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冠层的空间排布息息相关，我们采用便携式冠层激光雷达（Portable Canopy LiDAR，PCL；Parker等，2004）对模拟HWA管理措施下的冠层体积结构进行测量。2005年9月至10月，即叶片脱落前，我们在8个处理样地各900平方米（30×30米）的内部区域设置了16条间距为2米的平行样带。为最大程度降低穿行林分的难度，样带朝向统一设置为南北向或东西向。借助该便携式冠层激光雷达，我们记录了样带上距地面1米以上的冠层表面距离数据。在假设水平采样速率恒定的前提下，我们将连续获取的高度测量值按1米间隔进行分箱处理。基于上述测量数据，可推导出垂直冠层剖面（vertical canopy profiles）、冠层开度（canopy openness）、冠层粗糙度（canopy rugosity）以及其他与冠层三维结构相关的量化指标。我们计划至少每5年和15年重复开展一次冠层测量，以明晰模拟HWA管理措施所引发的早期结构动态变化及微气象学效应。(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.)