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Question from Sharon, Spokane, WA -

Is there anything known about the “tipping point” or ways to predict native trees decline due to drought stress? Most of our native trees and plants are drought tolerant, but in recent years we have had longer periods of no precipitation, high temperatures, big fire seasons, and have been seeing more symptoms of drought stress and other insect/disease problems combining to cause tree death. This is in native forests and rural situations (inland northwest- Montana, Idaho eastern Washington. Primarily ponderosa pine, but some other species like doug fir and cedar also).

Sharon

Answer from Dr. Mike Kuhns, USU Extension Forester and Professor (sent 11/29/17)-

Sharon,

There is a tipping point, but it would be different for each species or forest type and what you would measure to indicate whether this point has been reached would vary. If the trees are coniferous evergreens then the best indicator may be how many years worth of needles are on the tree. Severely stressed trees will often lose last year’s needles before the next growing season is over. Also stem (trunk) diameter growth is a good measure of stress. Slow growth is a sign of stress. Finally, susceptibility to insect attack is a good indicator of stress.