Snow, fire and drought: How alpine and treeline soil seed banks are affected by simulated climate change

Abstract

Background and aims: Seed persistence in soil depends on environmental factors that affect seed dormancy and germination, such as temperature and water availability. In high-elevation ecosystems, rapid changes in these environmental factors due to climate change can impact future plant recruitment. To date, our knowledge on how soil seed banks from high-altitude environments will respond to climate change and extreme climate-related events is limited. Here, using the seedling emergence method, we investigated the effects of reduced snow cover, fire and drought on the density and diversity of germinants from soil seed banks of two high-altitude plant communities: a tall alpine herbfield and a treeline ecotone.

Methods: In Autumn 2020, we collected soil samples and characterized the standing vegetation of both communities at Kosciuszko National Park, Australia. Then, we employed a factorial experiment and subjected the soil samples to a series of manipulative treatments using greenhouse studies.

Key results: The treeline had a larger and more diverse soil seed bank than the herbfield. A reduction in snow had a negative effect on the number of germinants in the herbfield and increased the dissimilarity with the standing vegetation, while the treeline responses were mainly neutral. Fire did not significantly affect the number of germinants but decreased the evenness values in both communities. The drought treatment reduced the number and richness of germinants and increased the dissimilarity with the standing vegetation in both communities. Plant functional forms explained some of the detected effects but seed functional traits did not.

Conclusions: Our study suggests that simulated climate change will affect plant recruitment from soil seed banks in a variety of ways. Changes in snow cover, incidences of fire and drought may be key drivers of germination from the soil seed bank and therefore the future composition of alpine plant communities.

Keywords: alpine herbfield; alpine treeline; dormancy; drought; fire; freeze-thaw cycle; germination; snow reduction; soil seed bank.