Collaborative Research: MSB-ECA: Resolving controls on lignin decomposition at the continental scale to reconcile classical and modern paradigms of soil organic matter

木质素是植物组织中的重要组成部分，由于其复杂的化学结构，可以保护植物免受食草动物和病原体的侵袭。当植物组织死亡并进入土壤时，木质素通常是最后分解的成分之一，可能会持续数十年甚至更长时间。尽管木质素的衰变速度通常很慢，但最近的研究表明，许多土壤的有机质中含有非常少的木质素。这一明显的矛盾给我们理解土壤有机质形成提出了一个关键挑战，这一主题与包括土壤肥力、水质和碳储存在内的环境服务密切相关。这项研究试图了解控制木质素衰减率的环境因素，以及整个北美生态系统中木质素对土壤有机质的最终贡献。将评估土壤微生物和矿物质的差异对不同生态系统木质素分解的影响。这些发现对生态系统功能和服务的更广泛影响将通过一个数学模型进行研究。将培训一名博士后研究人员和研究生，并通过有针对性的推广活动将研究结果传达给公众和土地管理人员。这项研究试图解决土壤有机质中挥之不去的不一致问题，在这些问题上，由于空间和方法采样偏差，木质素的特定背景重要性可能被忽视。木质素、土壤地球化学特征和微生物群落组成之间的相互作用可能会对木质素停留时间和矿物吸附产生重大影响，这些影响只有在考察大陆尺度的环境梯度时才会出现。从国家生态观测网络(NEON)站点收集的数据将与新的实验相结合，以检验两个假设：(1)土壤有机质中的木质素分解速率及其丰度是否可预测地随大陆尺度上的土壤地球化学特征和微生物群落组成而变化(与土壤有机质的经典和现代范例相反)；以及(2)在最新的机械生态系统模型中，是否可以通过包括地化和微生物参数(除了气候、残渣质量和养分有效性等传统变量之外)来改善木质素分解和碳循环的表示？霓虹灯数据将与野外和实验室培养的碳同位素标记木质素和核磁共振光谱测量相结合，以验证这些假设。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Lignin is an important component of plant tissues that provides protection from herbivores and pathogens due to its complex chemical structure. When plant tissues die and enter the soil, lignin is often among the last components to decompose and may persist for decades or even longer. Despite the generally slow decay rates of lignin, recent work has suggested that many soils contain very little lignin in their organic matter. This apparent contradiction presents a key challenge for our understanding of soil organic matter formation, a topic which is critically linked to environmental services including soil fertility, water quality, and carbon storage. This research seeks to understand the environmental factors that control lignin decay rates and the ultimate contributions of lignin to soil organic matter in ecosystems across North America. The influence of differences in soil microorganisms and minerals on lignin decomposition across diverse ecosystems will be assessed. The broader implications of the findings for ecosystem functions and services will be studied by using a mathematical model. A postdoctoral researcher and graduate students will be trained, and findings will be communicated to the public and to land managers with targeted outreach activities.This research seeks to resolve lingering inconsistencies in soil organic matter, where the context-specific importance of lignin may have been neglected due to spatial and methodological sampling biases. Interactions among lignin, soil geochemical characteristics, and microbial community composition may have significant impacts on lignin residence times and mineral sorption that emerge only when examined across continental-scale environmental gradients. Data collected from National Ecological Observatory Network (NEON) sites will be combined with new experiments to test two hypotheses: (1) Does lignin decomposition rates and its abundance in soil organic matter predictably vary with soil geochemical characteristics and microbial community composition at the continental scale (in contrast to both classical and modern paradigms of soil organic matter)?; and (2) Can the representations of lignin decomposition and carbon cycling in a state-of-the-art mechanistic ecosystem model be improved by inclusion of geochemical and microbial parameters (in addition to the traditional variables of climate, residue quality, and nutrient availability)? The NEON data will be combined with field and laboratory incubations of carbon isotope-labeled lignins and nuclear magnetic resonance spectroscopic measurements to test these hypotheses.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.