Growth dynamic of Alnus acuminata H.B.K. spp. acuminata (Andean Alder) in the mountain areas of Tucuman and Catamarca (Argentina)

Abstract

Growth and age of 123 individuals of Andean alder growing in 5 mountain localities (1,700-2,000 above sea level) were estimated employing the standard methodology of ring width measurement. Growth rate in the juvenile period (1-10 years) was fast (mean radial increment= 4.7 mm/year in the dry locality to 7.7 mm/year in the wet locality) but decreased markedly (mean radial increment= | to 1.4 mm/year), after 8-25 years. The size achieved by the best individuals growing in humid sites (ca. 40 cm d.b.h. in 20-30 years) suggests that A. acuminata could be an attractive forestry alternative in high rainfall mountain areas of NW Argentina. At drier sites growth rate was generally reduced and the initial fast growth period was considerably shorter. Trees older than 30 years maintain low to very low growth rates (0.2-4 mm/year). These values measured in the present study, combined with diameter data of previous studies suggest that individuals in the range of 150-300 years of age are likely to be found in the natural stands of NW Argentina. If this hypothesis is confirmed, A. acuminata could be as valuable as Cedrela and Juglans in regional dendrochronological studies, covering the last three centuries. Tree-ring variations from A. acuminata may be extremely useful to reconstruct climatic conditions in the mountains of NW Argentina, as it is more widespread than Cedrela and Juglans, and grows up to 3,000 m above sea level, far above the altitudinal range of these genera.