Soil fungal community is more sensitive to nitrogen deposition than increased rainfall in a mixed deciduous forest of China

Abstract

Nitrogen (N) deposition and intensified rainfall can strongly affect soil microbial community, but compared with available studies on bacteria, those on soil fungi are quite limited. Here we carried out a field experiment in a mixed deciduous forest of China to study the influences of increased N deposition and rainfall on soil fungi by using quantitative PCR and high-throughput sequencing method. The results demonstrated that (1) N addition significantly increased fungal abundance and alpha diversity (richness, Shannon index and Invsimpson index), changed fungal community composition at OTU level, and marginally increased the relative abundance of Ascomycota and Zygomycota, while water addition showed no remarkable effects on fungal abundance, biodiversity and community composition. (2) N addition significantly increased the richness of saprotrophic fungi and pathogenic fungi, and the relative abundance of saprotrophic fungi, but water addition only slightly increased the abundance of pathogenic fungi. (3) Fungal composition dissimilarity closely correlated with the disparity of soil parameters as a whole. Soil NH 4 + -N exhibited strong positive correlation with the richness of pathogenic fungi and mycorrhizal fungi, while both soil moisture and NH 4 + -Ntightly correlated with soil fungal abundance and alpha diversity indices. We concluded that in this N-limited but non-water-limited forest ecosystem, N deposition posed stronger effects on soil fungi than increased rainfall, partially mediated by changes in soil properties.

Adaptation of Soil Fungal Community Structure and Assembly to Long- Versus Short-Term Nitrogen Addition in a Tropical Forest

“…Additionally, consistent with our first hypothesis, we observed that N addition significantly increased the fungal α-diversity at the short-term site (>10%), but little enhanced at the long-term site (<2%; Figures 2A – C ), suggesting that soil fungal species could be sensitive to short-term N addition, and may adapt to long-term N enrichment in the tropical forest. Our results are in line with some of the observations from other forest ecosystems ( Entwistle et al, 2013 ; Zhao et al, 2020 ). For instance, Zhao et al (2020) revealed that 5 years of N addition increased the fungal α-diversity in a mixed deciduous forest; while Entwistle et al (2013) showed there were no significant effects on fungal α-diversity under more than 15 years of N addition.…”

“…Our results are in line with some of the observations from other forest ecosystems ( Entwistle et al, 2013 ; Zhao et al, 2020 ). For instance, Zhao et al (2020) revealed that 5 years of N addition increased the fungal α-diversity in a mixed deciduous forest; while Entwistle et al (2013) showed there were no significant effects on fungal α-diversity under more than 15 years of N addition. Different response patterns between short- and long-term N additions in the present study could be attributed to the sensitivity of fungal species to N availability.…”

“…More often, the effects of N enrichment on fungal biomass and diversity are related to the N rates and duration of application ( Yang et al, 2019 ). Previous researches showed that short-term exogenous N enrichment could reduce or increase soil fungal community diversity ( Zhang H. et al, 2018 ; Chen et al, 2020 ; Zhao et al, 2020 ), but other studies indicated that fungal communities had the potential to adapt to the long-term N addition ( Entwistle et al, 2013 ; Freedman et al, 2015 ; Yan et al, 2021 ). Microorganisms are known for their capabilities of resistance and resilience to perturbations, but it should be noted that microbial communities are generally sensitive to environmental changes and can recover from disturbance across the time scales of days to years ( Allison and Martiny, 2008 ; Li et al, 2014 ).…”

How Do N Addition Affect Soil Fungal Community Assembly: Short- Versus Long-term Effects?

“…2a-c), suggesting that soil fungal species could be sensitive to short-term N addition, and longterm N enrichment may result in the acclimatization of the soil fungal community in the tropical forest soil. Our results are in line with some of the observations from other forest ecosystems [50,51]. For instance, Zhao et al [50] revealed that 5 years of N addition increased the fungal α-diversity in a temperate forest, while Entwistle et al [51] showed there were no significant effects on fungal α-diversity under more than 15 years of N addition.…”

“…Our results are in line with some of the observations from other forest ecosystems [50,51]. For instance, Zhao et al [50] revealed that 5 years of N addition increased the fungal α-diversity in a temperate forest, while Entwistle et al [51] showed there were no significant effects on fungal α-diversity under more than 15 years of N addition. We speculated that the different response patterns between short-and long-term N addition in the present study could be attributed to the sensitivity of fungal species to N availability and the niche differentiation.…”