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A graduate seminar to select the 5 most important papers pub lished in the first 50 years of the Journal of Range Management (J R M), 1948‐1997, cultivated an appreciation for the development of the discipline of rangeland science and management, and provided some historical perspective to judge the JRM. A review of textbooks, and papers describing early milestones and the use of citation counting were helpful in developing criteria to discriminate the importance of papers. The greatest disagreement among the 9 participants focused on the use of citation counts as a criterion: 2 students used only counts and 3 students refused to use counts. Eighteen papers received at least 1 vote as a top 5 paper, and 2 plant succession-vegetation monitoring papers were clearly the most popular. The exercise revealed that discontent with the JRM is not new. Although the JRM now covers a wider variety of topics, including both reductionist and synthetic works, some students felt that it was less encompassing of multi ple values of rangelands and the breadth of rangeland science than recent texts. The students found that the selection of impor tant papers expanded their understanding of the discipline and their resolve to publish in the JRM. Ideally, others will be chal lenged to perform this review for the benefit of students, the dis cipline, and the JRM.

Thespatialeomponent ofherbivory remainsenigmatic although it is a central aspect of domestic and native ungulate ecosystems. The effects of ungulate movement on plants have not been clearly established in either range or wildlife management. While livestock movement systems have been implemented to cope with increases in livestock density, restrictions on movement, and overgrazing, B large number of studies have disputed the effectiveness of different livestock movement patterns. Traditional pastoralism, particularly nomndism, has been perceived as irrational and even destructive, hut many studies have documented features of traditional pastoral land use that would promote sustainability. Disruptions of wild ungulate movements have been blamed for wildlife owrgrazing and population declines, but actual patterns and mechanisms of disrupted movement and population responses have been poorly documented. Models that integrate plant growth, ungulate movement, and foraging are suggested as a way to improve analyses of spatial plant-herbivore systems. Models must give due attention to nonforage constraints on herbivore distribution, such as topography. Models should assess the significnnee of movement 8s a mans Of coping with local climatic variation (patchy rainfall). Models that distribute an aggregate population over a landscape in relation to the distribution of habitat features deemphasize aspects of ungulate movements and population responses that inevitably cause nonideal distributions, particularly in natural ecosystems. Individual based models describe movement and foraging processes more accurately, hut these models are difficult to apply over large areas. Both top-down and bottom-up approaches to spatial herbiwry are needed. To model plant responses to movement, it is important to account for small scale phenomena such as tiller defoliation patterns, patch grazing, and grazing lawns as well as large scale patterns such as rotation and migration. Herbivory patterns at these difTerent scales are interrelated. Managers of wildlife and domestic livestock populations confront similar problems as they attempt to interpret ungulate spatial distribution patterns and their effects on plants. Overgrazing and subsequentecosystemdegradation onrangelandsorpastoralgrazing areas arc often attributed to inappropriate management of livestock spatial distributions. Overabundances of ungulates in wildlife preserves, and consequent overgrazing, arc often attributed to human interference with natural ungulate migrations or dispersal patterns. These management problems are analogous in that ungulate spatial utilization patterns determine how grazing impacts are distributed in space and in time. Ecosystem sustainability is affected by interactions among animal movement and abundance, plant growth, plant response to grazing, and the physical structure of the landscape. The consequences of herbivory for ecosystems depend, of course, upon herbivore abundance. However, herbivore abundance is expressed in terms of numbers of animals per unit of land, per unit of plant production, or per unit of land per unit time. These measures have been distinguished as stocking density, grazing pressure, and stocking rate, respectively (Heitschmidt and Taylor 1991). Until recently, research and management of ungulate herbivores have treated the denominators of these expressions as homogeneous. The aim of this paper is to explore heterogeneities in these denominators that are normally averaged out.

The range science profession has traditionally relied upon the concept of apical dominance to explain tiller initiation in perennial grasses. The physiological mechanism of apical dominance is assumed to follow the direct hypothesis of auxin action, which was originally proposed during the 1930's. This hypothesis indicates that the plant hormone auxin (IAA), produced in the apical meristem and young leaves, directly inhibits axillary bud growth. The direct hypothesis was, and continues to be, the sole interpretation of the physiological mechanism of apical dominance since the concept was initially adopted by the range science profession. However, the direct hypothesis was abandoned by plant physiologists during the 1950's because of experimental and interpretive inconsistencies and the demonstrated involvement of a second hormone, cytokinin, in apical dominance. The cytokinin deficiency hypothesis has replaced the direct hypothesis as the current hormonally based interpretation of apical dominance. This hypothesis indicates that IAA produced in the apical meristem blocks the synthesis or utilization of cytokinin within axillary buds inhibiting their growth. Despite wide acceptance, numerous issues remain unresolved concerning this hypothesis, suggesting that it may also be an incomplete interpretation of the physiological mechanism of apical dominance.

Inhibitory effects of metabolites from balsam poplar (Pops Unpublished data, P.B. Reichardt) and the relative amounts present in juvenile and mature plants and plant parts are being quantified. In addition, bioassays are being conducted to evaluate deterrent properties of different resin fractions isolated (Bryant and Kuropat 1980, Bryant 1981, Bryant et al. 1983, Unpublished data, P.B. Reichardt). Bryant and Kuropat (1980) speculated that current annual growth (CAG) twigs ofjuvenile Alaska paper birch are less digestible than CAG twigs from mature-growth-form plants due to their higher resin content, which may be toxic to rumen microbes. Previous studies have demonstrated antibacterial effects or inhibition of digestion by rumen microbes exposed to various terpenoids. Nagy et al. (1964) found that essential oils in sagebrush (Artemisia tridentata) inhibited bacterial growth and decreased gas and volatile fatty acid production in rumen of mule deer (Odocoileus hemionus). Oh et al. (1967) and Longhurst et al. (1968) found that oxygenated monoterpenes present in Douglas fir (Psuedotsuga menziesii) needles strongly inhibited Columbian black-tailed deer (0.h.’ columbianus) rumen microbial activity. Schwartz et al. (1980) reported that volatile oils present in various junipers (Juniperus spp.) reduced cellulose digestion in vitro by up to 40%. In this paper, we present evidence that benzyl alcohol, cineok papyrifcric acid, and a steam distillate fraction from juvenile Alaska paper birch depress in vitro fermentation of cellulose SUSpended in rumen fluid from wapiti (Cervus elaphus nelsoni). Material and Methods Four resin components, 2 each from balsam poplar and paper Authorsare research assistant, Department of Biological Sciences, MichiganTechnological University, Houghton 49931; research assistants, Department of Animal Sciences, University of Alberta, Edmonton T6G 2P5. The authors thank the following persons for their support and assistance with various aspects of this study: J. Bryant, P. Reichardt, R. Hudson, L. Jebson, D. Renecker, J. Aalhus, D. Summers, and T. Fenton. Financial support for this study was prowded by Michigan Technological University and the University of Alberta. Manuscript accepted October 15, 1984. 370 birch, were chosen for testing because of their ability to deter browsing by snowshoe hare (Lepus americanus) (Unpublished data, J.P. Bryant). Papyriferic acid, a triterpene carboxylic acid, and a steam distillate fraction, composed primarily of sesquiterpenes, from juvenile Alaska paper birch were provided by Dr. P.B. Reichardt (Department of Chemistry, University of Alaska, Fairbanks). Papyriferic acid was isolated from diethyl ether extract of CAG twigs from winterdormant juvenile plants by column chromatography. The steam distillable fraction of juvenile paper birch was isolated by diethyl ether extraction of the steam distillate (Personal communication, P. Reichardt). In addition, cineole (an isoprenoid) and benzyl alcohol, 2 compounds present in balsam poplar bud resin, were obtained commercially (Sigma Corp., St. Louis, MO.). Sample Preparation Concentrations of resin fractions used for in vitro trials were based on the amount of each resin component available and on the amount estimated to be present in CAG twigs from both mature and juvenile forms of paper birch and balsam poplar (Unpublished data, P.B. Reichardt). Because of the limited availability of papyriferic acid and paper birch steam distillate, treatment concentrations for these compounds were 5 and 20 mg per gram of substrate. Cineole and benzyl alcohol were tested at concentrations of 5, 10, 20,40, and 100 mg per gram of substrate. All treatment concentrations were prepared on a dry weight basis. Commercial purified cellulose (“Alpha floe”, Lee Chemicals Ltd., Toronto, Ont.) was used as a substrate. Resin components were dissolved in excess acetone, placed into a 150-ml round-bottom flask with the cellulose substrate, and swirled until the material was saturated. The flask was then placed on a vacuum rotodistiller with a water bath temperature of 50°C for approximately 10 minutes, or until the acetone had evaporated. The treated cellulose was removed from the flask, placed into metal dishes, and oven-dried at 4O“C for 48 hours. Following drying, samples were mixed in a micro mill and stored in sealed glass containers. In Vitro Techniques The in vitro techniques used to measure digestion of dry matter were developed by Tilley and Terry (1963) and modified by Morgantini and Hudson (in press). Rumen inoculum was obtained from a fistulated wapiti steer which was maintained on pelleted aspen concentrate, alfalfa hay, freshly cut browse, and fresh grass available ad libitum in a l-ha pasture. Triplicate samples were tested at each concentration level. Acetone controls were also tested for antimicrobial effects. Differences were tested by one-way analysis of variance and Duncan’s new multiple range test (KO.05).

Microwave ovens l ppe8r to be 8 vi8blc 8Item8tive to forced 8ir I8bor8tory ovens for obt8ining dry weights for vegetrtion samples. Two gr8ss species, Kentucky bluegr8ss (Pea pratensis) 8nd till fescue (Fatucu urundinaceu), were used to determine percent moisture lose by yeighbt at 3 weight lo8dings. The lo8dings were al 8pproxim8tely 50,100, urd 200 weights. For the 3 loadings, times rquired to obt8in a dried sample were at most 4.5,7.5, and 11.0 minutes, respectively. The time rquired for 8U sunples in the convention81 18b oven WM 72 hours.

This viewpoint paper examines criteria for preparing and evaluating manuscripts that involve stochastic approaches. Increasing use of stochastic mathematics to address inherent uncertainty in natural systems has meant increasing challenges to write and evaluate the manuscripts reporting such research. The paper provides a set of criteria directed at aiding authors, referees and associate editors in writing and evaluating this research. The paper asserts that for research papers to be acceptable to a management science journal such as the Journal of Range Management, they should at least be mathematically appropriate, functionally valid, pragmatically justified, technically comprehensible, and generally readable. It then examines the relationship of the concept of synthesis to the management implications sections of journal articles. The paper advocates increased attention to the concept of synthesis in making papers that report stochastic research in particular, and technical research in general, more understandable to readers, and more useful in range management science.

This paper analyzes the kinds of publications that are currently accepted by the Journal of Range Management, and in view of the evolving identity of range science, proposes a review of the those kinds of papers by the Editorial Board. The paper explores the kinds of papers that would help the Journal in identifying and developing range management science. It suggests a modified emphasis directed at increasing conceptual creativity, and developing explicit, integrative linkages and communications of range management science. In practice, this revision involves increased publication of synthesis papers, and increased emphasis of synthesis in the Journal's publications in general. Major benefits to the Journal would likely be increased diversity of published papers, broader professional diversity of authorship, increased readership, and increased effectiveness in serving and encouraging range management science.

The 3 papers which follow this prologue were originally presented at the Fifth International Symposium on Society and Resource Management, held 7-10 June 1994 at Colorado State University, Fort Collins. The symposium focused on creating partnerships among natural resource professionals in research, education, and management. Nearly 500 papers were presented by attendees representing a dozen countries. Most of them were social scientists and economists; relatively few range scientists or range managers were present. It is somewhat paradoxical that an international conference dealing with human dimensions issues of natural resource management should attract so little attention from those of us who have specialized in the stewardship of rangelands. While we all acknowledge the importance of how social issues are impacting rangeland management-particularly those on federal and state lands in the United States-many of us, like other natural resource professionals, tend to feel uncomfortable addressing societal concerns. Our lack of training in social sciences certainly inhibits us. Also, social problems are often perceived as being insolvable because of non-compromising interest groups. Whatever the reasons, me lag far behind several other natural resource professions in exploring interrelationships between the human and bio-physical dimensions of our discipline. The dilemma at the Fifth International Symposium was not one of a dearth of appropriate subjects being covered. Although the word “rangelands” did not appear in many papers, topics germane to rangelands were presented; e.g., papers on risk assessment, ecosystem management, and the changing resource management work force. Regardless, the human dimensions of rangelands will remain relatively unexplored without personal interactions between the kinds of people who tend to belong to the Society for Range Management, and the kinds of people-social scientists and economists--who attended the Fifth International Symposium. Partnerships cannot form without a mechanism for interaction. If the emerging concept of ecosystem management is to succeed as a national policy, opportunities for synthesizing the crucial components of social values and ecosystem health, as they relate to long-term sustainability and other ingrained goals, must be increased. The utilitarian conservation movement of the early 1900’s. based soley on rigorous science and professionalism, has been modified by the environmental

This paper analyzes the rangeland condition concept, and discusses how the search for a general concept has been part of the larger search for the identity of range science. It distinguishes between the concept and the assessment of rangeland condition, and distinguishes between the concept and ecological theories used in condition assessment. It proposes a general condition concept of modular character in which different ecological theories and field data are interchangeable components applied locally on appropriate, specific areas. It discusses past distinctions between range management and range science, implores the development of range management science, and discusses efforts needed in research, education, and administration to pursue its development. It interprets past and current events related to range science, including the advent of rangeland health, and discusses their relationships to range science's unfulfilled development as a management science. The paper encourages systematic design of concepts needed to allow range science to fulfill its philosophical potential as a management science.

Multi-variable analysis of grazing research has seen little conceptual development and even less application. To advance research on the multiple relationships of livestock grazing, computer-based analyses using multiple variables are needed. Dynamic variables describing livestock-herbage relationships must be developed to describe dynamic processes such as herbage growth and disappearance. Such variables could be used either alone or in combination with other variables as indicators to analyze and manage grazing. This paper presents 4 arrays of derived variables and discusses their individual and combinational value in analyzing and managing grazing. Greater power in analyzing grazing will come from use of combinations of variables rather than relying on single variables, e.g., stocking level. The variables described are useful in comprehensive analyses of research or in ad hoc roles aiding decisions in management. The paper also discusses possible future uses of variables as indicators in computerized analyses of other ecological systems.

