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EFFECTS OF LAND USE ON STREAM METABOLISM AND ORGANIC MATTER TURNOVER
Author(s) -
Young Roger G.,
Huryn Alexander D.
Publication year - 1999
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/1051-0761(1999)009[1359:eoluos]2.0.co;2
Subject(s) - ecology , organic matter , environmental science , land use , environmental chemistry , biology , chemistry
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 important than differences among methods. The two‐station approach appeared to cope more adequately with steep slope, high bed roughness, and low GPP than did the single‐station method. However, in tranquil and productive streams, both methods worked well. When differences between methods were accounted for, results emphasized how differences in terrestrial landscapes may markedly affect ecosystem processes within streams. Shading by the heavy canopy at the native forest site, turbidity at the pasture site, and the valley walls at one of the tussock grassland sites appeared to limit GPP. CR was high in the native forest site, due to a large supply of organic material from the riparian zone. Concentrations of seston were highest at the developed pasture site, apparently a result of intensive grazing and associated bank failure. The organic content of seston was highest in the native forest site and lowest in the pasture site. Organic carbon spiraling length in the pasture site was longer than average for a stream of its size, whereas spiraling length in the native forest site was short when compared to similar‐sized streams elsewhere. Changes in catchment land use and riparian vegetation, as well as reach‐specific geomorphic factors, alter light availability and organic matter supply, which are fundamental factors controlling organic matter production, respiration, and transport in streams.