Prairie Forbs Research Articles

Can the past predict the future? Experimental tests of historically based population models

A frequently advocated approach for forecasting the population-level impacts of climate change is to project models based on historical, observational relationships between climate and demographic rates. Despite the potential pitfalls of this approach, few historically based population models have been experimentally validated. We conducted a precipitation manipulation experiment to test population models fit to observational data collected from the 1930s to the 1970s for six prairie forb species. We used the historical population models to predict experimental responses to the precipitation manipulations, and compared these predictions to ones generated by a statistical model fit directly to the experimental data. For three species, a sensitivity analysis of the effects of precipitation and grass cover on forb population growth showed consistent results for the historical population models and the contemporary statistical models. Furthermore, the historical population models predicted population growth rates in the experimental plots as well or better than the statistical models, ignoring variation explained by spatial random effects and local density-dependence. However, for the remaining three species, the sensitivity analyses showed that the historical and statistical models predicted opposite effects of precipitation on population growth, and the historical models were very poor predictors of experimental responses. For these species, historical observations were not well replicated in space, and for two of them the historical precipitation-demography correlations were weak. Our results highlight the strengths and weaknesses of observational and experimental approaches, and increase our confidence in extrapolating historical relationships to predict population responses to climate change, at least when the historical correlations are strong and based on well-replicated observations.

Effect of Aminopyralid on Desirable Forb Species

AbstractNative forbs are important for plant community function and diversity, and provide food and cover for wildlife. Field studies have been conducted throughout the western United States to determine the impact of herbicides applied to control invasive weeds on native forbs. However, locating adequate populations of native forbs for evaluation of tolerance to herbicides is often difficult. The susceptibility of nine native prairie forbs to aminopyralid applied at 30 to 120 g ha−1 was evaluated in a greenhouse study and results compared to the same or similar species in field trials. Forb susceptibility to aminopyralid varied by species. Of the forbs evaluated, azure aster, purple coneflower, and closed bottle gentian were the most tolerant to aminopyralid while prairie coneflower, great blue lobelia, harebell, and white prairie clover were the most susceptible and likely would be killed in the field. Blanket flower and showy goldenrod were moderately tolerant to aminopyralid even when applied at 120 g ha−1. The susceptibility of greenhouse-grown forbs to aminopyralid was comparable to results for the same or similar species in the field. Results from greenhouse trials could be used to predict native forb tolerance in the field.

Fire season and prairie forb richness in a 21-y experiment

An experimental restoration in Wisconsin planted in 1986 tested the hypothesis that growing-season fire maintained richness of native herbaceous dicots (forbs). Replicated plantings were burned in May or July, or left unburned, every third year from 1989 to 2004 and monitored for differences in cover and richness through 2006. Native forb richness was higher in burned than unburned plots, with greatest richness following July burns. Two seasons after the 2004 fires, counts averaged 2 more native forb species in replicates burned in July than those burned in May and 4 more species in replicates burned in July than those left unburned. The strongest statistical response to fire season was higher richness of early-flowering species in replicates burned in July, largely attributable to early-flowering forbs planted in 1986 that persisted better after July burns than in other treatments. Spring fire increased cover of late-flowering C4 grasses. As of 2006, C4 grasses accounted for 76% cover after May fires, 52% after July fires, and 39% in unburned plots. Replicates burned in July held more alien species for the first 12 y, after which alien richness declined and differences among treatments disappeared. Summer fire best maintained richness of native, especially early-flowering, species.

