Forest restoration is a well-established approach for effective soil rehabilitation. However, the precise function of soil microbes at the microscale level of soil aggregates has remained unclear.

In a study published in Land Degradation & Development, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences investigated how soil microbial communities enhance soil fertility through micro-scale soil aggregates during tropical forest restoration.

The research team examined four forest types in Xishuangbanna: tropical rainforest, rubber monoculture plantation, and two restored systems (naturally restored rubber monoculture and naturally restored rubber-tea intercropping).

They conducted comparative analyses of soil physicochemical properties, microbial diversity, community structure, and co-occurrence networks across the four forest types and various soil aggregate sizes.

The results showed that restored forests create more favorable conditions, such as increased plant diversity and changes in soil pH and conductivity, which in turn stimulate microbial activity. Smaller soil aggregates act as tiny nutrient-rich fortresses, providing physical protection and resources that foster a thriving microbial ecosystem.

Compared to rubber monoculture, restored forests displayed significantly higher levels of soil organic carbon, total nitrogen, total phosphorus, pH, and electrical conductivity. Soil microaggregates in restored forests also contained the highest nutrient concentrations.

Using partial least squares path modeling (PLS-PM), the researchers identified soil microbes as the most influential factor driving improvements in soil fertility, with strong correlations between specific microbial groups and soil nutrients.

Notably, abundance of r-strategy bacteria (e.g., Proteobacteria, Bacteroidota) and K-strategy fungi (Basidiomycota) increased in restored forests. Microbial networks also grew more complex and interconnected, resembling a sophisticated underground “social network.”

These shifts in microbial life strategies and interactions are likely to enhance the production of microbial-derived organic matter, improve nutrient cycling efficiency, and facilitate ecological communication, all contributing to the accumulation of soil carbon, nitrogen, and phosphorus.

“Our findings clearly show that forest restoration and soil aggregate structure are key predictors reshaping the microbial community. Soil microbes can serve as a powerful indicator of soil resilience and health in evaluating the success of forest restoration projects,” said LIU Wenjie of XTBG.

Relationships between soil properties and microbial communities. (Image by CHEN Chunfeng)

First published: 29 September 2025