Linking plant ecological stoichiometry with soil nutrient and bacterial communities in apple orchards

Soil microbial community and biodiversity maintains ecosystem stability through a variety of biotic and abiotic processes. However, the relationship among environmental factors, soil bacterial community, soil nutrient content and plant ecological stoichiometry has not been clearly confirmed at a regional scale, especially in orchard ecosystems. Here we collected 36 soil and plant samples from major apple-producing areas in three climate zones (humid, semi-humid and semi-arid) to link plant ecological stoichiometry with soil nutrient and bacterial communities in apple orchards. Soil bacterial diversity and community from next-generation high-throughput sequencing, soil texture and aggregates, soil nutrient content, and plant ecological stoichiometry were determined in this study. Structural equation modelling (SEM) was used to establish the relationships among the driving factors, soil bacterial community, soil nutrient content and plant ecological stoichiometry. The results indicated that soil bacteria diversity increased and community composition varied from humid to semi-arid zones at a regional scale, showing a positive correlation with soil organic matter and soil pH. The increases in the diversity and community composition of soil bacteria could improve soil nutrient availability, which would in turn increase nutrient absorption by leaves and alter the ecological stoichiometry of trees. We demonstrated that the same vegetation showed differences in ecological stoichiometry, mainly because of the key driving factors affecting soil bacterial diversity, and also altered soil nutrient availability and absorption of nutrients by trees. Therefore, the results of this study are of great significance in elucidating the belowground and aboveground feedback in an orchard ecosystem.