Canopy cover and groundlayer vegetation dynamics in a fire managed eastern sand savanna

Savanna vegetation is characterized by high and variable ground layer species richness regulated by functional group interactions with fire regimes and canopy cover. Frequent fire selects for C4 grasses and prairie forbs in canopy openings and C3 graminoid species and shade-adapted forbs and shrubs in canopy shade. Frequent fire also maximizes heterogeneity in partial canopy cover and species richness across the full canopy gradient. However, few studies have linked fire induced change in tree canopy cover with groundlayer vegetation dynamics in relation to this model. In 1986 and in 2007, we measured canopy cover and sampled groundlayer vegetation in 1 m 2 plots along 53 transects at the Tefft Savanna, a fire managed 197 ha eastern sand savanna with strong canopy cover and elevation gradients. We analyzed temporal change in canopy cover and groundlayer vegetation, correlating percent change in canopy cover with change in ground layer functional groups. After 20 years of burning at 3 fires/decade, elevation accounted for 62% of the variation in an NMS ordination of groundlayer vegetation. However, canopy cover, which averaged 24–86% in 2007, had a significant secondary effect on the ordination. Five vegetation types classified by TWINSPAN varied significantly in elevation and canopy cover. Woody vegetation comprised 8 of the 12 species with greatest niche breadths, and tended to predominant in woodland or forest, where tree cover averaged 50% or more. Forbs had greater richness in savanna, which averaged less than 30% canopy cover. The C3 sedge Carex pensylvanica was the dominant graminoid species under woodland canopy cover, and was co-dominant with the C4 grasses Andropogon scoparius and Sorghastrum nutans under savanna canopy cover. As in other savannas, N-fixing species sorted across shade and canopy openings, and heterogeneity among transects was maximized at mid-canopy cover. Over time, canopy cover decreased up to 50%, creating more open savanna conditions at mid to high elevations. This decrease was associated with a 20–100 % increase in species richness and was significantly correlated with increasing richness and cover of C4 grasses and summer flowering prairie and woodland forbs. These results support a canopy cover model of fire-maintained savanna vegetation, with greater abundance of C4 grasses and prairie forb species associated with lower canopy cover, greater heterogeneity at mid-canopy cover, and species richness maximized across the light gradient. They also indicate that decreasing canopy cover caused by repeated burning increases species richness and abundance of C4 and prairie forb species.

Slug grazing effects on seedling and adult life stages of North American Prairie plants used in designed urban landscapes

Designed vegetation is a major contributor to ecosystem service provision in cities, and as such the study of how herbivory and other ecological factors determine its capacity to deliver such services, is long overdue. This study investigated the effect of slug grazing on the establishment and development of 26 species of North American prairie forbs and grasses used in sown or planted naturalistic communities in urban greenspace. The experiment was designed to provide slugs with the opportunity to choose between the plant species used, to mirror the situation that prevails in public greenspace. Slug density was manipulated through baiting with metaldehyde at different frequencies. Seedlings of prairie species were more palatable to slugs than adults. Seedling establishment was significantly reduced in most species by slug grazing, with only seven species showing no significant increase in establishment in response to baiting with metaldehyde. In many species successful establishment was based on moderate-high unpalatability and large or fast growing seedlings. Adult prairie plants were typically more able to withstand slug damage, and once their shoots reached a certain size, grazing declined. This was not true of the most palatable species, which even as adults were eventually eliminated by grazing in the absence of baiting. Phenology plays an important role in the survival of adults, with early emerging species potentially subject to severe damage due to the limited availability of alternate food plants. As a group, prairie forbs are typically palatable to slugs, and unlikely to be persistent in the most slug-rich urban situations.

