Decomposition of Leaf Litter in Relation to Environment, Microflora, and Microbial Respiration

Bacterial and fungal counts, mycelial growth, microbial evolution of Co₂ , and substrate moisture and temperature in bags with litter of either mulberry, redbud, white oak, loblolly pine, or beech were measured biweekly over the period November 1960—November 1961 in oak, pine, and maple stands at Oak Ridge, Tennessee. Serial dilution plate method and closed—box technique were effective for measuring microbial densities and microbial respiration respectively. Microbial densities, microbial respiration, and annual weight losses of species declined in the order mulberry, redbud, white oak, pine, beech, ad were significantly positively correlated. Stand effects were not significant possibly due to partial exclusion of stand effects in the bags. Microbial densities and moisture conditions of the various leaf species converged with time and their short—term fluctuations decreased indicating homogenation of substrate and stabilization of microbial populations. Microbial respiration was controlled in decreasing order by temperature (T), bacterial density (B), moisture (M/D), and the number of weeks (W) since leaf drop. An effective model for prediction of microbial respiration (C) is C = 46.5 + 3.2T + 26.9 M/D + 11.4 log B — 0.6W. Mean CO₂ production was 0.17 liters/g substrate decomposed. Production was higher for rapidly decomposing leaf species dominated by relatively inefficient bacterial flora than for slowly decaying litter with predominantly more efficient fungi. Loss of weight and respiration were highly correlated with a microbial population estimate, combining bacterial and fungal counts.