Possibilities of using a tree height map derived from a digital surface model in a karst area

Abstract

The claim to understand the wider context of the karsts’ environment only appeared in the last few years, especially with regard to the vegetation cover. The composition and growth rate of vegetation is defined by an interaction between the environmental factors and therefore changes in these characteristics can indicate the changes of the whole system. Due to their geographical position the potential vegetation of Hungarian karsts is mainly mixed-stand deciduous forest. In the case of an old, near-natural forest one of the indicators describing the cumulative effect of the environmental factors is the height of the trees. These data are rather hard to acquire by field measurements for large areas but they are easy and fast to produce by remote sensing methods. One of these methods is deriving tree height from a Digital Surface Model. In this study we examined the possibilities of using this method in a karst area. In order to determine the accuracy of a tree height model derived from aerial photos of 2004 we carried out two series of field measurements in the Aggtelek karst area in summer 2005. Although the error of the model, the errors of navigation and that of the field measurements add up, which makes statistical analysis complicated; it is clear that the model describes stand height rather than the height of individuals. On the basis of the results our conclusion is that tree height maps derived from Digital Surface Models can serve as a useful complementary to the forest management plans, especially in areas where the resolution of the plan does not match the diversity of the surface.