
Tree rings help researchers understand drought intolerance
Dec. 26 (UPI) -- Tree rings are giving scientists answers for how fire suppression has increased forest density and reduced their tolerances for droughts and wildfires, a study says. Researchers at Oregon State University and Utah State University analyzed 2,800 hectares of mixed-conifer forest in central Oregon. Some of the ponderosa pines have inhabited the study area since before 1910 -- that's around the time when putting out forest fires became federal law. "We wanted to document the trajectory of sensitivity to drought stress in response to progressively increasing fire deficits, and the threshold level of stand occupancy where decreasing resistance and resilience to drought stress, bark beetles and wildfire set in," Christopher Still, a researcher at OSU College of Forestry and stu...