Intact seeds (caryopses) of Indian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker] are generally reported to exhibit poor germination. The cultivar Nezpar was evaluated to determine if substrate matric potential and substrate physiochemical properties influence germination. Matric potentials ranged from 0 to -1.5 MPa. Substrate variables included: 2 kinds of germination paper, the A horizon of a dune sand, and a commercial washed silica sand. Seeds of Indian ricegrass had low germination (< 5%) with an oversaturated substrate. Germination increased significantly (P less than or equal to 0.05) between -0.005 and -0.10 MPa tension (30 to 70%), then decreased at more negative matric potentials. As compared with paper substrates, the dune sand showed significantly greater (P less than or equal to 0.05) germination at matric potentials more negative than -0.30 MPa. Standard germination screening procedures, especially at high water contents, do not adequately predict the maximum germination characteristics of Indian ricegrass; thus, substrate matric potential is a critical variable to control in germination tests. Moreover, physicochemical differences among common laboratory germination substrates may lead to significantly different termination responses. Microscopic examination of cross-sections of caryopses suggests the mechanism for reduced seed germination at saturated and oversaturated conditions may be the presence of a void between the lemma and palea which, when water-filled, retards oxygen diffusion to the embryo.

This paper addresses the issue of the effect of random errors in field estimates of net primary production (NPP). This is a critical subject in range management because field estimates of plant production are regularly used to determine stocking rates, range condition, and animal consumption. What we show in this paper is that random errors associated with field estimates of NPP can result in a positive bias and thus an overestimation of NPP. Depending on the case, this overestimation has been reported as high as 700%. We present examples with overestimations in the 200% to 400% range. The overestimation in NPP increases with increases in biomass variances, frequency of sampling, and number of taxonomic (species) and tissue (live, dead, etc) components sampled. We (1) outline in nonmathematical terms the reasons behind overestimation in NPP and the analytical solutions designed to correct them; and (2) present applications of the analytical solution for adjustments to concrete cases. The adjustments for overestimation outlined in this paper do not guarantee an accurate estimate of NPP but eliminate an unneeded source of error. A computer program (for IBM(TM) compatible) designed to implement the necessary adjustments is available from the authors free of charge (send a blank diskette).

Bighorn sheep and mule deer grazed bluebunch wheatgrass on areas on a Wyoming big sagebrush/bluebunch wheatgrass winter range significantly greater than adjacent unburned sites for 4 years after burning. Grass production decreased slightly the first year after burning but returned to preburn levels 2 years afterwards. Frequency of bluebunch wheatgrass in plots was reduced for 2 years following burning but returned to preburn levels by the third year. Big sagebrush seedlings were noted on burned sites 2 years after burning. Burning was considered to benefit bighorn more than mule deer because sagebrush, an important component of the mule deer diet, was effectively removed from the site for at least 4 years after burning. Many populations of bighorn sheep (Ovis canadensis) occur as small, isolated bands in the upper Salmon River area of Idaho. Restoration of bighorn sheep winter range is one aspect of increasing these populations to levels which ensure that local extinction will not occur, and hopefully to levels which will eventually provide regulated sport hunting. These populations occupy Wyoming big sagebrush (Artemisia tridentata wyomingensis)-bluebunch wheatgrass (Agropyron spicatum) rangelands that offer opportunities to enhance productivity through prescribed burning, which would hopefully favor the preferred grass forage and decrease the sagebrush. In addition, these winter ranges are used by mule deer (Odocoileus hemionus), which prefer sagebrush and other browse species (Lauer and Peek 1976). As the preferred deer forage species are reduced by buming, and bighorn forage species are favored, deer use may be reduced on these sites, which would lessen competition with bighorn. This paper describes responses of vegetation and ungulate use on seven small burns conducted in September 1974 on the East Fork Salmon River bighorn sheep winter range. Study Area and Methods The East Fork Salmon River winter range is located approximately 20 km south of the confluence of the East Fork with the main Salmon River in east-central Idaho. It is approximately 86 km2, with elevations ranging from 1,744-2,438 m. Soils are derived from Challis Volcanics, composed chiefly of andesite flows and flow breccias (Ross and Savage 1967). Mean annual temperature at Challis, Idaho, 34 km north, is 7?C, and annual precipitation averages 18 cm, Authors are professor and research associates, College of Forestry, Wildlife and Range Sciences, University of Idaho, Moscow. Lauer is now a wildlife biologist for the Bureau of Indian Affairs, Pendleton, Oregon. Authors thank Craig T. Kvale, Jeffrey J. Yeo for assistance in data collection. Loren Anderson and Jerry Christian, Bureau of Land Management, Salmon, Idaho, and Lanny 0. Wilson, Bureau of Land Management, Boise, organized and conducted the buming. This report was financed by McIntire-Stennis Project MS-22, the Forest Wildlife and Range Experiment Station, University of Idaho, Idaho Cooperative Wildlife Research Unit, William T. Wittinger and, the Bureau of Land Management. Paper No. 150, Forest, Wildlife, and Range Experiment Station, University of Idaho. Manuscript received September 5, 1978. much occurring as rain in May and June. Snowpack rarely exceeds 15 cm at lower elevations, but may exceed 61 cm at higher elevations. Precipitation at Challis, 34 km north of the study area, was lower than normal in spring (April, May, and June) but higher than normal in fall (September-October) from 1975-1977. Fall precipitation was 177% of normal in 1975, 219% in 1976, and 125% in 1977. Total precipitation from 1974-1977 ranged from 93-128% of normal. Seven areas ranging in size from 0.05 to 0.45 ha and totaling 1.51 ha were burned in September 1974, using hand-held propane torches and flares. Small patches of unburned vegetation within the fire perimeter were burned later. Unburned stubble less than 5 cm tall was present on most bluebunch wheatgrass plants after burning. Wyoming big sagebrush plants were completely burned, with a few stems burned to below-ground level. No fall regrowth occurred after the burning. Vegetation analysis consisted of evaluation of composition and vigor of bluebunch wheatgrass on each of the seven sites. Permanently marked 15;.2-m transects were established, and twenty 2 x 5-dm plots were located at 1.5-m intervals. Ground cover was determined by recording live vegetation, litter, and inorganic material at the four corner points of each plot. Frequency of occurrence of each species within the 20 plots was obtained. Production of grasses, forbs, and shrubs was obtained in July by clipping ten 2 x 5-dm plots on the burned and unburned sites. Grazed and ungrazed heights of vegetative growth of 100 burned and unburned bluebunch wheatgrass plants were measured in spring of each year. Percentage grazed of 100 randomly selected bluebunch wheatgrass plants was also obtained on burned and adjacent unburned sites. Analyses of variance and Duncan's multiple range tests to determine significant differences in means of observed parameters between years on burned and unburned sites were used to evaluate the data. Pearson correlation coefficients were used to determine relationships between precipitation and vegetation production. All information except utilization data were collected until no differences attributable to burning occurred or trends could be established.

Seed of Texas persimmon germinated in excess of 90% at constant temperatures from 20 to 300 C, and in an alternating temperature regime of 20-30? C. Seeds germinated equally well in light and dark. No seed dormancy mechanisms were observed, and viability was not reduced after storage at room conditions for 2 years. Germination percentages of seeds collected from 2 contrasting range sites did not differ. Germination did not differ over a broad range of pH values (4 to 11), but radicle elongation was inhibited at pH 11. Germination and radicle length were sensitive to osmotic potentials of 0.2 MPa or more, and no seed germinated at 1.2 MPa. Germination was restricted in a 5 g/l NaCI solution and nearly ceased at 10 g/l NaCl. Radicle length was more sensitive to NaCl solutions than was germination. Ion toxicity of salt solutions appeared to be more detrimental to germination and radicle growth than the osmotic potential of salt solutions. Seeds were not dependent on soil cover for seedling establishment, but the highest emergence occurred when seeds were covered with 1 cm of soil. Percent of germination was not reduced by passage through the digestive tracts of coyotes. Texas persimmon (Diospyros texana), also called "black" and "Mexican" persimmon is a native shrub or small tree found in rocky open woodlands, open slopes, arroyos, and other such places throughout the western two-thirds of Texas (Correll and Johnston 1970). Highest densities occur in a group of 13 counties in southcentral Texas from the southern edge of the Edwards Plateau into the northern South Texas Plains (Scifres 1975). It is usually 2 to 3 m tall, but may attain a height in excess of 6 m. Texas persimmon fruits are an important wildlife food (Vines 1960, Arnold and Drawe 1979), but this species is often a deterrent to effective range management. Although usually considered a minor component of range vegetation, Texas persimmon may become one of the primary problems following use of mechanical brush control methods such as chaining and root plowing (Scifres 1975, 1980). Moreover, it is a hard-to-kill species that is essentially resistant to conventional herbicides applied as broadcast sprays. Because its roots extend laterally a great distance from the parent plant, it is also resistant to most mechanical control methods (Scifres 1980). Little is known of the life history or biology of Texas persimmon. The major objective of this study was to determine the germination response of Texas persimmon seeds in the laboratory to certain environmental factors encountered in the seedbed. The effect on seed germination after passing through a coyote digestive tract was also studied. Materials and Methods Texas persimmon seeds were collected in August 1980 from several plant populations growing on a gray sandy loam range site (Aridic Ustochrepts) near La Joya in Hidalgo County, Texas. Only fully developed, undamaged seeds were used for germination experiments. Prior to use in experiments, seeds were stored at room conditions (20 to 270C, and 50 to 75% relative humidity). Author is range scientist, Agricultural Research Service, U.S. Department of Agriculture. This study is a contribution from Remote Sensing Research, Southern Region, Agricultural Research Service, USDA, Weslaco, Texas 78596. The author wishes to thank Mario Alaniz for his assistance in both the field and laboratory. Manuscript received February 14, 1983. With the exception of periodic determination of germination over a 2-year period, the various experiments were conducted when the seeds were less than I year old. All experiments were conducted in small growth chambers with automatic temperature and fluorescent light (200 MAE/m2/s) controls. Unless otherwise stated, experiments were conducted at a constant temperature of 25?C (optimum) with an 8-hr light period. An experimental unit was 10 seeds in a 15-cm petri dish that had 2 filter papers wetted with 20 ml of distilled water or an appropriate test solution. Experiments were designed as randomized complete blocks unless otherwise stated. Treatments were replicated 10 times, and each experiment was conducted twice. Seeds with 2-mm long radicles were considered as germinated. Germination was recorded 14 days after the initiation of each experiment. Radicle lengths were recorded in selected experiments. Seeds were germinated under continuous temperatures of 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, 35, and 40?C (8-hr light period, 16-hr darkness) and alternating temperatures of 10-20, 15-25, 20-30, and 25-35? C (16-hr low temperature in darkness, 8-hr high temperature with light) (Mayeux and Scifres 1978, Mayeux 1982, Everitt 1983a). The effects of simulated moisture stress on seed germination were evaluated by adding polyethylene glycol (PEG-6000) to distilled water for the substrata-PEG-6000 concentrations required to give osmotic potentials over a wide range of temperatures are given by Michel and Kaufman (1973). Their results were used to prepare solutions ranging from 0 to 1.2 MPa at 25?C (1 MPa = 10 bars). The pH of these PEG solutions was 6.7. Tolerance to salinity during germination was evaluated with aqueous solutions of NaCl at concentrations of 0, .25, .5, .75, 1,2.5, 5, and 10 g/l. The influence of substrate pH on germination was investigated by adjusting the pH of distilled water with HCI and KOH (Mayeux and Scifres 1978). Percent germination was evaluated at pH values of 2, 3, 4, 5, 6, 7, 8, 9, 11, and 12. Light requirements for seed germination was investigated by comparing germination in petri dishes covered with aluminum foil with germination in uncovered dishes. The effect of age on germination was investigated by comparing germination at 1, 6, 12, 15, 18, 21, and 24 months after seed collection. The influence of planting depth on seed germination was studied in the greenhouse. Temperatures in the greenhouse ranged from 21 to 28?C. Ten seeds were planted in soil in large pots (16 cm diameter X 16 cm height). A potting mixture of 3 parts sandy loam :1 part peat moss: 1 part perlite was used to prevent crusting. Seeds were placed on the soil surface and also covered to depths of 1, 2,4, 5, and 7 cm. Seedling emergence and height were recorded after 60 days. Seeds were also collected from several plant populations growing on a shallow sandy loam range site (Ustollic Paleorthids) in northern Hidalgo County in August 1980, and their germination was compared with that of plants from the gray loam site. During August 1979, seeds were recovered from fresh coyote feces from the gray sandy loam site near La Joya and their germination was compared with that of control groups of seeds from this same site. Seeds were taken from approximately 50 fecal samples. Three-hundred seeds from fecal samples and 300 control seeds JOURNAL OF RANGE MANAGEMENT 37(2), March 1984 189 This content downloaded from 157.55.39.17 on Fri, 02 Sep 2016 04:46:44 UTC All use subject to http://about.jstor.org/terms were placed in a growth chamber at 300 C. Each experimental unit consisted of 10 seeds in a 15-cm petri dish containing 2 filter papers wetted with 20 ml of distilled water. Treatments were replicated 10 times and each experiment was conducted 3 times. Percentage germination and emergence data were transformed (Arcsin) before statistical analyses. Data from 2 or 3 experiments were pooled prior to analyses. Data were subjected to analysis of variance and Student's t-test. An LSD was calculated in selected experiments (Steel and Torrie 1960). All statistical comparisons were made at P>0.05. Results and Discussion Germination of Texas persimmon seed appears to be restricted to a relatively narrow temperature range (Fig. 1). Germination was >93% at constant temperatures of 20-30? C, but decreased abruptly

Past analysis of the impacts of higher federal grazing fees on ranch vrlues have been purely speculative due to the absence of observations on sales of Western cattle ranches under a wide range of fee levels. An income approach to ranch value determination is described here in which numerous parameters affecting value can be varied. Solutions attained under different grazing fees are crpitaiized into the net present value of a potential ranch investment. Substantial decreases in ranch revenues and ranch values can occur with large fee increases in cases where public land forage comprises a large share of a ranch’s annual forage supply. Many factors affect the purchase price of a Western beef cattle ranch. The productivity of the ranch and the expected distribution of future cattle prices influence potential income. Estimates of the costs of production, including the federal grazing fee on public land-dependent ranches, are subtracted from gross revenues to provide an estimate of expected annual before-tax net revenues. Adjusting these estimates by expected inflation rates, changes in land and cattle asset values, applicable tax rates, and interest and opportunity costs of investment capital results in an estimate of the net present value of the ranch investment. Changes in the expected production, price, and cost relationships affect the present value calculations. The purpose of this paper is to explore how changes in one of the costs of production affect net present value. Specifically, how do changes in the fee charged for grazing cattle on public rangelands affect ranch values? Expected after-tax net present value is calculated as a random variable under different grazing fee levels with stochastic livestock prices. The influence of alternative federal grazing fee levels on the distribution of annual revenues and on ranch net present value is analyzed. The paper is organized into 5 sections. Following the introduction is a brief review of the literature addressing rural land valuation approaches, with specific reference to factors hypothesized to affect ranch land. The third section describes the model developed during this study to determine ranch values using the income approach to rural land valuation. The fourth section of the paper discusses the procedures developed to incorporate the stochastic nature of livestock prices into what are normally deterministic, nonrandom approaches to estimating ranch values. The empirical procedures employed and the results of changing parameter values on ranch values are discussed next. The paper concludes with a discussion of the results and the implications for those involved in the grazing fee debate.

