Browsing by Author "Debinski, Diane M."

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Adapting the Fire-Grazing Interaction to Small Pastures in a Fragmented Landscape for Grassland Bird Conservation
(2016-07) Duchardt, Courtney J.; Miller, James R.; Debinski, Diane M.; Engle, David M.
In North America, the loss of habitat heterogeneity resulting from homogeneous livestock grazing is one factor contributing to steep population declines of many grassland bird species. Patch-burn grazing is a management technique that uses historic grassland disturbance as a model to create heterogeneous grassland composition and structure, providing for the diverse habitat requirements of grassland birds. Though this management technique has been used successfully in relatively extensive grasslands, its utility on smaller grassland patches is less clear. We examined the efficacy of patch-burn grazing to restore habitat heterogeneity and increase grassland bird diversity in relatively small pastures (15–32 ha) in a grassland landscape fragmented by cultivation and tree encroachment. In 2006, we established 12 experimental pastures in the Grand River Grasslands of southern Iowa and northern Missouri, with 4 pastures in each of three treatments: 1) patch-burn graze, with spatially discrete fires and free access by cattle (the fire-grazing interaction), 2) graze-and-burn, with free access by cattle and a single burn of the entire pasture every third year, and 3) burn-only, with a single burn of the entire pasture every third year and no grazing. Patch-burn grazing in the first phase of the project (2007–2009) did not generate habitat heterogeneity or significant differences in bird diversity. From 2010 to 2013, stocking rates were reduced to increase residual vegetation in unburned patches at the end of the grazing season to increase heterogeneity. Habitat heterogeneity in patch-burn graze pastures subsequently increased relative to other treatments. Concomitantly, diversity of obligate grassland birds also increased in patch-burn graze pastures and was greatest in 2012 and 2013. We conclude that the fire-grazing interaction can be used to restore habitat heterogeneity and increase grassland bird diversity, even in relatively small grassland patches embedded in a highly fragmented landscape.
Another Tool in the Toolbox? Using Fire and Grazing to Promote Bird Diversity in Highly Fragmented Landscapes
(2011-03) Pillsbury, Finn C.; Miller, James R.; Debinski, Diane M.; Engle, David M.
The grasslands of central North America have experienced drastic reductions in extent, removal of historic disturbance patterns, and homogenization of remaining fragments. This has resulted in steep declines for a broad swath of grassland biodiversity. Recent work in relatively extensive grasslands has demonstrated that mimicking historic disturbance patterns using a fire‐grazing interaction can increase the abundance and diversity of grassland birds through increased habitat heterogeneity. We examined the efficacy of this management strategy for promoting avian diversity in highly fragmented landscapes, which represent the bulk of remaining grassland bird habitats in the tallgrass prairie region. We quantified the population density of obligate and facultative grassland bird species along transects in 13 experimental research pastures in the Grand River Grasslands of Iowa and Missouri (USA), divided among three treatments: 1) spatially discrete fires and free access by cattle (“patch‐burn grazed”), 2) free access by cattle and a single complete burn (“grazed‐and‐burned”), and 3) a single complete burn with no cattle (“burned‐only”). We expected that patch‐burn grazing would produce a bird community that overlapped that of the grazed‐and‐burned and burned‐only treatments, because it would provide habitat for species associated with both. However, an analysis of similarity (ANOSIM) showed that community structure on pastures managed using patch‐burn grazing instead diverged significantly from both of the other treatments. Differences in community structure were most highly correlated with visual obstruction and wooded edge density in the landscape, suggesting bird communities are differentiated not only by their structural habitat requirements, but also by the varying degrees of sensitivity to landscape fragmentation of their component species. The future success of this management scheme for fragmented grasslands hinges on if, after an optimal stocking rate is identified, adequate habitat can be maintained for a diverse bird community, or whether fragmentation will perpetually limit the efficacy of this method in these landscapes.
