A Comparasion of the Productivity and Nutrient Cycling of Chinese Fir Plantationin Different Site Conditions

The productivity and nutrient cycling of 19-year-old Chinese fir plantations in different site conditions were studied in a small watershed located in Fenyi County,Jiangxi Province.The watershed was divided into three parts: rideg,slope and foot of a hill,for which soil physical and chemical properties were completely different.Significant differences in productivity and nutrient cycling were found under these site conditions.Main conclusion is as follows;1.The tree biomass in ridge,slope and foot,was 68.3374 t/ha,99.162 t/ha,141.1403 t/ha,respectively.The tree biomass at the ridge was 48.4% of that at the foot,and the average individual biomass of the ridge was only 14.95% of that at the foot.That means the ridge is not suitable for the growth of Chinese fir.2.The effect of site condition on growth begins from infant stage(1-4) and arrives the biggest in fast growing stage (5~12),then gradually declines.3.The amount and rate of element accumulation,return,absorption and cycling follow the order: ridge'sslope' sfoot's.And on any site conditions the cycling rate of N was always the highest and Mg the lowest.