Temporal changes in Norway spruce physiological status using hyperspectral data: A case study of mountainous forests affected by long-term acidic depositions

Abstract

A decline in the Norway spruce forests of the Krušné Hory Mts., Czech Republic, has been reported since the early 1950's. It was attributed to the combination of severe atmospheric pollution and climatic conditions. The physiological status of the Norway spruce forests has been assessed using ground-truth data (biochemical and spectroscopic data) as well as two hyperspectral data sets acquired in 1998 (ASAS sensor, NASA Goddard Space Flight Center) and in 2013 (APEX sensor, developed by a Swiss-Belgian consortium on behalf of ESA, currently operated by VITO). The very first results coming from the analysis of the foliar chemistry indicate that the stands exhibit different physiological statuses corresponding to the pollution gradients in 1998 and 2013. Slight improvement of the Norway spruce physiological status was recorded in the eastern part of the mountains (e.g., total carotenoids to chlorophyll ratio), while the status of the western-located stands slightly worsened. These findings may correspond to a tremendous decrease in the atmospheric pollution which was most severe in the east. However, remains of the pollution can be still seen in the adverse soils conditions. Further linkages among foliar chemistry and reflectance and soil chemistry are currently under investigation.