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

氮素等营养物质在生态系统中的循环是维持农业、城市和自然土地的生物多样性和环境服务的关键过程。越来越多的证据表明，动植物相互作用的方式可以控制营养循环的速度。例如，许多植物对食草动物的损害做出反应，在它们的组织中产生防御性的抗食草动物的化学物质，以防止进一步的损害。这些防御性化合物还可以通过损害微生物分解来减缓死亡植物物质进入土壤时的氮循环速度。了解土壤养分环境如何改变植物的生长和植物防御系统的生产，对于对减少农药和化肥使用量同时最大化产量感兴趣的农学家来说至关重要。研究结果将通过旨在将生态系统动态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攸关方和小规模农民。此外，继续与当地乡镇保护委员会合作，将把研究结果直接纳入土地管理战略。结果将通过在专业会议上的陈述分享，资金将支持本科生在项目上的指导，这些项目有可能在工作产生的出版物上合作。将基因与生态系统功能联系起来是生态系统生态学最近的一个焦点，因为植物的基因决定了它的功能，因此有可能影响生态系统的过程。然而，植物的生长环境也决定了植物的基因类型，导致了不同环境条件下不同的性状表达。了解这种性状的可塑性如何与生态系统功能联系起来，对于预测环境变化将如何影响生态系统过程，如氮(N)循环，是至关重要的。食草率、结构抗草食动物防御化合物和场地肥力之间的相互作用都可以影响性状可塑性，从而影响基因和生态系统之间的联系。这些相互作用将在笼式高床花园种植的几种不同基因类型的常见草甸植物一枝黄花(Solidago Altissima)的生长环境中进行检验，该植物在不同条件下天生表达不同的抗食草动物防御能力。该试验将排除或添加Melanoplus大腿蝗虫草食动物，并排除或添加肥料。这项研究将测量在不同草食和肥料条件下生长的不同基因型的土壤微生物分解植物落叶的速度。随后的实验将测量这一过程如何改变土壤微生物群落、土壤氮素有效性以及随后的植物生长和特征。最后，15N示踪剂实验将通过跟踪土壤和植物中微生物分解释放的氮的量来测量氮的循环。综上所述，这些实验将决定植物基因型、植物抗食草动物特性的表达，还是土壤N水平最能预测生态系统中的N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.