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Publication Title: Stream organic matter budgets--introduction
Year: 1997 Publication Type: Journal Article
H. J. Andrews Publication Number: 2368
Citation: Webster, J. R.; Meyer, J. L. 1997. Stream organic matter budgets--introduction. In: Webster, J. R.; Meyer, J. L., eds. Stream organic matter budgets. Journal of the North American Benthological Society. 16: 5-13.
Online PDF: http://andrewsforest.oregonstate.edu/pubs/pdf/pub2368.pdf
Abstract: This analysis of organic matter dynamics in streams has 3 objectives: 1) to explore therelationships between physical characteristics of streams and their watersheds (climate, geomorphol-ogy) and stream organic matter dynamics using data from a broad geographic area; 2) to comparestream organic matter dynamics in a diverse array of streams in order to suggest determinants ofobserved patterns; and 3) to reveal deficiencies in currently available data on organic matter dynamicsin streams. Streams were included in this analysis not to represent the global diversity of streamtypes but because organic matter data were available. In the introductory chapter we describe thekinds of data included for each stream and provide brief descriptions of previously published organicmatter data for streams included in the comparative analysis but not described in individual chapters.The next 16 chapters present organic matter data for streams from North America, Europe, Australia,and Antarctica. Most of the streams represented are in the temperate zone of North America. Datapresented include climate and geomorphic variables and organic matter inputs, exports, and standingcrops. The chapters on individual streams are followed by 7 chapters analyzing physical features ofthese streams and specific components of the organic matter budgets. Stream size, water temperature,and precipitation were the most important variables setting the physical template for organic matterprocesses occurring in the streams. Watershed area was the best predictor of gross primary produc-tivity (GPP), which increased with increasing watershed area. Watershed area, discharge, and solublereactive phosphorus concentration explained 71% of the variation in GPP. Climate (latitude) andvegetation type were more important than stream order in predicting litter inputs across a broadgeographic range of streams, although, within a river basin, litterfall decreased with increasingstream order. Regression of benthic organic matter (BOM) and latitude and precipitation proveduseful in predicting BOM standing crop in streams at a continental scale, although BOM was alsorelated to channel characteristics such as gradient and woody debris. Benthic respiration increaseddramatically with increasing temperature (Q,o = 7.6), suggesting a response related not only tometabolism but also to changes in BOM quality in response to latitudinal shifts in vegetation. Ter-restrial and riparian vegetation was found to play an important role in regulating suspended partic-ulate organic matter (POM) concentration and export, with higher values observed in forested streamsand in lower gradient streams with extensive floodplains. Channel slope was the best predictor ofdissolved organic matter (DOM) concentration and export, probably because of its relationship withriparian wetlands and hydrologic flowpaths. In the final chapter, a synthesis of the organic matterbudgets, we reached two conclusions: 1) At a global level, stream organic matter dynamics are drivenprimarily by climate through its effect on terrestrial vegetation. 2) Despite significant progress inunderstanding organic matter processes in streams, many of the differences we found among streamsreflect omissions of important components of the budget, especially accurate measures of streambedarea, heterotrophic respiration, standing stock of fine BOM, and groundwater inputs of DOM. Key words: stream, organic matter. budget, primary production, litterfall, BOM, DOM, POM, res-piration.
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