Restoration Of Native Grasslands Research Articles

A decade‐long study of repeated prescription burning in California native grassland restoration

Native bunchgrass communities dominated by Stipa pulchra are widely distributed in California but share dominance with non‐native annual grasses. Restoration of these grasslands focuses on altering the balance of native to non‐native grasses to favor the former. This study investigated the impact of burning on vegetation recovery. In the first postfire year burning showed a 70% reduction in cover of non‐native annual grasses (Bromus diandrus exhibited the greatest reduction) and minimal impact on S. pulchra recovery. In the following 3 years, S. pulchra recovered to levels comparable to controls, whereas the annual grasses remained below control levels until the fifth year. Also, in response to reduced annual grass cover on burned sites several species of non‐native Erodium increased from 10 to 30% relative cover, however, the low growth form of these forbs presented a less competitive threat to bunchgrasses than the non‐native annual grasses, and by the third postfire year returned to near control levels. The rare native geophyte Brodiaea kinkiensis was present throughout these grasslands and was not inhibited by burning treatments. To document the reliability of these patterns a second prescription burn was conducted on these sites 5 years after the first burn and vegetation recovery followed for the subsequent 4 years. Patterns observed after the first burn were duplicated following the second burn. The cover of S. pulchra varied in response to precipitation, with the 95% credible intervals of precipitation parameters overlapping zero, however, the cover of non‐native grasses varied greatly with precipitation and had similar trajectories in unburned and burned plots.

Inoculation with native soil improves seedling survival and reduces non‐native reinvasion in a grassland restoration

Losses of grasslands have been largely attributed to widespread land‐use changes, such as conversion to row‐crop agriculture. The remaining tallgrass prairie faces further losses due to biological invasions by non‐native plant species, often with resultant ecosystem degradation. Of critical concern for conservation, restoration of native grasslands has been met with little success following eradication of non‐native plants. In addition to the direct and indirect effects of non‐native invasive plants on beneficial soil microbes, management practices targeting invasive species may also negatively affect subsequent restoration efforts. To assess mechanisms limiting germination and survival of native species and to improve native species establishment, we established six replicate plots of each of the following four treatments: (1) inoculated with freshly collected prairie soil with native seeds; (2) inoculated with steam‐pasteurized soil with native seeds; (3) noninoculated with native seeds; or (4) noninoculated/nonseeded control. Inoculation with whole soil did not improve seed germination; however, addition of whole soil significantly improved native species survival, compared to pasteurized soil or noninoculated treatments. Inoculation with whole soil significantly decreased reestablishment of non‐native invasive Bothriochloa bladhii (Caucasian bluestem); at the end of the growing season, plots receiving whole soil consisted of approximately 30% B. bladhii cover, compared to approximately 80% in plots receiving no soil inoculum. Our results suggest invasion and eradication efforts negatively affect arbuscular mycorrhizal hyphal and spore abundances and soil aggregate stability, and inoculation with locally adapted soil microbial communities can improve metrics of restoration success, including plant species richness and diversity, while decreasing reinvasion by non‐native species.

Responses of Flowering Plant and Butterfly Communities to Experimental Herbicide and Seeding Treatments for Native Grassland Restoration

Responses of Flowering Plant and Butterfly Communities to Experimental Herbicide and Seeding Treatments for Native Grassland Restoration

Long‐Term Elimination of Grazing Reverses the Effects of Shrub Encroachment on Soil and Vegetation on the Ordos Plateau

