The effectiveness of seed rain in recolonising an ecotonal mesic forest following extreme-severity fire

Context As fire severity and extent increase, recovery of fire-sensitive species in plant communities may rely increasingly on seed rain and dispersal from adjacent unburnt areas. The role dispersal plays in driving recovery trajectories is surprisingly understudied. How traits drive dispersal can contextualise compositional differences and indicate recovery trajectories. Aims This paper investigated seed rain in recently burned mesic forest, and the role of traits in driving post-fire recovery across a gradient of fire severities. Methods We placed seed traps at two locations in the Blue Mountains, located in south-eastern Australia. All seeds that fell into seed traps were collected and identified each month for a year, 3 years following fire of differing severities. We then compared species diversity of seed collections with extant vegetation and measured the minimum dispersal distance each species was likely to have travelled. Variable selection was used to identify which traits affected dispersal distances. Key results Rainforest species were generally lacking from recently burned sites in both extant vegetation and the seed rain. Composition of the seed rain indicated that dispersal occurred primarily from local sources, with minimum distance travelled largely determined by life form, dispersal type and dispersal height. Differences in species richness and composition between unburnt sites and sites burnt at differing severities was observed in both extant vegetation and in the seed rain. Conclusions Increasing fire severity suggests lengthening recovery times, with recolonisation from unburnt areas being minimal and slow. Implications The commonality of local dispersal highlights the importance of surviving individuals for maintaining diversity and replenishing populations.