Estimating carbon dioxide fluxes from temperate mountain grasslands using broad-band vegetation indices

• Main Authors: G. Wohlfahrt, S. Pilloni, L. Hörtnagl, A. Hammerle
• Format: Article
• Language: English
• Published: Copernicus Publications 2010-02-01
• Series: Biogeosciences
• Online Access: http://www.biogeosciences.net/7/683/2010/bg-7-683-2010.pdf

The broad-band normalised difference vegetation index (NDVI) and the simple ratio (SR) were calculated from measurements of reflectance of photosynthetically active and short-wave radiation at two temperate mountain grasslands in Austria and related to the net ecosystem CO<sub>2</sub> exchange (NEE) measured concurrently by means of the eddy covariance method. There was no significant statistical difference between the relationships of midday mean NEE with narrow- and broad-band NDVI and SR, measured during and calculated for that same time window, respectively. The skill of broad-band NDVI and SR in predicting CO<sub>2</sub> fluxes was higher for metrics dominated by gross photosynthesis and lowest for ecosystem respiration, with NEE in between. A method based on a simple light response model whose parameters were parameterised based on broad-band NDVI allowed to improve predictions of daily NEE and is suggested to hold promise for filling gaps in the NEE time series. Relationships of CO<sub>2</sub> flux metrics with broad-band NDVI and SR however generally differed between the two studied grassland sites indicting an influence of additional factors not yet accounted for.