Bee Abundance and Nutritional Status in Relation to Grassland Management Practices in an Agricultural Landscape
(2016-04) Smith, Griffin W.; Debinski, Diane M.; Scavo, Nicole A.; Lange, Corey J.; Delaney, John T.; Moranz, Raymond A.; Miller, James R.; Engle, David M.; Toth, Amy L.
Grasslands provide important resources for pollinators in agricultural landscapes. Managing grasslands with fire and grazing has the potential to benefit plant and pollinator communities, though there is uncertainty about the ideal approach. We examined the relationships among burning and grazing regimes, plant communities, and Bombus species and Apis mellifera L. abundance and nutritional indicators at the Grand River Grasslands in southern Iowa and northern Missouri. Treatment regimes included burn-only, grazed-and-burned, and patch-burn graze (pastures subdivided into three temporally distinct fire patches with free access by cattle). The premise of the experimental design was that patch-burn grazing would increase habitat heterogeneity, thereby providing more diverse and abundant floral resources for pollinators. We predicted that both bee abundance and individual bee nutritional indicators (bee size and lipid content) would be positively correlated with floral resource abundance. There were no significant differences among treatments with respect to bee abundance. However, some of the specific characteristics of the plant community showed significant relationships with bee response variables. Pastures with greater abundance of floral resources had greater bee abundance but lower bee nutritional indicators. Bee nutritional variables were positively correlated with vegetation height, but, in some cases, negatively correlated with stocking rate. These results suggest grassland site characteristics such as floral resource abundance and stocking rate are of potential importance to bee pollinators and suggest avenues for further research to untangle the complex interactions between grassland management, plant responses, and bee health.
Bees and Butterflies in Roadside Habitats: Identifying Patterns, Protecting Monarchs, and Informing Management
(ITD Reseach Program, 2023-07) Meinzen, Thomas C.; Debinski, Diane M.; Burkle, Laura A.; Ament, Robert J.
Pollinating insects provide vital ecosystem services and are facing global declines and habitat loss . Roadsides are increasingly regarded as important potential areas f or enhancing pollinator habitat. Understanding which roadsides best support pollinators — and why — is essential to helping locate and prioritize pollinator conservation efforts across roadside networks. To support this effort, we assessed butterfly, bee, and flowering plant species richness and abundance on a set of 63 stratified randomized roadside transects in State-managed rights-of-way in SE Idaho. Our research evaluated pollinator diversity as a function of highway class (interstate, U.S., and state highways), remotely sensed NDVI values (a measure of vegetation greenness), and floral resources. We found that smaller highways and lower (less green) maximum NDVI values were associated with significantly more bee species and total bees. Roadsides bordering sagebrush habitats typically had low NDVI values and higher bee and butterfly species richness, potentially contributing to this observed pattern. Butterfly richness increased in association with higher floral abundance in roadsides. Additionally, we identified and mapped 1,363 roadside patches of milkweed (Asclepias speciosa), larval host plant for the imperiled monarch butterfly (Danaus plexippus), in a survey of over 900 miles of southern Idaho highways. Based on these results and a literature review, we recommend management strategies to promote the health of pollinator populations in Idaho’s rights-of-way and provide data to help ITD prioritize areas for pollinator-friendly management practices and habitat restoration within their highway system.
Butterflies and Continuous Conservation Reserve Program Filter Strips: Landscape Considerations
(2006-11) Davros, Nicole M.; Debinski, Diane M.; Reeder, Kathleen F.; Hohman, William L.
