{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,11]],"date-time":"2026-03-11T04:37:18Z","timestamp":1773203838011,"version":"3.50.1"},"reference-count":60,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2015,1,23]],"date-time":"2015-01-23T00:00:00Z","timestamp":1421971200000},"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 invasive shrub, Acacia longifolia, native to southeastern Australia, has a negative impact on vegetation and ecosystem functioning in Portuguese dune ecosystems. In order to spectrally discriminate A. longifolia from other non-native and native species, we developed a classification model based on leaf reflectance spectra (350\u20132500 nm) and condensed leaf tannin content. High variation of leaf tannin content is common for Mediterranean shrub and tree species, in particular between N-fixing and non-N-fixing species, as well as within the genus, Acacia. However, variation in leaf tannin content has not been studied in coastal dune ecosystems in southwest Portugal. We hypothesized that condensed tannin concentration varies significantly across species, further allowing for distinguishing invasive, nitrogen-fixing A. longifolia from other vegetation based on leaf spectral reflectance data. Spectral field measurements were carried out using an ASD FieldSpec FR spectroradiometer attached to an ASD leaf clip in order to collect 750 in situ leaf reflectance spectra of seven frequent plant species at three study sites in southwest Portugal. We applied partial least squares (PLS) regression to predict the obtained leaf reflectance spectra of A. longifolia individuals to their corresponding tannin concentration. A. longifolia had the lowest tannin concentration of all investigated species. Four wavelength regions (675\u2013710 nm, 1060\u20131170 nm, 1360\u20131450 nm and 1630\u20131740 nm) were identified as being highly correlated with tannin concentration. A spectra-based classification model of the different plant species was calculated using a principal component analysis-linear discriminant analysis (PCA-LDA). The best prediction of A. longifolia was achieved by using wavelength regions between 1360\u20131450 nm and 1630\u20131740 nm, resulting in a user\u2019s accuracy of 98.9%. In comparison, selecting the entire wavelength range, the best user accuracy only reached 86.5% for A. longifolia individuals.<\/jats:p>","DOI":"10.3390\/rs70201225","type":"journal-article","created":{"date-parts":[[2015,1,23]],"date-time":"2015-01-23T11:20:34Z","timestamp":1422012034000},"page":"1225-1241","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":55,"title":["Field Spectroscopy in the VNIR-SWIR Region to Discriminate between Mediterranean Native Plants and Exotic-Invasive Shrubs Based on Leaf Tannin Content"],"prefix":"10.3390","volume":"7","author":[{"given":"Jan","family":"Lehmann","sequence":"first","affiliation":[{"name":"Institute of Landscape Ecology, University of M\u00fcnster, Heisenbergstr. 2, M\u00fcnster 48149, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6075-5497","authenticated-orcid":false,"given":"Andr\u00e9","family":"Gro\u00dfe-Stoltenberg","sequence":"additional","affiliation":[{"name":"Institute of Landscape Ecology, University of M\u00fcnster, Heisenbergstr. 2, M\u00fcnster 48149, Germany"}]},{"given":"Meike","family":"R\u00f6mer","sequence":"additional","affiliation":[{"name":"Institute of Pharmaceutical Technology and Biopharmacy, University of M\u00fcnster, Corrensstr. 48, M\u00fcnster 48149, Germany"}]},{"given":"Jens","family":"Oldeland","sequence":"additional","affiliation":[{"name":"Biodiversity, Evolution and Ecology of Plants, University of Hamburg, Ohnhorststr. 18,  Hamburg 22609, Germany"}]}],"member":"1968","published-online":{"date-parts":[[2015,1,23]]},"reference":[{"key":"ref_1","first-page":"47","article-title":"Plants and secondary metabolites (Tannins): A review","volume":"1","author":"Hassanpour","year":"2011","journal-title":"IJFSE"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1016\/j.anifeedsci.2004.12.013","article-title":"Assessment of the digestibility of some Mediterranean shrubs by in vitro techniques","volume":"119","author":"Ammar","year":"2005","journal-title":"Anim. Feed Sci. Tech."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1016\/S0377-8401(01)00323-6","article-title":"Condensed tannin content of several shrub species from a mountain area in northern Spain, and its relationship to various indicators of nutritive value","volume":"95","author":"Frutos","year":"2002","journal-title":"Anim. Feed Sci. Tech."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"213","DOI":"10.1007\/BF00002937","article-title":"Nitrogen immobilization in leaf litter at two Mediterranean ecosystems of SW Spain","volume":"15","author":"Gallardo","year":"1992","journal-title":"Biogeochemistry"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1016\/S0301-6226(00)00174-3","article-title":"Utilization of low quality resources by small ruminants in Mediterranean agro-pastoral systems: The case of browse and aftermath cereal stubble","volume":"64","author":"Landau","year":"2000","journal-title":"Livest. Prod. