Data from: Post-fire vegetation shifts: Role of invasives and seedbanks in an Australian grassy woodland ecosystem

Changing fire patterns alongside the growing role of invasive species in
forested landscapes may be interacting to shift post-fire vegetation
communities. Identifying some of the mechanisms of change may help target
ecosystem management. Here, we aim to understand some of the relationships
between fire and introduced species in a grassy woodland environment in
south-eastern Australia, and the role soil seedbanks may be playing in
facilitating any changes. We sampled the soil seedbank and extant
vegetation shortly before a wildfire, with vegetation surveys repeated
thereafter. We used three combinations of data, including a
Before-After-Control-Impact (BACI) survey design and planned contrasts, to
assess changes in the extant vegetation pre- and post-fire, the role of
the soil seedbank in those changes, and how past fire history may have
impacted the vegetation community. Analyses were conducted at both the
species and plant functional group (PFG) level. The wildfire modified the
vegetation community through significant changes to three PFGs: trees and
shrubs, resprouting herbs with persistent seedbanks, and introduced annual
seeders with wind dispersed seed. Sites that were burnt typically had
higher cover of introduced species, and lower cover of native trees and
shrubs. The soil seedbank contributed some new species into the extant
vegetation, predominantly introduced species, with the soil seedbank
becoming more similar to the extant vegetation after fire. Increasing fire
severity typically favoured PFGs with a high proportion of introduced
species, with many native PFGs showing negative or negligible
relationships with fire severity. We did not detect a consistent influence
of time since fire or fire frequency for the majority of PFGs. Synthesis:
Fire events increase the cover of introduced annuals in grassy woodland
environments which may be increasing the flammability of the ecosystem,
suggesting the potential for a grass or forb fire cycle. Given grass-fire
cycles typically reduce the cover of trees and shrubs, a management option
is to support tree regeneration either through active restoration, or by
reducing the occurrence of fire in these ecosystems until trees are both
reproductively mature, and large enough to survive fire. However, the
decision making around ecosystem management should be led by the
Traditional Owners of the land, the Gunditjmara.