Evaluation of the carbon sequestration of Zhalong Wetland under climate change

Wetland ecosystems are crucial to the global carbon cycle. In this study, the Zhalong Wetland was investigated. Based on remote sensing and meteorological observation data from 1975-2018 and the downscaled fifth phase of the coupled model intercomparison project (CMIP5) climate projection dataset from 1961-2100, the parameters of a net primary productivity (NPP) climatic potential productivity model were adjusted, and the simulation ability of the CMIP5 coupled models was evaluated. On this basis, we analysed the spatial and temporal variations of land cover types and landscape transformation processes in the Zhalong Nature Reserve over the past 44 years. We also evaluated the influence of climate change on the NPP of the vegetation, microbial heterotrophic respiration (Rh), and net ecosystem productivity (NEP) of the Zhalong Wetland and predicted the carbon sequestration potential of the Zhalong Wetland from 2019-2029 under the representative concentration pathways (RCP) 4.5 and RCP 8.5 scenarios. Our results indicate the following: (1) Herbaceous bog was the primary land cover type of the Zhalong Nature Reserve, occupying an average area of 1168.02 +/- 224.05 km(2), equivalent to 51.84% of the total reserve area. (2) Since 1975, the Zhalong Nature Reserve has undergone a dry-wet-dry transformation process. Excluding several wet periods during the mid-1980s to early 1990s, the reserve has remained a dry habitat, with particularly severe conditions from 2000 onwards. (3) The 1975-2018 mean NPP, Rh, and NEP values of the Zhalong Wetland were 500.21 +/- 52.76, 337.59 +/- 10.80, and 162.62 +/- 45.56 gC center dot m(-2)center dot a(-1), respectively, and an evaluation of the carbon balance indicated that the reserve served as a carbon sink. (4) From 1975-2018, NPP showed a significant linear increase, Rh showed a highly significant linear increase, while the increase in the carbon absorption rate was smaller than the increase in the carbon release rate. (5) Variations in NPP and NEP were precipitation-driven, with the correlations of NPP and NEP with annual precipitation and summer precipitation being highly significantly positive (P < 0.001); variations in Rh were temperature-driven, with the correlations of Rh with the average annual, summer, and autumn temperatures being highly significantly positive (P < 0.001). The interaction of precipitation and temperature enhances the impact on NPP, Rh and NEP. (6) Under the RCP 4.5 and RCP 8.5 scenarios, the predicted carbon sequestration by the Zhalong Wetland from 2019-2029 was 2.421 (+/- 0.225) x 10(11) gC center dot a(-1) and 2.407 (+/- 0.382) x 10(11) gC center dot a(-1), respectively, which were both lower than the mean carbon sequestration during the last 44 years (2.467 (+/- 0.950) center dot 10(11) gC center dot a(-1)). Future climate change may negatively contribute to the carbon sequestration potential of the Zhalong Wetland. The results of the present study are significant for enhancing the abilities of integrated eco-meteorological monitoring, evaluation, and early warning systems for wetlands.

Automated summary

This study investigates the Zhalong Wetland ecosystem and its response to climate change. The research reveals the dominant land cover type of herbaceous bog in the Zhalong Nature Reserve and the dry-wet-dry transformation process over the years. Results show significant impacts of climate change on vegetation, microbial respiration, and carbon sequestration potential in the wetland.