Land-use links soil health and microbial functional traits to ecosystem productivity

Soil health underpins ecosystem functioning, yet its overarching role in underlying net primary productivity (NPP) across contrasting land-use types remains insufficiently quantified. Here, we integrated field surveys, high-throughput sequencing, and remote sensing across 177 plots spanning woodlands, grasslands, and croplands in the climatically transitional region of western Sichuan, China. We constructed a composite soil health index (SHI) encompassing biological, chemical, and physical attributes and linked it to MODIS-derived net primary productivity (NPP). SHI values in woodlands and grasslands were 3.3- and 1.6-fold higher than those in croplands. While SHI strongly correlated with NPP in croplands, this relationship was weak or absent in grasslands and woodlands, highlighting land-use-dependent controls on productivity. Random forest and structural equation models revealed that soil properties (e.g., organic carbon, available phosphorus) dominated NPP prediction in croplands, climatic factors prevailed in woodlands, and both climate and edaphic variables jointly regulated grasslands. Microbial functional guild richness exhibited distinct land-use associations: mycorrhizal and saprotrophic fungi with woodland NPP; nitrogen-fixing bacteria and chemoheterotrophs with grassland NPP; and plant pathogens with cropland NPP. Our findings demonstrate that land use restructures soil health–productivity linkages through shifts in soil fertility, climatic sensitivity, and microbial functional composition. This mechanistic framework provides a basis for developing land-use-specific soil health management strategies to sustain ecosystem productivity.