Benthic Organic Matter Storage in Streams: Influence of Detrital Import and Export, Retention Mechanisms, and Climate

In lotic ecosystems, BOM is a major energy source for secondary production (Minshall 1967, Benke et al. 1984), influences nutrient cycles (Mulholland et al. 1985), and affects export of DOM and POM (Bilby and Likens 1980, Bilby 1981, Smock et al. 1989). Benthic detritus also influences channel stability and retention characteristics (Keller and Swanson 1979, Mosley 1981, Webster et al. 1994) and provides habitat for stream microorganisms, macroinvertebrates (Benke et al. 1984, Huryn and Wallace 1987), and fish (Angermeirer and Karr 1984, Elliott 1986). However, in spite of the great importance of BOM to stream ecosystem function, benthic detrital storage is one of the most poorly understood components of stream organic matter budgets (Cummins et al. 1983). Storage of BOM is governed by a broad spectrum of processes. At the scale of the river continuum, BOM tends to decrease downstream as channels become larger and riparian influences decline (Naiman and Sedell 1979, Minshall et al. 1983, Conners and Naiman 1984, Naiman et al. 1987). Individual reaches, however, are influenced not only by their position along a river continuum but also by local variations such as the character of riparian vegetation (Minshall et al. 1983, Gurtz et al. 1988) and floodplain size. Within reaches, BOM distribution is further affected by retention mechanisms, including debris dams and pools (Huryn and Wallace 1987, Smock et al. 1989, Trotter 1990, Jones and Smock 1991), channel characteristics like gradient, and interactions between main-channels and flood-