Regeneration failure, fire, topography, and climate interact to drive temperate wet forest landscapes into fire traps

Where early successional forests are more flammable than old‐growth forests, forested landscapes are vulnerable to shifting into ‘fire traps' through positive feedbacks, where fire leads to more fire. These feedbacks are amplified by increased flammability driven by climate change, the presence of non‐native flammable plant species, and slowed regeneration due to herbivory or dispersal limitation. In simulated landscapes with topographic variation, gullies act as refugia for older vegetation, modifying successional trajectories. Previous studies in Aotearoa–New Zealand have shown that fire, seed and seedling predation, and herbivory can interact to drive warm‐temperate forest landscapes toward states dominated by flammable, early‐successional vegetation (fire traps). We build on those previous studies, using a spatially explicit state‐and‐transition model to evaluate how topography and climate affect succession rates and the risk that landscapes could become fire traps. We also used the model to evaluate whether and how interactions among topography, climate, non‐native mammalian herbivores, and non‐native plants influenced the rate of succession. Although increased fire frequency was sufficient to drive landscapes into fire traps, non‐native mammals intensified these effects by slowing regeneration and prolonging the period that vegetation remained in a high flammability, early successional state. Invasion by flammable, fire‐adapted non‐native woody species was favoured by frequent fire, and their presence further amplified positive fire–vegetation interactions. Interactions between fire regime and landscape context, such as the nature of the surrounding landscape mosaic, can further intensify these feedback dynamics. Ecosystem changes that are driven and reinforced by positive feedback dynamics challenge restoration efforts. Minimising the risk of warm temperate rainforest landscapes tipping into fire traps will require managing them through vulnerable flammable early successional communities as quickly as possible by 1) suppressing fire during this period and 2) minimising the effects of stressors that impede regeneration.