| The study on carbon cycle is more and more inportant under the background of climate change, globally. With the amount of nitrogen deposition and addition is increasing, the response of carbon cycle to nitrogen input is focused by schoolars generally. However,the studies almost focused on the part of it. We try to explore the response of carbon cycle to nitrogen addition by testing the components of carbon cycle and to build the framework of carbon cycle. It is helpful to understand the response of carbon sourse and sink to nitrogen. It is also useful for the management and sustainable development based on carbon cycle.Our result showed:1. Nitrogen addition increased ANPP significantly,but had on effect on BNPP;2. Nitrogen addition did not change the 0-100cm SOC, nor the SOC in different deepth; the nitrogen addition can not increase the SOC in a short-term because of the long-term accumulation of SOC;3. Nitrogen addition increased the litter production, but the effect was not significantly;4. High level nitrogen addition improved autotrophic soil respiration but decreased the heterotrophic respiration, and low level nitrogen addition decreased autotrophic respiration significantly;5. Soil respiration had a great relationship with soil temperature, and the temperature sensitivity did not change in different levels; soil moisture had a positive relationship with the response ratio of soil respiration to nitrogen addition;6. The meadow steppe ecosystem in the east of Inner Mongolia is a carbon sink in the growing season, which could store 130gC/m2 ·year;7. Nitrogen addition is good for increasing the carbon sink by increasing the carbon sequestration and decreasing the CO2 emission; high level nitrogen addition improved NPP and soil respiration, but low level nitrogen addition decreased soil respiration and had not effect on NPP;8. We builded the carbon cycle of meadow steppe and the carbon cycle under the different level nitrogen addition. |
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