EFFECTS OF LAND USE ON STREAM METABOLISM AND ORGANIC MATTER TURNOVER

Abstract

We measured ecosystem metabolism and organic matter transport seasonally in five streams draining catchments dominated by native forest, exotic pine plantation, grazed tussock grassland, or developed pasture. All streams are tributaries of the Taieri River in southeastern New Zealand. Whole-stream metabolism was estimated by both two-station and single-station open-channel methods, allowing comparison between these techniques. Transfer of oxygen across the stream surface was estimated using reaeration coefficients determined from three different procedures: tracer gas injections (propane), analysis of the oxygen record, and empirical velocity–depth equations. Measurements of gross primary production (GPP) and community respiration (CR) showed differences among streams that reflected method rather than ecosystem process. The ratio of GPP:CR and net ecosystem metabolism, however, showed strong concordance among methods, suggesting that bias involved in standardizing estimates to areal units may be more impo...