Filter strips or buffers are areas of grass or other perennial herbaceous vegetation established along waterways to remove contaminants and sediments from agricultural field runoff. In the heavily cultivated regions of the Midwestern United States, these buffer zones established under the Farm Bill provide important habitat for wildlife such as butterflies. The question of how the landscape context of these plantings influences their use has not been adequately researched. We used multiple regression and Akaike's Information Criteria to determine how habitat width and several landscape‐level factors (i.e., landscape composition [total herbaceous cover, amount of developed area, and amount of wooded cover] and configuration [herbaceous edge density]) influenced the abundance and diversity of the butterfly community using filter strips in southwestern Minnesota, USA. Habitat‐sensitive butterfly abundance and all richness and diversity measures were positively correlated with filter‐strip width. Butterfly abundance was negatively associated with the amount of developed areas (cities, towns, and roads) within the area of a 1‐km radius (3.14 km2) surrounding the sites. Percentage of wooded cover in the landscape was an important variable explaining individual species abundance, although the direction of the relationship varied. Our finding that landscape context influences butterfly use of filter strips highlights the importance of landscape‐level approaches to wildlife conservation in agroecosystems.
Butterflies Like Wide Buffer Strips with Tall Native Grasses and
(2007-01) Debinski, Diane M.; Hohman, William L.
If you want more species of butterflies in your filter strips and other grass buffers, make the buffers wider and plant tall native grasses and broad leaf plants. That’s a key finding of a southwestern Minnesota study on butterfly use of conservation buffers.
Butterfly Responses to Prairie Restoration Through Fire and Grazing
(2007-11) Vogel, Jennifer A.; Debinski, Diane M.; Koford, Rolf R.; Miller, James R.
The development of land for modern agriculture has resulted in losses of native prairie habitat. The small, isolated patches of prairie habitat that remain are threatened by fire suppression, overgrazing, and invasion by non-native species. We evaluated the effects of three restoration practices (grazing only, burning only, and burning and grazing) on the vegetation characteristics and butterfly communities of remnant prairies. Total butterfly abundance was highest on prairies that were managed with burning and grazing and lowest on those that were only burned. Butterfly species richness did not differ among any of the restoration practices. Butterfly species diversity was highest on sites that were only burned. Responses of individual butterfly species to restoration practices were highly variable. In the best predictive regression model, total butterfly abundance was negatively associated with the percent cover of bare ground and positively associated with the percent cover of forbs. Canonical correspondence analysis revealed that sites with burned only and grazed only practices could be separated based on their butterfly community composition. Butterfly communities in each of the three restoration practices are equally species rich but different practices yield compositionally different butterfly communities. Because of this variation in butterfly species responses to different restoration practices, there is no single practice that will benefit all species or even all species within habitat-specialist or habitat-generalist habitat guilds.
Butterfly, bee and forb community composition and cross-taxon incongruence in tallgrass prairie fragments
(2008-02) Davis, Jessica; Hendrix, Stephen D.; Debinski, Diane M.; Hemsley, Chiara
Pollinators provide an important class of ecological services for crop plants and native species in many ecosystems, including the tallgrass prairie, and their conservation is essential to sustaining prairie remnants. In Iowa these remnants are typically either block-shaped or long, linear strips along transportation routes. In this study we examined differences in the butterfly, bee, and forb community composition in linear and block prairie remnants, determined correlations between species diversity among butterflies, bees and forbs in the 20 prairie remnants sampled, and examined correlations of community similarity among butterflies, bees and forbs. Correspondence analysis showed that distinct communities exist for butterflies and forbs in block versus linear sites and discriminant analysis showed that the bee and forb communities in block and linear sites can be distinguished on the basis of a few species. Diversity of one group was a poor predictor of diversity in another, except for a significant inverse relationship between bees and butterflies. These two pollinator taxa may be responding very differently to microhabitat components within fragmented ecosystems. Our studies show that there need to be differences in conservation strategies for bees and butterflies to maintain both pollinator communities.
Changes in Vegetation Structure through Time in a Restored Tallgrass Prairie Ecosystem and Implications for Avian Diversity and Community Composition
(2009-12) Olechnowski, Brian F.; Debinski, Diane M.; Drobney, Pauline; Viste-Sparkman, Karen; Reed, William T.