AbstractConversion from grasslands to shrublands resulting from overgrazing occurs worldwide and is reinforced by the global climatic change. The functioning, biogeochemical cycles (e.g., carbon and water), and the stability of grassland ecosystems are significantly affected by the conversion. To best manage and use those grassland ecosystems, it is imperative to examine how the shrub‐encroached grasslands can be restored to native grassland ecosystems. In this study, aboveground biomass of all species, root biomass, soil water content, and soil texture in a set of fenced and unfenced plots were observed every three years from 1992 to 2011 in a semishrub encroached grassland on the Ordos Plateau of China. In the fenced plots, aboveground biomass increased for grass species and decreased for semishrub species. Root biomass and soil water content in the 0–10‐cm soil layer increased, but decreased in the 10–30‐cm soil layers. The fraction of soil particle sizes less than 0.01 mm increased in the 0–10‐cm soil layer. In contrast, these variables remained constant in the unfenced plots over the experimental period. The semishrub encroached grassland dominated by Artemisia ordosica was replaced with a native perennial grass, Stipa bungeana, when grazing was eliminated in the fenced plots. Changes in soil texture and moisture after fencing were correlated with the native grassland restoration from semishrub encroached grasslands. This study suggests that, to restore the native grassland, grazing should be eliminated in the study region.

Eastern grasslands: Conservation challenges and opportunities on private lands

ABSTRACTGrasslands were once common in the eastern United States and provided habitat for numerous grassland‐dependent wildlife. However, native grasslands in this region have largely been eliminated as a result of conversion to other land uses (e.g., urban development, row‐crops), altered disturbance regimes (e.g., lack of fire and grazing), or conversion to introduced grasses for livestock production. Consequently, many wildlife species adapted to these environments have experienced protracted population declines, notably, northern bobwhite (Colinus virginianus), and other grassland‐dependent bird species. Restoration of native grasslands with appropriate native plant species composition, structure, and disturbance regimes will be key to restoring at‐risk wildlife. Indeed, the region still includes >20 million ha of grasslands, but these are dominated by introduced grass species and focused on cattle (Bos taurus) production. Any successful restoration strategy must engage the agricultural community, provide profitable forage production, and benefit habitat for wildlife. Furthermore, grassland ecosystems in humid regions (i.e., >95 cm annual rainfall) require frequent disturbance to prevent succession to forested conditions. Historically, these native grasslands were maintained by fire, herbivory, and their interaction. Consequently, wildlife communities in humid, native grasslands are adapted to those same disturbances and the conditions they create. Improving species composition by replacing introduced, sod‐forming grass species commonly used in production agriculture (e.g., tall fescue [Schedonorus arundinaceus] and bermudagrass [Cynodon dactylon]) with native grasses can be beneficial but must be accompanied by appropriate disturbance to achieve and maintain improved habitat. Therefore, developing a business case for producers to incorporate native grasses into regional agro‐grasslands that include disturbance through grazing may foster large‐scale improvements in habitat quality. Although Farm Bill conservation practices can make important contributions to conservation of eastern grassland‐dependent wildlife, such programs are dependent on uncertain and limited federal budgets and, to provide appropriate disturbance, require management intervention at a net cost to landowners and Farm Bill programs. Thus, there exists an opportunity to improve habitat at a scale that has the potential to sustain viable populations of grassland‐dependent wildlife. Therefore, we discuss the potential of a new conservation paradigm, one based on grazing systems that utilize native grasses, for filling that conservation gap. © 2019 The Wildlife Society.

A Low Organic Matter Soil Does Not Maintain a Native Grassland Restoration in the Colorado Front Range

A Low Organic Matter Soil Does Not Maintain a Native Grassland Restoration in the Colorado Front Range

Three years of vegetation development worth 30 years of secondary succession in urban‐industrial grassland restoration

