The impacts of tillage frequency on soil micro-food web compositions and energetic structure in an agroecosystem

Soil microbes and nematodes are key components of soil micro-food webs, driving energy fluxes across trophic levels. While tillage is known to reduce microbial biomass and alter nematode communities, its impacts on energy fluxes under different tillage frequencies remain unclear, particularly in fragile karst ecosystems. To disentangle direct physical disturbances from resource-driven influences, we investigated the effects of tillage frequency on soil micro-food web composition and energetic structures. Eight treatments were set up, including original vegetation with no tillage (T0 + V), actual-maize planting with no tillage (T0 + M) and tilled every 4 months (T2 + M), and pseudo-maize planting with artificial plants simulating maize (T0) and tilled every 6, 4, 2, and 1 month(s) (T1, T2, T3, T4, respectively). Tillage after vegetation removal significantly reduced microbial biomass and nematode abundance. Energy flow uniformity was higher under low tillage frequencies (T1, T2) than under high frequencies (T3, T4). This indicates that increased tillage disrupts soil micro-food web stability. Actual-maize planting further enhanced energy flow uniformity compared to pseudo-maize planting. Additionally, tillage weakened the fungal energy channel, as shown by a decreased fungal-to-bacterial biomass ratio and reduced abundance of the fungivorous nematode family Aphelenchoididae, indicating its sensitivity to disturbance. These findings highlight that land use change from natural vegetation to cropland, combined with even low-frequency tillage, can disrupt soil biological properties in karst ecosystems. Reducing tillage frequency could help maintain soil community stability and promote sustainable agriculture.