Grassland birds are one of the most endangered taxa in temperate North America. Because many species declines have been linked to habitat fragmentation and loss, large-scale prairie restoration projects have the potential to provide critical habitat for these declining species. We examined how the structure of restored grassland habitat changes through time and how diversity and community composition of grassland birds respond to these changes. Our study was completed at Neal Smith National Wildlife Refuge, a large-scale prairie restoration in central Iowa. Vegetation composition and structure were measured at 42 restored grassland plots throughout the refuge in 2007. Birds were surveyed at these locations from 1994 to 2007. Survey points were sorted into five categories (out of crop rotation for 1, 2, 3, 4–6, and > 6 y). In the initial phases of restoration, species such as horned larks, red-winged blackbirds, and killdeer were abundant. Other species such as common yellowthroats and dickcissels were more common in established restored points. Henslow’s sparrows appeared only at survey points that were out of crop rotation for more than 6 years. Diversity peaked in survey points that were 2–3 years out of crop rotation and points that were more than 6 years out of rotation. Community composition shifted through the chronosequence of prairie plantings. Changes in diversity and shifts in community composition can be explained by changes in vegetative structure. Our results suggest that managing for a variety of restored prairie stages will best maintain the highest levels of avian diversity and abundance.
Climate extremes, vegetation change, and de-coupling of interactive fire-grazing processes exacerbate fly parasitism of cattle
(2017-02) Scasta, John D.; Talley, Justin L.; Engle, David M.; Debinski, Diane M.
We assessed local horn fly (Haematobia irritans L.) and face fly (Musca autumnalis De Geer) communities on cattle in 2012 and 2013 relative to vegetation and climate data to understand how parasitism of cattle is influenced by change in climate and vegetation structure. We compared heterogeneity management using spatially and temporally discrete fires (i.e., patch-burning one-third of a pasture annually) to homogeneity management (i.e., burning entire pasture in 2012 then no burning in 2013), with cattle grazing all years in both treatments. Predicted emergence of horn flies and face flies was 24 and 34 d earlier in 2012 associated with earlier spring warming, a significant deviation from the five-year mean. Intraannual horn fly dynamics were explained by concurrent high ambient air temperature the day of observations, but face flies were explained by low ambient air temperatures and dry conditions 3 wk before observations. Importance values of information for the theoretic models including fire treatments ranged from 0.89 to 1, indicating that both horn flies and face flies are sensitive to habitat alterations and fire-driven animal movements. Ordination indicates herds on unburned pastures were dissimilar to herds on pastures burned with patchy fires or pastures burned completely and species-specific fly responses to different vegetation structure metrics. For example, horn flies were correlated with vegetation visual obstruction, and face flies were correlated with woody plant cover. Vegetation structure may be as important as climate in driving the dynamics of fly parasites of cattle.
Connecting Soil Organic Carbon and Root Biomass with Land-Use and Vegetation in Temperate Grassland
(2005-07) McGranahan, Devan A.; Daigh, A. L.; Veenstra, J. J.; Engle, David M.; Miller, James R.; Debinski, Diane M.
Soils contain much of Earth’s terrestrial organic carbon but are sensitive to land-use. Rangelands are important to carbon dynamics and are among ecosystems most widely impacted by land-use. While common practices like grazing, fire, and tillage affect soil properties directly related to soil carbon dynamics, their magnitude and direction of change vary among ecosystems and with intensity of disturbance. We describe variability in soil organic carbon (SOC) and root biomass—sampled from 0–170 cm and 0–100 cm, respectively—in terms of soil properties, land-use history, current management, and plant community composition using linear regression and multivariate ordination. Despite consistency in average values of SOC and root biomass between our data and data from rangelands worldwide, broad ranges in root biomass and SOC in our data suggest these variables are affected by other site-specific factors. Pastures with a recent history of severe grazing had reduced root biomass and greater bulk density. Ordination suggests greater exotic species richness is associated with lower root biomass but the relationship was not apparent when an invasive species of management concern was specifically tested. We discuss how unexplained variability in belowground properties can complicate measurement and prediction of ecosystem processes such as carbon sequestration.
