Cambial activity, phenology and climate in Nothofagus pumilio forests of Tierra del Fuego, Argentina.

ROIG F; MARTINEZ PASTUR G; MOYANO V; PINEDO L; LENCINAS MV

Québec (Canadá) 22-27 Agosto

Conferencia; Sixth International Conference on Dendrochronology; 2002

International Union of Dendrocronologhy

Although some information related to phenology of the southern Andes deciduous forests exists, no links between the phenological behavior and the cambial activity have been made. Timing of ring formation is important to better interpret the tree-ring growth-climate models, traditionally outlined through statistical procedures. This study represents preliminary observations undertaken through the 2001-2002 period about the timing of the leaf budding, foliage color change and cambial phases in Nothofagus pumilio trees distributed along an altitudinal transect in Tierra del Fuego, Argentina. For cambial analysis five trees per plot were systematically sampled fortnight at breast height with an increment puncher. Phenological observations were undertaken twice a month in ten trees per plot. Air and soil temperatures and relative humidity are presently recorded at each plot in order to relate changes in phenological and cambium status with climate. Results indicate that at any altitudinal plot the initial surge of earlywood passed after the first-formed leaves are fully expanded. Later, the cambium becomes most active after the foliage reaches its full development. Except for the tree-line environment, where cambial activity ceases shortly before the appearance of the first manifestation of leaf color change, a month or more may elapse between the latewood formation and the beginning of the autumnal phenophase. The model described point out the delay of the water-conducting tissue formation in relation to the moment of leaf emergence. The influence of altitude is expressed in the delay of the onset of both the initial stages of leaf swelling and the re-activation of cambial divisions as well as of the shortening of the vegetative growth period. While at lower elevations the cambium remains active for 4 months, at the tree-line environments this activity is reduced to two months. We hope this routine study will help to understand better the behavior of the ring formation and to improve our present knowledge of the growth-climate interactions of the South-American beeches.