Evaluating the Endangered Mechanism and Different Conservation Effects of <em>Pinus squamata</em> from the Rhizosphere Soil Bacterial Community Perspective

Abstract

Pinus squamata is one of the most threatened conifer endemic to northeastern Yunnan Province, China, and it is prioritized as one of the Plant Species with Extremely Small Populations (PSESP) for urgent protection in China. However, we lack a comprehensive consideration of the protection effect and the endangered mechanism, especially based on the underground growth status of endangered plants. The integrated study of soil properties and rhizosphere bacteria can assist conservation to understand therequired conditions for the protection and survival of rare and endangered species. In our study, bacterial communities in wild, ex-situ, and reintroduced P. squamata rhizosphere were compared using Illumina sequencing of the V3-V4 region of the 16S rRNA genes. We determined the soil physicochemical properties, analyzed the relationships between the bacterial communities and soil physicochemical factors, and predicted the potential bacterial ecological functions. The reintroduced site Qiaojia (RQ) had the highest richness and diversity. Samples were scattered (R = 0.93, P = 0.001), indicating significant difference between the different conservation sites. Soil total potassium (TK) and available nitrogen (AN) were the main factors driving bacterial community (0.01 &amp;amp;lt; P ≤ 0.05). The low abundance of Plant growth-promoting rhizobacteria (PGPR) may be a biotic factor contributing to the endangerment of P. squamata. This study provides a foundation to assess the effect of conservation based on bacterial diversity and plant growth-promoting rhizobacteria (PGPR) to guide future research into the conservation of P. squamata.