Macquarie researchers study extreme rainfall effects

Australian scientists are studying how plants worldwide will respond to more extreme rainfall in a future affected by climate change. They report that impacts will vary greatly across regions, meaning potentially dramatic disruptions to plant growth. This changed timing of rainfall may impact grasses and crops, with different rooting depths to trees, in different ways.

Because extreme precipitation, or changed timing of precipitation changes soil water content, this is likely to affect plant growth. This means food production, forestry industry, biodiversity and carbon and water cycles may also be affected, depending upon the region, and soil types.  Interactions with pests and pathogens, and invasive species may also be influenced by extreme precipitation changing soil water content.
Dr Melanie Zeppel and Jessica Wilks of Macquarie University, Sydney, in an international collaboration with Professor James Lewis, Fordham University, New York, conducted a global review of how plants respond to extreme precipitation in different ecosystems around the planet, such as dry grasslands, woodlands, warm humid tropical rainforests, savannas, as well as cold deserts. Their paper is published in Biogeosciences.
Dr Zeppel says that seasonal changes to rainfall “may have significant effects on plant water stress and growth rates.”
Despite the fact that we are seeing more intense droughts, storms and floods, yet we don’t currently know how many plants, particularly deep-rooted trees, will respond to this changed timing of precipitation.
“Knowledge of how plants respond to extreme precipitation is essential to understanding plant responses to future climates. This inspired us to examine the current state of knowledge.
“CSIRO and the Intergovernmental Panel on Climate Change (IPCC) agree that in future we are likely to experience more extreme weather, with many regions receiving intense droughts, floods, as well as hotter heat waves and bush fires.
“Even if the amount of rainfall within a year stays the same, in future, rain is likely to fall in more intense and ‘extreme’ rain events. That means rather than many, small rain events, we are likely to experience, fewer, more heavy rain events,” she says.
Precipitation may also shift seasons, for example, with more falling in Autumn, and less falling in Spring.
Consequences included delayed flowering, significantly less fruit production, smaller plant size and mortality in some regions and soil types, with plants in other regions growing larger.
“We were excited to find some intriguing results. In certain low rainfall regions, extreme precipitation caused growth rates to go up, whereas in wetter regions, extreme precipitation caused plant growth to decrease. It will be fascinating to see if this pattern holds across different ecosystems, and whether there is a threshold, above which changed precipitation timing causes plant growth to decline.”

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