2022/09/12 by Benefiel, Sophie, Garzelloni, Roman, Kesler, Joseph
#Big Sur #fire #redwood (Sequoia sempervirens) #spider #structural complexity
paper · doi:10.21973/n3gw91
Spiders are important to many ecosystems as both predators and prey, and their distribution can reflect the health of the ecosystem as a whole. A pressing disturbance impacting spider distribution is fire. Directly following fire, spider density decreases. However, there is less information about their recovery in the years following fire. Spider distribution relies on the structural complexity of vegetation for web-building as well as prey abundance, both of which are affected by fire. The redwood forests of California’s Big Sur region presented a useful study system, as they host a variety of spider species, and were burned by the 125,000-acre Dolan Fire in August 2020. To examine spider distribution two years following the Dolan Fire, we measured these variables in the form of furrow depth and prey density respectively, on the bark of 60 coast redwood trees. Additionally, we recorded whether each web was structured as a sheet or tube, if the web was occupied by a spider, and the intensity of the burn at each tree. We found that overall, burn intensity had no direct effect on spider web density or prey density. However, burn intensity did have a negative effect on furrow depth, whereas furrow depth had a positive effect on sheet web density, but no effect on tube web density. Our findings suggest that two years after fire, the burn intensity on redwood trees has little to no effect on the spiders that occupy the bark of said trees. This speaks not only to the resilience of these spiders as organisms capable of quickly rebounding after fire, but also to the resilience of the ecosystem as a whole.