PARENT SESSION
Oral Session # 45: Plant Ecology III: Plant - Water Relations I.
Presiding: R Giuliani
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 200.
Willow persistence in Yellowstone National Park: Interacting effects of hydrology and herbivory.
Bilyeu, Danielle*,1, Singer, Francis1, 2, Hobbs, N. Thompson1, Cooper, David3, 1 Natural Resource Ecology Laboratory, Fort Collins, CO, USA2 Earth Resources, Fort Collins, CO3 Biological Resources Division, Fort Collins, CO
ABSTRACT- Willows (Salix spp.) in the ungulate winter range of Yellowstone National Park (YNP) have undergone a well-documented decline in height, distribution, and recruitment over at least the past 70 years. The decline has coincided with both an increase in ungulate populations and a decrease in water tables, due to declines in beaver populations and/or a trend towards a drier, warmer climate. We constructed an experiment with two treatments, exclosing (to prevent herbivory by ungulates) and artificial damming (to raise water tables), in order to examine the effects of herbivory and water table on the growth of S. geyeriana, S. boothii, and S. bebbiana (n=4). The first year of post-treatment data suggests that damming had a positive effect on current annual growth for S. geyeriana, although exclosing had a negative effect for both S. geyeriana and S. bebbiana. However, seed production was much higher inside of exclosures, suggesting that browsed plants allocate more resources to growth and less to reproduction relative to unbrowsed plants. Furthermore, increased water availability may also stimulate growth in browsed plants.
Key words: Yellowstone, herbivory, Salix, hydrology