EARSeL eProceedings Vol. 3, No. 2, 154-165, 2004

Abstract
The coastal dunes belong to the most important ecosystems in the Netherlands, but they have also suffered from prolonged desiccation, changes in land use, diminished coastal dynamics, and acidification. Environmental management is applied to counteract the deterioration of threatened dune vegetation and to maintain biodiversity. An efficient and reliable monitoring system is necessary to investigate autonomous vegetation development and to evaluate the effects of nature conservation and restoration measures such as cattle grazing. Monitoring of the vegetation is supported by the classification of remote sensing images. As the spectral characteristics of vegetation change during the growing season, the discrimination between vegetation types may vary too. In order to determine an appropriate period for collecting hyperspectral imagery of coastal sand dunes, a GER field spectrometer was used to collect reflectance data of several dune grassland types in the Amsterdam Water Supply Dunes in different periods from May to July 2001. The data were transformed into the spectral configuration of a hyperspectral GER EPS-A scanner, which was used to make a hyperspectral image of this area. The reflectance spectra were analysed for statistically significant differences between vegetation types. The results illustrate that the spectral characteristics of dry dune vegetation do change during the growing season. It is concluded that the best discrimination is achieved by the end of May and that a field spectrometer can help to determine a convenient period for hyperspectral imagery.

ISSN 1729-3782