Index Of Soil Fertility And Evaluation Of Chinese Fir Plantation

Chinese fir [Cunninghamia lanceolata (Lamb) Hook] is a most important timber tree in southern China.In the last years,because of the traditional extensive management and some inappropriate cultivated measures,such as monoculture of a tree species,control burning,over-all site preparation,clear cutting and continuous cropping at the same site, as well as the biological characteristics of Chinese fir itself,the decline of its forest productivity and soil fertility exists in common.It is a critical problem nowadays to reveal the mechanism of productivity decline of Chinese fir plantations after continuous cropping and to explore techniques for long-term maintenance of the forest productivity.The project was studied on different generations and different ages of Chinese fir plantation in Jingdezhen city , JiangXi province. The soil enzyme, soil chemical and physical properties of Chinese fir plantation were measured. And the soil fertility indexes of Chinese fir plantation were analyzed .At last, we gave a evaluation about soil fertility quality of Chinese fir plantation.The main results were showed as follows:(1)With the growth of Chinese fir plantation , soil bulk density,soil water content tended to increase, and soil porosity tended to decline. For example, the soil bulk density of 8,11,15-year-old Chinese fir plantation were increased by 6.5% and 8.45%, respectively. The soil water content of 8,11,15-year-old Chinese fir plantation were increased 2.05% and 3.3%, respectively. And the soil porosity of 8,11,15-year-old Chinese fir plantation are decreased by 2.4% and 3.5%, respectively. Compared with the first planting, the soil bulk density of second planting was increased, and the soil porosity of second planting was decreased.(2)With the growth of Chinese fir plantation, there are evident drops on N,P,K,soil organic matter and CEC . pH values of different soil layers and different generations were all significantly different. Soil organic matter of different generations were significantly different, but that in different soil layers were significantly different . CEC of different soil layers and different generations are all significantly different. As the Chinese fir grows, the pH values,soil organic matter and CEC were decreased. So, older Chinese fir had more intensive impact on soil chemical properties than the younger.(3)With the soil layers increasing, soil enzyme activities are decreased. And the activity of highest soil enzyme was in the 0-10cm soil layer, the lowest activity soil enzyme was in the 20-40cm soil layer. At the same soil layer, with the grows of Chinese fir, the soil enzyme activities were decreased. So the activity of soil enzyme of 8 years was higher than that of 15 years. Soil enzyme activities in the first planting was higher than that in the second planting.(4)Composite index of soil quality was assessed by two methods: soil integrated quality index (QI) and soil deterioration index (DI). It showed: 8-year-old Chinese fir plantation>11-year-old Chinese fir plantation>15-year-old Chinese fir plantation>the second planting. So, with growth of Chinese fir, soil quality declined. Compared with the first planting, soil fertility quality index of the second planting was reduced.