Willow colonization of Rocky Mountain mires

Abstract

Salixplanifolia Pursh ssp. planifolia and Salixmonticola Bebb are the dominant willow species of Colorado Rocky Mountain willow carrs. Extensive field observations suggest that neither of these species is capable of sexual propagation under continuous sedge cover on peat soils. Growth experiments using willow stem cuttings in pots of saturated peat soil indicate that S. planifolia produces more root biomass (p = 0.0031) and shoot biomass (p = 0.0001) than S. monticola during one summer of growth. Male 5. planifolia and female S. monticola produce more dry-weight root (p = 0.0390) and shoot (p = 0.0442) biomass than their conspecific opposite sex. A species by sex by elevation interaction is significant for root biomass (p = 0.0360). The results are suggestive that these taxa have different regeneration niches. Asexual propagation driven by beaver activity is suggested as an explanation for the dominance of s. planifolia in mires and how this species colonizes vegetated peat soils. Beaver cut and store willow stems for a winter food source. This activity provides willow fragments for asexual colonization of mires.