EAGER: Investigating changes to forest soil microorganism communities due to the interactive effects of increasing soil P and pH

森林覆盖了地球表面的30%。它们支撑着地球上很大一部分活的有机体，并在全球碳和水的循环中发挥重要作用。虽然它们经常通过伐木等活动直接受到人类的影响，但也经常受到人类活动的间接威胁，例如导致酸雨和高养分沉积的活动。这些间接活动导致的土壤养分变化可能从根本上改变土壤微生物群落，进而对森林组成和过程产生影响。例如，细菌和真菌等土壤微生物可以推动植物生长，特别是与根相关的真菌可能会比其他植物更有利于某些植物物种。这项实验研究将评估土壤微生物组成和丰度如何随着土壤酸化和森林景观中磷的变化而变化，以及与根相关的微生物如何随着树冠树种的变化而变化。这项实验研究的结果可以用来预测森林将如何应对与人类影响相关的土壤养分有效性的变化。除了对研究生和本科生的传统培训外，该项目还在几个方面造福于更广泛的科学界和社会。它将动员教师和学校管理人员改善代顿地区STEM学校六年级学生的STEM教育，方法是制定项目，突出微生物生物学和土壤真菌及其重要作用和协会。它还将向私人林地所有者和专业林业员提供关于土壤肥力和森林管理的培训。以前在各种系统中的研究表明，土壤酸度对于塑造土壤微生物群落非常重要，这可能会对植物组成产生影响。土壤和与根相关的微生物对酸度的反应可能是通过土壤P的变化来促进的。尽管pH和P之间存在着重要的联系，但在森林生态系统中对pH和P的实验操作相对较少，相反，研究倾向于利用现有的养分可利用性梯度。这种对pH和P缺乏因子控制的能力限制了梳理驱动微生物对pH和其他营养物质变化的反应的机制的能力。为了充分了解磷的变化如何改变土壤微生物群落，需要研究通过改变土壤pH直接或间接地操纵土壤磷。这项拟议的研究利用了一项独特的、为期12年的森林施肥试验，通过添加石灰和/或磷肥，独立地和共同地提高了土壤pH和P的有效性。这项建议的主要目标是确定土壤磷有效性变化是否会导致微生物群落的分类和功能组成发生变化。拟议的工作试图理清这些微生物群落的生物和非生物驱动因素，并确定是否特定的门或微生物群落的关键优势菌株正在推动变化。通过这样做，建议的研究结果将有助于了解微生物对改变养分循环的贡献，并为预测了解土壤磷的有效性如何改变森林群落组成，从而影响未来的碳储存提供关键一步。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Forests cover 30% of the Earth’s surface. They support a large portion of the earth’s living organisms and play an important role in the global cycling of carbon and water. While often being directly affected by humans via activities like logging, they are also often indirectly threatened by human activities such as those that result in acid rain and high nutrient deposition. The resulting changes in soil nutrients from these indirect activities can fundamentally alter the soil microorganism community which in turn can have consequences for forest composition and processes. For example, soil microorganisms like bacteria and fungi can drive plant growth, and particular root-associated fungi can favor some plant species over others. This experimental study will evaluate how soil microbial composition and abundance change with soil acidification and with changes in phosphorus in a forested landscape and how root-associated microbes change as the canopy tree species change. The results of this experimental study can be used to predict how forests will respond to changes in soil nutrient availability associated with human influences. In addition to the traditional training of graduate and undergraduate students, this project benefits the broader scientific community and society in several ways. It will engage teachers and school administrators to improve STEM education for students in sixth grade in the Dayton Regional STEM School by developing programs to highlight microbial biology and soil fungi and their important roles and associations. It will also provide training to private woodlot owners and professional foresters about soil fertility and forest management.Previous work in a variety of systems has shown that soil acidity is important for shaping soil microorganism communities with potential consequences for plant composition. Soil and root-associated microbial responses to acidity are likely facilitated through changes in soil P. Despite this important linkage between pH and P, experimental manipulations of both pH and P in forest ecosystems are relatively rare and instead studies tend to take advantage of existing gradients in nutrient availability. This lack of factorial manipulation of pH and P limits the ability to tease apart mechanisms driving the responses of microorganisms to alterations in pH versus other nutrients . To fully understand how changing P alters the soil microorganism community,studies that manipulate soil P directly versus indirectly by changing soil pH are needed. The proposed research utilizes a unique, 12-year forest fertilization experiment that has increased soil pH and P availability independently and together, through the addition of lime and/or phosphate fertilizer. The main objective of this proposal is to determine if altered soil P availability drives changes in taxonomic and functional composition of microorganism communities. The proposed work seeks to disentangle biotic and abiotic drivers of these microbial communities and to identify whether particular phyla or key dominant strains of the microorganism community are driving changes. In doing so, outcomes from the research proposed will contribute to understanding microbial contributions to changing nutrient cycles and provide a critical step towards a predictive understanding of how soil P availability can alter forest community composition with consequences for future carbon storage.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.