The Potential of Deep Roots to Mitigate Impacts of Heatwaves and Declining Rainfall on Pastures in Southeast Australia

• Published in: Plants (Basel) Vol. 10; no. 8; p. 1641
• Main Authors: Meyer, Rachelle, Sinnett, Alexandria, Perera, Ruchika, Cullen, Brendan, Malcolm, Bill, Eckard, Richard J
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 10-08-2021; MDPI
• Subjects: Adaptation; Climate change; climate impacts; Climate models; Dormancy; Drought; Drying; Economic analysis; Economic models; Energy intake; Geographical distribution; Growing season; Heat; heat stress; Heat waves; Opportunity costs; Pasture; pasture systems; Pastures; Rain; Rainfall; Root distribution; Roots; Seasons; Soil profiles; Soil properties; Species; System effectiveness; Trends; Australia; heat stress; adaptation; climate impacts; drought; pasture systems
• ISSN: 2223-7747; 2223-7747
• DOI: 10.3390/plants10081641

Declines in growing-season rainfall and increases in the frequency of heatwaves in southern Australia necessitate effective adaptation. The Sustainable Grazing Systems Pasture Model (SGS) was used to model the growth of three pasture species differing in root depth and root distribution under three different climate scenarios at two sites. The modelled metabolisable energy intake (in MJ) was used in a partial discounted net cash flow budget. Both the biophysical and economic modelling suggest that deep roots were advantageous in all climate scenarios at the long growing season site but provided no to little advantage at the short growing season site, likely due to the deep-rooted species drying out the soil profile earlier. In scenarios including climate change, the DM production of the deep-rooted species at the long growing season site averaged 386 kg/ha/year more than the more shallow-rooted species, while at the site with a shorter growing season it averaged 205 kg/ha/year less than the shallower-rooted species. The timing of the extra growth and pasture persistence strongly influenced the extent of the benefit. At the short growing season site other adaptation options such as summer dormancy will likely be necessary.