Soil microbial influences over coexistence in multispecies plant communities in a subtropical forest

Soil microbes have long been recognized to substantially affect the coexistence of pairwise plant species across terrestrial ecosystems. However, projecting their impacts on the coexistence of multi-species plant systems remains a pressing challenge. To address this challenge, we conducted a greenhouse experiment with 540 seedlings of five tree species in a subtropical forest in China and evaluated microbial effects on multispecies coexistence using the structural method, which quantifies how the structure of species interactions influences the likelihood of multiple species to persist. Specifically, we grew seedlings alone or with competitors in different microbial contexts and fitted individual biomass to a population dynamic model to calculate intra- and inter-specific interaction strength with and without soil microbes. We then used these interaction structures to calculate two metrics of multispecies coexistence, structural niche differences (which promote coexistence) and structur..., We conducted the experiment in a greenhouse located at the Heishiding Natural Reserve (111°53′ E, 23°27′ N, 150–927 m elevation), Guangdong Province, south China. Our experiment included five species that vary in their relative abundance in the reserve and in mycorrhizal types: Artocarpus styracifolius (ASTY), Cryptocarya concinna (CCON), Cyclobalanopsis hui (CHUI), Castanopsis hystrix (CHYS) and Cyclobalanopsis pachyloma (CPAC) (Appendix S1: Table S1). Briefly, ASTY and CCON form root associations with arbuscular mycorrhizal fungi, and the others associate with ectomycorrhizal fungi.
In our experiment, we grew either a single individual (to measure the intrinsic growth rate) or two conspecific individuals (to measure intraspecific interaction coefficients) of each species in pots inoculated with soil from conspecific adult trees, or in pots with only sterile soil (5 species × 2 soils × 2 density levels = 20 treatments; Figure 1). Additionally, we grew each pairwise combination of speci..., , ## Description of the data and file structure

We have uploaded two datasets for statistical analysis: growth_dat.csv and raw_trait_dat.csv.

The growth_dat.csv is used to construct a Bayesian model to calculate intraspecific and interspecific interaction coefficients.

The raw_trait_dat.csv is employed for Mantel tests to explore the relationships between niche differences, fitness differences, and traits. NA indicates that the traits of the focal species were not measured.

### **growth\_dat.csv**

* **block:** The block in which the plant is located, ranging from A to F. The differences between the blocks are not significant and are not used for analysis.
* **soil_origin:** The source of the soil microbiota. ASTY, CCON, CHUI, CHYS, CPAC are abbreviations for the Latin names of five species. For instance, in the case of the species pair 'ASTY-CCON', if the soil_origin is \"ASTY\", this indicates that the soil microbes used for planting these two species originate from beneath the trees ...