Understanding the response of variability in tree reproduction (masting) to climatic and environmental change

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Background: Many tree species show a reproductive strategy known as masting, which is characterised by switching between years of bumper investment in reproduction ("mast years"), and years of low investment. Remarkably, this variation is synchronised within and across tree populations. Various mechanisms may explain how trees are able to a) vary their seed production year-to-year, and b) synchronise this variation between individuals. Most of these mechanisms rely either directly or indirectly on climate as the key regulator of masting, implying that masting may respond to changes in climate. However the response of masting to climate change remains highly uncertain. This is important because forest regeneration it strongly regulated by seed production, dispersal and predation, influencing species composition, recovery from disturbance and migration in response to climate change. These processes are all influenced by masting. For example, we have recently shown that when warming-driven increase in seed production is associated with a "breakdown" in masting, the benefits of increased investment in reproduction accrue largely in seed predators, rather than the plants. This example demonstrates how changes to masting patterns are of fundamental importance to the functioning and dynamics of forest ecosystems, including in a changing environment.Objectives: This project will establish the response of masting to recent changes in climate, and predict future changes in masting resulting from ongoing environmental change. A key objective will be establish whether the different physiological mechanisms that underpin masting in different species result in contrasting responses to environmental change.