Fire, species richness and aerial biomass distribution in mountain grasslands of Northwest Argentina

ROXANA ARAGÓN; JULIETA CARRILLA; LUCIANA CRISTOBAL

Land Use Changes and Mountain Biodiversity

CRC Press LLC

Lugar: Boca Raton, Florida, USA; Año: 2006; p. 89 - 100

Abstract Fire and grazing are the most common disturbances in the mountain grasslands of northwest Argentina. They can affect species composition and richness, determine dominant life-form, and the general structure of the community. This work aims to determine the effect of burning on species richness, vegetation structure, and aerial biomass distribution in the grasslands of northwest Argentina that are subjected to grazing. We performed a comparative study at Los Toldos, Salta, Argentina (22º30 S, 64º50 W) at 1700 masl and surveyed patches that differed in the time since the last fire event. We considered three treatments: patches that were burned during the ongoing growing season (in spring 2000), burned the previous season, or not burned for at least 5 yr. Treatments did not cause differences in species richness, and caused only small changes in species composition. The equativity of life-forms showed a tendency to decrease with fire suppression, with woody species becoming more dominant in plots that were not recently burned. Total biomass and the proportions of live biomass, standing dead, and litter varied among treatments. Fire caused a reduction in total biomass, but increased the contribution of live biomass and encouraged the development of more palatable growth forms (mainly grasses). Patches that were burned during the ongoing growing season had 80% of their biomass as live biomass in December and January. In these months, livestock is moved from forests at lower altitudinal levels to these highland grasslands. This modification in the seasonal dynamics of aerial biomass may represent a substantial change in the pattern of forage availability, especially at this time of the year.