Constraints to restoring fire and grazing ecological processes to optimize grassland vegetation structural diversity
(2016-10) Scasta, John D.; Duchardt, Courtney J.; Engle, David M.; Miller, James R.; Debinski, Diane M.; Harr, Ryan N.
Extirpation of the ecosystem engineer (bison) and its interaction with fire, coupled with the utilitarian concept of moderate grazing, have contributed to homogenization of grassland habitat in North America. Although cattle may serve as a proxy for bison, combining fire with cattle grazing has been uncommon and to date managers have not always successfully applied cattle and controlled burns as tools to manipulate grassland vegetation heterogeneity and increase habitat diversity. Using an information-theoretic approach, we assessed factors constraining the fire-grazing interaction ecological process to engineer habitat structure of grasslands via patch-burn grazing. We assessed how grazing, fire, and biotic and abiotic features in tallgrass prairie influenced establishment and maintenance of low vegetative structure in burned patches, the positive feedback driving the fire-grazing interaction, and subsequent structural heterogeneity across a pasture. Four pastures were divided into three patches with a different patch burned annually in March/April from 2007 to 2013. Cattle were stocked from light to heavy (1.1–4.4 AUM/ha) from May to October (∼150 days) with access to the entire pasture. We hypothesized that the exotic C3 grass tall fescue (Schedonorus arundinaceus), lag-time between burning date and the date cattle were put into experimental pastures, and burn date would be the constraining factors. However, the most informative model included stocking rate, date of burn completion, and precipitation. The lightest cattle stocking rate did not establish low vegetative structure in the burn patch, which resulted in the lowest heterogeneity among patches. The heaviest cattle stocking rate established but did not maintain low vegetative structure in the burn patch. The intermediate cattle stocking rate maintained the lowest vegetative structure in the burn patch and the greatest heterogeneity among patches, i.e., the best efficacy of patch-burn grazing to engineer habitat structural heterogeneity. The relationships of stocking rate to burn patch vegetative structure and to landscape heterogeneity were both quadratic and were both optimized at intermediate stocking rate.
A Cross-Taxonomic Comparison of Insect Responses to Grassland Management and Land-Use Legacies
(2011-12) Debinski, Diane M.; Moranz, Raymond A.; Delaney, John T.; Miller, James R.; Engle, David M.; Winkler, Laura B.; McGranahan, Devan A.; Barney, Robert J.; Trager, James C.; Stephenson, Andrew L.; Gillespie, Molly K.
Many species of plants and animals associated with grasslands are rare or declining due to habitat loss and degradation. Although grassland plants and insects evolved in the context of both grazing and fire, the appropriate use of grazing and fire has been debated among those concerned with protecting insect communities. We established an experiment to test insect responses to three grassland management treatments: (1) patch-burn graze (burning of spatially distinct patches and free access by cattle), (2) grazeand- burn (burning of entire tract with free access by cattle), and (3) burn-only. Because we expected that land-use legacies could also affect insect abundance and diversity, we evaluated effects of time since fire, grazing history, remnant history (remnant or reconstructed grassland) and pre-treatment vegetation characteristics, which were assumed to be a legacy of prior land-use. Butterflies (Lepidoptera), ants (Hymenoptera: Formicidae), and leaf beetles (Coleoptera: Chrysomelidae) were surveyed for three years to compare their responses to each of these treatments as measured by abundance, richness and species diversity. Each of these taxa is relatively diverse and was expected to have the potential to have strong negative responses to grazing and burning, but we predicted more positive responses to patch-burn grazing. Our results showed that land-use legacies affected insect abundance, richness and diversity, but treatments did not. Ant abundance was lower in tracts with a history of heavy grazing. Ant species richness was positively associated with pre-treatment time since fire and vegetation height and negatively associated with pre-treatment proportion native plant cover. Butterfly abundance was positively associated with pre-treatment litter cover. Leaf beetle diversity was positively associated with pre-treatment native plant cover, and leaf beetle abundance was negatively associated with time since fire. Our results indicate that land-use legacies can exert more influence on grassland insect community composition than current management, but the particular aspects of these land-use legacies that are important vary across insect taxa. The implications of these finding are that (1) land-use legacies should garner more attention in grassland management and (2) conservation of grassland insect communities will be improved by taxonspecific analysis of land-use legacy variables.