Response of two prairie forbs to repeated vole herbivory

Vertebrate herbivores as diverse as ungulates, geese, and rabbits preferentially feed on plants that have previously experienced herbivory. Here, we ask whether smaller grassland "cryptic consumers" such as voles (Microtus ochrogaster and M. pennsylvanicus) preferentially clip (cut stems for access to leaves or seeds) or avoid previously clipped individuals of two tallgrass prairie species (Desmanthus illinoensis and Echinacea purpurea) within a growing season. Further, we ask how these plants respond to repeated clipping within a growing season, and whether the effects of this herbivory last into the subsequent growing season. Voles preferentially clipped stems of D. illinoensis and E. purpurea plants that had been previously clipped. The exception was indiscriminant clipping of stems of E. purpurea late in the growing season when its achenes, a favorite vole food, ripened. For D. illinoensis, repeated clipping resulted in a 59% reduction in biomass, 42% lower ratio of reproductive to vegetative biomass, and 57% fewer seeds produced per plant compared with unclipped plants. These effects lasted into the following growing season in which plants were protected from voles. In contrast, the only effect of repeated clipping for E. purpurea was that the number of achenes per plant was substantially reduced by three episodes of clipping. This effect did not carry over to the next growing season. Such differences in D. illinoensis and E. purpurea response to repeated stem clipping by voles offer insights into how these small rodents can effect major changes in composition and dominance in grassland communities.

Can life‐history traits predict the response of forb populations to changes in climate variability?

Summary 1. Climate change will cause changes in average temperature and precipitation as well as increased fluctuations around the mean, yet few studies have considered the impacts of altered climate variability on plant populations. We tested whether life‐history traits (expected life span, generation time and seed size) can predict plant responses to increased environmental variability across similar plant species sharing the same habitat. 2. We combined long‐term demographic data on 10 prairie forb species with stochastic demography techniques to estimate the effects of potential changes in matrix element means and variances on the long‐term stochastic population growth rate. 3. For all 10 species, recruitment had higher contribution and elasticity values than survival, meaning that climate change is more likely to influence population growth through effects on recruitment than on survival for these relatively short‐lived forbs. Species with longer generation times had lower elasticities to increases in matrix element variability. 4. Synthesis. Our analysis of a unique, long‐term data set suggests that longer‐lived plant species will be less vulnerable to the effects of future increases in climate variability. While this relationship was previously reported for diverse taxa from many locations, our results show that it also applies within a guild of short‐lived species from a single community. The generality of the pattern demonstrates the potential for using life‐history traits to make predictions about which species may be the most vulnerable to climate change.

Reproduction of Amorpha canescens (Fabaceae) and diversity of its bee community in a fragmented landscape

Loss of insect pollinators due to habitat fragmentation often results in negative effects on plant reproduction, but few studies have simultaneously examined variation in the bee community, site characteristics and plant community characteristics to evaluate their relative effects on plant reproduction in a fragmented habitat. We examined the reproduction of a common tallgrass prairie forb, Amorpha canescens (Fabaceae), in large (>40 ha) and small (<2 ha) prairie remnants in Iowa and Minnesota in relation to the diversity and abundance of its bee visitors, plant population size, and species density of the forb flowering community. We found significant positive effects of the diversity of bees visiting A. canescens on percent fruit set at a site in both years of the study and in 2002 an additional significant positive effect of plant species density. Abundance of bees visiting A. canescens had a significant positive effect on percent fruit set in 2002, but was only marginally significant in 2003. In 2003 but not 2002, the plant species density at the sites had a significant negative effect on the diversity and abundance of bees visiting A. canescens, indicating community-level characteristics can influence the bee community visiting any one species. Site size, a common predictor of plant reproduction in fragmented habitats did not contribute to any models of fruit set and was only marginally related to bee diversity one year. Andrena quintilis, one of the three oligolectic bee species associated with A. canescens, was abundant at all sites, suggesting it has not been significantly affected by fragmentation. Our results show that the diversity of bees visiting A. canescens is important for maintaining fruit set and that bee visitation is still sufficient for at least some fruit set in all populations, suggesting these small remnants act as floral resource oases for bees in landscapes often dominated by agriculture.

