{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,20]],"date-time":"2026-01-20T01:21:02Z","timestamp":1768872062788,"version":"3.49.0"},"reference-count":35,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2022,3,10]],"date-time":"2022-03-10T00:00:00Z","timestamp":1646870400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Consumer-grade drone-produced digital orthoimagery is a valuable tool for conservation management and enables the low-cost monitoring of remote ecosystems. This study demonstrates the applicability of RGB orthoimagery for the assessment of forest health at the scale of individual trees in a 46-hectare plot of rare southern Appalachian red spruce forest on Whitetop Mountain, Virginia. We used photogrammetric Structure from Motion software Pix4Dmapper with drone-collected imagery to generate a mosaic for point cloud reconstruction and orthoimagery of the plot. Using 3-band RBG digital orthoimagery, we visually classified 9402 red spruce individuals, finding 8700 healthy (92.5%), 251 declining\/dying (2.6%), and 451 dead (4.8%). We mapped individual spruce trees in each class and produced kernel density maps of health classes (live, dead, and dying). Our approach provided a nearly gap-free assessment of the red spruce canopy in our study site, versus a much more time-intensive field survey. Our maps provided useful information on stand mortality patterns and canopy gaps that could be used by managers to identify optimal locations for selective thinning to facilitate understory sapling regeneration. This approach, dependent mainly on an off-the-shelf drone system and visual interpretation of orthoimagery, could be applied by land managers to measure forest health in other spruce, or possibly spruce-fir, communities in the Appalachians. Our study highlights the usefulness of drone-produced orthoimagery for conservation monitoring, presenting a valid and accessible protocol for the monitoring and assessment of forest health in remote spruce, and possibly other conifer, populations. Adoption of drone-based monitoring may be especially useful in light of climate change and the possible displacement of southern Appalachian red spruce (and spruce-fir) ecosystems by the upslope migration of deciduous trees.<\/jats:p>","DOI":"10.3390\/rs14061341","type":"journal-article","created":{"date-parts":[[2022,3,10]],"date-time":"2022-03-10T20:19:10Z","timestamp":1646943550000},"page":"1341","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Assessment of Canopy Health with Drone-Based Orthoimagery in a Southern Appalachian Red Spruce Forest"],"prefix":"10.3390","volume":"14","author":[{"given":"Ryley C.","family":"Harris","sequence":"first","affiliation":[{"name":"Department of Geography, Virginia Tech, Blacksburg, VA 24061, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4076-1184","authenticated-orcid":false,"given":"Lisa M.","family":"Kennedy","sequence":"additional","affiliation":[{"name":"Department of Geography, Virginia Tech, Blacksburg, VA 24061, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5911-2803","authenticated-orcid":false,"given":"Thomas J.","family":"Pingel","sequence":"additional","affiliation":[{"name":"Department of Geography, Virginia Tech, Blacksburg, VA 24061, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2189-6013","authenticated-orcid":false,"given":"Valerie A.","family":"Thomas","sequence":"additional","affiliation":[{"name":"Department of Forest Resources and Environmental Conservation, Virginia Tech, Blacksburg, VA 24061, USA"}]}],"member":"1968","published-online":{"date-parts":[[2022,3,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"427","DOI":"10.2307\/1942471","article-title":"Late Quaternary Vegetation of Central Appalachia and the New Jersey Coastal Plain","volume":"49","author":"Watts","year":"1979","journal-title":"Ecol. Monogr."},{"key":"ref_2","unstructured":"White, P.S. (1984). Late-Quaternary history of the spruce-fir ecosystems in the southern Appalachian mountain region. The Southern Appalachian Spruce-Fir Ecosystem: Its Biology and Threats, United States Department of the Interior, National Park Service. Research\/Resource Management Report SER-71."},{"key":"ref_3","unstructured":"Adams, H.S., Stephenson, S.L., Rollins, A.W., and Adams, M.B. (2009, January 14\u201315). The isolated red spruce communities of Virginia and West Virginia. Proceedings of the Conference of Ecological High-Elevation Forests in the Central and Southern Appalachian Mountains, Slatyfork, WV, USA. GTR- NRS-P-64."