Differential mechanisms underlying responses of soil bacterial and fungal communities to nitrogen and phosphorus inputs in a subtropical forest

Abstract

Atmospheric nitrogen (N) deposition and phosphorus (P) addition both can change soil bacterial and fungal community structure with a consequent impact on ecosystem functions. However, which factor plays an important role in regulating responses of bacterial and fungal community to N and P enrichments remains unclear. We conducted a manipulative experiment to simulate N and P inputs (10 g N · m−2 · yr−1 NH4NO3 or 10 g P · m−2 · yr−1 NaH2PO4) and compared their effects on soil bacterial and fungal species richness and community composition. The results showed that the addition of N significantly increased NH4+ and Al3+ by 99.6% and 57.4%, respectively, and consequently led to a decline in soil pH from 4.18 to 3.75 after a 5-year treatment. P addition increased Al3+ and available P by 27.0% and 10-fold, respectively, but had no effect on soil pH. N addition significantly decreased bacterial species richness and Shannon index and resulted in a substantial shift of bacterial community composition, whereas P addition did not. Neither N nor P addition changed fungal species richness, Shannon index, and fungal community composition. A structural equation model showed that the shift in bacterial community composition was related to an increase in soil acid cations. The principal component scores of soil nutrients showed a significantly positive relationship with fungal community composition. Our results suggest that N and P additions affect soil bacterial and fungal communities in different ways in subtropical forest. These findings highlight how the diversity of microbial communities of subtropical forest soil will depend on future scenarios of anthropogenic N deposition and P enrichment, with a particular sensitivity of bacterial community to N addition.

Phosphorus Reduces Negative Effects of Nitrogen Addition on Soil Microbial Communities and Functions

“…Second, soil microbial biomass was greatly promoted under NP addition in A horizon ( Supplementary Table S1). This result was coincided with the studies from P-limited old-growth tropical ecosystems [60,61], but was different from a P-unlimited subtropical forest where increased soil P availability did not change microbial biomass [62]. It is possible that the N and P were limited in A horizon for microbes in this studied forest because either N or P addition increased microbial biomass ( Supplementary Table S1).…”

Influence of Acacia mangium on Soil Fertility and Bacterial Community in Eucalyptus Plantations in the Congolese Coastal Plains

“…However, both parameters are crucial for ecosystem functioning processes linking soil, plant, and environment. Accretion in N storage previously observed [5] may have led to a decrease not only in microbial richness and diversity indices [28] but also in lighting its link to the bacterial community of the studied soils.…”

“…Despite the highest N content and the lowest C/N ratio, the lowest microbial richness and diversity indices were found in mixed-species plantations nearby Acacia even though there were no significant differences among stands. Li et al [28] reported a significant decline in bacterial species richness and diversity and a substantial shift of bacterial community composition after N addition in a subtropical deciduous oak mixed forest in China. We suggest that the loss of one or more species does not dramatically affect the functioning of the ecosystem, probably due to the high functional redundancy of soil microorganisms [72].…”

“…A better understanding of the soil microbial community in mixed and pure plantations under different soil and climate conditions is crucial to understand how soil microorganisms contribute to regulating ecosystem functioning, SOM dynamics, and nutrient cycling (C, N, S, and P). Organic C content greatly influences and drives the abundance of microorganisms in tropical forests [27], whereas N addition may induce a decline in bacterial species richness and diversity and a shift of bacterial composition [28]. Despite its negative impact on soil acidification, soil buffering capacity, and vegetation diversity, sulfur (S) has a potential to stimulate growth and to enhance the biomass of Actinobacteria, gram-positive bacteria, and fungi [29], while available P is enhanced by arbuscular mycorrhizal fungi colonization, phosphatase activities, and organic acids liberated by plants and microorganisms [30].…”

Canopy and Understory Nitrogen Addition Alters Organic Soil Bacterial Communities but Not Fungal Communities in a Temperate Forest

“…(Mueller et al, 2014;Zhao et al, 2020). Some studies found that N addition could enhance or reduce fungal diversity and alter fungal community composition (Freedman et al, 2015;Kaspari et al, 2017;Chen et al, 2018;He et al, 2021), but others showed no effect of N addition on fungal diversity and community composition (Carrara et al, 2018;Li et al, 2019;Liu et al, 2021). Several environmental factors have been used to explain the responses of soil bacterial and fungal communities to N addition, such as soil pH and N availability (Rousk et al, 2010;Lladó et al, 2017;Nie et al, 2018;Wang et al, 2018a;Liu et al, 2021).…”