Water potentials comparison of healthy versus drought-induced dieback-affected Populus tremuloides

Predawn and midday plant water potential measurements, collected on terminal twigs using a scholander-type pressure chamber (PMS Instruments, Corvallis, OR, USA). Measurements were collected in five trembling aspen (Populus tremuloides) clones, from three canopy dominant or co-dominant ramets in an intact portion of the clone (<20% tree-level mortality, 'Control' treatment), as well as three ramets in a portion of the clone experiencing high drought-induced mortality (>80% of ramets dead, 'Dying' treatment). Water potential measurements were also collected for understory shrub Symphiocarpus albus in the Control and Dying treatments. Data are formatted in the PSINet data submission template. Measurments were collected in mid June, mid July and mid August of 2011, in the San Juan National Forest in southwestern Colorado, USA. Other physiological measurements made in these locations are described in Anderegg WRL, Berry JA, Smith DD, Sperry JS, Anderegg LDL, Field CB. 2012. The roles of hydraulic and carbon stress in a widespread climate-induced forest die-off. Proceedings of the National Academy of Sciences 109: 233–237.