Ernest B. Fish

AQUATIC MACROINVERTEBRATE DIVERSITY OF PLAYA WETLANDS: THE ROLE OF LANDSCAPE AND ISLAND BIOGEOGRAPHIC CHARACTERISTICS

Wetland habitats continue to be lost at a unsettling rate, especially freshwater emergent wetlands that are isolated geographically. These are the predominant wetlands found in arid and semi-arid environments, where they serve as foci of regional biodiversity. This is especially true of the playa wetlands of the Southern High Plains of Texas, USA. The factors that determine and maintain biotic diversity in these wetlands are understood poorly. Consequently, this study examined the effect of island biogeographic and landscape features on the diversity of aquatic macroinvertebrates in playa wetlands. Macroinvertebrates were collected from playas three times during the spring and summer of 1994 and categorized as resident or transient taxa based on life history strategies. Diversity was estimated using taxonomic richness (richness) and Fisher’s log-series alpha (α). Surrounding land-use practices influenced resident richness, whereas playa surface area affected resident and transient richness, as well as resident α. However, relationships differed among sampling dates. Regression analyses suggested that transient richness and α were influenced more by insular characteristics than by landscape features. The converse was true for resident richness and α. Therefore, both insular and landscape characteristics affected the diversity of macroinvertebrates in playa wetlands, but impacts were dependent on life-history strategy and time since inundation (i.e., sampling date). Consequently, conservation and management efforts targeting macroinvertebrates in playa wetlands will need to focus on the wetlands and characteristics of adjacent watershed features.

Phenological Effects on Forage Quality of Five Grass Species

Abstract Information on nutritive values of each plant part in each phenological stage could help range managers choose suitable grazing times to achieve higher animal performance without detriment to vegetation. Thus, nutritive value of different plant parts of 5 grass species in 3 phenological stages (vegetative, flowering, and seed production) from 2 sites were investigated. Species included: Agropyron tauri Boiss and Bal., Agropyron trichophorum Richt, Bromus tomentellus Boiss, Festuca ovina Hack, and Hordeum bulbosum L. Samples of leaf, stem, and flower from 5 locations at each site for each species were analyzed for dry matter ratio of plant parts, crude protein, acid detergent fiber, neutral detergent fiber, dry matter digestibility, and metabolizable energy. A completely randomized design with a factorial arrangement of species and phenological stage was analyzed with 5 replicates for each location. Plant part was included as a subplot factor in a split plot arrangement. Nutritive values differed significantly (P < 0.05) both within and among plant parts and phenological stages for each species. Phenological stages indicated a significant difference on nutritive value of plant parts, with leaves having the highest nutritive value. Thus, forage with a higher leaf-to-stem ratio should improve animal performance because at the beginning of the 2nd phenological stage, the plant had desirable quantity and quality of forage with higher leaf-to-stem ratio.

HABITAT USE, HOME RANGES, AND SURVIVAL OF SWIFT FOXES IN A FRAGMENTED LANDSCAPE: CONSERVATION IMPLICATIONS

Abstract Habitat loss might be one of the primary reasons for the decline of the swift fox (Vulpes velox) in the western Great Plains of North America. From 1998 to 2001, we monitored 42 swift foxes in a landscape interspersed with native short-grass prairies, nonnative grasslands enrolled in the Conservation Reserve Program, irrigated agricultural fields, and dry-land agricultural fields. Survival estimates ranged from 0.52 to 0.66 for both adults and juveniles, and the primary causes of death were vehicle collisions (42% deaths) and coyote (Canis latrans) predation (33%). Annual home-range size was similar for males and females (10.8 and 10.5 km2, respectively). Within the study area, swift foxes selected only short-grass prairies and had lower-than-expected use or complete avoidance of all other habitat types. Our results indicate swift foxes are more specialized in habitat selection than other North American canids; thus, protection of native short-grass prairies might be necessary for their long-term existence.

Macronutrient and Trace Element Leaching Following Biosolids Application on Semi-arid Rangeland Soils

The objective of this study was to quantify the leachate concentration of macronutrients and trace elements obtained through intact soil columns containing two rangeland soils with different texture and amended with biosolids. This was done to evaluate the possibility that surface application of biosolids could adversely affect subsurface water quality via leaching. Biosolids were applied on the surface of the soil columns at 0 (control), 7, 18, 34, or 90 Mg ha−1 in dry basis. Results indicated that biosolids did not increase NO3 − − N leaching, except for the application of 90 Mg ha−1 in the Stellar soil (Calciargid), the finer-textured soil. In the Armesa soil (Haplocalcid), the coarser-textured soil, all leachate NO3 − − N concentrations were higher than the maximum contaminant limit (MCL) for drinking water established by USEPA, irrespective of biosolids treatment. Orthophosphate leaching occurred mostly in the Stellar soil and was favored by biosolids application. Of the trace elements that are regulated by USEPA, Cd, Ba, Cr, and Be were found below the MCL for drinking water irrespective of the biosolids application rate or soil type. The application of 90 Mg ha−1 of biosolids represented a significantly higher potential of leaching for many elements and compounds (NO3 − − N, SO4 =, Cl−, Ca, K, Mg, Na, and Sr) than applications of 34 Mg ha−1 or lower. In general, the application of biosolids up to 34 Mg ha−1 did not pose potential adverse effects for subsurface water quality.

