{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T00:48:55Z","timestamp":1775695735770,"version":"3.50.1"},"reference-count":51,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2018,2,9]],"date-time":"2018-02-09T00:00:00Z","timestamp":1518134400000},"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>Leaf nitrogen concentration (leaf N, %) is an essential component for understanding biogeochemical cycling. Leaf N is a good indicator of grass or forage quality, which is important for understanding the movements and feeding patterns of herbivores. Leaf N can be used as input for rangeland carrying capacity and stocking rate models. The estimation of leaf N has been successful using hyperspectral and commercial high spatial resolution satellite data such as WorldView-2 and RapidEye. Empirical methods have been used successfully to estimate leaf N, on the basis that it correlates with leaf chlorophyll. As such, leaf N was estimated using red edge based indices. The new Sentinel-2 sensor has two red edge bands, is freely available, and could further improve the estimation of leaf N at a regional scale. The objective of this study is to develop red edge based Sentinel-2 models derived from an analytical spectral device (ASD) spectrometer to map and monitor leaf N using Sentinel-2 images. Field work for leaf N and ASD data were collected in 2014 (December) in and around Kruger National Park, South Africa. ASD data were resampled to the Sentinel-2 spectral configuration using the spectral response function. The Sentinel-2 data for various dates were acquired from the European Space Agency (ESA) portal. The Sentinel-2 atmospheric correction (Sen2Cor) process was implemented. Simple empirical regression was used to estimate leaf N. High leaf N prediction accuracy was achieved at the ASD level and the best model was inverted on Sentinel-2 images to explain leaf N distribution at a regional scale over time. The spatial distribution of leaf N is influenced by the underlying geological substrate, fire frequency and other environmental variables. This study is a demonstration of how ASD data can be used to calibrate Sentinel-2 for leaf N estimation and mapping.<\/jats:p>","DOI":"10.3390\/rs10020269","type":"journal-article","created":{"date-parts":[[2018,2,9]],"date-time":"2018-02-09T12:46:27Z","timestamp":1518180387000},"page":"269","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":40,"title":["Explaining Leaf Nitrogen Distribution in a Semi-Arid Environment Predicted on Sentinel-2 Imagery Using a Field Spectroscopy Derived Model"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9917-9754","authenticated-orcid":false,"given":"Abel","family":"Ramoelo","sequence":"first","affiliation":[{"name":"Earth Observation Research Group, Natural Resources and the Environment Unit, Council for Scientific and Industrial Research (CSIR), Pretoria 0001, South Africa"},{"name":"Risk and Vulnerability Assessment Centre, University of Limpopo, Sovenga 0727, South Africa"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4435-5375","authenticated-orcid":false,"given":"Moses","family":"Cho","sequence":"additional","affiliation":[{"name":"Earth Observation Research Group, Natural Resources and the Environment Unit, Council for Scientific and Industrial Research (CSIR), Pretoria 0001, South Africa"},{"name":"Department of Plant and Plant Science, University of Pretoria, Pretoria 0001, South Africa"}]}],"member":"1968","published-online":{"date-parts":[[2018,2,9]]},"reference":[{"key":"ref_1","first-page":"17","article-title":"ARS range research","volume":"14","author":"Child","year":"1992","journal-title":"Rangelands"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"422","DOI":"10.2307\/4002737","article-title":"Range condition assessment and the concept of thresholds: A viewpoint","volume":"44","author":"Friedl","year":"1991","journal-title":"J. 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