Half a century of demographic responses of Nothofagus cool temperate rainforests to disturbance

Abstract

Temperate rainforests have historically been considered highly vulnerable to disturbance. Climate change, which is expected to increase the intensity, frequency, and impacts of disturbance events, is consequently a significant threat to their long-term persistence. However, data describing the long-term response of temperate rainforests to disturbance is rare. In the cool temperate rainforests of northern New South Wales, Australia, Nothofagus moorei is considered especially vulnerable to climate change due to a decreasing number of mature individuals, limited remaining suitable habitat, and low rates of sexual regeneration. In this study, we used over 50 years of empirical data from silvicultural experiments with multiple thinning intensities to characterise the demographic responses (i.e., growth, mortality, and recruitment) of cool temperate rainforest species, including N. moorei, to disturbance over time. Cool temperate rainforest species showed resilience to disturbance, predominantly through their widespread ability to basally coppice. Nothofagus moorei, in particular, demonstrated higher rates of successful sexual and vegetative recruitment and grew faster in response to higher intensities of disturbance, in comparison to very low rates of recruitment pre-disturbance. These results challenge successional models that position rainforests as disturbance-sensitive ecosystems and identify N. moorei as a species that requires large-scale disturbance to successfully regenerate. Management regimes that actively exclude disturbance from these forests risk the local loss of disturbance-dependent rainforest species such as N. moorei.