Provenance effects in Banksia attenuata germination and emergence: implications for restoration seed sourcing under climate change

The rapidity of climate change and its effects have contributed to the complexity of selecting an appropriate seed source for restoration projects. The use of a traditional local provenancing seed sourcing strategy has been critiqued as it may fail to facilitate long-term sustainability of a restoration site. Alternative strategies such as climate-adjusted provenancing may enhance lasting survival of a restored community, by purposefully selecting seed sources that match future climate predictions for the site. This study assessed the population-level variation (that is, a provenance effect) in Banksia attenuata seed germination and emergence in response to a variety of environmental stimuli. Specifically, laboratory trials of seed germination highlight that Banksia attenuata shows significant provenance effects in response to temperature, with seed sourced from hotter climates achieving greater germination under hotter incubation temperatures than seed sourced from cooler climates. All sampled populations displayed a significant interactive effect with water potential (MPa), whereby a decrease in MPa resulted in a varied reduction in germination between populations. Four trial locations were established to investigate any provenance effects in Banksia attenuata emergence. No overall significant provenance effect was observed at unmined or postmining restoration sites 16 weeks after seeds had been sown. These findings indicate that provenance does not play a significant role in Banksia attenuata seedling emergence in field trials, suggesting that local seed sourcing for restoration of Banksia attenuata is no more effective than using non-local seed. The results from the field trial provide little evidence to support a climate-adjusted seed sourcing strategy for restoration in the future. The contrasting results between laboratory (germination) and field (emergence) trials points to the need for future research quantifying determinants of species provenance in a practical restoration context