Warming, rather than drought, remains the primary factor limiting carbon sequestration

Area of Science:

• Ecology
• Climate Science
• Biogeochemistry

Background:

• Steppe ecosystems in arid/semiarid regions are vital for global carbon balance but sensitive to climate change.
• Mechanisms controlling seasonal carbon flux responses to climate shifts remain unclear.

Purpose of the Study:

• Quantify carbon fluxes in Inner Mongolian steppes (2006-2021).
• Investigate climatic factor constraints on carbon fluxes.
• Explore responses to coupled temperature and moisture changes.
• Assess steppe ecosystem adaptation to temperature and drought.

Main Methods:

• Utilized eddy covariance tower data for carbon flux measurements.
• Analyzed relationships between climatic factors (temperature, Vapor Pressure Deficit, Soil Water Content) and carbon fluxes (Net Ecosystem Productivity, Gross Primary Productivity, Ecosystem Respiration).
• Evaluated ecosystem adaptation strategies to climatic variations.

Main Results:

• The steppe ecosystem functions as a carbon sink (73.55 g C m⁻² yr⁻¹), with an N-shaped annual accumulation pattern.
• Temperature and Vapor Pressure Deficit (VPD) exhibit parabolic constraints on Net Ecosystem Productivity (NEP) and Gross Primary Productivity (GPP), with optimal ranges.
• Soil Water Content (SWC) mitigates temperature's negative impact on carbon sequestration.
• Gross Primary Productivity (GPP) drives ecosystem adaptation to temperature and drought, not Ecosystem Respiration (RECO).

Conclusions:

• Inner Mongolian steppes demonstrate adaptive capacity to warming and drought.
• Warming is a more significant limiter of carbon sequestration than drought.
• The ecosystem's adaptation is primarily driven by GPP.
• Despite adaptation, the steppe remains vulnerable at the warming boundary, necessitating continued monitoring and research.