ARS | Publication request: Small mammal herbivory: Feedbacks that help maintain desertified ecosystems

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2008
Publication Date: January 1, 2009
Citation: Roth, G.A., Whitford, W.G., Steinberger, Y. 2009. Small mammal herbivory: Feedbacks that help maintain desertified ecosystems. Journal of Arid Environments. 73:62-65.

Interpretive Summary: Rangelands around the world have been degraded due to misuse and/or mismanagement. Restoring degraded sties can be expensive, difficult, and time consuming. One factor that contributes to this difficulty in restoration may be the continued grazing of degraded sites by native small animals, such as jackrabbits. This study in southern New Mexico examined the impact of native jackrabbits and kangaroo rats on vegetation of degraded desert conditions. Results indicated jackrabbits had minimal impact on degraded sites. However, small rodents grazing of the few grasses present in degraded conditions may contribute to the persistence of degraded conditions over time. Efforts to restore these degraded sites will need to incorporate effective strategies to minimize the grazing effect of these small rodents.

Technical Abstract: We tested the hypothesis that herbivores contribute to feedbacks maintaining arid ecosystems in a degraded state. We studied small mammal herbivory on a subshrub, broom snakeweed (Gutierrezia sarothrae), and perennial grasses at three sites: (1) ungrazed black grama (Bouteloua eriopoda) grassland; (2) grassland degraded by intense short-duration grazing; and (3) mesquite (Prosopis glandulosa) coppice dunes. Snakeweed was browsed by herbivores primarily during dry winter months. The average percent of G. sarothrae standing crop biomass removed by browsing was 9.2 in ungrazed grassland, 7.4 in intensely grazed grassland, and 4.1 in the dunes. In ungrazed grassland, an average of 12% of grass cover was harvested by herbivores; in the intensely grazed plots – 80%. Herbivore exclusion plots showed that jackrabbits (Lepus californicus) were the primary browsers on snakeweed and rodents on grasses and G. sarothrae inflorescences. Rodent removal of G. sarothrae inflorescences allows wind dispersal of seeds in disturbed and desertified areas, thereby increasing abundance of this poisonous shrub. Grass-tiller cutting by rodents provides a strong feedback that may be responsible for keeping the grass cover low on the intensely grazed areas. Jackrabbit pruning has little effect on G. sarothrae abundance at any stage of desertification.