Long-term nitrogen deposition enhances microbial capacities in soil carbon stabilization but reduces network complexity

Abstract

Background Anthropogenic activities have increased the inputs of atmospheric reactive nitrogen (N) into terrestrial ecosystems, affecting soil carbon stability and microbial communities. Previous studies have primarily examined the effects of nitrogen deposition on microbial taxonomy, enzymatic activities, and functional processes. Here, we examined various functional traits of soil microbial communities and how these traits are interrelated in a Mediterranean-type grassland administrated with 14 years of 7 g m−2 year−1 of N amendment, based on estimated atmospheric N deposition in areas within California, USA, by the end of the twenty-first century. Results Soil microbial communities were significantly altered by N deposition. Consistent with higher aboveground plant biomass and litter, fast-growing bacteria, assessed by abundance-weighted average rRNA operon copy number, were favored in N deposited soils. The relative abundances of genes associated with labile carbon (C) degradation (e.g., amyA and cda) were also increased. In contrast, the relative abundances of functional genes associated with the degradation of more recalcitrant C (e.g., mannanase and chitinase) were either unchanged or decreased. Compared with the ambient control, N deposition significantly reduced network complexity, such as average degree and connectedness. The network for N deposited samples contained only genes associated with C degradation, suggesting that C degradation genes became more intensely connected under N deposition. Conclusions We propose a conceptual model to summarize the mechanisms of how changes in above- and belowground ecosystems by long-term N deposition collectively lead to more soil C accumulation.

Distinct Responses of Abundant and Rare Soil Bacteria to Nitrogen Addition in Tropical Forest Soils

“…For instance, N inputs can decrease soil bacterial diversity, due to the extinction of some taxa that are adapted to nutrient-poor conditions or acidic intolerant species, following N-induced soil acidification ( 16 , 17 ). Such changes may also result in alterations of microbial community composition, activities, interactions, and their contributions to ecosystem function ( 18 – 20 ). Therefore, a deeper understanding of soil bacterial community responses to N enrichment would give a finer understanding of the potential consequences of N deposition for terrestrial ecosystem functioning ( 21 , 22 ).…”

The reciprocal changes in dominant species with complete metabolic functions explain the decoupling phenomenon of microbial taxonomic and functional composition in a grassland

“…Although reductions in the complexity of functional gene networks have been observed in other nutrient addition experiments ( Ma et al, 2022 ), co-occurrence networks with correlations can only partially explain the phenomenon and cannot clearly explain why ( Deng et al, 2012 ; Ma et al, 2022 ). In our results, networks built on individual gene do interact less with nutrient addition than with no change in overall metabolic functions.…”

Plants changed the response of bacterial community to the nitrogen and phosphorus addition ratio

“…66, 130-138. doi: 10. / j.soilbio.2013 Hu, Y., Chen, M., Yang, Z. L., Cong, M. F., Zhu, X. P., and Jia, H. T. (2022). Soil microbial community response to nitrogen application on a swamp meadow in the arid region of central Asia.…”