CR 09:9-15 (1997)  -  DOI: https://doi.org/10.3354/cr009009

Results from the first attempt at implementing the SPUR2 (Simulation of Production and Utilization of Rangelands) simulation model under the specific conditions of a deep soil on basalt rock in Uruguay are presented. The study area was selected because it represents a large portion of Uruguayan land (21%) almost exclusively oriented to cattle production; due to the variety of soil types in this region it was possible to analyze contrasting situations regarding vulnerability to the occurrence of extreme climatic events--such as droughts--and to potential climate changes. The information used, which included soil texture, organic matter content and hydrologic characteristics, corresponded to a representative soil of the Itapebí Tres Arboles unit. The weather data used were daily records for precipitation, as well as air temperature, solar radiation and wind run data simulated with a climate generator program. The model was run for the 1961-1990 period under normal (present day) carbon dioxide concentration conditions. The analysis focussed particularly on the SPUR2 outputs of the hydrology and plant submodels. Biomass production simulations showed a good representation of reality with regard to annual production. However, they differed from the actual data available for this area with regard to the seasonal distribution of forage. The results of the hydrology submodel significantly departed from the expected values. Potential evapotranspiration reached monthly values 148% above normal (observed), which could be partly explained by the fact that the global solar radiation estimates were higher than the real values.

Simulation model · SPUR2 · Natural pastures · Grazing system · Climate change