Performance of Romney ewes and their lambs grazing an annual grass-subclover hill pasture was evaluated under both fivepaddock rotational and continuous grazing management treatments during 1977 and 1978. Live weight gains of ewes and lambs tended to be greater under rotational than under continuous grazing during the spring or fall green-feed periods. During the summer dry-feed period, however, sheep maintained thefr body weight better under continuous than under rotational grazing. These data support the hypothesis that rotational grazing most effectively improves animal performance during the green-feed period, perhaps through its reguhtion of pasture production. A common goal of rotational grazing systems is to increase forage production by controlling the frequency and intensity of pasture defoliation. Increased herbage production from rotational compared to continuous grazing management systems has been reported for perennial ryegrass (Ruane and Raftery 1964, Young and Newton 1975) and for perennial ryegrass-white clover (Trifolium repens) pastures (Marsh and Laidlaw 1978). This increase is thought to result from the maintenance of a more nearly optimum Leaf Area Index (LA1 = leaf area per unit ground area) than is achieved under continuous grazing (Smetham 1973). But as Young and Newton (1975) pointed out, increased forage production will result in superior animal production only if the additional forage available is consumed. Lambourne (1956) concluded that where feed supply was insufficient under continuous grazing, the extra feed produced under rotational grazing led to improved lamb growth. When feed supply was already adequate on continuously grazed pastures, the additional forage produced by rotational grazing became rank, causing a decline in forage quality. Lamb growth suffered. This same principle is well illustrated by the stocking rate X grazing management interaction discussed by Robinson and Simpson (1975). They noted that animal performance under rotational grazing only exceeded that of continuous grazing at intermediate to high stocking rates. When stocking rates were either very low or extremely high, rotational grazing tended to reduce animal performance. A second goal of rotational grazing is to improve the efficiency by which forage is harvested and converted to salable animal products. Continuous grazing allows livestock a considerable amount of dietary selectivity (Heady 1961). This selectivity, while allowing animals to choose a high quality diet (Weir and Tore11 1959), often results in overutilization of the most preferred plants allowing less preferred plants to become rank and of low quality (Sharrow and Krueger 1979, Smetham 1973). Undesirable shifts in species composition of the sward may follow as unpalatable species increase and as low growing plants such as clovers are shaded out (Smetham 1973). The high animal density for a short period of time employed by rotational grazing systems tends to increase grazing pressure, thus suppressing dietary selectivity by animals. This favors a more even utilization of all forage produced. The nonuse period immediately following grazing favors the growth of clovers and provides for production of high quality grass regrowth for grazing during the next rotational cycle (Smetham 1973). Since dietary selectivity may be suppressed under rotational grazing, it is important that ample high quality forage be present on each paddock if high animal performance is desired. Heady (1961) expressed concern about the implications of reduced dietary selectivity of livestock if rotational grazing systems were applied to the California annual grassland. He suggests that livestock production would suffer if animals were concentrated on small areas even for short periods of time due to reduced quantity and quality of forage available per animal. U Author is associate professor, Department of Rangeland Resources, Oregon State Although both continuous grazing and rotational grazing sysniversity, Corvallis 97331. terns are widely used in western Oregon, acomparison of these two Paper No. 6210. Oregon Agricultural This riport was submitted as Technical I E: rperiment Station, Corvallis. ~.nn.rrint rwx=ivrd lnnunrv IS 19X2. .._ .._ 1_..r. .__-..__ __..__., __. .._-. systems has not been made on annual grass-subclover pastures. The objective of this paper is to discuss the effects of rotational and JOURNAL OF RANGE MANAGEMENT 36(5), September 1983 593 continuous grazing on the performance of ewes and lambs grazing annual grass-subclover under heavy stocking rates. Table 1. Speeiaa composition (% of weight) and standing crop (kg//ha) of herbage present prior to stocking of pastures grazed continuously (C) and rotationally (R). Materials and Methods Information presented in this paper is taken from the final 2 years of a 6-year study. Animal performance data from the initial 4 years of the study were previously reported by Sharrow and Krueger ( 1979). 18 May 1977 I5 April V978 Research was conducted during 1977 and 1978 at the Soap Creek Ranch, approximately 20 km north of Corvallis, Ore. Elevation is approximately 100 m. The climate is maritime with cool, rainy winters and hot, dry summers. Mean annual precipitation is 103 cm. Species C R C R Vulpia myuros (rattail fescue) 62 61 48 52 Bromus mollis (softchess) 9 9 II 13 L&urn perenne (perennial ryegrass) 4 1 3 T Tk~olium subterraneum (subclover) 20 19 32 29 Misc. grass T 2 2 I

Relationships between overstory structure and understory current year production on 20 undisturbed sites of the grand fir/myrtle boxwood habitat type were studied in the Clearwater Mountains of northcentral Idaho. Overstory characteristics measured were tree canopy coverage, sum of the tree diameters, basal area, stand height, and stem density. Understory production was divided into four vegetation classes: (1)shrubs, (2) forbs, (3) graminoid and (4) total production. Regression models predicting current year production of each understory vegetation class were developed using all possible combinations of overstory parameters as independent variables. Canopy coverage and sum of the tree diameters were found to be the best indices of understory production. Canopy coverage was most significantly correlated with total understory production and shrub production. Canopy coverage and sum of the tree diameters were the most significantly correlated overstory parameters with forb production. Graminoid production was not significantly correlated to any of the measured overstory parameters. Basal area, tree density, and stand height were not statistically related to the understory production. Further examination of the models is needed to validate these relationships over the range of the grand fir/myrtle boxwood habitat type. The models are not applicable to areas where recent disturbance such as logging, fire, or disease has affected overstory structure. In forest stands, understory shrub and herb production available to herbivores is highly dependent on the structure of the tree overstory. Several studies have been conducted which relate understory production to overstory structure in forest stands and have proposed models to predict understory production based on tree stand characteristics such as basal area (Clary and Ffolliott 1966, Gaines et al. 1954, Halls and Shuster 1965, McConnell and Smith 1965) and canopy cover (Anderson et al. 1969; Cooper 1960; Ehrenreich and Crosby 1960; Halls and Shuster 1965; Jameson 1967; McConnell and Smith 1965, 1970; Young et al. 1967). The majority of the published accounts of overstory structureunderstory production relationships are for forests in the south, southwest, or midwest United States. Little work has been done relating overstory structure to understory production in the Pacific Northwest. The objective of this was to determine relationships between overstory structure and understory current year production on undisturbed sites of the grand fir/ myrtle boxwood (Abies grandis/ Pachistima myrsinites) habitat type in the Clearwater Mountains of northcentral Idaho. Authors are graduate research assistant and associate professor and range scientist Department of Forestry and Range Management, Washington State University, Pullman 99164. D. Pyke is now agricultural research technician, Department of Botany, Washington State University. This paper is Scientific Paper SP 5837 of the College of Agriculture Research Center, Washington State University. Work was conducted under Project 0290. The research herein was financed in part by a grant from the U SDA expanded Douglas-fir Tussock Moth Research and Development Program. Manuscript received February 2, 1981. Study Area and Methods The study area was located in the Clearwater Ranger District, Nezperce National Forest, northcentral Idaho. Twenty study sites were selected to obtain a range overstory canopy coverage, basal area, stand height and stand density. All sites were of the grand fir/ myrtle boxwood habitat type as described by Daubenmire and Daubenmire (1968). Overstories varied in maximum age breast height from 65 to 192 years. Site elevations range from 1 120-1620 m with aspects representing all cardinal directions and slopes ranging from 0-54%. Vegetation measurements were made within a 375-m2 circular macroplot established on each site. Overstory canopy coverage was measured using a spherical densiometer leveled at I m above the ground at the center of the macroplots (Lemmon 1956). The densiometer employs a highly polished, convex, chrome mirror to reflect a large overhead area. Diameter at breast height was measured for all conifer trees over 1.4 m and used to calculate basal area in m2 / ha and sum of tree diameters in m / ha. Average height in meters of the combined dominant and codominant crown classes was determined with a clinometer. All trees greater than 1.4 m high were counted and stem density expressed as number of trees per hectare. The understory vegetation was divided into four above-ground vegetation classes: (1) shrub, (2) forb, (3) graminoid, and (4) total production. Current year growth of these vegetation classes was sampled between August 9 and 17, 1976, the period of near maximum above-ground production for the year. The circular macroplot was bisected perpendicular to the contour of the slope and five, 0.45 m2 production microplots were systematically located in each half. One microplot in each half of the macroplot was randomly selected for harvesting. The vegetation production of each class in the remaining 4 microplots was estimated as a percentage of the production of their counter-part class in the microplot to be harvested (Mueggler 1976). All herbaceous vegetation in the harvest microplot was then clipped to the upper surface of the litter layer and separated into their respective vegetation classes. Current year growth of shrubs in the harvest microplot was clipped at the previous spring's bud scar. No vegetation above 3 m from the ground was included in the sample. The clippings were air-dried for 3 days, oven-dried for 12 hours at 60?C, and weighed. Estimation error was assessed by clipping all 10 microplots at 3 of the study sites after estimating production as described above. A regression equation relating estimates to actual production was derived to correct for estimation error prior to calculating the production for each macroplot. Canopy coverage and rooted frequency data were collected on each site to characterize species composition of the understory. Forty 2 X 5 dm microplots were systematically placed along two 20 m transects passing through the center of the macroplot, one parallel and one perpendicular to the contour of the slope (Daubenmire 1959). The production and overstory data were plotted and inspected to ascertain appropriate regression models. Relationships between JOURNAL OF RANGE MANAGEMENT 35(6), November 1982 769 This content downloaded from 207.46.13.149 on Wed, 19 Oct 2016 03:59:54 UTC All use subject to http://about.jstor.org/terms overstory structure (independent variables), and understory production (dependent variables) were analyzed using the general linear model (GLM procedure), stepwise regression maximum R2 improvement (STEPWISE procedure), and all possible regressions (RSQUARE procedure) of the Statistical Analysis System (SAS) (Helwig and Council 1979). Two general linear models were considered appropriate and tested for significance

Honey mesquite kill and suppression, vegetation response, and changes in grazing use and capacity were evaluated following brush control in north-central Texas. Tree grubbing was most effective for eliminating honey mesquite, but because of soil and plant damage the treatment did not increase grazing capacity or improve range condition compared to nontreated rangeland. Aerial application of 2,4,5-T + picloram was more effective in killing and defoliating honey mesquite than 2,4,5-T alone, but both treatments significantly increased forage production. The 2,4,5-T + picloram and 2,4,5-T sprays provided a 7 to 16% increase in grazing capacity over a 4-year period on light and heavy honey mesquite infested pastures, respectively. Nearly 6 million hectares in the Rolling Plains of Texas are infested with woody plants of low forage value (Smith and Rechenthin 1969). Honey mesquite (Prosopis glandulosa Torr. var. glandulosa)l is the most abundant woody invader having increased in density over the past century with drought, overgrazing, and the cessation of natural fires (Fisher 1948, Bogoush 1951, Rechenthin and Smith 1967). Chemical and mechanical control of honey mesquite has been used extensively throughout the Rolling Plains with the objective of reducing the size and number of plants and to promote secondary succession (Fisher 1977, Scifres 1980). Thirty years of experience have shown that total eradication of honey mesquite is neither practical nor feasible. Several methods for controlling honey mesquite have been developed, however, and are widely used to maintain and increase forage production. Foliar applications of herbicides, such as 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), and 2,4,5-T plus 4-amino-3,5,6 trichloropicolinic acid (picloram), usually "root-kill" only 25 to 40% of the honey mesquite plants (Fisher et al. 1972). Plants not killed by the herbicides develop new stems from previously defoliated branches or from the root crown (Younget al. 1948, Scifres etal. 1974). Prolific sprouting from the root crown can result in a multi-stemmed, shrubby growth requiring retreatment in 4 to 7 years (Scifres and Hoffman 1974). Grass response following spraying is most significant under the honey mesquite canopy and over a period of years expands into interspace areas between the plants (Brock et al. 1979). Tree grubbing with a low energy crawler tractor equipped with a sharp, U-shaped blade attached to the front can eliminate over 90% of the honey mesquite by cutting roots 15 to 30 cm below the soil surface (McDaniel et al. 1978). Grasses growing beneath the canopy are often uprooted with the grubbed honey mesquite leaving a pit of bare exposed soil. Grubbing honey mesquite usually induces a lower seral stage of succession because of the disturbance of soil under the canopy area. The authors are assistant professor, Range Improvement Task Force, Department of Animal and Range Sciences, New Mexico State University, Las Cruces; assistant professor, Division of Agriculture, Arizona State University, Tempe; and principal application scientist-range science, EROS Data Center, Sioux Falls, South Dakota. The paper is published with approval of the Director, Texas Agr. Sta., as TA16819. Research reported in this paper was funded in part by a grant from the E. Paul and Helen Buck Waggoner Foundation, Inc. Manuscript received March 10, 1981. 'Scientific names follow Gould, F.W. 1975. Spraying honey mesquite is expected to give maximum increases in grazing capacity the first 3 years, whereas mechanical control may not yield a return until after 3 or 4 years (Workman et al. 1965, Dahl et al. 1978, Wiedeman et al. 1977). Following interviews with range trained personnel, Whitson and Scifres (1980) reported an annual rate of return from aerial applications of 2,4,5-T on honey mesquite in the Rolling Plains to be from 12.7 to 16.9% over a 20-year planning horizon. Five to 9 years are required to recover the initial investment of aerial application of 2,4,5-T on deep soils, and 12 to 13 years are required on shallow soils. Tree dozed or grubbed areas seeded to a native mixture of adapted species require nearly three times the number of years to yield a return on the original investment compared to spraying 2,4,5-T. The choice of which method to use for honey mesquite control is more complex than the treatment's ability to kill the plant or yield the greatest economic return. Environmental and management variables enter into the decision-making process making the choice of no single specific practice uniformly superior for every situation (Whitson and Scifres 1980). A brush control method which provides a favorable vegetation response and which allows an increase in red meat production is likely to be the preferred practice. The objective of this research was to evaluate changes in vegetation and grazing capacity following several different brush control techniques on light and heavy infested honey mesquite rangeland.

