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Divergent trajectories of regeneration in early-successional forests after logging and wildfire

Bowd, Elle1

Published Oct 04, 2024 on Dryad. https://doi.org/10.5061/dryad.9kd51c5n5

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Oct 04, 2024 version files 404.14 KB

Abstract

Increases in forest disturbances have altered global patterns of forest demography, with many regions now characterized by extensive areas of early-successional forest. Heterogeneity in the structure, diversity and composition of early-successional forests is often overlooked in ecological research. However, these sources of variability in early-successional forests can influence their inherent ecological values now and in later successional stages, including values for biodiversity and carbon storage. Here, using 14 years of longitudinal data, we describe temporal patterns in the structure, diversity, and composition of early-successional forests subject to different disturbance origins (clearcut logging, salvage logging and wildfire) and disturbance histories (short, medium and long disturbance intervals) in the Mountain Ash (Eucalyptus regnans) and Alpine Ash (Eucalyptus delegatensis) forests of south-eastern Australia. Our analyses revealed several key differences between early-successional forests that regenerated from wildfire versus anthropogenic perturbations. Most ash-type plant communities were resilient to wildfire within historical fire-regimes (75-150 years), exhibiting temporal trends of recovery within the first decade. In contrast, the diversity and abundance of some plant lifeforms and life-history traits were negatively associated with clearcut logging and salvage logging, relative to forests disturbed by wildfire alone. Taxa most affected were resprouting species, such as tree-ferns and ground ferns. However, some onsite-seeding species, including Acacia were more abundant after clearcut logging than after wildfire. Our findings also provide evidence of the pronounced and pervasive impacts of salvage logging on early-successional plant communities. Alarmingly, we observed several negative temporal responses in plant diversity after salvage logging. That is, diversity declined over time after salvage logging, rather than increased as occurred following other disturbance types. Early-successional forests provide the template from which mature forests develop. Therefore, altered patterns of recovery in early-successional forests with different disturbance origins will likely shape the structure and function of later-successional stages. Forest management should seek to limit future anthropogenic perturbations, especially salvage logging, to preserve total diversity of plant communities in ash-type forests. This is pertinent with predicted increases in wildfire likely to increase the extent of early-successional fire-prone forests in many already regrowth-dominated ecosystems, which risk falling into positive feedbacks.