Impact of forest disturbance derived from Sentinel-2 time series on Landsat 8/9 land surface temperature: The case of Norway spruce in Central Germany
Simon Grieger, Martin Kappas, Susanne Karel, Philipp Koal, Tatjana Koukal, Markus Löw, Martin Zwanzig, Birgitta Putzenlechner
Abstract
Forest cover and vitality loss is a global phenomenon. Areas of Norway spruce ( Picea abies (L.) Karst.) in Central Germany were affected by widespread vitality and canopy cover loss in the years from 2018 due to drought stress and pest infestation. Such disturbances can favor higher land surface temperature (LST) on cloudless summer days. Regional assessment of LST in disturbed forest stands is challenging due to the spatial and temporal resolution of available products and various influences on the surface energy budget. To assess the effects of forest disturbance and topographic and pedological site factors on LST, a time series of the Landsat 8/9 Surface Temperature product was combined with a Sentinel-2-based forest disturbance monitoring framework. Results from three regions in Central Germany indicate a trend of elevated LST in disturbed areas of Norway spruce (median of LST differences of 4.4 K compared to undisturbed areas). Among topographic site factors, elevation exhibits the highest influence (median of LST differences between disturbed and undisturbed areas 1.2 K higher for highest areas compared to lowest). For pedological site factors, substrate shows the highest effect, modulating the median of LST differences by 2.9 K. Forest disturbance is accompanied by increased LST variance, possibly caused by different post-disturbance forest management practices. Air temperature at 15 cm shows highest agreement with LST and supports variation among management types. Identification of sites with a high risk of elevated LST is crucial for decision making in post-disturbance forest management, successful reforestation, and establishment of resilient forests. • Landsat 8/9 land surface temperature reveals effect of forest disturbances. • Topographic and pedological site factors modulate land surface temperature. • Disturbance effect in similar geographical settings totals 4.4 K. • Land surface temperature dynamics are linked to in situ microclimate. • Post-disturbance management modifies in situ land surface temperature and microclimate.