Desertification in cattle systems of the southwest extreme of pampean region, Argentina

AMIOTTI N. M; BRAVO, O.; MARELLO, D.

Conferencia; VII International Conference on Aeolian Research; 2010

The main cause of desertification is the land utilization beyond their capabilities. The aim of this study was to quantify the effect of grazing on plant communities and on physical and chemical soil properties. The experience was conducted in western of Villarino District, Buenos Aires. The climate is temperate-semiarid with mean annual temperature of 14.5 ºC. Precipitation is 400 mm yr-1 and the mean annual winds velocity is 3.1 m s-1. The soils classified as Entic Haplustols. Three treatments were compared: NP: natural pasture; ONP: overgrazed natural pasture and OOP: overgrazed oats pasture. The abundance-density and basal coverage area of plants, as well as, soil texture, bulk density (BD), total organic matter (TOM), particulate organic matter (POM) and erodibility fraction were determined. NP showed strata of rich shrub and herbaceous species with high forage value. Bare soil percentage was negligible. In ONP, the shrub strata was absent and in the herbaceous a lower diversity and dominance of unpalatable, with 57% of bare soil was observed. OOP evidenced degradation with absence of palatable species and a very low coverage (33%). Overgrazing altered the initial soil physical properties with marked increases in BD. Significant losses of TOM (35% in ONP, and 26% in OOP) and POM (42% and 61% related to NP) were detected. Soil textures were homogeneous (sandy loam) and the erodibility fraction ranged between 0.49 and 0.52. The damage caused by overgrazing indicates a marked deterioration of vegetation cover and a sharp decline in soil quality. Analysed livestock systems are vulnerable to soil loss by wind erosion and to desertification processes.