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Abstract: Using large-scale open-top chambers to approximate the thermal regimes of the Barossa Valley in the next decades, we measured yield and vegetative growth of grapevines in three factorial field experiments combining two thermal regimes (elevated temperature vs. control) with: two water regimes (experiment 1), two source:sink ratios generated by manipulation of fruit load (experiment 2) and four varieties (experiment 3). Water regime, source:sink ratio and varieties are sources of variation typically embedded in climate change studies using time series. Yield of controls ranged from 1.2 to 10.5kgvine−1. Warming had asymmetric effects on fruit yield and fruit/pruning weight ratios: yield response to elevated temperature varied from 46% reduction to 177% increase in relation to controls, and the response of fruit/pruning weight ratio varied from 56% reduction to 145% increase. Yield response to temperature was primarily explained by the response of bunch number (r 2 =0.92, P <0.0001). The effect of elevated temperature on fruit/pruning weight ratio was closely related to the response of fruit yield (r 2 =0.79, P <0.0001) and unrelated to the response of pruning weight (P =0.18). Elevated temperature reduced concentration of starch in trunks but not in roots. We conclude that the asymmetric responses of yield and fruit/pruning weight ratios resulted from seasonal influences on warming effects, whereby the largest responses of these traits were mediated by the promotion of bunch formation following relatively low temperatures in the preceding season. This highlights the need to assess warming effects in the light of both the background temperature and the distribution of thermally contrasting seasons in particular locations. Lower source:sink ratio and reduced starch concentration in trunks are two important elements of the carbon balance of the vine with long-term physiological and viticultural implications. [Copyright &y& Elsevier]

Winter crops are the backbone of Australian agriculture. This study reports the first comparative analysis of the impact of temperature and water stress on yields of wheat, barley, canola, chickpea and field pea across four major production zones in Australia (North, East, South and West) using the 2009-2013 National Variety Trials (NVT). Developmental windows of 100 °Cd centred at flowering were used to sample rainfall, vapour pressure deficit (VPD), potential evapotranspiration, water supply/demand ratio, average minimum (Tmin) and maximum (Tmax) temperature, number of days below 0 °C and above 30 °C, incident radiation, photothermal quotient (PTQ) and PTQ corrected by VPD. Flowering was estimated for a mid-season cultivar for each trial using a simulation model (APSIM). There was a consistent negative association between Tmax and yields in all crops, from early in the season in the South and after flowering in the West. Our study supports that high temperature in the non-stressful range is associated with yield reduction with crop specific effects. Days exceeding 30 °C were unlikely before flowering; wheat and chickpea were sensitive to temperatures above 30 °C from early and late in grain filling respectively. Chickpea was sensitive to low temperatures from flowering. Canola was overall the most sensitive to water stress. Unequivocally, the interaction between temperature and water stress exhibited strong regional differences. In the West, with Mediterranean rainfall pattern, high Tmin before flowering was associated with higher yields in wheat, barley, canola and chickpea, indicating a role in promoting early growth and water use and reducing evaporation. In the North, crops depend on initial soil moisture, and high yields were associated with lower Tmin, likely slowing growth and early water use and lessening terminal stress. These relationships need direct experimental confirmation to show causality but there is room for large scale studies to uncover seasonal and regional patterns and highlight targets for research, breeding and management options aimed at improving yield under climate change. [ABSTRACT FROM AUTHOR]