John R. Tester

Old‐Field Succession on a Minnesota Sand Plain

Vegetation and soils were sampled in 22 old fields ranging in age from 1 to 56 yr since abandonment. Soil nitrogen concentration increased significantly with field age. Vegetation cover, total aboveground plant biomass, and litter cover increased significantly with soil nitrogen. Light penetration to the soil surface was negatively correlated with total plant biomass. Field age and soil nitrogen concentration were used as independent variables in simple regression and partial correlation analyses to determine the relative importance of such time-dependent processes as dispersal vs. the availability of a limiting resource (nitrogen) as predictors of patterns in species richness or the abundance of various plant groups. Species richness per field and within-field heterogeneity in species composition increased with field age. Local species richness decreased with increasing soil nitrogen. Cover of annuals and introduced species decreased with field age and nitrogen; however, annuals contributed an important part of total vegetative cover even in 25-yr-old fields. Cover of perennials and woody species increased with soil nitrogen and field age. Although the fields were bordered by woods, woody species contributed <15?/o cover even in the oldest fields. For several plant groups the relationship between cover and soil nitrogen within individual fields was the opposite of that among all fields. These patterns suggest that while soil nitrogen is an important determinant of local species composition and abundance, dispersal and colonization, which are dependent on field age, determine which species are present in a field.

Consequences of habitat loss and fragmentation for wetland amphibian assemblages

Landscape-level variables operating at multiple spatial scales likely influence wetland amphibian assemblages but have not been investigated in detail. We examined the significance of habitat loss and fragmentation, as well as selected within-wetland conditions, affecting amphibian assemblages in twenty-one glacial marshes. Wetlands were located within urban and agricultural regions of central and southwestern Minnesota, USA and were distributed across two ecoregions: tallgrass prairie and northern hardwood forest. We surveyed amphibian assemblages and used a geographic information system to quantify land-use variables at three scales: 500, 1000, and 2500 m. Ten species of amphibians were detected, the most abundant beingRana pipiens, Ambystoma tigrinum, andBufo americanus. Amphibian species richness was lower with greater wetland isolation and road density at all spatial scales in both ecoregions. Amphibian species richness also had a negative relationship with the proportion of urban land-use at all spatial scales in the hardwood forest ecoregion, and species richness was greater in wetlands with fish andAmbystoma tigrinum. These biotic relationships are less consistent and more difficult to interpret than are land-use relationships. The data presented here suggest that decreases in landscape connectivity via fragmentation and habitat loss can affect amphibian assemblages, and reversing those landscape changes should be an important part of a regional conservation strategy.

Pocket gophers (Geomys bursarius), vegetation, and soil nitrogen along a successional sere in east central Minnesota

SummaryPocket gophers (Geomys bursarius: Geomyidae Rodentia) are shown to affect soil resources and thus, indirectly, vegetation. Gophers reduce average soil nitrogen near the surface and increase point-to-point heterogeneity of soil nitrogen by moving nitrogen-poor subsurface soil to the soil surface. Data from 22 old fields at Cedar Creek Natural History Area, Minnesota, USA show correlations of soil nitrogen, vegetation, and gopher mounds that are consistent with this indirect mechanism by which gophers affect local species composition and old field succession.

Path Selection by Peromyscus leucopus in the Presence and Absence of Vegetative Cover

We examined path selection and avoidance by tracking Peromyscus leucopus marked with fluorescent powder in Minnesota and Maryland. Mice at both sites selected logs > 5 cm in diameter and avoided logs < 5 cm in diameter. In Minnesota, two types of soft log, smooth and mossy, were strongly selected, and hard, smooth logs were avoided. Mice selected forb cover and avoided grass cover in Minnesota and selected bare ground and avoided leaf cover in Maryland. The same pathways were used repeatedly in Maryland, but not in Minnesota. Individual P. leucopus appear to restrict their movements to paths that offer protection from predators searching by sight or sound

Automatic Radio-Tracking System for Monitoring Animal Movements

The effects of physical and biological factors on the activity patterns and movements of animals are of major interest to biologists. Much speculation has arisen on the stimuli for specific motile responses. However, published reports on the influence of physical and biotic factors in the environment on activity patterns and movement are relatively infrequent and usually treat the subject qualitatively rather than quantitatively. This report describes an automatic radio-tracking system designed to provide quantitative data on animal behavior under natural conditions.

The importance of local and regional factors in predicting effective conservation Planning strategies for wetland bird communities in agricultural and urban landscapes

Wetland assessment techniques have generally focused on rapid evaluations of local and site impacts; however, wetland biodiversity is often influenced both by adjacent and regional land use. Forty wetlands were studied in the Red River Valley (RRV), Southwest Prairie (SWP), and the Northern Hardwood Forest (NHF) ecoregions of Minnesota, USA, to assess the strength of association between local and landscape condition and avian community composition. We examined the relationship between bird assemblages and local and landscape factors (connectedness, isolation, road density, and site impacts). Landscape variables were calculated for three spatial scales at 500 m (79 ha), 1000 m (314 ha), and 2500 m (1963 ha). Connectedness and road density are important measures for predicting bird assemblages in both agricultural ecoregions (SWP and RRV). Connectedness and its relationship with wetland bird assemblages were most pronounced at the larger scale (2500 m), where the largest remnant patches can be discerned. In contrast, road effects on bird assemblages were most pronounced at the smallest scale (500 m). Wetland isolation corresponded to bird community patterns as well, but only in one ecoregion (SWP). In the urbanizing ecoregion (NHF), species richness was considerably lower than elsewhere but community patterns did not correspond to landscape variables. The focus of wetland conservation planning needs to shift from the site scale to the landscape scale to ensure that connection with the regional wetland pattern is accounted for, therefore, affording the best opportunity to successfully maintain wetland avian diversity.

