Restoration Efforts for Plant and Bird Communities in Tallgrass Prairies Using Prescribed Burning and Mowing

Recent losses and fragmentation of tallgrass prairie habitat to agriculture and urban development have led to corresponding declines in diversity and abundance of plants and birds associated with such habitat. Mowing and burning are alternative management strategies for restoring and rejuvenating prairies in fragmented landscapes, but their specific, comparative effects are the subjects of ongoing evaluation. We compared the responses of plant and bird communities on four sets of mowed, burned, and untreated sites of small (3–10 ha), fragmented tallgrass prairies at the DeSoto National Wildlife Refuge (DNWR), Iowa, U.S.A., during May–July in 1998 and 1999. Species richness and diversity of plants, resident grassland birds, and communities of birds associated with grassland edges (edge species) were independent of treatment. Although not affecting species richness and diversity in plant communities, mowed sites ranked lower in total plant coverage and total forb coverage than burned sites or untreated sites. In contrast, untreated sites had more coverage by shrubs, suggesting that mowing and burning did retard shrub encroachment. Overall, abundance and diversity of plants and birds were generally insensitive to management strategies. Small, fragmented sites of rare habitat may not respond in the short term to management treatments and may not be capable of supporting highly diverse communities, no matter how intensively manipulated. It is more probable that diversity of native prairie communities can be enhanced and restored only through long‐term efforts, acquisition of large land units capable of supporting stable populations, and deliberate reintroduction of species of high conservation value.     

Flower visitor communities are similar on remnant and reconstructed tallgrass prairies despite forb community differences

One common goal of habitat restoration and reconstruction is to reinstate the biodiversity found at intact reference sites. However, few researchers have examined whether these practices reinstate communities of flower‐visiting insects. This is unfortunate, as anthropogenically mediated declines in flower visitors, including bees (the primary pollinators for most terrestrial ecosystems), beetles, flies, and butterflies, have been reported worldwide. Biodiversity declines may be especially severe in North America's tallgrass prairie, a once‐vast grassland that has experienced severe destruction and degradation due to agricultural conversion. As such, we assessed the structure of forb and flower‐visiting insect communities as a whole and two subsets of the flower visitor community—bees and phytophagous beetles—across five tallgrass prairie remnants and five reconstructed prairies (former crop fields) in Kansas from 2013 to 2015. Remnant prairies had significantly higher forb diversity and differed significantly in forb composition, compared to reconstructed prairies. Despite the dissimilarities in forb community structure, there were no differences in flower visitor diversity or abundance between remnants and reconstructed prairies. However, when considered separately, bee communities exhibited significantly greater variability in composition on reconstructed prairies, likely due to the abundance of generalist bee species visiting non‐native legumes at two reconstructed prairies. Our work provides evidence that prairie habitat reconstruction is a valuable tool for reestablishing flower‐visiting insect communities and also emphasizes the considerable role that non‐native species may play in structuring grassland plant–bee interactions.     

Differences in ground beetles (Coleoptera: Carabidae) of original and reconstructed tallgrass prairies in northeastern Iowa, USA, and impact of 3-year spring burn cycles

Ground beetle assemblages were monitored at four tallgrass prairie sites burned on 3-year cycles in northeastern Iowa. The objectives of this study were to quantify differences in carabid communities between original and reconstructed tallgrass prairies, and to determine the responses of ground beetles to 3-year cycles of early spring fire commonly used to manage tallgrass prairies. Using pitfall traps, ground beetle assemblages in two original and two reconstructed tallgrass prairies were compared between 1994 and 1998, where beetles were sampled annually (0-, 1-, and 2-year post-fire conditions) from plots burned every 3 years. When burned, the greatest abundance, activity density, and species richness of carabid beetles occurred the year immediately following a spring burn, with abundance declining steadily with increased time since burning. Overall ground beetle diversity as determined by Shannon's diversity index was greatest in original tallgrass prairies several years after a fire. Some species of ground beetles were found only in original prairies, while others were found primarily in reconstructed prairie. Similarly, some species were more abundant the year immediately following a burn, while others were found in greater abundance with increased time since fire. NMS ordination and indicator species analysis clearly show differences in carabid species between original and reconstructed tallgrass prairies, but did not show differences among burn treatments.     

Effects of urbanization on site occupancy and density of grassland birds in tallgrass prairie fragments

Tallgrass prairies are among the most threatened ecosystems in the world. Remaining prairies tend to be small and isolated and many are associated with urban and suburban landscapes. We asked how urbanization might impact the conservation value of tallgrass prairie fragments for grassland birds by comparing the densities and the probability of occurrence of Dickcissels (Spiza americana), Grasshopper Sparrows (Ammodramus savannarum), and Eastern Meadowlarks (Sturnella magna) across 28 grasslands surrounded by low, moderate, and high levels of urbanization. We employed a hierarchical model selection approach to ask how variables that describe the vegetation structure, size and shape of grasslands, and urbanization category might explain variation in density and occurrence over two breeding seasons. Occurrence of all three species was explained by a combination of vegetation and patch characteristics, though each species was influenced by different variables and only Eastern Meadowlark occurrence was explained by urbanization. Abundance of all three species was negatively impacted by urbanization, though vegetation variables were also prevalent in the best‐supported models. We found no evidence that vegetation structure or other patch characteristics varied in a systematic way across urbanization categories. Although our results suggest that grassland bird density declines with urbanization, urban tallgrass prairies still retain conservation value for grassland birds because of the limited availability of tallgrass prairie habitat and the limited impact of urbanization on species occurrence.     

Impact of prescribed burning on endophytic insect communities of prairie perennials (Asteraceae: Silphium spp.)

Prescribed burning currently is used to preserve endemicity of plant communities in remnant tallgrass prairies. Although some types of arthropods benefit from changes in plant communities brought about by burning, other species that are endemic to prairies may be threatened. Because they inhabit the fuel layer of prairies, endophytic insects would seem particularly susceptible to this management tactic. In this paper, we assess the impact of prescribed burning on endophytic insect communities inhabiting stems of Silphium laciniatum L. and S. terebinthinaceum Jacquin (Asteraceae), endemic prairie plants. Populations of these insects were decimated by burning, with mortality approaching 100% in most cases. Their populations nevertheless began to rebound within a single growing season, with densities moderately but significantly reduced 1 year after the burn. Even when a prairie remnant was completely incinerated, plant stems were recolonized by insects within one growing season. Our findings suggest that sufficient numbers of endophytic insects survive burns in remains of Silphium to recolonize burned areas the following year.     

Bee communities (Hymenoptera: Apoidea) of small Iowa hill prairies are as diverse and rich as those of large prairie preserves

Natural small, xeric hill prairies in forested landscapes throughout the Midwest United States often contain high diversity and unique species of some organisms because of their unusual landscape context and microclimate. We measured the diversity, richness, and abundance of the bee communities of five hill prairies located in northeastern Iowa and we compared these to values for large prairie preserves in northwestern Iowa, using a Monte Carlo resampling approach to standardize sampling effort between habitat types. We also measured the diversity and richness of the flowering forb communities at the hill prairies and we quantified percentage of the landscape at a 1 km radius in different landscape elements. Bee diversity at the five hill prairies spanned the range of diversity values for large prairies preserves, so although the hill prairies are small (<5 ha), their bee communities are not uniformly depauparate compared to larger western prairie preserves. Bee diversity was significantly related to flowering forb diversity, and may have been influenced by landscape features within 1 km—particularly the percentage of agricultural row crops and open water, which may negatively affect bee diversity at the sites. Iowa’s hill prairie bee communities were largely composed of widespread eastern species, although about 10% of the bee species have more northern or western ranges and appear to be taking advantage of the region’s unique habitat features. Given the dependence of the bee communities on the plant diversity of the sites, management of the plant community to maintain its diversity will also likely benefit bee diversity.     

