Divergent Blue Carbon Trajectories in the Yellow River Delta Post‐1976 Diversion: Hydrological Stability and Human Disturbance Contrasts Revealed by Multi‐Source Remote Sensing (1984–2023)

ABSTRACT

Coastal wetlands are critical blue carbon sinks, yet their spatiotemporal dynamics under environmental change remain insufficiently quantified. Taking the Yellow River Delta (YRD) as a natural laboratory, this study synthesizes multi‐source remote sensing data, including optical and radar imagery spanning from 1984 to 2023, to explore the evolution of blue carbon stocks following the 1976 river diversion. Two distinct zones were identified: Zone A, characterized by an abandoned channel and sediment starvation, and Zone B, representing an active estuary with hydrological stability. Results show that: (1) Divergent vegetation trajectories: From 1984 to 2023, distinct vegetation dynamics were observed between the two zones. (2) Divergent carbon trajectories: Between 1984 and 2023, Zone A experienced fluctuations in carbon stocks, ranging from 9.90 × 10 ⁴  t to 407.35 × 10 ⁴  t, primarily due to land reclamation and altered hydrological conditions. In contrast, Zone B maintained a dynamic vegetation equilibrium under stable hydrological inputs, with carbon stocks rising from 33.80 × 10 ⁴  t to 547.01 × 10 ⁴  t. (3) Differential invasion impacts: The invasion of Spartina alterniflora after 2010 significantly increased carbon storage in Zone B by 46.60 × 10 ⁴  t. Conversely, the primary driver in Zone A was the hydrologic alteration following the river diversion, leading to heightened salinization. This condition limited the invasion of Spartina alterniflora . (4) Spatial reorganization: High‐carbon zones transitioned from being concentrated in Phragmites australis ‐dominated riverbanks during 1984–2010 to encompassing Spartina alterniflora ‐invaded areas within Zone B during 2010–2020. In salt marsh wetlands, hydrological conditions act as a critical regulator of blue carbon dynamics, primarily by governing vegetation cover and succession trajectories.