Pines grow faster and are more drought resilient in the Southern Hemisphere.

Abstract

Drought-induced conifer mortality is a global concern¹, yet conifers native to the Northern Hemisphere that have been planted at massive scales in the Southern Hemisphere do not appear to show the same magnitude of growth decline or mortality as in their native ranges. Using a standardized dendrochronological survey at 192 sites across four continents, we find that Northern Hemisphere conifers grow up to four times faster in the Southern Hemisphere and are also more resistant and resilient to drought than conspecifics in native ranges, suggesting that non-native populations respond fundamentally different to abiotic stress. Conifers in non-native ranges had higher concentrations of non-structural carbohydrates, commonly associated with drought tolerance^2,3, and lower δ¹³C values, consistent with lower stomatal limitations on photosynthesis. In sum, higher concentrations of non-structural carbohydrate, lower δ¹³C values and higher stem growth rates all point towards higher net carbon assimilation by conifers in non-native ranges. This paradoxical combination of high growth rates yet resilience to drought emphasizes the importance of integrating eco-evolutionary history into ecological theory and is relevant for assessing the ultimate role of afforestation as global carbon sinks.