The effects of slash burning on the mortality and collapse of trees retained on logged sites in south-eastern Australia

Trees may be retained on logged sites in eucalypt forests for a number of r easons, such as to provide wildlife habitat, for future wood production, fo r aesthetic reasons, to mitigate erosion, or to provide seed for regenerati on. These trees may be required to survive for a considerable period to mee t these objectives. Logged sites in eucalypt forests are routinely treated with a post-logging slash-burn to reduce fuel loads and facilitate regenera tion. We compared rates of mortality and collapse among trees retained on l ogged sites that were routinely treated with a high-intensity slash-burn wi th logged sites routinely treated with a low-intensity slash-bum. All obser vations were made 2-5 years after logging. The proportion of all retained t rees that were killed after logging was 37% on sites treated with a high-in tensity slash-bum and 14% on sites treated with a low-intensity slash-burn. The rate of collapse among retained trees over the same period was 1.5 and 0.5%, respectively Results of logistic regression models indicated that tr ees retained on logged sites were more likely to die and collapse if the si te was treated with a high-intensity slash-bum; however, trees were also mo re likely to die if the basal area of trees retained on the site was relati vely low and the site had a northerly aspect. Mortality was similar among a ll diameter classes on sites treated with a high-intensity slash-bum. Some of the objectives of retaining trees on logged sites, such as perpetuating hollow-bearing trees for wildlife, may be compromised where high-intensity post-logging slash-burns are employed. (C) 2000 Elsevier Science B.V. All r ights reserved.