Environmental Science
articles by Will Kemp

Changes in the population structure of Acacia papyrocarpa (western myall) in chenopod shrubland in South Australia


The arid chenopod shrublands of South Australia have been heavily degraded by sheep grazing since the 19th century. Acacia papyrocarpa is an ecologically important tree in these communities. It is habitat for many species of animals and plants which are not found in the open, it also plays an essential role in nutrient cycling and local hydrology. A. papyrocarpa is a very long lived tree – with some individuals possibly living as long as 1000 years – and recruitment occurs extremely slowly, depending on climate events which occur only a few times a century. Mainly due to grazing by sheep and rabbits, senescent trees are not being replaced by seedlings at a fast enough rate to maintain the population, and the tree and its associated ecosystems are threatened. We counted A. papyrocarpa, assigning individuals to one of nine age classes, and compared the age class distributions with a similar study which was carried out in 2000. This study appeared to show that these populations of A. papyrocarpa have begun to slowly recover. It is not clear what the cause of this recovery is – or even if such a recovery is, in fact, taking place – but, if it is, it may be related to reductions in the rabbit population due to the introduction of myxomatosis in the 1950s and calicivirus in the 1990s. Read the rest of this entry »