Soil seed banks provide a storage effect in post-logging regrowth forests southeastern Australia

Despite the importance of soil seed banks in diversity maintenance, our understanding of plant response changes in resource availability is largely limited to above-ground vegetation. We investigated how forest structure and edaphic properties influenced the above-ground vegetation and soil seed banks following logging in montane regrowth forests dominated by Eucalyptus regnans in the Central Highlands of southeastern Australia. We surveyed above-ground vegetation, soil seed banks, forest structure and soil properties across 20 harvest units, aged 16 to 20 years. A total of 80 species were identified in above-ground vegetation with 72 species in the soil seed bank, with only 34% of species co-occurring in both species' pools. Climate, soil, topography, and light availability shaped plant composition but the relative importance of these properties varied among individual species and pools of diversity (combined, above-ground, soil seed bank, life form). Annual heat moisture index (AHMI) was the most important factor that influenced plant community composition across all species pools with individual species positively associated with AHMI. Acacia, but not Eucalyptus stem density further moderated plant response via effects on both light availability and soil nitrogen at the stem exclusion phase of stand development. Structurally mediated controls on above-ground community composition flow through to the soil seed bank via above-ground diversity effects on below-ground composition. For the combined species pool, individual species were most frequently related to Acacia stem density that on average explained 20% of model variation. Soil nutrients accounted for most of the model variation for individual species in above-ground (26%), soil seed bank (20%) and non-woody (32%) pools of diversity, with AHMI accounting for most of the model variation for woody species (18%). The differential response of individual species and community composition gradients in resource availability across different pools of species diversity and life forms clearly demonstrates storage effect in wet temperate forests of southeastern Australia that promotes post-disturbance recruitment and persistence. Our work suggests logging interacts with broad environmental controls to shape species diversity. The key role of Acacia stem density as a biotic filter of plant diversity provides opportunity to shape future plant diversity through management interventions such as thinning in the early stages of stand development. With native forest harvesting of these forests set to end from 2024, our findings provide important information future patterns of plant diversity as logged forests recover over time, opportunities for management interventions in shaping plant composition, and potential impacts of future wildfire.