Nitrogen deposition input changes the carbon and nitrogen cycle rate significantly in terrestrial ecosystem, and then affects the structure and function of entire ecosystem. The elevated atmospheric concentration of greenhouse gases is one of the most important causes of global warming and has become an indisputable fact. Terrestrial ecosystem is the important source and sink of greenhouse gases, and plays an extremely important role in global warming. Nitrogen deposition can affect the fluxes of greenhouse gases from terrestrial ecosystem. The responses of greenhouse gases emissions to nitrogen deposition in forest ecosystem, farmland ecosystem, grassland ecosystem and wetland ecosystem of typical terrestrial ecosystem are reviewed in this paper. As a result of the differences of ecosystem types, climate, vegetational community and soil N status, the effect of nitrogen deposition on main greenhouse gases flux emissions present in three aspects: suppression, promotion and non-significant in terrestrial ecosystem.
Deyeuxia angustifolia were grown under three different levels of CO2concentration conditions, 370μmol mol-1(ambient CO2), 550μmol mol-1(elevated CO2) and 700μmol mol-1(elevated CO2) respectively. We investigated the responses of photosynthesis and growth ofD.angustifoliaunder different CO2concentration conditions. Leaf photosynthesis and chlorophyll content were checked. The results showed that the values of net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2concentration (Ci), transpiration (E), chlorophyll content were influenced by the elevated CO2concentrations. The photosynthetic parameters changed in parallel with CO2enrichment. CO2enrichment in short term improved the photosynthetic ability of leaves, whereas the capacity was weakened under long-term elevated CO2concentration condition. The leaves ofD.angustifoliagrown under elevated CO2concentrations at the end of growth, had lower Pn, Gs, Ci, E and chlorophyll content than those grown and measuered under ambient CO2concentration. The results indicated thatD.angustifoliaappeared photosynthetic acclimation.
Response of soil respiration in temperate wetlands in northeast China was studied from June 2009 to September 2011. Li-Cor 6400 infrared gas analyzer connected with a chamber was used to quantify the soil respiration. Results showed that soil respiration displayed a distinct seasonal pattern, with higher values observed in midsummer and lower values in spring and autumn. Furthermore, soil respiration exhibited a significant inter-annual variation. In addition, soil respiration presented significant positive exponential relationships with soil temperature. Whereas, significant exponential decay relationships between soil respiration rate and soil water content was found. In this ecosystem, soil temperature, soil water content and plant phenology together control soil respiration.
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