ABSTRACT
Geophysical and climate conditions play an important role in the distribution of organisms at both fine and broad scales. Headwater streams integrate changes at broad geographical scales and serve as important regions of nutrient processing and support high biodiversity. Stream salamanders are important members of headwater aquatic communities as both predators and prey. Combined with their biphasic life histories and physiological requirements, stream amphibians may serve as indicators for headwater stream conditions. We surveyed 50 streams for salamander occupancy, across eight counties of the southern Cumberland Plateau in Tennessee for which we are unaware of any stream amphibian distribution data. Our objective was to determine what variables best-predicted stream amphibian occupancy among species with variable life histories and habitat needs. Models were generated to determine the effects of elevation, catchment forest cover, and total catchment size as indicators of stream condition. We found species showed no significant responses to forest cover. Though forest cover has previously been the primary predictor of stream amphibian occupancy in streams across the United States, stream amphibian occupancy of the southern Cumberland Plateau was most closely associated with elevation and catchment size. Thus, the unique topography of the southern Cumberland Plateau may instead be the more important factor driving occupancy patterns. Despite limited evidence in this study for negative human impacts on salamander occupancy, low occupancy and abundance relative to other ecoregions suggests either poor quality habitat or large historic impacts. Developing a more comprehensive understanding of regional stream salamander occupancy patterns is necessary to ensure effective management and habitat conservation in a region with limited description of stream ecology.
Subject(s)
Animal Distribution , Ecosystem , Rivers , Urodela , Animals , TennesseeABSTRACT
This study examined the effect of modified stroma-free Hgb solution (SFHS) as a resuscitative fluid for rats in an ischemic intestinal shock model. The experiments compared the effect of SFHS with two other resuscitative fluids: lactated Ringer's solution (RL) and 3% albumin in RL. The control group received no fluids. After the induction of shock, the resuscitative solution was given iv over a 6-h period. RL and albumin in RL resulted in long-term (greater than 7 days) survival in 15 of 16 animals. All animals in the control group and six of eight animals in the SFHS-treated group died within 24 h. Hct was used to estimate changes in intravascular volume. All control animals became hemoconcentrated and exhibited a 50% loss in plasma volume. The failure of SFHS to improve significantly the survival in rats compared to the controls is surprising in view of the fact that the SFHS had the same oncotic pressure as the albumin-containing solution and identical volumes were administered.