Fire Frequency and Mosaic Burning Effects on a Tallgrass Prairie Ground Beetle Assemblage

Fire frequency has significant effects on the biota of tallgrass prairie, including mammals, vascular plants and birds. Recent concern has been expressed that widespread annual burning, sometimes in combination with heavy livestock grazing, negatively impacts the biota of remaining prairie remnants. A common management recommendation, intended to address this problem, is to create a landscape with a mosaic of different burn regimes. Pitfall trapping was used to investigate the impacts of fire pattern on the diversity and species composition of ground beetles (Coleoptera: Carabidae) at Konza Prairie Biological Station in eastern Kansas, USA. Trapping was conducted over three seasons in landscape units burned on average every 1, 4, or 20 years, and in a fourth season across the available range of vegetative structure to assess the variability of the community within the study system. In the fifth season communities were also followed immediately after two fire events to detect within-season effects of fire and to study short-term patterns of post-disturbance community assembly. Fire frequency had comparatively minimal effects on ground beetle diversity measures, and most numerically common species were observed widely across habitat and management types. Fire frequency effects were manifested primarily in changes in abundance of common species. Colonization of burned areas apparently did not occur from juxtaposed non-burned areas, but from underground or from long distances. While these results suggest that widespread annual burning of tallgrass prairie remnants may not have dramatic effects on prairie ground beetles, we urge caution regarding the application of these results to other taxa within tallgrass prairie.     

The influence of fire on Illinois hill prairie Auchenorrhyncha (Insecta: Hemiptera) diversity and integrity

Prescribed burning has been important in maintaining the structure of plant communities in the tallgrass prairie. However, implementation of these burn regimes often overlooks responses of other taxa, particularly arthropods. In this study, the timing and frequency of burns were examined on one of the most diverse and abundant groups of herbivorous insects, Auchenorrhyncha. These insects are ideal candidates in understanding the effects of fire on prairie arthropods because they are among the most numerous invertebrate herbivores in the prairie and they have ecological characteristics that confer a wide range of responses to prescribed burning. A total of 19 Illinois hill prairies were sampled along the Mississippi and Sangamon Rivers in the summer of 2006 using a modified leaf-blower vacuum. These sites exhibited a wide range of burn management, from unburned to recently burned, and having been burned multiple times. Species richness, Auchenorrhyncha Quality Index (with and without abundance data) and the mean coefficient of conservatism (with and without abundance data) were calculated for each site. Results suggest that unburned sites supported the greatest number of species and had higher Auchenorrhyncha Quality Index and mean coefficient of conservatism values than sites undergoing burn management. In order for land managers to maintain the prairie Auchenorrhyncha community and conserve vascular plants, this study recommends infrequent rotational burning with a minimum of 3?C5?years; although additional studies are needed to determine the appropriate number of years between each burn.     

Effects of fire on bird diversity and abundance in an East African savanna

Fire is an important determinant of many aspects of savanna ecosystem structure and function. However, relatively little is known about the effects of fire on faunal biodiversity in savannas. We conducted a short‐term study to examine the effects of a replicated experimental burn on bird diversity and abundance in savanna habitat of central Kenya. Twenty‐two months after the burn, Shannon diversity of birds was 32% higher on plots that had been burned compared with paired control plots. We observed no significant effects of burning on total bird abundance or species richness. Several families of birds were found only on plots that had been burned; one species, the rattling cisticola (Cisticola chiniana), was found only on unburned plots. Shrub canopy area was negatively correlated with bird diversity on each plot, and highly correlated with grass height and the abundance of orthopterans. Our results suggest that the highest landscape‐level bird diversity might be obtained through a mosaic of burned and unburned patches. This is also most likely to approximate the historical state of bird diversity in this habitat, because patchy fires have been an important natural disturbance in tropical ecosystems for millennia.     

