Soil-geomorphic heterogeneity governs patchy vegetation dynamics at an arid ecotone

Area of Science:

• Ecology
• Soil Science
• Geomorphology

Background:

• Soil properties significantly impact vegetation distribution and dynamics.
• The influence of soil heterogeneity on vegetation patterning, particularly at ecotones, remains under-documented.
• Understanding these relationships is crucial for predicting landscape responses to environmental changes.

Purpose of the Study:

• To investigate if ecotone location is determined by historical degradation or inherent soil properties.
• To determine if vegetation dynamics (cover and spatial organization) reflect self-organization or stable soil patterns.
• To identify specific soil properties influencing vegetation patch dynamics.

Main Methods:

• Analysis of ecotone location in relation to soil development.
• Assessment of vegetation cover and spatial organization changes using repeat aerial photography over 60 years.
• Statistical analysis correlating vegetation persistence and patch state with soil properties (surface calcium carbonate, subsurface clay content).

Main Results:

• The present-day ecotone corresponds to a transition from weakly to strongly developed soils.
• Vegetation dynamics occurred primarily in small patches (<40 m2), with some areas showing stability over 60 years.
• Vegetation presence and persistence were negatively related to surface calcium carbonate and positively related to subsurface clay content.

Conclusions:

• Soil heterogeneity, specifically variations in calcium carbonate and clay content, significantly constrains vegetation dynamics and patch organization.
• Ecotone location is linked to inherent soil properties, not solely historical degradation.
• Self-organizing vegetation processes are modulated by underlying soil heterogeneity, limiting landscape-scale changes to specific soil-susceptible areas.