Nitrogen dynamics in stream wood samples incubated with C-14-lignocellulose and potassium N-15-nitrate

• Published in: Applied and environmental microbiology 1985-01, Vol.49 (5), p.1119-1123
• Main Authors: Aumen, NG, Bottomley, P J, Gregory, S V
• Format: Article
• Language: English
• ISSN: 0099-2240

Surface wood samples, obtained from a Douglas fir log in a Pacific Northwest stream, were incubated (up to 18 days) with carbon-14-lignocellulose in a defined mineral salts medium supplemented with 10 mg nitrogen per litre as potassium nitrogen-15-nitrate. The organic nitrogen content of the lignocellulose-wood mixture increased from 132 ug to a maximum of 231 ug per treatment at day 6. Rates of lignocellulose decomposition were greatest during the first 6 days and began to decline over the remaining 12 days. Total carbon dioxide evolution followed a similar pattern. Filtrate ammonia-N increased from background levels to a final value fo 57 ug per treatment. Filtrate nitrate-N completely disappeared by day 6, and organic nitrogen decreased slightly between days 12 and 18. The majority (41 ug) of the labelled nitrogen that could be recovered appeared in the particulate organic fraction by day 6. The filtrate ammonia-N fraction contained 11 ug of labelled nitrogen by day 18. Gain or loss of nitrogen from the experimental system, resulting from nitrogen fixation and denitrification, was insignificant. These results indicated that woody debris in stream ecosystems might function as a sink for exogenous nitrogen, resulting in stimulation of wood decomposition and subsequent activation of other nitrogen cycling processes.