Drought and heat can delay phenological development and reduce growth of semi-arid trees

With climate change, higher temperatures are expected to cause earlier and longer growing seasons, but drought could negate this effect. We measured responses of shoot development and growth in mature piñon pine to heat and drought in a field experiment over three years. Responses varied with annual precipitation. Heat either delayed, advanced, or had no effect on development, and either reduced growth or had no effect, but never increased growth. Drought either had no effect, or delayed development and reduced growth. Our results were often inconsistent with the climate change paradigm of earlier development and increased growth in semi-arid trees.