Variation in Drought and Thermal Tolerance in Quercus douglasii and Quercus agrifolia

As climate change increases the intensity of hot droughts, understanding how tree species respond is crucial for effective conservation. Osmotic traits (e.g. turgor loss point, TLP) provide insight into drought tolerance, while thermal tolerance traits (e.g. the temperature at which 50% of photosynthesis is lost, T50) explain how plants cope with increased heat. While theory predicts a correlation between drought and heat tolerance, given their typical co-occurrence, this covariation remains unstudied in California oaks. I analyzed the relationship between drought and thermotolerance in Sedgwick Reserve’s blue (Quercus douglasii) and coast live (Quercus agrifolia) oak across a predawn water potential (soil moisture) gradient. I observed a species-specific tradeoff in the flexibility of drought and thermotolerance traits, with more hydrated trees showing lower thermotolerance. This insight into multi-stress responses facilitates a more informed approach to support ecosystem resilience.