Canopy LiDAR Measurements in Hemlock Removal Experiment at Harvard Forest 2005

As the ecological functioning of a forest stand is often related to the spatial organization of the canopy, we used a portable canopy LiDAR (PCL; Parker et al. 2004) to measure volumetric canopy structure in the simulated HWA management treatments. In September and October 2005, prior to leaf abscission, we set up 16 parallel transects spaced 2 meters apart in the 900 m2 (30 x 30 m) interior of each of the eight treatment plots. The orientation of the transects were either north-south or east-west to minimize the difficulty of traversing the stand. The distances to canopy surfaces more than1 m above the ground along the transects were recorded with the PCL. Assuming a constant horizontal sampling rate, the continual height measures were binned into 1 m intervals. From these measures, vertical canopy profiles, canopy openness, canopy rugosity, and other metrics related to the three-dimensional structure of the canopy can be derived. These canopy measures will be repeated minimally at 5 and 15 year intervals to develop an understanding of early structural dynamics and micrometeorological consequences associated with the simulated HWA treatments. (Parker, G.G., D.J. Harding, and M.L. Berger. 2004. A portable LIDAR system for rapid determination of forest canopy structure. Journal of Applied Ecology 41, 755-767).

鉴于林分的生态功能通常与林冠的空间组织形式紧密相关，我们采用便携式林冠激光雷达（portable canopy LiDAR，PCL；Parker等，2004）对模拟HWA管理处理样地的林冠体积结构开展测量。2005年9月至10月，即叶片脱落前，我们在8个处理样地各自的900 ㎡（30 m × 30 m）样地内部布设了16条间距为2 m的平行样线。样线朝向设置为南北向或东西向，以尽可能降低穿越林分的难度。沿样线，我们通过PCL记录了距地面1 m以上的林冠表面的距离数据。在假设水平采样率恒定的前提下，我们将连续获取的高度测量值划分为1 m间隔的区间。基于这些测量数据，可推导得到垂直林冠剖面、林冠开度、林冠粗糙度及其他与林冠三维结构相关的指标。我们将至少每5年和15年重复开展一次上述林冠测量工作，以明晰与模拟HWA处理相关的早期林分结构动态及微气象效应。(Parker, G.G., D.J. Harding, and M.L. Berger. 2004. 便携式激光雷达系统快速测定森林林冠结构. Journal of Applied Ecology 41, 755-767)