Speaker
Description
Droughts increasingly affect the functioning of forests worldwide and compromise their capacity to mitigate climate change. Over the past decade, forests in central Europe have experienced unprecedented sequences of consecutive drought years, resulting in widespread tree mortality and substantial economic and ecological losses. In our study, we examine tree physiological responses to a series of consecutive drought episodes during the last decade, based on carbon isotope composition (δ¹³C, ‰) of leaves across the vertical canopy of trees.
In a temperate broadleaved forest in central Europe (Hohes Holz, ICOS site DE-HoH), we annually collected leaves from twigs of comparable ages between 2015 and 2024, across the whole tree canopies of dominant species at the site (Fagus sylvatica and Quercus petraea). Bulk leaf material was assessed for δ¹³C, which provides an integrated record of the ratio of intercellular to atmospheric CO2 concentrations during the period when the carbon was fixed. As such δ¹³C can be used as physiological indicator of a tree’s water status and drought stress. We present how changes in δ¹³C across tree canopies are related to meteorological and hydrological indicators, spectral measures, and leaf functional traits measured at the forest site over the last decade.
Our dataset confirms pronounced vertical δ¹³C gradients within tree canopies, and significant increases in leaf δ¹³C with declining soil water availability. More remarkably, we observe that the difference in δ¹³C between upper and lower tree canopy layers (Δδ¹³C) consistently attenuates from wetter to drier years (P<0.05). This pattern arises because the δ¹³C values of leaves in the lower canopy increase more
rapidly (i.e. become less negative) than those of upper-canopy leaves. Linear mixed-effects model outcomes confirm that the attenuation of leaf Δδ¹³C across tree canopies is primarily explained by reductions in soil moisture, with additional variation explained by leaf functional traits. Collectively, our results suggest that drought induces a homogenization of reduced stomatal aperture across the canopies of the studied tree species, enhancing our understanding of tree functional responses to
drought.
| Status Group | Senior Scientist |
|---|---|
| FOR TALKS: Poster Presentation Option | Yes, I’m willing to present as a poster. |