The two faces of Janus: Processes can be both exogenous forcings and endogenous feedbacks with wind as a case study

Area of Science:

• Dryland Ecology
• Ecological State Transitions
• Wind Erosion Dynamics

Background:

• Ecological state transitions are driven by interactions between external forcing factors and internal stabilizing feedbacks.
• In drylands, wind erosion and vegetation interactions create a feedback loop favoring grass-to-shrub transitions.
• The role of extreme wind events as a direct forcing factor, distinct from stabilizing feedbacks, is underexplored.

Purpose of the Study:

• To investigate the dual role of wind processes in dryland state change, acting as both a forcing factor and a feedback component.
• To examine the ecological responses of a grass-shrub community to extreme wind events that caused severe deflation.

Main Methods:

• Field study measuring grass cover, root exposure, shrub height, grass patch size, and grass greenness.
• Data collected along 50-m transects across varying grass cover conditions.
• Analysis focused on responses following two extreme wind events in 2019.

Main Results:

• Extreme wind events directly reduced grass cover and exposed plant roots, particularly in areas with initially low grass cover.
• Root exposure was directional, aligning with the erosive wind patterns during the storms.
• Sites with increased root exposure showed reduced grass greenness, indicating stress and potential state change.

Conclusions:

• Extreme wind events function as significant endogenous forcing factors in dryland ecosystems, capable of initiating state shifts.
• A distinction exists between the forcing role of rare, extreme wind events and the stabilizing feedback role of common wind events.
• This framework helps contextualize state change dynamics across various ecological systems.