Integrative molecular biogeochemistry of long-term litter quality and quantity controls on soil organic matter composition and persistence in temperate forests

在全球范围内，土壤储存的碳是大气的两倍。土壤碳循环是植物和微生物的碳输入和微生物呼吸（CO2通量）的碳清除以及土壤剖面中可溶性碳输出或转运之间的复杂平衡。世界森林储存了约45%的陆地碳储量，贡献了约50%的净初级生产力。最近的研究表明，这些森林及其巨大的碳储量受到人为气候变化的威胁，气候变化破坏了土壤碳的稳定，使其容易受到微生物降解和从土壤剖面输出的影响。因此，全球森林土壤碳正在下降，这将对森林的健康及其提供的重要生态服务产生负面影响。据推测，土壤碳的主要来源是植物输入和土壤沉积。因此，植被类型和数量的变化也会改变土壤碳储存过程。本项目将利用综合分子生物地球化学表征平台，研究凋落物沉积和凋落物质量变化对森林土壤碳的长期影响。作为国际研究人员网络的一部分，申请人和她的学员将研究长期的凋落物操纵如何控制凋落物沉积到土壤中的数量和质量，以及这随后如何改变土壤碳周转和生物地球化学。该项目将研究五种不同的温带森林，它们分别经历了15年、20年和30年的凋落物处理。该研究项目将首次研究凋落物输入长期变化下土壤有机质的分子水平变化，以及这种变化如何改变森林土壤碳储量。该研究项目将提供新的知识，了解土壤有机质和土壤碳是如何受凋落物输入变化的控制的，以及这些差异是如何受土壤和其他生态系统特性的控制的。该研究项目还将测量土壤有机质的变化如何通过土壤衍生碳的增溶作用改变其输出或降解的能力。这种分子水平的数据对于制定更好的森林管理战略和确保森林在不断变化的世界中的长期可持续性至关重要。当前的环境政策需要更准确的科学知识，了解土壤碳对凋落物输入的潜在变化的敏感性。因此，这项拟议的研究将提供新的信息，有助于制定未来的环境缓解战略，以保护世界各地温带森林和其他敏感生态系统的土壤碳。

Globally, soils store twice as much carbon as the atmosphere. The cycling of soil carbon is an intricate balance between carbon inputs, from plants and microbes, and removals, from microbial respiration (CO2 flux) and soluble carbon export or translocation through the soil profile. The world's forests store ~45% of terrestrial carbon stocks and contribute to ~50% of the net primary productivity. Recent studies have demonstrated that these forests and their vast carbon reserves are under threat due to anthropogenic climate change which is destabilizing soil carbon and making it susceptible to microbial degradation and export from soil profiles. As such, forest soil carbon is declining globally and this will negatively impact the health of forests and the important ecological services that they provide. It is hypothesized that a major proportion of soil carbon is derived from plant inputs and deposition to soil. Therefore, changes in vegetation type and quantity will also alter soil carbon storage processes. The proposed research program will use an integrative molecular biogeochemistry characterization platform to study the long-term impacts on forest soil carbon with changes in litter deposition and litter quality. As part of an international network of researchers, the applicant and her trainees, will study how long-term litter manipulations govern the quantity and quality of litter deposited to soil and how this subsequently alters soil carbon turnover and biogeochemistry. This program will study five different temperate forests that have undergone 15, 20, and 30 years of litter manipulation. This research program will be the first to study the molecular-level compositional changes of soil organic matter with long-term variation in litter inputs and how this alters soil carbon storage in forests. This research program will provide new knowledge on how soil organic matter and soil carbon are controlled by litter input changes through time and also how these differences are governed by soil and other ecosystem properties. This research program will also measure how changes in soil organic matter alter its ability to be exported or degraded through the solubilization of soil-derived carbon. This molecular-level data is critically needed to develop better management strategies for forests and ensure their long-term sustainability in a changing world. Current environmental policies require more accurate scientific knowledge regarding the sensitivity of soil carbon to potential shifts in litter inputs. Consequently, this proposed research will provide new information that will help shape future environmental mitigation strategies for protecting soil carbon in temperate forests and other sensitive ecosystems around the world.