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"333","DOI":"10.2307\/3546282","article-title":"Tannins in Mediterranean woodland species: Lack of response to browsing and thinning","volume":"71","author":"Perevolotsky","year":"1994","journal-title":"Oikos"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/j.smallrumres.2005.04.017","article-title":"Sheep and goat preference for and nutritional value of Mediterranean Maquis shrubs","volume":"64","author":"Rogosic","year":"2006","journal-title":"Small Ruminant Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1016\/S0301-6226(00)00175-5","article-title":"Deactivation of condensed tannins in Acacia cyanophylla Lindl. foliage by polyethylene glycol in feed blocks: Effect on feed intake, diet digestibility, nitrogen balance, microbial synthesis and growth by sheep","volume":"64","author":"Nefzaoui","year":"2000","journal-title":"Livest. Prod. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"203","DOI":"10.1016\/j.anifeedsci.2009.06.014","article-title":"Chemical composition, biological effects of tannin and in vitro nutritive value of selected browse species grown in the West Australian Mediterranean environment","volume":"153","author":"Krebs","year":"2009","journal-title":"Anim. Feed Sci. Tech."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1016\/j.apsoil.2008.04.004","article-title":"Short- and long-term impacts of Acacia longifolia invasion on the belowground processes of a Mediterranean coastal dune ecosystem","volume":"40","author":"Marchante","year":"2008","journal-title":"Appl. Soil Ecol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"788","DOI":"10.1111\/j.1472-4642.2011.00782.x","article-title":"Trees and shrubs as invasive alien species\u2014A global review","volume":"17","author":"Richardson","year":"2011","journal-title":"Divers. Distrib."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1015","DOI":"10.1111\/j.1472-4642.2011.00816.x","article-title":"Impacts of invasive Australian acacias: Implications for management and restoration","volume":"17","author":"Gaertner","year":"2011","journal-title":"Divers. Distrib."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1099","DOI":"10.1007\/s10530-011-9949-2","article-title":"Acacia longifolia invasion impacts vegetation structure and regeneration dynamics in open dunes and pine forests","volume":"13","author":"Rascher","year":"2011","journal-title":"Biol. Invasions"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1007\/s11258-009-9625-0","article-title":"High competitiveness of a resource demanding invasive Acacia under low resource supply","volume":"206","author":"Werner","year":"2010","journal-title":"Plant Ecol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1016\/j.actao.2010.11.005","article-title":"Influence of an exotic N2-fixing Acacia on community composition and N status of native Mediterranean species","volume":"37","year":"2011","journal-title":"Acta Oecologica"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"904","DOI":"10.1007\/s10021-011-9453-7","article-title":"Understory invasion by Acacia longifolia alters the water balance and carbon gain of a Mediterranean pine forest","volume":"14","author":"Rascher","year":"2011","journal-title":"Ecosystems"},{"key":"ref_17","first-page":"315","article-title":"Comparative tanning ability of extracts from four North American species of Acacia","volume":"84","author":"Seigler","year":"1989","journal-title":"J. Am. Leather Chem. Assoc."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1016\/0300-9629(94)90402-2","article-title":"Condensed tannin as anti-defoliate agent against browsing by giraffe (Giraffa camelopardalis) in the Kruger National Park","volume":"107","author":"Furstenburg","year":"1994","journal-title":"Comp. Biochem. Physiol. A"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Maiden, J.H. (1889). The Useful Native Plants of Australia, (Including Tasmania), Turner and Henderson.","DOI":"10.5962\/bhl.title.12190"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1023\/A:1026206511084","article-title":"Tannins in nutrient dynamics of forest ecosystems: A review","volume":"256","author":"Kraus","year":"2003","journal-title":"Plant Soil"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1007\/BF02913395","article-title":"Autecological traits of Halimium halimifolium in contrasting habitats under a Mediterranean type climate\u2014A review","volume":"34","author":"Barradas","year":"1999","journal-title":"Folia Geobot."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1551","DOI":"10.1016\/j.phytochem.2011.01.040","article-title":"Tannins in plant-herbivore interactions","volume":"72","author":"Barbehenn","year":"2011","journal-title":"Phytochemistry"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"S92","DOI":"10.1016\/j.rse.2007.08.001","article-title":"Progress in field spectroscopy","volume":"113","author":"Milton","year":"2009","journal-title":"Remote Sens. Environ."