{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,2]],"date-time":"2026-02-02T11:53:07Z","timestamp":1770033187413,"version":"3.49.0"},"reference-count":104,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,1,23]],"date-time":"2021-01-23T00:00:00Z","timestamp":1611360000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001824","name":"Grantov\u00e1 Agentura \u010cesk\u00e9 Republiky","doi-asserted-by":"publisher","award":["17-05743S"],"award-info":[{"award-number":["17-05743S"]}],"id":[{"id":"10.13039\/501100001824","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001823","name":"Ministerstvo \u0160kolstv\u00ed, Ml\u00e1de\u017ee a T\u011blov\u00fdchovy","doi-asserted-by":"publisher","award":["LM2018123"],"award-info":[{"award-number":["LM2018123"]}],"id":[{"id":"10.13039\/501100001823","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Scaling leaf-level optical signals to the canopy level is essential for airborne and satellite-based forest monitoring. In evergreen trees, biophysical and optical traits may change as foliage ages. This study aims to evaluate the effect of age in Norway spruce needle on biophysical trait-prediction based on laboratory leaf-level spectra. Mature Norway spruce trees were sampled at forest stands in ten headwater catchments with different soil properties. Foliage biophysical traits (pigments, phenolics, lignin, cellulose, leaf mass per area, water, and nitrogen content) were assessed for three needle-age classes. Complementary samples for needle reflectance and transmittance were measured using an integrating sphere. Partial least square regression (PLSR) models were constructed for predicting needle biophysical traits from reflectance\u2014separating needle age classes and assessing all age classes together. The ten study sites differed in soil properties rather than in needle biophysical traits. Optical properties consistently varied among age classes; however, variation related to the soil conditions was less pronounced. The predictive power of PLSR models was needle-age dependent for all studied traits. The following traits were predicted with moderate accuracy: needle pigments, phenolics, leaf mass per area and water content. PLSR models always performed better if all needle age classes were included (rather than individual age classes separately). This also applied to needle-age independent traits (water and lignin). Thus, we recommend including not only current but also older needle traits as a ground truth for evergreen conifers with long needle lifespan.<\/jats:p>","DOI":"10.3390\/rs13030391","type":"journal-article","created":{"date-parts":[[2021,1,25]],"date-time":"2021-01-25T09:59:40Z","timestamp":1611568780000},"page":"391","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Foliage Biophysical Trait Prediction from Laboratory Spectra in Norway Spruce Is More Affected by Needle Age Than by Site Soil Conditions"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3060-641X","authenticated-orcid":false,"given":"Zuzana","family":"Lhot\u00e1kov\u00e1","sequence":"first","affiliation":[{"name":"Faculty of Science, Charles University, 12844 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Veronika","family":"Kopa\u010dkov\u00e1-Strnadov\u00e1","sequence":"additional","affiliation":[{"name":"Czech Geological Survey, 11821 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Filip","family":"Oulehle","sequence":"additional","affiliation":[{"name":"Czech Geological Survey, 11821 Prague, Czech Republic"},{"name":"Global Change Research Institute of the Czech Academy of Sciences, 60300 Brno, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7455-2834","authenticated-orcid":false,"given":"Lucie","family":"Homolov\u00e1","sequence":"additional","affiliation":[{"name":"Global Change Research Institute of the Czech Academy of Sciences, 60300 Brno, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eva","family":"Neuwirthov\u00e1","sequence":"additional","affiliation":[{"name":"Faculty of Science, Charles University, 12844 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7976-9645","authenticated-orcid":false,"given":"Marian","family":"\u0160vik","sequence":"additional","affiliation":[{"name":"Global Change Research Institute of the Czech Academy of Sciences, 60300 Brno, Czech Republic"},{"name":"Laboratory on Geoinformatics and Cartography, Department of Geography, Faculty of Science, Masaryk University, 61137 Brno, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1830-7556","authenticated-orcid":false,"given":"R\u016f\u017eena","family":"Janoutov\u00e1","sequence":"additional","affiliation":[{"name":"Global Change Research Institute of the Czech Academy of Sciences, 60300 Brno, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6912-1992","authenticated-orcid":false,"given":"Jana","family":"Albrechtov\u00e1","sequence":"additional","affiliation":[{"name":"Faculty of Science, Charles University, 12844 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3726","DOI":"10.1029\/2018JD029490","article-title":"Available Energy Partitioning During Drought at Two Norway Spruce Forests and a European Beech Forest in Central Europe","volume":"124","author":"McGloin","year":"2019","journal-title":"J. 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