Biotic and Abiotic Factors Important for Palmer’s Agave Restoration in Lehmann Lovegrass Dominated Areas

Abstract

ABSTRACT Encroachment of Eragrostis lehmanniana (Lehmann lovegrass), a non-native perennial grass species, challenges land managers in the southwestern United States due to its tendency to increase fire frequency and displacement of natives. In areas characterized by disturbance, E. lehmanniana displaces Agave palmeri (Palmer’s agave), an ecologically and socioculturally significant native plant species in the Sonoran Desert. We explored strategies to enhance short-term A. palmeri establishment using a greenhouse experiment. We assessed survival and growth responses of transplanted A. palmeri exposed to a variety of manipulated variables, including biotic (agave size at planting and E. lehmanniana competition) and abiotic (simulated precipitation and surface litter). We found a significant increase in A. palmeri biomass in the absence of E. lehmanniana in the high and medium watering treatments compared to agave in the presence of clipped E. lehmanniana neighbors. The presence of E. lehmanniana did not significantly affect A. palmeri biomass in the low water treatment. In the medium and low watering treatments, A. palmeri with litter had nearly twice the biomass as those without litter. The absence of E. lehmanniana with the high watering treatment and litter resulted in the largest agave biomass. For improved A. palmeri growth (and likely its survival) in restoration projects, we recommend supplemental watering and litter addition. Removal of E. lehmanniana is also suggested (by hand if possible); however, this species could operate as a nurse plant for agaves.