Dissertation Research: The Effect of Plant Community Composition and Land-use Change on Soil Microbial Community Composition and Function

土地利用变化和植物多样性及组成的变化已被证明会影响生态系统过程。然而，直到最近，很少有评价微生物群落的变化在中介过程变化中的作用。土地利用和植物多样性的变化可能改变土壤微生物群落的组成，从而改变集体生理，从而导致过程速率的差异。为了更全面地了解影响微生物群落及其功能的因素，我们的研究解决了以下问题：1)植物多样性和/或土地利用是否影响土壤微生物群落组成？2)微生物组成的这些变化是否影响养分循环速率？我们正在通过哥斯达黎加的一个实验来解决这些问题，该实验控制了植物群落的组成和多样性，以及包括森林和牧场在内的一组土地利用地点。为了解决第一个问题，我们正在使用磷脂脂肪酸分析（PLFA）和末端限制性片段长度多态性（T-RFLP）研究微生物群落组成。PLFA数据表明，微生物群落在植物多样性和土地利用梯度上存在显著差异。我们要求资金进行关键的第二个问题和测试，使用对照实验室实验，不同微生物群落的土壤在两个关键生态系统功能：硝化和凋落物分解方面是否不同。

PROJECT SUMMARYLand-use change and alterations of plant diversity and composition have been shown toinfluence ecosystem processes. Until recently, however, there has been little evaluation ofthe role of microbial community changes in mediating process change. Shifts in land-useand plant diversity may alter the composition, and thus collective physiology, of soilmicrobial communities, leading to differences in process rates. To understand more fullythe factors that influence microbial communities and their functioning, our researchaddresses the following questions: 1) Does plant diversity and/or land-use influence soilmicrobial community composition? 2) Do these changes in microbial compositioninfluence nutrient cycling rates? We are addressing these questions using an experimentin Costa Rica that manipulates plant community composition and diversity as well as aset of land-use sites, including forest and pasture. To address the first question, we areexamining microbial community composition using phospholipid fatty acid analysis(PLFA) and terminal restriction fragment length polymorphisms (T-RFLP). PLFA datasuggest that microbial communities differ significantly across plant diversity and land-use gradients. We request funds to proceed to the crucial second question and test, usingcontrolled laboratory experiments, whether soils with distinct microbial communitiesdiffer in two critical ecosystem functions: nitrification and litter decomposition.