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Prairie restorations are increasingly common throughout the central United States. However, we continue to have little information about which planted species become successfully established, or about the factors potentially limiting establishment. We used a combination of site surveys, field tests and germination testing to examine these issues. We surveyed thirty 4 to 6 y old Conservation Reserve Program (CRP) plantings to quantify the likelihood that planted native species can be found 4-6 y after planting. We then selected a subset of species that had been planted in the CRP sites for use in germination tests and field tests quantifying emergence and seedling survival. We found that nearly one third of the species planted in CRP sites failed to become established and that grasses were more likely to be successful than legumes or nonleguminous forbs. We also found that species with low establishment in the CRP sites often had low emergence rates in the field experiment and low germination rates in germination testing despite differences in seed origin and planting year. Our results suggest that germination may be a major limiting factor in the establishment of some tallgrass prairie species., INTRODUCTION Prairie restorations tend to have lower species richness, lower native forb densities and higher numbers of exotic species than remnant prairies (Sluis, 2002; Martin et al., 2005; McLachlan and [...]

Bison (Bos bison) were a keystone species in the tallgrass prairie region of the Great Plains of North America. Cattle (Bos taurus) have been described as a functional equivalent to bison and have replaced bison in most of the grassland that remains intact. However, non-grazing behaviors influence grassland dynamics and are dissimilar between bison and cattle. Wallowing behavior (a non-grazing behavior by bison, but not cattle) creates disturbances (wallows) that were a common feature (may have numbered more than 100 million) of tallgrass prairie prior to extirpation of bison and conversion of most land to row-crop agriculture. We hypothesized that wallows are a unique disturbance that significantly influence both the structure and function of tallgrass prairie. We examined the response of plants to wallowing disturbances on Konza Prairie Biological Station, Kansas, where a herd of approximately 200 bison had year-round access to 1000 ha of native tallgrass prairie. We determined the influence of this disturbance type on aboveground net primary production (ANPP), plant species richness and diversity, and plant life form richness and diversity. The ANPP at the edge of wallowing disturbances was double the production in wallows and in adjacent prairie, which were not different from year to year. Plant species richness and diversity were significantly lower in wallows than at the edge of wallows and in adjacent prairie during all years of the study. However, composition of species were dissimilar among locations (e.g., 16% of all plant species samples were found only in the wallows); and, therefore, wallows increased the local and likely regional diversity of plant species. Likewise, wallowing disturbances increased local richness and diversity of plant life forms. It appears that these once common wallowing disturbances increase the diversity of tallgrass prairie beyond that of prairie that is grazed only (i.e., prairie with cattle)., INTRODUCTION American bison (Bos bison) were a keystone species in the tallgrass prairie region of the Great Plains (Knapp et al., 1999); their impact on the ecosystem was disproportionately large [...]

Prairie junegrass [Koeleria macrantha (Ledeb.) Shultes] is a perennial, short-grass prairie species distributed throughout the Northern Hemisphere. This species demonstrates tolerance to many environmental stresses in Minnesota. Forty-eight K. macrantha accessions from the United States National Plant Germplasm System (NPGS) were grown under low-input conditions to evaluate turfgrass quality characteristics for use in a breeding program. A second objective was to identify key geographical locations for germplasm collection. The experiment was conducted at Becker and St. Paul, MN. Nineteen accessions at Becker and 30 accessions at St. Paul performed with an adequate turf quality rating of 5.0 or higher when averaged over the 3-yr study, suggesting the potential for use in low-input areas. Prairie junegrass from northern collection regions displayed the highest spring green-up ratings, an important turf trait in northern climates. There was a negative correlation between this trait and mowing quality at Becker (r = -0.44) and at St. Paul (r = -0.34). Several accessions had acceptable mowing quality and would be candidates for integration into a native prairie junegrass turfgrass breeding program. There was no correlation between inflorescence emergence and turf quality, or between inflorescence emergence and persistent straw suggesting that flowering does not necessarily affect turf quality ratings. Rust (unknown Puccinia species) was present at both locations. doi: 10.2135/cropsci2010.02.0068

