Schizachyrium Scoparium Research Articles

Pollinator Habitat Establishment after Organic and No-till Seedbed Preparation Methods

Establishing on-farm pollinator habitat can mitigate native pollinator and pollination ecosystem service declines, and federal programs are available to provide technical and financial assistance to farmers interested in habitat installation. Although sufficient seedbed preparation to limit weed competition is thought to be the most important step toward achieving good pollinator habitat establishment, preparation recommendations vary and studies have not investigated seedbed preparation techniques in the context of the U.S. Department of Agriculture (USDA) Farm Bill programs for pollinator conservation. To address this, we assessed the effects of two seedbed preparation methods, conventional inversion tillage and no-till with herbicide, on wildflower establishment and weed competition during the first year after planting. Experiments were conducted in Blacksburg, VA, and were replicated in 2015 and 2016. In addition, we tracked seedbed preparation methods and pollinator habitat establishment on seven farms located on the Eastern Shore of Virginia and Maryland in 2016. The wildflower mix consisted of nine species of forbs and two species of grasses: the forbs were black-eyed Susan (Rudbeckia hirta L.), partridge pea [Chamaecrista fasciculata (Michx.) Greene], plains coreopsis (Coreopsis tinctoria Nutt.), lanceleaf coreopsis (Coreopsis lanceolata L.), purple coneflower [Echinacea purpurea (L.) Moench], narrowleaf mountain mint (Pycnanthemum tenuifolium Schrad.), wild bergamot (Monarda fistulosa L.), Maximilian sunflower (Helianthus maximiliani Schrad.), and showy tickseed [Bidens aristosa (Michx.) Britton] or Indian blanket (Gaillardia pulchella Foug.); the grasses were splitbeard bluestem (Andropogon ternarius Michx.) and little bluestem [Schizachyrium scoparium (Michx.) Nash]. In the experiments, wildflower establishment was greater after no-till with herbicide than after tillage preparation (2015: P = 0.09; 2016: P = 0.002). Predominating weed species varied by study, with more common lambsquarters (Chenopodium album L.) and hairy galinsoga [Galinsoga ciliata (Raf.) S.F. Blake] growth after tillage treatments, and more hairy vetch (Vicia villosa Roth) growth after no-till preparation. On-farm pollinator habitat establishment on the Eastern Shore was highly variable, but more wildflower forbs established after tillage-plus-herbicide than tillage-only seedbed preparations (P = 0.01). Across sites, we found a large degree of site-specific variation in wildflower establishment and predominant weed species.

The potential of seven native North American forage species to suppress weeds through allelopathy

We conducted a series of three greenhouse studies to study the allelopathic effects of seven native perennial North American forage species alone and mixed on three problematic weeds including dand...

New distribution records and plant associations for Crophius scabrosus (Uhler, 1904) (Hemiptera: Lygaeoidea: Oxycarenidae)

Previous distribution records and plant associations are reviewed for the little-known oxycarenid Crophius scabrosus (Uhler, 1904). Based on fieldwork in the western United States, Kansas and Wyoming are reported as new state records. Adults were found on diverse plants in Nebraska, including juniper (Juniperus; Cupressaceae), pine (Pinus; Pinaceae), and composites (Compositae = Asteraceae); they were common in crowns of bunchgrasses (Poaceae), especially Panicum virgatum and Schizachyrium scoparium. Despite extensive fieldwork, nymphs were not found; a mating pair was observed on P. virgatum. Host plants—those supporting nymphal development— remain unknown, but composites such as species of Artemisia are suggested as potential hosts.

