Comparative seed germination traits in alpine and subalpine grasslands: higher elevations are associated with warmer germination temperatures

Abstract

Seed germination traits in alpine grasslands are poorly understood, despite the sensitivity of these communities to climate change. We hypothesise that germination traits predict species occurrence along the alpine-subalpine elevation gradient. Phylogenetic comparative analyses were performed using fresh seeds of 22 species from alpine and subalpine grasslands (1600-2400 m) of the Cantabrian Mountains, Spain (43° N, 5° W). Laboratory experiments were conducted to characterise germinability, optimum germination temperature and effect of cold and warm stratification on dormancy breaking. Variability in these traits was reduced by phylogenetic principal component analysis (phyl.PCA). Phylogenetic generalised least squares regression (PGLS) was used to fit a model in which species average elevation was predicted from their position on the PCA axes. Most subalpine species germinated in snow-like conditions, whereas most alpine species needed accumulation of warm temperatures. Phylogenetic signal was low. PCA1 ordered species according to overall germinability, whilst PCA2 ordered them according to preference for warm or cold germination. PCA2 significantly predicted species occurrence in the alpine-subalpine gradient, as higher elevation species tended to have warmer germination preferences. Our results show that germination traits in high-mountain grasslands are closely linked to the alpine-subalpine gradient. Alpine species, especially those from stripped and wind-edge communities, prefer warmer germination niches, suggesting that summer emergence prevents frost damage during seedling establishment. In contrast, alpine snowfield and subalpine grassland plants have cold germination niches, indicating that winter emergence may occur under snow to avoid drought stress.

Seed ecology of the geophyte Conopodium majus (Apiaceae), indicator species of ancient woodland understories and oligotrophic meadows

“…Taken together, the indifference to light and alternating temperatures indicate a preference for germination under a protective layer of leaf litter or snow, an environmental preference also found in sub‐Mediterranean mountain geophytes (Fernández‐Pascual et al . ).…”

Phylogeny and source climate impact seed dormancy and germination of restoration-relevant forb species

“…This germination trait is likely very important for seedling survival, as it is regulated by dormancy and could either promote emergence in suitable conditions or lead to emergence in unsuitable conditions if the timing is not right. Yet this trait is rarely measured, and in the cases where it is, it is rarely analyzed as a unique response, but rather subsumed in the final germination analyses (e.g.,[ 64 ]). The potential for germination in stratification merits more explicit consideration in species and populations in which it may occur.…”

Breaking of dormancy in the narrow endemic Jasione supina Sieber subsp. supina (Campanulaceae) with small seeds that do not need light to germinate

“…montana, and J. orbiculata are light-germinating and non-dormant (Pegtel 1988, Peco et al 2006, Koutsovoulou et al 2014. It has been found that Jasione cavanilesii has a low germination percentage at light and is considered to be dormant (Fernández-Pascual et al 2017).…”