Moisture and Saprotroph Effects on Log Decomposition Processes

木质凋落物的分解是促进森林生态系统生物地球化学循环和生产力的主要过程。由于木质凋落物可占上述生物量的22%，因此它是植物吸收营养物质和释放到大气中的二氧化碳的重要来源。然而，影响原木中二氧化碳和养分释放的分解和速率的因素仍然知之甚少。腐殖菌的定殖模式和生物多样性受到水分含量的影响，被认为在分解过程中起着重要作用。这些因素的重要性还没有经过实验评估。我们的目标是评估原木含水率和腐生生物群落发展对原木分解和矿化速率的影响。我们将检验这样的假设：(1)腐烂过程的初始速率取决于昆虫的渗透深度和腐烂真菌与非腐烂真菌的建立；(2)腐解速率是原木含水率的函数；(3)腐解速率与腐生生物群落的多样性呈正相关。我们预计腐解率和矿化率将逐渐增加，从未定居的原木到被昆虫隧道穿透的原木，再到被腐烂和/或非腐烂真菌定居的昆虫隧道。这些假设将通过比较木材密度的变化和豆杉原木中因碎裂、呼吸和淋洗而造成的碳/养分损失与操纵的含水率和操纵的初始腐殖体定居(韧皮部钻孔虫与边材钻孔虫、非腐烂真菌与腐烂真菌)进行比较来检验。在分解原木过程中操纵腐殖体的建立将表明生物多样性对这一生态系统过程的功能重要性。

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.