Divergent Spatial and Temporal Sensitivities of Forest Biomass to Climate Challenge Space‐For‐Time Assumptions and Models

ABSTRACT

Understanding and projecting forest carbon responses to climate change remains challenging. The widely used space‐for‐time substitution (SFTS) approach assumes that ecological responses along spatial climate gradients can substitute for temporal relationships, yet agreement among spatial, temporal, and mechanistic approaches remains largely unknown. Using global satellite‐derived aboveground biomass (AGB) data, we quantified forest AGB sensitivities to spatial versus temporal climate variability, projected climate‐driven AGB changes under future emission scenarios, and compared results with Earth system models (ESMs). Spatial climate gradients explain substantially more AGB variation than temporal anomalies, with strong divergence across regions and forest ages. ESMs better reproduce spatial sensitivities than temporal ones. Temporal extrapolation generally projects future AGB gains, whereas spatial extrapolation often indicates AGB declines. These contrasts demonstrate that spatial, temporal, and model‐based approaches capture distinct facets of forest–climate coupling, and integrating them can better constrain uncertainty in carbon–climate feedbacks and improve future ecosystem projections.