Grazing Modulates the Multiscale Spatial Structure of Dryland Vegetation

Area of Science:

• Ecology
• Environmental Science
• Plant Ecology

Background:

• Drylands exhibit a two-phase spatial structure of vegetation and bare soil, influencing ecosystem function.
• Global change drivers like aridity affect dryland vegetation patterns, but herbivore impacts, feeding habits, and mediating plant traits remain unclear.

Purpose of the Study:

• To investigate the effects of herbivores on dryland vegetation spatial structure.
• To differentiate herbivore impacts from climatic gradients and understand trait-mediated responses.

Main Methods:

• Coupled spatial vegetation pattern analysis of ecosystem images with field data on plant size distribution and life forms.
• Analyzed data from 326 plots across 25 countries and six continents.
• Utilized model simulations incorporating positive plant interactions.

Main Results:

• Herbivore effects on vegetation spatial structure were opposite to aridity effects.
• Grazed areas showed vegetation clustered into larger patches, skewing the patch-size distribution.
• Effects varied between browsing and grazing herbivores, with grazing reducing plant size, increasing shrub density, and promoting interspecific facilitation.

Conclusions:

• Herbivores significantly shape dryland ecosystem-level spatial patterns through species-level mechanisms.
• Understanding herbivory's role is crucial for dryland resilience under changing environmental conditions.