Biological carbon stabilization and destabilization: peering into microbial hot spots to understand soil carbon turnover and terrestrial energy flows

迅速增长的人口、农业集约化和气候变化正在威胁全球粮食安全。需要了解土壤碳(C)的数量、组成和稳定性，以提高土壤肥力和农业生态系统的可持续性，并建立公平和透明的方法来评估部门对减缓气候变化的贡献。虽然这一目标对减缓气候变化至关重要，但重要的是要认识到，土壤C不仅需要储存，而且还用于维持生态系统的功能。植物光合作用产物是农业生态系统土壤中新碳的主要来源，也是新能源的主要来源。土壤有机质的形成是由微生物调节的，微生物在分解过程中利用植物C，释放能量和养分。了解这些微生物转化是至关重要的。土壤有机质是土壤肥力和生产力的核心。它拥有支持植物生长、推动生物过程、为负责的生物群提供栖息地并缓冲短期压力(例如营养失衡或干旱)的碳和养分。一些微生物活动的热点，如植物残留物表面和土壤团聚体内的微站点，其活跃种群数量最高可达散装土壤的20倍。热点来自丰富的资源可获得性(例如C)。它们在时间上是动态的，很难在相关的时间和空间尺度上进行研究。为了优化碳循环过程和进行可持续的土壤管理，需要更好地了解执行分解的微生物分类群或群落特征的作用。为了更好地了解富碳热点地区碳周转的微生物动力学，拟议的研究计划将通过三个项目具体研究土壤微生物如何作为碳流动的代理人，这三个项目涉及土壤碳稳定和不稳定的微生物生态方面：1)不同农业土壤中碳利用的热力学效率与微生物群落组成之间的关系的调查；2)以富碳埋藏土壤作为模型系统，识别富碳热点地区碳稳定的指示微生物和土壤有机质生物标志物；3)对这些富碳埋藏土壤物理粒度和团聚体中的微生物群落和C周转率进行了分析，以更好地了解微生境作为C稳定的潜在热点的作用。明确地将碳纳入资源管理战略有可能极大地提高化肥的使用效率，并加强空气和水过滤、减缓气候变化和粮食生产的关键功能。换句话说，向CNPK管理框架的转变将更好地支持可持续的土壤管理，并最终支持粮食安全。

Burgeoning population, agricultural intensification and changing climate are threatening global food security. Understanding the amount, composition and stability of soil carbon (C) is needed to enhance soil fertility and agroecosystem sustainability and to establish a fair and transparent approach to evaluating sector contributions to climate change mitigation. Recently, great focus has been on storing or sequestering soil C. While this goal is critical to climate change mitigation, it is important to recognize that soil C not only needs to be stored, but also used to maintain ecosystem function. Plant photosynthate is the primary source of new C, and thus new energy, in agroecosystem soils. Formation of soil organic matter is mediated by microorganisms that utilize plant C during decomposition, releasing energy and nutrients. Understanding these microbial transformations is critical. Soil organic matter is at the heart of soil fertility and productivity. It holds C and nutrients that support plant growth, fuels biological processes, provides habitat for the biota responsible and buffers against short-term stresses (e.g. nutrient imbalance or drought).       Hot-spots of microbial activity such as plant residue surfaces and microsites within soil aggregates have active populations up to twenty times higher than the bulk soil. Hot spots arise from abundant resource availability (e.g. C). They are temporally dynamic and difficult to study at relevant scales of time and space. Improved understanding of the roles of microbial taxa or community traits that perform decomposition is needed to optimize C cycling processes and for sustainable soil management. To better understand microbial dynamics of C-turnover in C-rich hot spots, the proposed research program will specifically examine how soil microorganisms act as agents of C flows through three projects which address separate, but related aspects of microbial ecology of soil C stabilization and destabilization: 1) a survey of relationships between thermodynamic efficiency of C use and microbial community composition in different agricultural soils, 2) use C-rich buried soils as a model system to identify indicator microorganisms and SOM biomarkers for C-stabilization in C-rich hot-spots, 3) profile microbial communities and C turnover in physical size fractions and aggregates of these C-rich buried soils to better understand the role of microhabitats as potential hot-spots of C stabilization.  The interrelatedness of macronutrients nitrogen (N), phosphorus (P) and potassium (K) is acknowledged in soil fertilizer management. Explicit integration of C into resource management strategies has the potential to greatly enhance fertilizer use efficiency and to bolster critical functions of air and water filtration, climate change mitigation and food production. In other words, a shift toward a CNPK management frameworks will better support sustainable soil management and ultimately, food security.