US EPA

2283926 

Journal Article 

Nitrogen deposition weakens plant-microbe interactions in grassland ecosystems 

Wei, C; Yu, Q; Bai, E; Lü, X; Li, Q; Xia, J; Kardol, P; Liang, W; Wang, Z; Han, X 

2013 

Yes 

Global Change Biology
ISSN: 1354-1013
EISSN: 1365-2486 

WILEY 

HOBOKEN 

19 

12 

3688-3697 

English 

23925948 

10.1111/gcb.12348 

WOS:000326836000012 

Soil carbon (C) and nitrogen (N) stoichiometry is a main driver of ecosystem functioning. Global N enrichment has greatly changed soil C : N ratios, but how altered resource stoichiometry influences the complexity of direct and indirect interactions among plants, soils, and microbial communities has rarely been explored. Here, we investigated the responses of the plant-soil-microbe system to multi-level N additions and the role of dissolved organic carbon (DOC) and inorganic N stoichiometry in regulating microbial biomass in semiarid grassland in northern China. We documented a significant positive correlation between DOC and inorganic N across the N addition gradient, which contradicts the negative nonlinear correlation between nitrate accrual and DOC availability commonly observed in natural ecosystems. Using hierarchical structural equation modeling, we found that soil acidification resulting from N addition, rather than changes in the plant community, was most closely related to shifts in soil microbial community composition and decline of microbial respiration. These findings indicate a down-regulating effect of high N availability on plant-microbe interactions. That is, with the limiting factor for microbial biomass shifting from resource stoichiometry to soil acidity, N enrichment weakens the bottom-up control of soil microorganisms by plant-derived C sources. These results highlight the importance of integratively studying the plant-soil-microbe system in improving our understanding of ecosystem functioning under conditions of global N enrichment. 

aboveground-belowground linkages; compensatory effects; microbial carbon limitation; N saturation; resource stoichiometry; structural equation modeling