Complex interactions shaping aspen dynamics in the Greater Yellowstone Ecosystem

Research has not isolated the effect of elk herbivory on aspen from other factors including temperature, moisture, snow pack, bovid herbivory, and conifer competition.

“To date, however, there is an absence of research capable of isolating the effect of elk herbivory from other factors that may influence aspen, including temperature (Brown et al. 2006), moisture (Romme et al. 1995), snow pack (Brodie et al. 2012), bovid herbivory (Kimble et al. 2011, Beschta & Ripple 2014), and competition with conifers (Bartos 2001).”

Localized aspen recovery in the presence of relatively high elk density might be evidence of a behaviorally mediated trophic cascade, but spatial heterogeneity in aspen demography may not by itself be convincing evidence for such a cascade because aspen demography is spatially heterogeneous even when risk-sensitive foraging by elk is not implicated.

“Localized recovery of aspen in the presence of relatively high elk density might be evidence of a behaviorally mediated trophic cascade (BMTC) (e.g., Beschta & Ripple 2012, 2013).However, spatial heterogeneity in aspen demography may not be, by itself, convincing evidence for a BMTC because aspen demography is spatially heterogeneous even when risk-sensitive foraging by elk is not implicated (e.g.”