The unknown soil microbial biomass stoichiometry and its potential use – C:N:P:et al.

为了在土壤中以高速率实现多种生态系统功能，例如土壤肥力和健康所需的功能，更大和更活跃的土壤微生物生物量（SMB）是有利的。通常，SMB通过氯仿熏蒸提取碳（C）、氮（N）和磷（P）来测定，这三种元素显示出稳态化学计量。然而，微生物由更多的元素组成，它们在细胞功能，生长和与生态系统服务相关的活动中发挥重要作用。但它们在SMB中的化学计量尚不清楚。根据最小量定律，生长或活动受到与所需量相比具有最低可用性的营养素的限制，尽管现在已经清楚的是，元素的共同限制是主要情况。然而，一些元素如锰可以替代其他元素，例如镁，铁和锌。C与土壤中生长和活动所需的N和P以外的元素的比例尚不清楚。最近，我们优化了氯仿熏蒸提取方法用于其他SMB元素的分析。使用这种新方法的SMB的土壤变种的两个农业土壤和相应的土壤颗粒大小的部分，即砂，粉砂和粘土，将进行分析。虽然第一种由于长期施肥处理而在营养状况上有所不同，但后者由于矿物质的多样性和相关土壤有机质的质量而有所不同。此外，在培养实验中，将以几种浓度向土壤中添加元素。通过这些方法，将检验与C：N：P相反的假设，可以替代的元素显示塑性化学计量比。测量将包括呼吸和酶活性，而鸟枪测序将能够分析元素相关的功能基因，例如编码金属蛋白的基因。将测试生物可利用元素和SMB元素的化学计量的知识是否可以用于增强微生物生长和活性。在这个项目中获得的结果将深入了解SMB的化学计量表型超越C，N和P.这方面的知识与土壤中的生物可利用元素一起，将使利益相关者能够通过添加特定浓度的特定元素来操纵土壤微生物群落，以提高土壤肥力和健康，从而提高土壤生态系统服务。

For fulfilling the diverse ecosystem functions in soil at high rates, which for instance are needed for soil fertility and health, a larger and more active soil microbial biomass (SMB) is advantageous. Commonly, SMB is determined by chloroform fumigation extraction of carbon (C), nitrogen (N), and phosphorus (P) and these three elements show a homeostatic stoichiometry. However, microorganisms consist of more elements, which play important roles in cell functioning, growth, and activities related to ecosystem services. But their stoichiometry in SMB is not known. According to the law of the minimum, growth or activity are limited by that nutrient which in relation to the amount needed has the lowest availability, though nowadays it has become clear that co-limitation of elements is the dominant case. However, some elements like manganese can substitute for others, e.g. magnesium, iron, and zinc. The ratio of C to the elements beyond N and P needed for growth and activity in soil is not known. Recently, we optimised a chloroform fumigation extraction method for analysis of other SMB elements. Using this new method the SMB of soil variants of two agricultural soils and according soil particle size fractions, i.e. sand, silt, and clay, will be analysed. While the first differ in nutritional status due to long-term fertilisation treatments, the latter differ due to diversity of minerals and in quality of associated soil organic matter. Furthermore, in incubation experiments elements will be added in several concentrations to soil. With these approaches the hypothesis will be tested that in contrast to C:N:P, elements which can be substituted for show a plastic stoichiometry. Measurements will include respiration and enzyme activity, while shotgun sequencing will enable analysis of element-related functional genes, e.g. those coding for metalloproteins. It will be tested whether the knowledge of stoichiometry of bioavailable elements and SMB elements can be used to enhance microbial growth and activity. The results obtained in this project will give insight into the stoichiometric phenotype of SMB beyond C, N, and P. This knowledge together with that of bioavailable elements in soil shall enable stakeholders to manipulate the soil microbial community by addition of specific elements in specific concentrations in order to enhance soil fertility and health and, thus, soil ecosystem services.