Abstract:

In this paper, the relationships between NP nutrition and the ratio of root to shoot(R/S) of seedlings of main afforestation tree species in south China, including Chinese Fir, Slash Pine and Timor Mahogany were studied in acid soil. The results showed that: With the increasing of the NP nutrition of soil,the accumulation of root dry matter of all experimented tree species decreased,and the photosynthetic products moved from root to the rest parts of seedling body. The responses of the dry weight of leaf and stem were different from each other.Of the Timor Mahogany leaf went down,and its stem’s rose up.On the contrary,the dry weight of the Slash Pine leat and stem increased.So,it is obvious that the more phosphorus in the soil,the lower the R/S.In other words, the increasing of R/S is an adaptability of seedling to the nutritional stress on acid soil.The relationships between the NP nutrition stress and R/S could be expressed as the following three models:Allometric model(r=as^k),Thornley's model and Function Equilibrium model.These models could give some important directions in seedling cultivation.According to Allometric model,a new nutrient diagnosis method could be got.The main point of the new method is that when the parameter k=1,which is the mark of the balance status of seedling,the biomass of seedling might reach the maximum.

Key words: acid soil, nutritional stress, Chinese Fir, Slash Pine, Timor Mahogany, root/shoot ratio, dry matter distribution