Post-fire ecosystems are inherently heterogeneous because fires rarely burn uniformly and often leaves surviving individuals and unburned habitat fragments. Natural regeneration of disturbed landscapes can be highly dependent on these remnant available seed sources from undisturbed patches or from outside the fire boundary. Whether unburned patches can expand across the landscape via seed dispersal is critical to the spatial pattern of ecosystem recovery, with implications for management, including where to target active restoration efforts. Sagebrush-steppe is one ecosystem experiencing larger and more frequent wildfires in recent years and provides an excellent study system for considering heterogeneity of post-fire landscapes and estimating natural regeneration. Natural post-fire regeneration of sagebrush is extremely variable across landscapes. We asked the question: how do unburned remnant sagebrush contribute to the natural regeneration of burned landscapes? To answer this question, we conducted a seed trapping experiment around remnant patches at three sites each over two years, during which we placed vertical sticky traps at varying distances from patches and recorded the height and counts of all seeds caught on the traps. Next, we tested germination of trapped seed and finally, mapped the location of post-fire seedlings and remnants four years after a fire. We then combined these data sources into one dispersal and recruitment model in a hierarchical Bayesian framework that simultaneously estimated the seed dispersal kernel, germination rate, and recruitment of sagebrush seedlings.
Results/Conclusions
Preliminary results suggest that the majority of seed dispersal is limited to short distances, but that a small percentage of seeds do reach farther distances (to at least 13m). Germination rates of trapped seeds were relatively high (~ 60%) and did not vary with dispersal distance. We also found a high degree of variation in recruitment and found that recruitment is dependent on seeds reaching appropriate microsites. The modeling framework provides a method to simulate natural recruitment across burned landscapes to determine which areas are most likely to regenerate on their own and which areas are not. As the amount of money spent on post-fire regeneration seeding increases, it will become more critical to allocate restoration resources to areas where natural regeneration is unlikely.