Abstract
Soil erosion is prevalent in karst areas, but few studies have compared the differences in the drivers for soil microbial communities among karst ecosystems with different soil depths, and most studies have focused on the local scale. To fill this research gap, we investigated the upper 20 cm soil layers of 10 shallow–soil depth (shallow–SDC, total soil depth less than 100 cm) and 11 deep–soil depth communities (deep–SDC, total soil depth more than 100 cm), covering a broad range of vegetation types, soils, and climates. The microbial community characteristics of both the shallow–SDC and deep–SDC soils were tested by phospholipid fatty acid (PLFAs) analysis, and the key drivers of the microbial communities were illustrated by forward selection and variance partitioning analysis. Our findings demonstrated that more abundant soil nutrients supported higher fungal PLFA in shallow–SDC than in deep–SDC (p < 0.05). Furthermore, stronger correlation between the microbial community and the plant–soil system was found in shallow–SDC: the pure plant effect explained the 43.2% of variance in microbial biomass and 57.8% of the variance in the ratio of Gram–positive bacteria to Gram–negative bacteria (G+/G−), and the ratio of fungi to total bacteria (F/B); the pure soil effect accounted for 68.6% variance in the microbial diversity. The ratio of microbial PLFA cyclopropyl to precursors (Cy/Pr) and the ratio of saturated PLFA to monounsaturated PLFA (S/M) as indicators of microbial stress were controlled by pH, but high pH was not conducive to microorganisms in this area. Meanwhile, Cy/Pr in all communities was >0.1, indicating that microorganisms were under environmental stress. Therefore, the further ecological restoration of degraded karst communities is needed to improve their microbial communities.
Highlights
Introduction published maps and institutional affilSoil microorganisms play an important role in nutrient cycling and biogeochemical cycles [1]
They are expected to be heterogeneously distributed in complex soil environments, with different features affecting soil microorganisms to different extents depending on the niche they occupy [9]
We found that G+/G− and fungi to total bacteria (F/B) were positively correlated with mean annual temperature (MAT) in both soil depth communities (Figure 3, Table S10)
Summary
Soil microorganisms play an important role in nutrient cycling and biogeochemical cycles [1]. They are subject to a variety of factors, including soil properties, human activity such as reclamation [2] and forest management [3], vegetation types [4], succession stage [5]. It has been suggested that microorganisms are not homogeneously distributed in soils, even with consistently stable environments [8]. Recent studies have considered the drivers of soil microbial communities at the landscape and regional scales [14,15], and at iations. Forward selection revealed that of the factors considered in the study were seForward selection revealed that 36 of the 48 factors considered in the study were lected in the models, including background variables (MAT, elevation, sand), edaphic varselected in the models, including background variables (MAT, elevation, sand), edaphic + , NO
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