DOC Release from Alder Leaves and Catkins during Decomposition in a Small Lowland Stream

Alder leaves and catkins were placed in a small stream, then retrieved in weekly intervals, and rates of release of dissolved organic carbon (DOC) and substantial DOC characteristics were determined. Decomposition rates of leaves and catkins were 0.026 d–1 and 0.011 d–1 on the streambed, and 0.017 d–1 and 0.009 d–1 in the sediments, respectively, during 5 weeks of decomposition. The rate of DOC release from leaves declined from 18.0% d–1 to 0.7% d–1, and had a higher proportion of low molecular weight compounds, more saturated and contained larger humic molecules than DOC from catkins, which rate of release declined from 10.6% d–1 to 0.1% d–1. In initial stages of the decomposition, leaf material produced more biodegradable DOC (BDOC) than catkins. During the period of low leaf litter input, DOC released from catkins can become an important instream source of labile DOC. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)