Soil micro-structure drives trophic interactions within micro-food webs via bottom-up regulation under different planting patterns

Abstract

Agroforestry systems, a transformative planting pattern, have the potential to enhance soil health and maintain sustainable production. Planting patterns effects on soil micro-food webs, including organisms from multiple trophic levels, remain largely ambiguous. This study interpreted the effects of Sichuan pepper-bean agroforestry system (AF) on trophic interactions among the bacteria and fungi as prey and their predators protists in comparison to no-planting system (BK), bean monoculture system (A) and Sichuan pepper economic forest monoculture system (F) using high-throughput sequencing. Results showed that compared to BK, AF significantly increased the soil pH, total carbon and nitrogen, moisture content and capillary porosity (PorC), and enhanced the diversity of soil bacteria, fungi and protists (p < 0.05). Random Forest analysis indicated the bacterial diversity was well predicted by soil biological and chemical factors (p < 0.05), but the diversity of fungi and protists was better explained by soil physical factors. Meanwhile, co-occurrence network analysis visualized the shift of soil micro-food webs with planting patterns, presenting a network complexity order AF > A > F > BK. Mantel test revealed PorC significantly influence network structures by potentially altering the capabilities of soil organisms to disperse, forage, and predate. Partial least square path model demonstrated soil micro-aggregate had the greatest effect, i.e., marginal direct effect (5.85 %) and strong indirect effect (65.33 %), on protistan communities (71.18 %). These findings indicate soil micro-structure plays a vital role in shaping trophic interactions and affecting protistan community through bottom-up regulation, which provides important implications for leveraging soil properties as a catalyst to sustain agroecosystem functions.