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1912","DOI":"10.1016\/j.rse.2007.02.043","article-title":"Remote sensing of native and invasive species in Hawaiian forests","volume":"112","author":"Asner","year":"2008","journal-title":"Remote Sens. Environ."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Calvi\u00f1o-Cancela, M., M\u00e9ndez-Rial, R., Reguera-Salgado, J., and Mart\u00edn-Herrero, J. (2014). Alien plant monitoring with ultralight airborne imaging spectroscopy. PLoS One, 9.","DOI":"10.1371\/journal.pone.0102381"},{"key":"ref_26","first-page":"51","article-title":"The vegetation of dunes of southwest Portugal","volume":"2","author":"Costa","year":"1994","journal-title":"Silva Lusitana"},{"key":"ref_27","first-page":"29","article-title":"Phytosociological associations and Natura 2000 habitats of Portuguese coastal dunes","volume":"44","year":"2008","journal-title":"Fitosociologia"},{"key":"ref_28","first-page":"322","article-title":"Photometric methods of tannin analysis for black wattle tannin","volume":"35","author":"Roux","year":"1951","journal-title":"J. Soc. Leather Trades Chem."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1201","DOI":"10.1016\/j.trac.2009.07.007","article-title":"Review of the most common pre-processing techniques for near-infrared spectra","volume":"28","author":"Rinnan","year":"2009","journal-title":"TrAC Trends in Analytical Chemistry"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1627","DOI":"10.1021\/ac60214a047","article-title":"Smoothing and differentiation of data by simplified least squares procedures","volume":"36","author":"Savitzky","year":"1964","journal-title":"Anal. Chem."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"2742","DOI":"10.1016\/j.rse.2011.06.016","article-title":"Optimizing spectral indices and chemometric analysis of leaf chemical properties using radiative transfer modeling","volume":"115","author":"Gitelson","year":"2011","journal-title":"Remote Sens. Environ."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"672","DOI":"10.1016\/j.isprsjprs.2011.05.002","article-title":"Wavelength selection and spectral discrimination for paddy rice, with laboratory measurements of hyperspectral leaf reflectance","volume":"66","author":"Song","year":"2011","journal-title":"ISPRS J. Photogramm. Remote Sens."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"504","DOI":"10.1007\/s10021-012-9526-2","article-title":"Sources of canopy chemical and spectral diversity in lowland bornean forest","volume":"15","author":"Asner","year":"2012","journal-title":"Ecosystems"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"3958","DOI":"10.1016\/j.rse.2008.07.003","article-title":"Spectral and chemical analysis of tropical forests: Scaling from leaf to canopy levels","volume":"112","author":"Asner","year":"2008","journal-title":"Remote Sens. Environ."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1016\/S0169-7439(01)00155-1","article-title":"PLS-regression: A basic tool of chemometrics","volume":"58","year":"2001","journal-title":"Chemometr. Intell. Lab. Syst."},{"key":"ref_36","first-page":"97","article-title":"Partial least squares regression and projection on latent structure regression (PLS Regression)","volume":"2","author":"Abdi","year":"2010","journal-title":"Comp. Stat."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1016\/j.rse.2005.03.009","article-title":"Hyperspectral discrimination of tropical rain forest tree species at leaf to crown scales","volume":"96","author":"Clark","year":"2005","journal-title":"Remote Sens. Environ."},{"key":"ref_38","unstructured":"Naes, T., Isaksson, T., Fearn, T., and Davies, T. (2002). A user Friendly guide to Multivariate Calibration and Classification, NIR Publications."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1007\/s10661-007-9843-7","article-title":"Invasive species change detection using artificial neural networks and CASI hyperspectral imagery","volume":"140","author":"Pu","year":"2008","journal-title":"Environ. Monit. Assess."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"381","DOI":"10.1111\/j.1472-4642.2011.00761.x","article-title":"Benefits of hyperspectral remote sensing for tracking plant invasions","volume":"17","author":"He","year":"2011","journal-title":"Divers. Distrib."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1016\/0960-8524(91)90179-N","article-title":"Tannins and related polyphenols from ten common Acacia species of India","volume":"36","author":"Devi","year":"1991","journal-title":"Bioresour. Tech."},{"key":"ref_42","unstructured":"Humphries, S.G. (1963). Biogenesis of Natural Compounds,, Pergamon Press. [2nd ed.]."