EAGER: Moving Beyond the Leaf Decay Analogy: Root Trait Controls on Decomposition and Soil Carbon Dynamics

植物根系的分解还不太清楚。大量的有机碳（C）被束缚在根部，根部是植物与土壤相互作用的部分，吸收养分和水分。 并非所有的根都是一样的-它们有各种各样的形状和大小，具有不同的特性和化学成分。 该项目将首次测试关于垂死的根如何在土壤中分解，与土壤矿物质相互作用并促进森林碳循环的新想法。将使用一个实验系统来近似地下发生的事情，以便更好地了解根系分解的机制和速率。该项目将包括为肯特州立大学的本科生和研究生提供培训机会，以及通过俄亥俄州克特兰的霍尔顿植物园为小学生开展外联活动。 研究人员还将与肯特州立大学（科学学习社区，向上的约束，和俄亥俄州科学工程联盟）的既定计划协调，以吸引来自大克利夫兰地区的学生，包括那些来自代表性不足的群体和第一代大学的参与者，他们占肯特州立大学学生总数的46%。了解根系性状如何影响土壤碳动态是在本地和全球范围内准确建模的关键，因为根系提供了大部分稳定在土壤中的碳。然而，尽管根和叶之间的形态，化学成分和周围环境有明显的差异，根分解目前的概念化和建模几乎完全基于什么是已知的叶分解。细根分解发生在一个根本不同的空间尺度比叶分解，导致植物组织，分解有机体，矿物和分子之间的相互作用更密切的土壤碳稳定机制。这一建议假定，根形态是一个关键的控制分解速率，是为什么植物物种对土壤有机质库有不同的影响。 分解率预计将受到根的形态，以及根的化学性状，因为形态性状控制表面积以及可用于微生物定植的表皮中的断裂。此外，根系形态可能对根系分解过程中沉积在土壤中的有机物质的形式有另一种甚至更大的影响。据预测，具有薄而脆的一级根的植物物种更容易破碎，直接沉积为颗粒有机物，可以在土壤团聚体中进一步稳定。相比之下，厚根，耐破碎分解过程中预计将维持更大的微生物活性，伴随着生产溶解有机碳（DOC）和植物C易位到周围的土壤。 这些假设将进行测试，使用现场和控制实验室微观实验，通过测量质量损失率的根系代表梯度的性状组合，并利用C3和C4植物之间的13 C签名的差异，以跟踪根凋落物来源的C到不同的土壤C池。这项研究将测试一个新的框架连接根性状土壤碳动态在森林中。该框架弥合了以下两方面信息之间的重要差距：1）碳在土壤中稳定的物理矿物学机制，2）树根性状的分布及其与叶性状的独立性。木本丛枝菌根植物的性状特别多变，这是热带和许多落叶温带森林中的主要植物类型。根性状的生物地理和系统发育模式将有利于他们在未来的建模工作中的使用，如果土壤C动态的框架开发，更广泛地结合根性状。

The decomposition of plant roots is not well understood. A significant amount of organic carbon (C) is bound up in roots, and the roots are the part of the plant that interacts with the soil, taking up nutrients and water. Not all roots are the same - they come in a great variety of shapes and sizes, with different characteristics and chemistries. This project will, for the first time, test new ideas about how dying roots are decomposed in soil, interact with soil minerals, and contribute to forest C cycling. An experimental system will be used to approximate what is taking place underground so that the mechanisms and rates of root decomposition can be better understood. The project will involve training opportunities for undergraduate and graduate students at Kent State University, as well as outreach activities for grade school students through Holden Arboretum in Kirtland, OH. Researchers will also coordinate with established programs at Kent State University (Science Learning Community, Upward Bound, and Ohio Science & Engineering Alliance) to attract students from the greater Cleveland area, including those from under represented groups and first-generation college attendees, which make up 46% of the student body at Kent State.Understanding how root traits affect soil C dynamics is key to accurate C modeling at local and global scales because roots provide the majority of C that is stabilized in soil. However, despite obvious differences in morphology, chemical composition and surrounding environment between roots and leaves, root decomposition is currently conceptualized and modeled almost entirely based on what is known about leaf decomposition. Fine root decomposition occurs at a fundamentally different spatial scale than leaf decomposition, resulting in closer interactions between the plant tissue, decomposer organisms, and mineral and molecular mechanisms involved in soil C stabilization. This proposal posits that root morphology is a key control over decomposition rates, and is the reason why plant species have different effects on soil organic matter pools. Decomposition rate is expected to be affected by root morphology, as well as root chemical traits, because morphological traits control surface area as well as breaks in the epidermis available for microbial colonization. Moreover, root morphology likely has another, perhaps even larger, impact on the form of organic matter deposited in soil during root decomposition. It is predicted that plant species with thin and brittle first order roots are more likely to fragment, being deposited directly as particulate organic matter that can become further stabilized inside soil aggregates. By contrast, thick roots that are resistant to fragmentation during decomposition are predicted to sustain greater microbial activity, accompanied by production of dissolved organic C (DOC) and translocation of plant C to the surrounding soil. These hypotheses will be tested using field and controlled laboratory microcosm experiments, by measuring mass loss rates of root systems representing a gradient of trait combinations and by taking advantage of differences in 13C signature between C3 and C4 plants to track root litter-derived C into different soil C pools. This study will test a new framework linking root traits to soil C dynamics in forests. The framework bridges an important gap between emerging information on 1) physical-mineralogical mechanisms by which C is stabilized in soil and 2) the distribution of tree root traits and their independence from leaf traits. Traits are particularly variable for woody arbuscular mycorrhizal plants, a dominant plant type in the tropics and many deciduous temperate forests. Biogeographical and phylogenetic patterns in root traits will facilitate their use in future modeling efforts, if a framework for soil C dynamics is developed that more broadly incorporates root traits.