Precipitation and environmental constraints on three aspects of flowering in three dominant tallgrass species

Summary Flower production can comprise up to 70% of above‐ground primary production in grasslands. Yet we know relatively little about how the environment and timing of rainfall determine flower productivity. Evidence suggests that deficits or additions of rainfall during phenlologically relevant periods (i.e. growth, storage, initiation of flowering and reproduction) can determine flower production in grasslands. We used long‐term data from the Konza Prairie LTER to test how fire, soil topography and precipitation amounts during four phenologically relevant periods of the growing season constrain three aspects of flowering in three dominant C4 grass species. Specifically, we examined the probability of flowering, flowering stalk density and individual flowering stalk biomass for Andropogon gerardii, Schizachyrium scoparium and Sorghastrum nutans. We found that each of the three species responded to the amount of precipitation during phenologically relevant periods in unique ways. All aspects of A. gerardii flowering were sensitive to precipitation during the flowering stalk elongation period (20 June – 3 August). The probability of S. nutans flowering was partly determined by precipitation during the rapid growth phase (21 April – 4 June), whereas flowering stalk density of this species depended on rainfall during flowering stalk elongation (20 June – 3 August). In contrast, all aspects of flowering of S. scoparium were relatively independent of rainfall during any period. Our results demonstrate that three functionally similar, co‐dominant C4 grass species respond differently to phenologically relevant precipitation periods. As a result, drought during any phenological window during the growing season can adversely impact biomass and flowering production of grasslands via species‐specific reductions in flowering stalk density and biomass. A lay summary is available for this article.

Economic and conservation implications of converting exotic forages to native warm-season grass

Intensive agriculture can have negative environmental consequences such as nonpoint source pollution and the simplification of biotic communities, and land sharing posits that conservation can be enhanced by integrating agricultural productivity and biodiversity on the same land. In the Southeastern United States, native warm-season grasses (NWSG) may be a land sharing alternative to exotic forages currently in production because of greater livestock gains with lower fertilizer inputs, and habitat for grassland birds. However, uncertainty regarding costs and risk poses an important barrier to incorporating NWSG in livestock operations. We evaluated the economic and conservation implications of NWSG conversion among small, operational-scale pastures (6.8–10.5 ha) during 2011–2012 at the Prairie Research Unit in Monroe Co., Mississippi (USA). We used partial budgets to compare the marginal rate of return (MRRe) from converting exotic grass pastures to either a NWSG monoculture of Indiangrass (Sorghastrum nutans) or a NWSG mix of Indiangrass, little bluestem (Schizachyrium scoparium), and big bluestem (Andropogon gerardii). We similarly compared changes in productivity of dickcissels (Spiza americana), a grassland bird specializing in tall structure. Average daily gain (ADG) of steers and revenue were consistently higher for NWSG treatments than exotic grass pasture, but ADG declined between years. Indiangrass pastures yielded consistently positive MRRe, indicating producers would receive 16–24% return on investment. Marginal rate of return was lower for mixed NWSG (−12 to 3%), driven by slightly lower livestock ADG and higher establishment costs than for Indiangrass. Sensitivity analyses indicated that MRRe also was influenced by cattle selling price. Conversely, mixed NWSG increased dickcissel productivity by a greater degree than Indiangrass per amount invested in NWSG conversion, suggesting a tradeoff between livestock and dickcissel production between the two NWSG treatments. Given continued increases in livestock prices, NWSG could be a sustainable land sharing alternative to exotic pastures currently in production, but subsidies and changes in management may be required for NWSG conversion to be viable for producers and to maintain conservation benefits.

Field-Scale Phytoremediation of Mixed Contaminants in Upland Area of Big Marsh Site, Chicago, USA

