Abstract:

Nothofagus species are constitutive elements of the temperate forests along the Southern Andes Mountains. The deciduous Nothofagus alpina is a fast-growing, but long-lived opportunistic pioneer species (‘pioneer-climax species’) and co-occurs with the evergreen N. dombeyi. We tested whether N. alpina is competitively superior to N. dombeyi in mature stands and whether intra-specific competition in N. alpina is stronger than inter-specific competition with N. dombeyi.

In a pristine old-growth forest in South-Central Chile, we compared the growth of N. alpina trees in pure stands and in mixture with N. dombeyi to the growth of N. dombeyi and calculated competition indices. We related growth variables to climate data and weather extremes.

In N. alpina, juvenile basal area increment was significantly higher in pure than in mixed stands. Contrary to our hypothesis, N. dombeyi exhibited larger radial stem increments than N. alpina in the most recent 40 years. In the most recent two decades, this was caused by high growth rates of large N. dombeyi trees. In both Nothofagus species, stem growth was negatively related to temperature, but N. dombeyi responded more sensitively to weather conditions than N. alpina. In N. alpina, stem increment was negatively related to the intensity of competition, but the size of the competition effects on this species was similar in pure and mixed stands. Thus, compared to N. alpina, the ‘pioneer-climax species’ concept is even more appropriate for N. dombeyi with its relatively high growth rates even in the early stages of its life.

Key words: competition index, dendroecology, growth–competition relationship, pointer year, productivity, tree-ring analysis