},{"key":"ref_4","first-page":"4","article-title":"Land Use History of Three Spruce-Fir Forest Sites in Southern Appalachia","volume":"32","author":"Pyle","year":"1988","journal-title":"For. Conserv. Hist."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Rives, W.C. (1889). Notes on the Birds of White Top Mountain, Virginia. Auk, 50\u201353.","DOI":"10.2307\/4067437"},{"key":"ref_6","unstructured":"Pashley, D.N., Beardmore, C.J., Fitzgerald, J.A., Ford, R.P., Hunter, W.C., Morrison, M.S., and Rosenberg, K.V. (2000). Partners in Flight: Conservation of the Land Birds of the United States, American Bird Conservancy."},{"key":"ref_7","unstructured":"Rich, T.D., Beardmore, C.J., Berlanga, H., Blancher, P.J., Bradstreet, M.S.W., Butcher, G.S., Demarest, D.W., Dunn, E.H., Hunter, W.C., and Inigo-Elias, E.E. (2004). Partners in Flight North American Landbird Conservation Plan, Cornell Lab of Ornithology."},{"key":"ref_8","unstructured":"Noss, R.F., and Peters, R.L. (1995). Endangered Ecosystems: A Status Report on America\u2019s Vanishing Habitat and Wildlife, Defenders of Wildlife."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1016\/0378-1127(92)90485-R","article-title":"Impacts of acidic deposition on high-elevation spruce-fir forests: Results from the SpruceFir Research Cooperative","volume":"51","author":"Adams","year":"1992","journal-title":"Ecol. Manag."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1016\/0378-1127(94)90125-2","article-title":"Mortality trends in a southern Appalachian red spruce population","volume":"64","author":"Busing","year":"1994","journal-title":"For. Ecol. Manag."},{"key":"ref_11","unstructured":"Johnson, A., Cook, E., Eagar, C., Cogbill, C., and Jensen, K. (2012). Ecology and Decline of Red Spruce in the Eastern United States, Springer."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2190","DOI":"10.1111\/eva.12985","article-title":"Whole-exome sequencing reveals a long-term decline in effective population size of red spruce (Picea rubens)","volume":"13","author":"Capblancq","year":"2020","journal-title":"Evol. Appl."},{"key":"ref_13","first-page":"427","article-title":"Mapping microhabitat structure and connectivity on a tropical inselberg using UAV remote sensing","volume":"45","author":"Realpe","year":"2020","journal-title":"Prog. Phys. Geogr. Earth Environ."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Fabbri, S., Grottoli, E., Armaroli, C., and Ciavola, P. (2021). Using High-Spatial Resolution UAV-Derived Data to Evaluate Vegetation and Geomorphological Changes on a Dune Field Involved in a Restoration Endeavour. Remote Sens., 13.","DOI":"10.3390\/rs13101987"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"294","DOI":"10.1080\/23754931.2021.1871937","article-title":"Deriving Land and Water Surface Elevations in the Northeastern Yuca-t\u00e1n Peninsula Using PPK GPS and UAV-Based Structure from Motion","volume":"7","author":"Pingel","year":"2021","journal-title":"Pap. Appl. Geogr."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Prior, E., Aquilina, C., Czuba, J., Pingel, T., and Hession, W. (2021). Estimating Floodplain Vegetative Roughness Using Drone-Based Laser Scanning and Structure from Motion Photogrammetry. Remote Sens., 13.","DOI":"10.3390\/rs13132616"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"127546","DOI":"10.1016\/j.jclepro.2021.127546","article-title":"Unmanned aerial vehicle and artificial intelligence revolutionizing efficient and precision sustainable forest management","volume":"311","author":"Liu","year":"2021","journal-title":"J. Clean. Prod."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Wang, C., Morgan, G., and Hodgson, M. (2021). sUAS for 3D Tree Surveying: Comparative Experiments on a Closed-Canopy Earthen Dam. Forests, 12.","DOI":"10.3390\/f12060659"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Fraser, B., and Congalton, R. (2021). Estimating Primary Forest Attributes and Rare Community Characteristics Using Unmanned Aerial Systems (UAS): An Enrichment of Conventional Forest Inventories. Remote Sens., 13.","DOI":"10.3390\/rs13152971"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Alonzo, M., Andersen, H.E., Morton, D.C., and Cook, B.D. (2018). Quantifying boreal forest structure and composition using UAV structure from motion. Forests, 9.","DOI":"10.3390\/f9030119"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"10","DOI":"10.1186\/s41610-017-0029-0","article-title":"Calculating coniferous tree coverage using unmanned aerial vehicle photogrammetry","volume":"41","author":"Ivosevic","year":"2017","journal-title":"J. Ecol. Environ."