Remote sensing and micrometeorological monitoring of disturbed and reforested areas in Central Germany
Test Sites Southern Harz
BackgroundThe last years with their hot, dry summers (2018-2020) in combination with pests have left visible traces in local forests. Particularly in spruce stands, there has been and continues to be widespread dieback - leaving behind "Dürrständer" (Fig. 1) and increasingly "bare" forest areas such as in the Harz Mountains (Fig. 2). In view of progressive climate change and the associated increasing probability of drought but also heavy rainfall events, the question arises - what's next?
Figure 1: Bare areas and disturbed spruce stand in the southern Harz Mountains
From an ecological perspective, disturbed areas generally represent an opportunity for biodiversity and natural reforestation, especially when deadwood is left in place. However, there are multiple services of the forest ecosystem to our society: among other things, economic livelihood, renewable resource, flood and erosion control, and recreational space are also important forest functions. This tension raises questions that cannot be answered in a blanket manner, such as: What is the "benefit" of dead spruce stands? Should degraded areas be actively reforested or left untreated? Will native tree species cope with future climatic changes?
The silvicultural options for reforestation of developed damaged areas are manifold and are intensively discussed not only within forest science and forestry. There is an urgent need for interdisciplinary approaches that understand the forest as part of the landscape. As such, integrated research contributes to evidence-based discussions and solutions.
Figure 2: Dead spruce stands can be seen from the observation tower of the Poppenberg in the southern Harz Mountains (June 2021).
The research and activities of the research group include, among others:
- Drone surveys in the optical and thermal spectral range.
- Taking hemispherical photos to derive biophysical parameters (leaf area index/LAI, fraction of photosynthetically active radiation/FAPAR, percent canopy cover/FCOVER)
- Continuous monitoring of the microclimate (temperature below, at and above the soil surface, soil moisture)
- Multitemporal satellite image analysis (Sentinel-2, Landsat-8, Sentinel-3, MODIS)
- Supervision of bachelor and master theses
Figure 3: Monitoring of disturbed areas and reforestation measures. Top: drone flight with recordings in the optical and thermal spectral range, Middle: Derivation of biophysical parameters using digital hemispherical photography, Bottom: continuous monitoring of the microclimate on different plots.