Prairie forb response to timing of vole herbivory

The timing of herbivory can be an important factor in the strength and direction of plant response to herbivore damage. To determine the effect of vole herbivory timing within a growing season on tallgrass prairie forbs, we used individual plant enclosures to limit vole access to three species, Desmanthus illinoensis, Echinacea purpurea, and Heliopsis helianthoides, in an experimental restoration in northern Illinois, USA. As part of a long-term experiment, we implemented five vole access treatments in 2003: (1) vole access for the entire growing season, (2) early-season access, (3) mid-season access, (4) late-season access, and (5) no vole access. We protected all plants from herbivory in the following growing season (2004) to test whether the effects of herbivory in one growing season carried over to the next. We also tested how restoration planting design, including seeding time (June or December) and density (35 or 350 seeds/m2 of each species) affected patterns of herbivory and plant recovery. Vole access for the entire growing season was most detrimental for the growth and reproduction of all three species. In contrast, vole access for a portion of the growing season had different effects on the three species: Desmanthus growth and reproduction was negatively affected by early-season access, Echinacea reproductive output was reduced by late-season access, and Heliopsis was not affected by early-, mid-, or late-season vole access. Negative effects of continual vole access carried over to the following growing season for Desmanthus and Heliopsis, but not for Echinacea. Effects of herbivory did not carry over to the next season for Echinacea and Heliopsis when plants were accessible to voles for only part of the growing season. In contrast, Desmanthus plants exposed to early-season herbivory in one year continued to produce fewer seeds per plant after being protected from vole herbivory for a growing season. Planting density and planting season had mixed effects. Echinacea and Desmanthus were larger in plots planted in June, showing that restoration design continued to affect plant population dynamics seven years after seeding. However, there was no interaction between plant response to vole herbivory and restoration design.

Providing Native Plant Diversity to the Willamette Valley Ecoregion

Producing seeds of multiple Willamette Valley prairie forb species is challenging for a grower. Many species do not lend themselves to standard commercial seed production methods. This reality has driven us to find creative, efficient ways to produce seeds of some of the more challenging species. By sharing our results, Heritage Seedlings Inc hopes to provide restoration professionals and native seed buyers with information critical to planning projects and selecting materials.

Integration of invasion ecology theories into the analysis of designed plant communities: a case study in Southern Germany

Theories regarding the establishment and persistence of self-naturalising alien species can help in interpreting these processes in designed plant communities with their combination of exotic species and native plant communities. Thus, they may provide a theoretical basis for this kind of landscape design. A case study investigated the influence of plant community conditions (invasibility), species-specific traits (invasiveness), and gap diameter size on the establishment of selected North American prairie forbs in Central European horticultural meadows. Experimental sites were located in Freising, Bavaria. Introduced forbs included Aster laevis, Aster novae-angliae, Aster x salignus, and Aster x versicolor. Establishment success was measured as survival rate and total aboveground dry biomass. Invasibility of the investigated horticultural meadows was strongly related to resource availability, as most influences of plant community traits could ultimately be attributed to this factor. Leaf area and specific leaf area above canopy height of the resident meadow species appear to be the traits that best explained differences in establishment success of the Asters. Gap size influenced species performance mainly on the less productive site, again due to higher availability of resources in the larger gaps. These results are consistent with findings of studies on self-naturalising alien species. By applying this interdisciplinary approach, valuable insights in the functioning of designed plant communities could be gained. Horticultural meadows can be one important tool in designing the highly dynamic urban landscape. In choosing suitable sites, resource availability should be strongly considered.

Fire frequency and tree canopy structure influence plant species diversity in a forest-grassland ecotone

