The Ecogeography of The Herpetofauna, Fishes, Birds, and Macro-invertebrates of the South Fork Trinity River Basin.
Determining Patterns of Biodiversity and Quantifying Watershed-Scale Variability Relative to Hydrologic and Other Landscape Processes in a Tier-One-Key Watershed with an AMA Component
Using GIS, we are classifying the vegetation and determining relative amounts of each type in 60 catchments across the 1,500 square mile watershed. From these data we can characterize the disturbance regimes that most influence vegetation dymanics, and then arrange our catchments into meaningful groups for comprisons with patterns among the riparian and aquatic biota.
Using 22 environmental variables in a cluster analysis yielded four distinct sets of catchments among the total sample of 60. A subsequent discriminate analsysis supported these groupings and revealed which variables best distinguished each set.
We used principal components ordination to project those groupings in three dimensional space based on the most influential environmental gradients. These gradients consisted of three hardwood size classes, two conifer size classes, stand age, daily amplitude of stream temperature, slope, elevation, variability in canopy closure, and the number of road crossings above the sample reach.
We are currently examining the distributions of the amphibians, reptiles, fishes, birds and macroinvertebrates in the South Fork Trinity watershed as they relate to our four sets of streams, in order to determine patterns of biodiversity and quantify watershed scale variability relative to both hydrologic and landscape disturbance regimes.
We intend to quantify the distribution patterns of individual species relative to various environmental gradients. For example, tailed frog requires high gradient, cold water streams to persist. It is usually confined to the upper reaches of mountain streams and is a poor disperser. Tailed frog is a bioindicator of headwater stream health and is a species of special concern in California
Preliminary results indicate that many animal distribution patterns are related to the environmental gradients we have quantified. For example, the stream reaches in group two have the highest numbers of tailed frog, but no steelhead.
Ongoing research includes riparian and upland bird censuses and fish and herpetofaunal resamples. Proposed completion date is October 2005. Up to five publications will result from this research. These will be published in various journals and on the Redwood Sciences website.
Last updated on November 22, 2002, by Garth Hodgson