Retentive or leaky: How do stream ecosystems respond to carbon and nitrogen subsidies from non-native Russian olive (Elaeagnus angustifolia)?

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Conference Proceeding

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Russian olive (RO) is an invasive riparian tree widespread throughout the western USA. RO fixes nitrogen and consequently provides subsidies of nitrogen-rich litter and groundwater to streams. RO also contributes a subsidy of carbon via litter fall. We evaluated nutrient limitation of biofilms and measured nitrate and ammonium uptake in upstream-reference and downstream-invaded reaches of 6 streams in Idaho and Wyoming. Magnitude of chlorophyll-a increase on nitrogen addition treatments was lower in invaded compared to reference reaches. Nitrate and ammonium uptake velocities were significantly faster in invaded compared to reference reaches (paired t-test P= 0.05 and 0.03 respectively). In one stream, we constructed carbon budgets for an invaded and a reference reach and compared these to pre-invasion data. At the invaded reach, we observed a 30-fold increase in leaf-litter inputs, but little change in community respiration. We found RO doubled in-stream carbon storage as benthic organic matter and increased particulate terrestrial carbon export from 0.15 to 7.91 g/day. These findings indicate that the nitrogen subsidy from RO is processed in streams biologically while carbon inputs are primarily stored and exported.

Publication Title

American Society of Limnology and Oceanography and the North American Benthological Society Joint Meeting 2010