Decomposition of woody litter is a major process contributing to biogeochemical cycling and productivity in forested ecosystems. Because woody litter can amount to 22% of above biomass, it represents a substantial source of nutrients for plant uptake and carbon dioxide for release to the atmosphere. However, factors affecting decomposition and rate of carbon dioxide and nutrient release from logs remain poorly known. Saprotroph colonization patterns and biodiversity, as affected by moisture content, have been ascribed and important role in the decomposition process. The importance of these factors has not been evaluated experimentally. Our objective is to evaluate the influence of log moisture content and Saprotroph community development on log decomposition and mineralization rates. We will test hypothesis that (1) initial rates of decomposition processes are determined by the depth of penetration by insects and establishment of decay vs. non-decay fungi, (2) decomposition rate is a function of moisture content of logs, and (3) decomposition rate is positively related to the diversity of the saprotroph community. We expect decomposition and mineralization rates to increase incrementally from uncolonized logs to logs penetrated by insect tunnels, to insect tunnels colonized by decay and/or non-decay fungi. These hypotheses will be tested by comparing changes in wood density and carbon/nutrient losses due to fragmentation, respiration, and leaching in Douglas-fir logs with manipulated moisture content and manipulated initial saprotroph colonization (phloem borers vs. sapwood borers, non-decay fungi vs. decay fungi). Manipulation of saprotroph establishment in decomposing logs will indicate the functional importance of biodiversity to this ecosystem process.
