Patterns of willow seed dispersal, seed entrapment, and seedling establishment in a heavily browsed montane riparian ecosystem
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Authors: E. A. Gage, and D. J. Cooper
Date: 2005
Journal: Canadian Journal of Botany
Volume: 83
Number: 6
Pages: 678-687
Summary of Methods: Examined the potential factors that limit the establishment of willows (Salix spp.) on two sites within Rocky Mountain National Park, Colorado. High levels of browsing occurred within the park, resulting in the production of few aments and potentially decreased reproduction of shrubby species. The two year study examined seed dispersal phenology, germinability, and the spatial patterns of aerial seed rain. In addition, it quantified the effects of soil surface relief, texture, and moisture on seed entrapment, and examined natural patterns of seedling emergence in relation to seed source proximity.
Article Summary / Main Points: Willow seed rain patterns and subsequent seedling density is strongly influenced by the distribution of seed-producing plants. Seed dispersal began in late May and continued through early July, timing dependent upon species. Seed dispersal of the highly abundant species (S. monticola and S. geyeriana) coincided with declines in streamflow. All species exhibited high germination rates (85-99%). Total number of seeds dispersed differed between years with spatial patterns of seed rain varying by location within the park. Seed rain patterns drop sharply as distance from plant increases; 50% of seeds located within 30 m of seed source, over 90% of total seed within 200 m of seed source. Willow seed entrapment rates varied from 2-30% with high relief and moist areas capturing more seed than low relief and drier areas.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 48A Southern Rocky Mountains
Agrovoc Control Words: Riparian zones Salix Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: willow, salix spp., riparian, dispersal, ungulates, elk, cervus elaphus
Annotation: Study did not measure levels of elk herbivory, but refers you to previous research (Peinetti et al. 2001) where elk herbivory was linked to willow stature and seed production. Ongoing loss of willows due to heavy browsing, along with low establishment and recruitment rates, could result in the transformation of shrub-dominated riparian communities into herbaceous-dominated ones. These findings are consistent with results observed in other areas such as Yellowstone National Park and are applicable to all western riparian areas where high levels of browsing occur on riparian willows.
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