| As one of the key step in carbon cycle in terrestrial ecosystem,soil respiration is the main pathway of soil carbon pool and the major source of atmospheric C02,the small change of which might slow down or intensify the increasing speed of atmospheric C02,which might then affect the climate change.As an important part of global carbon pool,soil carbon in forests accounted for about 73 percent of soil carbon in terrestrial ecosystem.Therefore,the study on forest soil respiration is an important part of the research on missing carbon sink,including other important environmental issues such as global change.Taking the Chinese fir plantations in Huitong long term forest ecosystem research station as the research object,this research has set up four groups on twelve sample plots,including four treatments:the control group,low-N deposition group,high-N deposition group,drought stress group.In each groups,three treatments,consisting of root removal,litter removal and control,were set up with three replicates.Soil respiration rate of each sample plot are monitored periodically in each observation point to explore the response mechanism of soil respiration of Chinese fir plantation under the different circumstances such as drought and nitrogen deposition,and to provide scientific data to forest soil respiration for predictions of global carbon cycle and other studies in the future.The main research results are as follow:1.The average speeds of the total soil respiration each year in the control group are the highest(1.53 ? mol/(m2 · s),followed by those in the high-N group(1.46 ?mol/(m2·s)),and the low-N group was the lowest(1.24 ? mol/(m'·s).In the point of trend,the total soil respiration of Chinese fir plantation would be suppressed by simulating of different level of nitrogen deposition,especially more effective by stimulating low level of nitrogen deposition.Simulating different level of nitrogen deposition would change the ratio of components of the soil respiration,up to 30.1%in the low-N group,as well as increase the ratio of microbial respiration and decrease the ratio of root respiration.2.As a whole,it has a small change in the total soil respiration comparing with that in the control group,that is 1.43 ? mol/(m2 · s)to 1.53 ? mol/(m' · s).After ten months of isolated raining,the total and the components of soil respiration have showed the tendency of rising.Little removal has the slightest influence on soil respiration of Chinese fir plantations.3.Soil temperature is the major factor affecting soil respiration of Chinese fir plantations,because it could explain the changes of soil total respiration in the sample plot,from 62.4%to73.9%and the changes of Soil microbial respiration,from 55.1%to 69.5%.Under the condition of high-N,the Q10 of total soil respiration has increased to some extent,while decreased under the condition of low level of nitrogen deposition and drought.the Q10 of soil microbial respiration has increased by simulating nitrogen deposition and drought.Soil humidity has a slighter influence on soil respiration of Chinese fir plantation in sample plot relatively,which could only explain the changes of the total soil respiration from 6.2%to 22.9%and the changes of soil microbial respiration from 11.1%to 24.7%.After the simulation of nitrogen deposition of drought,the relationship between the soil humidity and soil microbial respiration are further weakened,while the relationship between the soil humidity and total soil respiration are strengthened. |
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