| Abstract: | Small streams in forested landscapes are tightly coupled to the vegetation of the surrounding forest, and one of the key drivers of the stream ecosystem is the nature of organic matter supplied to it. This paper is focussed on three questions related to organic matter dynamics in small, forested streams of the conifer dominated Pacific Northwest: (1) How do small streams differ from large streams? (2) How do small streams of the Pacific Northwest differ from those of other regions? and (3) How do forest practices alter organic matter dynamics of small streams in the Pacific Northwest? The organic matter dynamics of small streams in this region differ from temperate deciduous forests in the nature of the organic matter deposited (protective chemicals, hard epidermis, slower loss rates), the timing of inputs (distributed throughout the year), and the transport rates (smaller, hard needles are more easily transported). The large amount and persistence of wood in these streams provides an additional source of organic matter that can be consumed by particular species and contributes to biofilm and fine particulate organic matter (FPOM) production. Logging is commonly practiced in many forests of the region. This practice has been shown to alter the type, amount, and timing of organic matter delivery to small streams and reduce the amount and size of large wood. Changes in channel complexity and water temperature after logging also can contribute to reduced organic matter storage. Many of the processes controlling organic matter dynamics in small streams are well described in other regions. However, the climate, vegetation, and topography of the Pacific Northwest suggest that the rates and nature of some processes affecting stream organic matter may differ considerably from other regions. Further research on small streams of this area will be required to better understand these differences. |
