Collaborative Research: Biological and mineralogical controls over soil carbon cycling across multiple ecosystems: a focus on the priming effect

当人类燃烧石油、煤炭和汽油时，二氧化碳(CO2)会释放到大气中，是全球变暖的主要原因。土壤可以储存碳(C)，帮助抵消不断上升的二氧化碳，但土壤碳汇的未来尚不确定。它会被转化为土壤有机碳，可以保持数千年不变，还是土壤微生物会将其转化为二氧化碳，并将其返回大气？这是关于陆地上未来C下沉的一个重大不确定性。最近的研究表明了一种令人惊讶的反应，称为启动效应，在这种反应中，向土壤中添加碳可以促进微生物的新陈代谢，导致它们产生比预期更多的二氧化碳。然而，这种现象是多变的，人们对此知之甚少。所提出的机制未能解释什么条件调节启动反应的发生和大小。初步数据表明，反映土壤化学和地质性质的土壤矿物组合与土壤微生物群落相互作用强烈，从而影响启动效果。这项研究将检验引发反应取决于土壤矿物组合和土壤微生物群落之间的相互作用的观点。因此，这项研究处于地质学、生物学和化学的交界处。这项研究将调查九种土壤的引发反应，跨越广泛的气候和环境条件。实验室实验将评估底漆对矿物组合变化的反应，并将测试实验样本的碳循环和微生物群落特征。这项工作将使用最先进的技术，包括使用腔衰减仪进行在线同位素比率测量，以及与能够识别执行特定生态功能的微生物的基因微阵列相结合的新的稳定同位素探测技术。该项目强调研究与教学的结合，将为有较强少数民族招生历史的院校的本科生提供跨学科培训。学生将获得尖端方法的经验，以及对全球气候变化和碳管理的政策决策具有重大影响的研究领域的经验。

Carbon dioxide (CO2) is released to the atmosphere when humans burn oil, coal, and gasoline, and is the major cause of global warming. Soils can store carbon (C), helping counteract rising carbon dioxide, but the future of the soil C sink is uncertain. Will it be converted to soil organic C, which can stay put for thousands of years, or will soil microorganisms convert it back to CO2, returning it to the atmosphere? This is a major uncertainty about the future C sink on land. Recent work suggests a surprising response, called the priming effect, in which adding C to soil boosts the metabolism of microorganisms, causing them to produce even more CO2 than expected. Yet, this phenomenon is variable and very poorly understood. Proposed mechanisms fail to explain what conditions modulate the occurrence and magnitude of the priming response. Preliminary data suggest that the soil mineral assemblage, reflecting the chemical and geological properties of soil, interacts strongly with the soil microbial community to influence the priming effect. This research will test the idea that the priming response depends on interactions between the soil mineral assemblage and the soil microbial community. Thus, this research lies at the interface among geology, biology, and chemistry. The research will investigate priming responses in nine soils, spanning a broad range of climatic and environmental conditions. Laboratory experiments will evaluate how priming responds to variation in the mineral assemblage, and samples from the experiments will be tested for carbon cycling and microbial community characteristics. The work will use state-of-the-art techniques, including in-line isotope-ratio measurements using a cavity ring-down instrument, and new stable isotope probing techniques paired with gene microarrays capable of identifying microorganisms performing specific ecological functions. This project emphasizes integrating research and teaching, will provide interdisciplinary training for undergraduate students at institutions with strong histories of minority enrollment. Students will gain experience with the cutting-edge methods, and with a research field with strong implications for policy decisions surrounding global climate change and carbon management.