KROOF 3: Legacy Effects and Limits of Drought Tolerance in Beech/Spruce Stands

Impact of repeated drought and drought stress recovery on pure and mixed stands of beech and spruce

The "Kranzberg Forest Roof Project" (KROOF) has been funded by the DFG since 2013 as part of a series of individual proposals. The expertise of the participating research groups spans forest growth and yield science, ecophysiology, and rhizosphere biology. The University of Innsbruck is involved through the Weave program.

In the first funding period (KROOF 1), a throughfall exclusion experiment was initiated with approximately 100 trees in a mature beech-spruce forest in southern Germany. This experiment studied the effects of repeated summer drought on trees and their ectomycorrhizal associations. In addition, long-term drought adaptation was studied across five sites along a precipitation gradient. In the second phase (KROOF 2), the focus shifted to stand recovery processes.

For the third funding period (KROOF 3), the drought pre-treatment will be followed by a renewed, potentially lethal drought. The goal is to determine whether trees acclimated during the previous drought periods, making them less vulnerable, or whether they suffered pre-damage, which could cause them to reach their drought tolerance limits earlier and suffer lethal consequences.

The project focuses on three main hypotheses:

• "Mixing" hypothesis: Mixed stands benefit from structural heterogeneity and asynchronous resource use under drought conditions more than monospecific stands.
• "Weakest link" hypothesis: Acclimations to water shortage are overridden under extreme drought by the failure of the weakest link in the soil-plant-atmosphere continuum.
• "Legacy" hypothesis: Tree-soil systems with a history of drought cope better with renewed drought than those experiencing severe drought for the first time.

This research will analyze the multifaceted responses of pure and mixed stands of beech and spruce to repeated drought events, utilizing data from KROOF 1 and KROOF 2, complemented by new measurements. Empirical results will be integrated into the BALANCE tree growth model, allowing for precise simulations at multiple spatial and temporal scales. The results will contribute to understanding the dynamic interactions between forests and changing environmental conditions, with implications for sustainable forest management.

Relevant links

Duration

Funding

Partners

Contact