AbstractQuestionsThe restoration of unused urban‐industrial areas has largely been neglected despite their great potential for nature conservation purposes. We applied three plant introduction treatments at a highly degraded industrial area to test whether plant material introduced onto industrial areas initiates plant assemblages similar in composition to those of reference grasslands. We specifically asked (a) Does restoration differ between primary and secondary reference sites in terms of overall species richness and cover three years after the introduction of plant material? (b) What is the sociability of species of the vegetation resulting from different treatments?LocationRestoration and reference grassland sites with acidic sandy soil in the temperate region of the EU, NE Hungary, Nyírség.MethodsAs restoration techniques, we (a) directly seeded a single dominant species, (b) applied a commercial seed mixture, and (c) transferred hay. We compared species composition, cover, species richness and sociability of species in restoration treatments to reference grasslands. Inventories of vascular plant species were made at five randomly placed 2 m × 2 m sampling units per plot.ResultsThe species composition of seeded restoration plots (with a single dominant species and a commercial seed mixture) became similar to that of reference grasslands. Both types of seeding resulted in a similar cover, whereas seeding a commercial seed mixture and hay transfer resulted in a species richness similar to that of reference grasslands. The cover of the natural constituents (NC) of seeded plots also reached that of reference grasslands, while hay addition resulted in a lower cover and a higher number of NC than other methods.ConclusionsThe introduction of propagules in degraded industrial areas can provide communities similar, after three years, to those of secondary reference grasslands that are 30 years of age. We conclude that investing in the restoration of native grasslands at unused urban‐industrial sites can be a great opportunity to enhance biodiversity.

A field test of commercial soil microbial treatments on native grassland restoration

Seedling establishment and performance are often limiting steps in many grassland restorations. The soil microbial community is thought to be a factor that contributes to the poor performance of seedlings. Therefore, we conducted a field test to examine the ability of four treatments to alter the soil microbial community and improve seedling performance during restoration. Treatments were commercially available bacterial inoculum, fungal inoculum, fungicide, and a bacteria/fungicide combination which were all designed and sold to enhance plant performance. We hypothesized that if the soil microbial community was limiting the performance of seedlings, then these products would remediate detrimental effects of the soil microbial community resulting in greater seedling performance. However, during the 2 years after restoration, no effect of the treatments was found. It is plausible that the treatments designed for agriculture or home garden settings were not appropriate for a wildland system.

Evaluation of Locally-Adapted Native Seed Sources and Impacts of Livestock Grazing for Restoration of Historic Oil Pad Sites in South Texas

Oil and gas activities, particularly road and drilling pad construction, impact large acreages of native rangelands across the country. Many landowners attempt to restore the pad sites of historic wells to native vegetation with varying results. To test the ability of a locally-adapted, native seed mix, made up of grasses, forbs, and legumes, we attempted to restore four former oil and gas wells to their historic grassland state. Adding to the complexity of the restoration process, these pads were located within large grazing units, making it unfeasible to exclude grazing. We evaluated the ability of the native seed mix to establish and persist, and the effects of grazing by cattle the on the restored sites for two years after planting. By seven months post seeding, we were able to establish restored species density of ≥ 0.9 seeded plants/m2, comprising of an average of eight different species. Cattle grazing had little effect on the density of seeded species. Cattle grazing did have minor effects on species composition; however, these effects are not likely to create any long term effects on species composition. These results are promising to landowners attempting to perform native grassland restoration following oil and gas activities in South Texas, even when livestock exclusion is impractical.

A County-Based Northern Bobwhite Habitat Prioritization Model for Kentucky

Planning the management of northern bobwhite (Colinus virginianus) habitat at a statewide-scale is daunting. Native grassland restoration is difficult to manage in Kentucky because . 99% of the Commonwealth’s original grassland area has been lost to agriculture, succession, and development. We created a county prioritization model designed to target areas of grasslands and landowners likely to participate in conservation programs. Our goal was to identify 10% of the state as high priority for bobwhite habitat restoration. We created an east and west model divided by the Appalachian Mountains. The west model was designed to target production-oriented operators farming marginal lands, whereas the east model targeted reclaimed minelands. We used agricultural, landcover, and staff data to build county prioritization models in 2006 and 2011. The models targeted 16.6% and 17.6% of the state in 2006 and 2011, respectively. However, if areas of large, contiguous blocks of forests were excluded, the area total was much closer to 10%. Fifty percent of the high priority counties changed in the west model, and 33% of the counties in the east model changed over 5 years. Implementing a county prioritization model in conjunction with a finer-scale, biological targeted approach could focus conservation efforts with greater potential for success, but the models should be reconstructed at 5- to 10-year intervals to account for changes in conservation delivery potential. A modification of our technique may serve to validate or as an alternative to improve National Bobwhite Conservation Initiative 2.0.