Responses of breeding birds in tallgrass prairie to fire and cattle grazing

ABSTRACT.   No other group of North American birds has declined as precipitously and over so large an area as has the grassland assemblage. In the Flint Hills of Kansas, the largest extant region of tallgrass prairie, annual spring burning of rangeland has largely replaced traditional regimes and natural patterns with longer intervals between burns. I examined effects of burning and low-intensity cattle grazing on abundances of seven bird species at Konza Prairie Research Natural Area in June 2002 and 2003. Every species was affected by fire, with Upland Sandpipers ( Bartramia longicauda ) more abundant, and six species—Grasshopper Sparrow ( Ammodramus savannarum ), Henslow's Sparrow ( A. henslowii ), Dickcissel ( Spiza americana ), Eastern Meadowlark ( Sturnella magna ), Brown-headed Cowbird ( Molothrus ater ), and Bell's Vireo ( Vireo bellii )—either less abundant or absent at sites in the breeding season following a fire. These results demonstrate that annual burning limits the potential of much of the Flint Hills prairie to harbor high breeding densities of many grassland birds. On the other hand, I found a trade-off between immediate and longer-term effects of burning for several grass-dependent species. Grasshopper Sparrows, Henslow's Sparrows, and Eastern Meadowlarks, although more numerous in areas that were not burned the preceding spring, were less abundant at sites burned every 4 yrs than those burned at shorter intervals. In contrast, shrub-dependent Bell's Vireos were more abundant at sites burned every 4 yrs. Upland Sandpipers, Grasshopper Sparrows, and Eastern Meadowlarks were more abundant in grazed areas. Use of alternatives to annual burning could increase habitat heterogeneity by transforming the Flint Hills into a mosaic of regularly, but asynchronously, burned pastures that would better meet the diverse habitat needs of the region's grassland birds.     

Effects of habitat fragmentation and black-tailed prairie dogs on urban avian diversity

Urbanization and habitat fragmentation have the potential to influence bird communities. In addition, these phenomena, as well as ongoing lethal control measures, have also greatly reduced the range of the black-tailed prairie dog (Cynomys ludovicianus) since the beginning of the 20th century. Although prairie dogs are highly interactive species that can influence avian communities, few studies have investigated whether these interactions persist in urban settings. Our goal was to investigate the relative impacts of habitat fragmentation and prairie dogs on bird communities within an urban matrix. We performed bird surveys on 20 habitat fragments (10 colonized by prairie dogs, 10 uncolonized by prairie dogs) distributed throughout the Denver metropolitan area, and calculated Shannon–Weiner diversity and richness of all birds and native species, as well as total counts of grassland birds and raptors. Diversity, richness, and counts of many species increased with increasing fragment connectivity, and decreased on fragments isolated for longer periods of time. Avian diversity and richness did not differ between fragments with and without prairie dogs, suggesting that this element of the ecological role of prairie dogs is not fully retained in urban habitat. Future studies of the role of prairie dogs as keystone species in urban systems should include other taxa as well as consider the influence of the urban matrix surrounding prairie dog habitat. Our results emphasize that conservation of urban avian diversity should focus on landscape connectivity as well as local habitat features.     

The Role of Seed and Vegetative Reproduction in Plant Recruitment and Demography in Tallgrass Prairie

