Identifying spatial and temporal variations in tree growth within subtropical montane forests in South America

FERRERO, M.E.; VILLALBA, R.

Corvallis OR, USA

Workshop; PAGES 1st Young Scientists Meeting; 2009

Climate modulates tree growth at large spatial scales; however topographic position can locally induces different growth responses. Subtropical montane forests in South America afford the opportunity to study the climatic influences on tree growth and how site location influences growth pattern in the same species. The subtropical montane forest in NW Argentina occupies a narrow strip (22-28º S; 66-68º W) of very diverse environments: from the warm, dry sites of the lower woodland transitional ecotone to the moist, cool sites at upper tree line. Tree-ring chronologies allow us to characterize the relations between woody growth and climatic variations across these diverse environments. We describe differences in temporal patterns of radial growth of Juglans australis between sites, and relationships between these growth patterns with temperature and precipitation are also determined. Based on the similarity in tree-growth response to climate, thirty-four J. australis chronologies were merged in composite chronologies to enhance the regional climatic signals present in the tree-ring records. Principal Components Analysis (PCA) was used to identify spatial and temporal patterns of growth. Climatic records of temperature and precipitation from 32 stations distributed across the region were used to examine the relationships between climate and tree-ring growth patterns using correlation analysis. By identifying the mayor climatic factors controlling the variability of these sensitive tree-ring records, we will be able to develop the first reconstructions of long term climatic variations in the subtropical montane forests in South America.