[Effect of Biochar Addition on the Microbial Community Structure of Acidic Purple Soils Developed from Different...

Soil microorganisms are central to the material cycle in terrestrial ecosystems， and their community composition， diversity， and stability are key indicators of soil health and sustainability. Due to its unique physicochemical properties， biochar has shown potential advantages in improving acidic purple soils by enhancing soil fertility and regulating soil acidity. To investigate the effects of biochar on the improvement and microbial community structure of acidic purple soils derived from different parent materials， an indoor incubation method was adopted. Four types of acidic purple soils widely distributed in the Sichuan Basin， derived from the Shaximiao Formation， Jiaguan Formation， Penglaitown Formation， and Suining Formation， were selected as research subjects. An equal amount of biochar was added to each soil type， followed by a 63-day indoor incubation. Soil bacterial and fungal communities were measured using indoor analysis and high-throughput sequencing. The study investigated the effects of biochar on available nitrogen， base cations， and the composition and diversity of microbial communities in different acidic purple soils under the same conditions. The results showed that： ①The contents of NO₃^--N and base cations increased in all acidic purple soils with biochar addition， while the contents of NH₄⁺-N， exchangeable hydrogen （Q_H⁺）， and exchangeable aluminum （Q_Al³⁺） decreased. ②After biochar application， bacterial α-diversity was highest in the acidic purple soil from the Suining Formation， while fungal α-diversity was highest in the acidic purple sandy soil from the Jiaguan Formation. ③After biochar application， the relative abundance of Bacillus was highest in the acidic purple soil from the Shaximiao Formation， while Sphingomonas was most enriched in the acidic purple soil from the Suining Formation. In the fungal community， the relative abundance of Chaetomium was highest in the acidic purple soil from the Shaximiao Formation， and Fusarium was most enriched in the acidic purple sandy loam from the Penglaitown Formation. Based on microbial network feature analysis， the bacterial network in the acidic purple soil from the Shaximiao Formation was more complex， while the fungal network in the acidic purple sandy loam from the Penglaitown Formation was more complex. ④Correlation and redundancy analyses showed that soil organic matter （SOM） and total nitrogen （TN） were the main factors influencing the bacterial community structure， while the carbon-to-nitrogen ratio （C/N）， SOM， and available phosphorus （AP） were the main factors influencing the fungal community structure.Due to the differences in their material composition and physicochemical properties， the addition of the same amount of biochar resulted in significant variations in the soil microbial community structure among the different acidic purple soils. Therefore， the improvement and farmland fertility enhancement of different acidic purple soils should be addressed with tailored， site-specific measures.