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This paper documents changes in the size of a breeding population of Yosemite toads, Bufo canorus, over 20 years at Tioga Pass, California. Surveys of B. canorus numbers in breeding aggregations were made yearly from 1971 to 1982, and less systematic observations were made from 1983 to 1991. Six other populations in the eastern Sierra Nevada were surveyed occasionally from 1973 to 1990. The total number of marked males entering the largest breeding pools at Tioga Pass declined nine-fold from 1974 to 1982. The mean number of toads found in daily searches during breeding also dropped over the 20 year study. Similar declines occurred at smaller breeding sites throughout Tioga Pass Meadow and at the six other populations. In 1990 we found evidence for continued reproduction by B. canorus at all but one location (Sylvester Meadow), although reproduction was minimal at Tioga Pass. No single source of mortality was responsible for all the declines. We interpret the decline in our study populations as caused primarily by drought, disease, and predation. Spring snow depths in 1976,1977 and 1987-1991 were below the 62 year average, resulting in low tadpole survival. The death of adults from disease at Tioga Pass, and from predation at another site (Mildred Lake) also contributed to the declines. Although habitat destruction and localized human activities were not major factors, some natural variables responsible for the declines may have had anthropogenic components.

Data from a long-term field study show that adult White-crowned Sparrows were often engaged simultaneously in parental care and in postnuptial molt indicating that these functions were not prohibited from overlapping by energetic constraints and that there is strong selection for molt not to be delayed unduly. There was no constant phase relationship between stage of reproduction and initiation of molt. In this sense, the two functions appeared to be scheduled and regulated separately. The seasonal schedules for onset of gonadal refractoriness and of postnuptial molt were nearly identical, however, and all indications are that molt began in individuals right after refractoriness. This raises the distinct possibility that one mechanism or set of hormonal conditions could be inducing both events simultaneously.

Movements of White-crowned Sparrow Zonotrichia leucophrys oriantha fledglings in relation to their nest sites were measured for 37 broods on a large subalpine meadow, Tioga Pass Meadow (TPM). Broods were split between the parents upon fledging and the resulting family subunits appeared to move independently. Three weeks after fledging and about when young were becoming independent, family subunits were located a mean distance of 200 m from their nests. Additional data on movements of independent juveniles were obtained from a trapline on TPM in which we captured individuals originally banded in their nests either at TPM (locals) or at other sites (nonlocals) up to 5 km away from TPM but within the same watershed. Although some siblings traveled together at least until fall migration, considerable dissolution of families occurred at 35 to 40 days of age. At that same age, nonlocal juveniles began to appear in the TPM trapline. First captures of known age nonlocals of both sexes from within a 5 km radius of TPM peaked at age 50-55 days. The majority of nonlocals were probably more than 60 days of age upon arrival at TPM, however, and we assumed that they probably had also traveled more than 5 km from their natal sites.

Changes in herbaceous plant density and canopy cover of creosotebush (Larrea tridentata Sesse & Moc. ex DC) and associated shrubs following brush control treatments were measured in Sonoran and Chihuahuan Desert communities. Treatments were applied in 2 successive years st the Santa Rita Experimental range, Arizona, and 3 locations in Chihuahua, Mexico. Across all locations and years 1.5 kg/ha tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N'-dimethylurea) > 1.0 kg/ha tebuthiuron= disking = disking with furrowing >2-way railing >0.5 kg/ha tebuthiuron > land imprinting in reducing canopy cover of creosotebush and associated shrubs. At the Santa Rita Experimental Range annual precipitation was above long-term mean in 1982, 1983, 1984, and 1985; and grass density increased on all treated and untreated plots. Annual precipitation was below long-term mean during 1986 and 1987 and grass density decreased on both treated and untreated plots but did not decrease to pre-treatment densities. Forb densities were less than 3 plants/m2 throughout the study, except in 1987 when Russian thistle (Salsola iberica Sennen & Pau) increased on all plots. At the Chihuahuan locations, grass densities usually increased during the first year of the study, but very low precipitation throughout the study caused subsequent reductions in grass and forb densities. In dry years brush control treatments did not increase herbaceous plant density.

