Montane peatland response to drought: Evidence from multispectral and thermal UAS monitoring

• UAS monitoring revealed extensive transitions between wet and dry zones of peatland during in response to drought. • Shrinkage of shallow waterlogged open peat areas by 80% during drought. • Divergent land surface temperature response of peatland landcover categories over season. • Shallow submerged open peat land thermal response closer to bare peat rather than to stable water bodies. • Effectiveness of UAS monitoring in assessing changes of spatially distributed small elements. This paper investigates the response of mid-latitude montane peatlands to climate warming, focusing on changes occurring in a montane peat bog during a drought period. Unmanned Aerial Systems (UAS) equipped with multispectral and thermal sensors were used for high-resolution monitoring to analyze qualitative changes within the peat bog and their spatial distribution. The study was conducted in the Rokytka mountain peat bog in Šumava National Park, Czech Republic, which is one of the largest mountain peat bog complexes in Central Europe. Monitoring took place during the 2019 vegetation season, coinciding with the peak of the 2015–2019 drought. The recurrent UAS imaging campaigns were complemented by continuous hydrological and hydropedological monitoring and in-situ calibration measurements. The findings revealed diverging responses of montane peatlands to climate change across different functional zones of the peat bog. UAS thermal mapping identified distinct land surface temperature variations across various vegetation categories under different conditions. Notably, ponds and waterlogged areas displayed a stabilizing effect on land surface temperature variability, though they exhibited different absolute temperatures. In contrast, shallow waterlogged areas exhibited surface temperatures akin to dry open peat areas. Multispectral UAS monitoring demonstrated significant transitions among the peat bog zones in response to heat and drought propagation. The most pronounced changes occurred in shallow waterlogged areas, which shrank notably from 22.8% to 4.5%, while bare peat expanded from 26.8% to 45.5% during the 2019 drought season. High-resolution thermal and multispectral monitoring has revealed the scope and magnitude of the intra-peatland responses to drought and heat waves and serves as a sensible indicator of environmental changes of peatlands. It has disclosed a large cumulative effect of change in an environment composed of highly heterogeneous and subtle structures. The results highlighted the effectiveness of UAS monitoring in understanding the extent of change in montane peatlands as a fragile environment exposed to the effects of climate change.