Evaluating the Association Among Alternative Measures of Cumulative Watershed Effects on a Forested Watershed in Eastern Oregon

Abstract

Abstract The national forests must address cumulative effects in planning, including cumulative effects on streams and watersheds. This analysis compares predictions of a commonly used index of landscape use [equivalent clearcut acres (ECA)] with predictions of two indices of aquatic habitat quality (stream sediment and stream temperature) and estimated timber harvest levels to test the degree of association over a 100 yr planning horizon. We found significant negative association between predicted ECA and stream temperature index levels. No significant association was observed among all other combinations of predicted variables. All four indices (stream sediment, stream temperature, ECA, timber harvest levels) were evaluated using a different set of spatial and nonspatial data, thus variation in one index did not necessarily imply that a corresponding positive (or negative) variation in another would occur. We concluded that different relationships among these indices may be observed, depending on how a planning problem is formulated. Therefore, predicted ECA levels may not be a good proxy for predicted stream sediment and temperature levels (or vice versa). Finally, we cannot say that the stream sediment index (or temperature index) used here is a good proxy for actual sediment delivery or transport levels (or temperature levels), because the relationship between predicted values and actual field measurements was not investigated. West. J. Appl. For. 13(1):15-22.