Prairie junegrass [Koeleria macrantha (Ledeb.) Shult.] is a perennial, short-grass prairie species distributed throughout the northern hemisphere. This species is known to require fewer inputs than other cool-season turfgrasses and it demonstrates tolerance to many environmental stresses found in Minnesota. In June 2007, 48 K. macrantha accessions from the U.S. National Plant Germplasm System (NPGS) were grown and evaluated for seed production characteristics in 2 locations (St. Paul, MN, and Becker, MN). Significant variation was found among accessions for several seed production traits including harvest date, plant height, seedhead number, and seed yield. A significant correlation between seedhead number and seed yield was found, which can be utilized for indirect selection in the production nursery. Plant growth and seed yield were highest at the Becker location, demonstrating the species' preference for well-drained soils. Flowering times were significantly different between the locations; however, there were no significant differences in the duration from seedhead emergence to harvest between the locations. Multivariate analysis did not reveal clustering of accessions based on geographic origin, suggesting a diversity of material within collection regions. doi: 10.2135/cropsci2009.05.0235

Sericea lespedeza (Lespedeza cuneata [Dumont] G. Don) has shown allelopathic properties in tame pastures but no studies have been done on its allelochemical effects on grasses in eastern Kansas rangelands [...]

A six-year-old restored prairie plant community at Johnson County Community College (JCCC) was monitored for changes in species number and plant cover. It was hypothesized that haying would successfully establish [...]

Three tallgrass prairie plant species, two common perennial forbs (Artemisia ludoviciana and Aster ericoides [Asteraceae]) and a dominant [C.sub.4] perennial grass (Sorghastrum nutans) were studied under field and greenhouse conditions to evaluate interspecific variation in grazing tolerance (compensatory growth capacity). Adaptation to ungulate grazing was also assessed by comparing defoliation responses of plants from populations with a 25-yr history of no grazing or moderate ungulate grazing. Under field conditions, all three species showed significant reductions in shoot relative growth rates (RGR), biomass, and reproduction with defoliation. In the two forbs, clipping resulted in negative shoot RGR and reductions in both number and length of shoot branches per ramet. Sorghastrum nutans maintained positive RGR under defoliation due to a compensatory increase in leaf production. Defoliation reduced rhizome production in A. ericoides and S. nutans, but not in A. ludoviciana. Clipping significantly reduced sexual reproductive allocation in all three species, although S. nutans showed a smaller reduction than the forbs. All three species showed similar responses to defoliation in burned and unburned sites. Under greenhouse conditions, a similar clipping regimen resulted in smaller reductions in growth and reproduction than those observed in the field. For all three species, the grazing tolerance indices calculated under natural field conditions were significantly lower than those estimated from greenhouse-grown plants, and the interspecific patterns of grazing tolerance were different. Aster ericoides exhibited the highest overall defoliation tolerance under greenhouse conditions, followed by S. nutans. Artemisia ludoviciana, the only study species that is typically not grazed by ungulates in the field, showed the lowest grazing tolerance. In the field experiment S. nutans showed the highest grazing tolerance and the two forbs had similar low tolerance indices. These patterns indicate that, despite high compensatory growth potential, limited resource availability and competition in the field significantly reduce the degree of compensation and alter interspecific differences in grazing tolerance among prairie plants. In all three species, defoliation suppressed sexual reproduction more than growth or vegetative reproduction. Significant interactions between plant responses to defoliation and site of origin (historically grazed or ungrazed sites) for some response variables (root/shoot ratios, rhizome bud initiation, and reproductive allocation) indicated some degree of population differentiation and genetic adaptation in response to a relatively short history of ungulate grazing pressure. The results of this study indicate that patterns of grazing tolerance in tallgrass prairie are both genetically based and also environmentally dependent. Key words: Ambrosia ludoviciana; Aster ericoides; compensatory growth; forbs; grasses; grazing tolerance; Sorghastrum nutans; tallgrass prairie.

