The development of forest damage — control and prognosis on the basis of remote sensing data

Abstract

Forest damage can be caused by three types of stress which exercise their influence by predisposing, causative and contributory factors. Predisposing factors, above all permanent immision stress, cause the general diminishing of the trees' vitality. Causative fators such as long and extreme periods of dryness cause a fast and evident deterioration of the forest stand, contributory factors as eg pest attacks cause their mortification. When using remote sensing data to monitor the development of forest damage it is necessary therefore not only to pay attention to spectral signatures characterizing the degree of green space and thus the information of the canopy but also to spectral signs showing the water supply of the stands. This has not been done so far though nowadays the necessary multispectral satellite data are on regular offer. For this reason it may be suggested that the existing possibilities to predict the development of forest damage on the basis of remote sensing data have not yet been fully used.

In order to examine these possibilities, in the environs of Berlin, ie in the east and south of the Land of Brandenburg both the vegetation index which has been known from literature for a long time and an index for the difference in remission identifying the water bands in the short-wave infrared have been calculated on the basis of Landsat-TM data. A multi-temporal comparison shows that despite the bad conditions of the forest in 1991 on the test site located north-east of Berlin due to a relatively good water supply in that year the pine forest damage had not progressed in 1992. This allows to draw the conclusion that at least in the pine forests of the East German interior lowland the development of forest damage is essentially determined by dryness stress. In this way on the basis of 1992 Landsat-TM data there was not only an inventory made of the actual condition of the forest on the east and south-east of the Land of Brandenburg but also trends of damage progress shown. The damage classification of pine stands be completed by a prognosis as to the development of damage.