Earlier spring snowmelt drives arrowleaf balsamroot phenology in montane meadow
(Wiley, 2022-08) Durney, J. Simone; Engel, Arden; Debinski, Diane M.; Burkle, Laura A.
Climate change is shifting phenology globally, altering when and how species respond to environmental cues such as temperature and the timing of snowmelt. These shifts may result in phenological mismatches among interacting species, creating cascading effects on community and ecosystem dynamics. Using passive warming structures and snow removal, we examined how experimentally increased temperatures, earlier spring snowmelt, and the poorly understood interaction between warming and earlier spring snowmelt affected flower onset, flowering duration, and maximum floral display of the spring-flowering montane species, arrowleaf balsamroot (Balsamorhiza sagittata), over a 7-year period. Additionally, potential cumulative effects of treatments were evaluated over the study duration. The combination of heating with snow removal led to earlier flower onset, extended flowering duration, and increased maximum floral display. While there was year-to-year variation in floral phenology, the effect of heating with snow removal on earlier onset and maximum floral display strengthened over time. This suggests that short-term studies likely underestimate the potential for climate change to influence phenological plant traits. Overall, this research indicates that B. sagittata's flowering onset responded more strongly to snow removal than to heating, but the combination of heating with snow removal allowed plants to bloom earlier, longer, and more profusely, providing more pollinator resources in spring. If warming and early snowmelt cause similar responses in other plant species, these patterns could mitigate phenological mismatches with pollinators by providing a wider window of time for interaction and resiliency in the face of change. This example demonstrates that a detailed understanding of how spring-flowering plants respond to specific aspects of predicted climatic scenarios will improve our understanding of the effects of climate change on native plant–pollinator interactions in montane ecosystems. Studies like this help elucidate the long-term physiological effects of climate-induced stressors on plant phenology in long-lived forbs.
Earlier spring snowmelt drives arrowleaf balsamroot phenology in montane meadows
(Wiley, 2022-08) Durney, J. Simone; Engel, Arden; Debinski, Diane M.; Burkle, Laura A.
Climate change is shifting phenology globally, altering when and how species respond to environmental cues such as temperature and the timing of snowmelt. These shifts may result in phenological mismatches among interacting species, creating cascading effects on community and ecosystem dynamics. Using passive warming structures and snow removal, we examined how experimentally increased temperatures, earlier spring snowmelt, and the poorly understood interaction between warming and earlier spring snowmelt affected flower onset, flowering duration, and maximum floral display of the spring-flowering montane species, arrowleaf balsamroot (Balsamorhiza sagittata), over a 7-year period. Additionally, potential cumulative effects of treatments were evaluated over the study duration. The combination of heating with snow removal led to earlier flower onset, extended flowering duration, and increased maximum floral display. While there was year-to-year variation in floral phenology, the effect of heating with snow removal on earlier onset and maximum floral display strengthened over time. This suggests that short-term studies likely underestimate the potential for climate change to influence phenological plant traits. Overall, this research indicates that B. sagittata's flowering onset responded more strongly to snow removal than to heating, but the combination of heating with snow removal allowed plants to bloom earlier, longer, and more profusely, providing more pollinator resources in spring. If warming and early snowmelt cause similar responses in other plant species, these patterns could mitigate phenological mismatches with pollinators by providing a wider window of time for interaction and resiliency in the face of change. This example demonstrates that a detailed understanding of how spring-flowering plants respond to specific aspects of predicted climatic scenarios will improve our understanding of the effects of climate change on native plant–pollinator interactions in montane ecosystems. Studies like this help elucidate the long-term physiological effects of climate-induced stressors on plant phenology in long-lived forbs.
