TY - JOUR
T1 - Responses of the reflectance indices PRI and NDVI to experimental warming and drought in Europan shrublands along a north-south climatic gradient
AU - Mänd, Pille
AU - Hallik, Lea
AU - Peñuelas, Josep
AU - Nielsen, Tiit
AU - Duce, Pierpaolo
AU - Emmett, Bridget A.
AU - Beier, Claus
AU - Estiarte, Marc
AU - Garadnai, János
AU - Kalapos, Tibor
AU - Schmidt, Inger Kappel
AU - Kovács-Láng, Edit
AU - Prieto, Patricia
AU - Tietema, Albert
AU - Westerveld, Joke W.
AU - Kull, Olevi
PY - 2010/3/15
Y1 - 2010/3/15
N2 - 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.
AB - 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.
U2 - 10.1016/j.rse.2009.11.003
DO - 10.1016/j.rse.2009.11.003
M3 - Journal article
SN - 0034-4257
VL - 114
SP - 626
EP - 636
JO - Remote Sensing of Environment
JF - Remote Sensing of Environment
IS - 3
ER -
