Effects of light and ground cover on seed germination and seedling initial growth of Tetracentron sinense
By means of simulating wild natural environment, three kinds of light conditions with strong, middle and weak lights (being equivalent to 100%, 50% and 10% of natural light intensity, respectively) and three types of seedbeds with no cover, covering shrub-grass and covering shrub-grass and litter were set up.And effects of light and ground cover on seed germination rate, seedling survival rate and initial growth status of Tetracentron sinense Oliv.were investigated.The results show that under different light conditions, seed germination rate of T.sinense is the highest in no cover seedbed and the lowest in covering shrub-grass seedbed, in which, that is the highest in no cover seedbed under middle light condition.Survival rate of seedling with one month age in every treatment group is generally higher than that of seedling with two month age, and among different seedbeds, survival rate of seedling with one month age is the highest under weak light condition.In general, under weak light condition, covering shrub-grass seedbed is the most suitable for survive of T.sinense seedling with one month age.With decreasing of light intensity, height and main root length of seedling gradually decrease in no cover and covering shrub-grass seedbeds, while those appear the wavy trend in covering shrub-grass and litter seedbed, but there are no significant differences in height and main root length of seedling among different treatment groups.With changes of light intensity or seedbed cover degree, lateral root number, leaf area, dry weights of root, stem and leaf, and total dry weight of T.sinense seedling all appear different changing trends.Under strong light condition, root dry weight of seedling is the highest in covering shrub-grass seedbed;under middle light condition, lateral root number, leaf area, leaf dry weight and total dry weight of seedling are the highest in covering shrub-grass seedbed;and under middle light and weak light conditions, stem dry weight is the highest in no cover seedbed.Result of comprehensive analysis indicates that a certain degree of light is demanded for seed germination of T.sinense and litter and shrub-grass on ground would hinder its seed germination, while, at seedling establishment stage, the proper shading is demanded and cover shrub-grass on ground benefits seedling survive of T.sinense, therefore, forest gap or forest edge is more suitable for natural regeneration of T.sinense.Moreover, in situ conservation of T.sinense, different cultivation measures should be taken according to different stages of life history.