Spatial heterogeneity in Holocene forest compositional turnover across China inferred from pollen assemblages

Holocene pollen records provide important baselines for understanding long-term vegetation responses to climate variability and human disturbance. Here, we examined Holocene arboreal pollen dynamics across China using arboreal pollen (AP) assemblages from 189 records, integrating AP Z-scores, spatial interpolation, and rate-of-change (RoC) analysis to characterize AP-inferred arboreal representation and arboreal pollen assemblage turnover. Our results show a three-stage national trajectory of AP-inferred arboreal representation, with an early-Holocene increase, a middle-Holocene highstand, and a late-Holocene decline. Spatial interpolation at 9, 6, and 3 ka BP showed pronounced spatiotemporal heterogeneity, with the widest extent of high AP values during the middle Holocene and lower AP values across many regions during the late Holocene. In contrast, RoC remained generally low during the early to middle Holocene but increased after ∼4.2 ka BP, with a further rise during the last ∼1 ka. Regional contrasts were also evident: humid monsoonal regions showed relatively high AP-inferred arboreal representation and comparatively low RoC, whereas monsoon-margin, ecotonal, arid, and high-altitude regions showed stronger late-Holocene variability, higher RoC values, or more frequent peak-flagged intervals. These results indicate that AP-inferred arboreal state and compositional turnover rate provide complementary perspectives on Holocene vegetation change. Long-term hydroclimatic variability likely shaped the broad trajectory of arboreal pollen representation across China, while late-Holocene climatic variability, together with a possible contribution from human land use, may have increased compositional turnover in sensitive regions.