Crop rotational diversity enhances soil microbiome network complexity and multifunctionality

Although it is widely accepted that crop rotations can alleviate the adverse effects of agricultural intensification on ecosystem functioning, the influence of rotational diversification on soil microbial diversity, network complexity, and their associations with multifunctionality remains unclear. Here, we used a 16-year field experiment to assess the effect of six cropping regimes, and their respective crop diversity index (CDI, i.e., the number of crop species in a rotation multiplied by the species per year) and management intensity (MI, i.e., the anthropogenic inputs including fertilizer use, pesticide use and fuel consumption across a 2-year cycle), on soil microbial community (bacteria, fungi and protists) and soil multifunctionality. We used 20 soil functions related to soil properties, soil basal respiration, soil enzymatic activities and soil nitrogen cycling potential to characterize soil multifunctionality. Diversified crop rotation was shown to enhance soil multifunctionality. Also, soil multifunctionality and microbial diversity increased with CDI, but were negatively correlated or had a hump-shaped relationship with MI. With the increase in CDI, microbiome network nodes, edges and degree increased, but betweenness and average path length decreased. An increase in MI was found to have a hump-shaped relationship with the topological properties of the network. Soil microbiome network complexity had a stronger effect on multifunctionality than microbiome diversity and community composition. This study illustrates that more diverse rotations under intermediate MI promoted soil multifunctionality, and highlights the crucial role of network complexity in maintaining soil functions.

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