Morphological and phenological differences in Nothofagus pumilio from contrasting elevations:: Evidence from a common garden

We tested the hypothesis that contrasting elevations select distinct growth patterns and vegetative phenology in Nothofagus pumilio, a winter deciduous tree that dominates mountain forests of Patagonia. Analysis of saplings maintained under common-garden conditions for 4 years showed a significant decrease in shoot annual growth, leaf size, and a delay in bud-break, and leaf expansion with increased elevation of their site of origin. Rapid gain in height seems to be advantageous at low elevation in such light-demanding species. Lower stature high-elevation plants have wider branching angles and greater branching ratios (number of branches/number of internodes) than low-elevation plants. Compact growth at high elevation may be related to strong winds and irradiance. Plants from different elevations had distinct growth patterns during the common-garden experiment. This could be of importance in Mediterranean-climate areas characterized by highly unpredictable precipitation regimes. Also, liberation of growth-suppressed seedlings may follow different environmental signals in low- and high-habitats, which might explain such time-dependent responses to optimal conditions under cultivation. While these greenhouse-grown N. pumilio saplings showed heritable differences in plant architectural traits and leafing phenology, it was not clear how the genotypes characteristic of particular elevations would respond to longer growing seasons such as those predicted under global warming.