EFFECTS OF SEASON AND 4 TREE SPECIES ON SOLUBLE CARBON CONTENT IN FRESH AND DECOMPOSING LITTER OF TEMPERATE FORESTS

Decomposition of plant material is an important component in the study of forest ecosystems because of its critical role in nutrient cycling . The turnover of nutrients in forest soil organic matter depends on, among other factors, a readily available supply of C for decomposer or ganisms. Levels of water soluble C in leachate from four species of fo rest floor material were compared at five sampling periods in 1988, an d an assessment of correlations between the measured soluble C levels and levels of respired CO2, Co (potentially mineralizable C) and k (de cay rate) was performed. Potential release of water-soluble C followin g freeze/thaw treatment was evaluated. Sugar maple (Acer sarcharum Mar sh) leachate averaged 1.7 times more soluble C than leachate from Norw ay spruce (Picea abies (L.) Karst.), red pine (Pinus resinosa Ait.), a nd black locust (Robinia pseudoacacia L.). Average levels of soluble C for all samples in October were more than 2 times higher than those f rom July, August, September, and December, but soluble C levels did no t generally correlate with CO2 evolved during 20-day laboratory incuba tions. Correlations between soluble C and C, and k were poor. Maple su bstrate collected before autumn leaf fall and treated to alternating c ycles of freezing and thawing released significantly greater amounts o f soluble C than either controls or samples held at a constant 4 degre es C. Post-leaf fall maple substrate yielded significantly greater sol uble C values for each treatment, and treatment effects decreased in t he following order: freeze/thaw > 23 degrees C > 4 degrees C. Levels o f soluble C released from forest floor material depended on the specie s of substrate, and the degree of decomposition of the material, Cycle s of freezing and thawing released additional soluble C. Initial decom position of ''fresh'' soil organic matter by microorganisms may be tri ggered by the availability of a soluble C pool.