Abstract:In order to understand the effects of wind stress on coastal shelterbelt tree species, leaf morphology, photosynthetic characteristics and branch tensile resistance to long-term wind stress were studied in six coastal shelterbelt tree species, including Ligustrum lucidum, Sapindus mukorossi, Machilus thunbergii, Koelreuteria bipinnata,Sapium sebiferum, and Quercus virginiana with ages of 8-10 years. The results showed that the leaf length and leaf area of L. lucidum, S. mukorossi,M. thunbergii, K. bipinnata and Q. virginiana significantly reduced under long-term wind stress, and also did the leaf width and leaf fractal index of K. bipinnata and L. lucidum. Meanwhile, the net photosynthetic rate of all six tree species had significant inhibition for 18%-47% under long-term wind stress, and the water use efficiency of S. mukorossi, K. bipinnata and Q. virginiana decreased, but that of L. lucidum, M. thunbergii and S. sebiferum had no significant effect. Under long-term wind stress, the maximum branch load and elastic modulus of S. mukorossi, M. thunbergii and K. bipinnata significantly increased, and the positive correlation with branch diameter were further enhanced. Therefore, long-term wind stress reduced the photosynthetic capacities of coastal shelterbelt species, but trees developed adaptive strategies, such as reducing leaf area, and tolerant strategies like enhancing branch resistance to reimburse this physiological deficit. Moreover, concerning the selection and collocation of tree species for the construction and restoration of coastal shelterbelts, priority can be given to L. lucidum, M. thunbergii and S. sebiferum in areas that have been continuously stressed by the strong wind.

Abstract:Branching pattern was studied in Osmanthus fragrans grown in Shifengzai scenery Fujian Province, China, by the Strahler method. The architectural parameters (overall bifurcation ratio, stepwise bifurcation ratio (SBR1:2 and SBR2:3), length of the first order branch, ratio of branch diameter (RBD2:1), branch angle and leaf angle) varied with the different growth and development stages. The architectural comparison of branches showed that height growth was obvious at the seedling stage, transition from height growth to crown expansion occurred at the sapling stage, and the crown size increased rapidly with slow height growth at the mature stage. The analysis of leaf distribution showed that the leaves are distributed mainly at the first-order branches and the third-order branches, and the leaf size increased with the growth and development of O. fragrans. It is suggested that the plasticity of branching pattern is an adaptive strategy of O. fragrans.