Effects of Advance Regeneration and Deadwood Retention on Forest Hydrometeorology after Disturbance

Climate change, including an increasing frequency and intensity of disturbances, is progressively threatening the resilience and productivity of forests. In the same time, the demand for ecosystem services provided by forests, such as carbon sequestration, water purification or habitat provision, is steadily increasing. To develop strategies to better cope with this pressure on forests, the LabForest project, funded by the German Federal Ministry of Research, Technology and Space (BMFTR), investigates the effectiveness and efficiency of silvicultural measures in relation with calamities within a living lab in a forest of the Ludwig-Maximilians-University in southern Germany.

Within the LabForest project, two replications of a two factorial experimental design are established on a 1 km² area. The first factor compares plots with and without advance regeneration (before the calamity), and the second factor compares the post calamity treatment with fully cleared sites versus sites, were all dead wood was gouged and kept on site. This setup includes eight 0.25 ha experimental plots equipped with an extensive measurement network to assess hydrometeorological differences between forest management strategies.

During the first growing season following the disturbance, microclimatic measurements reveal lower mean and maximum soil temperatures at -6 cm depth and reduced diurnal temperature amplitudes at uncleared and gouged compared to cleared sites. These differences diminish above the ground (+2 cm) and are negligible at +15 cm height. Advanced regeneration had a weaker influence on soil and near-ground temperatures than complete clearing. Furthermore, differences in soil moisture patterns and evapotranspiration rates were observed.

The improved understanding of hydrological and micrometeorological conditions associated with the investigated forest management strategies, enables recommendations for establishing economically and ecologically resilient forests to cope with the increasing pressure on forests by anticipated climatic changes and societal demands.