Long-term aspen dynamics, trophic cascades, and climate in northern Yellowstone National Park

A significant recovery of quaking aspen (Populus tremuloides) in northern Yellowstone National Park, driven by reduced ungulate herbivory and a re-established trophic cascade, has been documented. The study found that aspen recruitment increased over 60-fold within 25 years after exclosure construction, despite a drying climatic trend since 1940, indicating that long-term aspen decline was primarily caused by high levels of elk (Cervus elaphus) herbivory rather than climate change. Following the reintroduction of gray wolves (Canis lupus) in 1995–1996, aspen density and height surged from 1997 to 2012, coinciding with high predator-prey ratios, declining elk numbers, and decreased browsing rates. This recovery supports the hypothesis that trophic cascades play a crucial role in ecosystem dynamics.

Beschta, R. L., Painter, L. E., Levi, T., & Ripple, W. J. (2016). Long-term aspen dynamics, trophic cascades, and climate in northern Yellowstone National Park. Canadian Journal of Forest Research, 46(4), 548–556. https://doi.org/10.1139/cjfr-2015-0301