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United States Department of Agriculture

Agricultural Research Service

Title: Woody Plant Invasion at a Semi-Arid/arid Transition Zone: Importance of Ecosystem Type to Colonization and Patch Expansion

Authors
item Peters, Debra
item Yao, Jin - NEW MEXICO STATE UNIV
item Gosz, James - UNIVERSITY OF NM

Submitted to: Journal of Vegetation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 3, 2006
Publication Date: June 15, 2006
Citation: Peters, D.P.C., Yao, J., Gosz, J.R. 2006. Woody plant invasion at a semi-arid/arid transition zone: importance of ecosystem type to colonization and patch expansion. Journal of Vegetation Science. 17:389-396.

Interpretive Summary: We examined how patterns in colonization and patch expansion of creosotebush differ between grasslands dominated either by the Chihuahuan Desert species, black grama, or by the shortgrass steppe species, blue grama, at a biome transition zone in central New Mexico. We sampled frequency of occurrence, height, and surface area of saplings (n=134) and patches of adult plants (n=247) of creosotebush within a mosaic of ecosystems dominated by one of the two grass species. Our results showed that creosotebush saplings (<1%) and adults (15%) occur less frequently in black grama- than blue grama-dominated ecosystems. Evidence was found for both local and long distance dispersal. We conclude that the persistence of grasslands at this site despite region-wide expansion by creosotebush may be related to the spatial distribution of blue grama-dominated ecosystems that resist or deter invasion by this woody plant.

Technical Abstract: Our objective was to evaluate how patterns in colonization and patch expansion of an invasive woody plant, Larrea tridentata (creosotebush) differ between two grassland ecosystems at a biome transition zone. We sampled frequency of occurrence, height, and surface area of saplings (n=134) and patches of adult plants (n=247) of creosotebush within a mosaic of ecosystems dominated either by the Chihuahuan Desert species, black grama, or the shortgrass steppe species, blue grama, located within 1 km of the creosotebush-dominated ecosystem. Distances between patches and patch area were used to estimate connectivity and propagule pressure. Sapling height and distance to the creosotebush dominated ecosystem were used to estimate patterns in dispersal. Our results show that creosotebush saplings (<1%) and patches of adults (15%) occur less frequently in black grama than blue grama-dominated ecosystems. Propagule pressure did not differ with distance from the core creosotebush ecosystem. Evidence was found for both local and long distance dispersal. We conclude that spatial variation in creosotebush saplings and adults at this biome transition zone is related to the different susceptibilities to invasion by the two grassland ecosystems. The persistence of grasslands at this site despite region-wide expansion by creosotebush may be related to the spatial distribution of blue grama-dominated ecosystems that resist or deter invasion by this species.

Last Modified: 12/22/2014
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