Shrub-facilitated invasion accelerates desertification.

Area of Science:

• Ecology
• Environmental Science
• Botany

Background:

• Desertification is theoretically linked to increased primary productivity sensitivity to precipitation variability.
• Empirical evidence linking biological invasions to desertification symptoms is limited.
• Exotic grasses are a growing concern in arid ecosystems.

Purpose of the Study:

• To investigate if exotic grass invasion exacerbates desertification symptoms.
• To assess the role of native shrubs in facilitating exotic grass invasion.
• To quantify the impact of invasion on biomass, biodiversity, and precipitation sensitivity.

Main Methods:

• Field study across precipitation gradients (41-248 mm/year) in Mojave and San Joaquin Deserts over 5 years.
• Measured herbaceous plant biomass and biodiversity in areas with high vs. low exotic grass invasion.
• Compared plant communities under native shrubs vs. interstitial spaces.

Main Results:

• Exotic grass invasion doubled precipitation-to-biomass conversion rates.
• Native shrubs facilitated exotic grasses, increasing ecosystem sensitivity to precipitation.
• Increased biomass production due to invasion correlated with significant native biodiversity loss.

Conclusions:

• Exotic grasses, facilitated by native shrubs, accelerate desertification by promoting a non-native flora sensitive to precipitation variability.
• Invasive grasses degrade biodiversity and ecosystem function in arid environments.
• Controlling exotic grasses and managing facilitated invasions are vital for desertification mitigation.