Spatial variation in non-structural carbohydrates reserves of pine species along climatic gradients: A global synthesis

Non-structural carbohydrates (NSCs) are crucial for tree growth and survival under climatic stress, yet their spatial dynamics across broad climate gradients remain unclear. Pines (Pinus spp.), one of the most widely distributed tree genera worldwide, provide an ideal system for investigating large-scale spatial patterns of NSC within a single genus along extensive climatic gradients. Here, we compiled a global NSC database for pines across 74 sites, and assessed the spatial variation in total NSC, starch (St), and soluble sugars (SS) concentrations in stem sapwood, the primary reserve tissue, along site-specific mean annual temperature (MAT) and precipitation (MAP). Our results show that MAP exerted a stronger influence (R² ​= ​20%–47%) on the spatial variation in total NSC and its components than did MAT (R² ​= ​6%–16%). Total NSC concentrations declined nonlinearly with increasing MAP, with the rate of decline slowing beyond approximately 800 ​mm. While MAT had weaker effects on total NSC concentrations, both MAT and MAP jointly regulated NSC partitioning: Higher MAT and MAP were associated with reduced St concentrations but elevated SS concentrations and SS:St ratios. These findings suggest that pine species in cold and arid environments prioritize storing NSC as St, whereas in relatively warm and humid environments, NSC are preferentially mobilized into SS to support immediate metabolic and growth demands.