Altitudinal and interannual variation in seedling survival of tree species in central Chile: implications for sclerophyllous forest restoration

Abstract

An important issue in ecological restoration of forest ecosystems is toestablish where reforestation is more limited by ecological factors andthus where additional treatments (e.g. irrigation, shading) are moreneeded. Population growth, density and reproduction in plants havefrequently been documented to decrease with altitude, although insemiarid regions, initial increases up to middle elevations and thendecreasing upward have been reported. In the semiarid region of centralChile, the Andean sclerophyllous forest is distributed between 400 and1,600 m a.s.l. In this paper, we tested the hypothesis thatreforestation in this ecosystem should be more successful at middleelevations of its altitudinal range. We planted twenty seedlings ofthree shade-intolerant tree species (Lithraea caustica, Quillajasaponaria and Schinus polygamus) in five sites along an elevationgradient (480 to 1,500 m a.s.l.). We repeated the experiment during twoconsecutive years (2007 and 2008) that had different climaticconditions. Seedling survival for all species was superior at higherelevations in both experimental years, and final survival did not differbetween years at any elevation level in the three species. In contrastto our initial prediction, these results suggest that reforestation ofthe Andean sclerophyllous forest is more successful at higher altitudes,and that at lower altitudes, additional treatments (irrigation, shading,etc.) would be needed to restore these forests.