RMBL principal investigator Benjamin Wong Blonder, PhD, studies how quaking aspens (Populus tremuloides) respond to stress across the high country. This summer’s drought and heat, he writes, are the latest chapter in a longer story: aspen decline that builds slowly, over years of accumulated stress, rather than arriving all at once. Below, he explains what watching the same aspens for over a decade has taught him, and why a single hot, dry summer is easy to notice but hard to fully understand without years of watching what came before.

I’ve been working with quaking aspens in the Gothic area since 2010. This year I took the bus to and from Denver, and had a chance to see trees across the state, in addition to those near Gothic. This summer’s dry and hot weather has not been kind to the aspens anywhere. At lower elevations, I saw many trees with thin-looking canopies, with canopies wholly absent, or with large fungal cankers on their stems.

What I saw this year is probably the consequence of several prior years of challenging conditions. If the climates of the past few years become the new normal, many areas of aspen habitat are going to become increasingly more marginal. The acute stress of this year will actually not play out fully for several years to come. This future is already partially written.

For more on the science behind this, see:

‘Climate lags and genetics determine phenology in quaking aspen (Populus tremuloides),’ Blonder et al., 2023, New Phytologist. Read the paper →
and
‘Cytotype and Genotype Predict Mortality and Recruitment in Colorado Quaking Aspen,’ Blonder et al., 2021, Ecological Applications. Read the paper →