Widespread Shrubification on European Mountain Summits

Area of Science:

• Ecology
• Botany
• Environmental Science

Background:

• Shrub expansion is documented in Arctic tundra but understudied in alpine zones.
• Alpine ecosystems face potential biodiversity and functioning changes due to shrub encroachment.

Purpose of the Study:

• To quantify shrub cover changes in European alpine areas over two decades.
• To assess the drivers and extent of shrub expansion above the elevational treeline.

Main Methods:

• Utilized 576 permanent 1 m² plots across European mountain ranges.
• Monitored shrub cover changes over a 20-year period.
• Analyzed relationships between cover shifts, plant height, leaf nitrogen, and light affinity.

Main Results:

• Total shrub cover increased by an average of 2.6% per m² per decade.
• Evergreen shrubs expanded more (2.0% per m² per decade) than deciduous shrubs (1.7% per m² per decade).
• Expansion magnitude correlated positively with plant height and negatively with leaf nitrogen and light affinity.

Conclusions:

• Shrub expansion is a widespread phenomenon in European alpine zones.
• This expansion has significant implications for alpine plant dynamics, soil, snow, carbon cycling, and food webs.
• Consequences extend to ecosystem services and human livelihoods.