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.
Highlights
Nitrogen (N) and phosphorus (P) inputs to the ecosystem have greatly increased due to anthropogenic activities, mainly originating from fossil fuel combustion, agricultural fertilization, and dust or ash production (Galloway et al, 2008; Stevens, 2019; Wang et al, 2014)
Soil pH decreased with N addition, whereas P and NP additions did not have any effect compared to the control
N but not P addition significantly influences bacterial communities Our results showed that N addition significantly decreased bacterial Operational Taxonomic Units (OTU) richness and Shannon index and altered the bacterial community composition, with Saccharibacteria increasing, but Chloroflex decreasing in terms of their relative abundances (Figs. 2–4; Table S5)
Summary
Nitrogen (N) and phosphorus (P) inputs to the ecosystem have greatly increased due to anthropogenic activities, mainly originating from fossil fuel combustion, agricultural fertilization, and dust or ash production (Galloway et al, 2008; Stevens, 2019; Wang et al, 2014). Excessive N and P inputs could result in many adverse impacts, including soil acidification (Guo et al, 2010; Mao et al, 2017; Tian & Niu, 2015) and nutrient imbalance (Peñuelas et al, 2013), N and P have been considered limiting factors for plant growth (Harpole et al, 2011). A large body of research focusing on aboveground plant community responses have demonstrated multiple effects with nutrient additions, including biodiversity loss (Hooper et al, 2012), species composition, and associated ecosystem services, such as terrestrial carbon dynamics (Isbell et al, 2013; LeBauer & Treseder, 2008). Integrated field experimental investigations of both bacterial and fungal responses to N and P additions are needed to improve our understanding of how the soil microbial community structure shifts in response to nutrient addition and whether the bacterial and fungal responses are consistent
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