Forest damage, waterflow and digital elevation models : a case study of Krkonose National Park, Czech Republic

Abstract: In the 1970's, a widespread deterioration in forest health in Europe was observed, first for the European fir and, subsequently, also for many other tree species. Now a large portion of the forests in Europe is affected by forest decline to varying degrees. The first aim of the study is to investigate if forest damage and forest die-back have lead to a change in waterflow. The study area is the mountain range Krkonae National Park in northern Czech Republic. The national park is situated in a region well known as the Black Triangle, where Germany, Poland and Czech Republic meet. Acidic emissions of sulphur dioxide have caused massive deforestation of spruce mono-cultures, especially at and above the elevations of 750 m above sea level. Forest die-back till today involves a loss in forest cover of about 25%, or about 8,000 ha, of the total area. Seven catchments in the national park were investigated regarding degree of forest damage, clear-cuts, topography, catchment size and age offorest stands. The results were then compared with changes in waterflow approximately over the period 1984-1992. The method used for investigating waterflow changes was to remove the effects of precipitation by making a ratio between data of waterflow and precipitation. In general, waterflow slightly decreased during the period whereas there was an increase in forest damage and clear-cuts. These results indicate a weak relationship between waterflow and forest changes. However, large deforestation was detected in waterflow, especially for the catchments smaller than 10 km2. To be able to model waterflow changes and soil erosion in the national park in the future it is of great importance to have reliable elevation maps of the area. Hence, the second aim of the study is to evaluate Digital Elevation Models (DEMs) and Digital Terrain Models (DTMs) of different resolutions (15-m and 30-m resolution maps) regarding elevation, slope and aspect in the Krkono§e National Park The field data for the investigation was collected in the national park with UPS receiver, angle meter and compass. Root Mean Square Error (RMSE) was calculated for the differences between field values and DEMs/DTMs. The results show that regarding elevation, the higher resolution DEM had lower RMSE values, but in slope and aspect, the lower resolution DTAls had lower RMSE. This result is probably due to that the 30-m measurements were performed in more open areas. An RMSE of approximately 3 m in elevation in both 15-m and 30-m resolution layers must be regarded as a minor error.