DISSERTATION RESEARCH: Untangling Aboveground versus Belowground Plant Contributions to the Soil Organic Carbon Pool

陆地上最大的碳储存库是土壤，其中大部分碳来自植物。然而，尽管其重要性，调节碳从植物到土壤的运动的因素仍然知之甚少，特别是叶和茎与根的相对贡献。评估土壤碳对环境变化破坏的脆弱性取决于了解控制植物地上碳与地下碳的因素。这项博士论文改进补助金研究将提供资金进行实验室实验，以模拟植物碳向土壤的运动，并量化植物碳的来源如何决定其在土壤中的命运。例如，研究人员将评估从植物枝条进入土壤的碳是否比通过根部提供的碳更有效或更不有效。这项工作的目标是：1）改进全球碳模型，以更好地描述陆地碳循环，2）为林业，农业和其他类型的土地管理提供信息，这些土地管理正在寻求最大限度地提高土壤中植物碳的储存量。调查人员还将对学生进行培训，并与自然历史博物馆一起开展多媒体外联活动，向更广泛的公众宣传这项工作的相关性。关于地上与地下植物输入作为土壤有机碳来源的相对作用，存在着相当多的科学争论。 如果要准确地模拟陆地碳循环，就必须解决这一争论，因为初步证据表明，地上与地下输入的命运存在很大差异，这可能强烈影响土壤有机碳库的积累速度及其动态。这项研究将进行实证研究，测试支撑地上与地下植物碳途径的机制差异，独立于流经它们的碳的数量和质量。 该项目使用一系列微观实验来测试关于碳如何通过地上和地下植物途径流向土壤的机制差异的假设。常见的植物碳化合物葡萄糖（同位素标记的重稳定同位素的碳）将被添加到土壤微观世界，以评估关键的差异，地下与地上途径的土壤碳库。这项研究将加深对土壤碳如何从植物碳形成的认识，并提高模型预测未来环境条件下碳动态的能力。

The largest terrestrial reservoir of carbon is in the soil, and most of this carbon comes from plants. Yet, despite its importance, the factors that regulate the movement of carbon from plants to soils remain poorly understood, particularly the relative contribution of leaves and stems versus roots. Assessing the vulnerability of soil carbon to disruption by environmental changes depends on understanding the factors that control aboveground versus belowground carbon from plants. This Doctoral Dissertation Improvement Grant research will provide funds to conduct laboratory experiments to simulate the movement of plant carbon to the soil, and to quantify how the source of plant carbon dictates its fate in the soil. For example, the researchers will evaluate whether carbon entering the soil from the shoots of the plant is stored more or less effectively than carbon being supplied via roots. The objectives of this work are: 1) to improve global carbon models to better describe the terrestrial carbon cycle, and 2) inform practices in forestry, agriculture, and other types of land management that are looking to maximize the amount of plant carbon stored in soils. The investigators will also train students and develop multimedia outreach activities with a natural history museum to inform the broader public on the relevance of this work. Considerable scientific debate exists around the relative roles of aboveground versus belowground plant inputs as sources of soil organic carbon. This debate must be resolved if the terrestrial carbon cycle is to be accurately modeled because preliminary evidence suggests substantial differences in the fate of above- vs. belowground inputs that may strongly influence rates of accumulation of soil organic carbon pools and their dynamics. This research will conduct empirical studies that test mechanistic differences that underpin aboveground versus belowground plant carbon pathways, independent of the quantity and quality of carbon flowing through them. This project uses a series of microcosm experiments to test hypotheses about the mechanistic differences in how carbon flows through aboveground and belowground plant pathways to the soil. The common plant carbon compound glucose (isotopically labeled with the heavy stable isotope of carbon) will be added to soil microcosms to assess key differences underlying belowground versus aboveground pathways to the soil carbon pool. This research will deepen knowledge of how soil carbon is formed from plant carbon and improve the ability of models to predict carbon dynamics under future environmental conditions.