Prescribed burning recycles essential plant nutrients and stimulates growth in prairie restoration. While reducing the content of nutrients in dry matter, prescribed burning may also alter the spatial variability and distribution of nutrients, which in turn could negatively impact long-term productivity. A study was conducted in a tallgrass prairie restoration at the Audubon Society's Goose Pond Sanctuary near Arlington, Wisconsin to characterize the content and spatial variability and distribution of macro- (i.e., N, C, P, K, Ca, Mg and S) and micro-nutrients (i.e., Zn, B, Mn, Cu, Fe, Al and Na) in the aboveground litter before burning and in the ash after burning following 3- and 6-y burn intervals. Aboveground litter mass was significantly higher in 2001 after the 3-y burn interval than in 1998 after the 6-y burn interval. The amount of preburn litter was consistently reduced by >90% for both burn intervals, but the reduction of dry matter and the reductions in mass of N, C, P, K and S were significantly higher in 2001 than in 1998. The 6-y burn interval resulted in nutrient export that was similar to nutrient inputs from atmospheric wet deposition, whereas the 3-y burn interval resulted in the export of N, K, Ca and Mg faster than they were replenished. Prescribed burning significantly affected the spatial variability of dry matter and the concentration and content of most macro- and micronutrients. However, prescribed burning had little effect on the pre- and postburn spatial distributions of macro- and micro-nutrient masses, which were similar to pre- and postburn spatial distributions of litter and ash masses, except for Fe and Al which had atypically large concentration variances.

Many clonal plants consist of many connected individual ramets, allowing them to share water and nutrients via physiological integration. Integration among ramets may also improve the ability of clonal plants to tolerate abiotic stress-or improve the competitive ability of individual ramets. Here I use a field experiment to determine whether clonal integration improves ramet performance for a widespread clonal tree species invading into native prairie. Aspen (Populus tremuloides) dominates the southern treeline in western Canada, has long-lived belowground connections between mother and daughter ramets, and reproduces vegetatively via resprouting rhizomes after disturbance. I applied two competition treatments (neighbors present or absent) and two clonal integration treatments (belowground rhizomes between mother and daughter ramets either severed or left intact) to 12 replicate Populus daughter ramets at each of three sites. Neighbors improved the survivorship of Populus ramets by 25-35% after 2 yr, but decreased growth by ~20%. Clonal integration tended to improve ramet survival and growth, but these trends were often not significant. Clonal integration did not alter the effects of competition from neighboring vegetation, suggesting that connections between ramets do not necessarily improve the competitive ability of Populus invading into native prairie. Key words: clonal plant; competition; grassland; physiological integration; Populus tremuloides; prairie; tree-grass competition; tree invasion.

We examined the spatial genetic structure of Helianthus occidentalis Riddell ssp. occidentalis Riddell (western sunflower) to determine whether this species is highly clonal and whether the distance between prairie patches influences genetic differentiation. In the Edge of Appalachia Preserve System, Ohio, this species is restricted to prairie patches that have a clumped distribution in the forest matrix. Data from this insect-pollinated forb with gravity-dispersed seed were compared to data from the same patches for Asclepias verticillata, an insect-pollinated species with wind-dispersed seed. Allozyme electrophoresis was used to collect genetic data from H. occidentalis samples from eight patches in four regions. Genetic data from three polymorphic loci indicted that this species is not highly clonal. Genetic differentiation was greater among patches within a region than among regions, suggesting that gene flow among patches is more limited in H. occidentalis than in A. verticillata. Founder effect may also have contributed to observed genetic differences among patches as some of these populations may have re-established after release from human use. As habitat fragmentation is increasing in the preserve, it is also likely that genetic differentiation may be increasing. Therefore, monitoring of genetic structure is necessary to further assess the effect of fragmentation. Key words: allozymes; Asteraceae; clonal; gene flow; genetic diversity; genetic structure; habitat fragmentation; Helianthus occidentalis; prairie.

