Endemic threatened tree species in the Mediterranean forests of central Chile are highly sensitive to ENSO-driven water availability and drought

The Mediterranean region in central Chile is experiencing a significant decrease in precipitation due to climate change and the dynamics of the El Niño Southern Oscillation (ENSO). Droughts have increased in recent decades, with the most severe and longest drought of the last millennium occurring since 2010 in central Chile. The impact of ongoing water scarcity is leading to significant drought-related declines in tree growth and forest dieback in the Mediterranean region. A deep understanding of how tree species respond to climate is crucial to accurately predict how forests will respond to climate change. We examined the growth responses to climate of three endemic and threatened tree species of the Mediterranean forests of central Chile, Nothofagus macrocarpa, Cryptocarya alba and Persea lingue, in a protected area. We observed that the growth of all three species was highly dependent on water availability and ENSO, and that the evergreen species C. alba and P. lingue increased their sensitivity to hydroclimate more than the deciduous species N. macrocarpa. These relationships were consistent across much of southern South America, highlighting the dependence of these species on water availability at large geographic scales. We found that there is a relationship between local water availability and ENSO that has intensified temporally and expanded geographically in recent decades. The xerophyllous species C. alba showed greater resistance and increasing resilience to severe droughts, while P. lingue and N. macrocarpa showed greater growth decline during droughts, possibly due to their preference for wetter environments. Our results highlight the crucial role of ENSO-driven water availability and drought in limiting tree growth and threatening the conservation of Mediterranean forests in central Chile.