Recruitment, establishment and survivorship of seed- and vegetatively-derived shoots were quantified biweekly in annually burned and infrequently burned tallgrass prairie to investigate the contributions of seed and vegetative reproduction to the maintenance and dynamics of tallgrass prairie plant populations, the demography of seedlings and ramets, and the influence of fire on the demography of grasses and forbs. Clonally produced grass and forb ramets comprised >99%of all established shoots present at the end of the growing season, whereas established seedlings accounted for <1%,emphasizing the rarity of successful seedling establishment and the importance of vegetative reproduction in driving the annual regeneration and dynamics of aboveground plant populations in tallgrass prairie. Most recruitment from vegetative reproduction occurred early in the growing season and was higher in annually burned than infrequently burned sites, although low levels of new stem recruitment occurred continuously throughout the growing season. Peak recruitment on annually burned prairie coincided with peak recruitment of the dominant C₄ grasses Andropogon gerardii and Sorghastrum nutans prior to prescribed spring fire, with a second peak in recruitment occurring following fire. On infrequently burned prairie, grass and forb recruitment was highest in early April and declined steadily through May. The naturalized C₃ grass, Poa pratensis, was responsible for most of the early recruitment on unburned sites, whereas A. gerardii contributed most to recruitment later in May. Infrequently burned prairie was dominated by these two grasses and contained a larger forb component than annually burned prairie. The principal demographic effect of fire was on ramet natality rather than mortality. Fire regime, plant functional group, or timing of cohort emergence before or after fire did not affect ramet survivorship. C₄ grass shoots that emerged early and were damaged by fire showed similar survivorship patterns to tillers that emerged after fire. Differences in species composition between annually burned and infrequently burned prairie are driven by fire effects on vegetative reproduction and appear to be related principally to the effect of fire and detritus accumulation on the development of belowground vegetative meristems of C₄ grasses and their emergence dynamics.     

Patterns of Plant Species Diversity in Remnant and Restored Tallgrass Prairies

To restore diversity of native vegetation, we must understand factors responsible for diversity in targeted communities. These factors operate at different spatial scales and may affect the number and relative abundances of species differently. We measured diversity of plant species and functional groups of species in replicated plots within paired restored and remnant (relic) tallgrass prairies at three locations in central Texas, U.S.A. To determine the contributions of species abundances and of spatial patterns of diversity to differences between prairie types, we separated diversity into richness and evenness (relative biomass) and into within‐plot (α), among‐plot (β), and prairie (γ) components. Species diversity was greater in remnant than in restored prairies at all spatial scales. At the γ scale, both species richness and species evenness were greater in remnants because of greater spatial variation in species composition. At the α scale, remnants were more diverse because of greater richness alone. Mean α richness correlated positively with the size of the species pool in restored prairies only, implying that in remnants, α richness was influenced more by colonization dynamics than by the number of species available for colonization. Plots in remnant prairies contained more functional groups and fewer species per group than did plots in restored prairies, suggesting that resource partitioning was greater in relic prairies. Our results are consistent with the interpretation that local ecological processes, like resource partitioning and limitations on seed dispersal, contribute to the greater diversity of remnant than restored prairies in central Texas. Restoration practices that limit abundances of competitive dominants, increase the number of species in seed mixtures, and increase the proximity of plants of different functional groups thus may be required to better simulate the plant diversity of tallgrass prairies.     

Influence of late season fire on early successional vegetation of an Oklahoma prairie

Abstract. The study of vegetation dynamics in tallgrass prairie in response to fire has focused on dormant season fire in late successional prairies. Our objective was to determine if late season fire of varying frequency results in divergent successional patterns in an early successional tallgrass prairie disturbed by grazing and cultivation. Specifically, we evaluated the influence of late‐summer fires of varying frequency on community composition and species richness. We collected vegetation and environmental data on two sites burned in the late growing‐season at varying frequencies. These communities differed in composition depending primarily on edaphic factors, time since the last burn, and year‐to‐year variation. We interpret the time effect as related to changes in species composition accompanying plant succession that followed disturbance either from cropping and heavy grazing on the loamy site or heavy grazing on the shallow site. Other unidentified factors also have a role in vegetation dynamics on this prairie. Community composition and species richness were not consistently responsive to frequency of growing‐season fires.     

