Abundant taxa enhanced stability of fungal communities according to reduced nitrogen fertilization

Abstract

Excessive nitrogen fertilization has emerged as a significant focus of contemporary agricultural research. Reducing nitrogen fertilization is factually a process of decreasing soil nitrogen resource pulses, elucidating the environmental adaptations and ecological processes of soil fungal communities in this process, and contributions of different sub-communities in it, is a core but less known theme. We investigated soil fungal communities and subcommunities in response to reduction of nitrogen fertilization (fertilization rates were 100 %, 75 %, 50 %, and 0 %, respectively), based on a four-year field plot simulation experiment combining high-throughput sequencing technology. The diversity, community stability, environmental correlation, and co-occurrence network of soil fungal communities was analyzed, combined with concomitant alterations in soil nutrient content throughout the process of nitrogen fertilization reduction, aimed to compare the ecological impact of abundant and rare taxa on the whole soil fungal community. Our results showed that the nitrogen fertilization reduction decreased the diversity (Shannon index) and improved the stability of whole fungal communities. In addition, reduction in nitrogen fertilization leads to an improvement in soil pH (from 4.21 to 6.11) and a decrease in ammonium nitrogen and nitrate nitrogen (94.29 and 130.49 mg/kg, respectively), and abundant taxa showing higher sensitivity but less fluctuations in the breadth of the ecological niche to environmental changes. Reduced nitrogen fertilization resulted in a more complex and stable fungal network structure, while abundant taxa had less variability and higher contributions. These findings highlight the dominant role of abundant taxa in maintaining fungal community stability in facing nitrogen reduction strategies.