Highlight: The importance of several plant communities for summer cattle range was evaluated. Based on understory production, eight communities were separated into three groups, i.e., bunchgrass, forested, and clearcutforested. Forested communities that had been clearcut and seeded to forage were the most productive. Soil depth and canopy cover were dominant environmental factors determining understory production on the study area. These two variables accounted for 96% of the variability in understory production. Clearcut forested communities seeded to forage provided 63% of the forage consumed by cattle and made up 31% of the study area. Seeded grasses accounted for 55% of the cattle diet. Environmental factors highly correlated with utilization by cattle during the summer were distance to salt and water, soil depth, and canopy cover. Relations of soil depth and canopy cover were a result of their influence on plant growth. There appeared to be no direct forage competition between big game and cattle when livestock were present during the last half of summer.

methods

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Wildlife Management Techniques

Cattle use on summer foothill rangelands in northeastern Oregon.

Composition, Structure, and Dynamics of Mixed-Species Foraging Aggregations in a Southern New Jersey Salt Marsh

We mounted a video camcorder in a single-engine aircraft to estimate nesting density along 10-m wide strip transects in black brant (Branta bernicla nigricans) colonies on the Yukon Delta National Wildlife Refuge, Alaska during 1990-1992. A global positioning system (GPS) receiver was connected to the video recorder and a laptop computer to locate transects and annotate video tape with time and latitude-longitude at 1-second intervals. About 4-5 hours of flight time were required to record 30-40 minutes of video tape needed to survey large (>5,000 nests in ?10 km2) colonies. We conducted ground searches along transects to locate and identify nests for determining detection rates of nests in video images. Counts of nests from video transects were correlated with actual numbers of nests. Resolution of images was sufficient to detect 81 % of known nests (with and without incubating females). Of these, 68% were correctly identified as brant nests. The most common misidentification of known nests was failure of viewers to see the nest that the detected bird was incubating. Unattended nests with exposed eggs, down-covered nests, and nesting brant, cackling Canada geese (Branta canadensis minima), and emperor geese (Chen canagica) were identified in video images. Flushing of incubating geese by survey aircraft was not significant. About 10% of known nests were unoccupied in video images compared to 16% unoccupied nests observed from tower blinds during periods without aircraft disturbance.

Estimating populations of nesting brant using aerial videography

— The relationships between vegetative and edaphic habitat factors and the local distribution and abundance of small mammals on Malheur National Wildlife Refuge, Harney County, Oregon, were examined between July 1973 and June 1975. Of 16 species of small mammals captured, deer mice {Peromyscus maniculatus), montane voles {Microttts montanus). Great Basin pocket mice {Perognathus parvus), and least chipmunks {Eutamias minimus) comprised 90.1 percent of the individuals. The physiognomy of the vegetation was a factor in the distribution of rodent species other than deer mice. Pocket mice and chipmunks were restricted to the communities dominated by sagebrush (Artemisia tridentata) or greasewood (Sarcobatus vermiculatus). Population densities of pocket mice and chipmunks were significantly related to edaphic factors such as soil depth, texture, and strength, which may have affected the construction and stability of burrows. Montane voles occurred only in marsh or grassland communities. Population densities of voles were directly correlated with the amount of cover and inversely correlated with its patchiness. Deer mice were the most common species encountered and occurred in all but the grassland communities. The density of this species was related to vegetative or edaphic factors only seasonally or in certain habitats, and few generalizations could be made. The general habitat preferences of many species of small mammals have been documented by several generations of natural historians, and often can be attributed to food preferences and associated morphological adaptations (Baker 1971). Many other extrinsic factors affect populations of small mammals, including vegetation, soils, predation, competition, and weather. Intrinsic factors, such as genetic and behavioral changes, also are of significance (Krebs 1964:63-67). However, the quantitative relationships between many environmental factors and the distribution and abundance of small mammals usually are considerably less well known than their gen-

/pdf/vegetative-and-edaphic-factors-affecting-abundance-and-4mjgmtd1ke.pdf

Wildlife Management Techniques

Citations

Cattle use on summer foothill rangelands in northeastern Oregon.

Composition, Structure, and Dynamics of Mixed-Species Foraging Aggregations in a Southern New Jersey Salt Marsh

Estimating populations of nesting brant using aerial videography

Vegetative and edaphic factors affecting abundance and distribution of small mammals in southeast Oregon

Attributes of desert tortoise populations at the National Training Center, Central Mojave Desert, California, USA

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