Buffelgrass Expansion Rate and Dispersal Type on Recently Invaded Barry M. Goldwater Range of Southwestern Arizona

Abstract

Land managers have struggled to develop successful control strategies to address buffelgrass invasion in the Sonoran Desert. Two important variables for control strategies are dispersal type and patch expansion rate (i.e. satellite or invasion front). We investigated these variables along a highway invaded within the last 10 years located south of Gila Bend, Arizona, USA. Dispersal type was calculated by documenting the location of each buffelgrass individual along a 16 km stretch of highway and using an average nearest neighbor analysis in ArcMap 10.2.2. Thirty-six patches were monitored for four years along a 56 km stretch of highway 85 by documenting the outlines of each patch. Dispersal type registered as satellite dispersal (i.e. clustered on the Nearest Neighbor test), z-score = -47.2, p < 0.01. Patch expansion exhibited a median doubling time of 0.81 years. The results of the dispersal type analysis represent an opportunity to enhance control strategies, by targeting buffelgrass satellites and theoretically reducing patch expansion exponentially. The patch expansion rates for buffelgrass were faster than found in past research, giving land managers a clearer understanding buffelgrass patch expansion behavior.