Studies such as this are important, the scientists said, to better understand how forests might respond to a warmer or drier climate of the future. And although this might imply that these conifers could be more resistant to drought than had been anticipated, the researchers said it's not that simple.
"If the climate warms, we might actually get more of these winter cycles of freezing and thawing," McCulloh said. "There's a lot of variability in the effects of climate we still don't understand.
"One of the most amazing things these trees can do is recover from these declines in conductivity by replacing the air bubbles with water," she said. "We don't understand how they do that at the significant tensions that exist at those heights. We're talking about negative pressures or tensions roughly three times the magnitude of what you put in your car tires."
When the field research on this study was done in 2009, the area actually experienced a historic heat wave during August when temperatures in the Willamette Valley hit 108 degrees. During such extreme heat, trees experienced some loss of hydraulic conductivity but largely recovered even before rains came in September. By contrast, greater loss of hydraulic conductivity was observed in the middle of winter.
The study was done at the Wind River Canopy Crane Research Facility, and published in the American Journal of Botany. The research was supported by the National Science Foundation.
"The commonly held view is that the summer months of the Pacific Northwest are extremely stressful to plants," the researchers wrote in their conclusion.
"Yet, our results indicated that the winter months are more stressful in terms of hydraulic function, and suggest that perhaps an inability to recover from increase in native
|Contact: Kate McCulloh|
Oregon State University