Climate change may alter seed and seedling traits and shift germination and mortality patterns in alpine environments

The early life-history stages of alpine plants are strongly influenced by climatic factors. Predicted changes in alpine climate could significantly impact the ability of plants to regenerate from seed and thus on the long-term survival of these species. However, our knowledge on this topic has focused predominantly on the effects of warming on germination. Other early life-history stages or other changing environmental factors have been overlooked. Here, we determine the effects of a future warmer and drier climate and post-fire conditions on (1) seed development, (2) germination and (3) seedling establishment of 13 alpine species.

For 2 years, we conducted a factorial field-based manipulative experiment in the Australian Alps where we created a warmer and drier microclimate using modified open-top chambers and post-fire conditions by controlled burning of selected plots. We (1) collected seeds that had developed under experimental conditions and determined their mass, size, germinability and the characteristics of emerging cotyledons; (2) buried seeds in experimental plots and monitored germination throughout the snow-free season; and (3) grew and planted seedlings and determined their survival over a year.

Overall, we found negative responses to the experimental treatments. Warmer and drier conditions during (1) seed development reduced seed mass, seed size and cotyledon area. (2) Seed germination decreased in response to warmer and drier and post-fire conditions. Importantly, the timing of germination shifted under warmer and drier conditions. (3) Seedling establishment was negatively affected by post-fire conditions and, to a lesser extent, by warmer and drier conditions. The timing of seedling mortality shifted relative to the control conditions.

Predicted future climate will have a negative impact on the ability of plants to regenerate from seed. Furthermore, species-specific responses are likely to contribute to changes in the composition and diversity of alpine communities.