Factors Controlling Sediment Community Respiration in Woodland Stream Ecosystems

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Abstract
In shaded woodland streams, sediment community respiration is an important measure of decomposition of organic matter. In situ rates of community respiration were measured in sediments from shaded woodland streams at the Hubbard Brook Experimental Forest (HBEF), USA, by estimating rates of CO2 production in low-disturbance benthic chambers. Rates of sediment community respiration (range: 26-340 mg C .cntdot. m-2 d) were closely correlated with amounts of sediment organic matter, but not with water column DOC or sediment size structure. Analysis of literature data indicated similar couplings between community respiration and sediment organic matter in other streams and in lakes and marine systems. However, respiration per unit organic matter was 23-fold higher in lakes and marine systems than in woodland streams, apparently due to differences in quality of organic matter (algae and macrophytes vs terrestrial detritus). In HBEF streams, community respiration was elevated in sediments of organic debris dams, suggesting that organic debris dams are focal sites of metabolism and nutrient regeneration in the stream channel.