Quantifying the impacts of intercropping practices on above- and belowground biodiversity in China's orchards: A meta-analysis

Intercropping systems improve crop productivity through enhanced biodiversity and ecosystem functioning; however, we lack an understanding of how intercropping influences biodiversity across multiple trophic levels. This research focuses on the effects of intercropping in orchards, a practice where different crops are grown together, compared to traditional monoculture systems. The aim is to understand how intercropping influences biodiversity in both aboveground and belowground ecosystems across China. Utilizing a meta-analysis approach, the study evaluates data from 567 observations across 50 studies in China. It assesses the impacts of intercropping on various groups, including pests, predators, and parasitoids aboveground, and bacteria, fungi, and soil fauna belowground. The study also considers the role of different orchard management practices, such as types of intercropping and pesticide use. Findings show that intercropping substantially boosts biodiversity. Belowground biodiversity benefits more (abundance increased by 39 %, richness by 20 %). Specifically, aboveground predators and parasitoids see a 67 % and 29 % increase in abundance, respectively, while richness of predators increased by 11 %. Belowground fungi increased by 30 % in abundance and bacteria increased by 3 % in Shannon diversity, while soil fauna abundance and richness increased by 76 % and 29 %, respectively. Notably, the combination of fruit with grass or flowers and minimizing pesticide application proved most beneficial. Overall, our finding provides robust evidence for the positive crop diversification-biodiversity relationships in orchards across China, emphasizing that intercropping is a promising way to conserve natural enemies, soil microbial and soil fauna diversity and may contribute to biocontrol, soil improvements and crop yields.