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NUTRIENT UPTAKE AND COMMUNITY METABOLISM IN STREAMS DRAINING HARVESTED AND OLD GROWTH WATERSHEDS: A PRELIMINARY ASSESSMENT
Citation:
Hill, B H. AND F H. McCormick. NUTRIENT UPTAKE AND COMMUNITY METABOLISM IN STREAMS DRAINING HARVESTED AND OLD GROWTH WATERSHEDS: A PRELIMINARY ASSESSMENT. Presented at Symposium on Ecosystem Management Research in the Ouachita and Ozark Mountains, Hot Springs, AZ, October 26-28, 1999.
Impact/Purpose:
The goal of this research is to evaluate stream ecosystem function at three levels of watershed disturbance intensity in four regions of the continental United States. As a secondary objective, we will assess intra- and inter-annual variability in measures of stream ecosystem function. We predict that any amount of watershed disturbance by logging will affect energy flow in the system by depressing community metabolism, increasing nutrient uptake lengths and disrupting ecosystem stability.
Description:
The effect of timber harvesting on streams is assessed using two measures of ecosystem function: nutrient ad community metabolism. This research is being conducted in streams of the southern Appalachian Mountains of North Carolina, the Ouachita Mountains of Arkansas, the Cascade Montains of Oregon, and the redwood forests of northern California, in order to understand similarities and differences among stream ecosystem responses to timber harvesting across diverse geographic regions. Data from Cedar and Peacock Creeks in the redwood forest are used to illustrate the principles and usefulness of measuring stream ecosystem function for assessing watershed disturbances. Streams draining logged watersheds had smaller dominant substrate size and more sand and fine sediments in the channel. Nutrient uptake (NH4+1, PO4-3) and community metabolism (primary productivity, respiration, P:R, net daily metabolism) were measured in streams draining old-growth (Cedar Creek) and harvested (Peacock Creek) watersheds. Phosphate uptake length was significantly shorter in Cedar Creek than in Peacock Creek. Ammonium uptake length was not significantly different in these streams. Preliminary analyses of stream metabolism suggest that primary productivity is greater in streams draining logged watersheds, but community respiration is greater in stream draining old-growth watersheds, resulting in substantial differences in P:R and NDM.