The suitability of nine native restoration plant species has been evaluated for phytoremediation of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in upland area of Big Marsh site (Chicago, IL, USA). From the initial nine species planted in the experimental area, only the prairie grass Little Bluestem (Andropogon scoparius) survived the three growing seasons. Replicate test plots were prepared by tilling and homogenizing the surface soil and underlying fill materials to approximate depth of 0.3 m. The survival and growth of the plant species were monitored for the first two growing seasons. Soil samples from each plot were collected before and after preparing the test plots and after the second and third growing seasons. Plant root and shoot samples were also collected at the end of the second and third growing seasons. PAHs and heavy metals were analyzed in the soil and plant samples. In addition, sequential extraction procedure was followed to determine the fractionation of the heavy metals in soils before and after planting. Analysis of benzo-a-pyrene (typical PAH) concentrations in roots showed an uptake and accumulation of this contaminant in the below-ground part of the plant, while the presence of the organic contaminants in stems and leaves of the surviving plant were non-detectable. No significant decrease of heavy metals was found in the soil at the end of the experiment. Furthermore, the presence of plants did not affect the heavy metal mobility or speciation in the soil. However, the presence of chromium (Cr), lead (Pb), manganese (Mn) and zinc (Zn) in the roots of Little Bluestem indicated the uptake and accumulation of these metals in the plant. The presence of Cr and Pb in stems and leaves was below detection limits, while concentrations of Mn and Zn were found to increase in the aerial part of the plant towards the end of the experiment. The survival of Little Bluestem and its high tolerance to the site conditions, makes it a suitable species for the phytoremediation of conditions representative of the upland areas of the field site.

Predators and Prickly Paradigms: Nesting Ecology of Bobwhites and Scaled Quail in West Texas

Sporadic recruitment appears to be the impetus for the irruptive population patterns observed along the western edge of northern bobwhite (Colinus virginianus) range. We investigated hen survival, nest selection strategies, and reproductive success of sympatric northern bobwhites and scaled quail (Callipepla squamata) in west Texas. Radio-marked bobwhites, along with a smaller sample of sympatric scaled quail, were monitored during the spring and summer of 1994 and 1995. Predation was the major source of mortality, with mammals and raptors responsible for about 60 and 30 percent of the mortalities observed, respectively. We used TrailMaster camera systems to document the presence and behavior of various nest predators. Raccoons (Procyon lotor) appear to be the dominant nest predator in this area, accounting for over 80 percent of the nests destroyed. Photographic surveillance of artificial nests provides some clues for making objective assessments of predators involved in nest depredations. The amount and kinds of egg shell evidence at a nest site varied with egg size (chicken vs quail). We found egg shell evidence at 83 percent of nests using chicken eggs, but only at 3 percent of nests using quail eggs. We predict that snakes are overrated in their importance as a nest predator, when such diagnoses are based solely on the absence of physical evidence (i.e., no egg shells). Our results suggest that pricklypear (Opuntia spp.) was a key nesting microhabitat. Overall, 12 of 21 bobwhite and 8 of 12 scaled quail nests were located in pricklypear. Subsequent investigations revealed that nests situated in pricklypear were afforded higher survival, especially in more arid sites with less traditional nesting cover (e.g., Schizachyrium scoparium). Initial results with intensive, short-term mammal removal suggest that nest survival can be increased for about $0.35 per hectare.

Ten-year persistence of native plant species on a green roof in Northeast US

We evaluated persistence of 28 northeastern or Midwestern US native plants for 10 y after installation on the green roof of the Wellesley College Water Treatment Facility. After 10 y, 50% of the original 28 species had perished and 29% had greatly expanded their presence on the green roof. Allium cernuum Roth (nodding onion; Liliaceae), Antennaria plantaginifolia (L.) Richardson (pussytoes; Asteraceae), Arctostaphylos uva-ursi (L.) Spreng. (kinnikinnick; Ericaceae), Campanula rotundifolia L. (bluebell bellflower; Campanulaceae), Carex pensylvanica Lam. (Pennsylvania sedge; Cyperaceae), Eurybia divaricata (L.) G.L. Nesom (white wood aster; Asteraceae), Fragaria virginiana Duchesne (Virginia strawberry; Rosaceae), ( Oligoneuron album (Nutt.) G.L. Nesom (prairie goldenrod; Asteraceae), Schizachyrium scoparium (Michx.) Nash (little bluestem; Poaceae), Solidago sciaphila Steele (shadowy goldenrod; Asteraceae), and Symphyotrichum laeve (L.) A. Love & D. Love (smooth blue aster; Asteraceae) were able to persist and grow in response to the challenging green roof conditions, and we recommend them for use on green roofs. Twenty-seven emergent species were present on the green roof at the end of the study. Emergent Solidago L. (goldenrod; Asteraceae) species, Solidago caesia L. (wreath goldenrod), Solidago odora Aiton (anise scented goldenrod), and Solidago rugosa Mill. (wrinkleleaf goldenrod) should be investigated further for their suitability in green roof installations. Lubell JD, Connolly B, Jones KN. 2017. Ten-year persistence of native plant species on a green roof in Northeast US. Native Plants Journal 18(3):227–234.

