Cold sensitivity of Casuarina cunninghamiana (Casuarinaceae) saplings

Abstract

The Australian tree, Casuarina cunninghamiana Miq. (Casuarinaceae), is widely planted for agroecosystem and other benefits, and belongs to a family (sheoaks) with wide adaptation and tolerance to environmental extremes. However, extreme cold as a stressor is not common on the Australian continent, so compared to heat and drought, less work has been done on the cold tolerance of Australian flora. Therefore, saplings of C. cunninghamiana were exposed to 0 to 4 months of extreme winter temperatures below -5°C to about -15°C over 2 years in Niğde, Central Anatolia, Turkey to test their cold sensitvity. Damage was severe, however, most plants exposed to 1 or 2 months of the milder temperatures (down to -5°C) at the beginning of winter recovered. Four months exposure killed all the plants. However, even the milder, early-winter conditions are unlikely to be suitable for the long-term productivity or survival of C. cunninghamiana and perhaps all members of its family. The risk of extreme cold needs to be considered when planting sheoaks beyond their native range.

Cold Sensitivity of Field-Grown Allocasuarina and Casuarina Tree Species

“…Much of the Australian flora is endemic and the continent, although having some areas with annual snowfall, temperatures do not normally fall below about −8°C (Riley and Saygı 2021a). Therefore, although the tolerance of Australian flora to many environmental stressors is well known, there has been limited assessment of tolerance to extreme cold.…”

“…In the field, there is a single report of frost damage to C. cunninghamiana in plantations in California, USA (Merwin et al 1995). There have also been studies on the effect of freezing on seed release in a range of species (Riley and Saygı 2021a) and containerised sapling survival with C. cunninghamiana (Riley and Saygı 2021b). Therefore, for this study, plants of 10 accessions including six species of Allocasuarina (2 species) and Casuarina (4 species) were established in the field in Niğde in Central Anatolia, Turkey and their growth and survival monitored over 1.5 years, using the local species, Elaeagnus angustifolia (F. Elaeagnaceae), as a comparator.…”