Non-linear relationships between grazing pressure and conservation.

BISIGATO, AJ; LOPEZ LAPHITZ, RM; CARRERA, AL

JOURNAL OF ARID ENVIRONMENTS

Elsevier

Año: 2008 p. 1464 - 1475

0140-1963

Grazing effects on soil organic carbon (C) and nitrogen (N) have not been consistent in different studies. Whereas several authors have found changes in the quantity and/or spatial distribution of these soil resources as a consequence of grazing, others have not found any effect. We hypothesized that these discrepancies are due to non-linear relationships between grazing pressure and conservation of soil resources. Therefore, our aim was to identify non-linear responses of soil resources (soil organic-C and soil-N) to grazing pressure in a Patagonian Monte shrubland, and their probable causes. We evaluated the amount and distribution of soil resources, the development of soil mounds associated to shrub patches, and the display of signs of wind erosion in 6 sites under different grazing pressure. Our results indicate that the conservation of soil resources was not linearly related to grazing. In a first stage of ecosystem degradation, grazing causes the remobilisation of fine sediments and soil resources and their accumulation in shrub patches. In a second stage, after plant cover is further reduced, soil resources are lost from the system, presumably by wind erosion. Finally, our results also highlight the importance of including several sites under a wide range of grazing pressures/disturbance to identify non-linear responses of soil resources to grazing in shrublands.