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

木质素是植物组织的重要组成部分，由于其复杂的化学结构，可以提供针对食草动物和病原体的保护。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，并且可能持续数十年甚至更长时间。尽管木质素的腐烂速度通常较慢，但最近的研究表明，许多土壤的有机质中含有很少的木质素。这种明显的矛盾对我们理解土壤有机质的形成提出了关键挑战，该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。这项研究旨在了解控制木质素腐烂率的环境因素以及木质素对北美生态系统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中木质素分解的影响。将使用数学模型研究研究结果对生态系统功能和服务的更广泛影响。一名博士后研究员和研究生将接受培训，研究结果将通过有针对性的外展活动传达给公众和土地管理者。这项研究旨在解决土壤有机质中长期存在的不一致问题，其中木质素的特定背景重要性可能由于空间和方法抽样偏差而被忽视。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对木质素停留时间和矿物质吸附产生重大影响，只有在跨大陆尺度的环境梯度进行检查时才会出现这种影响。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）木质素分解率及其在土壤有机质中的丰度是否可预测地随着大陆尺度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式相反）？ （2）最先进的机械生态系统模型中木质​​素分解和碳循环的表示是否可以通过纳入地球化学和微生物参数（除了气候、残留物质量和养分可用性的传统变量）来改进？ NEON 数据将与碳同位素标记木质素的现场和实验室孵化以及核磁共振光谱测量相结合，以测试这些假设。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值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.