Germination at Extreme Temperatures: Implications for Alpine Shrub Encroachment.

Area of Science:

• Ecology
• Botany
• Climate Change Science

Background:

• Shrub cover is increasing in alpine and tundra regions globally.
• This expansion is linked to rising temperatures and reduced snowpack.
• Climate change may necessitate shrub recruitment from seeds germinating outside optimal temperature ranges.

Purpose of the Study:

• To determine the germination temperature niche for 14 alpine shrub species.
• To compare laboratory germination temperatures with environmental conditions at seed collection sites and across species' distributions.

Main Methods:

• Utilized a temperature gradient plate to assess seed germination across various temperatures.
• Related germination temperature ranges to long-term average temperatures at seed accession sites and geographic distributions.

Main Results:

• Seven species had insufficient germination for analysis.
• The remaining species exhibited broad germination niches (up to 17°C range), but often with low overall germination rates.
• Optimal germination temperatures exceeded those at seed collection sites and were within or above the maximum modeled temperatures across species' ranges.

Conclusions:

• Alpine shrub germination niches are often broader than current site temperatures.
• Some species' germination is limited by seed dormancy.
• Successful shrub encroachment in alpine areas will depend on microsite germination conditions, despite overall warming trends.