DISSERTATION RESEARCH: Interactive Effects of Fern and Microbial Stoichiometry on Decomposition

植物和分解它们的微生物天生含有不同数量的元素，如碳、氮和钙。微生物群落分解植物物质所需的时间通常与植物养分浓度相关；养分浓度接近真菌和细菌的植物分解得更快。因为分解最终控制着植物的养分利用率，所以理解为什么不同类型的植物分解不同是很重要的。不同的植物群可能具有不同的营养浓度，这可能导致分解速率的差异。蕨类植物是许多陆生森林的重要组成部分，通常比被子植物分解得慢。与被子植物相比，蕨类植物似乎也缺乏营养，而那些进化得更早的蕨类物种与进化得更年轻的蕨类物种相比，也缺乏营养。为了测试养分含量对蕨类植物分解的重要性，我们将在实验室中探索蕨类植物和被子植物的分解动力学，在那里我们将操纵叶片和土壤的养分含量。随着时间的推移，微生物群落组成和叶片元素含量的测量将阐明养分含量、真菌/细菌比例、养分释放和分解率之间的相互作用。氮和钙等元素的稳定同位素可用于追踪营养物质的运动；我们将在实验的一个子集中向土壤中添加稳定同位素，从而跟踪营养物进入分解叶片的微生物运动。此外，我们还可以使用扫描电子显微镜附带的x射线直接分析微生物营养成分。这些技术将进一步阐明养分的命运以及植物和土壤养分含量对微生物养分的影响。

Plants and the microorganisms that decompose them innately contain different amounts of elements such as carbon, nitrogen and calcium. The time it takes for the microbial community to break down plant material is often correlated with plant nutrient concentrations; plants with nutrient concentrations closer to that of fungi and bacteria decompose faster. Because decomposition ultimately controls nutrient availability to plants, understanding why different types of plants decompose differently is important. Distinct plant groups can have different nutrient concentrations that may contribute to differences in decomposition rates. Ferns are a significant component of many terrestrial forests, and often decompose more slowly than angiosperms. Ferns also appear to be nutrient-poor in comparison to angiosperms, and those ferns species that evolved longer ago are nutrient-poor in comparison to evolutionarily younger fern species.In order to test the importance of nutrient content for fern decomposition, we will explore decomposition dynamics of ferns and angiosperms in the laboratory, where we will manipulate the nutrient content of both leaves and soil. Measurements of microbial community composition and leaf elemental content over time will clarify the interactions between nutrient content, fungal/bacterial ratios, and nutrient release and decomposition rates. Stable isotopes of elements such as nitrogen and calcium can be used to trace the movement of nutrients; we will add stable isotopes to the soil in a subset of the experiment, thereby tracking microbial movement of nutrients into decomposing leaves. Additionally, we plant to directly analyze microbial nutrient content using an x-ray attached to a scanning electron microscope. These techniques will further illuminate the fates of nutrients and the influence of plant and soil nutrient content on microbial nutrients.