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MOJAVE DESERT SPRING: THE AMPHIBIAN POINT OF VIEW
Citation:
Bradford, D F., A C. Neale, M S. Nash, D. W. Sada, AND J R. Jaeger. MOJAVE DESERT SPRING: THE AMPHIBIAN POINT OF VIEW. Presented at Spring-fed Wetlands: Important Scientific and Cultural Resources of the Intermountain Region, Las Vegas, NV, May 5-7, 2002.
Impact/Purpose:
The primary objectives of this research are to:
Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;
Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;
Develop and validate multivariate models based on quantification studies;
Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;
Complete an initial draft (potentially web based) of a national landscape condition assessment.
This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.
Description:
Numerous springs are scattered throughout the eastern Mojave Desert, most of which are concentrated near the bases of mountain ranges. Spring-fed wetlands in this region comprise nearly all the available habitat for amphibians. We surveyed 128 springs for amphibians and habitat throughout a 20,000 km' area below 173 5 in elevation. Wetlands were typically small, extending a median distance of only 200 m with a median water area of only 72 ml during the spring time. Most springs are ephemeral, and only 14% contained endemic animal taxa characteristic of geologically persistent water. A study of the red-spotted toad (Bufo punctatus) revealed that it occurs at 73% of the spring sites, populations can withstand considerable site disturbance, and site occupancy is determined primarily by local environmental factors rather than metapopulation processes (e.g., isolation by distance). In contrast, the Vegas Valley leopard frog (Ranafisheri) was eliminated by water development and possibly by introduced American bullfrogs (R. catesbeiana) in the Las Vegas Valley in the 1940s. The southwestern toad (B. microscaphus) has also been eliminated from the Valley, whereas Woodhouse's toad (B. woodhousii) has invaded this area. The relict leopard frog (R. onca), which formerly ranged from southwestern Utah to below Hoover Darn, now persists at only five wetlands fed by geothermal springs, and numbers approximately I I 00 individuals. The Pacific treefrog (Pseudacris regilla) persists at nearly all historical localities, and is particularly abundant on the east side of the Spring Mountains. Most springs have been substantially disturbed by anthropogenic activities, the most ubiquitous of which has been water development for livestock grazing. Restoration of many springs is needed to protect them for amphibians and the many other wildlife taxa that cannot exist in the region without them.