2021 ESA Annual Meeting (August 2 - 6)

Synergistic impacts of wildfire and experimental forest fragmentation on tree mortality

On Demand
Anna I. Spiers, n/a, University of Colorado Boulder;
Background/Question/Methods

Understanding how interacting disturbances impact biodiversity is critical in a warming climate. Historically, habitat loss and fragmentation are the largest causes of biodiversity loss, but forest fires are growing larger and more intense due to fire suppression and extreme climate impacts. Despite the anthropogenic escalation of habitat fragmentation and wildfire, we know little about their synergistic impacts on biodiversity. We document Eucalyptus forest community resilience and recovery following a wildfire in an experimentally fragmented forest. The area burned in Australia’s 2019-20 bushfires was the largest in a single season globally. This area included the Wog Wog Habitat Fragmentation Experiment in southeastern Australia where native Eucalyptus forest was fragmented in 1987 when an exotic pine plantation was established. We combine uncrewed aerial system (UAS) imagery taken before and after the fire at Wog Wog, historical tree surveys, and field assessments of burn severity to identify individual tree mortality and burn severity across the experiment within a year following the fire. We assess the role of the following in driving burn severity and mortality: environment (e.g., slope, hydrology), neighbor effects (e.g., tree density), individual traits (e.g. species, size), and fragmentation (e.g., fragments vs. controls, fragment size, edge effects).

Results/Conclusions

Our findings contribute to understanding of the synergistic impacts of habitat fragmentation and fire on tree communities. The fine spatial resolution of the UAS imagery enabled individual-level analysis of tree responses across the experiment. We found variation in burn severity and mortality across species, tree size, and topography. Preliminary results show that experimental control plots burned heterogeneously, producing a range of mortality probabilities for trees in unfragmented forest. In contrast, Eucalyptus fragments burned more homogeneously and severely with higher probability of tree mortality. We hypothesize that the pine forest monoculture in the fragmented landscape led to more efficient and uniform propagation of fire into fragments. This study provided a unique opportunity to assess the short-term impacts of a wildfire on an experimentally fragmented Eucalyptus forest within a year of burning, and to establish a baseline for comparison to long-term ecosystem recovery following interacting disturbances.