Wiregrass (Aristida beyrichiana) May Limit Woody Plant Encroachment in Longleaf Pine (Pinus palustris) Ecosystems

Wiregrass (Aristida beyrichiana) is a dominant groundcover species that facilitates fire in southeastern U.S.A. pine savannas, thereby limiting woody plant cover and maintaining a herbaceous dominated understory. In December 1993 two of us planted a plot of wiregrass (Aristida beyrichiana) in the midst of fire-maintained little bluestem (Schizachyrium scoparium) longleaf pine (Pinus palustris) savanna in the outer Coastal Plain of South Carolina. The plot and the surrounding area burned three times in the following 20 y. Vegetation sampling carried out in late summer 2013 indicated wiregrass dominated the plot and the majority of little bluestem had disappeared. The wiregrass plot was comparatively open and grass dominated, whereas the surrounding formerly bluestem dominated stand had filled in with loblolly pine (Pinus taeda) saplings as well as hardwood trees and shrubs. In addition wiregrass had reproduced and established away from the original planted area, most noticeably within a soil-disturbed plow line. A subsequent prescribed fire in spring 2014 burned with higher intensity within the wiregrass plot than in the surrounding area. Our observations suggest suppression of woody plant encroachment by dense wiregrass in pine savannas even during long fire free periods, which should reduce the likelihood of transition to hardwood dominated ecosystems.

Predicting Northern Bobwhite Habitat in Semiarid Rangeland Using Landsat Imagery

Multiple studies have attempted to model northern bobwhite (Colinus virginianus) distribution using classified remotely sensed imagery in combination with pattern recognition software. These models tend to be more accurate in humid subtropical regions. To identify bobwhite habitat in subhumid and semiarid rangeland, we performed our own classification on 4 LANDSAT scenes of Clay County, Texas, from July and December 2015. Stands of mature little bluestem (Schizachyrium scoparium) provide excellent bobwhite nesting cover and could be identified using LANDSAT imagery. Habitat was scored from 0 to 1.0 based on estimated range health, presence of little bluestem, and presence of brushy cover. We compared habitat score with the results of breeding season call counts from 2014 and 2015 and found significant correlation. When used in combination with other landscape data, this approach can provide a regional context to inform conservation and management decisions.

Response of native plants to elevated soil nitrogen in the sand dunes of Lake Michigan, USA

Atmospheric deposition of nitrogen (N) has been reported to reduce the diversity of plant species in N-limited soil. The sand dunes along the southern shore of Lake Michigan have been N-limited historically but receive substantial amount of N from the atmosphere currently. We investigated the effect of N-addition to soil on seed germination rates and species composition of nine native plants. In the greenhouse, the ambient addition (15kgNha−1yr−1) enhanced the germination of Elymus canadensis and Echinacea purpurea, while the 9× ambient N addition reduced seed germination of Dalea purpurea and Elymus. However, regardless the results from greenhouse, these species exhibited no or poor emergence in the field plots. Panicum virgatum was the only species whose germination was promoted significantly by the ambient addition in the greenhouse and also emerged in the field plots in the early years (2010−2012), but its dominance diminished during 2013–2014. The decline of Panicum suggests a failure of establishment and reproduction after germination. Such failure has likely led to reduction or exhaustion of viable seeds in soil. Meanwhile, the species that showed relatively low germination rates (<20%) in the greenhouse, such as Lupinus perennis, Monarda punctata and Schizachyrium scoparium, established substantially in the field plots. Also in the field plots, soil with elevated-N (3×, 5× and 9× ambient) appeared to favor grass over forb species. Dominance of grass over forb species has led to a reduction in species diversity and divergence of species composition between the ambient and elevated-N plots.

