Microbial necromass carbon dominates the accumulation of soil organic carbon in bedrock-exposed areas of karst regions

Description

Our objectives were to 1) elucidate the response patterns of plant- and microbially derived necromass carbon components to bedrock exposure gradients and determine their quantitative contributions to SOC; 2) reveal the potential regulatory pathways of the biological and abiotic factors changed by the outcrop of bedrock on plant-derived and microbially derived carbon, and quantify their importance via machine learning approaches.This data reveals the variations of biological and abiotic elements with the exposure rate of bedrock.

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The environmental variables included litter properties (litter biomass (LBM), litter organic carbon (LOC), litter total nitrogen (LTN) and litter total phosphorus (LTP)); soil porosity properties (bulk density (BD) and total porosity (Tpor)); soil water-holding capacity properties (soil natural water content (SWC) and capillary water holding capacity (CWHC)); soil texture ((clay < 2 μm), silt (2–20 μm), sand (20–2000 μm)); humus (humic acid (HA), fulvic acid (FA), humin (Hu)); soil nutrients properties (soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP)); soil mineral elements (Ca2+, Ca, Fe and Al), microbial traits (microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), β-1,4-glucosidase (β-Glu), cellobiohydrolase (CBH), leucine aminopeptidase (LAP), β-1,4-N-acetylGlucosaminidase (NAG), phosphatase (AKP), and xylanase (Xyn)), and pH. The above-mentioned indicators were determined with reference to Qi et al. (2016), DeForest (2009) and Zhang and Gong (2012). The content of lignin phenol in the soil was determined by Ma et al. (2018) and Thevenot et al. (2010).The lignin phenol composition was determined by quantifying three primary groups: vanillyls (Including vanillin, acetovanillone, and vanillic acid), syringyls (Including syringaldehyde, acetosyringone, and syringic acid), and cinnamyls (Including p-coumaric acid and ferulic acid). The total lignin content was derived from the summation of these three phenolic classes. To evaluate lignin degradation patterns, four diagnostic ratios were established: the syringyl-to-vanillyl ratio (S/V), cinnamyl-to-vanillyl ratio (C/V), and acid-to-aldehyde ratios for both vanillyl (Ad/Al)v and syringyl (Ad/Al)s subgroups, following established analytical protocols (Li et al., 2020). Amino sugars include muramic acid (MurN), glucosamine (GluN), mannosamine (ManN), and galactosamine (GalN).The content of amino sugars was determined by Indorf et al. (2011) and Li et al. (2019).

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