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1887","DOI":"10.1021\/jf970975b","article-title":"High molecular weight plant polyphenolics (Tannins) as biological antioxidants","volume":"46","author":"Hagerman","year":"1998","journal-title":"J. Agr. Food Chem."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1111\/j.1751-1097.1999.tb01944.x","article-title":"Environmental significance of anthocyanins in plant stress responses","volume":"70","year":"1999","journal-title":"Photochem. Photobiol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1111\/j.1469-8137.2004.01217.x","article-title":"Proanthocyanidins\u2014A final frontier in flavonoid research?","volume":"165","author":"Dixon","year":"2005","journal-title":"New Phytol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"1255","DOI":"10.1007\/s10886-010-9862-7","article-title":"Higher allocation to low cost chemical defenses in invasive species of Hawaii","volume":"36","author":"Sardans","year":"2010","journal-title":"J. Chem. Ecol."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"894","DOI":"10.1111\/j.1365-2745.2012.01980.x","article-title":"Genetic variation in anti-herbivore chemical defences in an invasive plant","volume":"100","author":"Wang","year":"2012","journal-title":"J. Ecol."},{"key":"ref_48","unstructured":"Omelchuk, O. The Content of Phenolics and Tannins in Native and Invasive Solidago Species. Available online: http:\/\/phytomorphology.org\/PDF\/MP4\/04091092.pdf."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"887","DOI":"10.2307\/2261425","article-title":"Evolution of increased competitive ability in invasive nonindigenous plants: A hypothesis","volume":"83","author":"Blossey","year":"1995","journal-title":"J. Ecol."},{"key":"ref_50","first-page":"32","article-title":"Hyperspectral reflectance of leaves and flowers of an outbreak species discriminates season and successional stage of vegetation","volume":"24","author":"Carvalho","year":"2013","journal-title":"Int. J. Appl. Earth Obs. Geoinf."},{"key":"ref_51","unstructured":"Hagerman, A.E. (2002). Tannin Handbook, Miami University."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"38","DOI":"10.1562\/0031-8655(2001)074<0038:OPANEO>2.0.CO;2","article-title":"Optical properties and nondestructive estimation of anthocyanin content in plant leaves","volume":"74","author":"Gitelson","year":"2001","journal-title":"Photochem. Photobiol."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1046\/j.1469-8137.1999.00424.x","article-title":"Assessing leaf pigment content and activity with a reflectometer","volume":"143","author":"Gamon","year":"1999","journal-title":"New Phytol."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"855","DOI":"10.1093\/jxb\/erl123","article-title":"Hyperspectral remote sensing of plant pigments","volume":"58","author":"Blackburn","year":"2007","journal-title":"J. Exp. Bot."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1016\/0034-4257(89)90069-2","article-title":"Remote sensing of foliar chemistry","volume":"30","author":"Curran","year":"1989","journal-title":"Remote Sens. Environ."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"3039","DOI":"10.1080\/01431160110104683","article-title":"Spectral characteristics of lignin and soluble phenolics in the near infrared: A comparative study","volume":"23","author":"Soukupova","year":"2002","journal-title":"Int. J. Remote Sens."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1413","DOI":"10.1080\/01431160500497119","article-title":"A bootstrap procedure to select hyperspectral wavebands related to tannin content","volume":"27","author":"Ferwerda","year":"2006","journal-title":"Int. J. Remote Sens."},{"key":"ref_58","doi-asserted-by":"crossref","unstructured":"Hemingway, R.W., and Laks, P.E. (1992). Plant Polyphenols, Springer.","DOI":"10.1007\/978-1-4615-3476-1"},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"7631","DOI":"10.1021\/jf801563z","article-title":"Measurement of condensed tannins and dry matter in red grape homogenates using near infrared spectroscopy and partial least squares","volume":"56","year":"2008","journal-title":"J. Agr. Food Chem."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"267","DOI":"10.1016\/S0034-4257(98)00084-4","article-title":"Spectroscopic determination of leaf biochemistry using band-depth analysis of absorption features and stepwise multiple linear regression","volume":"67","author":"Kokaly","year":"1999","journal-title":"Remote Sens. Environ."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/7\/2\/1225\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T20:41:55Z","timestamp":1760215315000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/7\/2\/1225"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,1,23]]},"references-count":60,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2015,2]]}},"alternative-id":["rs70201225"],"URL":"https:\/\/doi.org\/10.3390\/rs70201225","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2015,1,23]]}}}