HABITAT RELATIONSHIPS BETWEEN SYMPATRIC MULE DEER AND WHITE-TAILED DEER IN TEXAS

Abstract Desert mule deer (Odocoileus hemionus eremicus) and Texas white-tailed deer (O. virginianus texanus) are sympatric in west-central Texas. During winter, spring, and summer 1999 and 2000, we recorded locations of sympatric mule and white-tailed deer to determine habitat-use differences between species. We measured 379 mule deer and white-tailed deer locations for biotic and abiotic landscape parameters. Slope and percent shrub cover explained most variation in distributions of the 2 species. Locations of bedded deer were the most discriminated behavior type for all models. Density of shrubs and slope were the most important variables used to describe habitat preference by either deer species. Mean shrub cover used by mule and white-tailed deer at bed sites was 37.7% and 53.9%, respectively. Mean percent slopes used by mule and white-tailed deer for bed sites were 9.2 and 2.9, respectively. To a lesser extent, the same habitat parameters discriminated locations between deer species for moving and browsing for 1999 and 2000. If land managers want to maintain both deer species, several land management actions might be necessary. For mule deer on relatively steep slopes, managers should maintain lower percent woody cover and encourage native forb growth. For white-tailed deer in lower drainages, managers should maintain >50% woody species cover and encourage intermittent grass growth in the remaining areas.

Erosional impacts of trails in Guadalupe Mountains National Park, Texas

Abstract Twenty-six erosion transects were established on a variety of surface situations to include major trails and roads, small trails and non-trail controls. Transects were remeasured at intervals of 4, 5, 8 and 17 months. Results indicate that active soil movement is occurring throughout Guadalupe Mountains National Park. Approximately 85% of the points measured showed evidence of change, either by erosion or deposition. Major trails and roads indicate a greater degree of instability based on cross-sectional area changes. A greater percentage of the cross-sectional area change is attributable to deposition in the major trail or road and small trail categories when compared to the control transect category. These results may indicate that the trail sites are serving as deposition zones as a result of their impedence of normal drainage routes.

Evaluation of trail erosion in Guadalupe Mountains National Park, Texas

Abstract Guadalupe Mountains National Park, located in southwest Texas, is primarily a park for hiking and backpacking. Trails provide the only access to most scenic features and attractions. Permanently established erosion transects were studied to determine whether on-trail erosion was significantly greater than that occurring off-trail and to establish the factors which significantly contribute to the erosional/depositional process. Results after 3.5 years of study indicate that the net erosion and deposition of soil on the trails closely approximate those occurring naturally off the trail. Trail sites are relatively more unstable and experience greater soil movement (measured as absolute area change) than do off-trail sites. Differences in environmental site factors did not significantly affect the on-trail erosion process. Factors resulting from human impact (trail width and visitor use) were directly related to increased amounts of soil movement (absolute area change), but did not necessarily result in greater net erosion.

Predicting Private Landowner Support toward Recolonizing Black Bears in the Trans-Pecos Region of Texas

Black bears (Ursus americanus) began recolonizing the Trans-Pecos region of Texas from Mexico in the late 1980s after a 30-year absence. This region is predominately a ranching community and knowledge of landowner attitudes is essential to development of management plans for this population. We surveyed 1,100 landowners in the region to measure their response toward the natural recolonization of black bear in the Trans-Pecos. More positive scores toward black bear recolonization came from younger, more educated landowners who had owned land for less than three generations. Of the landowners against recolonization most (52%) believed that livestock losses would be excessive. Managers would benefit by focusing their efforts on increasing awareness of methods for preventing black bear damage to landowners with negative attitudes and those owning large parcels (>4,048 ha) of land possibly containing potential bear habitat. It is important that managers consider and incorporate landowners when managing this increasing black bear population.

Biosolids Effects in Chihuahuan Desert Rangelands: A Ten-Year Study

Arid and semiarid rangelands are suitable for responsible biosolids application. Topical application is critical to avoid soil and vegetation disturbance. Surface-applied biosolids have long-lasting effects in these ecosystems. We conducted a 10-year research program investigating effects of biosolids applied at rates from 0 to 90 dry Mg ha−1 on soil water infiltration; runoff and leachate water quality; soil erosion; forage production and quality; seedling establishment; plant physiological responses; nitrogen dynamics; biosolids decomposition; and grazing animal behavior and management. Biosolids increased soil water infiltration and reduced erosion. Effects on soil water quality were observed only at the highest application rates. Biosolids increased soil nitrate-nitrogen. Biosolids increased forage production and improved forage quality. Biosolids increased leaf area of grasses; photosynthetic rates were not necessarily increased by biosolids. Biosolids effects on plant establishment are expected only under moderately favorable conditions. Over an 82-mo exposure period, total organic carbon, nitrogen, and total and available phosphorus decreased and inorganic matter increased. Grazing animals spent more time grazing, ruminating, and resting in biosolids-treated areas; positive effects on average daily gain were observed during periods of higher rainfall. Our results suggest that annual biosolids application rates of up to 18 Mg ha−1 are appropriate for desert rangelands.

Distribution of the Swift Fox (Vulpes velox) in Texas

Abstract Swift foxes (Vulpes velox) once occupied ca. 79 counties in Texas, but surveys in 1997–1998 indicated the range of the species was reduced to two counties. We used scat-transects and live-trapping during 2005–2007 to assess current distribution of the species in Texas. Our results indicated that distribution of the swift fox in Texas remains significantly reduced from the historical distribution and that population densities are low where the species currently exists.