Detecting Change in Forest Structure with Simulated GEDI Lidar Waveforms: A Case Study of the Hemlock Woolly Adelgid (HWA; Adelges tsugae) Infestation
Detecting Change in Forest Structure with Simulated GEDI Lidar Waveforms: A Case Study of the Hemlock Woolly Adelgid (HWA; Adelges tsugae) Infestation
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DOI：
10.3390/rs12081304
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发表时间：
2020-04-01
期刊：
影响因子：
5
通讯作者：
Schaaf, Crystal
中科院分区：
文献类型：
--
作者：
Boucher, Peter Brehm;Hancock, Steven;Schaaf, Crystal
铁杉绵球蚜（HWA; Adelges tsugae）是一种入侵性昆虫，正在蔓延到美国东北部的森林中，这是由与气候变化相关的冬季气温升高所造成的。这种干扰的初始阶段是难以检测与被动光学遥感，因为昆虫往往会导致其宿主物种，东部铁杉树（铁杉加拿大），落叶在林中和林下，然后才显示在上层的影响。新的主动遥感技术，如最近推出的美国宇航局全球生态系统动力学调查（GEDI）星载激光雷达，可以通过穿透冠层间隙和记录低冠层结构的变化来解决这一限制。这项研究探讨了新的机会，监测HWA侵扰与机载激光雷达扫描（ALS）和GEDI星载激光雷达数据。GEDI波形模拟使用机载激光雷达数据集从HWA出没的森林地块在哈佛Forest ForestGEO网站在马萨诸塞州中部。2012年和2016年，NASA的G-LiHT和氖AOP两台机载激光雷达仪器飞越了该地点。从每个机载激光雷达数据集模拟GEDI波形，并将2012年至2016年波形指标的变化与ForestGEO站点的现场铁杉死亡率进行比较。铁杉地块被证明是经历动态变化的结果，HWA侵扰，失去了大量的植物面积在中间的树冠，而仍然在上层树冠生长。在一个逻辑回归模型中，林中植物面积（派11-12 m）和总冠层渗透性（由RH 10表示）的变化占铁杉死亡率变化的60%。这些结构-条件关系的鲁棒性保持，即使当模拟波形被视为真实的GEDI数据与添加的噪声和稀疏的空间覆盖。这些结果表明，未来的干扰监测研究与ALS和GEDI激光雷达数据的承诺。
The hemlock woolly adelgid (HWA; Adelges tsugae) is an invasive insect infestation that is spreading into the forests of the northeastern United States, driven by the warmer winter temperatures associated with climate change. The initial stages of this disturbance are difficult to detect with passive optical remote sensing, since the insect often causes its host species, eastern hemlock trees (Tsuga canadensis), to defoliate in the midstory and understory before showing impacts in the overstory. New active remote sensing technologies-such as the recently launched NASA Global Ecosystem Dynamics Investigation (GEDI) spaceborne lidar-can address this limitation by penetrating canopy gaps and recording lower canopy structural changes. This study explores new opportunities for monitoring the HWA infestation with airborne lidar scanning (ALS) and GEDI spaceborne lidar data. GEDI waveforms were simulated using airborne lidar datasets from an HWA-infested forest plot at the Harvard Forest ForestGEO site in central Massachusetts. Two airborne lidar instruments, the NASA G-LiHT and the NEON AOP, overflew the site in 2012 and 2016. GEDI waveforms were simulated from each airborne lidar dataset, and the change in waveform metrics from 2012 to 2016 was compared to field-derived hemlock mortality at the ForestGEO site. Hemlock plots were shown to be undergoing dynamic changes as a result of the HWA infestation, losing substantial plant area in the middle canopy, while still growing in the upper canopy. Changes in midstory plant area (PAI 11-12 m above ground) and overall canopy permeability (indicated by RH10) accounted for 60% of the variation in hemlock mortality in a logistic regression model. The robustness of these structure-condition relationships held even when simulated waveforms were treated as real GEDI data with added noise and sparse spatial coverage. These results show promise for future disturbance monitoring studies with ALS and GEDI lidar data.