{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,16]],"date-time":"2026-01-16T12:41:00Z","timestamp":1768567260150,"version":"3.49.0"},"reference-count":37,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2018,7,21]],"date-time":"2018-07-21T00:00:00Z","timestamp":1532131200000},"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>The gap fractions of three mature hemi-boreal forest stands in Estonia were estimated using the LAI-2000 plant canopy analyzer ( LI-COR Biosciences, Lincoln, NE, USA), the TRAC instrument (Edgewall, Miami, FL, USA), Cajanus\u2019 tube, hemispherical photos, as well as terrestrial (TLS) and airborne (ALS) laser scanners. ALS measurements with an 8-year interval confirmed that changes in the structure of mature forest stands are slow, and that measurements in the same season of different years should be well comparable. Gap fraction estimates varied considerably depending on the instruments and methods used. None of the methods considered for the estimation of gap fraction of forest canopies proved superior to others. The increasing spatial resolution of new ALS devices allows the canopy structure to be analyzed in more detail than was possible before. The high vertical resolution of point clouds improves the possibility of estimating the stand height, crown length, and clumping of foliage in the canopy. The clumping\/regularity of the foliage in a forest canopy is correlated with tree height, crown length, and basal area. The method suggested herein for the estimation of foliage clumping allows the leaf area estimates of forest canopies to be improved.<\/jats:p>","DOI":"10.3390\/rs10071153","type":"journal-article","created":{"date-parts":[[2018,7,24]],"date-time":"2018-07-24T02:58:56Z","timestamp":1532401136000},"page":"1153","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":29,"title":["Estimation of Gap Fraction and Foliage Clumping in Forest Canopies"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7458-1467","authenticated-orcid":false,"given":"Andres","family":"Kuusk","sequence":"first","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0396-2072","authenticated-orcid":false,"given":"Jan","family":"Pisek","sequence":"additional","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0951-7933","authenticated-orcid":false,"given":"Mait","family":"Lang","sequence":"additional","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"},{"name":"Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia"}]},{"given":"Silja","family":"M\u00e4rdla","sequence":"additional","affiliation":[{"name":"Department of Civil Engineering and Architecture, Road Engineering and Geodesy Research Group, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia"}]}],"member":"1968","published-online":{"date-parts":[[2018,7,21]]},"reference":[{"key":"ref_1","first-page":"267","article-title":"The point method of pasture analysis","volume":"46","author":"Levy","year":"1933","journal-title":"N. 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