A significant increase in forest regeneration failure following logging is driven by climatic and management factors

Regeneration following disturbance is a key natural process in forests worldwide and understanding the factors influencing it is critical to forest management. Here, using satellite data, historical logging data (1980-2019), and on-ground surveys, we quantified the spatial and temporal extent of regeneration failure following logging in the Eucalyptus forests of south-eastern Australia. We asked: What is the spatial extent and distribution of regeneration failure? Has the prevalence of regeneration failure changed over time? And, what climatic, topographic and other factors influence regeneration failure? We found that 19.2 % of areas logged between 1980 and 2019 in our study area (8030 ha of 41,819 ha cut) were characterized by regeneration failure. There was strong evidence of a significant increase in the extent of failed regeneration over the 40 years of our study, increasing from an average of <2 ha per cutblock in 1980 (∼7.5%) to an average of >9 ha per cutblock in 2019 (∼85%). The rate of change in regeneration failure also has increased. Regeneration failure was greatest on cutblocks with particular attributes including those: (1) with a high edge-area ratio (corresponding to long narrow logged areas), (2) on steep slopes, (3) at low elevation, and (4) dominated by Mountain Ash (Eucalyptus regnans) forest compared to other species (e.g. Alpine Ash [Eucalyptus delegatensis]). Our results suggest that attempts to regenerate forest cover in some areas may become challenging after logging, including cutblocks on steep slopes that experience comparatively drier conditions.