Influence of thinning on acidic deposition in Chinese fir plantations

LIU Si-mian(柳思勉)^{1, 2}, TIAN Da-lun(田大伦)^{3, 4}, XIANG Wen-hua(项文化)^{3, 4}, YAN Wen-de(闫文德)⁴, LIU Yun-guo(刘云国)^{1, 2}, HU Xin-jiang(胡新将)^{1, 2}

(1. College of Environmental Science and Engineering, Hunan University, Changsha 410082, China;
2. Key Laboratory of Environmental Biology and Pollution Control of Ministry of Education
(Hunan University), Changsha 410082, China;
3. Faculty of Life Science and Technology, Central South University of Forestry and Technology,
Changsha 410004, China;
4. Section of Ecology Research, Central South University of Forestry and Technology, Changsha 410004, China)

Abstract:Acidic deposition, which is mainly caused by atmospheric pollution, is one of the global environmental problems. Thinning is an effective management to improve the tree productivity, reduce the wildfire risk and maintain a healthy forest. Since thinning may reduce the effect of acidic deposition, the effect of thinning on acidic deposition was estimated. The biomass, soil properties, pH value of runoff and groundwater in both unthinned and thinned Chinese fir plantations were measured and compared over a 5-year period (2-6 years after thinning). The results indicated that acidic deposition in the Huitong State Ecosystem Research Station was serious, and it got worse with time. Forest thinning resulted in a huge change in biomass and soil properties. During the 5-year monitoring period, biomasses of understory and litter, plant species richness, coverage of undergrowth plant layer were significantly higher in thinned site than in unthinned site. Moreover, higher soil fertility as well as lower amounts of runoff and groundwater were found in thinned site. It was suggested that thinning could improve the structure of forest, leading to restoring the effluent (runoff and groundwater) pH to the normal value.

Key words:thinning; acidic deposition; Chinese fir; biomass; soil properties