Summer temperatures in small stream sources on managed Olympic Peninsula timberlands

Black, Jenelle

Study of the effects of timber harvest on small stream temperatures. From the Introduction: "Small streams and their sources in forestlands provide habitat for many animals and supply water to larger streams used by salmon and trout. Invertebrates, amphibians, and fishes living in very samll streams are adapted to the speciific ecology of their habitats and are often unable to adapt to large environmental changes (Bury,1988). For example, stream water temperature changes alter dissolved oxygen levels, biotic composition, and algal and bacterial growth (Noel et al, 1986). Warm temperatures have been suggested as a factor in population declines of salmonids, many of which have been listed as endangered (Ticomb, 1926; Brett, 1956). High average and peak water temperatures (above 20 C for salmonids) can cause disease and mortality in most aquatic biota, although moderately warm temperatures (13 to 18 C) can benefit some fish (Brett, 1956; Sullivan et al, 2000). Some other species, particularly amphibians have a very low tolerance for any change in temperature regime. For instance, increasing the daily temperature fluctuation by even a few degrees C can affect some species (Bury and Corn, 1988; Corn and Bury 1989). Therefore, potential changes in stream temperatures following timber harvest, espeically summer temperatures, concern many ecologists. ... The overall goal of this study is to increase the understanding of water temperatures at the sources of small streams. Specific objectives were to: 1. compare water temperatures between point emergence zones (springs) and more dispersed emergence zones (marshes); 2. investigate how source temperatures were affected by timber harvest and shade at and near the source, and 3. compare measured small stream and source temperatures with current and proposed regulatory limits. In order to achieve these objectives, small-stream temperatures were investigated on timberlands with mature timber, immature timber, and no timber (just-harvested) during the summer low-flow, peak temperature season (August 10 through September 10, 19997) on the western side of the Olympic Peninsula in Washington State."