Conservation tillage impacts on soil biodiversity: Additional insights from the Collembola-associated bacteria

Abstract

The effects of conservation tillage on soil biodiversity are crucial for maintaining the balance and stability of agroecosystems, but research on soil animal-associated microbiota, an important compartment of soil biodiversity in addition to soil microbiota and soil animals, is still lacking. Here, we used 16 S rRNA amplicon sequencing to investigate the diversity and composition of bacteria associated with two Collembola species (Entomobrya sibirica and Ceratophysella sp.) of different life forms under four different tillage practices: (1) conventional moldboard plow tillage with no straw mulch (CT), (2) moldboard plow tillage with straw mulch (MT), (3) no-tillage with straw cover (NT) and (4) no-tillage with straw cover and crop rotation (NTR). We found that conservation tillage increased Collembola abundance and Collembola-associated bacterial diversity, with no significant effect on soil bacteria. Ceratophysella sp. seemed to be more adapted to NTR, whereas E. sibirica was more adapted to MT. Interestingly, Collembola abundance was positively correlated with its associated bacterial diversity, with the relative abundance of Sphingomonas and Pelomonas being positively correlated, but Pseudomonas and Rhodococcus being negatively correlated with Collembola abundance. We identified Methylobacterium-Methtylorubrum and Streptomyces as indicator bacteria for the MT treatment, but no common indicator between the two Collembola species in the NTR treatment. Conservation tillage significantly affected the composition and network structure of Collembola-associated bacteria, particularly in the MT and NTR treatments. Our study suggests that conservation tillage practices affect at least two of the three compartments of soil biodiversity – soil microbiota, soil animals and soil-animal associated microbiota. If only one tillage practice is preferred, we recommend the no-tillage with straw mulch and rotation (NTR) as the most optimal strategy for conserving soil biodiversity.