Variation in stem hydraulic capacitance in two Eucalyptus pauciflora subspecies across an elevational gradient Stem hydraulic capacitance and elevation in Eucalyptus pauciflora

Abstract

Vegetation dieback is a concerning environmental phenomenon whose frequency appears to be increasing globally. The rate of dieback has recently intensified throughout subalpine snow gum woodlands in Kosciuszko National Park for reasons that are not well understood. There is a lack of research focused on the changes in stand hydraulics across elevation and how this may influence snow-gum susceptibility to woodborer-associated dieback. This study examined the relationship between stem hydraulic capacitance and elevation in two subspecies of Eucalyptus pauciflora (Sieber ex Spreng.) which appear to be differentially affected by dieback: Eucalyptus pauciflora subspecies niphophila (Maiden and Blakely) and Eucalyptus pauciflora subspecies pauciflora (Sieber ex Spreng.). Stem hydraulic capacitance and saturated water content was measured in 100 trees, ten from each of ten sites evenly spaced across a 1,000m elevation gradient. Across subspecies, we observed a significant decrease in stem hydraulic capacitance with elevation. The response of stem hydraulic capacitance to elevational change was species-specific. Further research should focus on other drought traits across snow gum subspecies and elevation to create a broader understanding of stand hydraulics and other physiological traits influencing woodborer-associated dieback susceptibility.