Trees on the Appalachian Ridge (IMAGE) Penn State Caption With an analysis of a global dataset of tree tissue, a team led by Penn State researchers demonstrated that the rate of photorespiration in trees is up to two times higher in warmer climates, especially when water is limited. They found the threshold for this response in subtropical climates, like this portion of the Appalachian Ridge and Valley Region, begins to be crossed when average daytime temperatures exceed roughly 68 degrees Fahrenheit and worsens as temperatures rise further. Credit Warren Reed/Penn State Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. No derivatives or adaptations of the work are permitted. License CC BY-NC-ND Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.