SPREAD OF INTRODUCED LEHMANN LOVEGRASS ERAGROSTIS-LEHMANNIANA NEES IN SOUTHERN ARIZONA, USA

Through seeding and subsequent spread, Lehmann lovegrass Eragrostis lehmanniana Nees. has transformed the structure and function of at least 145000 ha of semi-desert grassland in southern Arizona since its introduction in 1932. Our study of its spread on the Santa Rita Experimental Range since 1954 showed that by 1989 it was present on >85% of 75 relatively widely dispersed non-seeded permanent plots and accounted for >40% of all perennial grass plants on these plots. In addition, it represented >50% of the perennial grass plants on sites < 16 years after colonization, livestock grazing was not necessary for its spread, and it can account for >90% of the grass biomass and produce 2-4 times more biomass annually than native grass vegetation. In the future, strong consideration of these plant composition changes, and the likely decrease in wildlife diversity and increase in fire frequencies accompanying Lehmann love-grass dominance, should be made before seeding the species.