Effect of native shrubland replacement by pine plantations on actual evapotranspiration and percolation for historical and future periods in the Cauquenes river basin
La continua expansión de las plantaciones exóticas de pino ha generado el reemplazo de la vegetación nativa como es el caso del matorral espinoso, esto podría traer consecuencias en el ciclo hidrológico de las zonas donde ocurre este cambio de uso del suelo. El objetivo de esta investigación fue evaluar el efecto del reemplazo de áreas de matorrales de Acacia caven por plantaciones forestales de Pinus radiata en las tasas de evapotranspiración real (ETr) y percolación históricas y futuras en la cuenca pluvial del río Cauquenes. Se implementó el modelo HYDRUS-1D para cuantificar la ETr y percolación bajo diferentes escenarios de clima pasado, presente y futuro en tres repeticiones por cobertura. Las verificaciones del contenido de agua en el suelo y transpiración del modelo fueron satisfactorias arrojando valores de R2> 0,9, KGE >0,85 y PBIAS 0,7, KGE >0,55 y PBIAS 0.9, KGE> 0.85 and PBIAS 0.7, KGE> 0.55 and PBIAS <15%, respectively. The results indicate that from 1979 to 2019 there has been a decrease in the ETa rate and percolation in both covers, especially during the mega-drought period (2010-2019). The yearly differences between coverages showed that ETa was between 180 to 214 mm year-1 more in pines than shrubland and that shrubland percolates between 184 to 237 mm year-1 more than pines, regardless of the scenario analyzed. In future scenarios, both coverages will decrease their percolation, but pines will tend to values close to zero, because they will have to access to water table or suppress percolation to maintain their ETa rates. The historical replacement of shrubland by pine trees within the basin (corresponding to 7,751 ha) in the three temporal scenarios analyzed, yielded amounts of 15 to 19 million m3 year-1 additional of water lost to the atmosphere due to ETa and between 14 to 18 million m3 year-1 decrease in percolated water. In view of the country's challenge to opt for carbon neutrality, it is expected that plantations will continue to expand, but the results reported in this study and the scarcity of water that exists in this area impose challenges that should be focused on territorial planning to ensure the sustainable development to which Chile is committed.Versión original del auto
