Effects of climatic and soil properties on cellulose decomposition rates in temperate and tropical forests

Cellulose decomposition experiments were conducted under field conditions to analyze the effects of climatic and soil properties on rates of organic matter decomposition in temperate and tropical forests. The mass loss rates of cellulose filter papers buried in the soil surface were measured to estimate the respiratory C fluxes caused by cellulose decomposition and mean residence time (MRT) of cellulose. The rates of cellulose decomposition increased with soil temperature, except for during the dry season, while rate constants of decomposition (normalized for temperature) decreased with decreasing pH because of lower cellulase activity. The estimated MRTs of soil cellulosic carbohydrates varied from 81 to 495 days for the temperate forests and from 31 to 61 days for the tropical forests. As a major organic substrate, the C fluxes from cellulose decomposition can account for a substantial fraction of heterotrophic (basal) soil respiration. However, the respiratory C fluxes can be limited by the low substrate availability and low pH in tropical soils, despite high microbial activity. The rate-regulating factors of cellulose decomposition, i.e., temperature, soil pH, and substrate availability, can accordingly influence the rates of heterotrophic soil respiration.