Fire and clipping drive microbial fixation pathways in soil phosphorus and sulfur cycling in China's key karst region

Abstract

Despite growing interest in nutrient cycling genes, the influence of fire and clipping on soil microbes, phosphorus (P) and sulfur (S) cycling genes in Karst landscape remain unclear yet are critical for soil fertility in vegetation restoration landscape. Microorganisms have developed various adaptive mechanisms to improve nutrient availability in the soil in response to various landscape disturbances. In this study, we analyzed soil microbial communities and their role in mediating 90 P and 46 S genes under five fire and clipping management practices including: high-intensity fire (HIF), low-intensity fire (LIF), clipping and fire (CF), clipping (CP), and undisturbed control (CK) in Jianshui research station, Yunan province, China. The results indicated no significant (p < 0.05) differences in the predominant bacterial and fungal genera among the treatments. For bacterial compositions such as Sphingomonas, the relative abundance was highest (0.069 %) in LIF. In contrast, the relative abundance of Micromonospora was lowest (0.012 %) in LIF compared to CK. In the case of the fungal genus, Rhizophagus and Trichophyton were highest (0.187, 0.128 %) in CP and LIF respectively compared to control. Bacterial diversity was highest in CF (4.69) following the CK (4.71) while Fungal diversity was highest in CP (3.33) following the CK. P cycling genes increased in LIF, particularly those related to organic phosphoester hydrolysis and transporters, while the other treatments showed no considerable changes. S cycling genes related to S mineralization and assimilation increased in HIF and LIF, respectively, with CF showing a higher presence of sulfide cycling genes. Network analysis of P and S cycling genes indicated that S interactions formed tighter clusters under fire and clipping treatments, while P interactions had more extensive connectivity among genes. These findings underscore the distinct roles and network behaviours of P and S and provide valuable insights into the microbial mechanisms that regulate P availability and S cycling in Karst soils treated with fire and clipping. This also sheds light on the taxonomy of the microbes involved in informed decision-making in karst landscape management.