Perennial grasses were seeded by drilling or broadcasting on 4 mechanical and 3 herbicidal weed control and/or seedbed preparation treatments at 4 semidesert grassland sites invaded by creosotebush (Zarrea tridcnutu) in the Chfuahuan and Sonoran Deserts. The cultivars ‘Cochise’ Atherstone lovegrass (Eragrostis lehmanniana X Eragrostis trichophera) and ‘Catalina’ Boer lovegrass (Effrgrostis curvuIo var. coqferta) lovegrasses were initially established and persisted in 6 of the 8 plantings on disk plowed and disk plowed plus contour furrowed seedbeds. These grasses were established and persisted in 2 of the 5 plantings made in creosotebush stands treated with tebuthiuron [JV-(S-(l,l-dimethylethyl)1,3,4-thiadizol-2-yl)imethylurea] at 0.5, 1.0, and 1.5 kg a.i/ha rates. Grasses established initially on two-way railed and land imprinted areas usually died within 3 or 4 years. Creosotebush (Larrea tridentata), a woody perennial shrub, has invaded the semidesert grasslands within the Chihuahuan and Sonoran Deserts of North America (Humphrey 1958, Buffington and Herbel 1965, Hastings and Turner 1965). As creosotebush densities increase, perennial grass densities decline (Anderson et al. 1957). Therefore, it is desirable to replace creosotebush with perennial grasses to reduce soil erosion, increase infiltration, and provide forage for domestic livestock. Jerry COY. and Howard Morton are range scientist and supervisory plant physiologist, respectively; USDA, Agricultural Research Services Aridland Watershed Management Research Unit, 2000 E. Allen Road, Tucson, Artz. 85719, Martha Martin-R. and Fernando Ibarra-F. are head of the Department of Range Management and Technical Director, respectively, CIPES, Periferico OTS S/N, Conjunto UGRS, Postal 1754, Hermosillo, Sonora, Mexico. When this study was initiated Martha Martin-R. and Fernando Ibarra-F. were graduate students, School of Renewable Natural Resources, University of Arizona, Tucson. Appreciation is extended to Consejo National de Ciencia y Tecnologia (Mexico) for financial support; Elanco Products Company for the herbicide and fencing materials at the Mexican sites; Drs. Luis Carlos Fierro, Thomas N. Johnsen, Jr., and Gilbert L. Jordan for technical assistance; personnel at Rancho Experimental La Campana, Chihuahua, Mexico, and Aridland Watershed Management Research Unit, Tucson, Aria., for setting up plots, applying treatments, and collecting data; and ranchers Eloy Morales, Sergio Mendora, and Gilbert0 Valdez for permission to use their land and housing facilities. The Rocky Mountain Forest and Range Experiment Station gave permission to use land at the Santa Rita Experimental Range. Lovegrass seeds were provided by U.S. Dep. Agr., Soil Conservation Service, Plant Materials Center, Tucson, Arizona. Kleingrass and sideoats grama seeds were provided by Rancho Experimental La Campana. Buffelgrass seeds were provided by Centro de Investigations Pecuarias de1 Estado Sonora, Garbo, Sonora, Mexico. Manuscript accepted 5 May 1986. 540 For the past 90 years creosotebush management has consisted of mechanical tillage to reduce creosotebush competition and prepare a seedbed for seeding perennial grasses (Cox et al. 1982). Mechanical tillage disturbs surface soils and aids in rainwater infiltration (Jordan 1981), but seedings at creosotebush site were seldom successful and the treated area is usually reinvaded by creosotebush or annual forbs and grasses (Cox et al. 1984a). Pelleted tebuthiuron [N-(5-(1,ldimethylethyl)-1,3,4-thiadiazol2-yl)-WWdimethylurea] effectively controls creosotebush (Jacoby et al. 1982) and perennial grasses can be established if grass seeds and pellets are applied at the same time (Baur et al. 1977). Grass seedlings, however, may not survive if pellets are applied after seeds germinate because seedling roots encounter the herbicide as it moves through the upper soil profile (Baur 1979). The semidesert grasslands of the southwestern U.S.A. and northern Mexico are of great importance to the livestock industry, but the chances of reestablishing forage grasses are low because of erratic precipitation in summer. Therefore, it is important to address the effects of precipitation on plant establishment, persistence, and forage production. More than 300 forb, grass, and shrub species have been sown at 400 locations in the southwestern U.S.A. and northern Mexico during the past 90 years (Cox et al. 1982). A successful seeding was more likely to occur if seed of the following species were sown prior to the summer rains: (1) ‘A-68’ Lehmann lovegrass (Eragrostis lehmanniana), (2) ‘A-84’ and (3) ‘Catalina’ Boer lovegrass (E. curvula var. conferta), (4) ‘Cochise’ Atherstone lovegrass (E. lehmanniana X E. trichophera), (5) ‘S-75’ Kleingrass (Panicum coloratum), (6) ‘Premier’sideoats grama (Bouteloua curtipendula), and (7) ‘common’ buffelgrass (Cenchrus ciliaris). Researchers have evaluated either the relationships between mechanical seedbed preparation and grass establishment or chemical seedbed preparations and grass establishment, but have not attempted to directly compare both seedbed preparations. The purpose of this study was to compare establishment potential and persistence of 7 perennial grasses sown in mechanically and chemically prepared seedbeds.

