PS 7-67 - Edges and connectivity influence pyrodiversity in a landscape experiment

Background/Question/Methods

Human land use can lead to habitat fragmentation and altered fire regimes that can impact biodiversity. For example, landscape structure (e.g., connectivity or edges) can drive variations in burn severity (pyrodiversity), which in turn can affect plant diversity. In this study, we examine how landscape structure affects fire severity and plant diversity in a large-scale, replicated fragmented landscape experiment on the Savannah River Site, SC. The experiment is composed of 7 blocks, each with 1-ha clearings cut into pine plantation matrix each surrounded by four 1.4-ha clearings, one of which is connected to the center patch by a corridor. The site is managed with prescribed burns. We established arrays of 1m x 1m plots in areas of the site selected to test edge and connectivity effects. In these plots we collected data on plant species occurrence and abundance in September 2021 and June 2022, before and after prescribed burns in the winter of 2021/2022. We also collected data on pre-burn fuel loads and burn temperatures in these plots. We ask 1) How do edges and connectivity affect burn severity? 2) How does burn severity affect plot-level plant diversity? and 3) Does patch-level pyrodiversity positively relate to patch-level plant diversity?

Results/Conclusions

Our preliminary results showed no evidence of connectivity affecting patch-scale burn severity. However, we have found evidence of connectivity locally affecting fire behavior in the area of the corridor. Compared to patch centers, the interior of corridors burned with a significantly higher temperature (t stat= 7.1, p=0.001, df=4), while the interior of geometrically similar (but not connected) “wings” did not (t stat=0.35, p=0.4, df=4). Wing interiors also had patchy burns, with a higher proportion of plots not burning compared to patch centers (t stat= 2.8, p=0.02, df=4). We also found that plots near the edges burned marginally more uniformly than patch centers (t stat=1.8, p=0.054, df=9). These results suggest that edges and connectivity can significantly impact fire behavior within fragments. This variation in burn severity likely impacts plant abundances, which will be determined imminently.