Fig. 3: Influencing pathways of biotic and abiotic factors on microbial carbon use efficiency (CUE) across soil horizons.
From: Patterns and drivers of soil microbial carbon use efficiency across soil depths in forest ecosystems
a–c, Structural equation models illustrating the direct and indirect effects of various factor groups on CUE in the topsoil (a), subsoil (b) and deep subsoil (c). Pentagons represent the first principal component of the corresponding factor group, derived from principal component analysis, including climate, plant biomass, physicochemical protection, substrate and microbial properties. Black dashed and solid arrows indicate significant negative and positive relationships (P < 0.05), respectively, while gray arrows indicate nonsignificant relationships (P > 0.05). Numbers adjacent to the arrows represent standardized path coefficients. Statistical significance is based on maximum likelihood tests with n = 60 independent soil samples. Asterisks indicate significant relationships. For exact P values, see Supplementary Fig. 10. Standardized total effects (sum of direct plus indirect effects) of different factor groups on microbial CUE in the topsoil (d), subsoil (e) and deep subsoil (f), as obtained from the structural equation models. Plant BC, plant biomass carbon; MAT, mean annual temperature; MAP, mean annual precipitation; AGB, aboveground biomass carbon; BGB, belowground biomass carbon; Mac, macroaggregates; Mic, microaggregates; POC, content of SOC stored in the POM fraction; MAOC, content of SOC stored in the MAOM fraction; OC-Fe, content of SOC associated with Fe oxides; Bac_div, bacterial diversity; Fun_div, fungal diversity; CAI, carbon availability index; DSOC, decomposability of SOC.