Many plant species contain populations with more than one polyploid cytotype, but little is known of the mechanisms maintaining several cytotypes in a population. Andropogon gerardii cytotypes were compared to evaluate different models of autopolyploid cytotype coexistence. The enneaploid (90 chromosome, 9x) cytotype was found to be larger and taller than the hexaploid (60 chromosome, 6x) cytotype. Seed production is significantly more efficient in hexaploids, but seed production per area was not significantly different. The two cytotypes are not exomorphologically separable in the field because of great plasticity in response to environmental variation and wide variation within each cytotype. These data suggest cytotypic variation is maintained by natural selection. Key words: Andropogon gerardii; cytotype; enneaploid; hexaploid; Poaceae; polyploidy.

Symbiotic associations between plants and arbuscular mycorrhizal fungi are ubiquitous and ecologically important in many grasslands. Differences in species responses to mycorrhizal colonization can have a significant influence on plant community structure. The growth responses of 36 species of warm- and cool-season tallgrass prairie grasses and 59 tallgrass prairie forbs to arbuscular mycorrhizal (AM) fungal colonization were assessed in greenhouse studies to examine the extent of interspecific variation in host-plant benefit from the symbiosis and patterns of mycorrhizal dependence among host plant life history (e.g., annual, perennial) and taxonomic (e.g., grass, forb, legume, nonlegume) groups and phenological guilds. There was a strong and significant relationship between phenology of prairie grasses and mycorrhizal responsiveness, however this relationship was less apparent in forbs. Perennial warm-season [C.sub.4] grasses and forbs generally benefited significantly from the mycorrhizal symbiosis, whereas biomass production of the cool-season [C.sub.3] grasses was not affected. The root systems of the cool-season grasses were also less highly colonized by the AM fungi, as compared to the warm-season grasses or forbs. Unlike the native perennials, annuals were generally not responsive to mycorrhizal colonization and were lower in percentage root colonization than the perennial species. Plant growth responsiveness and AM root colonization were positively correlated for the nonleguminous species, with this relationship being strongest for the cool-season grasses. In contrast, root colonization of prairie legumes showed a significant, but negative, relationship to mycorrhizal growth responsiveness. Key words: cool-season grass; forb; mycorrhizae; mycorrhizal responsiveness; phenology; tallgrass prairie; warm-season grass.

Genetic variation was analyzed in the endangered prairie forb Penstemon haydenii. Individuals from nine populations were surveyed for chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) variation. No cpDNA polymorphism was found. Analysis of mtDNA revealed variation within and among populations. A minimum of eight haplotypes were identified. The distribution of these genotypes suggests that there is some correlation between geographic and genetic distances, which reflects the minimal gene flow in this species. Key words: chloroplast DNA; endangered species; genetic diversity; mitochondrial DNA; Penstemon haydenii; restriction fragment length polymorphism (RFLP).

