A cocktail of masting, tree growth and climate in xeric-related forest environments with Araucaria araucana in northern Patagonia, Argentina

HADAD MARTÍN; ROIG FIDEL

Conferencia; Ameridendro 2016 Third American Dendrochronology Conference; 2016

Many plant species exhibit the so-called phenomenon of mast seeding year (mast year) in which much more mast than usual is produced. Since a masting may be highly temporal synchronized among individual plants and regions, we compared a regional mast production record with tree growth, as represented by tree-ring chronologies derived from female and male trees placed at five distant forest stands of A. araucana in the northwestern Patagonian lands of Argentina. Our objective was 1) to study differences in cumulative ring growth between sexes; 2) to evaluate the presence of trade-offs between tree growth and mast years and 3) to find relationships between female and male tree-ring chronologies with possible environmental-related climate triggers, such as the El Niño index. Recognized regional mast years were 1988, 1991, 1995, 2000, 2004, and 2007. The masting year was identified by two components: the year in which the seeds complete their formation and fall (t-0), and the previous year where fertilization and early seed formation occurs (t-1). With the combination of this background we observed the following: 1) cumulative growth between male and female trees were similar through their lives; 2) from a superimposed epoch analysis, female trees show a negative and significant relationship of their xylem growth at the filling cone year (t-0), while male trees show a negative but not significant relationship in the t-1 year; 3) correlations between tree-ring chronologies and El Niño 3.4 show an inverse and significant (p < 0.05) relationship among the months corresponding to the prior period of growth (October, January, March and April) in female tree growth while male trees do not showed significant correlation in any month analyzed. In summary, at inter-annual resolution tree growths of both sexes are similar. However, at intra-annual level, female trees showed a different growth response than male trees, a fact that can be interpreted as a trade-off between seed production and tree growth during mast years, which in turn may be influenced by the more than annual average precipitation in northern Patagonia during an El Niño year