| Stable isotope data obtained from archived and freshly collected spruce annual rings from the Austrian Forest Inventory (ANFI) and from selected \“problem areas\” provide us with the basis to identify the susceptibility of spruce stands to drought and subsequently to bark beetle infestation (Ips typographus). The focus of this project is, on the one hand, to determine climate-induced changes in spruce physiology (using stable isotope analysis in annual rings (> 60 years) from samples of suitable ANFI and soil inventory sites) and, on the other hand, to assess forest susceptibility to bark beetle infestation using the isotopic signature of archived and newly collected cores from across Austria. The stable-isotope data will be used i) to determine if and how drought stress has affected infestations in the past, and ii) to predict how stands will respond under future climate change scenarios. Tree physiological response data will be combined with site-specific forest and soil property data available from the ANFI and the Austrian Forest Soil Inventory to test the relationship between soil water status, vapor pressure deficit, and isotopic chronologies. Translation of isotopic results into drought susceptibility information by closely examining intrinsic water use efficiency, stomatal conductance, temporal water use balance, and photosynthetic capacity will serve as the basis for creating drought susceptibility maps. |