{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,22]],"date-time":"2026-10-22T17:22:22Z","timestamp":1792689742845,"version":"4.5.0"},"reference-count":51,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2020,4,20]],"date-time":"2020-04-20T00:00:00Z","timestamp":1587340800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["1249946"],"award-info":[{"award-number":["1249946"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["80NSSC18K0642"],"award-info":[{"award-number":["80NSSC18K0642"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["80NSSC18K0621"],"award-info":[{"award-number":["80NSSC18K0621"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>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\u2014such as the recently launched NASA Global Ecosystem Dynamics Investigation (GEDI) spaceborne lidar\u2014can 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\u201312 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.<\/jats:p>","DOI":"10.3390\/rs12081304","type":"journal-article","created":{"date-parts":[[2020,4,21]],"date-time":"2020-04-21T04:49:38Z","timestamp":1587444578000},"page":"1304","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":41,"title":["Detecting Change in Forest Structure with Simulated GEDI Lidar Waveforms: A Case Study of the Hemlock Woolly Adelgid (HWA; Adelges tsugae) Infestation"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2585-6705","authenticated-orcid":false,"given":"Peter","family":"Boucher","sequence":"first","affiliation":[{"name":"School for the Environment, University of Massachusetts, Boston, MA 02125, USA"},{"name":"Department of Organismic and Evolutionary Biology (OEB), Harvard University, Cambridge, MA 02138, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Steven","family":"Hancock","sequence":"additional","affiliation":[{"name":"The University of Edinburgh, Edinburgh EH8 9XP, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7822-3560","authenticated-orcid":false,"given":"David","family":"Orwig","sequence":"additional","affiliation":[{"name":"Harvard Forest, Harvard University, Petersham, MA 01366, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laura","family":"Duncanson","sequence":"additional","affiliation":[{"name":"Department of Geographical Sciences, University of Maryland, College Park, MD 20740, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1232-3424","authenticated-orcid":false,"given":"John","family":"Armston","sequence":"additional","affiliation":[{"name":"Department of Geographical Sciences, University of Maryland, College Park, MD 20740, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hao","family":"Tang","sequence":"additional","affiliation":[{"name":"Department of Geographical Sciences, University of Maryland, College Park, MD 20740, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2683-5239","authenticated-orcid":false,"given":"Keith","family":"Krause","sequence":"additional","affiliation":[{"name":"Battelle, National Ecological Observatory Network (NEON), Boulder, CO 80301, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bruce","family":"Cook","sequence":"additional","affiliation":[{"name":"NASA Goddard Space Flight Center, Greenbelt, MA 20771, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ian","family":"Paynter","sequence":"additional","affiliation":[{"name":"Universities Space Research Association (USRA), Columbia, MD 21046, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6307-5200","authenticated-orcid":false,"given":"Zhan","family":"Li","sequence":"additional","affiliation":[{"name":"German Research Centre for Geosciences (GFZ), 14473 Potsdam, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4568-5758","authenticated-orcid":false,"given":"Arthur","family":"Elmes","sequence":"additional","affiliation":[{"name":"School for the Environment, University of Massachusetts, Boston, MA 02125, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Crystal","family":"Schaaf","sequence":"additional","affiliation":[{"name":"School for the Environment, University of Massachusetts, Boston, MA 02125, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,4,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/0378-1127(80)90013-4","article-title":"Forest Development in North America Following Major Disturbances","volume":"3","author":"Oliver","year":"1980","journal-title":"For. 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