Evaluation of a Resource Allocation Model for Regulation of Litter Decomposition

分解是一个至关重要的生态系统过程， 植物生长所需的养分循环。 大多数现有 分解模型预测率间接形式的措施， 区域气候和凋落物化学组成。 机械论 根据微生物的实际水平， 活动仍然缺乏。 这降低了我们预测 生态系统干扰的影响，如预期的影响， 形成全球气候变化。 我们将通过以下方式解决这一问题： 评价直接基于微生物的分解模型 与分解凋落物有关的酶的产生。 我们的模式是 基于可验证的假设，即微生物种群的增长是 优化胞外酶的相对产量， 从它们中获得必需的碳（C）和氮（N）， 环境 我们认为微生物会改变 （C-获取酶的产生取决于N的可用性 环境中的化合物。 如果无机氮化合物很容易 获得，微生物应该分配更多的资源， 产生碳获取酶 这将导致更大的 微生物生长和更快的分解垃圾。 如果是无机物 氮供应不足，微生物应该产生更多的有机氮- 获取酶和分配更少的资源用于获取C 化合物. 这将导致微生物生长减少， 分解老鼠的垃圾。 为了评估这个模型，我们将放置网袋， 森林土壤样地的三种凋落叶类型。 其中一些 地块将接受两种水平的氮肥施用。 其他人不会得到氮肥。 这将提供一个 无机氮有效性的变化， 模型 在分解过程中，将收集凋落物样本， 分析了微生物生物量和几种 酶参与获得C和N形式的有机化合物。 这些 酶活性将作为衡量微生物资源的指标 分配到养分获取。 我们模型的意义 它将N的可用性与分解机制联系起来 rates. 如果得到验证， 实地研究的局限性以及提供新的信息 养分循环模型。 这些信息也应该得到改善。 我们有能力预测森林生态系统对 大气氮污染的水平，现在发现在森林附近 农业和城市地区。

Decomposition is a vital ecosystem process that results in the recycling of nutrients needed for plant growth. Most existing decomposition models predict rates indirectly form measures of regional climate and litter chemical composition. Mechanistic models of litter decay, based on the actual level of microbial activity, are still lacking. This reduces our ability to predict the effects of ecosystem disturbances such as those anticipated form global climate change. We will address this problem by evaluating a decomposition model based directly on microbial production of enzymes involved in litter breakdown. Our model is based o the testable hypothesis that microbial populations grow by optimizing the relative production of extracellular enzymes that obtain essential carbon (C) and nitrogen (N) from their environment. We propose that microbes will change the amount of (C-acquiring enzymes produced depending on the availability of N compounds in the environment. If inorganic N compounds are easily obtained, microbes should allocate more of their resources to producing C-acquiring enzymes. This should result in grater microbial growth and faster decomposition of litter. If inorganic N is in low supply, microbes should produce more organic N- acquiring enzymes and allocate less resources towards acquiring C compounds. This should result in both reduced microbial growth and decomposition rats for litter. To evaluate this model, we will place mesh bags containing three of types of leaf litter on forest soil plots. Some of these plots will receive N fertilizer at two levels of application. Others will not receive N fertilizer. This will provide a range of variation in inorganic N availability over which to test the model. During decomposition, litter samples will be collected and analyzed for microbial biomass and the activities of several enzymes involved obtaining C and N form organic compounds. These enzyme activities will serve as measures of microbial resource allocation to nutrient acquisition. The significance of our model is that it mechanistically links N availability to decomposition rates. If validated, it may facilitate assessments of nutrient limitation in field studies as well as contribute new information for nutrient cycle modeling. Such information should also improve our ability to predict forest ecosystem responses to inputs of atmospheric N pollution at levels now found in forests near agricultural and urban areas.