园林树木冠层疏透度测度及遮荫功能综合评价

Measurement of canopy transparency and comprehensive evaluation of shading function of garden trees

园林树木冠层疏透度对遮荫功能等生态效益的发挥有着重要影响。选取肇庆市10种常见行道树,采用数码相机拍摄冠层照片,结合Photoshop图像处理方法进行冠层疏透度测定,验证树木参数、冠层疏透度、遮荫面积与荫影照度的相关性,并采用主成分分析方法对遮荫功能进行综合评价。结果表明:(1)凤凰木(Delonix regia)、盆架木(Alstonia scholaris)、小叶榄仁(Terminalia neotaliala)、黄葛榕(Ficus virens)的疏透度最高;凤凰木、盆架木、小叶榄仁、芒果(Mangifera indica)的荫影照度最高。(2)冠层疏透度(CT)、枝下高(UBH)、树高(TH)、胸径(DBH)与荫影照度(SI)呈正相关;冠幅(CW)、冠高(CH)、胸径(DBH)、树高(TH)与遮荫面积(S)呈正相关;枝下高(UBH)、胸径(DBH)、树高(TH)与冠层疏透度(CT)呈正相关;荫影照度(SI)和冠高(CH)显著负相关,层疏透度与荫影照度显著正相关。冠幅是决定遮荫面积的主导因素,冠层疏透度和冠高是决定树木荫影照度的重要因素。(3)综合遮荫功能排序前3的树木分别为细叶榕(Ficus microcarpa)、黄葛榕和麻楝(Chukrasia tabularis)。冠层疏透度的测度为开展园林树木遮荫功能相关研究提供了全新思路。

Canopy transparency of garden trees has an important influence on the shading function and other ecological benefits.Ten common street trees in Zhaoqing City were selected,and the canopy photos were taken by digital camera.Canopy transparency was measured by Photoshop image processing method to verify the correlation between tree parameters,canopy transparency,shade area and shade illumination.The shading function was comprehensively evaluated by principal component analysis.The results showed that:(1)Delonix regia,Alstonia scholaris,Terminalia neotaliala and Ficus virens had the highest transparency,while Delonix regia,Alstonia scholaris,Terminalia neotaliala and Mangifera indica had the highest shading illumination.(2)Canopy transparency(CT),height under branches(UBH),tree height(TH),and diameter at breast height(DBH)were positively correlated with the shading illumination(SI).Canopy width(CW),canopy height(CH),DBH,TH were positively correlated with shade area(S).UBH,DBH,TH were positively correlated with CT.SI was significantly negatively correlated with CH,and layer transparency was significantly positively correlated with SI.Canopy width was the dominant factor to determine the shade area,and canopy transparency and canopy height were important factors to determine the shading illumination of trees.(3)The top three trees with the comprehensive shading function were Ficus microcarpa,Ficus virens and Chukrasia tabularis.The measurement of canopy transparency provides a new idea for the study of shading function of garden trees.