Sensibilidad y resiliencia a la sequía de las principales especies forestales implantadas en Patagonia Argentina: Pinus ponderosa y Pseudotsuga menziesii

WEIGANDT M; VARELA S.; DIEZ JP; GYENGE JE; FERNÁNDEZ M.E.

Mar del Plata

Congreso; XXVIII Reunión Argentina de Ecología; 2018

Soc. Arg. Ecol.

An increase in the frequencyand intensity of global drought events is expected under climate change context. For Patagonia, a greatervariability of rainfall is predicted with tendencies to a climate of greaterwater deficit, with an increasing frequency of extreme drought events. In N.W. region the main implantedspecies are Pinus ponderosa and Pseudotsuga menziesii. Plantations must survive andto grow under climatic conditions that prevail within 30 or 40 years. While both species havecharacteristics that allow them to resist drought, in the last decades mortalityhas been observed at individual level after extreme droughts (e.g. 1998-1999and 2007-2009 years). Knowledge of the climatic effect on vegetation hadecological and productive importance, being necessary studies on thesensibility and resilience of both species in front of the past and presentclimatic conditions to predict future behaviors. We analyzed the above mentionedaspects under a dendroecological approach, recording the response of bothspecies in sites with high and low resource availability and different levelsof intraspecific competition. Tree cores were extracted under the mentionedconditions, mounted, sanded and scanned. The obtained images were used to measure ring width (growth)and to co-dating. Sensitivity andresilience indexes were estimated, knowing their response to the differentdrought events. A reduction in annualradial growth values was observed in both sites for both species (greater than60%), with greater sensitivity, in general, at the most xeric site. In mostcases, resilience was greater after first drought event than second one; thiscan be attributed to a cumulative effect of stress. These results quantify themagnitude of productivity decrease under drought conditions, and indicate thatin spite of resilience is high in both species, repeated events decrease thiscapacity threatening both production and survival of the trees.