Abstract Detail



Conservation Biology

Meyer, Susan [1], Rominger, Kody [2], Schultz, Bettina [3].

Establishment of Holmgren’s Milkvetch (Astragalus holmgreniorum) from Seed.

Holmgren’s milkvetch (Astragalus holmgreniorum) is a federally listed endangered plant with a restricted edaphic and geographic range at the northeastern edge of the Mojave Desert. It is a short-lived perennial spring ephemeral that relies on high seed production, a long-lived seed bank, and regular recruitment from seed for population persistence in the highly stochastic desert environment. The seeds are physically dormant and can persist in the soil for at least 10 years, but scarified seeds germinate quickly after short chilling. Seedling emergence in natural populations takes place after adequate winter-spring rainfall from mid-January through March. Survival of emerged seedlings through the end of spring in a 2-year field observational study averaged 72%. In a long-term demographic study, recruited seedling density varied from 0 in dry-winter years to 0.31recruits-m-2 in a favorable rainfall year. Successful second-year return from dormancy in this long-term study averaged 16% and ranged from 0 to 44.6%, mostly as a function of second-year winter precipitation. We planted scarified seeds in a small plot study in mid-December 2016. Seeding emergence started in mid-January and was generally high but differed between sites (67% at Bob’s Garden vs. 31% at the TNC Preserve). Supplemental watering treatments had no effect in this year of high precipitation (2016-2017). End-of-spring survival was similarly high at both sites (66-67%), but successful return from dormancy the following spring was higher at the TNC Preserve (28%) than at Bob’s Garden (17%) in this average winter-spring precipitation year (2017-2018). Experimental results largely mirrored results in years with similar precipitation patterns in observational studies. Among-block differences in demographic parameters were highly significant at both sites. Variation in demographic parameters showed spatial pattern related to underlying microsite variation, emphasizing the critical importance of microsite attributes on establishment in this species in addition to year to year variation in precipitation patterns. These studies have given us the tools to augment populations of this rare species and possibly to create new populations through direct seeding.


1 - USFS SHRUB SCIENCES LABORATORY, 735 North 500 East, Provo, UT, 84606, United States
2 - Utah Valley University, 800 W University Pkwy, Orem, UT, 84058, United States
3 - USFS Rocky Mountain Research Station, Shrub Sciences Laboratory, 735 North 500 East, Provo, UT, 84651-9528, United States

Keywords:
Endangered Species
seedling recruitment
spring ephemeral life history
Mojave Desert.

Presentation Type: Oral Paper
Number:
Abstract ID:330
Candidate for Awards:None


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