Population Response of Three Quail Species to Habitat Restoration in South Texas

Maintaining and increasing usable space is paramount for maintaining and increasing wild quail. Aside from weather and other factors that can temporarily reduce densities, range-wide, no factor has as much influence on quail populations as the amount of habitat present across the landscape. In the field of quail management, ‘‘bad news’’ is the norm, as many articles begin by explaining how a select species has declined. Here we provide good news and use 4 empirical examples of population increases for 3 quail species following creation of usable space and restoration of patch connectivity. From 2008–2014, a suite of independent projects aimed at increasing usable space for quail was initiated across South Texas. These projects included 3 focused on northern bobwhites (Colinus virginianus), 1 focused on scaled quail (Callipepla squamata), and 1 landowner-executed project focused on Montezuma quail (Cyrtonyx montezumae). Through the correction of attributes limiting habitat, bobwhite numbers increased 22–378% across 2 studies. On one particular study site, native grassland restoration resulted in the colonization of bobwhites from adjacent areas to 1 bobwhite/1.2 ha from nearly 0. For scaled quail in South Texas, reducing buffelgrass standing crop via grazing from about 2,240 kg/ha to 1,008 kg/ha resulted in the recolonization of a previously unoccupied habitat patch to a density of 1 scaled quail/6 ha. Finally, clearing monotypic stands of the invasive native plant, ash juniper (Juniperus ashei) in the Edwards Plateau of Texas, resulted in the reestablishment of native grasses and forbs and thus recolonization by Montezuma quail from nearby areas. Although habitat restoration and management can be a painstaking and lengthy process, addressing limiting factors to quail occupancy is the only known way to increase wild quail populations. We hope that highlighting these particular studies will provide inspiration to those interested in restoring and increasing quail across the US.

Short-term priority over exotic annuals increases the initial density and longer-term cover of native perennial grasses.

Temporal priority can affect individual performance and reproduction, as well as community assembly, but whether these effects persist over time remains unclear, and their demographic mechanisms have been little explored. The continued dominance of exotic annual grasses in California has been commonly attributed to their demonstrated early germination and rapid early growth relative to native perennial grasses. This advantage may play a crucial role in the structure of California exotic annual grasslands, as well as in the practice of native grassland restoration. We tested whether a two-week planting advantage under field conditions increased individual survival, growth, and reproduction for four native perennial grass species and whether these effects persisted over three years. We show that short-term priority significantly increased the establishment success of' native perennial grasses. Increased density of native grass seedlings presaged later large increases in cover that were not evident in the first year after planting. Although priority effects at the individual level may diminish over time, short differences in emergence timing can have long-lasting effects on community structure. Earlier germination and faster initial growth of exotic annual species may help explain their unprecedented invasion and continued dominance of California grasslands. Finally, these results highlight the importance of priority effects for effective exotic annual control during native grassland restoration in California: initial control can increase the establishment of native perennial seedlings, which then results in long-term control by mature native individuals.

‘Rio Rojo’ Smooth‐Seeded Wild Bean, a Native Annual Forage Legume

Smooth‐seeded wild bean (Strophostyles leiosperma Torr. & A. Gray) is an herbaceous annual legume native to North America from Canada to Mexico. ‘Rio Rojo’ (Reg. No. CV‐295, PI 658217) was selected by Texas AgriLife Research and The Noble Foundation to fill the need for easily propagated, nutritious forage, and high seed producing native annual legumes in subhumid climates of the southern Great Plains. It was selected from germplasm collected in the wild for its vigor and forage and seed characteristics. Depending on climate and soil conditions, it can produce up to 3.9 Mg forage DM yr−1 ha−1 and over 800 kg seed ha−1 yr−1. Rio Rojo will be ideal for those seeking native annual legume germplasm for wildlife plantings or in native grassland restoration efforts.

