Interannual variations in primary and secondary growth of Nothofagus pumilio and their relationships with climate

Abstract

The relationships between apical (or primary) and radial (or secondary) growth, and climatic influences on both types of growth, were evaluated for Nothofagus pumilio (Nothofagaceae), the dominant subalpine tree in Patagonia. We measured the spacing and number of nodes of annual shoots developed in the period 2001-2010 in 40 N. pumilio trees growing near the upper treeline in the northern Patagonian Andes (41ºS). Variations in ring width at the base of each trunk were also recorded. Interannual variations in primary and secondary growth were significantly related to each other, and to several climate variables. Mean temperatures in winter and early spring (June to October) prior to the period of shoot extension were positively associated with both primary and secondary growth. In addition, total summer precipitation (December to March) was positively related to shoot extension, whereas mean summer temperature during the previous growth season (January to March) was directly related to radial growth. These climatic influences on N. pumilio growth may play a major role in regulating the expressions of preformation and neoformation.