1 We studied the demographic viability of populations of a long-lived iteroparous prairie perennial, Silene regia, in relation to management regimes, population sizes, geographical region (Ohio and Indiana vs. Missouri and Arkansas), degree of isolation and amount of genetic variation. Demographic data were collected from 16 populations for up to 7 years. 2 This species has high survivorship, slow growth, frequent flowering and episodic seedling recruitment. Matrix projection methods were used to summarize population performance with and without recruitment. Median finite rates of increase by population varied from 0.57 to 1.82 and from 0.44 to 0.99, respectively. 3 Populations with the highest rates of increase had been burned. Six of eight populations, for which stochastic modelling predicted persistence for 1000 years, included fire in their management. None of the five populations with predicted 100-year extinction probabilities of 100% was managed for conservation or burned. An intermediate group of three populations with at least 10% probability of extinction between 100 and 1000 years was not managed, but was none the less kept open by mowing and herbicide application. 4 Analysis of composite elasticities showed that growth and fecundity terms were higher for growing (vs. declining) populations and that growth elasticity was higher in burned than unburned populations. Lack of burning shifts the elasticity spectrum from that typical of open habitat herbs (higher growth and fecundity elasticities) to values usually found for closed habitat herbs (higher survival elasticities). 5 In multivariate analyses predicting finite rates of increase (with and without recruitment), fire management and region were the strongest predictors, followed by genetic variation, population size, isolation and interactions of population size and fire, and region and fire. Populations with the highest rates of increase were burned, eastern, more genetically diverse, larger and less isolated. Discrimination of populations with different extinction risks (three classes) was related mainly to fire, genetic variation and region. 6 Most of these conclusions support conservation biology predictions that population viability will be highest in larger, less-isolated, more genetically diverse populations. However, management and geographic trends have overriding roles affecting demographic viability. Habitat fragmentation and genetic depletion have the potential to threaten residual prairie populations of S. regia, but lack of fire management appears to be the primary short-term threat. Keywords: elasticity, extinction probability, habitat management, population growth rate, population viability assessment

Large grazing mammals contribute to the species diversity of grasslands via direct and indirect effects of defoliation and urine deposition. We examined the influence of one and two applications of simulated bovine urine on vegetation structure on (1) tallgrass prairie burned either every 2 or 4 yr at Konza Prairie Research Natural Area (KPRNA), Kansas, and (2) unburned sandhills prairie at the Niobrara Valley Preserve, Nebraska. We also examined the influence of urine and the clipping of graminoids on an annually burned site at KPRNA. Plant abundance in general increased on urine patches but the response appeared dependent on litter accumulation. [C.sub.4] grasses increased at the annual burn and Niobrara sites where litter levels were low. [C.sub.3] forbs increased at the 2- and 4-yr burn sites where litter levels were high. Urine treatment significantly affected community composition at all but the 2-yr burn site. Alpha-diversity decreased on urine patches at the annual and 4-yr burn sites but increased on urine patches at the Niobrara site. Beta-diversity increased on urine patches at the annual burn and Niobrara site but decreased on urine patches at the 4-yr burn site. The clipping of graminoids at the annual burn site reduced both [Alpha]- and Β-diversity and graminoid abundance while forb abundance was not affected. Key words: [Alpha]-diversity; Β-diversity; clipping; nitrogen; sandhills prairie; simulated bovine urine; tallgrass prairie., INTRODUCTION Grassland vegetation is spatially and temporally variable (Weins 1976, Collins 1992, Glenn and Collins 1992, Seastedt and Knapp 1993). This variability or 'patchiness' may result from several factors including [...]

Previous research in tallgrass prairie in Kansas indicated that warm-season, [C.sub.4], grasses are obligate mycotrophs and do not grow normally in the absence of mycorrhizal symbiosis. However, the degree to which such grasses depend on mycorrhizae in other prairie soils has not been examined. Growth and mycorrhizal colonization of roots of Andropogon gerardii and Schizachyrium scoparium were compared in soil collected from Konza Prairie Research Natural Area (KPRNA), Riley County, Kansas and from Sand Ridge State Forest (SRSF), Mason County, Illinois. Plants of both species were grown in the two soils and were inoculated with Glomus etunicatum spores originally collected from KPRNA or colonized root pieces from S. scoparium plants collected from SRSE Glomus etunicatum inoculum resulted in significantly greater root colonization and biomass of both plant species in steamed KPRNA soil than did root piece inoculum. There was no benefit from inoculation in non-sterile soil which contained indigenous mycorrhizal fungi. In SRSF soil, there was no response to inoculation with mycorrhizal fungi from either source. The lack of mycorrhizal response in SRSF soil is attributed to the greater plant-available P level of this soil. For S. scoparium grown in SRSF soil, plants grown in steamed soil produced more biomass than plants grown in steamed soil amended with nonsterile soil sievings (containing soil organisms other than mycorrhizal fungi), or in nonsterile soil. These differences could be due to competition for inorganic nutrients between soil microbes and the plant or antagonistic relationships between the plant or the mycorrhizal association and the soil microbes. Thus, the mycorrhizal dependence of these plant species is related to both soil and inoculum type or species.

