Dispersal and fire limit Arctic shrub expansion

Area of Science:

• Earth System Science
• Ecology
• Remote Sensing

Background:

• Arctic shrub expansion impacts high-latitude carbon budgets, albedo, and warming rates.
• Predicting shrub expansion is challenging due to poorly understood underlying controls.
• Current models often rely on environmental suitability, neglecting crucial demographic processes.

Purpose of the Study:

• To investigate the primary drivers of observed Arctic shrub expansion.
• To compare predictions based on environmental suitability versus dynamic processes.
• To improve projections of future shrub expansion and associated climate feedbacks.

Main Methods:

• Utilized high-resolution satellite imagery across Alaska and western Canada (1984-2014).
• Analyzed shrub expansion patterns in relation to environmental suitability, seed dispersal, and fire history.
• Integrated dynamic processes with projected fire extent and climate for future projections.

Main Results:

• Observed shrub expansion was not controlled by environmental suitability alone.
• Seed dispersal and fire were identified as key explanatory factors for shrub expansion.
• Models incorporating dynamic processes project 25% tundra shrub expansion by 2100, contrasting with 39% from suitability alone.

Conclusions:

• Environmental suitability alone is insufficient for accurately predicting Arctic shrub expansion.
• Incorporating seed dispersal and fire dynamics is crucial for realistic land modeling.
• Current approaches may overestimate shrub expansion and its impact on the Arctic carbon sink.