Warming may extend tree growing seasons and compensate for reduced carbon uptake during dry periods

1. Warming and drought alter plant phenology, photosynthesis and growth with important consequences for the global carbon cycle and the earth’s climate. Yet, few studies have attempted to tease apart their effects on tree phenology, particularly leaf senescence, and on source and sink activity.
2. We experimentally assessed the single and combined effects of warming and reduced soil moisture on the phenology (leaf-out and senescence date, growing season length) and aboveground sink (height and diameter growth, leaf area and Huber values) and source activity (net photosynthesis, photosynthetic efficiency, chlorophyll concentration and total carbon (C) uptake) of two tree species with distinct strategies to deal with drought: European beech and pubescent oak.
3. Warming advanced leaf-out, irrespective of soil moisture levels, particularly in oak and to a lower extent in beech, leading to a prolonged growing season in oak but not beech. No impacts of warming on senescence timing were found...