ARS | Publication request: Importance of ecotone type to landscape dynamics at biome transition zones

Submitted to: US-International Association for Landscape Ecology
Publication Type: Abstract Only
Publication Acceptance Date: January 28, 2009
Publication Date: N/A

Technical Abstract: Landscapes in biome transition zones consist of a mosaic of patches dominated or codominated by species from adjacent biomes. Shifts in the vegetation composition and dynamics of a biome transition zone depend upon the underlying patch dynamics of the ecotones between these dominant species. Landscapes can consist of a number of different types of ecotones (directional, shifting, stationary) hypothesized to differ in the strength of three major factors: abiotic drivers, biotic feedbacks, and abiotic feedbacks. In this poster, our objective was to test the hypothesis that vegetation patterns across stationary ecotones are strongly related to abiotic factors that influence water availability (soil texture, microtopography) where we3ak correlations were expected for shifting ecotones. We tested this hypothesis for landscapes at the Sevilleta LTER site in central New Mexico, USA/ Landscapes at the Sevilleta consist of a mosaic of patches dominated or codominated by three species: two perennial C4 grasses, Bouteloua gracilis (blue grama) and Bouteloua eriopods (black grama), and one C3 shrub, Larrea tridentate (creosotebush). We estimated cover by species, analyzed soil samples (0-20 cm), and obtained elevation using a Total Positioning Station every 5-10 m along multiple transects for 10 ecotones. Our results show that stationary ecotones occur on finer-textured soils at slightly lower elevations (cms) compared with shifting ecotones. Soil and elevation were not good predictors of the location of shifting ecotones. Our results suggest that landscape dynamics at the biome transition zone dwpend on the factors controlling different types of ecotones. Even though the same species may be involved, the underlying processes determining ecotones dynamics may vary for different parts of the landscape.