Partitioning precipitation moisture sources in a cold-temperate forest: Seasonal dominance of advection and transpiration in the Greater Khingan Range, China

This study focuses on the northern Greater Khingan Range, a cold-temperate forest region at the interface between the high-latitude westerlies and the East Asian monsoon and spanning a permafrost transition zone. Event-based precipitation stable isotopes (July 2022–June 2025) were analyzed to partition advective versus locally recycled moisture contributions. The workflow integrated HYSPLIT backward trajectories, a Lagrangian Moisture Uptake diagnostic, and a seasonally structured isotope mixing model with two-end-members in the cold season (October–April) and three in the warm season (May–September). Uncertainty was evaluated using Monte Carlo simulations. Precipitation isotopes showed “summer enrichment–winter depletion” and were strongly correlated with temperature. The Local Meteoric Water Line slopes suggested more kinetic fractionation in the warm season (6.98) but near-equilibrium conditions in the cold season (7.87). Moisture Uptake diagnostics revealed seasonal contrasts in transport pathways: westerly-derived distant sources dominated cold-season moisture uptake (PMU r = 80.2%), whereas monsoon-related near-source regions accounted for 85.9% in the warm season. Consistently, end-member partitioning showed advective dominance in the cold season ( f adv > 74%) and enhanced recycling in the warm season ( f re = 33.0–45.7%), driven mainly by transpiration ( f tr peaking at 39.0%). Overall, these results constrain seasonal moisture-source dynamics in the northern Greater Khingan Range and provide benchmarks for ecohydrological modeling under climate change. • Isotopes show seasonal enrichment (warm) and depletion (cold) controlled by temperature. • Transport shifts from cold-season westerlies to warm-season monsoon inflow. • Moist uptake reveals source shift from continental (80.2%) to monsoon (85.9%). • Cold-season precipitation dominated by advection ( f adv > 74%); local recycling minimal. • Warm-season moisture recycling ( f re = 33–46%) is dominated by transpiration ( f tr up to 39.0%)