The effect of small mammal exclusion on grassland recovery from disturbance in the Chihuahuan Desert. (July 2019) - Svejcar, Lauren N.
Abstract: In many arid ecosystems, shrub encroachment is coupled to the loss of perennial grasses and associated ecosystem services. Increased native herbivore abundance associated with shrub encroachment can have negative effects on grass restoration. In the Chihuahuan Desert, native herbivore abundance can be two times greater in shrubland states dominated by Prosopis glandulosa (honey mesquite) than in historical Bouteloua eriopoda (black grama) grasslands. We compared the recovery of B. eriopoda patches following disturbance in plots that were exposed to or protected from native herbivores in shrub-dominated, grass-dominated and ecotone (grass and shrub co-dominated) states. We created a disturbance in the center of B. eriopoda grass patches in each treatment quadrat in 2001. The disturbed areas were measured for recruitment and re-establishment of B. eriopoda in 2002, 2005 and 2008. Although mean rodent abundance was generally greater in shrub-dominated states than other states over the study period, reproductive potential of B. eriopoda was similar in shrub and grass dominated states. Additionally, there was no revegetation by B. eriopoda in any state in response to rodent exclusion. Because increased herbivore abundance in shrub-dominated states did not constrain grass revegetation, other factors are likely to be more important constraints on perennial grass recovery in the Chihuahuan Desert. Highlights: Small mammal herbivores did not constrain grassland regeneration. Herbivore exclusion may not be effective in improving restoration of Bouteloua eriopoda grasslands, in some time periods. Further research into the demography of B. eriopoda ramets and seedlings is needed.