[Enhancement effects of ecological restoration on vegetation carbon storage in Sihong Hongze Lake wetland, Jiangsu Province, and the temporal variations.]

Abstract

Vegetation carbon storage is an important indicator for evaluating carbon sequestration benefits of ecologi-cal restoration. While most available studies have relied on static comparisons before and after restoration, direct quantitative evidence remains limited regarding the dynamics in vegetation carbon storage and its temporal response during restoration. Taking the Jiangsu Sihong Hongze Lake National Wetland Nature Reserve as the study area, we constructed a 30 m reflectance series for 2020-2025 using multi-source remote sensing data. Combined with fine classification of eight dominant vegetation communities and type-specific biomass inversion models, we systematically estimated the spatiotemporal patterns of vegetation carbon storage in the reserve and quantitatively evaluated the carbon enhancement effects of 14 ecological restoration projects initiated successively during 2019-2023. The results showed that the mean of the annual baseline vegetation carbon storage during 2020-2025 was 0.18 × 10⁶t C, and the value in 2025 was 0.15 × 10⁶t C. Spatially, vegetation carbon storage exhibited a pattern of being higher in the lakeshore zone and lower in the open lake area. With the project initiation year as the baseline and 2025 as the unified comparison time point, we found that the 14 restoration projects showed a net increase of 1429.25 t C in vegetation carbon storage relative to their baseline years, with an average carbon gain of 2.75 t C·hm^-2. In the key restoration area where the Yangmaozui degraded wetland ecological restoration project Phase II and species conservation-related projects were located, four projects covering approximately 233.33 hm² generated a cumulative carbon increase of 713.12 t C, with an average gain of 3.06 t C·hm^-2. Based on a comparison by restoration duration up to 2025, the projects were divided into four groups of 2, 3, 4, and 5 years. The 2-year group still showed a short-term net decrease in vegetation carbon storage, with a mean change of -1.59 t C·hm^-2. In contrast, the 3-, 4-, and 5-year groups all showed carbon enhancement, with mean net increases of 7.77, 6.01, and 1.79 t C·hm^-2, respectively. These results indicated that the enhancement of vegetation carbon storage by ecological restoration in shallow lake wetlands would not become stable immediately after implementation, but gradually emerge through vegetation recovery and community reconstruction. This study could provide quantitative evidence for understanding the carbon enhancement process of ecological restoration in lake wetlands and offer a scientific basis for restoration performance evaluation and carbon-oriented management.