Disturbances and environmental heterogeneity are two factors thought to influence plant species diversity, but their effects are still poorly understood in many ecosystems. We surveyed understory vegetation and measured tree canopy cover on permanent plots spanning an experimental fire frequency gradient to test fire frequency and tree canopy effects on plant species richness and community heterogeneity within a mosaic of grassland, oak savanna, oak woodland, and forest communities. Species richness was assessed for all vascular plant species and for three plant functional groups: grasses, forbs, and woody plants. Understory species richness and community heterogeneity were maximized at biennial fire frequencies, consistent with predictions of the intermediate disturbance hypothesis. However, overstory tree species richness was highest in unburned units and declined with increasing fire frequency. Maximum species richness was observed in unburned units for woody species, with biennial fires for forbs, and with near-annual fires for grasses. Savannas and woodlands with intermediate and spatially variable tree canopy cover had greater species richness and community heterogeneity than old-field grasslands or closed-canopy forests. Functional group species richness was positively correlated with functional group cover. Our results suggest that annual to biennial fire frequencies prevent shrubs and trees from competitively excluding grasses and prairie forbs, while spatially variable shading from overstory trees reduces grass dominance and provides a wider range of habitat conditions. Hence, high species richness in savannas is due to both high sample point species richness and high community heterogeneity among sample points, which are maintained by intermediate fire frequencies and variable tree canopy cover.

Genetic diversity in isolated patches of the tallgrass prairie forb, Lithospermum canescens (Boraginaceae)1

Abstract Genetic diversity is not well understood for many species inhabiting isolated, fragmented systems. We evaluated genetic diversity for the mixed mating, native prairie forb, Lithospermum canescens (Michx) Lehm. (hoary puccoon), at an isolated tallgrass prairie site in southern Minnesota. Leaf tissue was collected from nearly all individuals inhabiting three disjunct patches and AFLP (amplified fragment length polymorphism) was performed on each individual. A high level of genetic diversity was maintained (Nei's Genetic Diversity, h = 0.31), and diversity was similar among the separate populations (HT = 0.31, HS = .30, GST = 0.03) based on 73 scoreable bands from five primer pairs. Lithospermum canescens has retained a considerable amount of diversity among the three patches despite existing in isolated patches; pollination by flying insects likely contributed to the genetic similarities among the patches. Our results suggest that seeds from any one patch could be used for restoration of ot...

Assessing grassland restoration success: relative roles of seed additions and native ungulate activities

Summary Grassland restorations often lack rare forb and grass species that are found in intact grasslands. The possible reasons for low diversity include seed limitation, microsite limitation and a combination of both. Native ungulates may create microsites for seedling establishment in tallgrass prairie restorations by grazing dominant species or through trampling activities, but this has never been tested in developing prairies. We experimentally tested for seed and microsite limitation in the largest tallgrass prairie restoration in the USA by adding rare forb and grass seeds in two trials inside and outside native ungulate exclosures. We measured seedling emergence because this stage is crucial in recruiting species into a community. We also measured light, water and standing crop biomass to test whether resource availability could help to explain seedling emergence rates. Ungulates increased light availability for each sampling time and also increased above‐ground net primary productivity (ANPP) during summer. Seedling emergence of rare prairie forbs and grasses was consistently greater when we added seeds. Seedling emergence was conditionally greater with a combination of seed additions and grazing, but grazing alone was unable to increase emergence. When ungulates increased seedling enhancement, the mechanism was partially associated with increased water and light availability. Exotic and cosmopolitan weed seedling emergence was not affected by grazing. Synthesis and applications. These results suggest that tallgrass prairie restorations are primarily seed limited and that grazing alone may not be able to increase seedling emergence of rare species without the addition of seeds. Therefore, adding seeds to grassland restorations may increase seedling emergence of rare species, and mimicking effects of grazing may increase emergence when seeds are added.

At the Tip of the Prairie Peninsula: Vegetation of Daughmer Savannah, Crawford County, Ohio

