Recent Topics Posters
Huggins, Thomas , Prigge, Barry , Sharifi, Rasoul , Rundel, Philip .
Drought and decline in the critically endangered Lane Mountain milkvetch: host shrub and soil seed bank analyses
The Lane Mountain milkvetch, <em>Astragulas jaegerianus</em>Munz (LMMV), is a critically endangered plant that exists in small fragmented populations in the vicinity of the Army’s National Training Center, 40 miles north of Barstow, CA. The LMMV is a desert herbaceous perennial that grows within the canopy of host shrubs. In summer, the LMMV typically dies back to the root crown and becomes dormant to avoid water stress, resprouting after the onset of winter rains. Since monitoring began in 1999, this already rare plant has undergone alarming population contractions and a complete failure to recruit new individuals to monitored populations. These monitored populations have declined to less than 20% of their previous size, and some are in danger of local extinction. The decline of the LMMV has occurred simultaneously with severe drought conditions in the Mojave Desert that are predicted to continue for decades or longer. A previous laboratory study suggested that frequent, above average winter precipitation is important for seedling establishment and survival of the LMMV. Therefore, drought conditions in the Mojave are thought to have had a direct effect on LMMV mortality. This study investigates the extent to which declines in the LMMV may be explained by (1) the effect of drought on LMMV host shrubs and (2) the condition of the LMMV seed bank. Our results document a significant decline in shrub cover, and high host shrub mortality coincident with LMMV decreases and the on-going drought. Furthermore, our results suggest that LMMV population declines are exacerbated by low LMMV seed densities in the soil seed bank, and limited LMMV seed dispersal. Drought conditions may also contribute to low seed densities in the soil seed bank by negatively affecting LMMV seed production.
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1 - University of California Los Angeles, Ecology and Evolutionary Biology, 621 Young Drive South, Box 951606, Los Angeles, CA, 90095-1606, United States
2 - University of California Los Angeles, Herbarium, Mildred E. Mathias Botanical Garden, 621 Young Drive South, Box 951606, Los Angeles, CA, 90095-1606, United States
Presentation Type: Recent Topics Poster
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM