BayCEER Workshop 2020

Drought impacts on Central European forest: the remote sensing perspective

O 2.3 in Session 2: Tracing Changes in Space and Time

29.10.2020, 11:30-11:45, online via Zoom

Drought episodes are predicted to increase their intensity and frequency in Central Europe, which will have a particular impact on forest vitality, productivity, and species distribution. In addition, changes in drought response may change with tree ontogeny. The impact of tree species interaction on forest vulnerability to drought is limited. The aim of this study is to find out how deciduous saplings and mature trees reacted to the severe drought of 2018 and whether tree species diversity buffers the impact of drought stress on saplings. Based on field measurement of crown transparency, species richness, and the Sentinel-2 normalized difference vegetation index (NDVI) for mature trees, the vulnerability, and recovery from drought and the species interaction were analyzed. Fieldwork was carried out in Central Eastern Germany in 2018 during the vegetation season and repeated in 2019 and 2020.

Preliminary results show: (1) 65% of the recorded saplings species experienced defoliation during the drought episode of 2018, with Fagus sylvatica L. and Betula pendula Roth. saplings being less affected (< 55%) than Carpinus betulus L., Sorbus aucuparia L. and, Frangula alnus Mill. (≥ 85%); (2) C. betulus and S. aucuparia recovered faster than F. sylvatica, B. pendula, Quercus spp. and Crataegus spp., F. alnus, Sambucus nigra L., Acer platanoides L. and, Corylus avellana L., species (p < 0.001); (3) The NDVI for the mature tree species showed a significant decrease in 2018 compared to 2015 and a strong correlation with the groundwater. Our results suggest that although there was less precipitation in 2018 than in 2003, F. sylvatica saplings seem to be capable of withstanding and surviving extreme drought, however they may face a slow recovery. Saplings and mature trees exhibited a different response to drought stress, which is essential to consider for implementing adaptive forest management strategies to mitigate the impact of climate change.

Keywords: precipitation; broadleaf forests; tree vitality; drought stress; European beech saplings; climate change

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