Positive effects of nitric oxide on Solanum lycopersicum

How plant communities are structured, and the relative roles of gradients and disturbances in that structuring, has long been of interest. Here I use plots in replicate tallgrass, mixedgrass, and shortgrass prairies across Northern Oklahoma to address this issue by sampling plant percent cover three years after applying treatments realizing common prairie disturbances of burning, grazing, and soil turnover. I found (1) shortgrass plots had the least amount of aboveground biomass (AGB), with burning and soil turnover plots also having low AGB in the other two prairies, (2) tallgrass plots had the most total cover, with soil turnover plots having the least in the other two prairies, (3) tallgrass plots had the most species, with soil turnover plots having the least in the other two prairies, (4) control plots in mixedgrass had the smallest evenness and plots in shortgrass had the highest, and (5) a high degree of functional similarity in all three prairies. In addition to controlling these different aspects of population and community structure in prairies, results also show that the most severe disturbances can lead to a prairie plant composition and structure more similar to that found in the drier, most western prairie areas.     

High Plant Richness in Prairie Reconstructions Support Diverse Leafhopper Communities

A primary reason for restoring plant communities is to increase biodiversity to previous levels. It is expected that restoring land with greater plant diversity will increase biodiversity at higher trophic levels, but high diversity seed mixes are expensive. In this study, we used one insect family, leafhoppers (Hemiptera: Cicadellidae) to assess the difference in leafhopper communities that result from establishing high compared with low plant richness restorations. We tested the hypotheses that: (1) the added effort of a high richness restoration leads to measurable increases in both diversity and richness of leafhoppers; and (2) that leafhopper community composition is more similar to remnant prairies in high richness than in low plant richness restorations. We found that higher plant richness led to 3‐ to 7‐fold increases in leafhopper and prairie‐dependent leafhopper diversity and richness in restorations. Leafhopper communities in high richness restorations were not more similar to remnant prairies, rather they were distinct among high and low richness restorations and prairie interior. Leafhopper richness and diversity correlated with plant richness, and leafhopper community composition differed among plant community assemblages, but not with the occurrence of single plant species. For our sites, species‐rich restorations provided better quality habitat for leafhoppers that was comparable to remnant prairie. Our results suggest that restorations with high plant species richness better support animal food webs.     

Endophytic insect communities of two prairie perennials (Asteraceae: Silphium spp.)

Little is known of the biology of most insects that are endemic to prairie ecosystems of North America, with the exception of large and conspicuous species. In particular, species that are sequestered within plant tissues are commonly overlooked. In this paper, we assess the biodiversity of endophytic insects that inhabit stems of Silphium laciniatum L. and S. terebinthinaceum Jacquin (Asteraceae), endemic plants of tallgrass prairies. Endophytic herbivores, gall wasps Antistrophus rufus Gillette and A. minor Gillette (Hymenoptera: Cynipidae) and stem-boring larvae of the beetle Mordellistena aethiops Smith (Coleoptera: Mordellidae) were attacked by 10 species of natural enemies. We report new host plant associations for herbivores, and new host insect associations for parasitoids. The two plant species differed significantly in their densities of gall wasps and the vertical dispersion of galls within stems. Interactions within and between trophic levels attest to the biodiversity of endophytic insect communities, and the specialized nature of these insects suggests they are highly vulnerable to habitat conservation practices that involve destruction of dead vegetation.     

Recovery of Native Plant Community Characteristics on a Chronosequence of Restored Prairies Seeded into Pastures in West‐Central Iowa

