Thermal and Optical Indices for Wetland Habitats, are They Showing the Same Thing?

Abstract

This study is focused on detecting vegetation stress in natural and seminatural riparian wetland ecosystems. Wetland ecosystems play an important role at the local and global scale. They provide various ecosystem services as long as they are in good condition. The global climate change influences a local environment, in which wetlands health become an indicator of drought conditions. Persisting adverse conditions might lead to irreversible changes in these precious ecosystems. Hence, modern methods for the monitoring of these ecosystems are required to be developed. In the scope of this study, based on basic meteorological elements (air temperature and humidity) and canopy temperature from two different platforms (meteorological tower and Landsat-8 satellite), crop water stress index (CWSI) was proposed for riparian wetland habitats and wet meadows monitoring. The study was conducted in the Upper Biebrza Basin (NE, Poland). As a first step, CWSI was calculated based on meteorological measurements and compared with CWSI calculated for surrounding Landsat-8 pixels covered by the same land-use type as one being in the tower sensor field of view. CWSI from both sensors were in significant agreement. In the second step of the analysis, CWSI and selected optical indices were calculated for a longer period based on satellite data. Those indices were compared with test if they indicate the same conditions, or if their indications are inconsistent. Results show that CWSI and optical indices indicate different plant stress factors. Hence, for proper wetlands condition assessment, still more research is required to properly assess their conditions and its causes.