Finding partners in a habitat mosaic: Patch history and size mediate host colonization by arbuscular mycorrhizal fungi

AbstractRestoration of glades over the past 30 years, involving removal of woody cover and re‐establishment of herbaceous plant communities, has created an archipelago of habitat patches varying in age, size, and isolation. Within these glades, habitat varies in quality from edge to core. We investigated impacts of within‐ and among‐glade variation on the frequency of root colonization by arbuscular mycorrhizal fungi (AMF) for two host species, Schizachyrium scoparium and Rudbeckia missouriensis, and the plant community at large. We also conducted a soil analysis to explore the role of nutrient resources in mediating putative habitat effects. We used Akaike's information criterion (AIC) to evaluate a set of a priori models that assessed effects of glade size, isolation, age, and edge effects on AMF colonization. In community samples, AMF colonization increased while variation in AMF colonization decreased with restoration age. Edge effects also reduced plant community AMF colonization. AMF colonization was higher in R. missouriensis than in S. scoparium, but increased for both species in core habitat. Glade size had no direct effect on AMF at the plant scale, but indirectly affected overall AMF occupancy at the landscape scale via its geometric relationship to glade edge:core ratio. Hosts in small glades that are dominated by edge exhibit lower occupancy rates. The first two axes in a principal components analysis (PCA) combining soil nutrient variables explained 74% of sample variance: PC1 correlated positively with organic matter (OM), total nitrogen (N), calcium (Ca), magnesium (Mg), and potassium (K) and decreased from the edge to the core of older glades. PC2, which correlated positively with pH and negatively with available P, increased with time since restoration. While results are consistent with a role of soil properties in explaining edge and age effects, the two PCA dimensions themselves are weakly correlated with AMF colonization. Overall, our findings suggest that environmental filters associated with woody encroachment limit the colonization of otherwise suitable herbaceous hosts and create a landscape mosaic with larger, older glades serving as hotspots or reservoirs of AMF root colonization and smaller, newly restored glades as cold spots or potential sinks.

A native plant competitor mediates the impact of above- and belowground damage on an invasive tree.

Plant competition may mediate the impacts of herbivory on invasive plant species through effects on plant growth and defense. This may predictably depend on whether herbivory occurs above or below ground and on relative plant competitive ability. We simulated the potential impact of above- or belowground damage by biocontrol agents on the growth of a woody invader (Chinese tallow tree, Triadica sebifera) through artificial herbivory, with or without competition with a native grass, little bluestem (Schizachyrium scoparium). We measured two defense responses of Triadica through quantifying constitutive and induced extrafloral nectar production and tolerance of above- and belowground damage (root and shoot biomass regrowth). We examined genetic variation in plant growth and defense across native (China) and invasive (United States) Triadica populations. Without competition, aboveground damage had a greater impact than belowground damage on Triadica performance, whereas with competition and above- and belowground damage impacted Triadica similarly. Whole plant tolerance to damage below ground was negatively associated with tolerance to grass competitors indicating tradeoffs in the ability to tolerate herbivory vs. compete. Competition reduced investment in defensive extrafloral nectar (EFN) production. Aboveground damage inhibited rather than induced EFN production while belowground plant damage did not impact aboveground nectar production. We found some support for the evolution of increased competitive ability hypothesis for invasive plants as United States plants were larger than native China plants and were more plastic in their response to biotic stressors than China plants (they altered their root to shoot ratios dependent on herbivory and competition treatments). Our results indicate that habitat type and the presence of competitors may be a larger determinant of herbivory impact than feeding mode and suggest that integrated pest management strategies including competitive dynamics of recipient communities should be incorporated into biological control agent evaluation at earlier stages.

