Interacting Fire, Logging and Climate Change has Sprung a Landscape Trap in Victoria’s Montane Ash Forests

Abstract

\n Ecosystems are influenced by multiple drivers which shape ecosystem state and biodiversity. In some ecosystems, interactions and feedbacks between drivers can produce traps that confine an ecosystem to a particular state or condition and influence processes like succession. A range of traps have been recognized, with one of these – “a landscape trap” first proposed a decade ago for the tall, wet Mountain Ash and Alpine Ash forests of Victoria, south-eastern Australia. Under such a trap, young flammable forest is at high risk of reburning at high-severity, thereby precluding stand maturation, and potentially leading to ecosystem collapse. These young forests are more common because recurrent wildfire and widespread clearcutting have transformed historical patterns of forest cover from widespread old-growth with small patches of regrowth embedded within it, to the reverse. Indeed, approximately 99% of the montane ash ecosystem is now relatively young forest. Based on new empirical insights, we argue that at least three key inter-related pre-conditions underpin the development of a landscape trap in montane ash forests. A landscape trap has been sprung in these forests because the pre-conditions for its development have been met: We show how inter-relationships between these pre-conditions, leading to frequent high-severity fire, interacts with life history attributes (e.g. time to viable seed production) to make montane ash forests (e.g. which have been highly disturbed through logging and frequent fire) vulnerable to ecosystem collapse. We conclude with the ecological and resource management implications of this landscape trap and discuss how the problems created might be rectified.