Consequences of Prescribed Fire and Grazing on Grassland Ant Communities

Prescribed fire and livestock grazing are used for the management and restoration of native grasslands the world over; however, the effects of these management techniques on ant communities are unclear. We examined the response of ants to these disturbances in grasslands in northern California. Twenty-four 30 by 30 m plots were established across two sites that received one of four treatments: grazing, fire, grazing and fire, or no treatment. Ants were censused using 240 pitfall traps with one preburn and two postburn samples (14 d and 1 yr after burning). We analyzed ant abundance using broadly defined groups based on feeding habit and/or habitat use and detected no grazing effect but a significant fire effect that differed by group. Immediate postfire sampling showed an increase in cryptic species (particularly Brachymyrmex depilis). One year after the fire, no response was detected for cryptic species, but burned plots had greater abundance of seed harvesters. Analysis of vegetation showed burned plots had significantly greater forb cover, which might have provided greater food resources, and also lower biomass, which might have facilitated foraging. Understanding the effects of these management tools on ant abundance complements our understanding of their effect on vegetation and assists conservation practitioners effectively manage grassland ecosystems both in California and beyond.

Grasshopper Herbivory Affects Native Plant Diversity and Abundance in a Grassland Dominated by the Exotic Grass Agropyron cristatum

Abstract The indirect effects of native generalist insect herbivores on interactions between exotic and native grassland plants have received limited attention. Crested wheatgrass (Agropyron cristatum) is the most common exotic rangeland grass in western North America. Crested wheatgrass communities are resistant to colonization by native plant species and have strong competitive effects on native species, imposing problems for the restoration of native grasslands. Grasshoppers are generalist herbivores that are often abundant in Crested wheatgrass–dominated sites in the northern Great Plains. We conducted two experiments in a Crested wheatgrass–dominated grassland in western North Dakota to test the hypothesis that grasshopper herbivory influences local Crested wheatgrass community composition by impeding native seedlings. Grasshopper herbivory negatively affected the species richness, abundance, and Shannon diversity of native plants in 3 of 4 years. Although additional research is needed to determine if grasshoppers actively select native plants, the effects of grasshopper herbivory may be an important consideration in the restoration of Crested wheatgrass areas. Our findings illustrate the importance of understanding the impact of native generalist invertebrate herbivores on the relationships between exotic and native plants.

Climatic variability alters the outcome of long‐term community assembly

Summary We used seed additions to test experimentally whether long‐term community assembly unfolds consistently (deterministic model) or whether different outcomes are possible depending on variations in climate and the presence of exotic dominants (stochastic model). The experiment was conducted in homogeneous semi‐arid grassland on the northern Great Plains of North America. Native grass seed additions in each of 3 years (1994–96) were combined factorially with repeated selective herbicide applications to reduce the cover of the extant dominant, a Eurasian C3 grass (Agropyron cristatum). We assessed whether composition converged or diverged among treatments between 1996 and 2004. The outcome of long‐term community assembly varied by establishment year, in association with significant variations in monthly growing‐season precipitation from 68‐year averages during the years when seed was added. In 2004, the added native C4 grass Bouteloua gracilis dominated plots sprayed and seeded in 1994 and 1995, resisting re‐invasion and having significantly higher plot diversity. In contrast, plots sown in 1996 – one of the driest years on record – reverted to the exotic C3 grass. Seeded but unsprayed plots maintained their pre‐treatment dominance by exotic grass. Rainfall variability was also associated with the extent of exotic grass cover and bare soil in unsprayed plots, and natural recruitment by native species from nearby prairie. Establishment success varied significantly among the added species. All seeded grasses, other than B. gracilis, were mostly absent by 2004. The failure of these native C3 species to establish appears consistent with deterministic assembly models where local abiotic conditions filter out unsuitable species. Synthesis. Our results indicate that stochastic and deterministic processes operate simultaneously to influence community assembly, depending on interactions among climate, seed availability, species identity and disturbance during the initial stages of establishment. Multiple assembly trajectories developed, but the assembled communities did not include all the added species. Conversion of degraded grassland back to native‐dominated grassland was possible, but only with the removal of the exotic dominant and seed additions during years that were suitably wet for establishment. Once formed, however, the assembled native community resisted re‐invasion. This suggests that native grassland restoration will depend on establishment measures as intense as those used during initial cultivation almost a century earlier.