Converting exotic forages to native warm-season grass can increase avian productivity in beef production systems

Grasslands are among the most imperiled ecosystems in the world, and establishment of exotic forage grasses and management for uniform utilization may have contributed to population declines of many obligate grassland bird species in North America. Native warm-season grasses (NWSG) are increasingly promoted as viable alternatives to exotic forages currently in production such as bermudagrass (Cynodon dactylon) and tall fescue (Schedonorus arundinaceus), but structure of native bunchgrasses also may offer nesting habitat for birds such as the dickcissel (Spiza americana). Establishing NWSG pastures may thereby create an opportunity for land-sharing, where agriculture incorporates biodiversity-friendly practices. We investigated dickcissel responses to NWSG and grazing at the Prairie Research Unit in Monroe Co., Mississippi (USA), where we established a gradient of management intensity among four treatments in small, operational-scale pastures (6.4–10.5ha). Treatments included grazed exotic forages, two grazed NWSG treatments including Indian grass (Sorghastrum nutans) monoculture and grazed mixed NWSG polyculture of Indian grass, little bluestem (Schizachyrium scoparium), and big bluestem (Andropogon gerardii), and a non-grazed NWSG polyculture treatment. We applied a multi-state capture-recapture model in a Bayesian framework to estimate dickcissel nest density and productivity while accounting for nest stage-specific variation in survival and detection. Nest density and productivity were consistently greater in non-grazed NWSG than grazed exotic pasture, whereas productivity in grazed NWSG treatments was intermediate but declined between years. We also found that variation in survival and density did not always correspond with estimated productivity, and thus solely relying on either parameter may be misleading when making inferences on habitat quality. These results suggest a positive response to NWSG among dickcissels in this system, but grazing may reduce nest site abundance, and consequently productivity. Native warm-season forages may be a viable land-sharing alternative by increasing productivity of tall structure specialists such as dickcissels compared with exotic grass pastures currently in production, but grazing should be managed to ensure abundance of tall vegetation structure for nest sites.

Establishment‐Year Native Perennial Bunchgrass Biomass Yields

Weak seedling vigor of native North American perennial bunchgrasses may result in poor establishment‐season herbage dry matter (DM) yields (HY). Interseeding North American annual legumes as an N source during grassland restoration, pasture establishment, or bioenergy crop seeding might compound this limitation. Our first objective was to evaluate yellow Indiangrass [Sorghastrum nutans (L.) Nash], switchgrass (Panicum virgatum L.), and little bluestem [Schizachyrium scoparium (Michx.) Nash] first‐season HY in the southern Great Plains of North America. This took place in north–central Texas on a Windthorst fine sandy loam soil with no irrigation or soil amendments. Our second objective was to measure the effects of cross‐drilling native North American annual legumes smooth‐seeded wild bean [Strophostyles leiosperma (Torr. &amp; Gray) Piper], trailing wild bean [Strophostyles helvula (L.) Elliott], and showy partridge pea [Chamaecrista fasciculata (Michx.) Greene] on bunchgrass first‐season HY. In the drier (340 mm) year, legumes failed to establish, while switchgrass produced 2410 and Indiangrass yielded 1980 kg HY ha−1 y−1. In the year with 687 mm rainfall, legumes had no negative effects (P &gt; 0.05) on grass HY (5490 kg HY ha−1 y−1 for switchgrass) despite providing up to 49 through 1800 kg HY ha−1 y−1 (showy partridge‐pea with little bluestem; P ≤ 0.05 for year by grass × legume interactions). Our results indicate that these bunchgrasses produced harvestable HY during their establishment year and that simultaneously seeding annual legumes did not impair native perennial grass establishment while, in 1 yr, making potential N contributions for subsequent stand productivity.

