Dissertation Research: Mechanisms of soil organic carbon interactions with black carbon

地球大气中二氧化碳含量的增加正在推动全球气候变化。由于目前土壤中的有机碳含量高于大气中的碳含量，因此土壤管理可能会影响全球气候变化的速度。热原碳是一种土壤碳，在火灾中自然产生，微生物很难分解。在某些情况下，这种热原碳（“生物炭”）可能会增加碳储量，从而减少从土壤排放到大气中的碳量。为了预测热原碳对土壤碳平衡的影响，拟议的研究将扩展现有的工作，以研究微生物和土壤类型在确定添加热原碳是否增加土壤碳储量方面的重要性。方法包括土壤培养实验，将来自美国各地的不同土壤类型与热原碳混合，以预测热原碳在各种条件下对土壤有机碳储量的影响。这将有助于改进国家和全球在模拟和预测自然有机碳循环方面的努力，并将为土地管理决策提供有用的信息，特别是那些选择规定焚烧的地方。除了这些影响外，该研究还将支持博士生的研究，培训本科生的研究，并通过讲座，一般兴趣文章，研究网站和专业会议让公众参与有机碳循环科学。热原碳（PyC）在世界土壤有机碳（SOC）中占很大比例，在某些生态系统中可达50-80%。PyC添加对已经存在的SOC的影响仍然知之甚少。在土壤中添加PyC可以增加或减少土壤有机碳的分解，而且这种相互作用的幅度甚至方向会随着时间的推移而变化。这些不同的反应表明多种机制正在发生，不同的机制可能在不同的时间尺度上起作用。研究人员将使用实验操作来确定是否改变PyC和SOC中不稳定OC的数量可以预测任何启动效应的大小和方向，使用13c标记的BC。这项博士论文改进资助将把目前的实验扩展到具有全国代表性的土壤类型，并将测试微生物群落组成（使用高通量测序分析）可用于预测PyC-SOC相互作用的假设。了解这些机制对于预测土壤中天然的PyC输入对全球C循环的影响，以及量化有意的PyC生产和管理对气候的净影响至关重要。

Increasing levels of carbon dioxide in the Earth's atmosphere are driving global climate change. Because soils currently hold more organic carbon than is present as carbon in the atmosphere, soil management can affect rates of global climate change. Pyrogenic carbon is a form of soil carbon that is produced naturally during fires that can be difficult for microbes to decompose. Under some circumstance, this pyrogenic carbon ("biochar") may increase carbon storage and thus reduce the amount of carbon that is emitted to the atmosphere from soils. In order to predict the effects of pyrogenic carbon on soil carbon balance, proposed research will expand existing work to look at the importance of microbes and soil type in determining whether addition of pyrogenic carbon increases soil carbon storage. Methods will include a soil incubation experiment, where diverse soil types from across the United States will be mixed with pyrogenic carbon to predict the effects of pyrogenic carbon on soil organic carbon storage under a variety of conditions. This will help improve national and global efforts to model and predict the natural organic carbon cycle and will provide information that can be useful for land management decisions, especially those where prescribed burning is an option. In addition to these impacts, the research will support a PhD student's research, train undergraduate students in research, and engage the public with organic carbon cycle science, through lectures, general interest articles, a research website, and professional meetings.Pyrogenic C (PyC) can comprise a large fraction of the soil organic carbon (SOC) in soils around the world, with levels up to 50-80% of SOC in some ecosystems. The effects of PyC additions on already existing SOC are still poorly understood. PyC additions to soil have been found to both increase and decrease SOC decomposition, with the magnitude and even direction of these interactions changing over time. These varied responses indicate that multiple mechanisms are occurring, with different mechanisms potentially acting over different timescales. The researchers will use experimental manipulations to determine whether varying the amount of labile OC in PyC and in SOC can predict the magnitude and direction of any priming effects, using 13C-labelled BC. This doctoral dissertation improvement grant will expand current experiments to a nationally representative set of soil types and will test the hypothesis that microbial community composition (analysed using high-throughput sequencing) can be used to predict PyC-SOC interactions. Understanding these mechanisms is essential to predict the impact of natural PyC inputs to soils on the global C cycle, and to quantifying the net climate impact of intentional PyC production and management.