DISSOLVED ORGANIC CARBON ENRICHMENT ALTERS NITROGEN DYNAMICS IN A FOREST STREAM

摘要: Dissolved organic carbon, DOC, is an important source of carbon for stream heterotrophs. In many systems, bacteria and fungi are limited. Thus, avail- ability may control both the availability dynamics other nutrients (N or P) in heterotrophic systems. To test interdependence C N cycles forested streams, we continuously added as potassium acetate, to draining Watershed six at Hubbard Brook Experimental Forest, New Hampshire, weeks during summer 1999. For two months prior throughout addition, monitored streamwater N03- NH4+ concentrations 70-m upstream reference downstream treatment reaches. We also estimated uptake lengths rates using back-to-back, short-term enrichments The change concentration addition was used estimate whole-stream nitrification. Once before DOC once measured denitrification respiration reach, increase labile caused nitrate decrease from pretreatment addition. Metabolism higher treat- ment than reach that while metabolism had been similar reaches Prior were longer reach. During forms nitrogen much shorter Contrary expectations, enrichment did not lead increased denitrification. principal effect stimulate bacterial growth, leading high a corresponding assimilative demand nitrogen. Results this experiment demonstrate tight link- ages between headwater streams.