Soil nutrient limitation controls trophic cascade effects of micro-food web-derived ecological functions in degraded...

Soil nutrient supply drives the ecological functions of soil micro-food webs through bottom-up and top-down mechanisms in degraded agroecosystems. Nutrient limitation responds sensitively to variations in degraded agroecosystems through restoration practices, such as legume intercropping.

This study examined the effects of legume intercropping on trophic cascade dynamics through resource supply in degraded purple soil ecosystems.

A field experiment was conducted with three plantation types: Camellia oleifera monoculture (CK), C. oleifera-Arachis hypogaea (peanut) intercropping (CP), and C. oleifera-Senna tora intercropping (CS). Using soil nutrient limitation as a premise, modified by legume intercropping, we assessed the biodiversity of soil biotic taxa, analysed their community composition, and applied partial least squares path modelling (PLS-PM) to link trophic cascade with ecological functions.

Legume intercropping altered the abundance of biotic taxa, leading to changes in biotic diversity and microbial life strategies. The PLS-PM results indicated that legume intercropping enhanced bacterial diversity by aggravating soil P limitation, which subsequently increased protist consumer diversity and omnivore-predator nematode abundance through a bottom-up effect. Omnivore-predator nematodes and protist consumers indirectly influenced soil P metabolism, down-regulated through bacteria in the top-down effect. We observed high consistency between the untargeted metabolomic analysis and soil nutrient limitations. These findings indicate that soil micro-food web structure and function responded sensitively to legume intercropping in degraded ecosystems.

The results highlight the role of soil nutrient limitation in shaping micro-food webs and suggest that soil P limitation controls the down-regulation of soil P-related ecological functions through bottom-up and top-down effects.