Phylogenetic diversity reveals hidden patterns related to population source and species pools during restoration

Summary A phylogenetic perspective of community assembly can reveal new insights into how variation within dominant species interacts with the local species pool to influence the structure of restored plant communities. Many studies have examined the effect of dominant species in structuring plant communities, but few have investigated their effect on phylogenetic diversity (PD). We established grassland in a post‐agricultural field using two population sources (cultivars and local ecotypes) of three dominant grasses (Sorghastrum nutans, Andropogon gerardii and Schizachyrium scoparium) with three unique pools of subordinate species that varied in PD but not taxonomic or life‐form diversity. We tested the effect of the population source treatment on two metrics of community PD (net relatedness index [NRI] and nearest taxon index [NTI]) during the first 4 years of restoration. The NRI measures the overall pairwise phylogenetic distance between all pairs of taxa in a community. By contrast, NTI measures the pairwise distance between closely related taxa in a community. Population sources had a transitory effect on community phylogenetic structure over time. Local ecotypes decreased the abundance of closely related eudicots, monocots (low +NRI and +NTI values) and volunteer species (−NTI) more than cultivars. However, population sources did not affect ecologically conservative species (i.e. species with intermediate‐to‐poor ecological tolerance and a high degree of fidelity to prairie habitats). Thus, cultivars might have a positive effect on community phylogenetic diversity more than local ecotypes by decreasing the abundance of a phylogenetically diverse community of less closely related volunteer species. Differences in PD of seed mixes were maintained in the community of high‐fidelity species, but did not affect PD of the unsown (volunteer) species in the assembling community. Synthesis and applications. This is the first experiment to show consequences of using different seed sources on phylogenetic diversity (PD) in grassland restoration. Phylogenetics can reveal the effects of population sources on the abundance of volunteer species not evident through traditional analyses of species diversity. The PD of seed mixes or establishing communities, or other assessments of phylogenetic relationships, by restoration practitioners is recommended as a metric to allow consequences of the evolutionary patterns among species to be included in conservation planning. Increased accessibility of phylogenetic tools will allow the application of PD in restoration monitoring.

Long-term Sandhills prairie responses to precipitation, temperature, and cattle stocking rate

Understanding of Sandhills prairie, the most expansive sand dune region stabilized by perennial grasses in the Western Hemisphere, is limited by lack of long-term vegetation data. We used a 26-year dataset to evaluate Sandhills prairie responses to year-to-year variation in precipitation, temperature, and cattle stocking rate. Basal cover, a measurement that is constant seasonally and used to detect long-term changes in bunchgrass vegetation, was measured in 38–40 permanent plots positioned along four transects spanning 769 ha from 1979 to 2007. Across this period, total basal cover averaged 2.4 % and was dominated by warm-season grasses (81.1 %). Schizachyrium scoparium (little bluestem), the dominant warm-season bunchgrass, consisted of 60.0 % relative basal cover. Warm-season grass and total basal cover responded positively to lag 3-year growing season precipitation indicating delayed responses to improved growing season conditions, but these variables also were positively associated with stocking rate. The positive responses may be due to slow spread of warm-season grasses by vegetative structures in response to favorable growing conditions in light to moderately stocked rangeland. Despite its dominance, however, warm-season grass cover had no influence on cover of other functional groups providing weak support for competition as regulator of Sandhills prairie composition. Forb cover was best related in a negative manner to 3-year running mean total precipitation, a surprising result that maybe signaling factors governing basal responses in prairie remain largely unresolved. Woody species cover, however, was positively associated with mean growing season temperatures indicating potential of these to spread under warming scenarios.

