image: Network analysis showing the connectedness among genera of bacteria in the soils (a) under the low-N group (N0 and N135) and (b) the high-N group (N225 and N360). Nodes (colored dots) mean the genera that involved in the networks and links mean the relationship among the nodes. Red lines represent significant positive (Spearman’s correlation, r > 0.7 and P < 0.01) relationships, and blue lines denote negative (Spearman’s correlation, r < −0.7 and P < 0.01) relationships. The different colored dots represent the different phyla that the genera belong to. The numbers inside the nodes are the keystone genera (top five based on the betweenness centrality score) in the network. Unique node-level topological features of the bacterial networks in the soils of the low-N group and the high-N group (c-e), specifically the degree, closeness centrality and average shortest path length. “*”, “**”, “***” represent P < 0.05, P < 0.01 and P < 0.001, respectively.
Credit: Linchuan Fang, the Research Center of Soil and Water Conservation and Ecological Environment, Chinese Academy of Sciences and Ministry of Education
In paddy field, flood-and-drain cycles produce variations in reduced and oxidized environments, which are appropriate habitats for a wide variety of microorganisms. Nitrogen (N) fertilization drives the structure and function of soil microbial communities, which are crucial for regulating soil biogeochemical cycling and maintaining ecosystem stability. Despite the N fertilizer effects on soil microbial composition and diversity have been widely investigated, it is generally overlooked that ecosystem processes are carried out via complex associations among microbiome members. This study demonstrates that compared with low-N group (N0 and N135), the high-N group (N225 and N360) shaped more complex microbial networks. Moreover, positive links predominated across all networks, implying the importance of microbial synergism in N-enriched paddy soils. Interestingly, the proportion of negative links was increased in the high-N network. The researchers’ finding appeared December 4, 2023 in Soil Ecology Letters.
In this study, they found that the soil bacterial communities in the high-N fertilization group formed larger and more complex networks, and thus improved the stability of the microbial community. Furthermore, the PLS-PM results demonstrated that the high-N treatments had a more favorable impact on microbial network complexity than the low-N treatments, which further confirmed that high-N fertilization treatments improved the microbial network complexity in the paddy soil. A complex community interaction network was beneficial to nutrient cycling and accumulation in rice field ecosystems. Plant production, organic matter decomposition, and pathogen control are all increased in agricultural ecosystems that have stable microbial networks.
In addition, both low- and high-N additions, the microbial networks had more positive linkages than negative ones. This demonstrated the significance of microbial synergism in paddy ecosystems, as the great majority of microbial species cooperated mutually to adapt to environmental changes. However, we also observed that the proportion negative linkages increased in the high-N network, indicating that excessive N addition may enrich a number of competing microbes. A possible explanation for this finding is that more N fertilizer stimulated microbe growth, which will increase competition for nutrients.
The study emphasized that the majority of microbial species resist harsh environments through cooperation, and further advocated optimizing N fertilizer management to promote the microbial interactions for sustainable agriculture.
Journal
Soil Ecology Letters
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
High nitrogen fertilizer input enhanced the microbial network complexity in the paddy soil
Article Publication Date
4-Dec-2023