Ecological niche differentiation of detritivores dominates soil mesofaunal community assembly in a 33-year fertilized cropland

Abstract

In agricultural ecosystems, long-term fertilization significantly alters soil mesofaunal diversity and composition. However, how fertilization shifts the relative contributions of deterministic and stochastic processes in the community assembly remains unclear. We examined mesofaunal co-occurrence networks, community assembly processes, and key drivers after 33 years of fertilization. Fertilization increased diversity, particularly among detritivores. Network analysis revealed that fertilization enhanced cooperative interactions within the mesofaunal networks. These interactions were more pronounced in networks associated with inorganic and mixed fertilizers compared to organic fertilizer, indicating a potential reduction in competitive and predatory pressures and an increase in mutualistic relationships among mesofaunal taxa. Detritivores exhibited higher network centrality, indicating their pivotal role in driving enhanced network cooperation and highlighting their critical importance in maintaining soil mesofaunal diversity in fertilized croplands. Fertilization drove the assembly of soil mesofaunal communities via a combination of deterministic and stochastic processes. The proportion of deterministic processes, such as heterogeneous selection, in the mesofaunal community assembly under inorganic fertilizer treatment was larger than that under organic fertilizer treatment, whereas stochastic processes were dominant in the unfertilized treatment. Detritivores exhibited a similar pattern in their assembly. Furthermore, our results revealed that both pH, as a crucial abiotic factor, and detritivore richness, serving as a pivotal biotic factor primarily influenced community assembly. Fertilization shaped soil mesofaunal communities via resource availability and ecological interactions. In summary, our research revealed the driving processes of 33-year fertilization on soil mesofaunal community assembly and the key guilds influencing these processes, providing insights into the mechanisms shaping and maintaining soil mesofaunal diversity in fertilized croplands.