538 J. N. Am. Benthol. Soc., 2005, 24(3):538–552  2005 by The North American Benthological Society Catchment disturbance and stream metabolism: patterns in ecosystem respiration and gross primary production along a gradient of upland soil and vegetation disturbance JEFFREY N. HOUSER 1 AND PATRICK J. MULHOLLAND 2 Oak Ridge National Laboratory, Bethel Valley Road, PO Box 2008, Oak Ridge, Tennessee 37831-6036 USA KELLY O. MALONEY 3 Department of Biological Sciences, 331 Funchess Hall, Auburn University, Auburn, Alabama 36849-5407 USA Abstract. Catchment characteristics determine the inputs of sediments and nutrients to streams. As a result, natural or anthropogenic disturbance of upland soil and vegetation can affect instream processes. The Fort Benning Military Installation (near Columbus, Georgia) exhibits a wide range of upland disturbance levels because of spatial variability in the intensity of military training. This gradient of disturbance was used to investigate the effect of upland soil and vegetation disturbance on rates of stream metabolism (ecosystem respiration rate [ER] and gross primary production rate [GPP]). Stream metabolism was measured using an open-system, single-station approach. All streams were net heterotrophic during all seasons. ER was highest in winter and spring and lowest in summer and autumn. ER was negatively correlated with catchment disturbance level in winter, spring, and summer, but not in autumn. ER was positively correlated with abundance of coarse woody debris, but not significantly related to % benthic organic matter. GPP was low in all streams and generally not significantly correlated with disturbance level. Our results suggest that the generally intact ri- parian zones of these streams were not sufficient to protect them from the effect of upland distur- bance, and they emphasize the role of the entire catchment in determining stream structure and function. Key words: ecosystem respiration, primary production, catchment disturbance, land use, seasonal patterns, military reservation. Catchment land use affects sediment and nu- trient inputs, physical habitat variables, and bi- ological community composition in streams (Omernik 1976, Richards et al. 1996, Huryn et al. 2002, Strayer et al. 2003). Inputs of sediments and nutrients often increase with the proportion of urban or agricultural land use (Allan et al. 1997, Strayer et al. 2003). Land use also affects physical habitat variables such as abundance of coarse woody debris (Richards et al. 1996). The role of the riparian zone in mitigating some im- pacts of land use has been well studied (e.g., Lowrance et al. 1984, Gregory et al. 1991, Os- borne and Kovacic 1993, Richards et al. 1996), 1 Present address: Upper Midwest Environmental Sciences Center, US Geological Survey, 2630 Fanta Reed Road, La Crosse, Wisconsin 54603 USA. E-mail: jhouser@usgs.gov 2 E-mail addresses: mulhollandpj@ornl.gov 3 malonko@auburn.edu but less is known about how localized, intense disturbance of upland areas affects streams. Despite the growing number of studies of stream metabolism (e.g., Bott et al. 1985, Young and Huryn 1996, Uehlinger and Naegeli 1998, Mulholland et al. 2001, Acun ˜a et al. 2004), rates of ecosystem processes (e.g., ecosystem respi- ration rate [ER] or gross primary production rate [GPP]) in streams have not been used fre- quently to quantify the effects of catchment dis- turbance. Efforts to quantify the effects of land use on the biology of stream ecosystems have emphasized community-scale metrics such as abundance or diversity of fish or macroinverte- brates (e.g., Steedman 1988, Richards and Host 1994). Changes in ecosystem processes are an integrated response to catchment disturbance, and have only recently been advocated as useful measures of stream health (Bunn et al. 1999, Young and Huryn 1999, Gessner and Chauvet 2002). Military reservations present a unique oppor-