EQUATIONS TO ESTIMATE TREE GAPS IN A PRECISION FOREST MANAGEMENT AREA THE AMAZON BASED ON CROWN MORPHOMETRY

ABSTRACT The precision forest management technique still has much to be improved with the incorporation of forest biometric techniques and forest profiling with airborne LIDAR. When planning the cutting of a tree in forest management, the volume to be produced for industry is estimated but not the area impacted by removal of the tree. The objective of the present study was to develop equations for the Amazon rainforest that are able to estimate the impact area of gaps from harvesting individual dominant and co-dominant trees based on the canopy morphology obtained through forest profiling. On two separate occasions profiles were made in an annual forest-production unit in the Antimary State Forest (FEA) in the state of Acre, Brazil. The first was done a few days before the start of logging in 2010 and the second was done after completion of harvest activities in 2011. With field measurements and processing of the cloud of LIDAR points, dendrometric and morphometric variables were obtained for the canopy in order to develop equations for estimating gap areas. After evaluation of the explanatory variables with the highest correlation with gap area, the method used considered all possible models and included 2-4 parameters. The explanatory variables that best represent the impact of clearings are volume of the crown (VCop) and crown-projection area (APC). Ten equations were selected, of which two were chosen for use; these had R2 aj > 75% and Syx <23%. The good fit of the equations demonstrates the potential use of LIDAR to obtain information for estimating in advance the gaps in the forest cover that will be created from harvesting trees of different sizes.

摘要 精准林业管理技术在融合森林生物测定技术与机载激光雷达（airborne LIDAR）森林测绘方面仍存在较大提升空间。在林业生产的林木采伐规划环节，当前仅能估算工业生产所需的林木材积，却无法明确单株采伐作业所波及的影响区域范围。本研究旨在构建适用于亚马逊雨林的估算方程，基于通过森林测绘获取的冠层形态数据，估算优势木与亚优势木单株采伐后形成的林隙影响面积。研究于巴西阿克里州安蒂马利州立森林（Antimary State Forest, FEA）的年度林业生产单元内分两次开展冠层测绘工作：第一次于2010年采伐作业启动前数日完成，第二次则在2011年全部采伐活动结束后开展。通过野外实测与激光雷达点云数据处理，研究获取了冠层的测树学与形态学变量，以此构建林隙面积估算方程。在筛选出与林隙面积相关性最高的解释变量后，研究采用了涵盖2至4个参数的全模型构建方法。最能表征林隙影响范围的解释变量为冠体积（volume of the crown, VCop）与冠幅投影面积（crown-projection area, APC）。研究共筛选出10组方程，其中调整决定系数（R² aj）大于75%且标准估计误差（Syx）小于23%的2组方程被选定为实用模型。上述方程具备良好的拟合效果，证明机载激光雷达可用于获取相关信息，从而提前估算不同规格林木采伐后造成的林冠覆盖林隙面积。