Environmental drivers of local abundance-mass scaling in soil animal communities

The relationship between species’ body masses and densities is strongly
conserved around a three-quarter power law when pooling data across
communities. However, studies of local within-community relationships have
revealed major deviations from this general pattern, which has profound
implications for their stability and functioning. Despite multiple
contributions of soil communities to people, there is limited knowledge on
the drivers of body mass-abundance relationships in these communities. We
compiled a dataset comprising 155 soil-animal communities across four
countries (Canada, Germany, Indonesia, USA), all sampled using the same
methodology. We tested if variation in local climatic and edaphic
conditions drives differences in local body mass-abundance scaling
relationships. We found substantial variation in the slopes of this
power-law relationship across local communities. Structural equation
modeling showed that soil temperature and water content have a positive
and negative net effect, respectively, on soil communities. These effects
are mediated by changes in local edaphic conditions (soil pH and carbon
content) and the body-mass range of the communities. These results
highlight ways in which alterations of soil climatic and edaphic
conditions interactively impact the distribution of abundance between
populations of small and large animals. These quantitative mechanistic
relationships facilitate our understanding of how global changes in
environmental conditions, such as temperature and precipitation, will
affect community-abundance distributions and thus the stability and
functioning of soil-animal communities.

当跨群落合并数据时，物种体重与种群密度之间的关系普遍符合四分之三次幂律（three-quarter power law）。然而，针对群落内局域尺度关系的研究却揭示出与该通用模式存在显著偏离，这对群落的稳定性与功能具有深远影响。尽管土壤群落对人类具有多重贡献，但学界对这类群落中体重-丰度关系（body mass-abundance relationships）的驱动因子仍知之甚少。本研究汇编了涵盖四个国家（加拿大、德国、印度尼西亚、美国）的155个土壤动物群落数据集，所有群落均采用统一方法进行采样。我们检验了局域气候与土壤理化条件（edaphic conditions）的差异是否会驱动局域体重-丰度标度关系的变化。研究发现，不同局域群落的该幂律关系斜率存在显著差异。结构方程模型（structural equation modeling）结果显示，土壤温度与含水量分别对土壤群落具有正向与负向的净效应；这类效应由局域土壤理化条件（土壤pH值与碳含量）以及群落体重范围的变化所介导。本研究结果揭示了土壤气候与土壤理化条件的改变如何通过交互作用，影响大小动物种群间的丰度分布。这些定量机制关系有助于我们理解温度、降水等全球环境变化将如何影响群落丰度分布，进而影响土壤动物群落的稳定性与功能。