Long term effects of management practice intensification on soil microbial community structure and co-occurrence network in a non-timber plantation

Intensive forest plantation management practices, such as use of inorganic chemical fertilizer and herbicides improve productivity, however, their environmental impacts on plantation soil microbial communities and its interaction pattern remain unclear. In this study, we investigated associations between management practice intensities (nutrient-herbicide, nutrient-mowing and manure-mowing), environmental factors including plant coverage, pH, exchangeable calcium (Ca²⁺), aluminium ion (Al³⁺), total organic carbon (TOC), C to N ratio (C/N) and soil moisture (SM), and microbial community structure in Chinese hickory (Carya cathayenses) plantations cultivated on two soil types (calcareous and yellow soils). Our results demonstrated that long-term management practices with different intensities significantly changed certain soil environmental factors, and revealed a significant impact on both α and β-diversity of soil bacterial and fungal communities. Specifically, significant higher values of plant coverage, pH, Ca²⁺, TOC, C/N and SM and lower value of Al³⁺ were observed under manure-mowing management. Calcareous soil showed significantly higher pH, Ca²⁺ and TN contents and lower AP values than yellow soil across all three operating intensities. The bacterial community structure was different between the calcareous and yellow soil, but there was no difference for the fungi. Edaphic properties such as pH, Ca²⁺, TOC and TN were shown to play crucial roles in microbial community structuring, while vegetation-associated factors (vegetation coverage and Al³⁺) were correlated with fungal community structure. The complexity of microbe co-occurrence network decreased as management practice intensified. The keystone taxa including Bradyrhizobium, Reyranella and Phaselicystis in bacterial network and Rhizophydium and Microascales in fungal network were only observed under manure-mowing, with ecological functions mainly involved in organic carbon degradation and nitrogen fixation. Our results provide insight into the interactions between management practice intensities and soil microbial community characteristics and have implications for the optimization of sustainable forestry management practices and maintenance of microbial diversity and network complexity in over-managed forest plantations.