Xylem anatomy and branch embolism resistance of Sumatran rainforest trees

Several studies have reported accelerated tree mortality in tropical moist as well as dry forests in response to severe drought periods in the past. Although it still remains unclear how tropical trees will respond to increased drought frequency as predicted by several climate change scenarios, it is safe to conclude that drought will cause major shifts in community composition and ecosystem functioning in tropical forests in the future. The mechanisms leading to drought-induced mortality in trees are far from being understood, but it appears that large and tall tropical trees are carrying a disproportionally higher risk for drought-induced tree mortality than smaller and understory trees, both in seasonally-dry and in perhumid tropical environments. Tropical trees with light wood seem also to be at greater risk of drought-induced die-back, but the related findings are less consistent. Both tree height and wood density are thus thought to be key functional traits influencing growth and survival, but they have rarely been studied in adult tropical trees in combination with hydraulic measurements. To fill this gap, twelve forest tree species from the Harapan region representing a gradient in wood density and tree height at maturity will be analysed for their branch hydraulic properties including xylem safety.