Since the first edition of this popular textbook appeared in 1984, the Charter of Rights and Freedoms has transformed the role of the courts in Canadian politics. The book introduces students to issues raised by the new political role of Canadian judges. Law, Politics and the Judicial Process in Canada features new introductions and new readings that deal with current issues in the realm of Canadian law and politics.

Various rates of tebuthiuron pellets were aerially applied on rangelands in the Southwest to determine effects on noxious shrubs. Creosotebush (Larrea tridentata) and tarbush (Flourensia cernua) shrubs were controlled with 0.4 and 0.3 kg active ingredient (a.i.)/ha, respectively, of tebuthiuron pellets. About 1.1 kg a.i./ha of tebuthiuron pellets controlled honey mesquite (Prosopis glandulosa) growing on loamy sands or sandy loams. About 0.6 and 0.5 kg a.i./ha of tebuthiuron pellets controlled whitethorn acacia (Acacia constricta) and desert zinnia (Zinnia pumila), resptctively. Higher rates of tebuthiuron are needed to control those shrubs on deep, fine textured soils than on shallow, coarse textured soils. Woody plants have rapidly invaded new areas in the Southwest (Buffington and Herbel 1965, York and Dick-Peddie 1969). Some woody plants are responsible for reduced forage production and have other adverse effects on livestock operations (Herbel et al. 1983). Dense stands have harmful effects on the environment because of accelerated wind or water erosion in arid areas (Gould 1982). It is estimated that mesquite (Prosopis spp. L.) occurs on 37.7 mil ha, creosotebush (Larrea tridentata [DC.] Cov.) on 18.8 mil ha, and tarbush (Flourensia cernua DC.) occurs on 5.4 mil ha in the U.S. (Platt 1959). Various methods have been used to reduce the density and distribution of these plants (e.g., Fisher et al. 1959, Herbel and Gould 1970, Martin 1975, and Scifres 1977). Tebuthiuron [N-(5{ 1, 1 -dimethylethyl]l,3,4-thiadiazol-2-yl)-N,N'-dimethylurea] is effective for chemical control of many woody plants. In Texas, it killed 80, 70, and 86%, respectively, of live oak (Quercus virginiana Mill.), whitebrush (Aloysia lycioides Cham.), and sand shinnery oak (Q. havardii Rydb.) at 1.1 kg active ingredient (a.i.)/ ha; and 45 and 60% of Macartney rose (Rosa bracteata Wendl.) and blackbrush acacia (Acacia rigidula Benth.), respecAuthors are range scientist, P.O. Box 3JER, Las Cruces, N. Mex. 88003; plant physiologist, Tucson, Ariz.; and range scientist. Las Cruces, Agr. Res. Serv. U.S. Dep. Agr. Cooperative investigations of Agr. Res. Serv., U.S. Dep. Agr., and N. Mex. Agr. Exp. Sta. Mention of trade names or proprietary products does not constitute endorsement by the USDA and does not imply its approval to the exclusion of other products that may be suitable. This paper is Journal Article No. 1066, Agr. Exp. Sta., N. Mex. State Univ.. Las Cruces 88003. Manuscript accepted February 1, 1985. tively, at 2.2 kg a.i./ha (Meyer and Bovey 1979, 1980a, and 1980b; and Jacoby and Meadors 1982). Meyer and Bovey (1979) reported 95, 50, and 85% of honey mesquite (Prosopis glandulosa Torr.) plants killed on a clay loam site in south central Texas with subsurface applications of the wettable powder of tebuthiuron at 9 kg a.i./ ha applied April 1973, April and December 1974, respectively. Jacoby et al. (1982) reported creosotebush kills of 86 and 91 % with applications of 0.5 and 0.7 kg a.i./ha of tebuthiuron on gravelly loams in the eastern portion of the Trans-Pecos area in Texas. Tarbush kills of 68 and 95% were obtained with the use of 0.5 and 0.8 kg a.i./ha of tebuthiuron on silty clay loams in the western part of the Edwards Plateau in Texas (Ueckert et al. 1982). Morton et al. (1978) reported that pelleted tebuthiuron treatments applied to a sandy loam soil in southern Arizona at rates of 0.56, 1.12, and 2.24 kg a.i./ha killed 77, 97, and 99% of creosotebush and 78, 100, and 1 00% of velvet mesquite (P. velutina Wooton) plants, respectively. This study determined effects of various rates of tebuthiuron on honey mesquite, cresotebush, tarbush, and other associated woody plants. Methods and Materials Six range areas werc treated with tebuthiuron in southern New Mexico and Arizona. A major part of the study was conducted on 2 sites on the Jornada Experimental Range, 35 km north of Las Cruces, N. Mex. Annual rainfall at the Jornada Headquarters averages 230 mm and the elevation is 1,260 m. One of the areas treated was a sandy range site dominated by mesquite. The soil is an Onite-Pintura complex (Bullock and Neher 1980). Onite is a coarse-loamy, mixed, thermic Typic Haplargid, and Pintura is a loamy, mixed, thermic Typic Torripsamment. The second treated area was a loamy range site dominated by creosotebush and tarbush. The soil is a Berino-Dona Ana association. They are both fine-loamy, mixed, thermic Typic Haplargids. Tebuthiuron pellets were aerially applied on 5-ha plots at various rates on each of the sites for 4 years, 1977-80 (see Tables I and 2 for actual rates). Applications were made in early summer each year. At treatment, mesquite leaves were mature and beans were ripening. Creosotebush was fruiting, while tarbush was in the leaf stage. Each plot was 62 X 800 m with an untreated area 12 m wide JOURNAL OF RANGE MANAGEMENT 38(5), September 1985 391 This content downloaded from 157.55.39.110 on Sat, 24 Sep 2016 05:51:42 UTC All use subject to http://about.jstor.org/terms Table 1. Mortality of honey mesquite 28 months after application of pelleted tebuthiuron on a sandy site on the Jornada Experimental

