A DOMINANT FAST GROWING TREE TODAY, WILL ALWAYS BE A FAST GROWING TREE?

RODRIGUEZ CATON, M.; VILLALBA R.; SRUR A. M.; MORALES MS

Melboun

Conferencia; 9th International Conference on Dendrochronology; 2014

The growth patterns associated with tree decline and mortality were studied in 11 stands of Nothofagus pumilio in relatively dry forests in the northern Patagonian Andes. The dominant patterns of growth, based on ring width and basal area increment, were determined using principal component analysis. In most of the studied sites, three dominant patterns of growth were identified: (1) trees with high rates of growth until the mid-20th century showed a sustained reduction reaching the lowest increments in the late 20th century; (2) trees with intermediate growth rates until mid-20th century showed a subsequent 20-30 year period with high rates of growth followed by a gradual reduction to present; (3) trees with low growth over most of the 20th century substantially increased the growth rates concurrent with the growth decline in the previous twogroups. Changes in growth rate patterns were associated with the occurrence of major droughts in the years 1943-44, 1956-57, 1979 and 1986. Our studies show that droughts induced changes in the dominant patterns of radial growth among individual trees in the Nothofagus pumilio stands. Contrary to what is expected, dominant trees with high rates of growth seem to be the most affected by droughts. These results are consistent with the concept of ?decline disease stabilizing selection? proposed by Manion (2003) where healthy dominant fast-growing trees in the forest are selectively killed by a combination of specifically ordered factors. Processes that selectively enhance competitive dominant trees may also lead to increased vulnerability of these trees to decline and death following short-term inciting events such as droughts.