Research And Evaluation On Wind-resistance Of Main Tree Species In Leizhou Peninsula

Typhoon is a kind of natural disaster which has the characteristics of high frequency, affecting wide area, causing serious loss,and so on. Leizhou Peninsula is located in the south most of China mainland, and there will be an average of 2 to 3 typhoons annually, where typhoon takes palce frequently. Since 1890, China began to introduce Eucalypt,and the real conduct of large-scale introduction of system testing and promotion of cultivation began in 1950 of Leizhou Peninsula. Eucalypt has also become one of fast growing forest tree species with regional development strategy, so study on the wind-resistance of Eucalypt in this region is particularly important. Because of their rapid growth, strong resistance, Casuarina and Acacia become to the main protection forest tree species of southern coastal and important species of pulp and plate wood. However, different species of Eucalyptus, Casuarina equisetifolia and Acacia confusa have differenct wind-resistance, some are strong, while others are easier to wind-full or wind-breakage. Wind-resistance of green tree species in Leizhou Peninsula is one of the key factors of their suitability for cultivation in this region. For this reason, studies on wind-resistance of main green tree species in Leizhou Peninsula,analysising the correlation between wind-resistance and tree factors, and evaluating good wind-resistance varieties or clones are important measures to solve the wind serious problems typhoons brought in southern area.Through the research and analysis of three major fast-growing species of this region(Eucalyptus, Casuarina equisetifolia and Acacia confusa) on growth (including height, diameter, bark thickness), shape indices (including the crown, stem form straightness, branch angle ,root conditions , canopy density,etc.) and wood characteristics (including wood basic density, dynamic elastic modulus, the growth strain and fiber morphology), and lots of literature search of green tree species to analyse the different wind-resistance. The main results are summarized as follows,1.Growth,roots and wind damage of two one-year-old Eucalyptus clones (Eucalyptus grandis×E. tereticornis clone DH201-2 and E. urophylla×E. grandis clone DH32-29) were studied in six stand densities(1250, 1667, 2500, 5000, 6667 and 10000 trees?hm-2), and correlation between stand density,growth, roots and wind resistance was carried out. The results showed that the wind-resistance of two clones were significantly different, the wind-resistance of clone DH201-2 was stronger than that of DH32-29 in the same density, because the number of roots of DH201-2 was more than that of DH32-29 however the crown of DH32-29 was larger than that of DH201-2;and there was some correlation between wind damage and factors,for example,the bigger the crown or the shorter the height was,the easier wind-full the trees were(P<0.01);the smaller the crown was, the more likely wind-breakage the trees were(P<0.01);the more number of roots, the stronger the wind-resistance(P<0.05);the strongest wind-resistance and biggest growth of DH201-2 were respectively in stand density of 2500 trees·hm-2 and 1667 trees·hm-2,so if the stand density was too dense or too sparse,growth and wind-resistance would not be optimal.2.Trees from plots(22) of two clones of 4 and 6-8 years old Casuarina and from two species of 8 year old Acacia stands, were measured for growth and wind-resistance traits such as wood basic density and pilodyn penetration in a site at Nansan coastal protection forest in Zhanjiang,the results show that : There were some significant differences in all traits among forest ages(P<0.01); In terms of the regression, the worst plot was Acacia mangium(the grade of wind damage was 5.94),the second one was Acacia confuse(the grade of wind damage was 4.90),the best were two Casuarina clones, whereas stands of them had not significant differences. For categorical traits, wood basic density, growth strain value, acoustic velocity and Pilodyn penetration value were major(the standardized correlation coefficient valueβwere -1.244,1.039,0.449 respectively)but branch angle ,height and crown width were minor to determine the meaning of wind damage grade(the standardized correlation coefficient valueβwere -0.014,-0.069,0.097 respectively ). Fabre width and fabre length had positive effects, for instance, an increase in fabre width resulted in an increase in predicted wind damage grade,but the fabre length resulted in contrary effects.3. Through lots of literature search and data suvery,selected familiar 82 landscape tree species in Leizhou Peninsula, made a judge matrix by AHP, using 9 factors including tree type, tree height, diameter, crown, crown shape, stem form straightness, air-dry density, leaf tier status,situation of branches and roots;and got the weight of every factor by calculating the eigenvectors corresponding to the maximum characteristic root of matrix.Moreover,evaluated the wind-resistance of 82 tree species by comprehensive assessment method ,got the similar results of the choices of main green tree species in leizhou Peninsula and provided a scientific basis for the choice of green tree species in south coast.