Restored grasslands comprise an ever‐increasing proportion of grasslands in North America and elsewhere. However, floristic studies of restored grasslands indicate that our ability to restore plant communities is limited. Our goal was to assess the effectiveness of restoration seeding for recovery of key plant community components on former exotic, cool‐season pastures using a chronosequence of six restoration sites and three nearby remnant tallgrass prairie sites in West‐Central Iowa. We assessed trends in Simpson's diversity and evenness, richness and abundance of selected native and exotic plant guilds, and mean coefficient of conservatism (mean C). Simpson's diversity and evenness and perennial invasive species abundance all declined with restoration site age. As a group, restoration sites had greater richness of native C₃ species with late phenology, but lower richness and abundance of species with early phenology relative to remnant sites. Total native richness, total native abundance (cover), mean C, and abundance of late phenology C₃ plants were similar between restoration and remnant sites. Observed declines in diversity and evenness with restoration age reflect increases in C₄ grass abundance rather than absolute decreases in the abundance of perennial C₃ species. In contrast to other studies, restoration seeding appears to have led to successful establishment of tallgrass prairie species that were likely to be included in seeding mixtures. While several floristic measures indicate convergence of restoration and remnant sites, biodiversity may be further enhanced by including early phenology species in seeding mixes in proportion to their abundance on remnant prairies.     

Host plant species effects on arbuscular mycorrhizal fungal communities in tallgrass prairie

Symbiotic associations between plants and arbuscular mycorrhizal (AM) fungi are ubiquitous in many herbaceous plant communities and can have large effects on these communities and ecosystem processes. The extent of species-specificity between these plant and fungal symbionts in nature is poorly known, yet reciprocal effects of the composition of plant and soil microbe communities is an important assumption of recent theoretical models of plant community structure. In grassland ecosystems, host plant species may have an important role in determining development and sporulation of AM fungi and patterns of fungal species composition and diversity. In this study, the effects of five different host plant species [Poa pratensis L., Sporobolus heterolepis (A. Gray) A. Gray, Panicum virgatum L., Baptisia bracteata Muhl. ex Ell., Solidago missouriensis Nutt.] on spore communities of AM fungi in tallgrass prairie were examined. Spore abundances and species composition of fungal communities of soil samples collected from patches within tallgrass prairie were significantly influenced by the host plant species that dominated the patch. The AM fungal spore community associated with B. bracteata showed the highest species diversity and the fungi associated with Pa. virgatum showed the lowest diversity. Results from sorghum trap cultures using soil collected from under different host plant species showed differential sporulations of AM fungal species. In addition, a greenhouse study was conducted in which different host plant species were grown in similar tallgrass prairie soil. After 4 months of growth, AM fungal species composition was significantly different beneath each host species. These results strongly suggest that AM fungi show some degree of host-specificity and are not randomly distributed in tallgrass prairie. The demonstration that host plant species composition influences AM fungal species composition provides support for current feedback models predicting strong regulatory effects of soil communities on plant community structure. Differential responses of AM fungi to host plant species may also play an important role in the regulation of species composition and diversity in AM fungal communities. Received: 29 January 1999 / Accepted: 20 October 1999     

Exotic-Dominated Grasslands Show Signs of Recovery with Cattle Grazing and Fire

In grasslands, overgrazing by domestic livestock, fertilization, and introduction of exotic forage species leads to plant communities consisting of a mixture of native and exotic species. These degraded grasslands present a problem for land managers, farmers, and restoration ecologists concerned with improving biodiversity while continuing to use the land for livestock production. Here we assessed the response of butterfly and plant community composition to the use of fire and moderate grazing by domestic cattle on degraded grasslands dominated by exotic plants. We evaluated change by comparing experimental pastures to two reference sites that were grasslands dominated by native plants. We used two burning and grazing treatments: 1) patch-burn graze, a heterogeneously managed treatment, where one third of the pasture is burned each year and cattle have free access to the entire pasture, and 2) graze-and-burn, a homogenously managed treatment, where the entire pasture is grazed each year and burned in its entirety every three years. We tested for change in the butterfly and plant community composition over seven years using Bray-Curtis dissimilarity measures. Over the course of seven years, degraded pastures in both treatments became more similar to reference sites with respect to the butterfly and plant communities. Only two butterfly species and two plant functional guilds exhibited significant linear trends over time, with varying responses. Compositional changes in both the butterfly and plant communities indicate that the use of moderate grazing and fire may shift butterfly and plant communities of exotic-dominated grasslands to be more similar to reference tallgrass prairies over time.