INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Assessing tree demography under climate change in Nothofagus pumilio forests at the altitudinal gradient in Southern Patagonia, Argentina
SRUR, A. M.; ASCHERO, V.; VILLALBA, R.
Conferencia; Ameridendro 2016 Third American Dendrochronology Conference; 2016
Mean annual temperatures in the Southern Patagonian Andeshave increased since the 1950´s. The effects of these highertemperatures on tree demography are not easily predicted anddifferent effects are expected over the altitudinal range ofNothofagus pumilio forests. For example, in low-elevation dryforests, detrimental microclimatic conditions for forestregeneration are expected with increasing temperatures,particularly if droughts became more frequent. In contrast,higher temperatures could ameliorate adverse environmentalconditions for seedling establishment at high elevations byextending the growing-season length and reducing the stress dueto heavy and/or long-lasting snow accumulation. We have beenmonitoring N. pumilio vital rates (reproduction, growth andmortality) in permanent plots at low and high elevations at ElChaltén, Santa Cruz, Argentina since 2012. The idea of thismonitoring is test the hypothesis that recent climate changes inSouthern Patagonia have influenced tree demography differentlyat different elevations. Here, we present our first results aboutforest regeneration, tree growth and mortality at the extremesof the altitudinal gradient. Between 2012 and 2014 the density ofnew-born seedlings at high-altitude forests was 13 times greaterthan at low altitudes. In contrast, the mortality of markedseedlings was higher at low-altitude than at high-altitude forests.Consequently, seedling density is lower at the low- than at thehigh-altitude sites. Positive temporal trends in tree growth athigh-altitude forests in recent decades 1900-2008) contrasts withstable or decreasing trends at lower elevations. The mortality ofadult individuals registered in two years (>5 cm dbh) was higherat the low (-6%, n=116) than at high-altitude sites (2%, n=102).Therefore, low altitude forest, showed limited regeneration andhigher probability of adult tree mortality in the years of survey.These patterns support the hypothesis that climate changes candifferently affect the N. pumilio demography along altitudinalranges in mountain forests.