Accessions A-68, L-11, L-19, L-28, and L-38 of Lehmann lovegrass (Eragrostis lehmanniana Nees); P-15608 Cochise lovegrass (E. lehmanniana Nees X E. trichophora Coss & Dur.); A-84 and Catalina boer lovegrass (E. curvula var. conferta Nees); Palar Wilman lovegrass (E. superba Peyr.) and P-15630 blue panicgrass (Panicum antidotale Retz.) were seeded at a study site near San Simon, Ariz., in spring 1970 and 1971. Seedbeds were prepared by root plowing and furrow pitting immediately before planting. Growing season precipitation was 136 mm in 1970 and 218 mm in 1971. Mean accession densities in the fall after the initial growing seasons were 18 plants/M2 for both the 1970 and the 1971 plantings. Between fall 1971 and 1972 mean accession densities declined 44% and forage production was unchanged on the 1970 plantings. Accession densities declined 22% and forage production increased 250% on the 1971 plantings. Between fall 1972 and 1982 the majority of seeded plants died and forage production declined 90% on the 1970 plantings. Accession densities declined 78% and forage production declined 84% on the 1971 plantings. Southeastern Arizona and southwestern New Mexico rangelands were overutilized and deteriorated rapidly between 1880 and 1900. Griffith (1901) documented the deterioration and corresponding livestock losses. Cooperative studies to restore these rangelands were initiated in the early 1900's by the Division of Agrostology (USDA) and State Experiment Stations at Tucson, Ariz., and Las Cruces, N. Mex. Blount (1892), Griffith (1907), Keefer (1899), and Thornber (1905) seeded native and introduced grasses on irrigated and rangeland sites and evaluated emergence and survival. Teff [Eragrostis abyssinica (Jacq.) Link.] emerged on irrigated and nonirrigated sites, but long-term survival occurred only at irrigated sites. Native grass either failed to emerge or to survive at southwestern revegetation sites between 1910 and 1934 (Barnes et al. 1958, Cassady 1938, Glendening 1937, and Hendricks 1936). Numerous grass, forbs, and shrub species were introduced after 1930 (Cox et al. 1982). These introduced species were screened for germination, drouth tolerance, and seed production potential at Soil Conservation Service Plant Materials Centers, and a few promising grasses were released for rangeland plantings. Among these were A-68 Lehmann lovegrass and A-84 boer lovegrass; both were introductions from southern Africa. Lovegrass species and newly developed accessions were sown in summer (Bridges 1941 and Herbel et al. 1973) and fall (Bridges 1941) at desert sites in southern New Mexico. A-68 Lehmann and A-84 boer lovegrasses emerged in moist summers, and A-68 emerged in wet winters at lower elevations. Jordan (1970) conducted studies for 9 years to determine the best combinations of mechanical brush control, seedbed preparation, The authors are range scientist, USDA, Agr. Res. Serv., Arid Land Ecosystems Improvement, 2000 East Allen Road, Tucson, Ariz. 85719; and professor, range management, School of Renewable Natural Resources, University of Arizona, Tucson 85719. This paper is published with approval of the Director, University of Arizona College of Agriculture, Agricultural Experiment Station, as Paper No. 3705. The paper reports on work supported by the U.S. Department of the Interior, Bureau of Land Management, and is a cooperative investigation of Agr. Res. Serv., USDA, and the Arizona Agr. Exp. Sta., University of Arizona. Manuscript received January 20, 1983. and time of seeding for emergence and survival of forage grasses at 3 sites in southeastern Arizona. A-68 Lehmann lovegrass emergence and survival was optimized when root plowing and pitting were used to control brush and prepare the seedbed in spring, and when seed were sown immediately after a mechanical treatment. Comparative seedling trials were conducted to select adapted lovegrass and blue panicgrass accessions at a study site near San Simon, Ariz., in 1970 and 1971. The purpose of this paper is to quantitatively document and compare initial and long-term plant densities and forage production for these seeding trials. Study Site and Methods The study site is located 25 km southwest of San Simon, Ariz., near the Arizona-New Mexico State Line in southeastern Arizona. Average annual precipitation is 280 mm, and 30 to 40% occurs in winter. Winter months (November to March) are cold, dry, and windy, and typical of the Chihuahuan Desert (Mabry et al. 1977). Winter precipitation is either evaporated or transpired by shrubs, and apparently not used by seeded grasses (Jordan 1970). Effective summer precipitation falls in late July through October and varied from 98 to 230 mm at San Simon between 1972 and 1982 (National Oceanic and Atmospheric Administration, Annual Climatological Data Summaries 1972-1982). Mean summer precipitation was 165 mm over the 10 years. Figure 1 shows the departure of annual summer precipitation from the 10-year average. Average annual air temperature is 17?C and the frost-free period is 220 days. Soils are deep, well drained, and formed in old alluvium from mixed sources. Soils are classified as Eba gravelly sandy loam, mixed, thermic Typic Haplargids (Vogt 1980). Native perennial grass forage production was 2.5 to 5.0 g/ m2 on

Highlight: This paper describes a "now" capability whereby satellite imagery could provide range managers with maps and tables giving standing crop biomass for selected species groups or range types (swales, uplands, etc.). This capability is provided by a remote rangeland analysis system which can monitor the effects of weather, grazing intensity, and land-management actions on primary production. The system concepts resulted from a project designed to assess the usefulness of ERTS and other remote sensing systems as sources of information for rangeland management. A field measurement program supported and verified the successful use of ERTS imagery for computer classification of vegetation type and quantity of standing crop biomass. Biomass classification was accomplished on three successive ER TS images, withou t changing the classification parameters, indicating that biomass classification may be less critical than expected. Extensive statistical analysis of ERTS data has shown that the MSS (multispectral scanner) Channel 5 and the ratio of Channel 7 to Channel S provide the most significant variables for vegetation type and biomass classifications. Cross-classification results of vegetation type and biomass provide tables summarizing biomass availability by species groups and in total acres. Frequent monitoring of range and crop conditions is a prerequisite to effective management and planning decisions. Remote sensing can help improve such decisions by providing efficient monitoring of the quantity of standing crop biomass. This paper reports on initial efforts to develop a system to provide useful information for rangeland managers on a timely and economic basis. The remote rangeland analysis system (RRAS) described in this paper will be of benefit to government agenicies cliarged with management of public lands and to ranch managers. Application to the grasslands of the entire world may be possible. A conceptual description of the

The effects of clipping to a 2.54 cm (1 inch) height at 5 stages of development of western North Dakota mixed prairie were investigated. Soil moisture content at the beginning of the growing season had a greater effect on yields than did the clipping treatments. Observations from this two-year study indicate that soil moisture removal was not affected by the clipping treatments. Clipping significantly affected peak yields by needle-and-threadgrass (Stipa comata) and the Carex species during 1977; and the miscellaneous grasses (Agropyron smithii and Agropyron subsecundum) during 1978, at the sandy loam site. No significant differences in yields were observed for the other species and groups at the sandy loam site, or, the species and groups at the loam site for the two-yearperiod. Late season livestock gains in western North Dakota may be improved if the amount of blue grama (Bouteloua gracilis), the dominant palatable warm-season shortgrass, could be increased without decreasing the overall productivity of the range. Whitman (1953) reported that normal grazing usage results in a cover which is probably of greater grazing value than the completely protected cover. Employing a deferred and rotation system, Sarvis (1923) reported greater total gains on fewer acres when compared to a continuous grazing system. Under the deferred and rotation system, the vegetation was allowed to mature periodically before being subjected to grazing again. A new system of ranching, referred to as the Short Duration Grazing or SDG system, was developed in Rhodesia in 1964 (Goodloe 1969). This system consists of a high intensity-low frequency harvesting of the forage, even with intensive harvesting range conditions improved under the semiarid climate where the SDG system was developed. The present study was designed to determine the effect of intensive harvesting on the developmental stages of Northern Great Plains mixed prairie. Clipping results in more severe injury to grass stands than does defoliation from normal grazing use (Whitman et al. 1961). Although clipping does not directly duplicate the effects of grazing, considerable information may be gained by the reactions of species to foliage removal (Sarvis 1923). The effects of clipping on the Northern Great Plains have been reported by different authors. In South Dakota, Black et al. ( 1937) reported that frequency of clipping buffalo grass (Buchloe dactyloides) and blue grama appeared to have little effect on yield. Total production of buffalo grass, blue grama, western wheatgrass (Agropyron smithii), plains bluegrass (Poa arida), and six weeks fescue (Festuca octoflora) was greatest when clipped at 40-day intervals. Total production by all plants was also greatest when clipped at 40-day intervals. Two vegetation types in western North At the time of the research, authors were graduate student and chairman, Botany Department, North Dakota State University, Fargo, 58105. Holderman's present address is Ozark Francis National Forests, P.O. Box 1008, Russellville, Arkansas 72801. This report is a contribution of North Dakota Agricultural Experiment Station. Published with approval of the Director as Journal Paper No. 1091. Manuscript received October 19, 1979. Dakota, a western wheatgrass-blue grama type, and a needle-andthreadgrass (Stipa comata)-blue grama-sedge (Carex spp.) type were studied by Whitman and Helgeson (1946). Average yields for blue grama decreased in both vegetation types when clipped twice during a season to a height of 1.27 cm (1/2 in). Needle-andthreadgrass decreased under all clipping treatments in height, yield, and basal area. Average yields for western wheatgrass were maintained under single clipping to a height of 3.81 cm (1 1/2 in) and 7.62 cm (3 in), but decreased under double clipping. Sarvis (1923) reported blue grama was benefited by frequent clipping while needle-and-threadgrass decreased in relation to clipping frequency. Heinrichs and Clark (1961) in Saskatchewan, and Whitman et al. (1961) at Dickinson, North Dakota, reported that yields of green needlegrass (Stipa viridula) increased when clipped 2 or 3 times a year compared to annual clipping. These studies applied periodic and/or annual clipping treatments. The present paper reports the response of Northern Great Plains mixed prairie to intensive clipping at five stages of development, with respect to peak yields and basal cover of selected species and groups, and the seasonal removal of soil moisture in the profile. Description of Study Locations This study was carried out on two major range sites in western North Dakota. Vegetation of the region is mixed grass prairie as described by Weaver and Clements (1938). Study site I is located approximately 9.6 km (6 miles) northwest of the city of Dickinson on a sandy loam of the Vebar-Parshall-Arnegard toposequence (Larson et al. 1968). Dominant perennial grasses are needle-andthreadgrass, green needlegrass, blue grama, prairie Junegrass (Koeleria cristata), and Sandberg bluegrass (Poa secunda). The miscellaneous grasses are dominated by western wheatgrass and bearded wheatgrass (Agropyron subsecundum). Major Carex species are C. filifolia, C. eleocharis, and C. heliophila. Study site 2 is located approximately 14.4 km (9 miles) southeast of the town of Medora on a loam soil similar to the Shambo series (U.S. Dep. Agr. Forest Serv. 1971; and personal communication with Ken Thompson, Soil Conserv. Serv., Dickinson, N.D.). Dominant perennial grasses are western wheatgrass, blue grama, prairie Junegrass, and needle-and-threadgrass. The miscellaneous grasses are dominated by green needlegrass (Stipa viridula) and Sandberg bluegrass (Poa secunda). Major Carex species are C.filifolia, C. eleocharis, and C. heliophila. Scientific and common names follow Stevens (1963). Abbreviated scientific names follow the Range Analysis Handbook U.S.F.S. (1977). The climate of the region is semiarid with an annual precipitation between 40.13 cm (15.80 inches) and 42.06 cm (16.56 in), 75% of which falls during the growing season April through September. Experimental Procedures The experimental plots were randomly located with three repli188 JOURNAL OF RANGE MANAGEMENT 34(3), May 1981 This content downloaded from 157.55.39.55 on Sun, 12 Jun 2016 05:40:36 UTC All use subject to http://about.jstor.org/terms cates of eight treatments on each of two study sites. Plot size was 10.1 m by 11.9 m (33 ft by 39 ft) with four rows of six plots. Plots were subdivided into six 3.96 m by 5.03 m (13 ft by 16.5 ft) subplots, half of which were randomly selected to be sampled for above ground biomass in alternating years. Six-foot alley ways were left between plots to facilitate movement. Five of the treatments were clipping trials, two were herbicide trials, and one the control which received no treatment. This paper reports only the results of the

