Christine A. Ribic

Comparison of riparian plant communities under four land management systems in southwestern Wisconsin

Riparian plant community composition is influenced by moisture, erosion, original native plant communities, and current and past land use. This study compared riparian plant communities under four types of management: woody buffer strip, grassy buffer strip, rotational grazing, and continuous grazing. Study sites were located along spring-fed streams in the unglaciated region of southwestern Wisconsin, USA. At each site, plant community surveys were conducted using a point transect method. Among the treatments, woody buffer strips, rotationally grazed and continuously grazed riparian areas had greater plant species richness than grassy buffer strips, and woody buffer strips had the greatest native plant species richness. Reed canarygrass (Phalaris arundinacea L.) was prevalent in grassy buffer strips (44% of all observations), common in woody buffer strips (15%), and rare in sites that were rotationally or continuously grazed (3 and 5%, respectively). Pasture sites had greater proportions of native grasses and grass relatives and moderate levels of overall native species richness. Considered a water quality best management practice, well-managed rotational grazing may be a reasonable alternative to buffer strips which can contribute to protection and enhancement of native vegetation biodiversity.

Comparative effectiveness of Longworth and Sherman live traps

Abstract Despite the widespread use of Sherman (H. B. Sherman Inc., Tallahassee, Flor.) and Longworth (Penlon Ltd., Oxford, U.K.) live traps in small-mammal-community assessment, few studies have directly compared the effectiveness of these 2 popular models. This study compared the relative efficacy of both trap types in capturing small mammals in southern Wisconsin grasslands. As trap size may cause capture bias, we compared Longworth traps with equal numbers of small and large, folding Sherman traps. We also deployed a small number of pitfalls. We carried out trapping at 12 sites over a 2-year period (1996–1997). We observed a significant year effect, so we analyzed differences in capture success, species diversity indices, and percent community similarity between trap types separately for each year. Two-way contingency table analyses indicated that all 3 trap types exhibited species-specific differences in capture rates. We assessed standardized deviates for each cell within this two-way design, and we considered departures greater than 2 standard deviations (SE±1.96) from the mean to show an either significantly positive (≥ + 1.96) or significantly negative (≤−1.96) association. In the first year, Longworth traps captured greater numbers of long-tailed shrews (Sorex spp.) whereas small Sherman traps captured more western harvest mice (Reithrodontomys megalotis) and white-footed or prairie deer mice (Peromyscus spp.). In the second year, small Sherman captures were greater for long-tailed shrews and western harvest mice while large Sherman traps captured more meadow voles (Microtus pennsylvanicus) and jumping mice (Zapus hudsonius). Although estimates of community diversity were similar between trap types, percent community similarity estimates were lowest for Longworth-Sherman trap comparisons. Mortality rates were highest for Longworth traps and small Sherman traps and lowest for large Sherman traps. Pitfalls caught proportionally more long-tailed shrews than conventional live traps in the first but not the second year of study. In general, body mass of the animal had little effect on trap capture rates. However, in the first year of this study, small Sherman traps caught lighter (P =0.028) long-tailed shrews than the large Sherman traps. Similarly, Longworth traps caught significantly lighter white-footed/prairie deer mice than either small (P=0.022) or large (P= 0.035) Shermans. When used in combination, both Longworth and Sherman traps can diminish overall sampling error and yield less biased estimates of species composition than either trap type alone. The use of new as opposed to used Sherman traps in the second year of this study might account for the greater capture efficacy of these traps and contribute to differences in relative trap type success between years.

Trends in marine debris along the U.S. Pacific Coast and Hawai’i 1998–2007

We assessed amounts, composition, and trends of marine debris for the U.S. Pacific Coast and Hawaii using National Marine Debris Monitoring Program data. Hawaii had the highest debris loads; the North Pacific Coast region had the lowest debris loads. The Southern California Bight region had the highest land-based debris loads. Debris loads decreased over time for all source categories in all regions except for land-based and general-source loads in the North Pacific Coast region, which were unchanged. General-source debris comprised 30-40% of the items in all regions. Larger local populations were associated with higher land-based debris loads across regions; the effect declined at higher population levels. Upwelling affected deposition of ocean-based and general-source debris loads but not land-based loads along the Pacific Coast. LNSO decreased debris loads for both land-based and ocean-based debris but not general-source debris in Hawaii, a more complex climate-ocean effect than had previously been found.

A sampling design framework for monitoring secretive marshbirds

Abstract. n A framework for a sampling plan for monitoring marshbird populations in the contiguous 48 states is proposed here. The sampling universe is the breeding habitat (i.e. wetlands) potentially used by marshbirds. Selection protocols would be implemented within each of large geographical strata, such as Bird Conservation Regions. Site selection will be done using a two-stage cluster sample. Primary sampling units (PSUs) would be land areas, such as legal townships, and would be selected by a procedure such as systematic sampling. Secondary sampling units (SSUs) will be wetlands or portions of wetlands in the PSUs. SSUs will be selected by a randomized spatially balanced procedure. For analysis, the use of a variety of methods as a means of increasing confidence in conclusions that may be reached is encouraged. Additional effort will be required to work out details and implement the plan.

Relationship of Obligate Grassland Birds to Landscape Structure in Wisconsin

Abstract Conservation plans for grassland birds have included recommendations at the landscape level, but species responses to landscape structure are variable. We studied the relationships between grassland bird abundances and landscape structure in 800-ha landscapes in Wisconsin, USA, using roadside surveys. Of 9 species considered, abundances of only 4 species differed among landscapes with varying amounts of grassland and forest. Landscape variables explained <20% of variation in abundances for 4 of the 5 rarest species in our study. Our results suggest landscape-based management plans for grassland birds might not benefit the rarest species and, thus, plans should incorporate species-specific habitat preferences for these species.

Strategic Grassland Bird Conservation throughout the Annual Cycle: Linking Policy Alternatives, Landowner Decisions, and Biological Population Outcomes

Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds.