Restoring Palmer's agave in a Lehmann lovegrass dominated grassland in southeastern Arizona

Dryland restoration is becoming increasingly challenging in arid and semiarid regions, such as in the southwestern United States, due to rapid land degradation, the spread of non-native species, and climate change. The development of strategies to enhance restoration of native species, particularly culturally and ecologically important native plants like Palmer's agave (Agave palmeri), is particularly critical in southeastern arid lands where scarce rainfall, herbivory, and invasive species dominance pose unique challenges to land management. In a large field experiment in southeastern Arizona, U.S.A., we assessed the utility of several management techniques to promote restoration and revegetation outcomes for Palmer's agave survival and growth, including protection from solar insolation and herbivory, and reduction in the competitiveness of Lehmann lovegrass (Eragrostis lehmanniana). We found that the combination of herbivory protection and shade resulted in the highest survival of planted agaves, while the shade treatment alone resulted in the largest agaves. In fact, our results suggest that dense Lehmann lovegrass cover protects agaves from direct sunlight and predation. If land managers are challenged by widespread Lehmann lovegrass, they can opt to mechanically reduce it. However, if population recovery of Palmer's agave is a priority and fire hazard is minimal, our work suggests that stakeholders concerned with population recovery of Palmer's agave can forgo removing existing vegetation and plant agaves in a matrix of (and/or under the canopy of) existing vegetation.

Automated summary

Dryland restoration is challenging in arid and semiarid regions due to land degradation, non-native species, and climate change. This study in southeastern Arizona found that protecting agaves from herbivory and providing shade resulted in the highest survival rate, while shade alone led to larger agaves. Dense Lehmann lovegrass cover was found to protect agaves from direct sunlight and predation. Land managers can mechanically reduce Lehmann lovegrass or plant agaves in existing vegetation to promote population recovery of Palmer's agave.