Influences of wind and sandblasting on the endangered blowout penstemon

Abstract

Blowout penstemon Penstemon haydenii is a federally endangered species growing only in areas with active wind erosion in sand dunes of the central United States. This early seral spe- cies declines as the blowout habitat stabilizes, allowing later seral species to increase. Blowout pen- stemon populations and plant size declined in the 1990s when precipitation was higher than normal, resulting in reduced sand movement. We conducted a greenhouse experiment to determine whether blowing sand influenced vigor and persistence of blowout penstemon seedlings. Treatments were wind, sandblasting, wind with sandblasting, and a control. The wind treatment was a constant 14 km h -1 from electric fans for 18 h daily. Sand was applied at 96 km h -1 weekly for 10 min to individual plants for the sandblasting treatment, and the wind with sandblasting treatment was a combination of both. Number of leaf pairs, height, and stem diameter were measured biweekly. Biomass was determined at the conclusion of each experiment. Both wind and sandblasting affected plant growth. The combination of wind with sandblasting increased plant height and stem diameter in Year 1, and stem diameter and shoot biomass in Year 2. This study supports field observations that blowout pen- stemon has a positive thigmomorphogenic response to wind and sandblasting. Less sand movement is associated with wet soils. Therefore, loss of mechanical stimuli could have been one of the reasons for population decline in the 1990s. Disturbance may be necessary to maintain the blowout habitat and provide an important stimulus to the blowout penstemon plants.