Impact of Nitrogen Deposition on Tropical Forest Biomass and Carbon Sequestration

Abstract

Undoubtedly, nitrogen (N) is an essential component of proteins and nucleic acid of cells but in the last few decades it has undergone dramatic changes. Now move nitrogen has come into circulation and thus it has now become an environmental problem. Ndeposition is not always undesirable, in areas with N- limitation , N–deposition enhances the plant growth. Besides, it sequesters more CO into the plant biomass there by 2 lowering greenhouse gas emission into the atmosphere. Forest ecosystems all around the globe have experienced N- deposition and are becoming an important C-sink which has been shown in the table 1of this review article. The C-sink capacity of forest ecosystems have been determined using many approaches which are stochiometric scaling, dynamic global vegetation models and biomass weighting method. All these method used C:N response ratio as a predictor for future rate of C-sequestration in response to N- addition. Nutrient availability increases the production of biomass per unit of photosynthesis and decreases heterotrophic respiration in forests. Nutrient availability also determines net ecosystem productivity (NEP) and ecosystem carbon use efficiency (CUE). Biomass production was found higher in the nutrient rich forests, Increase in biomass production was more in woody biomass while foliage and root biomass production remain unchanged. Indeed, the potential of forest C-sink depends upon the partitioning of the carbon uptaken during photosynthesis. In terrestrial ecosystems, C –sequestration predominantly occur in forests ecosystems. Both C:N ratio and nitrogen use efficiency (NUE) are crucial for determining C-sequestration in different forest types. C-sequestration in response to N-addition shows variation with kind of mycorrhizal association. N-deposition benefitted trees with arbuscular mycorrhizal fungi rather than ectomycorrhizal fungi. Thus, after going thoroughly across number of research articles, we arrived at the conclusion that it is the C:N ratio, NUE, forest type, nutrient availability which determine the C sequestration by forest biomass.