Effects of experimentally reduced snowpack and passive warming on montane meadow plant phenology and floral resources.
(2017-03) Sherwood, Jill A.; Debinski, Diane M.; Caragea, P. C.; Germino, Matthew J.
Climate change can have a broad range of effects on ecosystems and organisms, and early responses may include shifts in vegetation phenology and productivity that may not coincide with the energetics and forage timing of higher trophic levels. We evaluated phenology, annual height growth, and foliar frost responses of forbs to a factorial experiment of snow removal (SR) and warming in a high-elevation meadow over two years in the Rocky Mountains, United States. Species included arrowleaf balsamroot (Balsamorhiza sagittata, early-season emergence and flowering) and buckwheat (Eriogonum umbellatum, semi-woody and late-season flowering), key forbs for pollinator and nectar-using animal communities that are widely distributed and locally abundant in western North America. Snow removal exerted stronger effects than did warming, and advanced phenology differently for each species. Specifically, SR advanced green-up by a few days for B. sagittata to >2 wk in E. umbellatum, and led to 5- to 11-d advances in flowering of B. sagittata in one year and advances in bud break in 3 of 4 species/yr combinations. Snow removal increased height of E. umbellatum appreciably (~5 cm added to ~22.8 cm in control), but led to substantial increases in frost damage to flowers of B. sagittata. Whereas warming had no effects on E. umbellatum, it increased heights of B. sagittata by >6 cm (compared to 30.7 cm in control plots) and moreover led to appreciable reductions in frost damage to flowers. These data suggest that timing of snowmelt, which is highly variable from year to year but is advancing in recent decades, has a greater impact on these critical phenological, growth, and floral survival traits and floral/nectar resources than warming per se, although warming mitigated early effects of SR on frost kill of flowers. Given the short growing season of these species, the shifts could cause uncoupling in nectar availability and timing of foraging.
Effects of grassland management practices on ant functional groups in central North America
(2013-08) Moranz, Raymond A.; Debinski, Diane M.; Winkler, Laura B.; Trager, James C.; McGranahan, Devan A.; Engle, David M.; Miller, James R.
Tallgrass prairies of central North America have experienced disturbances including fire and grazing for millennia. Little is known about the effects of these disturbances on prairie ants, even though ants are thought to play major roles in ecosystem maintenance. We implemented three management treatments on remnant and restored grassland tracts in the central U.S., and compared the effects of treatment on abundance of ant functional groups. Management treatments were: (1) patch-burn graze—rotational burning of three spatially distinct patches within a fenced tract, and growing-season cattle grazing; (2) graze-and-burn—burning entire tract every 3 years, and growing-season cattle grazing, and (3) burn-only—burning entire tract every 3 years, but no cattle grazing. Ant species were classified into one of four functional groups. Opportunist ants and the dominant ant species, Formica montana, were more abundant in burn-only tracts than tracts managed with either of the grazing treatments. Generalists were more abundant in graze-and-burn tracts than in burn-only tracts. Abundance of F. montana was negatively associated with pre-treatment time since fire, whereas generalist ant abundance was positively associated. F. montana were more abundant in restored tracts than remnants, whereas the opposite was true for subdominants and opportunists. In summary, abundance of the dominant F. montana increased in response to intense disturbances that were followed by quick recovery of plant biomass. Generalist ant abundance decreased in response to those disturbances, which we attribute to the effects of competitive dominance of F. montana upon the generalists.
