Study on Variation in Biomass and Annual Growth Rate of Different Organs of Oneyearold Toona sureni var. pubescens Seedlings

The relationship between the height, basal diameter and the time for the oneyearold seedlings of Toona sureni var. pubescens was studied, and the mathematical models to describe the correlations among the growth rate and biomass of each organ of the seedlings were formulated by means of periodic measurement of each index and with help of the ordered sample clustering and regressional analysis. The results showed that the annual growth of the oneyearold Toona sureni var. pubescens seedlings could be divided into four stages, i.e., the emergence stage, the initial growing stage, the flourishing growing stage and the late growing stage. The stem biomass in the initial growing stage was only 19.85% of the whole plant. The growth of the above ground part of the seedlings dominated at the flourishing growing stage, the biomass of the leaves and the stem respectively accounted for 4441% and 35.48% of the total. The growth rate of the stem volume in the flourishing growing stage reached the maximum level, growth of the height and basal diameter respectively accounted for 80.71% and 71.74% of the total growth of the plant at this stage. The growth of the stem and root system dominated at the late growing stage, the biomass of stem and root system accounted for 47.79% and 37.03% individually. The study showed that there were significant correlations among the height growth and the time, the basal diameter growth and the time, the height growth rate and the growth rate of each organ, the growth rate of the seedling height, basal diameter and the biomass allocation proportion of each organ respectively. The reliability of the mathematical models formulated according to the correlations was pretty high, which could be applied to estimate and analyze the growth rate and biomass allocation for oneyearold seedlings of Toona sureni var. pubescens at different growing stages around the year.