| Forest ecosystem is the largest terrestrial carbon storage. Soil is the largest carbon pool in the terrestrial ecosystem and it is an important greenhouse gas source and sink. Forest soil respiration is an important way of the global carbon cycle, as its dynamic change will directly affect the global C balance. Therefore, intensively analyzing the control factors of soil respiration and their response to management measure is of great importance. Forest thinning is an important management measure to cultivate the forest and it has a non-negligible impact on soil respiration. With our study, the seasonal variation of soil respiration among four thinning treatments. and the correlative factors that may lead to change of soil respiration were investgated in a25-year-old Chinese fir plantations in Nanjing Lishui Forest Farm.The general results were as follows:(1)medium intensity thinning(MIT) markedly decreased total soil respiration and its components respiration, heavy intensity thinning (HIT) markedly increased the total soil respiration (P<0.05). The autotrophic respiration was reduced by thinning especially MIT. Soil heterotrophic components accounted for the largest proportion of soil respiration, heterotrophic respiration show a downward trend with increasing thinning intensity. HIT and light intensity thinning (LIT) increased CO2emission of the litter, but MIT reduced CO2emission of the litter. The impact of HIT on litter CO2emission reached a significant level (P<0.05).(2) The soil temperature and soil surface moisture content were improved with thinning, the mean soil temperature [5.30～26.47℃] and the mean moisture content (23.26%) of LIT are the highest. By the increases of thinning intensity, soil organic matter content was significantly reduced, the total biomass of understory vegetation increased (P<0.05).(3)The pertinence between total soil respiration and soil temperature is extremely significant (P<0.01), but the correlation of soil respiration with the soil surface moisture content, soil organic matter content and understory vegetation biomass was not significant (p>0.05). |
