{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,17]],"date-time":"2026-03-17T11:56:40Z","timestamp":1773748600022,"version":"3.50.1"},"reference-count":92,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2021,4,29]],"date-time":"2021-04-29T00:00:00Z","timestamp":1619654400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Academy of Finland","award":["312559"],"award-info":[{"award-number":["312559"]}]},{"name":"Academy of Finland","award":["306539"],"award-info":[{"award-number":["306539"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>European aspen (Populus tremula L.) is a keystone species for biodiversity of boreal forests. Large-diameter aspens maintain the diversity of hundreds of species, many of which are threatened in Fennoscandia. Due to a low economic value and relatively sparse and scattered occurrence of aspen in boreal forests, there is a lack of information of the spatial and temporal distribution of aspen, which hampers efficient planning and implementation of sustainable forest management practices and conservation efforts. Our objective was to assess identification of European aspen at the individual tree level in a southern boreal forest using high-resolution photogrammetric point cloud (PPC) and multispectral (MSP) orthomosaics acquired with an unmanned aerial vehicle (UAV). The structure-from-motion approach was applied to generate RGB imagery-based PPC to be used for individual tree-crown delineation. Multispectral data were collected using two UAV cameras: Parrot Sequoia and MicaSense RedEdge-M. Tree-crown outlines were obtained from watershed segmentation of PPC data and intersected with multispectral mosaics to extract and calculate spectral metrics for individual trees. We assessed the role of spectral data features extracted from PPC and multispectral mosaics and a combination of it, using a machine learning classifier\u2014Support Vector Machine (SVM) to perform two different classifications: discrimination of aspen from the other species combined into one class and classification of all four species (aspen, birch, pine, spruce) simultaneously. In the first scenario, the highest classification accuracy of 84% (F1-score) for aspen and overall accuracy of 90.1% was achieved using only RGB features from PPC, whereas in the second scenario, the highest classification accuracy of 86 % (F1-score) for aspen and overall accuracy of 83.3% was achieved using the combination of RGB and MSP features. The proposed method provides a new possibility for the rapid assessment of aspen occurrence to enable more efficient forest management as well as contribute to biodiversity monitoring and conservation efforts in boreal forests.<\/jats:p>","DOI":"10.3390\/rs13091723","type":"journal-article","created":{"date-parts":[[2021,4,29]],"date-time":"2021-04-29T10:30:41Z","timestamp":1619692241000},"page":"1723","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Detection of European Aspen (Populus tremula L.) Based on an Unmanned Aerial Vehicle Approach in Boreal Forests"],"prefix":"10.3390","volume":"13","author":[{"given":"Anton","family":"Kuzmin","sequence":"first","affiliation":[{"name":"Department of Geographical and Historical Studies, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland"},{"name":"School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland"}]},{"given":"Lauri","family":"Korhonen","sequence":"additional","affiliation":[{"name":"School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland"}]},{"given":"Sonja","family":"Kivinen","sequence":"additional","affiliation":[{"name":"Department of Geographical and Historical Studies, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland"},{"name":"Finnish Environment Institute, Biodiversity Centre, Latokartanonkaari 11, FI-00790 Helsinki, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1039-3357","authenticated-orcid":false,"given":"Pekka","family":"Hurskainen","sequence":"additional","affiliation":[{"name":"Finnish Environment Institute, Biodiversity Centre, Latokartanonkaari 11, FI-00790 Helsinki, Finland"},{"name":"Earth Change Observation Laboratory, Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland"}]},{"given":"Pasi","family":"Korpelainen","sequence":"additional","affiliation":[{"name":"Department of Geographical and Historical Studies, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5509-6922","authenticated-orcid":false,"given":"Topi","family":"Tanhuanp\u00e4\u00e4","sequence":"additional","affiliation":[{"name":"Department of Geographical and Historical Studies, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland"},{"name":"Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014 Helsinki, Finland"}]},{"given":"Matti","family":"Maltamo","sequence":"additional","affiliation":[{"name":"School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5889-8402","authenticated-orcid":false,"given":"Petteri","family":"Vihervaara","sequence":"additional","affiliation":[{"name":"Finnish Environment Institute, Biodiversity Centre, Latokartanonkaari 11, FI-00790 Helsinki, Finland"}]},{"given":"Timo","family":"Kumpula","sequence":"additional","affiliation":[{"name":"Department of Geographical and Historical Studies, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland"}]}],"member":"1968","published-online":{"date-parts":[[2021,4,29]]},"reference":[{"key":"ref_1","first-page":"373","article-title":"Red-listed boreal forest species of Finland: Associations with forest structure, tree species, and decaying wood","volume":"43","author":"Tikkanen","year":"2006","journal-title":"Ann. Zool. 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