Several selective and nonselective foliar-active herbicides were applied alone and in 1:l combinations as broadcast sprays in the spring for control of Drummond’s goldenweed on the Coastal Prairie of Texas. Picloram at 0.56 kg/ha or picloram plus 2,4,5-T, glyphosate, or atrazine plus paraquat at 1.12 kg/ha consistently controlled the weed. Atrazine and 2,4-D, applied singly or in combination at 1.12 to 2.24 kg/ha total herbicide, effectively controlled Drummond’s goldenweed only when soil-water content was high. Dicamba, like 2,4-D, was effective when applied in a “wet” year but not in a “dry” year. The effective herbicides controlled Drummond’s goldenweed for at least 3 years. Although Drummond’s goldenweed is morphologically similar to common goldenweed, it is apparently more susceptible to herbicides than its western counterpart. Drummond’s goldenweed [Isocoma drummondii (T. & G.) Greene] has traditionally been considered a minor component of vegetation of the southern Gulf Prairies and Marshes of Texas. However, during the past decade, it has become increasingly important and is now a significant weed problem on about 1 million ha of rangeland south and west of Corpus Christi. It also occurs as isolated stands in the eastern South Texas Plains, where a closely related species, common goldenweed [Isocoma coronopzyolia (Gray) Greene] has become a serious, widespread range management problem (Mayeux et al. 1979). Drummond’s goldenweed normally occurs as scattered individuals in the understory of woody plant communities on rangelands. However, upon removal of the brush cover, especially by mechanical methods which disturb the soil, goldenweed may develop dense stands and dominate range sites of moderate to high potential productivity (Mayeux and Scifres 1979). Drummond’s goldenweed is a heavily branched, suffrutescent subshrub with a rounded canopy which is usually 5 to 8 dm tall but may attain a height of 1 m. The leaves are linear and entire or occasionally with small marginal teeth, several centimeters long, and resinous. The flower heads are formed in late fall, are composed of 10 to 30 bright yellow disc florets only, and occur singly or in clusters of as many as 20 at the stem tips. The flowers produce pubescent achenes, 2 to 3 mm long, with a persistent pappus two to three times as long as the achene. A single plant may produce more than 200,000 achenes and new seedling density can exceed 2,600/ m2 (Mayeux and Scifres 1979). However, annual seedling mortality may range from 25 to lOO%, depending on site and rainfall during the year of emergence. Stem elongation rates of mature plants average 0.5 to 0.8 mm/day but may proceed at nearly 2 mm/day following rainfall during the growing season on Authors arc range scientist, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Temple, Texas 76501, and professor, Department of Range Science, Texas A&M University, College Station 77843. The paper was approved by the Director, Texas Agricultural Experiment Station, as TA 15267. A part of the study was conducted while Mayeux was a graduate research assistant, Texas Agricultural Experiment Station, College Station 77843. The authors express their appreciation to Mr. Vernie Hubert of Vattman for providing the study area and to Julia Scifres for typing the manuscript. This paper reports the results of research only. Mention of a pest.icide in this paper does not constitute a recommendation by the USDA nor does It Imply registration under FIFRA. Manuscript received July 5, 1979. 98 well-drained sites which are not characterized by accumulations of salts and sodium. Since grazing of native grasslands provides the basis of the local economy of the area of Drummond’s goldenweed’s maximum adaptation, its spread, thickening of existing stands, and dominance of many sites following brush control have stimulated interest in its control. However, little information is available concerning the response of either Drummond’s or common goldenweed to conventional range weed control method. The problem is accentuated by confusion of Drummond’s goldenweed with common goldenweed or with “false broomweed” (Ericameriu austrotexana M.C. Johnston), formerly classified as Isocomapalmeri (Gray) Shinners and a common component of the south Texas perennial range weed complex. Mechanical methods which do not cause extensive soil disturbance, such as shredding, are not effective because Drummond’s goldenweed rapidly resprouts from lower stems and a woody caudex following top removal. Essentially no information exists concerning the response of Drummond’s goldenweed to herbicides. Common goldenweed, which occurs west of the geographical distributions of Drummond’s goldenweed, was controlled with 2,4-D [(2,4-dichlorophenoxy)acetic acid], picloram (4-amino3,5,6-trichloropicolinic acid), or a 1:l combination of picloram and 2,4,5-T[(2,4,5-trichlorophenoxy) acetic acid] applied as broadcast sprays in spring or fall if soil water content was adequate for rapid vegetative growth (Mayeux et al., 1979). Since control of common goldenweed with broadcast sprays depended on relatively high amounts of rainfall being received before treatment, responses among locations were erratic and relatively high herbicide rates were required for consistent control. However, forage species responded to goldenweed control with oven-dry standing crop increasing 5 to 10 kg/ ha for each 1% reduction in common goldenweed foliar cover. The objective of this study was to evaluate several herbicides and herbicide combinations for Drummond’s goldenweed control. Herbicides other than the phenoxy and related compounds commonly used on rangelands were included because highly susceptible agronomic crops such as cotton (Gossypium hirsutum L.) and vegetables are often grown on areas adjacent to rangeland infested with Drummond’s goldenweed. Glyphosate [N(phosphonomethyl)glycine] has proven effective for control of several species of perennial weeds on pastures (Johnson 1976) and railroad rights-of-way (Andrews et al. 1974). Glyphosate has also been used successfully for control of perennial range weeds such as Carolina horsenettle (Solanum carolinense L.) (Banks and Santelmann 1976) and African rue (Peganum harm& L.) (Allen and McCully 1976). Atrazine [2-chloro-4-(ethylamino)-6(isopropylamino)-s-triazine] is used on western rangelands to control weedy grasses and herbaceous broadleaf species (Houston and van der Sluijs 1973) especially in conjunction with grass seedings (Eckert et al. 1974). It also effectively controls silverleaf nightshade (Solunum eleugnifokum Cav.) (Johnson et al. 1976) and Canada thistle [Cirsium arvense (L.) Stop.] (Carson and Bandeen 1975, Parochetti 1974), and partially controls green rabbitbrush [Chrysothamnus viscidiflorus (Hook) Nutt.] when applied at 1 kg/ha JOURNAL OF RANGE MANAGEMENT 34(2), March 1981 (Evans and Young 1972). The contact herbicide paraquat (1,1’dimethyl-4,4’-bipyridinium ion) was evaluated because of its effectiveness against phenoxy-resistant range weeds such as geyer larkspur (Delphinium geyeri Green) (Hyder 1972). Table 1. Environmental conditiom daring herbicide applicationa to Drammondb goldenneed on June 4.1975, and May 26,1976, near Kingsville, Texas.

Bitterbrush plants were burned or clipped to 5 cm, during fall and spring, under different soil moisture conditions on 2 sites in eastern Oregon. Treated plants on the Juniperus/ArtenrisiarisiaPurshia site had an erect growth form while those on the Pinus/Purdtia site were a loq-growing, decumbent form. Sprouting after treatment was similar for the 2 sites and associated forms. Burning resulted in greater mortality than clipping. Spring treatments had less mortality compared to fall treatments. Artificially watering plants did not result in a substantial reduction in mortality. Over-winter mortality of sprouts reduced the number of bitterbrush plants alive in the second growing season. A publication summarizing recent literature on bitterbrush (Purshia tridentata) revealed that only about 10% of the citations alluded to bitterbrush response to fire (Clark and Britton 1979). The literature indicated that bitterbrush is a desirable shrub but may not be compatible with currently popular use of fire as a vegetation management tool. Response of bitterbrush to burning has been variable. In eastern Idaho it sprouted frequently but inversely with burn intensity (Blaisdell 1950, 1953). In central Oregon, Driscoll(l963) suggested that sprouting was related more to surface soil texture than burn intensity. Sprouting after wildfires was also variable in California. For example, in 5 of I3 wildfires at least 5% sprouting occurred, with a maximum of 25% (Nord 1965). In northern and central Utah limited sprouting occurred after wildfires (Blaisdell and Mueggler 1956). Daubenmire (1970) noted that bitterbrush was nearly always killed by wildfires in the steppes of Washington. Hormay (1943) stated that vast areas of bitterbrush have been destroyed by fire, and Billings (1952) contended that bitterbrush in the western Great Basin was permanently eradicated by fire. Mechanical top removal appears less damaging to bitterbrush than burning. Ferguson (1972) recommended removing 33% and 50% of the canopy to stimulate growth. Mueggler and Blaisdell (1958) reported that rotobeating and railing was less damaging than burning. Blaisdell and Mueggler (1956) burned or severed bitterbrush plants 5 cm above ground level monthly, May through October. They found 50% and 72%, respectively, of burned and severed plants sprouted, with spring treatments the least damaging. Some plants did not sprout until I3 months after treatment. Since bitterbrush at different locations may exhibit variable genetic traits, isolating specific factors which control sprouting is difficult. However, certain environmental parameters have been implicated in sprouting. This study was conducted to evaluate some environmental parameters which may be responsible for the variation in bitterbrush response to burning and clipping. Study Areas and Methods Two areas representing different plant communities were selected for study. Site I was located 30 km northwest of Burns, Ore., at 1,555 m elevation. Characteristic vegetation is the Juniperus/Artemisia-Purshia association (Fig. I) described by Driscoll(1964). Bitterbrush growing on this site does not layer and is similar to the columnar forms described by Alderfer (1977). Soils are Lithic Zerollic Paleargids over silica and limestone coated fractured bedrock (Lindsay et al. 1969). Site II was located 42 km north of Riley, Ore., at 1,585 m elevation. Characteristic vegetation on Site II is similar to the Pinusponderosa/Purshia tridentata (Fig. 2) association described by Daubenmire and Daubenmire (1968). Bitterbrush on this site is a low growing, decumbent form that infrequently layers. Soils are Lithic Argixerolls overlying rhyolite (U.S. Forest Service 1977). Soil texture on both sites is similar (Clark 1979). Both soils are shallow, averaging about 36 cm to bedrock. Both sites were located with the High Lava Plainsphysiographic province described by Franklin and Dyrness (1973) on the western fringe of the Great Basin. Average annual precipitation on both sites is similar, about 30 cm. Most of the precipitation occurs as snow during the winter months. During the study period snow persisted about 2 weeks longer on site II than on site 1 due to the canopy of ponderosa pine. Bitterbrush phenological development correspondingly was initiated about 2 weeks later on site II than on site I. A total of 80 bitterbrush plants on each site were randomly selected with 10 assigned to each of 8 treatments: fall clip, fall clip then water, spring clip, fall burn, fall burn then water, water then fall burn, spring burn, and control. Treatments applied later than August I were considered fall treatments because aerial growth had stopped and seeds had been dispersed although leafabscission had not occurred. Fall treatments were applied during early August 1977 when 97% of the achenes had abscised. Spring treatments were applied in late March on site I and mid-April 1978 on site II when the first leaf on each fascicle was approximately 30% expanded. Earlier spring treatment was prohibited by snow cover. Air temperature, relative humidity, and wind speed during burn treatments were determined with a battery operated fan psychrometer and a hand-held anemometer (Table I). To produce uniform intensity on all burn treatments, plants were burned individually in a plant burner (Britton and Wright 1979). The burner was calibrated to attain a soil surface temperature of about 2600 C at 45 seconds. Water treatments were applied 24 hours prior to, or immediately after burning to simulate a 5-cm precipitation event. Water was applied as a fine mist with a calibrated positive Authors are graduate research assistant, Oregon State University, Rangeland displacement pump. With the post-burn water treatments, water Resource Program, Corvallis97331;associate professor, Oregon Agricultural Ex,periwas applied I minute after the flame subsided. Water was restricted ment Station, and range scientist, USDA-ARS, Burns, Ore. 97720. Clark and Brltton are now graduate research assistant and associate professor. Department of Range to approximately the area of the plant burner by circular metal and Wildlife Management, Texas Tech University, Lubbock 79409. rings ( 1 IO cm diameter) embedded in the soil surface. Soil moisture This paper involved a cooperative effort of Eastern Oregon Agricultural Research Center and USDA-AR& Burns, Oregon 97720. Technical Paper Number 5391, was measured gravimetrically at the time of treatment. Clipped Oregon Agricultural Experiment Station. plants were severed approximately 5 cm above the soil surface to Manuscript received December 29, 1980. ensure removal of all photosynthetic material. JOURNAL OF RANGE MANAGEMENT 36(6), November 1962 711 Treated plants were observed monthly on each site during the summer of 1978 and in June of 1979. Each plant with visible sprouts was recorded. The number of live plants in each of the 8 treatments wassubjectedtochi-squareanalysistadetect statistical

Reseeding, with and without disc harrowing, building of water bars, and piling of slash on utility corridors (restoration), was studied on access roads and pylon sites following construction of the 500 kV Navajo Project Southern Transmission Line in 1973. Reseeding was not successful. Restoration either had no significant positive effect on revegetation or slowed plant succession in the following Qyear period, or had a deleterious effect on amount and quality of revegetation due to the destruction of climax vegetation which survived powerline construction. Reseeding rangeland has been shown to be both successful and economically feasible by many (e.g. Godfrey 1979, Kearl and Cordingly 1975). Successful seeding, however, has been shown to be dependent upon prevailing weather conditions; weed control (Herbel et al. 1973); seedbed preparation (Struth and Dahl 1974, Hull 1974); and sometimes, pretreatment of seeds to enhance germination (Voigt 1978). In previous papers (Hessing et al. 1981a,b) we described the secondary succession of plants after construction of the 500 kV Navajo Project Southern Transmission Line which connects the Navajo Generating Station at Page, Ariz., with Phoenix. In this paper we describe the effects of reseeding and restoration treatments on the initial course of secondary succession. We used an experimental design which allowed us to describe succession following restoration either separately or together with reseeding. The sequence of powerline construction was that a survey strip was bulldozed in 1972. The powerline was constructed in the spring and early summer of 1973 with part of the survey strip serving as an access road for construction. All restoration and reseeding was done after construction in the summer of 1973. Reseeding occurred at the beginning of the annual summer rainy season, thus providing the seeds with a moist seed-bed.

