Diane M. Debinski

Life-history traits predict species responses to habitat area and isolation: a cross-continental synthesis

There is a lack of quantitative syntheses of fragmentation effects across species and biogeographic regions, especially with respect to species life-history traits. We used data from 24 independent studies of butterflies and moths from a wide range of habitats and landscapes in Europe and North America to test whether traits associated with dispersal capacity, niche breadth and reproductive rate modify the effect of habitat fragmentation on species richness. Overall, species richness increased with habitat patch area and connectivity. Life-history traits improved the explanatory power of the statistical models considerably and modified the butterfly species-area relationship. Species with low mobility, a narrow feeding niche and low reproduction were most strongly affected by habitat loss. This demonstrates the importance of considering life-history traits in fragmentation studies and implies that both species richness and composition change in a predictable manner with habitat loss and fragmentation.

A remote sensing and GIS-based model of habitats and biodiversity in the Greater Yellowstone Ecosystem

We used remotely sensed data and geographical information systems (GIS) to categorize habitats, then determined the relationship between remotely sensed habitat categorizations and species distribution patterns. Three forest types and six meadow types in the Greater Yellowstone Ecosystem, USA, were classified using Landsat TM data. All plant species with 5% cover or greater, 31% of the butterfly species, and 20% of the bird species exhibited significant differences in distribution among meadow types. Sites of highest species richness coincided for plants, birds, and butterflies and were found in mesic meadows.

Connecting Soil Organic Carbon and Root Biomass with Land-Use and Vegetation in Temperate Grassland

Soils contain much of Earths 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.

Assessing alternative futures for agriculture in Iowa, U.S.A

The contributions of current agricultural practices to environmental degradation and the social problems facing agricultural regions are well known. However, landscape-scale alternatives to current trends have not been fully explored nor their potential impacts quantified. To address this research need, our interdisciplinary team designed three alternative future scenarios for two watersheds in Iowa, USA, and used spatially-explicit models to evaluate the potential consequences of changes in farmland management. This paper summarizes and integrates the results of this interdisciplinary research project into an assessment of the designed alternatives intended to improve our understanding of landscape ecology in agricultural ecosystems and to inform agricultural policy. Scenario futures were digitized into a Geographic Information System (GIS), visualized with maps and simulated images, and evaluated for multiple endpoints to assess impacts of land use change on water quality, social and economic goals, and native flora and fauna. The Biodiversity scenario, targeting restoration of indigenous biodiversity, ranked higher than the current landscape for all endpoints (biodiversity, water quality, farmer preference, and profitability). The Biodiversity scenario ranked higher than the Production scenario (which focused on profitable agricultural production) in all endpoints but profitability, for which the two scenarios scored similarly, and also ranked higher than the Water Quality scenario in all endpoints except water quality. The Water Quality scenario, which targeted improvement in water quality, ranked highest of all landscapes in potential water quality and higher than the current landscape and the Production scenario in all but profitability. Our results indicate that innovative agricultural practices targeting environmental improvements may be acceptable to farmers and could substantially reduce the environmental impacts of agriculture in this region.

Species diversity and the scale of the landscape mosaic : do scales of movement and patch size affect diversity

Abstract We use a combination of a model and empirical data to examine the relationship between the scale of the landscape mosaic and individual movement patterns on the measurement of local butterfly species diversity. In landscapes where patch sizes are smaller, the type of patch adjacent to the patch surveyed can influence both local species richness and incidence. In landscapes composed of larger patches, adjacency has no effect on species richness or incidence. We hypothesize that the mechanism for species enrichment is the potential for movement of individuals between habitats, resulting in either (a) spillover of species from the higher-diversity patches into other habitats, or (b) habitat sampling by species that benefit from the resources in adjacent patches. In order to determine whether landscape configuration alone can account for the observed patterns of diversity, we employ a simulation model. Simulation results suggest that both specialist and generalist butterflies can sample a much more diverse array of habitat types in a more fine-grained landscape.

