Ramp Neale, Jennifer M. , Deprenger-Levin, Michelle , Dawson, Carol , Grant III, Thomas A. .
Fencing populations of a rare native plant (Astragalus microcymbus) lead to increased reproduction but donít tell the whole story, how can management save this species from extinction?
Astragalus microcymbus Barneby (Fabaceae) is a rare species endemic to Gunnison County, Colorado. Since 1995, Denver Botanic Gardens and the Bureau of Land Management (Colorado State Office) have monitored four populations of this sensitive species in the South Beaver Creek drainage. Large, statistically significant population declines have been documented. The demographic study has documented prolonged dormancy, episodic fruit production, and variable levels of leaf and inflorescence herbivory. While this species is naturally rare, appropriate management techniques are needed to ensure its long-term survival. Many plants were observed to have a majority of stems sheared off near the base due to mammal herbivory, which prevents flowering and subsequent seed set. Therefore, a mammal exclusion experiment was installed in the springs of 2006 and 2007 to determine if reproduction would increase in the absence of small mammals. Data analyzed after fencing was installed indicate significantly less browsing in plots with fencing with an average 17.8% of the plants browsed in fenced plots and 45.5% browsed in unfenced plots. Mammal exclosures have resulted in significantly greater fruit production and an increase in average plant length in fenced sites. Despite detecting increases in plant growth and reproduction, the fit of the relationship between herbivory and fruit production is low indicating that there are confounding factors. We have detected a significant correlation between reproduction and precipitation indicating it may be essential for the longevity of these populations along with the exclusion of mammal herbivores. This long-term demographic study will continue while we analyze potential management techniques in order prevent the extirpation of these populations.
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1 - Denver Botanic Gardens, Research & Conservation, 909 York Street, Denver, CO, 80206, USA
2 - U.S. Bureau of Land Management (BLM) - Colorado State Office, 2850 Youngfield Street, Lakewood, CO, 80215, USA
3 - Colorado State University, Graduate Degree Program in Ecology, Fort Collins, CO, 80523, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Wasatch A/Cliff Lodge - Level C
Date: Wednesday, July 29th, 2009
Time: 8:30 AM