This study was conducted to compare the effectiveness of microwave drying with that of conventional forced-air oven drying of rangeland forage species. The data show that a microwave oven can dry grass forage samples for biomass production estimates without significantly affecting their nitrogen or phosphorus levels. Drying in a microwave for 10 minutes was comparable to drying in a forced air oven at 55’ C for 24 hours. In range surveys, mine reclamation permit programs, and other range forage evaluations, large numbers of relatively small clipped forage samples must be dried. Because of the locations of these surveys and programs, many of the workers do not have access to ovens of the size or number capable of drying these samples. Microwave radiation and other drying methods have been evaluated for stopping microbial and physiological processes and for their effects on the chemical components of plant materials (Darrah et al. 1977; Mayland 1968; Mayland et al. 1978). Mayland et al. (1978) evaluated the effect of freeze drying and oven drying at 40, 56, 70 or loo0 C on the extractable phosphorus (P) in alfalfa and sugarbeets. They concluded that the freeze drying, which caused no loss in dry matter, also caused less organic P hydroloysis than did oven drying. Wolf and Carson (1973) reported that microwave heating of alfalfa samples for 30 seconds, followed by forced-air drying was adequate to inactivate respiration. Microwave treatThe authors are soil scientists, U.S. Department of Agriculture, SEA-AR, High Plains Grasslands Research Station, 8408 Hildreth Rd., Cheyenne, Wyoming 82001 and Laramie, Wyoming, respectively. This article is a contribution from the SEA-AR, U.S. Dep. Agr. in cooperation with the Wyoming Agricultural Experiment Station, published as Paper No. JA 1055, Journal Series, Wyoming Agricultural Experiment Station. This research was supported in part by funds from the Environmental Protection Agency, Interagency Agreement: EPA-IAG-D5-E763. 426 ment resulted in similar nonstructural carbohydrates in the tissue when compared to freeze-dried material. Darrah et al. (1977) found that microwave drying caused heat damage to alfalfa and an orchardgrass-ladino clover mixture after only 12 minutes and 2 minutes of exposure, respectively. Also, levels of acid-detergent-insoluble nitrogen (N) were increased when the alfalfa and grass-clover mixture were exposed to microwave drying. However, drying plant material at 100” C in forced air ovens caused more heat damage than microwave drying. Some state regulatory agencies are requiring that forage samples bedried at 1100 C, which is undoubtedly resulting in heat damage and possible carbon loss. We conducted this study to compare the effectiveness of microwave and standard ovens for drying of rangeland forage species. Microwave drying could be very useful for personnel who are required to dry many herbage samples at remote locations to evaluate whether mine reclamation meets the state and federal requirements. Materials and Methods Samples of a native grass mixture [western wheatgrass (Agropyron smithii Rydb.), blue (Bouteloua gracilis (H.G.K.) Lag. ex Griffiths), buffalograss (Buchloe dactyloides (Nutt.) Englem.)] and of crested wheatgrass (Agropyron cristatum (L.) Gaertn.) were collected in mid-June and mid-August 1979 at the High Plains Grasslands Research Station, Cheyenne, Wyoming. Sample sizes were about the same as would be harvested from native range sites and crested wheatgrass seedings using a 1.92-ft2 (0.18-m2) frame. The sample weights for native and crested wheatgrass were 30 and 60 g, representing yields of 1,680 and 3,360 kg/ha, respectively. Samples clipped in June were placed in small paper bags and dried for 7.5 and 10 minutes in a Litton/Minute Master’ micro‘Use of trade name does not imply endorsement of this product by the USDA, but is used for the information of the reader only. JOURNAL OF RANGE MANAGEMENT 34(5), September 1961 Table 1. The comparison of microwave drying and forced air drying on forage moisture content, nitrogen and phosphorus of crested wheatgrass and a native grass mixture. Drying treatment Native grass mixture Estimated % Moist. % N %P Crested wheatgrass Estimated % Moist. % N %P Mid-June harvest* Microwave 7.5 minutes 36a*** 10 minutes 50b 7.5 + 5 minutes 43ab Forced Air Oven 55” C @ 24 hrs 48b Late-August harvest*** Microwave 7.5 minutes 42a 10 minutes 54b 12.5 minutes 54b Forced Air Oven 55” C @iI 24 hrs 53b 1.7a 1.6a .19a .22a 34a 51b 47b

Late spring grazing by sheep altered the amount of several forage categories available to deer the subsequent autumn and winter. Total herbaceous plant material was much reduced by spring-time sheep grazing, but regrowth following fall precipitation increased the proportion of green herbaceous material available. Current year's growth of bitterbrush was also increased relative to the nongrazed situation due to the release of moisture and nutrients accompanying the removal of herbaceous plants by sheep. Subsequently winter diets of mule deer on the sheep-grazed area were higher in herbaceous components but lower in shrub components than on the adjacent area where sheep had not been previously grazed. Implications of these findings are that quality of deer diets was not detrimentally affected where sheep had grazed during the preceding spring and a much greater animal yield is possible through dual use. A deficit of winter forage apparently limits mule deer (Odocoileus hemionus hemionus) population over much of their range (Aldous 1945; Doman and Rasmussen 1944). This can be viewed in terms of both extent of winter rangeland and quantity of forage (principally shrubs) produced there. The Utah Division of Wildlife Resources estimates that there are approximately 7,424,000 ha of mule deer winter range in Utah, including some 1,149,000 ha dominated by the sagebrush complex, primarily big sagebrush (Artemisia tridentata). However, big sagebrush is viewed as only moderate quality winter forage for deer because of its low acceptability (Smith and Hubbard 1954). This is a particular problem where sagebrush exists in stands devoid of more palatable shrub species. Winter deer losses in Utah appear to be inversely related to the amount of palatable browse species available (Robinette et al. 1952). The grazing of deer winter ranges by domestic livestock is common throughout the Intermountain West. Such ranges are grazed in spring when forage is typically in short supply for the livestock industry. Hence, the generally low state of productivity of these ranges is viewed as a limitation to livestock production (Cook and Harris 1968) as well as to deer production. Recent research indicates that with properly designed grazing strategies, livestock-big game competition can probably be minimized (Jensen et al. 1972; Jensen et al. 1976). Moreover, these same studies suggest that livestock may be used to manipulate vegetation on deer winter ranges to effectively Authors were research assistant, associate professor, and research assistant, respectively., Department of Range Science, Utah State University, Logan 84322. Smith and Fulgham are now, respectively, assistant professor of animal science, Angelo State University, San Angelo, Texas 76901, and assistant professor of animal and range sciences, New Mexico State University, Las Cruces 88003. This report is Journal Paper No. 2249 of the Utah Agricultural Experiment Station, the supporting institution for this research. Authors also acknowledge the Utah Division of Wildlife Resources (UDWR) for providing the study site, the experimental animals, and logistic support. Charles H. Jensen, game biologist, UDWR, assisted in site selection and study design. -Dr. Charles Romesburg and Mr. Kim Marshall, US/IBP Desert Biome Project, were both especially helpful in the data analysis phase of the project. Manuscript received November 14, 1977. increase quantities of browse available to wintering deer. However, the specific responses of mule deer to such grazing systems have not been well established. Thus, the study reported in this paper was designed to determine: (1) the plant species present and available to wintering mule deer following spring-time sheep grazing and (2) the relative proportions of the various plant species in the diets of mule deer during the winter following the spring sheep grazing treatment.

Relative preference for seven important sagebrush taxa in Oregon was established for mule deer and domestic sheep. Mule deer showed highest preference for low sagebrush (A rtemisia arbuscula ssp. arbuscula), mountain big sagebrush (A. tridentata ssp. vaseyana), foothill big sagebrush (a recently recognized variant of mountain big sagebrush) and Bolander silver sagebrush (A. cana ssp. bolanderi). They showed intermediate preference for basin big sagebrush (A. tridentata ssp. tridentata) and Wyoming big sagebrush (A. tridentata ssp. wyomingensis) and least preference for black sagebrush (A. nova). Sheep showed highest preference for low sagebrush and medium preference for black sagebrush. They utilized but did not prefer, Bolander silver sagebrush and mountain and foothill big sagebrush and they showed least preference for Wyoming and basin big sagebrush. Genetic variation between kinds of sagebrush taxa influenced animal preference more than environmental variation within a taxon. Although many articles have been written regarding utilization of sagebrush by both native and domestic animals, confusion still exists regarding which sagebrush taxa are preferred by animal consumers. Two trends in sagebrush utilization by deer are evident in the literature: ( 1) Heaviest use occurs during the winter months, (2) Taxa most often mentioned include big sagebrush (A. tridentata) and low sagebrush (A. arbuscula) (Smith 1950, Kufeld et al. 1973). Likewise with sheep, most utilization takes place during the winter season. Big sagebrush and black sagebrush (A. nova) are the two taxa most often associated with sheep use. Most past research involving utilization of sagebrush has been based on recognition at the generic or, at best species level. A considerable amount of recent literature has shown that species, subspecies, and forms exist, each with their own morphological characteristics and environmental requirements (Beetle 1960; Beetle and Young 1965; Tisdale et al. 1969; Winward and Tisdale 1977; Hanks et al. 1971; Brunner 1972; Hanks et al. 1973, McArthur et al. 1979). Only a few researchers have studied sagebrush utilization at the subspecies and form level under controlled or semicontrolled experimentation (Hanks et al. 1971; Hanks et al. 1973; and Scholl et al. 1977). The purpose of this study was to evaluate relative animal preference for seven important sagebrush taxa in Oregon under conditions where all seven taxa were available for selection. The seven taxa studied included: (I) Artemisia arbuscula Nutt. ssp. arbuscula-low sagebrush (Lo), (2) A. cana ssp. bolanderi (Gray) Ward Bolander silver sagebrush (Bo), (3) A. nova Nelson black sagebrush (B 1), (4) A. tridentata ssp. tridentata Nutt. basin big sagebrush (Ba), (5) A. tridentata ssp. vaseyana (Rydb.) Beetlemountain big sagebrush (Mo), (6)A. tridentata ssp. wyomingensis Beetle Wyoming big sagebrush (Wy) and (7) a relatively low Authors are former graduate research assistant and associate professor. Rangeland Resources Program, Oregon State University, Corvallis, respectively. Mr. Sheehy is presently a rancher in Wallowa, Oregon, and Dr. Winward is regional ecologist for the US Forest Service, Intermountain Region, Ogden, Utah. This article was submitted as Technical Paper No. 5392. Oregon Agricultural Experiment Station, Corvallis. Manuscript received January 28, 1980. elevational variant of A. tridentata ssp. vaseyana referred to in this paper as foothill big sagebrush (Fo). Nomenclature follows Beetle (1960) and Beetle and Young (1965) except for the last taxon which was encountered in Oregon but at the present time is not an officially recognized subspecies.

Information on the potential loss of forage that might be expected from grasshopper feeding in a given season would benefit ranchers and land managers if the loss could be estimated in the spring before peak forage production. A method was developed for forecasting such losses on the northern mixed prairie when most species of grasshoppers are in the 3rd and 4th instars. The method is based on the assumptions that forage losses (forage consumed + destroyed) are directly proportional to grasshopper size and density and that during the period between the 3rd instar and death, which usually does not exceed 46 days, density decreases linearly to 0. Using feeding ratios (weight of forage destroyed/weight of adults), losses/day were calculated for each of 26 grasshopper species and for 3 groups of species separated by weight. Forecasted loss estimates for any population can be estimated if the density and species are determined, or a loss of 43 mg/grasshopper feeding day could be used as a general average if species cannot be identified. Forecasted losses are related to grasshopper density and to observed losses at one site in Montana during a 3-year period. Grasshoppers continue to be the most widespread and destructive pests on rangeland in the western United States. In 1979, for example, 7.2 million acres were treated by APHIS to prevent forage and crop destruction (Shannon Wilson, personal communications). Several workers have reported in the review paper by Hewitt (1977) on the effect of grasshoppers on the rangeland ecosystem. Estimates of forage losses have been determined for individual species and field populations after the losses have taken place; however, information has not been available on which to forecast losses. Forecasting is difficult because of the many highly variable interactions between an unstable environment and grasshopper development. Seasonal weather patterns directly affect the density of newly hatched nymphs in the spring and the growth and Authors are with the Rangeland Insect Laboratory, Agriculture Research Service, U.S. Department of Agriculture, Bozeman, Montana. maturation of adults during the summer and fall when eggs are laid. Precipitation and cool weather can not only cause early instar mortality and reduced feeding, but also promote above-normal forage production that may offset the forage destroyed by grasshoppers. However, forage losses depend mainly on grasshopper density, species composition, and weather conditions from the time of hatching until death in the fall. The effect of weather on grasshopper populations cannot be predicted, but information on species and density can usually be obtained before much forage has been destroyed. Planning for the control of grasshoppers during outbreaks or population increases would be facilitated if losses could be forecast in the spring before forage production peaked. Ranchers could use such forecasts in determining the correct stocking rates and use of rest rotation pastures. This paper describes a method of forecasting forage losses on the northern mixed prairie of the United States. Forage loss predictions are related to grasshopper density and to forage reduction in clipped plots during a 3-year period 1975-1977 in Montana. Forecasts are based on the grasshopper species present and their density when the majority of the individuals are in the 3rd and 4th instars, which is after moderation of very high levels of natural mortality that occur among earlier instars (Pickford 1960), but is before forage losses become significant (Hewitt 1979). The proposed method for forecasting losses was developed for use by range people and extension personnel and thus an attempt was made to present a quick and efficient method that would have wide application. Methods and Materials Grasshoppers were collected from several locations in Montana and Wyoming over several years. For 26 species, dry weights were determined of both sexes of the 4th and 5th instars and adults. These 26 species were divided into three groups on the basis of adult dry weight (weight of sexes averaged): Group A (0-65 mg), JOURNAL OF RANGE MANAGEMENT 35(1), January 1982 53 This content downloaded from 207.46.13.113 on Sun, 24 Apr 2016 05:37:28 UTC All use subject to http://about.jstor.org/terms Group B (66-120 mg), and Group C (>120 mg). The amount of forage destroyed (consumed + wasted) by nymphs of Camnula pellucida (Scudder) and Amphitornus coloradus (Thomas) from hatching to the adult stage was obtained from the literature(Misra and Putnam 1966). The total forage destroyed (810 mg) by these two species was divided by the total adult dry weight (179.2 mg) to obtain a nymphal feeding ratio of 4.5. This ratio was multiplied by the average dry weight of individuals within both the 4th and 5th instar to give the amount of forage destroyed during the two instars by each of the 26 species (Table 1). Information on the amount of forage destroyed on a daily basis by adults of Melanoplus sanguinipes (F.), M. infantilis Scudder, M. foedus Scudder, and Aulocara elliotti (Thomas) was obtained from the following sources: Parker (1930), Barnes (1955), Smith (1959), Mitchell and Pfadt (1974), Hewitt et al. (1976), Hewitt (1978), and unpublished field data. Adult feeding ratios for these species were determined by dividing the amount of forage destroyed/day by the average dry weight of the adults and then averaging the four feeding ratios to obtain an adult feeding ratio of .65. This adult ratio (.65) was multiplied by the average dry weight of adults of the 26 species to give the foragedestroyed/daybyeach species (Table 1). The amount of forage destroyed by the 26 species was estimated by using 46 days as an average life span beginning with the 4th instar; 7 days were allowed for each of the last instars, and 32 days for adult life. The average loss/ day was determined for each of the three groups by totaling the lossesfor the 4th and 5th instar and the adults for each species within the group. Thus, estimated average group losses per day/ species were 26 mg for those species in Group A, 49 mg for those in Group B, and 109 mg for those in Group C. Density data from grasshopper populations during 1975 through 1977 near Roundup, Montana, were used to verify the forecasting method. These were the same density data that were used earlier to support a study of hatching and development in relation to forage growth, temperature, and precipitation. (Hewitt 1979). Twenty collections of grasshoppers were taken weekly along transect lines near a 1-ha exclosure; 22 such collections were made in 1975 from May 14-Oct. 6; 19 in 1976 from May 25-Sept. 28; and 16 in 1977 from May I O-Aug. 17. Collections were made by using a vacuum quick trap during the evening or after dark when temperaTable 1. Estimated forage loss for rangeland grasshopper species, grouped according to adult dry weight,fora 46-day period (both 4th and 5th instars last 7 days each and adults live 32 days). Estimated forage loss (mg)2 Dry wt X Dry wt X Dry wt Dry wt (mg)' 4.5 X .92 4.5 X .77 X .65 Species 4th instar 5th instar Adult 4th instar 5th instar Adult/day Total species GROUP A dry wt = 0 to 65 mg Aeropedellus clavatus (Thomas) 10.7 22.2 45.8 44.3 76.9 29.8 1074.8 Ageneotettix deorum (Scudder) 11.8 27.4 58.8 48.9 94.9 38.2 1366.2 Amphitornus coloradus (Thomas) 19.3 38.0 63.7 80.0 131.7 41.4 1536.5 Cordillacris occipitalis occipitalis (Thomas) 10.6 12.7 32.1 43.9 44.0 20.9 756.7 Melanoplus dawsoni (Scudder) 18.7 26.1 55.2 77.5 90.5 35.9 1316.8 Melanoplus infantilis Scudder 12.5 28.1 52.1 51.8 97.4 33.9 1234.0 Philbostroma quadrimaculatum (Thomas) 14.0 20.6 59.4 58.0 71.4 38.6 1364.6 Psoloessa delicatula (Scudder) 12.0 21.0 43.0 49.7 72.8 28.

