Abstract:

In this paper,a systematic study was made on the impact of cultivation activities,such as slash burning,site preparation,new planting tending,stand thinning and final logging etc.,on the long term site productivity of Chinese Fir plantations.Each of the above mentioned cultivation activities was considered upon the biomass and nutrient cycling of the plantation ecosystem as well as the reduction of soil organic matter and mineral nutrients in yellow red earth derived from granite and slate respectively.The results showed that,in the plantation ecosystem with yellow red earth derived from slate the reduction of soil organic matter and mineral nutrients was mainly caused by the slash burning and clear cutting activities,while in the plantation ecosystem with yellow red earth derived from granite the reduction of the soil organic matter and mineral nutrients was mainly caused by slash burning,soil erosion and clear cutting activities.For the Chinese Fir plantation with age of 19 years on the soil derived from slate,the total reduction of organic matter was 34.06t·hm^-2 and the total reduction of mineral nutrients was 2371.96kg·hm^-2,while in the Chinese Fir plantation with age of 27 years on the soil derived from granite,the total reduction of organic matter was 16.33t·hm^-2 and the total reduction of mineral nutrients was 2 323.24kg·hm^-2.It is concluded that the significant impact on soil nutrient loss existed when a series of cultivation activities were conducted following the normal cultural methods in the Chinese Fir plantation.It is impossible to maintain the site productivity without supplement of enough nutrients and organic matter to the soil in Chinese Fir plantations.

Key words: Chinese Fir plantation, Impact of cultivation activities, Biomass removal, Reduction of soil organic matter and mineral nutrients