We used a field-based, prescribed-watering, 4-treatment experiment to examine the response of smooth brome (Bromus inermis Leyss.) to a late spring burn in a tallgrass prairie remnant under conditions of varying soil moisture. Smooth brome decreased 17.0% + or - 3.9 SE in the burned, high-water treatment, decreased 8.2% + or - 3.1 in the burned, low-water treatment, increased 10.5% + or - 2.9 in the unburned, high-water treatment, and increased 11.7% + or - 4.2 in the unburned, low-water treatment. The decreases in the two burned treatments were significantly different but the increases in the unburned treatments were not. Smooth brome decreases in the high-water, burned treatments and increases in the low-water, unburned treatments were significantly larger in plots with smaller initial smooth brome biomass. We discuss several implications of this study for management of natural areas to control smooth brome.

Clones of the perennial grass Panicum virgatum were studied on the Konza Prairie in northeast Kansas to determine the effects of neighbors, nutrient availability, and physiological integration on ramet population dynamics and clonal growth and architecture. Opposite halves of established clones in the field were subjected differentially to treatments including neighbor removal and nitrogen addition, with intact or severed rhizome connections between halves. Neighborhood competition strongly influenced clone architecture and expansion rates. Removal of neighbors resulted in a >95% increase in radial clone expansion, intraclonal ramet densities, ramet population growth rates, ramet biomass, and percent of stems flowering, averaged over a 4-year period relative to halves or clones with intact competitors. Plant responses suggest that effects of interclonal neighbors are mediated through alteration of the light environment in the clone canopy and water availability. Addition of nitrogen did not affect lateral spread or clone structure, but resulted in significant increases in ramet size, flowering, and seed production. ANOVA revealed no significant effect of rhizome severing or treatment x severing interactions, suggesting that the size of the integrated physiological unit is much smaller than clone size and/or that physiological integration had no effect on clone responses to environmental heterogeneity at the scale of the diameter of established clones.

Spring burns were conducted at four day intervals from 6 April through 20 May 1988 on a reestablished tallgrass prairie in eastern Nebraska. Growth and flowering responses of big bluestem (Andropogon gerardii Vitman) were measured during October. Flowering stem height and flowering stem number increased significantly (P < 0.05) on areas burned on each of two, successive four-day intervals after 12 May. Plants on areas treated before 12 May showed no such response. The closely timed, but significantly different, responses emphasize the importance of careful attention to specific time of burning and associated plant growth status. This is particularly relevant when interpreting the effects on such broadly defined treatments as 'Spring burn.' Further, this study suggests that there may be some activity, either environmental or physiological, that changes dramatically over as few as four days and that significantly affects big bluestem.

To assess changes in herbaceous species cover due to woody plant invasion, plant species composition was determined at different locations under and adjacent to isolated 10 to 22-yr-old eastern red cedar (Juniperus virginiana L.) trees situated in an eastern Nebraska native bluestem prairie. Little bluestem (Andropogon scoparius Michx.) dominated plots without trees (44% cover); Kentucky bluegrass (Poa pratensis L.), a nonnative species, dominated under trees (19% cover). This difference in dominant species represents a 20-yr change in herbaceous composition that occurred following establishment and growth of tree crowns over native prairie. In addition to little bluestem, 11 other common species (frequency > 10%) declined under persistent tree cover including big bluestem (Andropogon gerardii Vitman; -10%) and white aster (Aster ericoides L.; -5%). However, Kentucky bluegrass and carex (Carex spp.) cover increased 13% and 10%, respectively. No consistent correlation was found between photosynthetic pathway (C3 or C4) and species response to tree cover. Direction from the main tree stem was a significant factor affecting the response of 4 of 13 common species to tree crown development; percent cover of these species generally was lower to the N and E than to the W and S. Tree size significantly affected the response of 5 of 13 species. The data indicate that bluestem prairie species composition can be significantly affected by less than 20 yr of shading by invading trees, suggesting that protection from such invasion is essential to the continuation of this ecosystem.

