DISSERTATION RESEARCH: Will Ecosystem Recovery From Acid Precipitation Jeopardize Soil Carbon Storage?

虽然酸雨在过去30年中在美国各地显著减少，但许多森林生态系统才刚刚开始恢复，预计完全恢复需要数十年至数百年。最近的证据表明，虽然森林从酸雨中恢复后会长得更好，但森林中的土壤也可能失去大量的碳和养分。 在这个博士论文改进补助金（DDIG）项目中，学生正在努力了解森林从酸雨中恢复可能增加含有土壤碳和养分的土壤有机质脆弱性的机制。研究人员特别感兴趣的是了解土壤酸度和钙含量的上升如何改变土壤碳的溶解性和不稳定性（分解性）。 该项目将通过研究土壤的物理、化学和微生物特性对酸度变化的反应来检验这一点。 这项研究对于预测整个美国东北部森林生长和碳储存的未来趋势是必要的。为了促进和告知基于证据的管理决策，这项研究将被纳入一个基于网络的应用程序，面向让公众探索和了解长期的生态数据。为了研究酸雨生态系统恢复可能改变土壤有机质（SOM）动态的机制，研究人员将进行长期的温室围隔实验。土壤将从哈伯德布鲁克实验森林收集，这是一个受酸雨影响的东北硬木森林。该团队将通过地平线重建土壤中生态系统，包括有和没有糖枫幼苗，糖枫幼苗是获得土壤的森林中的共同优势物种。将通过实验对土壤进行改良，以在完全析因设计中增加土壤pH值和Ca。学生将测量SOM溶解度和SOM的微生物呼吸，以确定SOM池对这些处理的响应。此外，研究人员将测量SOM动态的近似机制（铝-SOM络合，土壤胞外酶活性，细菌：真菌微生物生物量比等）。这可能会导致SOM溶解度和微生物呼吸的变化。这些测量将种植和未种植的围隔进行比较，以确定可能的植物介导的SOM动态的影响。

While acid rain has significantly decreased across the United States over the past thirty years, many forested ecosystems are only beginning to recover, with full recovery expected to take decades to centuries. Recent evidence suggests that, while forests will grow better as they recover from acid rain, the soil in forests may also lose a substantial amount of the carbon and nutrients. In this Doctoral Dissertation Improvement Grant (DDIG) project, the student is working to understand the mechanisms by which forest recovery from acid rain may increase the vulnerability of soil organic matter that contains soil carbon and nutrients. The investigators are particularly interested in understanding how rising soil acidity and calcium content may alter the solubility and lability (decomposability) of soil carbon. The project will test this by studying the physical, chemical and microbiological properties of soils in response to changing acidity. This research is necessary to predict future trends of forest growth and carbon storage throughout the Northeastern United States. To facilitate and inform evidence-based management decisions, this research will be incorporated into a web-based application that is geared toward letting the general public explore and understand long-term ecological data. To examine the mechanisms by which ecosystem recovery from acid rain may alter soil organic matter (SOM) dynamics, the researchers will perform a long-term greenhouse mesocosm experiment. Soils will be collected from Hubbard Brook Experimental Forest, a Northeastern hardwood forest that is impacted by acid rain. The team will reconstruct soil mesocosms by horizon, both with and without sugar maple seedlings, a co-dominant species in the forest where the soils were obtained. Soils will be experimentally amended to increase soil pH and Ca in a fully factorial design. The student will measure SOM solubility and microbial respiration of SOM to determine the responses of SOM pools to these treatments. In addition, researchers will measure proximate mechanisms of SOM dynamics (Aluminum-SOM complexation, soil exoenzyme activity, bacterial:fungal microbial biomass ratios, etc.) that may drive changes to SOM solubility and microbial respiration. These measurements will be compared between planted and unplanted mesocosm to identify possible plant-mediated effects on SOM dynamics.