A new collaborative research project between Anangu, the Traditional Owners of Uluru, and plant scientists has uncovered the physiological traits that helped some species of desert plants survive a mass dieback event in Australia. These results reveal the key strategies for desert plant survival in the face of increasing extreme weather events, with consequences for the conservation of ecologically and culturally important keystone species.
A record-breaking hot drought from 2018 to 2019 caused widespread plant mortality in Uluru-Kata Tjuta National Park, Australia.
"Anangu were concerned about these impacts and wanted to know why important plants were dying," says Mr Jay Nicholson, co-author of the study published in Conservation Physiology. "This provided an opportunity to bring together Anangu knowledge of Country and a western plant physiology framework to better understand how culturally significant desert plants respond to extreme heat and drought."
The team surveyed nine species of desert plants over a mild-temperature spring season and an extreme-temperature summer season and measured a range of traits for each species. They focused on many of the keystone species in the Australian desert chosen by Anangu that provide food, habitats and materials for tools, including wanari (Acacia aneura, mulga), tjanpi (Triodia pungens, spinifex), and kurkara (Allocasuarina decaisneana, desert oak).
"These plants are part of the living cultural landscape that Anangu have cared for over millennia, so changes to their health have consequences beyond the plants themselves and extend to cultural practices and maintenance of knowledge," says Mr Nicholson.
To determine why some species were more likely to survive extreme weather than others, a range of physiological traits were analysed to determine their impact on chances of survival, including leaf measurements, leaf water content, and leaf carbon-nitrogen ratio.
The findings of this study reveal that plant species using drought-tolerance strategies tended to have higher dieback than those using drought-avoidance strategies.
Drought-tolerating plants can maintain growth during dry conditions, but risk severe dehydration under extreme drought. Drought-avoiding plants conserve water by reducing growth during dry periods, but prolonged drought can exhaust carbon reserves and increase mortality risk.
Maintenance of leaf-relative water content, a component of drought-avoidance, was the trait that best predicted dieback severity, with plants experiencing large reductions in leaf water content being the most vulnerable to dieback. However, neither strategy provided guaranteed survival under extreme drought and heat.
By studying ecologically and culturally important species, this research provides new insights into how plants that are important to Anangu respond to hotter droughts. This knowledge can help inform culturally appropriate approaches to caring for Country as the climate continues to change.
"The desert is often overlooked when we think about the impacts of climate change, with an assumption that desert plants are naturally equipped to withstand heat and drought," says Mr Nicholson. "Our findings show that even plants adapted to these conditions can be vulnerable when extreme heat and drought occur together, and that both drought-tolerating and drought-avoiding strategies can fail and lead to mass mortality."
This project has been driven by Anangu aspirations and demonstrates the invaluable benefits of scientific collaboration with Indigenous communities. "Anangu have co-developed research aims, selected study species and locations, conducted fieldwork, and interpreted and discussed our findings," says Mr Nicholson. "Working together has allowed us to weave Anangu knowledge of Country, plants, fire, and landscape change, with a western framework of plant physiology."
This study highlights several opportunities to reduce the impact of drought-driven dieback, including Anangu cultural burning and community plant nurseries. "Supporting local propagation and restoration of culturally significant plants through the community nursery is an opportunity to maintain cultural connections to plants and actively restore Country," says Dr Nicholson. "Ultimately however, reducing the long-term impacts of hotter droughts will require strong measures to halt and reverse anthropogenic climate change."
Conservation Physiology is an online only, fully open access journal published on behalf of the Society for Experimental Biology by Oxford University Press. The journal prides itself on serving the community of conservation physiology researchers through its publishing activities and wider initiatives.
This work was funded by Director of National Parks. This research was a collaboration between university scientists, Anangu and the Mutitjulu Community Mala Rangers, and Uluru-Kata Tjuta National Park and other Parks Australia staff; the input and collaboration of all partners were critical for its success.
