Convergence in growth responses of tropical trees to climate driven by water stress

LÓPEZ, LIDIO; RODRÍGUEZ-CATÓN, MILAGROS; VILLALBA, RICARDO

ECOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2019 vol. 42 p. 1 - 14

0906-7590

Widely documented for temperate and cold forests in both hemispheres, variationsin tree growth responses to climate along environmental gradients have rarely beeninvestigated in the tropics. Seven tree-ring chronologies of Centrolobium microchaete(Fabaceae) in the Cerrado tropical forests of Bolivia are used to determine the growthresponses to climate along a precipitation gradient. Chronologies are distributed fromthe humid Guarayos forests (annual precipitation > 1600 mm) in the transition tothe Amazonia to the dry-mesic Chiquitos forests (annual precipitation < 1200 mm)in the proximity to the dry Chaco. On a large spatial scale, radial growth is positivelyinfluenced by rainfall and negatively by temperature at the end of the dry season.However, this regional pattern in climate-tree growth relationship shows differencesalong the precipitation gradient. Relationships with climate are highly significant andextend over longer periods of the year in sites with low rainfall and extremely severedry seasons. At wet sites, larger water soil capacity and endogenous forest dynamicspartially mask the direct influence of climate on tree growth. Stronger similarities intree-growth responses to climate occur between sites in the dry Central Chiquitos andin the transition to the Guarayos forests. In contrast, the relationships show fewer similaritiesbetween sites in the humid Guarayos. We conclude that growth responses toclimate in the tropics are more similar between sites with limited rainfall and severe andprolonged dry seasons. Our study points to a convergence in the patterns of growthresponses of tropical trees to climate, modulated by scarce rainfall and marked seasonality.The negative impact of water deficits on tree physiological processes induces notonly the documented reduction in forest species richness, but also a convergence intree-growth responses to climate in dry tropical forests