VARIABILITY AND BALANCE OF CROWN PROJECTION OF TREES PLANTED ON SIDEWALKS OF THREE BRAZILIAN CITIES

ABSTRACT Tree crown form can be used as a variable to the comprehension of factors that influence tree growth, mainly maintenance practices and interactions with urban structures, but also the potential risks that can exist. In this research, we aimed to evaluate crown projection unbalance of trees planted on sidewalks of three Brazilian cities, in order to determine the existence and the sort of asymmetry and crown angle formed in relation to the central axis of the trunk. We measured the length of four crown projection radii and compared them by means of Kruskal-Wallis Test. Each one of the crowns was framed in one of the four asymmetry classes to verify the uniformity of projection in relation to the central axis of the trunk. We also determined the distance between central axis of the trunk and crown centroid, with respective angle formed, in order to characterize the unbalance of crown projection. There was a significant difference among crown projection radii, with greater values to radius faced to street and the smallest ones faced to buildings. In the three cities evaluated there were a predominance of trees framed on class 3 of asymmetry, which represents the model with the greatest deformations on crown of trees. We observed the lowest mean angle of crown centroid projection with distinctions among species sampled in Bonito.

摘要：树冠形态可作为解析树木生长影响因素的变量，此类因素主要包括养护措施、与城市构筑物的相互作用，同时亦涵盖潜在的风险隐患。本研究旨在评估巴西三座城市人行道栽植树木的树冠投影失衡状况，以明确相对于树干中轴线的不对称类型及形成的树冠角度。研究测量了4组树冠投影半径，并通过克鲁斯卡尔-沃利斯检验（Kruskal-Wallis Test）对其开展比较分析。将每株树木的树冠划归于4种不对称等级之一，用以验证其相对于树干中轴线的投影均匀性。此外，本研究还测定了树干中轴线与树冠质心之间的距离及对应夹角，以此表征树冠投影的失衡程度。结果显示，不同树冠投影半径间存在显著差异：朝向街道的半径数值更大，而朝向建筑物的半径数值最小。在三座评估城市中，绝大多数树木被归入不对称等级3，该等级代表树冠变形程度最高的树木类型。我们观察到，博尼图市采样的不同树种间，树冠质心投影的平均角度存在显著差异，且该平均角度为所有组别中最低。