School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China.
Experimental Center of Desert Forestry, Chinese Academy of Forestry, Dengkou 015200, Inner Mongolia, China.
Ying Yong Sheng Tai Xue Bao. 2023 Jul;34(7):1892-1900. doi: 10.13287/j.1001-9332.202307.025.
Protective forests are the ecological barriers of oases in arid sand areas and can effectively prevent and control wind and sand hazards. The structural characteristics of individual trees, as the basic unit of protective forests, are the key factors affecting the protective benefits. With the typical leafless tree species of Ulan Buh Desert oasis, , var. , var. , and , as the research objects, and by using the ground-based LiDAR and through computational fluid dynamics (CFD), we fully explored the structural characteristics of individual trees and their surrounding aerodynamic characteristics on the basis of real 3D models. We further established the relationship between structural parameters of individual trees and wind field index. The results showed that combining AdQSM and MeshLab to build tree models had high accuracy. The wind field around the individual trees could be roughly divided into six regions, including the attenuation zone of the windward side of the plant, the acceleration zone at the top of the plant, the eddy zone, the calm zone, the transition zone, and the recovery zone of leeward side of the plant. The pressure field around individual trees showed a gradual change of high pressure on the windward side to low pressure on the leeward side. Horizontally, in the range of 20% to 50% reduction in relative wind speed, the effective protection distances were 0.21H-1.51H, 0.20H-0.91H, and 0.25H-1.64H (H was the corresponding tree height) for var. , var. , and , corresponding to effective protection areas of 18-294, 15-227, and 18-261 m, respectively. The maximum wind speed decay rate in the vertical direction was at 0.3H height for var. and , and was reflected at 0.5H height for var. . The correlation and stepwise regression analysis of the single tree structure parameters with the wind field indicators clearly indicated that optical porosity and volume porosity dominated the protection effect. Among the wind field factors, the best regression models related to the porous coefficient were screened for three factors, including diameter at breast height, tree surface area, and optical porosity. The regression variables screened for effective protection distance and effective protection area differed among the classes.
防护林是干旱风沙区绿洲的生态屏障，能有效防治风沙危害。树木个体的结构特征是防护林的基本单元，是影响防护效益的关键因素。以乌兰布和沙漠绿洲典型的无叶树种胡杨、灰杨、中间锦鸡儿、小叶锦鸡儿为研究对象，基于真实的 3D 模型，采用地面激光雷达和计算流体动力学（CFD），充分探究了树木个体的结构特征及其周围的空气动力学特性，并进一步建立了树木个体结构参数与风场指标的关系。结果表明，结合 AdQSM 和 MeshLab 构建树模型具有较高的精度。树木个体周围的风场可大致分为 6 个区域，包括植物迎风侧的衰减区、植物顶部的加速区、涡流区、静风区、过渡区和植物背风侧的恢复区。树木个体周围的压力场表现为迎风侧的高压逐渐变为背风侧的低压。水平方向上，在相对风速降低 20%~50%的范围内， var. 、 var. 、 的有效防护距离分别为 0.21H-1.51H、0.20H-0.91H 和 0.25H-1.64H（H 为相应的树高），对应的有效防护面积分别为 18-294、15-227 和 18-261 m。垂直方向上， var. 、 var. 的最大风速衰减率出现在 0.3H 高度处， var. 则出现在 0.5H 高度处。树木个体结构参数与风场指标的相关性和逐步回归分析表明，光学孔隙度和体积孔隙度主导着防护效果。在风场因子中，筛选出与多孔系数相关的最佳回归模型为三个因子，分别是胸径、树表面积和光学孔隙度。有效防护距离和有效防护面积的回归变量在不同类群中存在差异。
