植物根系构型对花岗岩弃渣土壤有机碳组分的影响

Aims The accumulation of granite spoils destroys soil structure and increases carbon emissions. Even after ecological restoration, these soils still suffer from low stability of carbon pools. As a key interface of plant-soil-microorganism interactions, root system, particularly its architecture characteristics, significantly affect the transformation of soil organic carbon. However, the effect of root architecture on the transformation of organic carbon in granite spoil dump soils is not clear yet. Methods In this paper, we compared the organic carbon fraction contents between rhizosphere and bulk soils of the taproot system Medicago sativa (MR and MNR) and the fibrous-root system Elymus dahuricus (PR and PNR) to reveal the effects of root architecture on organic carbon fraction contents in a granite spoil dump. Furthermore, we analyzed soil physicochemical properties, enzyme activities, and bacterial community characteristics to reveal their underlying drivers. Important findings Our results showed that: (1) total organic carbon (TOC), dissolved organic carbon (DOC) and particulate organic carbon (POC) content were significantly increased by plants in both systems; (2) the rhizosphere effects on TOC and DOC were significantly higher in Elymus dahuricus (50.36% and 78.60%) than that in Medicago sativa (13.38% and -7.10%), suggesting a stronger effect on carbon enhancement in the fibrous-root system relative to the taproot system; (3) Compared to MR, PR was more effective at significantly increasing soil fast-acting nutrient content, enhancing cellulase activity, and enriching the Proteobacteria (relative abundance 41.09%), and thus creating a more suitable microenvironment for carbon accumulation; (4) correlation analysis showed that ammonium nitrogen, effective phosphorus and cellulase activity were significantly and positively correlated with TOC, DOC and POC contents. In summary, the driving effect of the fibrous-rooted Elymus dahuricus was more effective for organic carbon accumulation in granite spoil reconfigured soils compared to the taproot system Medicago sativa. This study provides theoretical support for the stabilization of organic carbon pools in granite dumps, and the screening and community allocation of ecological restoration plants.