If you’ve ever been bushwalking in Australia you will have surely come across the damage caused by fire, whether it be the result of controlled burning or wildfire. In most cases the damage would have been relatively minor in comparison to that caused by the Black Saturday bushfires on 7 February 2009. The largest of the many fires burning on the day was the Kinglake complex, formed as the south-westerly wind change merged the Kilmore East (caused by fallen powerlines) and Murrindindi Mill fires. These fires were intensely hot; Melbourne had been suffering a heatwave having recorded three consecutive days above 43 degrees. On the 7th, temperatures peaked at 46 degrees with 100+ km/h winds from the north-west.
Small sections of the Kinglake National Park have been re-opened for public access, eight months after these fires destroyed 98% of it, including the office and most visitor facilities. Unlike the wildlife of the area, the trees didn’t have the opportunity to attempt escape but have however adapted to survive such an event. As featured in these photographs, the eucalypts have epicormic buds buried deep within their trunks. During normal growth, epicormic buds are inhibited from sprouting by hormones produced in leaves of the crown. If a fire is intense enough to remove all the leaves, the hormonal influence disappears triggering the epicormic buds to sprout thereby covering the entire tree in a new gown of leaves and branches. In a severe fire, the crown may be detroyed and even the epicormic buds on the smaller branches may be killed so the plant can only recover from the epicormic buds present on the main trunk.
Similar behaviour is exhibited by the grass-tree (Xanthorrhoea) with regards to its flowering being stimulated by fire. The fine example shown above has recovered to a flowering stage while the surrounding vegetation is struggling to make do in the seemingly now sterile topsoil. The dense and inflammable foliage surrounding the stem protect the apex of Xanthorrhoea from fire. Even though the trunk grows only a few centimetres in height per year, fire triggers rapid growth of the main shoot tip into a flowering spike. The spike grows at an average of 4 cm per day, attaining a maximum height of around 3 m in about 75 days.