Soil heterogeneity significantly affects plant dynamics such as plant growth and biomass. Most studies developed soil heterogeneity in two dimensions, i.e. either horizontally or vertically. However, soil heterogeneity in natural ecosystems varies both horizontally and vertically, i.e. in three dimensions. Previous studies on plant biomass and biomass allocation rarely considered the joint effects of soil heterogeneity and species composition. Thus, to investigate such joint effects on plant biomass and biomass allocation, a controlled experiment was conducted, where three levels of soil heterogeneity and seven types of species compositions were applied. Such soil heterogeneity was developed by filling nutrient-rich and nutrient-poor substrates in an alternative pattern in pots with different patch sizes (small, medium or large), and species compositions was achieved by applying three plant species (i.e. Festuca elata, Bromus inermis, Elymus breviaristatus) in all possible combinations (growing either in monoculture or in mixtures). Results showed that patch size significantly impacted plant biomass and biomass allocation, which differed among plant species. Specially, at the pot scale, with increasing patch size, shoot biomass decreased, while root biomass and R:S ratio increased, and total biomass tended to show a unimodal pattern, where the medium patch supported higher total biomass. Moreover, at the substrate scale, more shoot biomass and total biomass were found in nutrient-rich substrate. Furthermore, at the community scale, two of the three target plant species growing in monoculture had more shoot biomass than those growing together with other species. Thus, our results indicate soil heterogeneity significantly affected plant biomass and biomass allocation, which differ among plant species, though more research is needed on the generalization on biomass allocation. We propose that soil heterogeneity should be considered more explicitly in studies with more species in long-term experiments.

中文翻译：

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三维土壤异质性和物种组成对植物生物量和草混合物生物量分配的影响

土壤异质性显着影响植物动态，例如植物生长和生物量。大多数研究在两个维度上发展了土壤异质性，即水平或垂直。然而，自然生态系统中的土壤异质性在水平和垂直方向上都有变化，即在三个维度上。以前关于植物生物量和生物量分配的研究很少考虑土壤异质性和物种组成的联合影响。因此，为了研究这种对植物生物量和生物量分配的联合影响，进行了一项对照实验，其中应用了三个土壤异质性水平和七种物种组成。这种土壤异质性是通过在具有不同斑块大小（小、中或大）的盆中以另一种模式填充营养丰富和营养贫乏的基质而形成的，物种组成是通过以所有可能的组合（单一栽培或混合栽培）应用三种植物物种（即羊茅、无芒雀麦、Elymus breviaristatus）来实现的。结果表明斑块大小显着影响植物生物量和生物量分配，植物物种之间存在差异。特别是在盆栽尺度上，随着斑块大小的增加，枝条生物量减少，而根生物量和R:S比增加，总生物量呈现单峰模式，中等斑块支持更高的总生物量。此外，在基质尺度上，在营养丰富的基质中发现了更多的枝条生物量和总生物量。此外，在群落规模上，单一栽培的三种目标植物中的两种比与其他物种一起生长的植物具有更多的枝条生物量。因此，我们的研究结果表明，土壤异质性显着影响植物生物量和生物量分配，植物物种之间存在差异，但需要对生物量分配的概括进行更多研究。我们建议在长期实验中对更多物种的研究中更明确地考虑土壤异质性。