The effects of canopy openings and population size on the persistence of Southwest columbines at risk of extinction

Abstract

The habitat associated with riparian, understory, rare and endangered plant populations of the Southwest includes rocky places in high-altitude canyons, mostly along shady streams, pools, and dripping cliffs. The composition of these insular plant populations, which are separated by intervening desert, is influenced by several local environmental conditions. The understory light environment, which is influenced by canopy cover, is a key determinant of vegetation patterns; it varies spatially within and among populations, and is determined by intermediate closure and light availability. Light availability could directly affect individual fitness (via affecting photosynthetic, micro-climatic, and transpirational processes) and subsequently could indirectly affect plant population size and persistence. We examined the environmental influences of canopy cover and light availability in seven populations of herbaceous, perennial yellow columbines (genus Aquilegia) in the Southwest. Aquilegia populations exhibit many of the characteristics, particularly isolation and relatively small population size, associated with at-risk populations. For example, Aquilegia chaplinei, or Chapline's columbine, is currently protected under the New Mexico Endangered Plant Species Act. Canopy cover and understory light environments were quantified from the view each plant has of the sky, measured via vertical photography. These images were analyzed to investigate the percentage of sky versus canopy cover, as well as the relationship of canopy cover and within- and among-population traits. Overall, these ecological assessments will help expand our understanding of environmental influences and may be important in regard to the conservation, persistence, and recovery of small, isolated plant populations.

Parent Publication

• Southwestern rare and endangered plants: Proceedings of the Third Conference

Citation

Gallagher, Kelly G.; Milligan, Brook G. 2001. The effects of canopy openings and population size on the persistence of Southwest columbines at risk of extinction. In: Maschinski, Joyce; Holter, Louella, tech. eds. Southwestern rare and endangered plants: Proceedings of the Third Conference; 2000 September 25-28; Flagstaff, AZ. Proceedings RMRS-P-23. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 110-115.