Expressing the effects of grazing animals on herbage requires explicitly defined variables describing herbage growth and herbage disappearance, as well as variables describing net changes in herbage. This paper presents a mathematical framework on variables describing herbage growth, disappearance, and accumulation, which can be used to model herbage dynamics, and to develop and present field research. Describing herbage dynamics with or without livestock grazing requires measurement of both herbage growth and disappearance. Sequential measurements of standing crop define net changes in standing crop but do not indicate the changes that occurred in growth and disappearance. Often this distinction is essential in understanding and comparing effects of grazing management on herbage dynamics. We often hear that grazing systems (Society for Range Management 1974) such as short-duration grazing will maintain or increase growth rate of herbage, but less is said about effects on herbage disappearance. Similarly, in sampling during grazing studies, we usually emphasize standing crop measurements, while growth and disappearance measurements are often ignored. In general, while growth and disappearance have been frequently described and modeled in plant sciences, there is a need to mathematically formalize basic variables for application in grazing research. Quantification of dry-weight changes per unit area in standing crop, herbage growth, and herbage disappearance requires clearly defined variables developed from principles of systems analysis. Relationships among these variables should be clear and mathematical description of each variable explicit. This paper (1) defines concepts of herbage growth, herbage disappearance, and herbage accumulation; (2) offers a mathematically defined terminology for describing components of standing crop dynamics, and examines its relationship to previous papers on herbage terminology; and (3) discusses the importance of measuring herbage growth and disappearance in evaluating herbage dynamics in field grazing

A conceptual model of secondary succession was tested with data from disturbed vegetation in theAgropyron/Poa habitat type using a combination of classification and ordination techniques. Individual stands were classifled into communities by an agglomerative method. Results of the Bray-Curtis polar ordination using three endpoint selection methods supported the validity of the model. The model is visualized as a solid cone in which all of the plant communities included in a habitat type are positioned relative to their degree of disturbance, inferring their probably secondary successional pattern within habitat types. Most of our nation's range vegetation is in some stage of secondary succession. One of the aims of modern resource management is to direct plant succession toward a desired seral stage in order to obtain maximum productivity or stability (Stoddart et al. 1975). Williams et al. (1969) point out that natural succession may be the most economical means, and in many inaccessible areas the only means, to restore the resource to a level of production that can be managed economically. In order to use secondary succession as a tool to attain this level, it is essential to have a better understanding of seral communities. Reviews on succession were made by Drury and Nisbet (1973) and Golley (1977). Tree age data are widely used in study of forest succession (Botkin et al. 1972; Zedler and Goff 1973; Horn 1975). Because age of perennial herbs is not determinable, the same approach cannot be applied to study secondary succession of grassland vegetation. This paper deals with testing of a conceptual model of secondary succession in which age of plant is not involved. The relatively recent availability of computer and multivariate analytical techniques adapted for vegetational analysis permit researchers to analyze and interpret large quantities of data. These techniques help reveal relationships of plant communities not previously possible. Reviews in use of multivariate techniques as applied to plant ecology have been published by Crovello (1970), Goodall (1970), Williams (1971), Orloci (1973), Clifford and Stephenson (1975), and others. The purpose of this study was to test the validity and soundness of a conceptualized model of secondary succession that was developed recently. The model is visualized as a solid cone with the climax plant community situated at the At the time of the research, authors were with the College of Forestry, Wildlife, and Range Sciences, University of Idaho, Moscow 83483. G. Huschle's present address is U.S. Fish and Wildlife Service, Roy, Montana 59471. The paper is published with the approval of the director, Forest, Wildlife, and Range Experiment Station, Univ. of Idaho, as Contribution No. 53. This study was part of a United States Army Corps of Engineers contract with the Idaho Cooperative Wildlife Research Unit, College of Forestry, Wildlife and Range Sciences, University of Idaho Daa in this study were collected by personnel of the Idaho Cooperative Research Unit. Special thanks are extended to Dr. Duane Asherin, Mr. James Claar and Mr. Jerry Lauer for their contributions to the study. Manuscript received December 15, 1978. apex and associated seral communities positioned in their respective positions in the remaining portion of the cone. The solid cone model may be illustrated by a habitat type, for example, which is defined as the collective area of land supporting or capable of supporting a specific climax plant community (Daubenmire 1970). Secondary succession within a habitat type is a continuum of plant communities whose endpoint is the climax vegetation. Within the habitat type there may be numerous plant communities in various stages of secondary succession. Conceptually, secondary succession can be viewed as a solid cone in which are contained all the plant communities associated with a single habitat type or having the same successional endpoint. The solid cone includes all of the disturbed communities within a habitat type, converging to the climax community that is positioned at the upper portion of the cone (Fig. 1). As succession returns 'oward climax, the vegetational compostion changes continuously until it reaches the climax association. Toward the base of the cone, numerous communities exist because different kinds and intensities of disturbance result in different vegetation. If the disturbance is severe enough, a community with a single pioneer species or finally the base level of the cone, bare ground, may result. While secondary succession is a vegetational continuum, it is convenient to recognize community types and seral stages for practical management. A community type of one habitat type may have greater resemblance to a seral community of another habitat type than to one of its own. All community types are not unique to a habitat type. This is shown by the overlap of community types of two adjacent habitat types in Figure 1. Secondary succession can be studied by investigating

The daily mean energy expenditure of free-ranging heifers grazing crested wheatgrass rangeland was estimated as 161 kcal/kgBW,75/day using the carbon dioxide entry rate technique (CERT). This was 46% greater than the mean 110 kcal/kgBW 75/day estimated for stall-fed heifers consuming similar forage. Under laboratory conditions, CERT can provide a mean estimate of energy expenditure that has a standard error of 5% and a coefficient of variation of 20%. In contrast to the stall-fed animal, the range animal requires additional dietary energy to meet the demands of its free-roaming condition. For sheep on pasture, Young and Corbett (1972) reported a 60-70% increase in daily energy expenditure above the maintenance costs of penned sheep. Young (1970) and Wallace (1956) have reported 60% and 50% increases, respectively, for grazing cattle. These substantial increases in energy expenditure have several possible origins. Osuji (1974) reviewed the literature on the energy expenditure of the pastured ruminant and suggested that the increased energy costs might be due in part to an increased amount of time spent obtaining food and the locomotion associated with grazing. For example, 40% of the energy expended by grazing sheep has been attributed to their activities of standing, walking, ruminating and eating as compared to 10% for a penned animal consuming roughages (Graham 1964). Each hour spent grazing by cattle represents a 2% increase in daily energy expenditure (Holmes et al. 1978). Cattle on crested wheatgrass rangeland typically spend 7.7 to 10 hours daily grazing (Scarnecchia 1980). Additionally, the daily time spent grazing increases as the quantity of available forage declines (Nastis 1979), although cattle seldom graze longer than 13 hours a day, irrespective of forage conditions or availability (Arnold and Dudzinski 1978). The energetic cost of travel on level terrain has been estimated as 0.45 to 0.78 kcal/kgBW/km (Blaxter 1962, Graham 1964, Osuji 1974). Although travel involves a negligible expense for the stallfed animal, various researchers have reported traveling distances of 5 to 12 km a day for cattle on western U.S. ranges (Dwyer 1961, Herbel and Nelson 1966, Malechek and Smith 1976). Thus, travel could easily add 10% to the daily energy expenditure of the grazing animal. Additional unknown stress-related factors also may contribute to increases in energy expenditure when animals are forced to search for food under conditions of scarcity. The extent to which Authors are assistant professor, Department of Animal and Range Science, Montana State University, Bozeman, and professor, Department of Range Science, Utah State University, Logan. At the time of this research. Havstad was research assistant, Range Science Department, Utah State University. This paper was approved by the Director, Utah Agr. Exp. Sta. as Journal Paper No. 2727. Manuscript received in 1980. free-roaming conditions increase the energy expended by the grazing ruminant warrants a close examination of factors affecting energy expenditure. This knowledge would be important in planning grazing management systems, particularly those that have as their objective uniform grazing, which may tend to stress animals. Thus, the purpose of this study was to measure the energy expenditure of grazing heifers at several different levels of available forage, and to compare these quantities to the energy expended by similar stall-fed animals consuming a diet of similar quality and quantity. Precise estimates of energy expended by the free-roaming animal are limited byavailabletechnology. Techniques for indirect estimation of energy expenditure include time budget analysis and food intake balance and energy balance models. These techniques are either still being tested or may be limited by numerous assumptions involved in their application. For direct estimation of energy expenditure, accepted and applicable methods of indirect calorimetry include respiratory gas exchange (Young et al. 1975), heart rate and respiratory rate estimation (Yamamoto et al. 1979), and the carbon dioxide entry rate technique (CERT) (Whitelaw et al. 1972). Typically, gas exchange methods require fistulation of the trachea, and the associated equipment required for gas measurement is cumbersome. Young and Corbett (1972) reported that this technique estimated energy expenditure with a standard mean error of 12%. The heart rate measurement technique has been used with increasing frequency during recent years. Each animal's heart rate must be calibrated with their oxygen consumption, and this relationship varies with cardiac stroke volume and responses to emotional factors (Brockway 1978). Yamamoto et al. (1979) reported a mean standard error of 16% when heart rate was used to estimate energy expenditure of cattle. CERT has been suggested as the most suitable measurement for estimating energy expenditure of the grazing ruminant (Webster 1972). However, mean standard errors of 7 to 20% for energy expenditure estimates have been reported by users of CERT (Young et al. 1969, Whitelaw et al. 1972). Methodology is apparently best chosen on the basis of availability and suitability of a particular technique and its associated equipment to conditions at hand rather than upon attainment of a prescribed limit of statistical reliability. Due to the availability of the necessary equipment, CERT technology was selected for the experiment reported here.

