It is increasingly acknowledged that fuelled by the forces of climate change, Australia is experiencing an increased frequency of severe fire events (NSWGov, 2026). This was well demonstrated by the unprecedented 2019/20 Black Summer megafires in Australia, burning vast areas of native forest at a high severity.
A key impact of high severity fire is the large-scale loss of mature foliage, which subsequently releases large volumes of epicormic foliage during recovery. Epicormic growth is the growth of new shoots from epicormic buds in response to damage or stress. Following significant fire events, arboreal folivore species including koalas, greater gliders and possums that feed primarily on leaves, may become reliant on epicormic regrowth for sustenance for extended periods of time while the forest recovers. While the rapidly sprouting nature of epicormic regrowth may make it appear that there is an abundance of food available, little research has been conducted on the nutritional quality of epicormic regrowth and the potential effects on the population recovery and health of arboreal species.
Study:
A 2026 study conducted in East Gippsland, Victoria, sought to quantify the post-fire change in the chemical composition of epicormic foliage, with the aim to facilitate a greater understanding of the impacts from fire induced canopy disturbance on surviving arboreal folivores (Wagner et. al.). Eucalyptus, the genera of trees that dominate Australian ecosystems, have two major strategies for responding to fire: obligate seeding, which involves fire-activated seed release, or resprouting. Resprouting trees contain epicormic buds within their tissues which allows the tree to regenerate vegetatively after fire or other stressors. This results in rapid leaf growth within the forest mid-story and canopy shortly after fire. The nutritional needs of arboreal folivores are likely adapted to the chemistry of mature, adult phase leaves. Mature leaves typically have a relatively high available nitrogen content, and low concentrations of plant secondary metabolites (PSMs), which are known to deter herbivores. However, little is known in regard to any potential nutritional differences occurring in epicormic regrowth.
Can epicormic foliage provide for arboreal folivores post-fire?
The study found that post-fire epicormic regrowth differs chemically from mature foliage. However, the degree of this variation is heavily influenced by both subgenus and species.
Epicormic foliage tends to have a higher nitrogen content when compared to mature leaves, but not higher concentrations of available nitrogen, which is influenced by other leaf constituents such as protein-binding tannins. For species that are less affected by insoluble tannin-protein complexes, increased total nitrogen content in epicormic growth will provide a short to medium-term dietary benefit. However, this benefit may be limited given the trade-off of consuming higher concentrations of PSMs.
Variations in PSM levels in epicormic growth were observed between the subgenus Eucalyptus (the monocalypts) and subgenus Symphyomyrtus (the symphyomyrtles). Symphomyrtle species displayed more consistent increases in the PSM concentrations of epicormic leaves when compared to mature leaves. This may consequently limit consumption and thus reduce the utility of epicormic foliage as a food resource, refuting any benefits of increased nitrogen content. However, in monocalypt species the epicormic growth contained reduced PSM concentrations when compared to mature growth. This suggests that this epicormic growth may be more palatable and thus support increased consumption post-fire. However, any potential effects of PSM level variations are highly dependent on the inherent PSM levels of the eucalypt species as increases in species with lower inherent concentrations may be insignificant. Similarly, fauna species with higher PSM tolerances may not be affected as much by PSM increases. Thus, the overall dietary impact of epicormic shoots compared to mature growth is heavily context driven and shaped by species composition within an area.
The study suggested that in forests with a mixed composition of monocalypt and symphomyrtle species, there may be increased foraging options that offer sufficient nutrition to support folivore populations after fire activity. However, the overall impact of epicormic shoots as a foraging resource is heavily context driven and shaped by the specific species composition within an area, as well as the individual dietary tolerances of affected folivores. Therefore, looking ahead, the conservation of threatened folivores will be enhanced by gaining an increased understanding of the specific species compositions of individual forests and the dietary niches of resident folivores.
Click here for the original article
This article was written by Elke Black, the Healthy Ecosystems Program Volunteer with the Nature Conservation Council of NSW.
Image from Flickr by Tessa Barrat
