Thermal tolerance and growth responses to in situ soil water reductions among alpine plants

ABSTRACT

Background

Changes to precipitation patterns and warming temperatures are predicted to reduce the water available to Australian alpine plants during the growing season. Soil water deficits are likely to co-occur with frost extremes that are common throughout the year and heatwaves which are increasing in severity with ongoing climate change.

Aims

We aimed to determine whether co-occurring reductions in soil moisture would affect the capacity of alpine plants to tolerate temperature extremes.

Methods

We used small rainout shelters to impose a drought treatment in situ in the alpine zone, which chronically reduced soil moisture in plots of alpine plant species including evergreen shrubs, graminoids and perennial forbs. We determined photosynthetic freezing tolerance and heat tolerance during the growing season across 2 years, and measured plant growth, in response to the drought treatment.

Results

Thermal tolerance was insensitive to chronically reduced soil moisture, and graminoids exhibited overall greater freezing and heat tolerance thresholds than other life forms. The drought treatment improved shrub growth, likely due to the amelioration of wind and the slightly warmer temperatures provided by the rainout shelters.

Conclusion

We conclude that Australian alpine plants maintain high tolerances to both high- and low-temperature extremes during the growing season and are relatively robust to combined temperature extremes and reductions in near-surface soil moisture that are likely to occur with ongoing climate warming.

KEYWORDS:

• Alpine
• climate warming
• drought
• freezing tolerance
• heat tolerance
• plants
• Australia

Acknowledgements

Jeronimo Vazquez Ramirez and Irma Del Valle Nachon provided field and laboratory assistance. Mel Schroder and Andrew Miller assisted with site selection, accommodation and logistics within Kosciuszko National Park. Naomi Monk assisted with site access within the Falls Creek Resort. We thank two anonymous reviewers whose comments greatly improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/17550874.2022.2160674.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

EES was supported by a Deakin University Post-Graduate Research Scholarship, a Holsworth Wildlife Research Endowment, and a Parks Victoria Grant. This study was conducted under an Alpine National Park, VIC permit: 10008981 and Kosciuszko National Park, NSW permit: SL102188.