In the northern Great Basin, populations of black-tailed jackrabbits (Lepus californicus) are cyclic, reaching high densities at approximately 10-year intervals. This project examined impacts of jackrabbits during a peak in their cycle on sagebrush-steppe vegetation in southeastern Idaho. Total vascular plant cover was significantly lower on plots open to jackrabbit herbivory than on exclosure plots, but in no case was cover of a specific species significantly reduced on open plots. The most severe impacts were on shrubs during winter; most aboveground tissues of both winterfat (Ceratoides lanata) and green rabbitbrush (Chrysothamnus viscidiflorus) plants were completely eaten by spring. However, these impacts were largely ameliorated by compensatory growth during the following growing season, and there was no difference in total biomass for either species between the open and protected plots by July. New growth of winterfat plants that had been browsed the previous winter was significantly greater than that of protected plants. Thus, although the cumulative effects of herbivory reduced total plant cover, no single species was irreparably impacted. Over a year, jackrabbits exert feeding pressure on nearly all of the important species in these communities; therefore, these hares do not appear to apply differential grazing pressure that would alter the course of vegetation development on northern Great Basin rangelands. The black-tailed jackrabbit (Lepus californicus) is an important native herbivore on rangelands in the western United States (Vorhies and Taylor 1933, Dunn et al. 1982). In northern portions of the species' range, populations are cyclic, reaching high densities at approximately 10-year intervals (Gross et al. 1974, Johnson and Peak 1984). Numerous studies of food preferences and seasonal dietary trends for black-tailed jackrabbits provide a reasonably complete picture of feeding behavior (see Johnson and Anderson 1984), but the effects that black-tailed jackrabbits have on native plant populations are not completely understood. It is generally assumed that peak population densities will have severe impacts on range ecosystems (Vallentine 1971, MacCracken and Hansen 1984), but speculation about such impacts has been based largely upon casual observation. Vorhies and Taylor (1933) argued, "Under all but the most conservative stocking with cattle the tendency of grazing by jackrabbits will be to accentuate overgrazing, to eliminate the more palatable grasses and favor their replacement by somewhat less desirable species and by weeds." In contrast, Bond (1945) speculated that jackrabbits would "exert a force in favor of succession toward the climax" on range that was only moderately deteriorated, whereas on range "deteriorated to the point of having more weeds than grasses, their effect would be towards further deterioration." More recently, Rice and Westoby (1978) found that protection from jackrabbits for periods of 5 to 15 years had no consistent effects on vegetation. The impacts of jackrabbit herbivory on long-term vegetation trends are complicated because jackrabbits may suppress or eliminate certain species (Westoby 1974, McKeever and Hubbard 1960) or enhance propagule dispersal of others (Riegel 1941, 1942; Timmons 1942). This project was initiated to assess the impacts of a high populaAuthors are professor and senior research assistant, Department of Biological Sciences, Idaho State University, Pocatello 83209. This paper is a contribution from the Idaho National Engineering Laboratory Ecological Studies Program, supported by the Office of Health and Environmental Research, U.S. Department of Energy. We thank T. Dieffenbach, R. Wilkosz, and D. Pavek for field assistance. Dr. E. Fichter, O.D. Markham, S.J. McNaughton, and R.S. Nowak provided helpful comments on the manuscript. Manuscript accepted 25 July 1985. tion density of black-tailed jackrabbits on sagebrush-steppe vegetation and to examine those impacts in relation to long-term trends in vegetation development. In this paper, we describe the shortterm impacts of a peak in a jackrabbit population on cover, biomass, and leaf length of several important plant species and discuss the implications of these measurements in relation to vegetation

Germination characteristics of Maximilian sunflower (Heliunthus maximiliana Schrad.) and awnless bushsunflower (Simsia c&a Engelm. & Gray) Gray were evaluated at water potentials of 0, -.25, -0.50, -0.75, and -1.0 MPe under alternating temperature regimes of 10/20,15/25,and 20/30” C in controlled environmental chambers. Cumulative germination was greatest for both species at water potentials of 0 and -0.25 MPa in the 15/250 C temperature regime. Germination total and rate were depressed for both species in the lo/200 C regime. The 20/30° regime depressed total germination but increased germination rate. The adverse effects of more negative water potentials (-0.75 and -1.0 MPa) were more pronounced at low temperatures for awnless bushsunflower and high temperatures for Maximilian sunflower. ‘Aztec' Maximilian sunflower (Helianthusmaximiliana Schrad.) is an erect, perennial forb with one to several stems (1 to 2 m tall) and short rhizomes (Rechenthin 1972, Texas Agricultural Experiment Station 1979). This cultivar is adapted to the southern threefourths of Oklahoma and all parts of Texas except the Trans Pecos region (Thornburg 1982, Wasser 1982). ‘Aztec’is adapted to most soil types, except where prolonged saturation or salinity is a problem (Texas Agricultural Experiment Station 1979). Plants provide forage for livestock, cover and food for wildlife, and showy yellow flowers for landscape beautification (Rechenthin 1972). Awnless bushsunflower (Simsia calva (Engelm. & Gray) Gray) is a multi-branched, spreading, perennial forb occurring on limestone and calcareous soils in Central Oklahoma and in the Coastal Prairie, Cross Timbers, South Texas Plains, Edwards Plateau, and Trans Pecos regions of Texas (Gould 1975, Soil Conservation Service 1980). Plants are readily grazed by sheep, goats, and deer, and to a lesser extent by cattle (Rechenthin 1972). Both of these species could be used in mixtures to provide greater diversity for revegetation plantings on disturbed rangelands in the Southern Great Plains. However, a better understanding of their ability to germinate and develop under different environmental conditions must be obtained in order to effectively establish and manage them (Sutton 1975). The objective of this study was to investigate the effects of different temperature X water potential regimes on germination characteristics of ‘Aztec’ Maximilian sunflower and awnless bushsunflower. Materials and Methods Seed of ‘Aztec’ Maximilian sunflower and PMT-856 awnless bushsunflower were obtained from the Soil Conservation Service Plant Materials Center, Knox City, Texas. Seeds were harvested in 1981 and were stored for 5 months at 16OC and 40% relative humidity prior to germination trials. Lots of 100 uniformly sized seeds were dusted with Captan (US-N-(Trichlor-omethyl) thio)-4 -cyclohexene 0 1,2dicarboximide) and placed on 1 piece of Whatman No. 1 chromatography paper in 13 X 13.5 X 3.5 cm plastic trays. The chromatography paper was supported by a 5-mm thick Authors are graduate research assistant and assistant professor, Range Science Department, Texas A&M University, College Station 77843. This research was supported in part by a grant from the Center for Energy and Mineral Resources, Texas A&M University, College Station 77843. The authorsgratefullyacknowledge the USDA-SCS Plant Materials Center. Knox City, Texas, for providing seeds used in this study. Published with approval of the Director, Texas Agricultural Experiment Station, as TA-19669. Manuscript accepted October I, 1984. 336 piece of polyurethane foam with 5 cotton wicks which extended into a 200-ml reservoir of solution. Solutions had water potentials of 0, -0.25, -0.50, -0.75, and -1 .O MPa, which were derived from 20,000 MW polyethylene glycol. Trays were wrapped with clear polyethylene film to reduce evaporation and stabilize the relative humidity. Trays were placed in controlled environmental chambers with night/day temperature regimes of 10/20, 15/25, and 20/ 30° C and 1Zhour photzperiods. During the day period, a light intensity of 450 urn01 l m . sec.’ was maintained at tray level. Germinated seeds were counted every other day over a 21day period. A seed was considered to have germinated when it had at least 1 cotyledon exposed and a radicle greater than or equal to 5 mm in length (Copeland 1978). The experiment was arranged in a completely randomized design with 3 replicates (trays) per treatment, and each treatment was replicated twice over time. Germination data were transformed with an arcsine transformation prior to statistical analysis by analysis of variance (Steele and Torrie 1960). The effects of substrate water potentials and alternating temperature regimes on germination percentages were analyzed by the use of a quadratic response surface (Evans et al. 1982). Results and Discussion Cumulative germination of Maximilian sunflower was greatest at substrate water potentials of 0 and -0.25 MPa in the 15125°C temperature regime (Fig. 1). At the same substrate water potentials, germination decreased 7% as alternating temperatures were lowered to 10/20°C and 16% as alternating temperatures were elevated to 20/ 30” C. Germination remained at or above 60% in all 3 temperature regimes when substrate water potentials decreased to -0.50 MPa, but was significantly reduced when substrate water potentials decreased from -0.50 to 0.75 MPa and from -0.75 to -1.0 MPa. Cumulative germination of awnless bushsunflower was greatest at the 0 MPa substrate water potential level in the 15/25’C temperature regime (Fig. 2). Germination remained at approximately 48% when substrate water potential decreased to -0.25 MPa in the lo/ 20°C and 20/ 30°C temperature regimes, and -0.50 MPa in the 15/25’C temperature regime. As with Maximilian sunflower, germination was significantly reduced in all 3 alternating temperature regimes when substrate water potentials decreased from -0.50 to -0.75 MPa and from -0.75 to -1.0 MPa. Favorable planting dates can be selected on the basis of these temperature and moisture requirements for germination and a knowledge of seasonal temperature and moisture conditions of the area to be revegetated (Ashby and Hellmers 1955). Based on precipitation and dry period possibilities and soil temperatures in central Texas (Dugas 1983, 1984), optimum germination for both species occurs in March and April. Therefore, both species should be planted in early spring. Favorable microclimatic conditions prevailing in the immediate vicinity of the seed may override overall climatic factors and extend planting dates for both species (Mayer and Poljakoff-Mayber 1982). Germination was initiated earlier, rate of germination was increased, and highest level of germination was reached at an earlier date with increasing temperature for both species (Fig. 3 JOURNAL OF RANGE MANAGEMENT 38(4), July 1985 Fig. 1. Quadratic response surfacefor cumulative germination percentage of ‘Aztec’ Maximilian sunflower seeds in relation to substrate water potentials and alternating retnperarure regimes. Values in parentheses are one-half rhe width of calculated confidence intervals. and 4). In the lo/ 20° C temperature regime, germination started at day 5 (an average of the 0, -0.25, and -0.50 MPa substrate water potentials) and continued through day 21 without reaching the highest ultimate level of germination. In the 15/25’C temperature regime, germination initiated at day 3 and leveled off after day 18. In the 20/30°C temperature regime, germination started at day 2 and reached the highest level of germination after day 10. Germination rates were negligible for both species at -1.0 MPa water potential in all 3 alternating temperature regimes. The rates of germination and initial seedling growth can be critical factors in the success or failure of seeding operations on wildlands (Hillel 1972). Fast germination and establishment is desired because favorable temperature and moisture conditions last for only short periods of time under field conditions. TemperFig. 2. Quadratic response surfacefor cumulative germination percentage of awnless bushsunflower seeds in relation to substrate water potentials and ahnerating temperature regimes. Values in parentheses are one-half the width of calculated confidence intervals. atures at the high end of the favorable range for germination shorten lag times and accelerate rates of germination, thus allowing germination to occur under transiently favorable water conditions (McDonough 1977). When averaged over substrate water potentials of 0, -0.25, and -0.50 MPa, Maximilian sunflower seeds attained 50% germination in approximately 12 days at lo/ 20” C (Fig. 3A). At 15/25 and 20/30°C approximately 10 and 8 days, respectively, were required for 50% of the seed to germinate (Fig. 3B and 3C). When averaged over the same substrate water potentials, awnless bushsunflower requires approximately 20, 11, and 9 days for 40% seed germination to occur at respective temperatures of 10/20, 15/25, and 20/3O“C (Fig. 4A, 4B, and 4C). Sorensen and Holden (1974) investigated the germination characteristics of other native species in the Asteraceae family that are found in Southern Great Plains. Under controlled environmental conditions (constant temperature of 21°C, complete darkness, and a continually moist filter paper substrate), common yarrow (AchilJOURNAL OF RANGE MANAGEMENT 38(4), July 1985 337

A S early as the late eighteenth century stockmen were concerned with the relationship between pasture forages and the behavior of animals grazing them. James Anderson (1797), who farmed in Scotland, described grazing habits of animals and outlined certain procedures which he felt would give greater production from pastures. One hundred and forty years elapsed before any further large-scale studies were reported in which an effort was made to relate the effects of forage characteristics to the grazing and milk production of dairy cows. Hancock (1950)) working under New Zealand conditions, reported the conclusions drawn from four years’ work during which nearly 2,000 cow-days of grazing were recorded. While the data from which the observations were made were not reported, several of the conclusions are of great interest to workers in the field of grassland management. Of particular interest is the observation that the time spent grazing and the subsequent time required for ruminating are interdependent. Either of the periods may be limited or prolonged by the other and, in the case of prolonged ruminating time, total forage intake may be limited by insufficient time for grazing. To enable this relationship to be depicted, the use of the formula ( ruminating time grazing time = rt/gt ratio > was suggested and used in this paper. The relationship between grazing behavior and the quantity and quality of forage available per cow is perhaps the newer and more interesting of the reported findings. Waite, et al. (1951) reported on two years’ work in Scotland during which an effort was made to relate the forage conditions, grazing behavior, and other factors to the forage intake of the animals under study. He explained the difference in intake between forages characterized as long stemmy material of low moisture content and its opposite on the basis that the rumen is less densely packed when the animal receives the feeling of repletion, thus, giving shorter grazing periods and less dry matter intake. On the short materials of high moisture content, the forage tends to pack in the rumen and the animal grazes longer and takes a greater quantity of forage into the rumen before the state of fullness is reached. The workers found no apparent relationship between the time spent grazing and stage of lactation, individual milk yield, or live weight. It is the purpose of this paper to describe the techniques being used at the Georgia Experiment Station and some of the preliminary data obtained during the first phases of a long-time study of pasture utilization by dairy cows.

R OTATION grazing composed one of the panel periods at the third annual meeting of the Range Society held in San Antonio, Texas, in January, 1950. Several papers on the subject were read and lively discussions followed. It soon became apparent that much diversity of opinion exists among both research workers and operators regarding the merits of rotation grazing. Some of these differences seem to stem back to confusion in terminology, as between rotation and deferred grazing; others to the more broadly accepted objectives of these grazing systems, still others to a combination of the two. The importance of this subject prompted Editor Dr. R. S. Campbell to request the authors to prepare their papers for publication in the Journal, preferably in a single issue. He also proposed that the writer edit the series, prepare a brief review on the subject of rotation grazing, list the most pertinent references, and perhaps draw some conclusions on the merits and application of rotation grazing. All agreed to carry out these proposals.

the plastic. A backing sheet is pressed in place, and the mount is trimmed to size on a paper cutter. Another sheet of adhesive plastic makes the best backing but increases t h e cost. This makes a completely waterproof and flexible mount. Acetate plastic, tracing cloth, and botany paper all make satisfactory backing material at much less cost. Self-laminating plastic is available from most stationers and office suppliers in a variety of weights and sizes. Prices vary from 40 to 75 cents per square foot. Materials for a 4 by 6 inch mount using botany paper backing costs about 12 cents.

This paper describes the spectral light reflectance characteristics of giant reed (Arundo donax L.) and the application of aerial color-infrared photography and videography for distinguishing infestations of this invasive plant species in Texas riparian areas. Airborne videography was integrated with global positioning system (GPS) and geographic information system (GIS) technologies for mapping the distribution of giant reed. Field spectral measurements showed that giant reed had higher near-infrared reflectance than associated plant species in summer and fall. Giant reed had a conspicuous pink image response on the color-infrared photography and videography. This allowed infestations to be quantified using computer analysis of the photographic and videographic images. Accuracy assessments performed on the classified images had user's and producer's accuracies for giant reed that ranged from 78% to 100%. Integration of the GPS with the video imagery permitted latitude-longitude coordinates of gi...