Daughmer Savannah, Crawford County, Ohio is the largest and best preserved remnant of the unplowed, deep soil prairies and savannahs that were present at the easternmost extension of the Prairie Peninsula prior to European settlement. Repeated surveys of plant species composition over three years were combined with quantitative community sampling of plants and soils during 1999 to produce a comprehensive ecological and botanical analysis of this 16 ha site. A total of 166 species representing 109 genera from 48 plant families were recorded. Approximately 30% of the graminoids and 20% of the forbs were species with strong prairie affinities. Three sedges listed by the Ohio Department of Natural Resources as threatened or endangered (Carex atherodes, C. bicknelli and C. sartwellii) were present. Detrended Correspondence Analysis identified six major community types within Daughmer Savannah: oak savannah dominated by Quercus macrocarpa, mesic prairie dominated by Andropogon gerardii, Schizachyrium scoparium and other prairie grasses and forbs, wet prairie dominated by Spartina pectinata or Calamagrostis canadensis depending on the area, sedge meadow dominated by a mixture of Carex atherodes and C. lacustris, bluejoint swales dominated by Calamagrostis canadensis and Muhlenbergia mexicana, and prairie pothole marsh dominated by emergent aquatic plants. Species composition and community delineations were similar to those developed for Wisconsin by Curtis in the 1950's. This site should be used as a model for restoration of diverse prairie landscapes in the region.

Effects of Soil Carbon Amendment on Nitrogen Availability and Plant Growth in an Experimental Tallgrass Prairie Restoration

Abstract Restoration of tallgrass prairie on former agricultural land is often impeded by failure to establish a diverse native species assemblage and by difficulties with nonprairie, exotic species. High levels of available soil nitrogen (N) on such sites may favor fast‐growing exotics at the expense of more slowly growing prairie species characteristic of low‐N soils. We tested whether reducing N availability through soil carbon (C) amendments could be a useful tool in facilitating successful tallgrass prairie restoration. We added 6 kg/m2 hardwood sawdust to experimental plots on an abandoned agricultural field in the Sandusky Plains of central Ohio, United States, increasing soil C by 67% in the upper 15 cm. This C amendment caused a 94% reduction in annual net N mineralization and a 27% increase in soil moisture but had no effect on total N or pH. Overall, plant mass after one growing season was reduced by 64% on amended compared with unamended soil, but this effect was less for prairie forbs (−34%) than for prairie grasses (−67%) or exotics (−62%). After the second growing season, only exotics responded significantly to the soil C amendment, with a 40% reduction in mass. The N concentration of green‐leaf tissue and of senescent leaf litter was also reduced by the soil C treatment in most cases. We conclude that soil C amendment imparts several immediate benefits for tallgrass prairie restoration––notably reduced N availability, slower plant growth, and lower competition from exotic species.

