Effects of burn severity on functional trait diversity of arthropod communities in pine-oak forests

Background/Question/Methods

Prescribed fire and wildfire are among the largest disturbances to impact forest soils each year, and the impact of such events on the structure and function of soil arthropod communities remains poorly understood, although the role of these organisms in shaping soil productivity is widely recognized. Differences in the functional groups that compose these communities can lead to contrasting responses to environmental change and stress. For soil- and litter-dwelling arthropods, fire events have been shown to cause local extinctions and subsequent rapid colonization by regional community members with high dispersal ability, yet little is known about how fire severity influences this effect. We present the preliminary results of an ongoing study, exploring the relationship between fire severity and the taxonomic and functional diversity of soil- and litter-dwelling arthropods, as a step toward better understanding fire as a driver of change in soil communities. Our work focuses on the New Jersey Pinelands, a high-disturbance landscape with frequent prescribed fire and wildfire. Arthropods were sampled from pitfall traps in July and August 2020 from forest plots, which were either burned or unburned. Using tree char height as a proxy for Composite Burn Index, burned plots were categorized by fire severity: low, moderate, or high. Specimens were sorted by taxonomy and trophic guild, then weighed to determine body size and estimate biomass distribution at community level.

Results/Conclusions

Preliminary results indicate that arthropod richness does not vary with fire type, although arthropod abundance peaks in areas that experienced low and moderate fire severity, and at annual frequency/low intensity, when compared to high fire severity areas. Furthermore, across the general arthropod community, mean body size is larger in low severity and unburned plots. Future analysis will help determine if disturbance intensity affects arthropod trophic guild structure, and the overall structure of soil-dwelling arthropod community assemblages. Moderate levels of disturbance intensity appear to promote the greatest overall arthropod diversity, suggesting that char height may be an effective predictor of post-fire shifts in the arthropod community.