The rhythm of incubation in Mountain White-crowned Sparrows developed gradually during the egg laying period and a consistent pattern began with laying of the penultimate egg. Behaviors of incubating females were highly flexible and adaptable to conditions at the nest. During environmental fluctuations females partitioned their activity to provide adequate time for foraging while maintaining egg temperature (Tegg) within "normal" limits. Abilities of embryos to withstand low and oscillating temperatures allowed females to forage during the coldest hours of the day. Both air temperature (Ta) and exposure of the nest to direct sun influenced the daily rhythm of incubation activities. Mean duration of periods on and off the nest increased with increasing Ta. In some individuals, however, length of periods off decreased with increasing Ta, especially when nests were exposed to sun. Females remained on the nest at such times to prevent heating of embryos to lethal temperatures. There are indications that the onset and cessation of daily incubation activity is cued by photoperiod or light intensity.

A glassbouse study was conducted to dtttrmint how nonftrtillztd and ftrtlllztd solls collected ln crtoto~tbutb [Lunta Mdcntou (DC.) Cov.] communitlts would influence seedling ltaf gowtb and shoot production of Lebmann lovtgrass (Erugrostis Mmadana Nees) and blue pa&grass (Pdcum untidotde Ritz.). Soila were collected at 3 locations around creosottbusb plants: (1) at the crown base (Basal), (2) along tbt outer canopy tdgt (Drip), and (3) ln areas between plants (Open). Ltafltngtbs and shoot production were greatest on nonftrtillztd soils collected at the plant base, inttnntdiatt at the canopy edge, and least in open areas. Leaf lengths and shoot production significantly increased on ftrtilized solls collected in open areas.