Above- and below-ground responses of native and invasive prairie grasses to future climate scenarios

More intense and frequent droughts, coupled with elevated temperatures, are projected for grasslands worldwide. Although it has been suggested that alterations in temperature and precipitation will increase the success of biological invasions, studies that combine these climate change scenarios are limited. These changes in climate may increase the success of non-native, invasive plant species directly, as these species often possess traits that are favored by variable climates, or indirectly through negative impacts on native vegetation or alterations in soil microbial communities, such as arbuscular mycorrhizal (AM) fungi. The goal of our research was to assess above- and below-ground production and mycorrhizal fungal abundance of functionally similar native and invasive non-native grass species under projected climate-change scenarios. We assessed plant biomass, intra-radical AM root colonization, and relative abundance of extra-radical fungal biomass of two native (Schizachyrium scoparium (Michx.) Nash, Pascopyrum smithii (Rydb.) Á.Löve) and two invasive (Bothriochloa ischaemum (L.) Keng, Bromus inermis Leyss.) grass species subjected to increased temperature and decreased soil water availability. Regardless of temperature or soil moisture, the invasive grasses in our study displayed greater seedling growth as compared with paired native species. Invasive grasses were also generally characterized by greater intra-radical colonization by AM fungi, compared with native species. Our data suggest that invasive grasses will continue to be problematic and successfully out-compete native grasses following increased temperatures and reduced water availability, as projected by climate-change models.

Relative Performance of Non-Local Cultivars and Local, Wild Populations of Switchgrass (Panicum virgatum) in Competition Experiments.

The possibility of increased invasiveness in cultivated varieties of native perennial species is a question of interest in biofuel risk assessment. Competitive success is a key factor in the fitness and invasive potential of perennial plants, and thus the large-scale release of high-yielding biomass cultivars warrants empirical comparisons with local conspecifics in the presence of competitors. We evaluated the performance of non-local cultivars and local wild biotypes of the tallgrass species Panicum virgatum L. (switchgrass) in competition experiments during two growing seasons in Ohio and Iowa. At each location, we measured growth and reproductive traits (plant height, tiller number, flowering time, aboveground biomass, and seed production) of four non-locally sourced cultivars and two locally collected wild biotypes. Plants were grown in common garden experiments under three types of competition, referred to as none, moderate (with Schizachyrium scoparium), and high (with Bromus inermis). In both states, the two “lowland” cultivars grew taller, flowered later, and produced between 2x and 7.5x more biomass and between 3x and 34x more seeds per plant than local wild biotypes, while the other two cultivars were comparable to wild biotypes in these traits. Competition did not affect relative differences among biotypes, with the exception of shoot number, which was more similar among biotypes under high competition. Insights into functional differences between cultivars and wild biotypes are crucial for developing biomass crops while mitigating the potential for invasiveness. Here, two of the four cultivars generally performed better than wild biotypes, indicating that these biotypes may pose more of a risk in terms of their ability to establish vigorous feral populations in new regions outside of their area of origin. Our results support an ongoing assessment of switchgrass cultivars developed for large-scale planting for biofuels.

Notice of release of Carrizo Blend little bluestem: a selected class of natural germplasm

A commercial blend of 2 selected class germplasm of little bluestem (Schizachyrium scoparium (Michx.) Nash var. scoparium [Poaceae]) was released in 2015 for rangeland and wildlife habitat restoration seedings in South Texas. Carrizo Blend little bluestem is a post-harvest blend of STN-176 Germplasm and STN-461 Germplasm little bluestems. These selections were made from evaluations of 95 native populations of little bluestem collected from southern Texas that were compared with available commercial standards at 3 evaluation sites in the region. Upon selection, seed stock for release of the 2 selections was grown in isolation using outplants grown from the original wild seed collections to maintain the genetic integrity of the source populations. Carrizo Blend little bluestem represents the first selected, ecotypic seed source of little bluestem for use in South Texas.