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）被释放到大气中，是全球变暖的主要原因。土壤可以储存碳(C)，帮助抵消二氧化碳的上升，但土壤碳汇的未来是不确定的。它会被转化为土壤有机碳，可以保持数千年，还是土壤微生物将其转化为二氧化碳，再回到大气中？这是未来陆地碳汇的主要不确定性。最近的研究表明了一种令人惊讶的反应，称为启动效应，在土壤中添加C会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，这种现象是可变的，而且很难理解。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，影响了土壤的启动效应。这项研究将验证启动响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想法。因此，本研究处于地质学、生物学和化学的交叉点。该研究将调查9种土壤的启动反应，涵盖广泛的气候和环境条件。实验室实验将评估启动如何响应矿物组合的变化，实验样品将进行碳循环和微生物群落特征测试。这项工作将使用最先进的技术，包括使用空腔衰荡仪器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型稳定同位素探测技术。本项目强调科研与教学相结合，将在少数民族招生历史悠久的院校为本科生提供跨学科的培训。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政策决策有重大影响的研究领域。

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.