The radiance contrast of forest‐to‐clearcut edges on a medium resolution Landsat Enhanced Thematic Mapper satellite winter image

Abstract

Forest logging results in decreased and fragmented forest area and the increased appearance of edge habitats. The monitoring of forest area and particularly, the detection of changes over the years relies on correctly determined forest edge locations. Radiance contrast of forest clearcut edges Our objective was to characterize the radiance contrast at the sharp forest edges of recently created clearcuts of boreal and boreo‐nemoral forests in Estonia. Radiance data were derived from a medium resolution Landsat Enhanced Thematic Mapper (ETM+) satellite image taken in late winter, in March. In the winter image there is a high radiance contrast at the forest to clearcut boundary area. This radiance contrast was investigated in the visible and near infrared spectral regions (ETM+ bands 1–4) with 30m‐pixel‐size resolution in the spectral bands and 15m‐pixel‐size in the ETM+ panchromatic band. The analyses of radiance contrast at clearcut to forest edges reveal the effects of stand parameters, clearcut age and azimuthal exposure. The results of the analyses show that the radiance contrast between forest and clearcut area depends on the stand height and stem volume of coniferous trees in the first and the second tree layer. The stem volume of deciduous trees had no statistically significant effect on the variation of radiance contrast at the forest edge. A significant non‐linear effect of the edge exposure to sun was found, indicating a shade length effect. Shade and forest structure affect edge detection on medium resolution satellite images.