Effects of Tall Fescue and Its Fungal Endophyte on the Development and Survival of Tawny-Edged Skippers (Lepidoptera: Hesperiidae)
(2016-02) Jokela, Karin J.; Debinski, Diane M.; McCulley, Rebecca L.
Invasive, exotic grasses are increasing in tallgrass prairie and their dominance may be contributing to the decline of grassland butterflies through alterations in forage quality. Tall fescue ( Schedonorus arundinaceus (Schreb.) Dumort.), an exotic grass covering millions of acres in the United States, can host a fungal endophyte, Epichloë coenophiala (Morgan-Jones & Gams). Alkaloids produced by the endophyte are known to be toxic to some foliar-feeding pest insects. Endophyte-infected tall fescue is commonly planted in hayfields, pastures, lawns, and is invading natural areas, but effects of the endophyte on nonpest insects such as butterflies are relatively unknown. Our objective was to investigate the role that tall fescue and its endophyte might play in the decline of grass skippers (Hesperiidae). We examined growth and survival parameters of tawny-edged skippers ( Polites themistocles (Latreille)) that were reared on endophyte-infected tall fescue (E+), endophyte-free tall fescue (E−), and Kentucky bluegrass (KBG). KBG was included as a comparison because it is a cool season grass known to be palatable to P. themistocles larvae. Interestingly, results showed that the endophyte did not affect growth and survival of larvae compared to uninfected tall fescue, even though significant amounts of loline alkaloids (average 740 ppm) were measured in endophyte-infected plant material. Larvae feeding on KBG grew faster with greater survival rates than larvae on both tall fescue treatments. These results confirm that tall fescue invasion and dominance may be deteriorating the quality of grassland habitats for native pollinators; however, this effect does not appear to be linked to endophyte infection.
Epigaeic Ant Communities Along a Soil Moisture Gradient in Grand Teton Montane Meadows
(2008-01) Robinson, Wayne A.; Debinski, Diane M.
Climate change has become a major concern for scientists and resource managers across the globe. Whilst there is much speculation about the pending magnitude of the changes and their ecological effects, there is an urgent and undeniable need to have sound ecological monitoring programs in place in sensitive areas. Montane meadows in the Greater Yellowstone Ecosystem (GYE) are inhabited by short-lived plants and highly mobile animal species that can exhibit quick changes in distribution patterns relative to environmental changes (Debinski et al. 2000, Debinski et al. 2002). Thus, they can provide an early warning system for other ecosystems across the globe. Currently, the extent and range of climatic changes that will occur in montane meadows are unknown.
Evaluating Native Bee Communities and Nutrition in Managed Grasslands
(2020-06) Stein, D. S.; Debinski, Diane M.; Pleasants, John M.; Toth, Amy L.
Native pollinators are important for providing vital services in agroecosystems; however, their numbers are declining globally. Bees are the most efficient and diverse members of the pollinator community; therefore, it is imperative that management strategies be implemented that positively affect bee community composition and health. Here, we test responses of the bee and flowering plant communities to land management treatments in the context of grasslands in the upper Midwestern United States, a critical area with respect to bee declines. Twelve sites were selected to examine floral resources and wild bee communities based on three different types of grasslands: tallgrass prairie remnants, ungrazed restorations, and grazed restorations. Total bee abundance was significantly higher in ungrazed restorations than remnants, but there were no significant differences among grasslands in community composition or Shannon diversity. Across the three grassland types we also examined mass and lipid stores as nutritional health indicators in three sweat bees (Halictidae), Augochlora pura, Agapostemon virescens, and Halictus ligatus. Although there were no differences in lipid content, total average bee mass was significantly higher in Ag. virescens collected from ungrazed restorations as compared to remnants. Floral abundance of native and non-native species combined was significantly higher in grazed restorations compared to remnants and ungrazed restorations. However, ungrazed restorations had higher abundance and richness of native flowering ramets. These data suggest that bee abundance and nutrition are driven by high abundance of native flowering plant species, rather than total flowering plants.