We examined the effect of leaf rolling on [CO.sub.2] and water vapor exchange of two [C.sub.4] prairie grasses with contrasting patterns of leaf rolling. Andropogon gerardii (big bluestem) is a drought-resistant species with predominantly hypostomatal leaves that fold (adaxial surface inward) in response to low leaf water potential, while leaves of Spartina pectinata (prairie cordgrass), a mesic species, are epistomatal and roll into spirals (also adaxial surface inward). Adaxial stomata of both in completely rolled or folded leaves; thus these leaf movements have a minor effect on total leaf conductance. Energy budget calculations indicate that leaf rolling reduces transpiration by 7%-13% in water-stressed plants by lowering leaf temperature and, therefore, leaf-to-air vapor pressure deficit. This reduction is small relative to the direct effect of stomatal closure on transpiration. However, small decreases in transpiration, leaf temperature, and incident irradiance associated with leaf rolling may decrease the potential for photoinhibition, prolong physiological activity, and increase survival during drought.

Ecophysiological responses to drought and a 3-cm rain were measured in seven [C.sub.3] forb and five [C.sub.4] grass species on a tallgrass prairie in northeastern Kansas. In general, midday leaf water potentials and conductances increased after rain to a greater extent in the [C.sub.3] forbs, although exceptions occurred. In particular, the deeply rooted Silphium laciniatum showed little or no change in water potential and three of the five grass species exhibited no change in conductance. Although the above differences in species and life-form responses were noted, few of the species exhibited signs of severe stress at the height of the drought, emphasizing the degree to which both [C.sub.3] forbs and [C.sub.4] grasses are adapted to occasional severe droughts in the prairies of North America.

Little is known of the lifespans of herbaceous plants, especially in grasslands, although this information is basic to understanding the dynamics of species and ecosystems. Permanently marked plants of the bush morning glory, Ipomoea leptophylla (Convolvulaceae), in Nebraska sandhills prairie were censused annually from 1979-1989. While the average annual death rate was 2.6 per 100, virtually all the mortality was among smaller and probably younger plants. Recruitment varied greatly among years. Of plants of known age, the median age at first flowering was 6 yr. After 9 yr 30% had never flowered. Larger size classes flowered more frequently than smaller mature plants and were more likely to mature seeds successfully. For this polycarpic nonrhizomatous herb, a generation is probably over 2 decades and some plants may live more than a century. As a result, environmental variation on the scale of even the Great Drought may be a passing interval of minor impact on lifetime fecundity for established adults, although until extreme years have been observed this cannot be proven.

1 The distribution of different plant growth-forms may be caused by interactions among plants. Previous studies show that prairie and forest vegetation have different competitive effects and also influence both resource availability and soil community structure. 2 I used a field experiment to distinguish between short-term competitive effects and the long-term effects of vegetation on soils. Soil cores were reciprocally transplanted between prairie and forest sites. Seedlings of a grass (Bouteloua gracilis) and a shrub (Elaeagnus commutata) were planted into these cores and grown with or without neighbours. 3 Soil origin did not significantly alter the survival, growth or responses to competition of either transplant species. Bouteloua and Elaeagnus growth was suppressed by neighbours to about the same extent in prairie, but only Bouteloua growth was suppressed in forest, resulting in a significant interaction between environment and competition. All except one of the interactions involving soil origin were not significant, suggesting that plant-soil feedbacks did not modify the effects of competition or environment. 4 The results suggest that environment and competition have much larger influences on the performance of juvenile plants in the field than does soil origin. Further work is needed to determine the relative importance of resource competition and soil community effects on plant performance among species and study systems. Key-words: Bouteloua gracilis, competition, Elaeagnus commutata, forest, grass, growth, indirect effects, plant-soil feedback, prairie, reciprocal transplant experiment, shrub Journal of Ecology (2001) 89, 176-185

