遮荫作为树冠对辐射截留的集中表现,与林下环境,特别是光环境特征具有密切关系。为满足坡地人工林下作物、中药栽培环境模拟、预测和控制的理论需要,以圆锥形树冠为研究对象,借助几何光学中光的直线传播原理,根据水平投影与坡面投影的亲似对应关系,在坡平面直角坐标系内讨论树冠的坡面投影形状、确定投影关键点坐标,在测树因子、经纬度、坡度、坡向、时间(包括时刻和日期)等变化要素基础上建立坡面投影理论边界模型Z(x′,y′)=0。经模拟验证,各时刻实测与计算阴影边界曲线相关系数大于等于0·928、显著水平(P)均达到0·01,表明该模型可较精确地描述正圆锥的坡面投影。在此基础上,进行模型的实用检验和分析,选择北半球中纬度单株樟子松,计算得到5月12日8:00~14:00树木遮荫影响最远到达东0·69倍树高、西1·18倍树高、南0·2倍树高、北0·4倍树高,绝大多数阴影位于近似扇环的区域内,计算结果符合北半球太阳视运动规律且实际观测结果与计算值之间相关系数为0·983(P=0·008),证明该模型适用于树冠的遮荫分析,并可能在邻体遮光干扰的进一步研究中发挥作用。最后讨论该模型的优点及局限性,明确模型在实际研究中合理运用的条件。 Shade, as a canopy, is a concentrated manifestation of radiation interception and closely related to the environment under the forest, especially the light environment. In order to meet the theoretical needs of simulation, prediction and control of crop cultivation environment under Chinese herb plantations in the sloping field, conical crown was taken as the research object. With the principle of linear propagation of light in geometrical optics and according to the pro-like correspondence between horizontal projection and slope projection , The projection shape of the crown of the canopy is discussed in the rectangular coordinate system of the slope plane. The coordinates of the key points of the projection are determined. On the basis of the factors of measuring the tree factors, latitude and longitude, gradient, aspect, time (including time and date) Theoretical boundary model Z (x ’, y’) = 0. The simulation results show that the correlation coefficient between measured and calculated shadow boundary curves at each time is greater than or equal to 0. 928, and the significant level (P) reaches 0.01. It shows that this model can describe the projection of the slope of a normal cone more accurately. On this basis, the practical test and analysis of the model were carried out to select the single-plantation Pinus sylvestris var. Mongolica in the mid-latitudes of the northern hemisphere. The tree shady effect on the 12th from the 8th to the 14th of May was calculated to reach the height of 0.69 times the east , 1.18 times the height of the west, 0.2 times the height of the south tree, 0.4 times the height of the north of the tree. Most of the shadows are located in the approximate fan-ring region. The calculated results are consistent with the northern hemisphere solar visual movement and the observed results are The correlation coefficient between the calculated values ​​is 0.983 (P = 0.008), which proves that this model is suitable for shading analysis of canopy and may play a role in the further study of the interference of neighboring light shading. Finally, the advantages and limitations of the model are discussed, and the conditions for the rational use of the model in practical research are clarified.