Incorporation of nitrogen from decomposing red alder leaves into plants and soil of a recent clearcut in Oregon

• Published in: Canadian journal of forest research Vol. 27; no. 9; pp. 1496 - 1502
• Main Authors: Swanston, C.W, Myrold, D.D
• Format: Journal Article
• Language: English
• Published: 01.09.1997
• Subjects: Alnus rubra; biogeochemical cycles; degradation; forest soils; fractionation; isotope labeling; nitrogen; plant litter; soil depth; soil microorganisms; soil water; vegetation; Oregon
• ISSN: 0045-5067; 1208-6037
• DOI: 10.1139/x97-116

Nitrogen incorporation from red alder (Alnus rubra Bong.) into an Oregon upland mesic forest soil was studied by tracing the fate of 15N added as 15N-labeled alder leaf litter. The recovery of 15N in vegetation, litter, light- and heavy-fractions of the soil, the chloroform-labile (microbial biomass) pool, and the whole soil were investigated after a 21-month field incubation of the labeled liner. 15N abundances well in excess of normal values were measured in vegetation growing in the plots, perhaps 3% of the 15N excess initially added. Additionally, the recovery of initial 15N after 21 months was 31% in remaining litter, 34% in the upper 5 cm of soil, and 4% in the 5-15 cm depth class. Alder litter had lost 78% of its mass, 77% of the total initial N (14N + 15N), and 64% of the initial 15N. 15N recovery was higher in the light fraction than in the heavy fraction. The soil heavy fraction accounted for 77 to 88% of the total soil N; however, the concentration of N in the light fraction was 3.5 times that in the heavy fraction. Recovery of excess 15N in the chloroform-labile N fraction was not significantly different from zero. After 21 months of decomposition, alder detritus was a net source of N; most of which remained in the top 5 cm of soil where it was concentrated in the more labile pools of soil N, and some of which was incorporated into growing plant tissue.