`Prairie Chief' Big Bluestem

While the use of prairie plants in midwestern landscapes is currently going through a resurgence (Smith and Smith, 1980; Wasowski, 2002), the concept is firmly rooted in the past. Wilhelm Miller (1915) wrote, “Every Illinois city should have in at least one park a ‘prairie border’–with the grasses, composites, and other flowers labeled.” Astute designers realized that native prairie species are often adapted to Midwestern soils, climate, and pests, which can reduce maintenance practices such as supplemental irrigation, fertilization, and pesticide use. The reduction in materials and labor resulting from landscaping with native plants over a 10-year period may be one-fifth the cost of conventional landscape plantings (Mariner et al., 1997). Horticultural selections of prairie forbs (e.g., Aster novae-angliae, Echinacea purpurea, Liatris spicata, and Rudbeckia hirta) are common. Conversely, other than switch grass (Panicum virgatum) and little bluestem (Schizachyrium scoparium), horticultural selections of native ornamental grasses are relatively uncommon; presently, most ornamental grasses planted in the Midwest are exotics, often from the genera Calamagrostis, Miscanthus, and Pennisetum. Native grasses in the genus Andropogon (the bluestems), particularly A. gerardii, deserve more landscape attention. Greenlee (1992) noted that named cultivars of Andropogon would soon be introduced into the U.S. landscape trade due to their heights and foliage colors. Andropogon gerardii Vitman, big bluestem or turkey-foot, has been shown to be particularly diverse morphologically, ecologically, cytologically, and genetically (Barnes 1985, 1986; Gustafson et al., 1999; Keeler and Davis, 1999; Keeler et al., 2002; Wipff, 1996), all indicative of high potential for horticultural selection. Andropogon is a large genus of ≈100 species, comprised of perennial grasses found in temperate and tropical climates (Mabberley, 1997; Watson and Dallwitz, 1994). Members of the genus are commonly referred to as bluestems or beardgrasses; the name bluestem describes the bluish bloom on stems of some species within the genus (Mosher, 1918). The term beardgrass is a literal interpretation of the genus name Andropogon, which was derived from the Greek andro (man) and pogon (beard). This name is in reference to the hairy rachis and pedicels of sterile spikelets (Fernald, 1950). The specific epithet, gerardii, honors the French botanist, Louis Gerard, who informally described the species from plants cultivated in Provence (Fernald, 1950). Members of the genus Andropogon are quite common in much of the U.S.; there are 15 species in the continental U.S. (Kartesz and Meacham, 1999). Big bluestem (Andropogon gerardii), a primary component of the tallgrass prairie, is typically found in mesic areas, but can also occur in xeric or wet prairies (Ladd, 1995; Stubbendieck et al., 1997). Big bluestem is found from Quebec and Maine to Saskatchewan and Montana, south to Florida, Wyoming, Utah, and Arizona and also in Mexico and Honduras (Fernald, 1950; Hitchcock 1950; Kartesz and Meacham, 1999). Big bluestem is highly regarded as a livestock forage crop (Stubbendieck, 1997). Selections have been made for forage production as well as range and pasture plantings. For example, A. gerardii ‘Niagara’ is used for warm season forage production, re-vegetating droughty sites, and wildlife habitat improvement (Alderson and Sharp, 1995). Unique characteristics of ‘Niagara’ include a wide flag leaf, rapid regrowth in late summer and early fall, and some resistance to leaf spot (Alderson and Sharp, 1995). Other varieties such as ‘Kaw’ and ‘Pawnee’ (Reg. No. 1) are also used for range and pasture plantings. ‘Kaw’ displays uniform distribution of leaves, some resistance to rust, relatively high seed yields. ‘Pawnee’ produces good forage yields in Nebraska; seed quality and seed yields in cultivated rows and under irrigation are superior to common strains (Alderson and Sharp, 1995). In landscapes, Andropogon gerardii has traditionally been relegated to naturalized plantings such as prairie restoration, but can also be used as a background plant or screen (Greenlee, 1992). Its height (typically 1.5 to 2.4 m), upright growth habit, and orange to copper-red fall color identify it as a potential landscape plant (Darke, 1999). Cultivars of big bluestem have rarely been selected for ornamental planting. Exceptions are ‘Sentinel’ and ‘Champ’. ‘Sentinel’ (Limerock Ornamental Grasses, Inc., Port Matilida, Pa.) is similar in height, floral morphology, and cultural and propagation requirements to the species. Its narrow, columnar growth habit and burgundy tinted with yellow and orange suffused with blue fall color distinguish it from other big bluestems (Norm Hooven, Limerock Ornamental Grasses, Inc., personal communication). ‘Champ’ was originally selected as a forage type (Alderson, and Sharp, 1995; Newell, 1968), but Greenlee (1992) includes it with ornamental grasses due to its fall color and tolerance to sandy growing sites. Herein, another A. gerardii cultivar, ‘Prairie Chief’, is being introduced for landscape planting. It displays an upright habit that is slightly more open than ‘Sentinel’, and red, purple, and orange fall color. Furthermore, based on its habit and height, ‘Prairie Chief’ provides a native replacement for several exotic grasses

Establishing North American prairie vegetation in urban parks in northern England: Part 1. Effect of sowing season, sowing rate and soil type

