Whole-tree chambers for elevated atmospheric CO<inf>2</inf>experimentation and tree scale flux measurements in south-eastern Australia: The Hawkesbury Forest Experiment
- Publication Type:
- Journal Article
- Agricultural and Forest Meteorology, 2010, 150 (7-8), pp. 941 - 951
- Issue Date:
Resolving ecophysiological processes in elevated atmospheric CO2(Ca) at scales larger than single leaves poses significant challenges. Here, we describe a field-based experimental system designed to grow trees up to 9m tall in elevated Cawith the capacity to control air temperature and simultaneously measure whole-tree gas exchange. In western Sydney, Australia, we established the Hawkesbury Forest Experiment (HFE) where we built whole-tree chambers (WTC) to measure whole-tree CO2and water fluxes of an evergreen broadleaf tree, Eucalyptus saligna. A single E. saligna tree was grown from seedling to small tree within each of 12 WTCs; six WTCs were maintained at ambient Caand six WTCs were maintained at elevated Ca, targeted at ambient Ca+240μmolmol-1. All 12 WTCs were controlled to track ambient outside air temperature (Tair) and air water vapour deficit (Dair). During the experimental period, Tair, Dairand Cain the WTCs were within 0.5°C, 0.3kPa, and 15μmolmol-1of the set-points for 90% of the time, respectively. Diurnal responses of whole-tree CO2and water vapour fluxes are analysed, demonstrating the ability of the tree chamber system to measure rapid environmental responses of these fluxes of entire trees. The light response of CO2uptake for entire trees showed a clear diurnal hysteresis, attributed to stomatal closure at high Dair. Tree scale CO2fluxes confirm the hypothesised deleterious effect of chilling night-time temperatures on whole-tree carbon gain in this subtropical Eucalyptus. The whole-tree chamber flux data add an invaluable scale to measurements in both ambient and elevated Caand allow us to elucidate the mechanisms driving tree productivity responses to elevated Cain interaction with water availability and temperature. © 2010 Elsevier B.V.
Please use this identifier to cite or link to this item: