Soil microorganisms are the main primary decomposers of plant material and drive biogeochemical processes like carbon and nitrogen cycles. Hence, knowledge of their nutritional demands and limitations for activity and growth is of particular importance. However, potential effects of the stoichiometry of soil and plant species on soil microbial activity and carbon use efficiency are poorly understood. Soil properties and plant traits are assumed to drive microbial carbon and community structure. We investigated the associations between C and N concentrations of leaf, root, and soil as well as their ratios and soil microbial biomass C and activity (microbial basal respiration and specific respiratory quotient) across 32 young native angiosperm tree species at two locations in Central Germany. Correlations between C:N ratios of leaves, roots, and soil were positive but overall weak. Only regressions between root and leaf C:N ratios as well as between root and soil C:N ratios were significant at one site. Soil microbial properties differed significantly between the two sites and were significantly correlated with soil C:N ratio across sites. Soil C concentrations rather than N concentrations drove significant effects of soil C:N ratio on soil microbial properties. No significant correlations between soil microbial properties and leaf as well as root C:N ratios were found. We found weak correlations of C:N ratios between plant aboveground and belowground tissues. Furthermore, microorganisms were not affected by the stoichiometry of plant tissues in the investigated young trees. The results suggest that soil stoichiometry represents a consistent determinant of soil microbial biomass and respiration. Our study indicates that stoichiometric relationships among tree organs can be weak and poor predictors of soil microbial properties in young tree stands. Further research in controlled experimental settings with a wide range of tree species is needed to study the role of plant chemical traits like the composition and stoichiometry of root exudates in determining interactions between above- and belowground compartments.

中文翻译：

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叶和根的碳氮比不能很好地预测 32 种树种的土壤微生物生物量碳和呼吸作用

土壤微生物是植物材料的主要主要分解者，并驱动生物地球化学过程，如碳和氮循环。因此，了解他们的营养需求以及活动和生长的限制是特别重要的。然而，人们对土壤和植物物种的化学计量对土壤微生物活性和碳利用效率的潜在影响知之甚少。假定土壤特性和植物性状驱动微生物碳和群落结构。我们调查了德国中部两个地点 32 种年轻的本地被子植物树种的叶片、根和土壤的 C 和 N 浓度及其比率与土壤微生物生物量 C 和活性（微生物基础呼吸和特定呼吸商）之间的关联. 叶、根的 C:N 比之间的相关性，和土壤是积极的，但整体疲软。只有根和叶 C:N 比率之间以及根和土壤 C:N 比率之间的回归在一个地点是显着的。两个站点之间的土壤微生物特性显着不同，并且与站点之间的土壤C：N比显着相关。土壤 C 浓度而不是 N 浓度推动了土壤 C:N 比对土壤微生物特性的显着影响。未发现土壤微生物特性与叶片和根系 C:N 比之间存在显着相关性。我们发现植物地上和地下组织之间的 C:N 比率的相关性较弱。此外，微生物不受所研究幼树中植物组织化学计量的影响。结果表明，土壤化学计量代表了土壤微生物生物量和呼吸作用的一致决定因素。我们的研究表明，树木器官之间的化学计量关系可能是幼树林分土壤微生物特性的弱预测因子。需要在具有广泛树种的受控实验环境中进行进一步研究，以研究植物化学特征（如根分泌物的组成和化学计量）在确定地上和地下室之间相互作用中的作用。