Rangeland management and small mammal functional diversity loss in the Monte desert, Argentina

CHILLO, VERÓNICA Y RICARDO OJEDA

Mendoza, Argentina

Congreso; 10th International Mammalogical Congress; 2009

CONICET, CCT Mendoza, IADIZA, GIB, International Federation of Mammalogist (IFM) y Sociedad Argentina para el Estudio de los Mamiferos (SAREM)

Rangeland production in arid ecosystems uses artificial watering points, generating radial grazing gradient patterns called piosphere. We analyzed the effect of piosphere over the structure and functional diversity of small mammal assemblages under two grazing systems. Three radial transects with ten sample points each were placed in an experimental rangeland with rotational grazing (RG) and in a neighbor rangeland with continuous grazing (CG), in the Monte desert, central-west Argentina. Sample points were separated by 50, 50, 50, 100, 200, 400, 600, 600, and 600 m from each other. Community structure was represented using range-abundance curves. Functional diversity (FD) was calculated using Rao?s index with 11 traits regarding nutrient cycling function and habitat use. Using Syncsa software we separated traits that maximized assemblage divergence patterns along the gradient. In both rangelands, community structure close to the watering point was highly dominated by one species with ecomorphological adaptations to open habitats (Eligmodontia sp.). Only under RG did the community diversify away from the water, with an exponential increase in FD beyond 1200 m (r=0.82, p<0.001). Under CG, FD values did not increase with distance, but had the maximum in two outliers close to water. Traits that maximized divergence were significant only in RG, and were related to diet (insectivorous, granivorous and omnivorous) and bipedal locomotion (ρ=0.652, p<0.01). These traits represent ecomorphological characters that vary the most within the community, improving ecosystem functioning. Away from watering points under RG, more complex habitat structure allows more diverse life strategies, increasing trait divergence. The loss of these traits at higher livestock densities and under CG may have significant effects over ecosystem functioning by diminishing the diversity of nutrient cycling strategies. We suggest long-term rest RG strategies to avoid small mammal functional diversity loss (Partially supported by PICT-Agencia and CONICET).