The long-term effect of elevated CO2 concentrations on needle dark respiration of two coniferous spe- cies—Pinus koraiensis and Pinus sylvestriformis on the Changbai Mountain was investigated using open-top chambers. P. koraiensis and P. sylvestriformis were exposed to 700, 500 μmol·mol-1 CO2 and ambient CO2 (approx. 350 μmol·mol-1) for four growing seasons. Needle dark respiration was meas- ured during the second, third and fourth growing seasons’ exposure to elevated CO2. The results showed that needle dark respiration rate increased for P. koraiensis and P. sylvestriformis grown at elevated CO2 concentrations during the second growing season, could be attributed to the change of carbohydrate and/or nitrogen content of needles. Needle dark respiration of P. koraiensis was stimu- lated and that of P. sylvestriformis was inhibited by elevated CO2 concentrations during the third growing season. Different response of the two tree species to elevated CO2 mainly resulted from the difference in the growth rate. Elevated CO2 concentrations inhibited needle dark respiration of both P. koraiensis and P. sylvestriformis during the fourth growing season. There was consistent trend be- tween the short-term effect and the long-term effect of elevated CO2 on needle dark respiration in P. sylvestriformis during the third growing season by changing measurement CO2 concentrations. How- ever, the short-term effect was different from the long-term effect for P. koraiensis. Response of dark respiration of P. koraiensis and P. sylvestriformis to elevated CO2 concentrations was related to the treatment time of CO2 and the stage of growth and development of plant. The change of dark respiration for the two tree species was determined by the direct effect of CO2 and long-term acclimation. The prediction of the long-term response of needle dark respiration to elevated CO2 concentration based on the short-term response is in dispute.
ZHOU YuMei1, HAN ShiJie1, ZHANG HaiSen1, XIN LiHua2 & ZHENG JunQiang1 1 Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China
A study was conducted to determine the effects of elevated CO2 on soil N process at Changbai Mountain in Jilin Province, northeastern China （42°24＂N, 128°06＂E, and 738 m elevation）. A randomized complete block design of ambient and elevated CO2 was established in an open-top chamber facility in the spring of 1999. Changpai Scotch pine （Pinus sylvestris var. sylvestriformis seeds were sowed in May, 1999 and CO2 fumigation treatments began after seeds germination. In each year, the exposure started at the end of April and stopped at the end of October. Soil samples were collected in June and August 2006 and in June 2007, and soil nitrifying, denitrifying and N2-fixing enzyme activities were measured. Results show that soil nitrifying enzyme activities （NEA） in the 5-10 cm soil layer were significantly increased at elevated CO2 by 30.3% in June 2006, by 30.9% in August 2006 and by 11.3% in June 2007. Soil denitrifying enzyme activities （DEA） were significantly decreased by elevated CO2 treatment in June 2006 （P 〈 0.012） and August 2006 （P 〈 0.005） samplings in our study; no significant difference was detected in June 2007, and no significant changes in N2-fixing enzyme activity were found. This study suggests that elevated CO2 can alter soil nitrifying enzyme and denitrifying enzyme activities.
采用DGGE（Denaturing Gradient Gel Electrophoresis）技术，于2003年的7-9月中旬对高浓度CO2（700和500μmol·mol^-1）处理下的红松幼苗根际和根外0-10cm土壤微生物群落结构进行了研究．结果表明，大气CO2浓度升高对红松根际和非根际土壤细菌群落结构产生了较大的影响，主要表现为部分细菌物种的出现，或原有细菌数量的丰富以及原有物种的消失或其数量被削弱的现象，但主要建群种未变．
A stdudy was conducted to determine the seasonal changes of soil respiration and the contribution of root respiration to soil respiration in Betula plaophylla forest in Changbai Mountain from May to September in 2004. Results indicated that the total soil respiration, root-severed soil respiration and the root respiration followed a similar seasonal trend, with a high rate in summer due to wet and high temperature and a low rate in spring and autumn due to lower temperature. The mean rates of total soil respiration, root-severed soil respiration and root respiration were 4.44, 2.30 and 2.14 μmol.m^-2.s^-1, respectively during the growing season, and they were all exponentially correlated with temperature. Soil respiration rate had a linear correlation with soil volumetric moisture. The Q10 values for total soil respiration, root-severed soil respiration and root respiration were 2,82, 2.59 and 3. 16, respectively. The contribution rate of root respiration to the total soil respiration was between 29.3% and 58.7% during the growing season, indicating that root is a major component of soil respiration. The annual mean rates of total soil respiration, root-severed soil respiration and root respiration were 1.96, 1.08, and 0.87 μmol.m^-2.s^-1, or 741.73 408.71, and 329.24 g.m^-2.a^-1, respectively. Root respiration contributed 44.4% to the annual total soil respiration. The relationship proposed for soil respiration with soil lemperature was useful for understanding and predicting potential changes in Changbai Mountain B. platyphylla forest ecosystem in response to forest management and climate change.
