Monitoring the forest health status using remote sensing methods

A rising proportion of sanitary felling in the annual felling plans requires a special attention paid to forest health status and the proportion of unplanned felling. In the past ten years, the proportion of unplanned fir felling within the total felling plan was 57%-Gospić, and 37% of pedunculated oak-Vinkovci. Such high proportions (dead trees) have adverse impacts on sustainable management. Priority stands of poorer health should be located in order to take timely measures for keeping their vitality and production at optimal levels. Since the field status is required in the shortest possible time, we suggest remote sensing methods, particularly the colour infrared (CIR) aerial photography. The to date research associates the increased tree dieback with the various habitat and stand features (elevation, exposition, inclination, soil, structure), the abiotic and biotic factors (silver fire needle moth, mildew, mistletoe), though the real causes remain unknown. The aim of this research is to establish the relations among the forest health conditions, habitats, stands, and the abiotic/biotic factors. The purpose of the research is by using photointerpretation, to establish and analyse forest damage, to collect the data on the damage area distribution, to study the impacts on the forest health status and to get an answer to the issue on a possible damage cause. Multispectral imaging (digital camera MS-3100 and hyperspectral scanner V9) of mistletoe on fir will provide the images on the basis of which the method efficiency will be analysed and the operation survey procedures defined. High resolution satellite image will also be acquired, to use it with CIR photographs in determining and inventory taking of the damaged forests, required by management and forest protection practices. The following results are expected: objective view into the forest damage status (database); damage maps and GIS analyses of environmental factors in the massive tree dieback. The results may be checked and compared, since the interpretation is done under precisely assessed conditions that are uniform over the whole area. The research is significant for the assessment and monitoring of the occurrence, its distribution and progress, as well as the causes of the dieback. Based on this, corresponding actions and operations can be carried out. The monitoring of particular symptoms will help to establish the current health status. Repeated survey will predict possible future development.