Abstract:

The growing rate curve of young forest has one valley and two peaks and the boundary (the valley point)is in the first and second decade of July.The increments in early stage and on sunny slope are greater than that in the later stage and shady slope respectively.The young trees are more sensitive to water condition than thermal one. The reaction process needs about 10 days.The combined effect of water and heat on the growth is very strong.High temperature can limit the tree growth.The difference of growth between different or ientations of slope is due to different water and thermal conditions.The tree growth on the shady slope is better than that on the sunny slope in weibei loess plateau.

Key words: Platycladus orientalis, Young forests, Growth dynamics, Water, Heat, Regression analysis