Author(s): Chloe Denham
Mentor(s): Sam St.Clair
Institution BYU
Aspen conifer forests are crucial habitats that support many different species and are important for maintaining biodiversity and forest health. Forest landscapes have experienced an increase in grazing pressure from elk, cattle, and deer that can reduce forest recruitment and regeneration. This study aims to quantify the impacts of chronic grazer herbivory on regenerating aspen-conifer forests and management approaches that can mitigate them. We applied three treatments to 34 plots across the Monroe Mountain in central Utah where grazing pressure is particularly high. Plots were either burned, mechanically thinned, or left untreated. Controlled burns were applied to reduce fuel loads and encourage regrowth, while mechanical thinning involved the removal of competing conifer species using logging machinery (a feller buncher attached to a large skid steer) to decrease canopy cover, creating conditions thought to favor aspen regeneration. Transect measurements were conducted across the plots, and included aspen density, herbivory rates, elk and deer pellet counts, and the recruitment of taller aspens (over 200 cm). We observed a significant reduction in aspen browsing in burned and mechanically thinned plots, suggesting reduced grazing pressure in treated areas. Additionally, sucker density declined over time, while the average aspen height increased across all plots. These results indicate that chronic herbivory significantly impacts aspen recruitment in aspen-conifer forests that can be overcome by large prescribed fires and mechanical treatments. There is evidence that the positive effects of treatments may be due to induction of secondary defense compounds, and fast growth that outpaced animal consumption of regenerating stems.