FACTORS PREDISPOSING EPISODIC DROUGHT-INDUCED TREE MORTALITY IN NOTHOFAGUS: SITE, CLIMATIC SENSITIVITY AND GROWTH TRENDS
MARIA LAURA SUAREZ, LUCIANA GHERMANDI, AND THOMAS KITZBERGER
JOURNAL OF ECOLOGY (PRINT)
Año: 2004 vol. 92 p. 954 - 966
Abstract During 1998-99 a severe drought affected northern Patagonia in relation to strong La Niña conditions. This period constitutes one of the most severe drought during the twentieth century in terms of precipitation deficit. This extreme drought resulted in immediately high Nothofagus dombeyi (coihue) mortality rates at Nahuel Huapi National Park. In this study we examined both at the stand and individual scale the factors involved in determining Nothofagus mortality following the 1998-99 drought. At stand-scale, high mortality patches had the highest abundance of dead-standing barkless tress, and boring insect-infested trees; supporting the idea that recurring climatic/biotic events make forest more prone to be killed by subsequent stress. At tree-scale our results confirm the prediction that N.dombeyi individuals with more variable growth were more prone to die from drought than trees with more complacent growth. In addition, mean growth rate was a good predictor of mortality in adult trees, showing that adult trees with declining growth were more susceptible to die than trees without this trend. Severe drought occurred regionally over northern Patagonia in1956-57 were associated with further accentuated reductions in growth rate in dead trees, and as possible intervention years as growth trajectories between live and dead adult trees bifurcate. These results emphasize the role of repeated severe droughts in predisposing trees to eventual death.