Terrestrial allochthonous inputs represent the primary energy source for small stream ecosystems, and activities that alter those inputs produce cascading effects through multiple trophic levels. Urban development affects riparian forests through direct removal or through modifications to species composition and structure. Our study evaluated stand composition and litterfall inputs to small streams across a range of urbanization. Heterogeneity was high, but a consistent pattern of deciduous dominance was observed in more-disturbed areas and a mosaic of conifer, mixed, and deciduous forest patches in less-disturbed areas. Such mosaics are a region-dependent pattern that results from Pacific Northwest forest succession. Riparian vegetation disturbance level increased as total impervious area in the watershed increased. Annual mean daily litterfall rates ranged from 0.0 to 2.5 g m−2 d−1 in 128 trap locations distributed over 13 stream reaches that represent the range of riparian vegetation conditions currently present in the Puget Lowland. Conifer, mixed, and deciduous plots in watersheds with disturbance produced 12.5 to 19.3 mg N m−2 d−1 and 0.9 to 1.3 mg P m−2 d−1. Deciduous riparian forests associated with moderate urban development produced organic matter loads similar to those of conifer forests, but the greater prevalence of leaf material produced 54% higher N loads and 40% higher P loads from litter inputs compared to conifer-dominated riparian areas. Conversion from coniferous to deciduous vegetation also produced subtle shifts in timing of inputs. Anthropogenic activities shape and maintain the current vegetation regime in the Puget Lowland, and this regime has profound implications for nutrient processes and aquatic productivity.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.