A comparison of satellite data and landscape variables in predicting bird species occurrences in the Greater Yellowstone Ecosystem. USA

We compare the accuracy of predicting the occurrence of 11 bird species in montane meadows of the Greater Yellowstone National Park ecosystem, in the states of Montana and Wyoming, USA. We used remotely sensed, landscape, and habitat data. The meadow type, as determined from the remotely sensed data, was highly correlated with abundances of six of the 11 bird species. Landscape variables significant in predicting occurrence were selected using a stepwise multiple regression for each bird species. These variables were then used in a multiple regression with the variable meadow type. As expected, the abundances of the generalist species (American Robin, Dark-eyed Junco, White-crowned Sparrow, Brewers Blackbird, and Chipping Sparrow) were not strongly correlated with landscape variables or meadow type. Conversely, abundances of the Common Snipe, Common Yellowthroat, Lincolns Sparrow, Savannah Sparrow, Vesper Sparrow, and Yellow Warbler were highly correlated with meadow type and landscape variables such as percent cover of willow (Salix spp.), graminoid, woody vegetation, sagebrush (Artemisia spp.), and graminoid and shrub biomass. The results from our study indicate that remotely sensed data are applicable for estimating potential habitats for bird species in the different types of montane meadows. However, to improve predictions about species in specific sites or areas, we recommend the use of additional landscape metrics and habitat data collected in the field.

Using Biodiversity Data to Assess Species-Habitat Relationships in Glacier National Park, Montana

Biodiversity surveys are becoming increasingly popular. However, standard analysis techniques for these data have not yet been developed. This paper explores the use of multivariate ordination techniques for assessing species—habitat relationships using biodiversity data. The research was conducted in Glacier National Park, Montana, and birds and butterflies were chosen as the taxonomic groups of study. Biodiversity assessment sites were established throughout a range of habitats and monitored from 1987 through 1989. Presence/absence sampling over the total number of sampling sites was used to classify species commonness and rarity. Approximately 86% of the historically recorded butterflies and 70% of the historically recorded bird species have been observed in the 3 yr of sampling. During the 3 yr of this study there was a striking continuity of species richness per site. There was also a striking overlap between sites that support high species diversity and sites that support rare species. Principal components analysis and cluster analysis worked well in discerning species—habitat relationships. Elevation, structural diversity of the site, and moisture were the major factors explaining species distributions. A chi—square analysis also provided some insights into species—habitat relationships, showing birds were more habitat specific than butterflies. Habitat diversity analyses demonstrated a positive but nonsignificant correlation between remotely sensed spectral—class diversity of a site and species richness for both birds and butterflies. Aspect, slope, and elevation diversity had a negative or negligible relationship with species richness.

Genetic diversity assessment in a metapopulation of the butterfly Euphydryas gillettii

Abstract Euphydryas gillettii is a Rocky Mountain endemic butterfly distributed in small, widely separated populations, which appear to be declining. This paper presents the results of a genetic diversity assessment within and among E. gillettii colonies comprising the Glacier National Park (GNP) metapopulation. Four colonies were assayed within GNP during 1988 and 1989, and two outgroups, colonies from Idaho and Wyoming, were also compared with GNP populations for allelic uniqueness and heterogeneity. Differences between the 1988 and 1989 data suggest that E. gillettii may exist as a biennial population. Minor differences were found among GNP populations while larger differences were found among Montana, Wyoming and Idaho populations. Heterozygosity was higher than expected, suggesting a potential selective advantage for heterozygotes. Heterozygosity was also found to be higher in populations that were distributed in a linear space along stream corridors relative to those in meadows. More research should be conducted with respect to dispersal along streams as it appears that these corridors may be significant in the maintenance of the metapopulation.

Survival, movement, and resource use of the butterfly Parnassius clodius

Abstract.  1. A mark–recapture study was conducted on the American Apollo butterfly Parnassius clodius Menetries during three field seasons (1998–2000) to examine its movement patterns over the course of a season within a sagebrush meadow in Grand Teton National Park, Wyoming, U.S.A. The study examined how resources affected butterfly distribution patterns and used mark–recapture data to gain insight into movement differences between sexes and over time.

Another tool in the toolbox? Using fire and grazing to promote bird diversity in highly fragmented landscapes

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.