Soil microbial attributes at different spatial scales in deciduous broad-leaved forest in Qinling Mountains

We established three different spatial-scale fixed plots in Foping National Nature Reserve in the Qinling Mountains. Based on field investigation and indoor analysis, we investigated soil microbial characteristics and environmental factors in order to explore the responses of microbial phospholipid fatty acid (PLFA) biomass, microbial structure, and respiration to environmental factors. Results showed that microbial PLFA biomass did not significantly change among the three sampling scales, except actinomycete biomass was higher at the small scale compared with the other scales (P < 0.05). Similarly, microbial community structure was not significantly different, except the branched/monounsaturated PLFA ratio was significantly higher at the large scale than the small and mid-scales (P < 0.05). Pearson correlation analysis indicated that there were significant differences in the correlation between microbial characteristics and environmental factors at different spatial scales. Moreover, redundancy analysis (RDA) showed that the interpretation of microbial attributes by environmental factors differed at different spatial scales. Namely, the most important controllers of microbial attributes were soil organic carbon, water content, and dissolved nitrogen at the large scale; water content, soil organic nitrogen, and dissolved organic carbon at the mid-scale; and soil pH, total phosphorus content, and soil organic nitrogen at the small scale. Thus, our results showed that the interactions among environmental factors and degree of spatial autocorrelation increased at the small scale due to the existence of the scale effect, indicating that environmental factors had different effects on soil microorganisms at different spatial scales.