The role of isotopes in precipitation in assessing the impact of climate change on forest mortality

In times of climate change, when drinking water resources and the water needed for the survival of groundwater-dependent ecosystems, such as lowland forests depend on the availability of water, the sustainable use of groundwater requires strategic planning based on an assessment of the amount of groundwater available. To properly assess and plan the amount of available and accessible water resources, it is first necessary to understand the processes of the water cycle.

About 25 years ago (in 2000), a high mortality rate was observed in the groundwater-dependent ecosystem (GDE) of several lowland oak forests in Slovenia and Europe. Understanding the processes of the hydrological cycle is becoming increasingly important, mainly because of the high mortality of these forests, whose main problem is probably the lowering of the groundwater table and the reduced accessibility of water to these trees as a result of changes in weather patterns or the regime and amount of precipitation recharging the aquifers in the area of these forests.

By short-term monitoring of the composition of stable water isotopes (δ¹⁸O and δ²H) in precipitation in the area of lowland oak forests Murska šuma (northeast Slovenia) and Krakovski gozd (southeast Slovenia), we have obtained important results on the variability of the precipitation signal, which will be compared with the results of the neighbouring long-term stations (e.g. Murska Sobota, Ljubljana, Vienna, Graz and Zagreb). In the future, we will expand our research and also monitor the isotope signal of stable water isotopes in soil, groundwater and xylem water of adult trees. This will allow us to assess the origin of water sources used by trees and to identify physiological responses to changing climatic conditions such as drought stress or altered precipitation regimes. By integrating water isotope data into ecological and hydrological models, we can better predict how trees will respond to current and future climate change, providing information for conservation strategies and sustainable management practices.

Activities for this presentation were funded in last decade by the Slovenian Research Agency (Grants P1-0143, N1-0054, N1-0309 and P1-0020), IAEA (CRP F31006, TC RER7013, TC RER7017, SLO7001) and projects Mladi forum and FREYA which are co-funded by the Slovenian Research and Innovation Agency within the framework of Developmental funding pillar.