Growth patterns of Nothofagus pumilio trees along altitudinal gradients in Tierra del Fuego, Argentina

Abstract

The influence of ecological factors resulting from altitude on the growth characteristics of Nothofagus pumilio was analyzed. Nothofagus pumilio forests grow in the southern Andes from near the sea level or the valley bottoms to 600 m.a.s.l. Eight study sites were selected in the southwestern area of Tierra del Fuego, on both north- and south-facing slopes, and distributed along an altitudinal gradient between 200 and 600 m.a.s.l. Tree-ring analysis was conducted on wood samples extracted with increment borers. Exactly dated tree-ring measurements were standardized to construct ring-width chronologies. Correlation analysis of the ring-width chronologies, monthly mean temperatures, and net precipitation data were used to determine the relationships between climate and tree growth. Some chronology statistics were more variable for slope aspect than for altitude. For example, south-facing slopes showed higher values in common growth variability, probably because of stronger climatic controlling factors over growth (e.g. lower temperatures). Climate-growth correlation models revealed long-term temperature influences on growth variability at every altitude considered. However, there were variations among the different plots. There were obvious differences in the spectral power component of the chronologies throughout the altitudinal profile. These results suggest a strong altitudinal component in the growth variability of Nothofagus pumilio in Tierra del Fuego. These variations should be taken into consideration in the development of sampling strategies for ecological and paleoenvironmental studies.