Silvery bladderpod (Lesquerella ludoviciana) is an endangered plant in Illinois where plants are at the eastern edge of their geographic range, occurring in blowout areas of recovering sand prairies at the Henry Allan Gleason Nature Preserve. Little is known about its reproductive potential in these areas. The objective of this study was to characterize population size, production of reproductive structures, and viability of seeds. In June 1999, three populations were identified within the Preserve. For each population, plants with and without fruits (no flowers present) were counted, and population areas were determined. Seedstalks/plant, fruits/seedstalk, and seeds/fruit were counted. Seeds were germinated on filter paper in Petri dishes at 25C. The three populations varied in size from 275 to 2050 m2 with a total area of nearly 3000 m2. Plant numbers were 900, 225, and 10,300 in the smallest, intermediate, and largest areas, respectively. The percentage of reproductive plants was lowest (28%) in the largest area and highest (88%) in the smallest area. Reproductive plants produced 6.5 seedstalks/plant (from 1 to 20). An average of 17.3 fruits/seedstalk (from 0 to 43) and 2.4 seeds/fruit (from 0 to 7) were produced. On seedstalks, seeds matured first on the lower part and last on the upper part. Total seed production for all three populations was estimated at nearly 1,200,000 seeds. Seeds germinated without any treatments to break dormancy. In summary, reproductive potential does not appear to be limited by seed production or by seed viability. Rather, reproductive potential in silvery bladderpod must be limited by other factors.

Brittany Card and A. Darlene Panvini. Belmont University Nashville, Tennessee. The distribution and architecture of exotic and native shrubs were examined along a prairie-forest transition in Beaver Dam state Park [...]

We present a biophysically based, one-dimensional hydrology/radiobrightness (1dH/R) model for prairie grassland that is subject to solar heating, radiant heating and cooling, precipitation, and sensible and latent heat exchanges with the atmosphere. The 1dH/R model consists of two modules, a one-dimensional hydrology (1dH) module that estimates the temperature and moisture profiles of the soil and the canopy and microwave emission module that predicts radiobrightness (R). We validate the 1dH/R model by comparing its predictions with data from a field experiment. The model was forced by meteorological and sky radiance data from our Radiobrightness Energy Balance Experiment (REBEX-1) on prairie grassland near Sioux Falls, SD, during the fall and winter of 1992-1993. Model predictions were compared with 995 consecutive REBEX-1 observations over a 14-day period in October. Average errors (predicted-measured) for canopy temperature are 1.1 K with a variance of 3.72 [K.sup.2], for soil temperatures at 2-, 4-, 8-, 16-, 32-, and 64-cm depths are 2 K with a variance of 4 [K.sup.2], and for H-polarized brightnesses are 0.06 K with a variance of 1.30 [K.sup.2] at 19 GHz and 6.01 K with a variance of 6.04 [K.sup.2] at 37 GHz. The model overestimates the 37.GHz brightness because we have not included scatter darkening within the vegetation canopy in the model. We use the 1dH/R model to simulate a 60-day dry-down of prairie grassland in summer. For grass with a column density of 3.7 kg/[m.sup.2] and soil with an initially uniform moisture content of 38% by volume, the upper 5 mm of soil dries to 27% by the end of the simulation. The corresponding L-band brightness increases from an initial 143 K to a final 163 K. In contrast, none of the special sensor microwave/imager (SSM/I) radiobrightnesses nor the radiobrightness thermal inertia (RTI) technique, either at L-band or at any SSM/I frequency, exhibits significant sensitivity to the soil dry-down.