Separating reflectance signatures of shrub species – a case study in the Central Greater Caucasus

• Published in: Applied Vegetation Science
• Main Authors: Magiera, Anja, Feilhauer, Hannes, Tephnadze, Nato, Waldhardt, Rainer, Otte, Annette
• Other Authors: Rocchini, Duccio, Volkswagen Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2015
• Subjects: Arctic
• Online Access: http://dx.doi.org/10.1111/avsc.12205; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Favsc.12205; https://onlinelibrary.wiley.com/doi/pdf/10.1111/avsc.12205

Abstract Questions Shrub encroachment has been observed in many alpine and arctic environments and is expected to significantly alter these ecosystems. Mapping these processes with remote sensing is a powerful tool for monitoring purposes. Thus, we test the distinctiveness of the reflectance signature of target species relative to their co‐occurring shrub species using uni‐ and multivariate analyses for an alpine ecosystem. We ask: (i) is it possible to differentiate shrub species with a unique growth form by their reflectance signature; (ii) which of the tested multispectral sensors produces the best separation; and (iii) how are the results affected by the timing of data acquisition in the vegetation period? Location Kazbegi district, Central Greater Caucasus, Georgia. Method We analysed three shrub ( Betula litwinowii , Rhododendron caucasicum , Hippophae rhamnoides ) and one tall forb ( Veratrum lobelianum ) species occurring in the sub‐alpine to alpine belt The vegetation of 52 relevés was analysed using non‐metric multidimensional scaling and indicator species analysis. From field spectrometric data we simulated multispectral sensor bands ( IKONOS , Quickbird 2, RapidEye, WorldView‐2) directly taken from the target species. We analysed the reflectance signature in RapidEye data from June and September. For all data sets we calculated the Jeffries‐Matusita distance ( JMD ) as a separation measure and tested the reflectance signature of the single bands for differences. Results Betula litwinowii and V. lobelianum always co‐occurred in our data. A high abundance of B. litwinowii could also be found in the Rhododendron cluster and vice versa, whereas the Hippophae cluster was more homogeneous. Simulated bands showed good overall separation ( JMD 1.58–2.00) of the target species. The separation increased with the increase of number of bands and inclusion of the red edge band. There was a general trend in which the reflectance from satellite images produced a lower separation ( JMD 1.20–1.55) than the ...