Collaborative Research: The role of phyllosilicate minerals in mediating the temperature sensitivity of soil organic matter decomposition

土壤中含有丰富的有机碳，大部分与细粒页硅酸盐矿物（可互换地称为粘土矿物）密切相关。矿物伴生有机碳被认为是稳定的微生物呼吸，因为各种保护机制，最终减少温室气体的排放量。然而，目前预测温室效应的地球化学模型没有充分考虑这种碳储存的复杂性，模型预测往往与实验证据不符。这种模型实验的不一致性要求需要更好地了解如何以及在何种程度上矿物相关的有机碳可用于微生物分解。本项目的最终目标是研究粘土矿物在介导土壤有机质微生物分解中的作用。各种土壤有机质-粘土矿物相互作用实验将在一系列温度下在良好控制的条件下进行。实验数据将用于推导参数，这些参数可以纳入土壤地球化学模型，以更好地预测土壤有机质对温度的反应。可靠的土壤碳周转预测对于加强粮食安全、减少土壤退化和减缓生物多样性丧失至关重要。一个改进的模型预测未来的温室气体排放和环境变化将更好地使我们的社会发展可持续农业和应对最近频繁的极端天气和自然灾害。该假说假定土壤层状硅酸盐矿物控制基质的生物利用度和酶活性，因此，通过扩展，在土壤中的基质分解的温度敏感性。为了证实这一观点，研究人员建议将机械实验研究与创新的地球化学（BGC）建模相结合。他们将专注于无处不在的层状硅酸盐，因为它们在土壤中的重要性和现有的知识差距。在这个为期一年的示范项目中，他们将进行酶-碳基质-矿物相互作用（吸附）实验的实验室实验。将使用普通土壤粘土矿物。代表蛋白质、纤维素和木质素功能的有机聚合物将被选为底物替代物，β-葡萄糖苷酶、亮氨酸氨肽酶和酚氧化酶将被选为酶指示剂。将拟合动力学吸附数据以推导：1）不同底物（和酶）对矿物表面的吸附能力和亲和力;以及（2）酶-底物相互作用的Vmax和亲和力参数。这些参数和它们的温度依赖性将用于参数化平衡化学近似动力学。一个改进的BGC模型将减少目前预测土壤有机碳储量对持续变暖温度的响应的不确定性。除了通过学生参与，出版物和演示定期数据传播，结果将被纳入课程。具体内容的视频剪辑将在博物馆展出。所有调查人员将努力访问代表性不足的K-12学校，提供一般科学讲座和领导各种科学活动。

Soils contain abundant organic carbon, mostly in intimate association with fine-grained phyllosilicate minerals (interchangeably called clay minerals). Mineral-associated organic carbon is believed to be stable against microbial respiration because of various protection mechanisms, which ultimately decrease the amount of greenhouse gas emission. However, current biogeochemical models that predict greenhouse effect do not adequately consider the complexity of this carbon stock, and model prediction is often at odds with experimental evidence. This model-experiment inconsistency calls for need for an improved understanding of how and to what extent mineral-associated organic carbon is available to microbial decomposition. The ultimate goal of this project is to study the role of clay minerals in mediating microbial decomposition of soil organic matter in response to warming temperature. Various soil organic matter-clay mineral interaction experiments will be performed under well-controlled conditions across a range of temperatures. Experimental data will be used to derive parameters that can be incorporated into biogeochemical models to better predict microbial decomposition of soil organic matter in response to temperature. Reliable predictions of soil carbon turnover are essential to enhanced food security, reduced soil degradation, and mitigation of biodiversity loss. An improved model prediction of future greenhouse emission and environmental change will better enable our society to develop sustainable agriculture and to deal with recently frequent extreme weather and natural disasters.The goal of this proposal is to assess the role of phyllosilicates in mediating the temperature sensitivity of soil organic matter decomposition. The hypothesis posits that soil phyllosilicate minerals control substrate bioavailability and enzyme activity, and thus, by extension, the temperature sensitivity of substrate decomposition in soil. To corroborate this view, investigators propose to integrate mechanistic experimental investigation with innovative biogeochemical (BGC) modeling. They will focus on the ubiquitous phyllosilicates because of their importance in soils and existing knowledge gap. In this one-year demonstration project, they will perform laboratory experiments of enzyme-carbon substrate-mineral interaction (adsorption) experiments. Common soil clay minerals will be used. Organic polymers representing the functionalities of proteins, cellulose, and lignin will be selected as substrate proxies and â-glucosidase, leucine aminopeptidase, and phenol oxidase as enzyme indicators. Kinetic adsorption data will be fitted to derive: 1) the adsorption capacity and affinity of different substrates (and enzymes) onto mineral surfaces; and (2) Vmax and affinity parameters for enzyme-substrate interactions. These parameters and their temperature dependence will be used to parameterize the Equilibrium Chemistry Approximation kinetics. An improved BGC model will reduce uncertainty in current predictions of the response of soil organic carbon stocks to ongoing warming temperature. In addition of regular data dissemination through student involvement, publications, and presentations, results will be incorporated into courses. Content-specific video clips will be exhibited in museums. All investigators will make efforts to visit under-represented K-12 schools to deliver general science lectures and lead various science activities.