Climate change impacts on phenology and yield of Hazelnut in Australia.

The growing demand for nuts and the required diversification of supply are urging to identify additional zones for hazelnut tree cultivation around the world. Given the long-term nature of the investment needed to establish new orchards, an ex-ante evaluation of the future production trends due to global changes is critical to support stakeholders and decision makers. With this motivation, we investigate the physiological response and the attainable yield of hazelnut in Australia, using a process-based model. Simulations examined phenological development, hazelnut growth processes and yield in recent past and near-future climate conditions, using an ensemble of regional climate models bounded by four global climate models (GCMs). While the entire domain of analysis will warm up in the next twenty years, the precipitation patterns are rather erratic across GCMs. The effect of climate change on hazelnut farming is variable across agro-climatic zones, except in the southeast­ ernmost part of Australia, where all simulations agree in predicting a yield increase ranging from 18 to 52%. Elsewhere the hazelnut production potential varies, with some GCMs projecting yield increase and others esti­ mating reductions or no significant changes. Yield increase is associated mainly with higher gross assimilation rates, whereas decrease is related to a delay in chilling requirements fulfilment, caused by the projected increase in minimum temperatures and to sub-optimal conditions for the photosynthetic process. Despite the need of additional field trials to further validate the model, these results may be used by private and public bodies to support new investment plans, and promote legislative measures aimed at encouraging hazelnut cultivation in Australia.

Figure 4. The box plots show yield in future (2020–2039) and recent past (1990–2009) climate for different agro-climatic zones. The quadrants show changes in hazelnut yield (future – present climate) according to the climate input projected by various GCMs (marked by numbers 1, 2, 3 and 4) in different agro-climatic zones. The diameter of the spheres represents the magnitude of increase (shown by green color) or decrease (shown by red color) in yield. The position of the spheres in X and Y axes represent their relative position with respect to the change in temperature and precipitation.