Riparian forests situated adjacent to agricultural uplands were studied to test the hypothesis that riparian forests intercept and utilize nutrients lost from these uplands. Production rates, tissue nutrient concentrations, and nutrient accretion rates of woody plants were compared between sites that were contiguous to agricultural areas (test sites) and sites that were separated from agricultural areas by grass buffer zones (reference sites). Net primary production was 10,344 kg ha–1yr–1, but trees within a riparian forest that received runoff directly from a pigpen (test site) had production rates that were 2.5 times higher than the average for all other sites. Above ground forest nutrient accretion rates were also highest at the pigpen test site. Woody plants in test site forests had, on the average, higher branch wood and leaf nutrient concentrations than plants in reference site forests. The data provide evidence that riparian forest communities within agricultural environments absorb and retain nutrients lost from agricultural uplands. As such they are important components of agricultural ecosystems helping to maintain acceptable stream water quality. It is suggested that ecologically sound agricultural practice should include longterm maintenance of natural riparian vegetation zones within agricultural areas.
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