Germination at Extreme Temperatures: Implications for Alpine Shrub Encroachment

Abstract

Worldwide, shrub cover is increasing across alpine and tundra landscapes in response to warming ambient temperatures and declines in snowpack. With a changing climate, shrub encroachment may rely on recruitment from seed occurring outside of the optimum temperature range. We used a temperature gradient plate in order to determine the germination niche of 14 alpine shrub species. We then related the range in laboratory germination temperatures of each species to long-term average temperature conditions at: (1) the location of the seed accession site and (2) across each species geographic distribution. Seven of the species failed to germinate sufficiently to be included in the analyses. For the other species, the germination niche was broad, spanning a range in temperatures of up to 17 °C, despite very low germination rates in some species. Temperatures associated with the highest germination percentages were all above the range of temperatures present at each specific seed accession site. Optimum germination temperatures were consistently within or higher than the range of maximum temperatures modelled across the species’ geographic distribution. Our results indicate that while some shrub species germinate well at high temperatures, others are apparently constrained by an inherent seed dormancy. Shrub encroachment in alpine areas will likely depend on conditions that affect seed germination at the microsite-scale, despite overall conditions becoming more suitable for shrubs at high elevations.

Shrub encroachment impaired the structure and functioning of alpine meadow communities on the Qinghai–Tibetan Plateau

“…Furthermore, shrubs usually produce a biochemically recalcitrant plant litter and decrease the photooxidation of surface organic matter, two processes that promote litter accumulation (Eldridge et al, 2011; Fenner & Freeman, 2020). The combination of a thicker litter layer and the relatively lower temperatures at shrub understories can significantly impact the reproductive success of many herbaceous species (Venn et al, 2021).…”

Insecticidal efficacy of Chrysanthemum cinerariaefolium Seed Oil Against Cowpea Beetle and Its Impact on the Physicochemical and Technological Characteristics of Cowpea during Storage

“…By the mechanism of pyrthrin, they enter the nervous system of the insect by penetrating its cutile when they come into contact with its body. This causes the nerve cells to stop functioning and the insect nervous system to close, which ultimately causes the insect to die (Venn et al, 2021). C. cinerariaefolium contains pyrethrin, a potent natural insecticide that acts on insects' nerve systems systems to provide a "knockdown effect" (Kikuta et al, 2012).…”

Slope position- mediated soil environmental filtering drives plant community assembly processes in hilly shrublands of Guilin, China

“…Shrubs act as an essential component of global and regional vegetation and have rich characteristic such as wide distributions, high germination rates, and high morphological and physiological plasticity, which is an ideal natural experimental model to facilitate adaptation for diverse environments (Xu et al, 2020;Venn et al, 2021). Generally, shrubs are an important component of forest ecosystems and play a vital role in natural forest dynamics, especially during the first stages of tree development.…”