DISSERTATION RESEARCH: Linking phenotypic variation in plant anti-herbivore defense to spatial variation in soil nutrient pools

氮等营养物质在生态系统中的循环是维持农业、城市和自然土地生物多样性和环境服务的关键过程。越来越多的证据表明，植物和动物相互作用的方式可以控制养分循环的速度。例如，许多植物对食草动物的伤害做出反应，在它们的组织中产生防御性的抗食草动物化学物质，以抵御进一步的伤害。当死亡植物进入土壤时，这些防御性化合物还可以通过损害微生物分解来减缓氮循环速率。了解土壤养分环境如何改变植物生长和植物防御的生产，对农学家在减少农药和肥料使用的同时最大限度地提高产量至关重要。研究结果将通过一个旨在将生态系统动力学知识纳入可持续土地管理战略的讲习班和研讨会，传达给研究地点附近的当地利益相关者和小农。此外，继续与当地乡镇保护委员会合作，将研究结果直接纳入土地管理战略。研究结果将通过在专业会议上的演讲进行分享，研究经费将用于指导本科生参与有可能成为论文合著者的项目。将基因与生态系统功能联系起来是最近生态系统生态学的一个焦点，因为植物的基因型决定了它的功能，从而有可能影响生态系统过程。然而，植物基因型也受其生长环境的影响，导致不同环境条件下性状表达的差异。了解这种特征可塑性如何与生态系统功能联系起来，对于预测环境变化如何影响生态系统过程（如氮循环）至关重要。草食率、结构抗草食防御化合物和位点肥力之间的相互作用都会影响性状可塑性，从而影响基因与生态系统之间的联系。这些相互作用将在笼养床花园种植的几种不同基因型的常见草牧场植物中进行研究，这些植物在不同条件下天生表达不同的抗食草动物防御。本试验将排除或添加黑草蝗食草动物，并排除或添加肥料。该研究将测量土壤微生物在不同草食和施肥条件下对不同基因型植物凋落叶的分解速度。随后的实验将测量这一过程如何改变土壤微生物群落、土壤氮有效性以及随后的植物生长和性状。最后，15N示踪试验将通过跟踪微生物分解释放后土壤和植物中的氮量来测量氮循环。综上所述，这些实验将确定植物基因型、植物抗草食性状的表达或土壤氮水平是否能最好地预测生态系统内的氮循环。

The cycling of nutrients such as nitrogen through ecosystems is a critical process that maintains biodiversity and environmental services of agricultural, urban, and natural lands. There is increasing evidence that the way plant and animal species interact with each other could control the rate of nutrient cycling. For instance, many plants respond to herbivore damage by producing defensive anti-herbivore chemicals in their tissues to ward off further damage. These defensive compounds could also slow down the nitrogen cycling rate when dead plant material enters the soil by impairing microbial decomposition. Understanding how the soil nutrient environment changes plant growth and the production of plant defenses is of critical importance to agronomists interested in lowering pesticide and fertilizer use while maximizing yield. Results of the study will be communicated to local stakeholders and small-scale farmers near the study site through a workshop and seminar designed to integrate knowledge of ecosystem dynamics into sustainable land management strategies. In addition, continuing engagement with a local township conservation commission will incorporate study results directly into land management strategies. Results will be shared through presentations at professional meetings and funding will support the mentoring of undergraduates on projects with the potential for co-authorship on publications that arise from the work.Linking genes to ecosystem function is a recent focus in ecosystem ecology, because a plant's genotype determines how it functions and thus has the potential to impact ecosystem processes. Plant genotypes are also shaped by their growing environment, however, resulting in differential trait expression across environmental conditions. Knowing how such trait plasticity connects to ecosystem functioning is fundamental to prediction of how environmental change will influence ecosystem processes like nitrogen (N) cycling. Interactions among rates of herbivory, structural anti-herbivore defensive compounds, and site fertility can all affect trait plasticity and thus can affect the connections between genes and ecosystems. These interactions will be examined manipulating the growing environment in caged raised bed garden plantings of several different genotypes of a common meadow plant, goldenrod (Solidago altissima), which innately express anti-herbivore defenses differently under different conditions. The experiment will exclude or add Melanoplus femurrubrum grasshopper herbivores and exclude or add fertilizer. The study will measure how rapidly soil microbes decompose plant leaf litter from the genotypes grown in the different herbivory and fertilizer conditions. Subsequent experiments will measure how this processing changes soil microbial communities, soil nitrogen availability, and subsequent plant growth and traits. Finally, a 15N tracer experiment will allow measurement of nitrogen cycling by tracking the amount of nitrogen in the soil and in plants after it is released by microbial decomposition. Taken together these experiments will determine whether plant genotype, the expression of plant anti-herbivore traits, or soil N level best predicts N cycling within ecosystems.