Vegetation Carbon Source/Sink Dynamics and Extreme Climate Response in the Yangtze River Delta Coastal Zone

Coastal zones, as transition areas for sea/land interaction, have substantial carbon sequestration potential while also being particularly vulnerable to extreme climate. Consequently, it has become essential to evaluate the vegetation carbon sinks in coastal zone areas under extreme climate conditions. In this study, we evaluated the vegetation net ecosystem productivity (NEP) in typical regions within the Yangtze River Delta coastal zone from 2000 to 2020. We studied the regional and chronological properties of NEP and its response to extreme climate. The results revealed the following: (1) Vegetation NEP demonstrated a fluctuating rising trend over the past 21 years, with an interannual change rate of 1.96 gC·m−2·a−1, and the 21-year average was 249.22 gC·m−2·a−1. Spatially, the southern part of the region had a higher NEP than the northern part, and the northern part had a higher NEP than the central part. (2) The overall area showed characteristics of a vegetation carbon sink, with carbon sink areas accounting for 82.41%. Among the ecosystems, forest ecosystems exhibited the strongest carbon sink capacity, followed by cropland ecosystems, while wetland ecosystems, urban ecosystems, and grassland ecosystems had relatively weaker carbon sink capacities. (3) The overall spatial change trend showed an upward trend, consistent with the temporal trend. There is also a high risk of vegetation NEP degradation in the future. (4) The NEP’s response to extreme temperature was more pronounced. The largest explanatory power was observed with SU25 and TMAX during single-factor analysis. The strongest explanatory power in the interaction analysis was found in the following three factor groups: R99p∩TMAX, SU25∩TNx, and TXx∩LST. The results highlight a complex synergistic interplay among these influences on NEP. The findings offer a scientific basis for ecological protection and the attainment of dual-carbon goals in the coastal zone of the Yangtze River Delta.