Abstract
At the regional scale, although environmental factors are known to shape the distributions of belowground communities in terrestrial ecosystems, these environmental factors account for relatively low percentages of the variation in belowground communities. More of this variation might be explained by considering ecosystem stable isotopic values, which can provide insight into environmental conditions. Here, we investigated ecosystem (plant and soil) δ13C and δ15N values and belowground communities (microbes and nematodes) as well as environmental factors (climates, soils, and plants) across the Mongolian Plateau. The regression analyses showed that plant isotopic values were more closely associated with belowground communities than soil isotopic values, while ecosystem δ13C values were more closely associated with the belowground communities than ecosystem δ15N values. We also found isotopic values were more closely associated with nematode communities than microbial communities. Variation partioning analyses indicated that environmental variables together explained 16–45% of total variation in belowground communities. After isotopic variables were added as predictors to the variation partition analyses, the explanation of the variance was improved by14–24% for microbial communities and was improved by 23–44% for nematode communities. These findings indicate that isotopic values could be used to predict the properties of belowground communities at a regional scale.
Highlights
Determinants of the spatial distribution of aboveground and belowground communities is a relevance issue of community ecology[1]
A recent regional-scale study showed that microbial biomass alone predicted 61% of the variance in C mineralization rates at 0–5 cm depth in mineral soils[21]. Both the ecosystem stable isotopic compositions and belowground communities have great effects on the soil C and N cycling hinted that there properly exist an inherent correlation between them, and our understanding of belowground communities could be increased by considering ecosystem stable isotopic compositions
How do the ecosystem isotopic values relate to the soil microbial and nematode communities at the regional scale? Second, after controlling for environmental variables, how much of the variance in the functional groups of the belowground microbial and nematode communities is explained by isotopic values? Third, what explains the relationships between the ecosystem isotopic values and soil microbial and nematode communities on the Mongolia Plateau?
Summary
Determinants of the spatial distribution of aboveground and belowground communities is a relevance issue of community ecology[1]. A recent regional-scale study showed that microbial biomass alone predicted 61% of the variance in C mineralization rates at 0–5 cm depth in mineral soils[21] Overall, both the ecosystem stable isotopic compositions and belowground communities have great effects on the soil C and N cycling hinted that there properly exist an inherent correlation between them, and our understanding of belowground communities could be increased by considering ecosystem stable isotopic compositions. One report has provided direct evidence regarding the relationship between isotopic values and belowground communities[24]; that report documented a positive correlation between the δ15N values and abundance of ammonia oxidizing archaea at four sites in Arizona and in Hawai’i It is still unclear whether ecosystem δ13C and δ15N values can be used to predict the spatial patterns in belowground communities along environmental gradients at a regional scale.
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