Carbon cycling of forest ecosystems in response to global nitrogen deposition: a review

Forest soils and vegetation store about 46 percent of all carbon in the terrestrial biosphere, which play a critical role in global carbon balance. Increases in atmospheric nitrogen deposition over the last several decades have altered carbon cycling and sequestration of forest ecosystems by affecting productivity and biomass accumulation in terrestrial ecosystems. Based on the studies conducted in temperate forest regions in Europe and North America, the paper reviewed mechanism and characteristics underlying the impacts of nitrogen deposition on plant photosynthesis, soil respiration, soil dissolved organic matter (DOM), and tree growth, and the uncertainties as to the interactions between forest ecosystem carbon dynamics and nitrogen deposition were also analyzed and discussed. Most tropical forests function quite differently from temperate forests with regard to N and C cycling, and that the effects of anthropogenic N inputs on tropical ecosystem processes may also differ, so it is urgent and necessary to initiate studies related to carbon-nitrogen cycle coupling in the tropical regions.