Assessing the dendroclimatic potential of Nothofagus betuloides (Magellan\u2019s beech) forests in the southernmost Chilean Patagonia

Mauricio Fuentes,Juan Carlos Aravena,Hans W Linderholm,Andrea Seim

doi:10.1007/s00468-018-1801-1

Mauricio Fuentes, Juan Carlos Aravena + Show 2 more

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https://doi.org/10.1007/s00468-018-1801-1

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Abstract

Key messageTree growth of Nothofagus betuloides forests south of 50°S is affected by local temperature and precipitation together with large-scale high-latitude climate patterns, but also significant influences from the Tropical Pacific were found.The characterization of past climate dynamics in southern South America is difficult due to the shortness of instrumental data. However, abundant forests in the southernmost part of the continent makes it an ideal place to assess the dendroclimatological potential for developing high-resolution climate proxy time series to extend the observations back in time. Whereas the majority of dendroclimatological studies have focused on latitudes north of 50°S, we present six new Magellan’s beech (Nothofagus betuloides (Mirb.) Oerst.) tree-ring width (TRW) chronologies, spanning between 202 and 500 years, developed from southernmost Patagonia (> 50°S), Chile. The climate signal in the trees was analyzed using local station data, regional sea surface temperature (SST) and large-scale atmospheric indices: the Southern Oscillation Index (SOI) and the southern annual mode (SAM). The correlations between individual site chronologies and observed summer temperatures and precipitation varied, reflecting diverse microsite conditions and local scale geographic patterns. An influence of southern Pacific SST was evident at two of the northern sites. Although the associations with SOI and SAM were weak, the influence of regional sea level pressure on tree growth in the region was evident.

Highlights

Few studies have analyzed the climatic influence on tree growth, and their dendroclimatological potential, in a regional context in southernmost South America
The variability of precipitation and temperature in southern Patagonia is largely depending on the westerly wind flow (Carrasco et al 2002), which during the austral summer is organized into two bands centered at around 40°S and 60°S, and is related to the exchange of atmospheric pressure described by the southern annular mode (SAM)
Common periods of enhanced growth are centered around 1705 for the three longer site chronologies: Alejandro Valley (ALE), DF2, and DP, in addition to 1760 which is indicated by ST

Summary

Introduction

Few studies have analyzed the climatic influence on tree growth, and their dendroclimatological potential, in a regional context in southernmost South America. The heterogeneity of the geography is due to the topography, with mountains rising from sea level up to more than 2000 m a.s.l., interspersed with valleys and glaciers (Pisano 1977) This mosaic-like landscape must be seen within a larger geographical context, which encompasses a permanent influence of the Southern Ocean, the westerly winds and a distinct precipitation gradient from west to east (Carrasco et al 2002; Schneider et al 2003; Garreaud et al 2013). These factors determine the hydrological cycle and affect various ecosystems in the region, and prompt site-specific responses of tree growth to local temperature and precipitation regimes (Boninsegna et al 1989; Llancabure 2011; Lara et al 2015; Soto-Rogel and Aravena 2017)

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