Abstract Detail

Conservation Biology

Daggett, Catherine [1], Berry, Eric [2].

Measuring the Effect of Decreasing Water Potential on Seed Germination, Seedling Development, and Population Growth in the Endangered Wildflower Northern Wild Senna (Senna hebecarpa).

Northern Wild Senna (Senna hebecarpa) is an endangered native wildflower with a limited range within New England. Extant populations in the region are in decline, with a number of states listing the species as historic. Possible reasons for the decline include natural ecological succession, habitat loss, and, of greatest interest for this study, changes in soil hydrology. Senna hebecarpa thrives in moist soils and is typically found along stream banks or other alluvial sites. Decreases in springtime soil water potential due to hydrological changes from dam construction, ditching, or other means may adversely affect germination rates, contributing to further population decline. Our study examined the impact of water potential on seed germination and seedling growth in S. hebecarpa. We simulated soils of varying water potentials ranging from 0Ψ (pure water) to -10Ψ by mixing Polyethylene Glycol (PEG) 8000 and water to produce a colloidal solution that has been shown to simulate the effects produced by the matric properties of soil particles. Seeds were scarified, placed in petri dishes, and grown for 14 days. Our results indicate that S. hebecarpa seeds germinate well under conditions between 0Ψ - 1Ψ, but germination rates drop to nearly zero at less than 2Ψ. Likewise seedling growth was significantly reduced under conditions less than 2Ψ. We also examined the impact of reduced germination on population growth (finite rate of growth, λ) by incorporating germination rates from our experiment into transition matrix models parameterized from a wild population of S. hebecarpa in Amherst, NH. These simulations revealed that although λ is only moderately sensitive to changes in seed germination (i.e. low elasticity values), the magnitude of the response of decreasing water potential on germination rates produced a significant decline in population growth over the range of water potentials studied. These results reinforce the concern that hydrological changes to S. hebecarpa habitat can contribute to the species decline.

Broader Impacts:

1 - Saint Anselm College, 100 Saint Anselm Drive, Manchester, NH, 03102, USA
2 - Saint Anselm College, Biology, 100 Saint Anselm Drive, Manchester, NH, 03102, USA

Keywords:
Senna hebecarpa
finite rate of growth
water potential
seedling growth and development
seed germination.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM
Number: PCB002
Abstract ID:206