Frost as a limiting factor for recruitment and establishment of early development stages in an alpine glacier foreland?

Abstract

Questions How frost resistant are the early development stages (seeds, seedlings, plantlets and juveniles) of alpine plant species? Do summer frosts impair establishment of plant species typical of different successional stages on a central alpine glacier foreland? Location Rotmoos glacier foreland, Austrian Central Alps (Obergurgl, Tyrol, Austria). Methods Seeds of 12 species typical of different successional stages were collected in the glacier foreland and either sown directly in the field or in a growth chamber (25/10 °C, 16/8 h) and grown to the investigated development stages. Frost resistance of the early development and adult stages was determined by exposing them to a set of freezing temperatures and assessing viability with the tetrazolium test (LT 50, i.e. 50% of samples being lethally frost damaged). Results Dry seeds had the highest frost resistance (LT 50: −19 °C), followed by wet seeds after imbibition (LT 50: −8 °C). With the onset of germination, frost resistance decreased rapidly. While germinated seeds tolerated a mean of −3.2 °C, seedlings and juveniles were less frost resistant (LT 50: −2.5 °C). Along the primary succession, seedlings of pioneer species were significantly less frost resistant than early‐ and late‐successional species. However, field grown seedlings, mainly of pioneer species, showed higher frost resistance (mean: −5 °C) than the growth chamber seedlings (mean: −3 °C), indicating that frost hardening (transition from a lower to a higher level of frost resistance) is already possible during these early stages of development. Conclusions The low frost resistance during and after germination may not suffice to survive summer frosts and may at least in certain years explain the high seedling mortality rates recognized in the glacier foreland.

Habitat‐related seed germination traits in alpine habitats

“…The low germination of the species belonging to “Cluster A” may indicate that cold stratification is not always effective in promoting germination for alpine species or that appropriate cues for germination were not meet (Donohue, Rubio de Casas, Burghardt, Kovach, & Willis, ). The low germination of alpine species under laboratory conditions has been suggested as a mechanism to ensure the formation of a persistent soil seed bank (Mondoni et al., ; Shimono & Kudo, ), as an ecological strategy to the low chance of establishment in these environments (Erschbamer, Niederfriniger Schlag, & Winkler, ; Schwienbacher, Marcante, & Erschbamer, ), due to summer drought/heat and early autumn/spring frost episodes (Graae et al., ; Marcante, Sierra‐Almeida, Spindelböck, Erschbamer, & Neuner, ; Marcante et al., ).…”

Relationship between frost hardiness of adults and seedlings of different tree species

“…While seeds of temperate tree species are generally frost-tolerant down to -196 °C (Sakai & Larcher 1987), they lose frost hardiness with the onset of germination (Marcante et al 2012). As most temperate and boreal tree species germinate at the beginning of the growing season in spring, they are often exposed to late frost events which frequently occur in the temperate and boreal zone (Bigras et al 2004), and therefore, frost events can severely affect seedling growth and survival (Bigras et al 2004, Kreyling et al 2012.…”

“…As most temperate and boreal tree species germinate at the beginning of the growing season in spring, they are often exposed to late frost events which frequently occur in the temperate and boreal zone (Bigras et al 2004), and therefore, frost events can severely affect seedling growth and survival (Bigras et al 2004, Kreyling et al 2012. For plant species in an alpine glacier foreland, Marcante et al (2012) showed that freezing temperatures in the growing season are potentially severe enough to kill plants at early stages of their development. Similarly, Funkenberg et al (2012) demonstrated the importance of late frosts for establishment of Fallopia japonica (Houtt.)…”

Klima, Wetter, Gletscher im Wandel

“…Daneben ist in den spärlich besiedelten Gletschervorfeldflächen an sommerlichen Schön-wettertagen aber auch eine beträchtliche Erwärmung der Pflanzenorgane, der Bodenoberfläche und des Bodens zu erwarten (Neuner & Buchner 2012), sodass sogar Hitzeschäden auftreten können (Buchner & Neuner 2003 (Marcante et al 2012. Marcante et al (2012) (Marcante et al 2012). Außerdem tolerieren die vegetativen Organe der alpinen Pflanzen um 2-5 °C niedrigere Fröste im Vergleich zu den reproduktiven Teilen …”