Decoupling occurs under extreme heat

Our study had a glasshouse and a field component. The glasshouse study provided the opportunity to better control water availability, while the field study provided observations of tall trees in the field. The glasshouse experiment examined responses to a five-day heatwave under controlled conditions, with a direct comparison of well-watered and droughted conditions using a gradual, moderate drought stress. Four treatments include: C, control; D, drought; C+HW, control + heatwave; D+HW, drought + heatwave. In the field, we took advantage of naturally-occurring extreme heatwaves to compare in situ responses of urban trees in Sydney, Australia during the hottest and driest year on record (2019). We investigated if there is evidence for decoupling of stomatal conductance (gs) from net photosynthesis (Anet) in 26 different broadleaf tree or shrub species (n=4-8 trees per species) by measuring leaf gas exchange on hot days (maximum air temperature >40 °C). For more details, see associated publication in Global Change Biology (link below).