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Safonova, A., Hamad, Y., Dmitriev, E., Georgiev, G., Trenkin, V., Georgieva, M., Dimitrov, S., and Iliev, M. (2021). Individual Tree Crown Delineation for the Species Classification and Assessment of Vital Status of Forest Stands from UAV Images. Drones, 5.","DOI":"10.3390\/drones5030077"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"573","DOI":"10.1007\/s11056-019-09754-5","article-title":"Monitoring forest structure to guide adaptive management of forest restoration: A review of remote sensing approaches","volume":"51","author":"Camarretta","year":"2019","journal-title":"New For."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Kom\u00e1rek, J., Kl\u00e1p\u0161t\u011b, P., Hrach, K., and Klou\u010dek, T. (2022, January 21). The Potential of Widespread Ready-Made UAVs in Quantifying Conifers and Delineating Their Crowns. Available online: https:\/\/www.researchsquare.com\/article\/rs-723971\/v1.","DOI":"10.21203\/rs.3.rs-723971\/v1"},{"key":"ref_25","first-page":"26","article-title":"The volcanogenic Mount Rogers Formation and the overlying glaciogenic Konnarock For-mation\u2014Two Late Proterozoic units in southwestern Virginia","volume":"2029","author":"Rankin","year":"1993","journal-title":"US Geol. Surv. Bull."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"489","DOI":"10.2307\/2995900","article-title":"Comparative study of composition and distribution patterns of subalpine forests in the Bal-sam Mountains of southwest Virginia and the Great Smoky Mountains","volume":"111","author":"Rheinhardt","year":"1984","journal-title":"Bull. Torrey Bot. Club"},{"key":"ref_27","unstructured":"Potter, K.M., Frampton, J., Sidebottom, J., Onken, B., and Reardon, R. (2005, January 1\u20133). Impacts of balsam woolly adelgid on the southern Appalachian spruce-fir ecosystem and the North Carolina Christmas tree industry. Proceedings of the Third Symposium on Hemlock Woolly Adelgid in the Eastern United States, Asheville, NC, USA."},{"key":"ref_28","unstructured":"Krustchinsky, A.R. (2010). Post-Fire Recovery and Successional Dynamics of an Old-Growth Red Spruce Forest in the Southern Appalachian Mountains. [Master\u2019s Thesis, Texas A & M University]."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"176","DOI":"10.3368\/lj.20.2.176","article-title":"Which Nature? A Case Study of Whitetop Mountain","volume":"20","author":"Robertson","year":"2001","journal-title":"Landsc. J."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Cartwright, J.M., and Wolfe, W.J. (2016). Insular Ecosystems of the Southeastern United States\u2014A Regional Synthesis to Support Biodiversity Conservation in a Changing Climate, US Department of the Interior-Southeast Climate Science Center, US Geological Survey.","DOI":"10.3133\/pp1828"},{"key":"ref_31","unstructured":"Mielke, M.E. (1986). Decline and Mortality of Red Spruce in West Virginia. Report 86 4, Department of Agriculture, Forest Service, Forest Pest Management. Methods Application Group."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"905","DOI":"10.1139\/x92-120","article-title":"Prevalence of individual-tree growth decline in red spruce populations of the southern Appalachian Mountains","volume":"22","author":"Leblanc","year":"1992","journal-title":"Can. J. For. Res."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"760","DOI":"10.1890\/1051-0761(2000)010[0760:GDFFDA]2.0.CO;2","article-title":"Gap dynamics following forest decline: A case study of red spruce forests","volume":"10","author":"Battles","year":"2000","journal-title":"Ecol. Appl."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"29","DOI":"10.3375\/043.036.0108","article-title":"Release of Suppressed Red Spruce Using Canopy Gap Creation\u2014Ecological Restoration in the Central Appalachians","volume":"36","author":"Rentch","year":"2016","journal-title":"Nat. Areas J."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"118789","DOI":"10.1016\/j.foreco.2020.118789","article-title":"Spatial and temporal fuels changes in white-bark pine (Pinus albicaulis) from mountain pine beetle (Dendroctonus ponderosae)","volume":"482","author":"Gray","year":"2021","journal-title":"For. Ecol. Manag."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/6\/1341\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:34:06Z","timestamp":1760135646000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/6\/1341"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,3,10]]},"references-count":35,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2022,3]]}},"alternative-id":["rs14061341"],"URL":"https:\/\/doi.org\/10.3390\/rs14061341","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,3,10]]}}}