Soil warming increases plant species richness but decreases germination from the alpine soil seed bank

Abstract

Global warming is occurring more rapidly above the treeline than at lower elevations and alpine areas are predicted to experience above average warming in the future. Temperature is a primary factor in stimulating seed germination and regulating changes in seed dormancy status. Thus, plant regeneration from seed will be crucial to the persistence, migration and post disturbance recruitment of alpine plants in future climates. Here, we present the first assessment of the impact of soil warming on germination from the persistent alpine soil seed bank. Contrary to expectations, soil warming lead to reduced overall germination from the soil seed bank. However, germination response to soil temperature was species specific such that total species richness actually increased by nine with soil warming. We further explored the system by assessing the prevalence of seed dormancy and germination response to soil disturbance, the frequency of which is predicted to increase under climate change. Seeds of a significant proportion of species demonstrated physiological dormancy mechanisms and germination of several species appeared to be intrinsically linked to soil disturbance. In addition, we found no evidence of subalpine species and little evidence of exotic weed species in the soil, suggesting that the soil seed bank will not facilitate their invasion of the alpine zone. In conclusion, changes in recruitment via the alpine soil seed bank can be expected under climate change, as a result of altered dormancy alleviation and germination cues. Furthermore, the alpine soil seed bank, and the species richness therein, has the potential to help maintain local species diversity, support species range shift and moderate species dominance. Implications for alpine management and areas for further study are also discussed.

Seeds at the forefront: synthesis of the inaugural National Seed Science Forum and future directions in Australian seed science

“…Seed traits and environmental thresholds for regeneration can also further understanding of species' vulnerabilities to climate change. For example, recent studies have found that as soil temperatures increase or fire regimes change there will be measurable changes in the level and extent of seed dormancy within-species, as well as possible deleterious changes in the capacity of seeds to persist in the soil seed bank (Ooi et al 2012;Hoyle et al 2013;Ooi et al 2014). Australia's alpine regions are predicted to experience significant changes in temperature over the next few decades, with the effects on soil seed banks and seed regeneration potentially resulting in profound changes to the composition of vegetation communities (Hoyle et al 2013;Sommerville et al 2013;Hoyle et al 2014).…”

“…For example, recent studies have found that as soil temperatures increase or fire regimes change there will be measurable changes in the level and extent of seed dormancy within-species, as well as possible deleterious changes in the capacity of seeds to persist in the soil seed bank (Ooi et al 2012;Hoyle et al 2013;Ooi et al 2014). Australia's alpine regions are predicted to experience significant changes in temperature over the next few decades, with the effects on soil seed banks and seed regeneration potentially resulting in profound changes to the composition of vegetation communities (Hoyle et al 2013;Sommerville et al 2013;Hoyle et al 2014). In light of these changes, the ability to identify which species are likely most sensitive to warming or drought (Cochrane et al 2014a, b;Cochrane et al 2015a, b;Cochrane 2016;Cochrane 2017) will allow for informed development of conservation strategies that prioritise conservation actions for at-risk species.…”

Inconclusive Predictions and Contradictions: A Lack of Consensus on Seed Germination Response to Climate Change at High Altitude and High Latitude

“…There are a small but increasing number of studies addressing the possible effects of warming on germination ecology of alpine species [25][26][27][28][29][30][31][32]. However, the results of these studies have led to uncertainties in answering the important question: does a warmer alpine climate favor or hamper the germination of seeds?…”

“…We were able to include only five studies in their entirety; all the combination of treatments applied to different species listed in these five studies met our review requirements: 6 rows [27], 6 rows [31], 46 rows [28], 16 rows [26], and 90 rows [25]. In some other studies, only part of the investigation made it into our analysis as treatments were omitted because they could not be satisfactorily compared to the control.…”

The Effects of Climate Warming on Plant-Herbivore Interactions

“…However, air and soil warming strongly affects germination rates (Walck et al 2011). In many cases, warming decreases germination rates (Yurkonis & Meiners 2004, Hoyle et al 2013. Oenothera biennis may therefore be maximizing seed production to offset likely reductions in germination due to climate warming and herbivores.…”