Intensive leaf cooling promotes tree survival during a record heatwave.

Increasing heatwaves are threatening forest ecosystems globally. Leaf thermal regulation and tolerance are important for plant survival during heatwaves, though the interaction between these processes and water availability is unclear. Genotypes of the widely distributed foundation tree species were studied in a controlled common garden during a record summer heatwave-where air temperature exceeded 48 °C.

Limits of thermal and hydrological tolerance in a foundation tree species (Populus fremontii) in the desert southwestern United States.

Populus fremontii is among the most dominant, and ecologically important riparian tree species in the western United States and can thrive in hyper-arid riparian corridors. Yet, P. fremontii forests have rapidly declined over the last decade, particularly in places where temperatures sometimes exceed 50°C.

Tradeoffs between leaf cooling and hydraulic safety in a dominant arid land riparian tree species.

Leaf carbon gain optimization in hot environments requires balancing leaf thermoregulation with avoiding excessive water loss via transpiration and hydraulic failure. The tradeoffs between leaf thermoregulation and transpirational water loss can determine the ecological consequences of heat waves that are increasing in frequency and intensity. We evaluated leaf thermoregulation strategies in warm- (>40°C maximum summer temperature) and cool-adapted (<40°C maximum summer temperature) genotypes of the foundation tree species, Populus fremontii, using a common garden near the mid-elevational point of its distribution.

Episodic defoliation rapidly reduces starch but not soluble sugars in an invasive shrub, Tamarix spp.

Premise: Plants rely on pools of internal nonstructural carbohydrates (NSCs: soluble sugars plus starch) to support metabolism, growth, and regrowth of tissues damaged from disturbance such as foliage herbivory. However, impacts of foliage herbivory on the quantity and composition of NSC pools in long-lived woody plants are currently unclear. We implemented a controlled defoliation experiment on mature Tamarix spp.

Adaptive capacity in the foundation tree species : implications for resilience to climate change and non-native species invasion in the American Southwest.

(Fremont cottonwood) is recognized as one of the most important foundation tree species in the southwestern USA and northern Mexico because of its ability to structure communities across multiple trophic levels, drive ecosystem processes and influence biodiversity via genetic-based functional trait variation. However, the areal extent of cover has declined dramatically over the last century due to the effects of surface water diversions, non-native species invasions and more recently climate change. Consequently, gallery forests are considered amongst the most threatened forest types in North America.

Variation in woody plant mortality and dieback from severe drought among soils, plant groups, and species within a northern Arizona ecotone.

Vegetation change from drought-induced mortality can alter ecosystem community structure, biodiversity, and services. Although drought-induced mortality of woody plants has increased globally with recent warming, influences of soil type, tree and shrub groups, and species are poorly understood. Following the severe 2002 drought in northern Arizona, we surveyed woody plant mortality and canopy dieback of live trees and shrubs at the forest-woodland ecotone on soils derived from three soil parent materials (cinder, flow basalt, sedimentary) that differed in texture and rockiness.

Influence of soil texture on hydraulic properties and water relations of a dominant warm-desert phreatophyte.

We investigated hydraulic constraints on water uptake by velvet mesquite (Prosopis velutina Woot.) at a site with sandy-loam soil and at a site with loamy-clay soil in southeastern Arizona, USA. We predicted that trees on sandy-loam soil have less negative xylem and soil water potentials during drought and a lower resistance to xylem cavitation, and reach E(crit) (the maximum steady-state transpiration rate without hydraulic failure) at higher soil water potentials than trees on loamy-clay soil.

Six-year follow-up of the first Waterloo school smoking prevention trial.

This paper reports six-year follow-up data from the first large-scale randomized trial of the social influences approach to smoking prevention. In 1979, 22 schools were randomly assigned to program or control conditions. Students in program schools received a social influences curriculum in six core and two maintenance sessions in grade 6, two booster sessions in grade 7, and one booster session in grade 8.

Relation between severity of chronic illness and adjustment in children and adolescents with sickle cell disease.

Tested the relationship between illness severity and adjustment in 70 sickle cell patients, aged 8-16. Illness severity was measured by frequency of hospitalization and emergency room visits, frequency and intensity of pain crises, and duration of illness. Adjustment variables were IQ, self-esteem, social and personal adjustment, behavioral problems, school performance, and peer relations.

Coronary artery to left atrium fistula requiring revascularisation: case report and literature review.

Only 12 cases of coronary artery to left atrium fistula have been reported, with successful correction in at least seven. We describe a unique case of repair of a left main coronary artery to left atrium fistula using revascularisation with general discussion of the embryology, pathophysiology, complications, and diagnosis of these fistulae, indications for operation, and guidelines for surgical management.