Effect of Pinus radiata plantations on water balance in Chile

The effect of Pinus radiata (D. Don) plantations on water resources at different Chilean sites located between 33 degrees and 40 degrees south was determined. Incoming precipitation. canopy interception loss, evapotranspiration, net evapotranspiration (transpiration and evaporation from the soil). percolation and soil water content were measured in each site, where Pinus radiata plantations were 12 to 17 years old and between 700 and 830 trees ha(-1) dense. The results were compared with those obtained from areas covered with perennial grasses and shrubs at the same sites. The pine canopies intercepted on average 36-40% of the annual rainfall at all sites where rainfall was less then 1200 mm, while only 15% of the mean rainfall was intercepted in the southernmost and rainy (2081 mm year(-1)) site. Annual net evapotranspiration increased from south to north from 32% of the incoming precipitation for the southern most site to 55% for the one located at the lower latitude. In this northernmost site almost the entire incoming precipitation was evapotranspired. Annual percolation registered its minimum value in the northern site (5% of incoming precipitation) and its maxima in the southern one (53%). The values of net evapotranspiration and percolation were regulated by the pluviometric regime and the soil moisture retention capacity in each site. Compared with the shrub or grass covers, sites under Pinus radiata plantations registered higher water consumption by evapotranspiration and reduced percolation. Copyright (C) 2007 John Wiley & Sons, Ltd.