With the mission to develop climate-resilient forest management techniques, this is how the WAIKLIM project is shaping up in its second year.

Foresters around the world face the challenge of securing forest ecosystems’ future in a rapidly changing environment. “Waldbau im Klimawandel” (WAIKLIM) is a collaborative project funded by the Waldklimafonds, involving four TU Dresden Chairs: Silviculture (Prof. Sven Wagner, Project Head, and Dr. Katja Skibbe, Project Coordinator), Soil Resources and Land Use (Prof. Karsten Kalbitz), Forest Sites and Hydrology (Prof. Natalie Orlowski), and Biodiversity and Nature Conservation (Prof. Goddert von Oheimb).

WAIKLIM aims to determine the optimal intensity and spatial arrangement of interventions in mature tree stands to enable successful rejuvenation while maintaining storm-resistant old stands. The project seeks to answer a critical question: How do saplings manage to grow into healthy trees despite climate-induced stress from heat and drought? Researchers are examining how different levels of canopy cover affect local water availability, the growth of young trees, and the vulnerability of mature stands to storm damage, which is likely to increase due to climate change.

To evaluate the different aspects of the project, a total of 14 sites across Saxony with different forest compositions were selected: three pine stands, five pre-forests, and six beech stands. To create different levels of canopy cover, thinning of 20-30% was carried out in the pine and beech stands. For the pre-forests, subplots were created that represent a gradient of canopy cover, ranging from less than 30% to subplots with 80% cover.

How can current tree stands be converted into climate change-resilient forest stands?

Increasing droughts, heat waves, extreme rainfall, and storm risks are expected to increase through climate change. This has led to uncertainty about suitable tree species selection and silvicultural methods for forest regeneration. WAIKLIM studies ecologically and economically valuable tree species that could adapt to stress conditions. We therefore created an “artificial” regeneration with rejuvenation plants of fast-growing forest species (beech and silver fir) and intermediate tree species (oak and Douglas-fir) in the thinning gaps to monitor their regrowth and adaptation ability to different environmental conditions (thinning, water availability, micro-climate etc.)

The successful establishment of the saplings will be measured and documented in high resolution with terrestrial laser scanners (TLS) and hemispherical photos. This will be the first time that a large number of features, such as the exact position, diameter at breast height (DBH), height, crown volume, and canopy, will be precisely determined in a wide range of forest stands across Saxony.

Measurement setup

This summer, the main tasks of the project cantered around the instrumentation of the stands to allow site-specific measurements of the water balance. Each study site will have weather stations with automated remote data transfer, energy self-sufficient solar panels, and a multi-sensor that combines measurements of factors such as precipitation, solar radiation, and wind direction and intensity, among others.

To obtain below-canopy precipitation values at sites with higher canopy density, throughfall samplers and rain gauge sensors using the tipping bucket principle will be implemented. For soil hydrological measurements, each stand will be equipped with around 100 high-precision time-domain- transmission (TDT) sensors with remote transfer of data of soil moisture, temperature, and soil matric potential. Both the sensors and the weather stations use the Internet of Things (IoT) technology, enabling real-time monitoring.

This unique measurement setup will enable a detailed site characterization and high-resolution spatial data about tree stand water dynamics across Saxony. These efforts are crucial for understanding how varying degrees of canopy clearing affect local water supply and the growth of young trees, providing insights into developing effective climate-adaptive forest management strategies.

We look forward to sharing further developments as the project progresses. For more information about the WAIKLIM project, please visit our website.