Ecosystem functional response across precipitation extremes in a sagebrush steppe

Area of Science:

• Ecology
• Environmental Science
• Plant Biology

Background:

• Precipitation variability is increasing in the western US, impacting water-limited ecosystems.
• Extreme precipitation events significantly influence ecosystem functioning and species composition.
• Long-term ecosystem responses to precipitation shifts may involve species adaptation or physiological limits.

Purpose of the Study:

• To investigate ecosystem functional response to sustained drought and irrigation in a sagebrush steppe.
• To determine if plant community composition changes under altered precipitation regimes.
• To assess the relationship between soil moisture and aboveground net primary productivity (ANPP) under different precipitation scenarios.

Main Methods:

• A five-year precipitation manipulation experiment using drought and irrigation treatments (±50%) in Idaho sagebrush steppe.
• Monitoring of aboveground net primary productivity (ANPP), species abundance, and soil moisture.
• Statistical analysis using generalized linear mixed effects models and nonmetric multidimensional scaling.

Main Results:

• Ecosystem functional response (ANPP-soil moisture relationship) showed increased sensitivity under drought but was weak and uncertain across all treatments.
• Plant community composition remained stable and did not differ significantly among drought, irrigation, and control treatments.
• High spatial variation in ANPP contributed to the uncertainty in the soil moisture effect.

Conclusions:

• Sagebrush steppe ANPP response to soil moisture is weak and community composition is resilient to precipitation variability.
• Ecosystem functional stability is not driven by compensatory community shifts but by the insensitivity of dominant species to soil moisture.
• Dominant species' life history strategies likely confer resilience against precipitation extremes.