Influence of coarse wood and fine litter on forest organic matter composition

Forest soil organic matter (SOM) is affected by inputs from coarse wood (CW) and fine litter (FL, e.g., leaves, twigs, cones, and needles). The influence of these materials on forest SOM was studied in a lodgepole pine (Pinus contorta) forest in southeastern Wyoming. Organic materials in CW sites were significantly (P < 0.05) more acidic, but contained half the total N of FL sites. Forest floor materials and SOM C contents were significantly greater in CW samples. Lignin decomposition products (CuO analysis) accumulated primarily in organic horizons of both sites, with significantly higher (60–70%) contents in CW materials. Vanillyl compounds were the primary lignin products from both sites, with cinnamyl compounds also important in SOM from FL sites. Vanillic acid to vanillin ratios were significantly higher in mineral soils under CW. 13C-NMR spectra indicated CW materials were enriched in lignin, and that humic acids from both site types were very similar and unusually high in alkyl C. Fulvic acids were also high in O-alkyl and carboxyl C, particularly in the CW sites. Results suggest there are differences in forest C constituents and that removal of CW could possibly alter forest soil dynamics that would impact forest productivity and biodiversity. Key words: Forest, coarse wood, litter, carbon, soil organic matter, humic substances