Plant Community Response to the Decline of Diffuse Knapweed in a Colorado Grassland

Long-term reductions in invasive plant species are few, and studies documenting the response of plant communities to such reductions are equally rare. We quantified plant species richness and cover during a nine-year period at a grassland site in central Colorado where the introduction of biological control insects reduced the invasive non-native forb diffuse knapweed (Centaurea diffusa). This reduction opened up 25 percent of the relative plant cover for other plant species. Based upon repeated inventories of plant species from four transects at the site we found no changes in native or nonnative plant species richness. Although we documented a modest increase from 2.4 percent to 8.6 percent in the relative cover of native forbs as knapweed declined, we observed no significant shifts in the relative cover of total native and total non-native vegetation. Two introduced grasses, field brome (Bromus arvensis [= B. japonicus]) and intermediate wheatgrass (Thinopyrum intermedium) showed significant increases. Native warm- and cool-season grasses at the site were unable to exploit the vacuum left by the decline of the knapweed. We found little evidence of native grassland restoration following the reduction of a non-indigenous, invasive plant. Our findings support the conclusion that the reduction of a regionally abundant, non-native plant species alone is not sufficient to promote restoration of the formerly dominant native plant species, and that further management activities are necessary.

Seed Resources for Temperate Native Grassland Restoration

Seed Resources for Temperate Native Grassland Restoration

INFLUENCE OF LAND USE ON POSTMETAMORPHIC BODY SIZE OF PLAYA LAKE AMPHIBIANS

Agricultural land use may indirectly affect the body size of amphibians by altering the hydroperiods of nearby wetlands and influencing amphibian densities—both factors which can limit the larval and postmetamorphic growth rates of amphibians. We measured postmetamorphic body size for 4 species (Spea multiplicata, S. bombifrons, Bufo cognatus, Ambystoma tigrinum mavortium) and 3 age classes (metamorph, subadult, adult) of amphibians captured at playa wetlands surrounded by one of 2 general land-use types (cultivation, grassland) in the Southern High Plains. Sixteen playas (4 per land-use type in 1999 and 2000) were partially enclosed with drift fence and pitfall traps, and mass and snout-vent length (SVL) were measured from a subsample of captured individuals. Mass and SVL were 10–148% greater for amphibians captured at grassland wetlands than at cropland wetlands for most species and age classes. Mass and SVL also were 3–124% greater in 1999 than in 2000 for most species and age classes. We attribute differences in body size between land-use types to differences in the hydroperiods of the associated wetlands, and potentially to variation in the density of terrestrial conspecifics and aquatic predators. We attribute differences in body size between years to differences in rainfall. Body size is positively related to the probability of survival, reproduction, and evolutionary fitness in amphibians. Thus, if cultivation of landscapes surrounding wetlands negatively influences postmetamorphic body size of amphibians, restoration of native grasslands surrounding playa wetlands may help prevent local amphibian declines.

Geographic races may exist among perennial grasses

California's native perennial grasses have been largely replaced by alien annuals. Interest in restoration of native grasslands is strong, but genetic differences among the available collections of some grasses may affect the survival of plantings and remnant native stands. In collections of the four native grasses examined, differences in phenology, growth form and forage quality suggest the existence of geographic races.