Adaptation tipping points for fruit trees

Adaptation tipping points for fruit trees

Photographer: Liese CoulterBackground

Fruit tree orchards are particularly vulnerable to climate change, with changes likely to affect variables on which orchard productivity is reliant such as cold winter temperatures and extreme summer heat. In order to best prepare for climate change, the fruit tree industry needs targeted information on likely climate impacts and suitable adaptive management options. However there is little baseline physiological data against which impacts and adaptation can be evaluated.

This project is collating field information on key physiological phases of fruit trees (see diagram below) across the major growing regions of Australia. Physiological data sets are being used to evaluate lead times until key physiological thresholds (or tipping points) are crossed under future climates, and to measure the efficacy of adaptation options in managing these impacts.

The research will increase the Australian fruit tree industry’s preparedness for climate change, providing region-specific information on the lead times available to implement adaptive management strategies that moderate anticipated climate change impacts.

Project outline

Researchers are collecting physiological data on apple, pear and cherry in southern Queensland, northern Victoria, southwest Western Australia and southern Tasmania. The project is focused on four temperature-reliant processes that affect fruit productivity: winter chilling, spring flowering frost risk, summer extreme heat exposure and potential yield.

Field phenology and climate data are being collected for use in physiology models, alongside future temperature projections, to determine physiological thresholds, lead times until tipping points and the effect of implementing adaptation options.

Adaptive measures under evaluation include chill-breaking chemicals, the effect of rootstock choice and netting. Each option is being assessed, via model simulations, for their ability to delay adverse climate impacts, and then the lead times to tipping points will be re-analysed with the adaptation option in place.

Results to date

The research team have collected physiological and climate data for several seasons. Initial findings indicate that flowering at the Western Australian sites was noticeably delayed, suggesting a climate warming signal is already present in that region.

Modelling of future impacts on key fruit tree physiological processes has indicated that the future incidence of sunburn damage for Royal Gala apple will increase in some of Australia’s warmer growing regions. However simulations show that the risk of damage can be halved in some locations by installing netting.

Observational studies by the team have assessed temperature thresholds for sunburn damage in pears, with data collected via fine wire thermocouples showing damage manifests when fruit surface temperatures exceed approximately 47.1°C.

Another element of the project is looking to more accurately predict flowering timing so that climate change impacts can be forecast with more confidence. The team has constructed a flowering model for Pink Lady® apple that better explains the observed flowering patterns than a widely applied method. It is the first time this more dynamic modelling approach has been applied to apple and in the southern hemisphere.

Next steps

Activities to be completed over the remainder of the project include:

  • Evaluating winter chilling requirements for seven apple and one cherry variety using controlled environment chambers
  • Estimating the risk of insufficient winter chill accumulation due to climate change at key Australian production areas for seven fruit and nut varieties
  • Projecting the flowering timing of Pink Lady ® apple in Australia under climate change conditions
  • Presenting the results of netting as an adaptation option to the national conference Greenhouse2015
  • Conducting a global assessment of flowering phenology models for ‘Golden Delicious’ apple.

Related resources

Titlesort descending Excerpt
Adaptation tipping points for fruit trees publications A bibliographic survey of research publications produced by the Adaptation tipping points for fruit trees project.
Diagram: perennial fruit tree annual cycle                                                      
Winter chill and fruit trees fact sheet Fact sheet produced by Dr Rebecca Darbyshire through her research in the PICCC project Crossing the threshold: adaptation tipping points for Australian fruit trees.

Related media

Headline Source Published
Fruit surface temperature and sunburn damage of red-blushed pears Apple and Pear Australia Limited website 5 November 2015
What's the blooming difference? Apple and Pear Australia Limited website 24 October 2014
Climate researchers says profitable fruit production safe from climate change for another 50 years ABC Rural 25 August 2014
Fruit trees unlikely to warm to recent weather Apple and Pear Australia Limited website 4 June 2014
Why Australia's endless summer is bad for trees, fruit, insects – and shops The Guardian 28 May 2014
A chilling year: was 2013 a low winter chill year? Apple and Pear Australia Limited website 28 March 2014
State first netting trail tests heat impacts ABC Rural 17 March 2014
Protecting fruit trees from the heat Bush Telegraph, ABC Radio National 3 February 2014
Growers act to protect their fruit from the heat Tom Arup, Environment editor, The Age 18 January 2014