Alpine plant communities differ in their seed germination requirements along a snowmelt gradient in the Caucasus

Abstract

Mesoscale heterogeneity of alpine landscapes generates snowmelt gradients resulting in a distinct vegetation zonation from almost snow-free fellfields to long-lasting snowbeds. Although the vegetative trait variation along such gradients has been intensively studied, little is known about whether and how seed germination is adapted to the variable snowpack duration. Here, we compare the seed germination niches of 18 characteristic plant species occurring in four distinct plant communities (alpine lichen heath—Festuca varia grassland—Geranium-Hedysarum meadow—snowbed) along an alpine snowmelt gradient in the North Caucasus (Russia). In a fully factorial experiment, we tested seed germination responses to temperature (10/2, 14/6, 18/10, 22/14, 26/18 and 30/22 °C) and water potential (0, − 0.2, − 0.4, − 0.6 and − 0.8 MPa) gradients, reflecting the full spectrum of seedling establishment conditions in the study system. Community-specific germination niches were identified by generalised mixed model with Bayesian estimation. Our study revealed that the species from the four focal communities significantly differed in their temperature requirements for germination, whereas soil moisture was found to be a limiting factor for seedling establishment along the entire gradient. The snowbed germination was constrained to comparatively high temperatures above 10 °C, whereas seed germination in alpine lichen heaths occurred under a wide range of experimental conditions. The seed germination patterns of species from Festuca varia grasslands and Geranium-Hedysarum meadows reflected their intermediate position along the snowmelt gradient. We conclude that seed germination niche is affected by the environmental filtering along the snowmelt gradient thus departing from the general alpine germination syndrome.

Spatiotemporal patterns of microclimatic buffering in relict alpine communities

“…These predictions highlight the need for long‐term monitoring of microclimate and snow patterns, ideally complemented with the assistance of time series of satellite images, together with physiological, genetic, and demographic approaches. It will be also necessary to identify critical plant life stages responding to microclimatic conditions, since only a few studies have tackled this question in adult plant survival, seed dispersal and persistence (Auffret et al., 2023), germination (Shimono & Kudo, 2005) or seedling survival (Rosbakh et al., 2022; Gya et al., 2023). Such studies will be especially informative in alpine relict communities reduced to small alpine areas, which are more likely to experience local extinctions (Körner & Hiltbrunner, 2021).…”

Seed science in Australasia: regionally important, globally relevant

“…Research continues to investigate how germination or reproduction responses are related to multiple environmental factors such as temperature stress (Notarnicola et al 2021), moisture stress (Emery et al 2021;Schultz et al 2021) and seasonal change (Rosbakh et al 2021). These new insights show how the regeneration niche may contribute to species distribution under climate change.…”

“…Coupled with innovative technology like temperature gradient plates (Collette et al 2021), research can test multiple levels of factors and enable high resolution investigations of environmental drivers of germination. Such data are also requiring developments in statistical analysis methods as discussed in the workshop 'Analysing Seed Data with R' (Rosbakh et al 2021).…”