Enhancing Quality of Desert Tortoise Habitat: Augmenting Native Forage and Cover Plants

Abstract

Abstract Vegetation in habitat of the federally listed desert tortoise Gopherus agassizii in the Mojave and western Sonoran Desert is now partly or mostly dominated by nonnative annual plants. To improve forage quality and augment availability of perennial cover plants, we tested seeding (pelletized or bare seeding), watering, and fencing for increasing a native annual forage species (desert plantain Plantago ovata), a perennial forage species (desert globemallow Sphaeralcea ambigua), and two shrub species (cheesebush Hymenoclea salsola and winterfat Krascheninnikovia lanata) that provide cover in desert tortoise habitat of southern Nevada. Treatments were ineffective at establishing the perennial species, even though greenhouse assays confirmed that some bare and pelletized seeds were germinable. In contrast, pelletized seeding quadrupled the density of desert plantain compared with not seeding or seeding untreated seed by the end of the first year (autumn 2013). Fencing tripled density of desert plantain to 17 plants/m2. Pelletized seeding plus fencing produced a desert plantain density of 39 plants/m2, the highest average density among all treatment combinations. The positive effect of fencing persisted until at least the second year after treatment (autumn 2014). Augmenting native annual forage plants favored by desert tortoises is feasible.