Responses of the reflectance indices PRI and NDVI to experimental warming and drought in European shrublands along a north–south climatic gradient

Pille Mänd, Lea Hallik, Josep Peñuelas, Tiit Nilson, Pierpaolo Duce, Bridget A. Emmett, Claus Beier, Marc Estiarte, János Garadnai, Tibor Kalapos, Inger Kappel Schmidt, Edit Kovács-Láng, Patricia Prieto, Albert Tietema, Joke W. Westerveld, Olevi Kull

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The aim of this study was to evaluate the use of ground-based canopy reflectance measurements to detect changes in physiology and structure of vegetation in response to experimental warming and drought treatment at six European shrublands located along a North–South climatic gradient. We measured canopy reflectance, effective green leaf area index (green LAIe) and chlorophyll fluorescence of dominant species. The treatment effects on green LAIe varied among sites. We calculated three reflectance indices: photochemical reflectance index PRI [531 nm; 570 nm], normalized difference vegetation index NDVI680 [780 nm; 680 nm] using red spectral region, and NDVI570 [780 nm; 570 nm] using the same green spectral region as PRI. All three reflectance indices were significantly related to green LAIe and were able to detect changes in shrubland vegetation among treatments. In general warming treatment increased PRI and drought treatment reduced NDVI values. The significant treatment effect on photochemical efficiency of plants detected with PRI could not be detected by fluorescence measurements. However, we found canopy level measured PRI to be very sensitive to soil reflectance properties especially in vegetation areas with low green LAIe. As both soil reflectance and LAI varied between northern and southern sites it is problematic to draw universal conclusions of climate-derived changes in all vegetation types based merely on PRI measurements. We propose that canopy level PRI measurements can be more useful in areas of dense vegetation and dark soils.
    Original languageEnglish
    JournalRemote Sensing of Environment
    Volume114
    Issue number3
    Pages (from-to)626-636
    ISSN0034-4257
    DOIs
    Publication statusPublished - 2010

    Keywords

    • Bio systems
    • Environment and climate

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