Seasonal Weight Changes, Mortality, and Population Structure of Raccoons in Minnesota

A population of raccoons ( Procyon lotor ) in east-central Minnesota was studied from September 1964 through October 1966. Sixty-three individuals were radio-tagged, and an automatic tracking system monitored their presence in the population for 3367 raccoon days for yearlings and adults and 3518 days for juveniles. Data are presented on weight loss and mortality in this population. Juveniles, yearlings, and adults lost about half their weight during winter dormancy, and many juveniles died from starvation and parasitism, the most important mortality factors in this relatively unhunted population. Late winter and early spring were the most critical periods for juveniles. Limited data on population structure indicated an even ratio of yearlings to adults and an even sex ratio in yearlings and adults, although there was a heavy bias toward males in a sample of 20 raccoons born on the study area in 1965.

HABITAT USE AND HOME RANGE OF MALLARDS BREEDING IN MINNESOTA

Telemetry techniques were used to study habitat use and home range of 12 drake and 12 hen mallards (Anas platyrhynchos) in the forested region of north-central Minnesota during the 1968 to 72 breeding seasons. Circumneutral bogs and seasonal wetlands were the most frequently used communities; the lakeshore communities most used were sand-gravel, overhanging brush, and bog mat. Based on the availability of habitat, the highest preference shown was for the seasonal community and the least for the softwood swamp; however, all communities were used to some extent during the breeding season. Lakeshore was always among the habitats most frequently used by pairs. Twelve nests were found, nine in nonpermanent wetlands and three in upland forest sites. Mean home range was 210 ha for hens and 240 ha for drakes. The long axis of the home ranges of drakes and hens averaged 2.8 and 2.7 km, respectively. Hens had smaller home ranges during the laying period (anti x = 70 ha) than during prenesting (anti x = 135 ha).

Development of community metrics to evaluate recovery of Minnesota wetlands

Monitoring wetland recovery requires assessment tools that efficiently and reliably discern ecosystem changes in response to changes in land use. The biological indicator approach pioneered for rivers and streams that uses changes in species assemblages to interpret degradation levels may be a promising monitoring approach for wetlands. We explored how well metrics based on species assemblages related to land use patterns for eight kinds of wetlands in Minnesota. We evaluated land use on site and within 500 m,1000 m, 2500 m and 5000 m of riverine, littoral, and depressional wetlands (n = 116) in three ecoregions. Proportion of agriculture, urban, grassland, forest,and water were correlated with metrics developed from plant, bird, fish, invertebrate, and amphibian community data collected from field surveys. We found79 metrics that relate to land use, including five that may be useful for many wetlands: proportion of wetland birds, wetland bird richness, proportion of insectivorous birds, importance of Carex, importance of invasive perennials. Since very few metrics were significant for even one-half of the wetland types surveyed, our data suggest that monitoring recovery in wetlands with community indicators will likely require different metrics,depending on type and ecoregion. In addition, wetlands within extensively degraded ecoregions may be most problematic for indicator development because biotic degradation is historic and severe.

Pathological Responses of Red Foxes to Capture in Box Traps

We documented the physiological responses of captive-raised red foxes (Vulpes vulpes) to capture in box (i. e., live) traps. The behavior of captured foxes was video recorded, and heart rate and body temperature were monitored via radio telemetry throughout an 8-hour restraint period. Endocrine, biochemical, hematological, and pathological samples were collected. Responses of foxes caught in box traps were compared to the responses reported by Kreeger at al. (1990c) for untrapped (i.e., control) foxes and foxes caught in padded- and unpadded-jaw foothold traps. Heart rate and body temperature increased after foxes were caught in box traps, but never significantly exceeded mean pretrapped levels. Foxes caught in box traps were physically active for 35.7±8.8 (SE)% of the restraint period. The majority of this activity consisted of pacing in the trap. Foxes caught in box traps had higher (P<0.003) adrenocorticotropin and cortisol values than untrapped foxes, and lower (P<0.001) β-endorphin and cortisol levels than foxes caught in foothold traps. Bilirubin, alkaline phosphatase, lactate dehydrogenase, and aspartate aminotransferase levels for foxes caught in box traps were elevated (P<0.01) above levels of untrapped foxes. Foxes caught in box traps had lower (P<0.004) alkaline phosphatase, lactate dehydrogenase, creatine kinase, and aspartate aminotransferase levels than foxes caught in foothold traps. Because foxes caught in box and padded-jaw foothold traps had no limb damage, the observed biochemical differences between animals caught in these traps were likely due to psychogenic factors associated with limb restraint and differences in the intensity of exertion (i.e., pacing vs. digging). Hematological profiles of foxes caught in box traps or foothold traps were similar, but trapped foxes had higher (P<0.01) leukocyte counts and significant neutrophilia and lymphopenia compared to untrapped foxes. The gross and histopathological findings for foxes caught in box and foot hold traps were generally similar. Foxes caught in box traps had higher (P<0.05) incidences of adrenal and renal congestion and lung hemorrhage than did untrapped foxes. We conclude that factors associated with limb restraint directly contribute to the trauma experienced by trapped red foxes and, therefore, foxes caught in box traps undergo less trauma than foxes that are restrained by a limb in a padded- or unpadded-jaw foothold trap