Long‐term nitrogen addition modifies microbial composition and functions for slow carbon cycling and increased sequestration in tropical forest soil

• Published in: Global change biology 2019-10, Vol.25 (10), p.3267-3281
• Main Authors: Tian, Jing, Dungait, Jennifer A. J., Lu, Xiankai, Yang, Yunfeng, Hartley, Iain P., Zhang, Wei, Mo, Jiangming, Yu, Guirui, Zhou, Jizhong, Kuzyakov, Yakov
• Format: Article
• Language: English
• Subjects: Abundance; Acidic soils; Acidification; Bacteria; BASIC BIOLOGICAL SCIENCES; Biodegradation; Biodiversity; biogeochemical cycling; Biogeochemistry; C and N turnover; Carbon; Carbon Cycle; Carbon dioxide; Cellulose; Chitin; Communities; Community composition; Composition; Decomposition; Degradation; Denitrification; Deposition; Earth; Ecosystems; Efflux; Emissions; Environmental changes; Forest soils; Forests; Functional groups; Genes; global climate change; Greenhouse effect; Greenhouse gases; microbial functional community; Microorganisms; N deposition; Nitrogen; Nitrous oxide; NorB protein; Organic carbon; Organic matter; Organic soils; Phytase; Plant growth; Relative abundance; Soil; Soil acidification; Soil investigations; Soils; Storage; Temperate forests; Tropical climate; tropical forest; Tropical forests
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.14750

Nitrogen (N) deposition is a component of global change that has considerable impact on belowground carbon (C) dynamics. Plant growth stimulation and alterations of fungal community composition and functions are the main mechanisms driving soil C gains following N deposition in N‐limited temperate forests. In N‐rich tropical forests, however, N deposition generally has minor effects on plant growth; consequently, C storage in soil may strongly depend on the microbial processes that drive litter and soil organic matter decomposition. Here, we investigated how microbial functions in old‐growth tropical forest soil responded to 13 years of N addition at four rates: 0 (Control), 50 (Low‐N), 100 (Medium‐N), and 150 (High‐N) kg N ha−1 year−1. Soil organic carbon (SOC) content increased under High‐N, corresponding to a 33% decrease in CO2 efflux, and reductions in relative abundances of bacteria as well as genes responsible for cellulose and chitin degradation. A 113% increase in N2O emission was positively correlated with soil acidification and an increase in the relative abundances of denitrification genes (narG and norB). Soil acidification induced by N addition decreased available P concentrations, and was associated with reductions in the relative abundance of phytase. The decreased relative abundance of bacteria and key functional gene groups for C degradation were related to slower SOC decomposition, indicating the key mechanisms driving SOC accumulation in the tropical forest soil subjected to High‐N addition. However, changes in microbial functional groups associated with N and P cycling led to coincidentally large increases in N2O emissions, and exacerbated soil P deficiency. These two factors partially offset the perceived beneficial effects of N addition on SOC storage in tropical forest soils. These findings suggest a potential to incorporate microbial community and functions into Earth system models considering their effects on greenhouse gas emission, biogeochemical processes, and biodiversity of tropical ecosystems. N deposition is one of the global change components. We presented new biological mechanisms of soil functional response to N deposition in a tropical forest. These mechanisms are based on microbial community structure and functional groups and their potentials leading to slowing C cycling and so, to C sequestration in soil.