Leiyi Zhang;Yi Wu;Zhang Jie;Kumuduni Niroshika Palansooriya;Chao Liu;Rahat Shabir;Yao Hu;Qiang Sun;Wei-hui Wu;Scott X. Chan

necromass;bl;soil;paddy soil;fungal abundance;increase

Fungi play a crucial role in the utilization and storage of soil organic carbon (SOC). Biochar can potentially influence soil carbon (C) turnover by mediating extracellular electron transfer, which can be facilitated by fungi. However, the effects of biochar and soil types on the community, abundance, enzyme secretion, and necromass of fungi mediating SOC storage remain unclear. Using a mesocosm experiment, we studied the impact of biochars pyrolyzed at low (300 °C, BL) and high (700 °C, BH) temperature on fungal abundance, community composition, necromass size, and C-degrading enzyme activities in forest and paddy soils from southern China. The SOC retention ratio was higher under BL (84.0%) than under BH (76.3%). The BL (an electron shuttle) application increased fungal abundance in the forest soil by 230%. In contrast, BH (a geological capacitor) decreased fungal abundance in the paddy soil by 20.8%. Biochar addition affected fungal necromass accumulation and oxidase activity and regulated SOC turnover. The BL's high available C and moderate liming effects significantly increased fungal abundance and its necromass in the forest soil compared to the paddy soil. Moreover, after 16 weeks of incubation, BL addition decreased peroxidase activity by 32.1% in the forest soil due to the higher C use efficiency of fungi (i.e., the enrichment of Talaromyces, Umbelopsis, and Trichoderma), decreasing C-degrading enzyme secretion and reducing SOC degradation compared to the paddy soil. However, BH addition increased the Fusarium abundance, which regulated the polyphenol oxidase activity and promoted SOC degradation in the paddy soil. We conclude that biochars alter the soil environment and extracellular electron transfer to mediate fungal-driven necromass content and C-degrading enzyme activities, thus affecting SOC storage in forest and paddy soils.