Crop rotation history constrains soil biodiversity and multifunctionality relationships

Human agricultural activities are recognized to play a major role in structuring soil microbial communities, which are of critical importance in terms of maintaining the multiple functions of soil (‘multifunctionality’ hereafter). However, the impact of agricultural management history on soil multifunctionality and its relationship with soil microbial diversity has not been well understood enough. To address this gap, we characterized the multifunctionality (via activity of multiple extracellular enzymes) in soils subjected to four rice rotation regimes (rice-rapeseed, rice-wheat, rice-vegetable and rice-fallow) with or without fertilization and explored the linkages between bacterial community diversity and soil multifunctionality. We found that the crop rotation history rather than fertilization explained a significant portion of the variation in soil multifunctionality (52%), bacterial species richness (69%) and community composition (61%). Bacterial diversity (species richness and weighted Unifrac dissimilarity) exhibited strong positive relationships with soil multifunctionality. In particular, bacterial diversity in the rice-rapeseed rotation had the strongest effect on the ability of the soil system to provide more functions. Partial least squares path modeling indicated that crop rotation indirectly controlled soil multifunctionality via changes in bacterial species richness and community composition, which positively affected multifunctionality mainly by regulating C cycling-related enzyme activities. This study highlights the importance of the crop rotation history in influencing soil microbial diversity and multifunctionality relationships, indicating rice rotation with rapeseed combined with fertilization can greatly improve soil multifunctionality despite the typical focus on nutrient inputs in cropland ecosystems.