This study investigated the establishment of 17 species of North American prairie forbs and grasses by field sowing in Sheffield, a city in northern England. The purpose of the work was to see whether it was feasible to use this sown, naturalistic plant community as a more sustainable alternative to traditional herbaceous plantings in urban parks. Key variables in the study were, sowing season (summer and winter), soil type (topsoil, subsoil, and sand mulched topsoil) and sowing rate (0.625, 1.25, and 2.5 g/m 2). All experimental plots were baited with metaldehyde containing pellets to reduce the impact of slug predation. For the sown community as a whole, the highest seedling emergence was recorded on subsoil plots sown in winter, and overall, winter sowing was superior. The lowest emergence was recorded on sand mulched plots sown in summer, although even in this treatment emergence was satisfactory in terms of landscape practice. For individual species, high levels of emergence were dependent upon specific combinations of soil type and sowing season. High seedling densities were recorded: from 64 seedlings/m 2 at the low rate, to 315 seedlings/m 2 at the high rate. The most successful species were: Echinacea pallida, Echinacea purpurea, Monarda fistulosa, Ratibida pinnata, and Solidago rigida. The least successful species were: Coreopsis tripteris, Solidago ohioensis, Sporobolus heterolepis, and Veronicastrum virginicum. Soil type had a significant influence on weed density in the experiment, with sand mulched plots the least weedy, and topsoil the most weedy. The study has shown that given control of mollusc predation during the emergence period, all of the species chosen could be established by sowing in situ in northern England.

Emergence, survival and initial growth of North American prairie forbs and British meadow forbs and grasses in low-productivity urban “waste” soils

SummaryTwenty-two species of North American and British forbs naturally associated with dry, unproductive habitats were sown as mono-cultures into pots containing mixes of brick rubble, sand and sub-soil. Three grass species native to Britain were also included as a contrast. Individual species exhibited considerable variation in emergence characteristics; both temporally, and as a percentage of seed sown. Geographical origin had no marked effect on emergence characteristics, although it appears that American species are more sensitive to moisture stress at germination. Grasses demonstrated significantly greater survival than either British or North American forbs at the group level of comparison and produced the highest biomass in the first growing season. North American forbs did not differ significantly from British forbs in terms of weight of first year growth. Overall, brick rubble proved to be the least satisfactory substrate in terms of emergence, survival and initial growth. Sand and sand:subsoil mixes supported high seedling emergence, survival and satisfactory first year growth. The results are discussed in relation to the physical and chemical properties of the four substrates, and an assessment is made of the implications of the study for future work.

High White-Tailed Deer Density Has Negative Impact on Tallgrass Prairie Forbs

ANDERSON, R. C., E. A. CORBETT, M. R. ANDERSON, G. A. CORBETr, AND T. M. KELLEY (4120-Department of Biological Sciences, Behavior, Ecology, Evolution, and Systematics Section, Illinois State University, Normal, Illinois 61790-4120). High white tailed deer density has negative impact on tallgrass prairie forbs. J. Torrey Bot. Soc. 128:381-392, 2001.-We studied the effect of deer browsing on prairie forbs under conditions of high deer density (30 to 42 deer km -2) on a single remnant tallgrass prairie in the Illinois Department of Natural Resources' Heidecke Lake Fish and Wildlife Area in northeastern Illinois. Almost no grasses or sedges were browsed and the frequency of browsing of graminoids was nearly the same in deer exclosure and reference plots. In contrast, deer browsed 3.5% to 18.9% of the standing crop of forb stems depending upon time of sampling. Deer selectively browsed 26% percent of the 100 species of forbs sampled in at least one of nine samples taken over three growing seasons. However, most species (17 of 26 selected species) were selected in only one sample. Highest browsing intensity occurred during late June and early July. Flowering stems of 3 species of forbs were significantly less abundant in the reference plots than in the exclosure plots, indicating a potentially adverse effect of deer browsing on the reproductive success of these prairie forbs. Deer are most likely to influence prairie vegetation by causing a shift in plant species abundance and competitive abilities in a way that favors grasses over forbs and reduces prairie plant diversity.