NTEED for reliable information concerning the effects of environN5 ment on the response of plants to herbicides motivated the construction of the controlled environment system described herein. A unit suitable for such studies should have these general specifications: 1. a useful range of control of light, temperature, and relative humidity; 2. no recirculation of air, to avoid overall contamination of the unit by volatile herbicides; 3. capability of maintaining several sets of conditions simultaneously; and 4. a design which may be modified easily. The system described was constructed with these points in mind. A schematic diagram illustrates the major structural components of the environment system (Figure 1). Outside air enters the cooling

IT IS NECESSARY only to set down the title of this article, inevitably inviting comparison with Bisson's America's Far Eastern Policy' and Moore's Soviet Far Eastern Policy.2 to realize that Canada cannot properly be said to have a positive Far Eastern policy. This is not surprising, since the Canadian people and government have had other preoccupations in their task of creating a civilized community in the harsh northern half of North America. Their relations with the Pacific have been relatively few and tenuous. Yet not only has the twentieth century enabled Canada to develop the material structure of its civilization to near-maturity; the great wars of the century have enormously accelerated that development and forced a somewhat unprepared Canada to participate in world affairs. In consequence a Canadian Far Eastern policy must develop, and is, indeed, in the process of doing so. To understand present developments in Canadian policy in the Far East, one must keep in mind certain fundamentals of Canadian external policy which arise out of the history of the country and the present composition and interests of its people. In contrast with that of the United States, the history of Canada is distinguished by its traditional orientation towards Europe. Even the French-Canadian community, whose political ties with Europe were forcibly broken, has maintained religious and, to a lesser degree, cultural ties with Europe which may increasingly affect Canadian external policy. Of this European orientation the colonial bond was only one manifestation. The orientation arose, too, out of the nature of the Canadian economy, whose great export staples usually found their principal markets in Europe and, especially, the British Isles. The pattern was set in the colonial period by the conservative and counter-revolutionary character of the early Canadian immigrants, by fear of absorption by the United States in the era of Manifest Destiny, and by continued

mrHE technique used in the tests herein reported is based on the T inhibition of root elongation by growth substances, an exceedingly sensitive response. Two procedures are used in the application of the growth substances. The first consists of applying known amounts of test compounds to the root bathing solution of mesquite seedlings, and the second procedure consists of applying these compounds to the cotyledons. After addition of the growth regulator to the solution subsequent root inhibition is dependent on absorption by the root tissue and accumulation in an active form at the site of action. In cotyledonary applications, translocation as well as absorption is necessary before inhibition of root elongation will occur. It was the objective of this study to investigate various possibilities for using these procedures in herbicide absorption and translocation experiments. The use of root inhibition as a quantitative test for growth hormones was suggested by Lane (13) in 1936. The inhibition of Avena root elongation was employed by Bonner and Koepfli (5) in obtaining dosage response curves suitable for making quantitative estimates of indoleacetic acid (IAA). Thereafter, extensive use was made of this response in studying the action and activity of growth substances. Reviews by Aberg (1), Burstrom (6), and Torrey (18) summarize most of the root inhibition experiments, criticize the technique and discuss the significant findings. In most root inhibition experiments, the compounds have been added to the root bathing medium. However, IAA applications to stumps of shoots (17) and the endosperm (5) of Avena were found to retard root growth. On the other hand, similar applications to Pisum and Zea mays (17) failed to inhibit root development. Crafts (7) reported that measurements of root injury could not be obtained when small dosages of 2,4-D were applied to cotton leaves though large doses killed the roots. Van Overbeek (19) concludes that plant growth regulators are absorbed and translocated in the same manner as other organic compounds. Both direct and indirect evidence indicating the translocation of the intact molecule of phenoxy compounds has been presented by Crafts (7), Fang, et al. (9), Hay and Thimann (12), and many others. On the basis of their findings, it was assumed in the

Herbicides were applied by a truck-mounted sprayer and airplane to stands of mixed brush in East Texas. Mixtures of 2,4,5-T + picloram gave the best brush control. Picloram was the best individual chemical but failed to kill white ash (Fraxinus americana L.), saw greenbriar (Smilax bona-nox L.) and redbay (Persea borbonia (L.) Spreng.) Picoloram only partially controlled American holly (Ilex opaca Ait.), blackgum (Nyssa sylvatica Marsh.), flowering dogwood (Cornus florida L.), red maple (Acer rubrum L.), oaks (Quercus spp.), and yaupon (flex vomitoria Ait.). Dicamba, isocil, bromacil, and mixtures of 2,4,5-T had intermediate activity. Paraquat and diquat were least effective for killing woody species. Dense grass stands occurred within 2 years after treatment where the brush had been controlled.