Treesearch

The modern North American grassland herpetofauna has evolved in situ since the Miocene. Pleistocene glaciation had a minimal effect except in the far North, with only minor displacements of some species. South of the glaciers, winters were warmer and summers cooler than at present. Snakelike reptiles, leaping frogs, and turtle "tanks" are favored adaptive types in uniform dense grassland. A typical fauna consists of about 10-15 species, mostly snakes. Special habitat components, such as streams and ponds, bare ground, sand, trees, prairie dog towns, and rocky outcrops, add distinct suites...

Of the bat research that has been conducted in the Southwestern states, few studies have addressed species inhabiting grasslands and the potential effects of management activities on these populations. Up to 17 bat species may be found regularly or occasionally in Southwestern grasslands or short-grass prairie. Main habitat requirements of grassland-dwelling bats are suitable roosts, water, and food. Livestock grazing, fire suppression, mining, bridge construction, agriculture, and urbanization affect the quality, quantity, and distribution of these resources. Effects of activities may not...

We analyzed trends of sparrows and towhees captured in fall at the Rio Grande Nature Center, Albuquerque, New Mexico from 1985 to 1994. Species were grouped into three breeding-habitat classes: grassland and shrubsteppe, riparian and deciduous vegetation, and upland forests, woodlands, and edges. Spearman's rank correlations were used to determine whether population trends were similar within and among species groups. We found that steep fluctuations in captures of many species masked population increases or decreases over time. Eight of nineteen (42%) correlations of pairs of species were...

Management of a 775-km2, privately-owned ranch in northeastern Utah exemplifies a progressive approach to utilizing domestic livestock and wild ungulates, elk (Cervus elaphus), mule deer (Odocoileus hemionus), and pronghorn (Antilocapra americana), for economic return while maintaining or enhancing land health. The management program on the Deseret Ranch includes the use of a multiple-herbivore grazing system in balance with the available forage and native wildlife in a sagebrush (Artemisia spp.)-grass ecosystem.

This publication is the result of a half-day symposium, "Ecology, management, and sustainability of western grassland ecosystems," held at The Wildlife Society’s First Annual Technical Conference, September 22-26, 1994 in Albuquerque, NM. The symposium was sponsored by The Wildlife Society's Working Group on Sustainable Use of Ecosystem Resources and was organized by members Deborah Finch, Gale Wolters, and Bertie Weddell. The scope of this working group is the assembly, study, and transfer of information pertaining to the conservation of wildlife through sustainable uses of ecosystem...

Retrospective examination of cutover forests enables the development of models that predict regeneration success as a function of plot conditions and time since disturbance. The modeling process uses a two-state system. In the first state, all plots are analyzed to predict the probability of stocking (at least one established seedling on the plot). In the second state, only stocked plots are analyzed to predict seedling density, species composition, and seedling heights. Outcomes are predicted on a plot basis; therefore, the model is sensitive to variation within the stand. Predictions are...

Numerous subcontinental-scale projects have placed significant emphasis on the use of Normalized Difference Vegetation Indices (NDVI's) derived from Advanced Very High Resolution Radiometer (AVHRR) satellite data for vegetation type recognition. In multi-season AVHRR data, overlap of NDVI ranges for vegetation classes may degrade overall classification performance. The preliminary work of this project is presented to illustrate potential differences in vegetative cover discrimination capabilities between original visible and near-infrared (NIR) channels of AVHRR data and NDVI's derived...

A Monte Carlo simulation was used to evaluate the statistical properties of measures of association and the Kappa statistic under double sampling with replacement. Three error matrices representing three levels of classification accuracy of Landsat TM Data consisting of four forest cover types in North Carolina. The overall accuracy of the five indices ranged from 0.35% to 82.1% depending on the number of classes, the level of classification accuracy of satellite imagery, and the simulated sample sizes of reference plots. Statistical criteria used in the evaluation included: percent bias,...

An accuracy assessment method involving double sampling and the multivariate composite estimator has been used to validate the prototype seasonal land cover characteristics database of the conterminous United States. The database consists of 159 land cover classes, classified using time series of 1990 1-km satellite data and augmented with ancillary data including terrain, climate, and ecological definitions. Reference data from more than 2,200 1 km2 plots were independently collected; data included descriptions of dominant land cover types. Validity of the database is presented in terms...

Adaptive management of ecosystems (e.g., Holling 1978, Walters 1986, Everett et al. 1994, Grumbine 1994, Yaffee 1994, Gunderson et al. 1995, Frentz et al. 1995, Montgomery et al. 1995) structures a system in which monitoring iteratively improves the knowledge base and helps refine management plans. This adaptive approach acknowledges that action is necessary or appropriate with imperfect knowledge (Raiffa 1968, Walters 1986, Everett et al. 1994, USDA/FS and DOI/BLM 1994b) and that initial actions can be refined as more information becomes available. Imperfect knowledge is the case in...