Ruikun Gou

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Gou

First Name

Ruikun

ORCID

0000-0003-4655-2479

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Publications 1 - 4 of 4

Atmospheric water demand constrains net ecosystem production in subtropical mangrove forests
Gou, Ruikun; Chi, Jinshu; Liu, Jiangong; et al. (2024)
Journal of Hydrology
Subtropical mangroves have great potential to sequester atmospheric carbon dioxide (CO2) and thus significantly contribute to climate change mitigation. Meanwhile, the carbon cycling processes in subtropical mangroves are vulnerable to the changing climatic conditions, such as the warming-induced vapor pressure deficit (VPD) increases. However, the impacts of VPD on net ecosystem production (NEP) in subtropical mangroves remain poorly understood due to a lack of detailed assessment of NEP responses to VPD among different mangrove forests over a long-term observational period. In this study, we deployed eddy-covariance systems to measure net ecosystem CO2 exchange at three subtropical mangrove forests for 16 site-years, comprising two natural and one artificial forests. We employed a state-of-the-art data-driven modeling approach (i.e., Shapley additive explanations (SHAP) framework based on extreme gradient boosting model), which enabled us to explore the interactive effects of meteorological and tidal factors (e.g. salinity) with VPD on the mangrove NEP. We revealed that air temperature, global solar radiation (GR) and wind speed have significant interactions on the response of NEP to VPD stress in subtropical mangroves. For instance, when GR was high, the SHAP interaction values of VPD and GR on NEP decreased with increasing VPD, but when GR was low, the trends were the opposite. However, instead of identifying interactive effects between tidal salinity and VPD on mangrove NEP, we came across potential independent influence of salinity on the same. SHAP analysis was also able to disentangle the impact of VPD from other abiotic drivers. Thus, we evaluated the threshold effect of VPD stress on NEP loss in subtropical mangroves and observed a range of 2.50–2.95 kPa. Above this range, VPD stress leveled off. The subtropical mangrove responses to VPD should be therefore considered in the dynamic global vegetation models to increase the accuracy in carbon cycle simulations in the future.
CO₂ fluxes contrast between aquaculture ponds and mangrove forests and its implications for coastal wetland rehabilitation in Leizhou Peninsula, China
Gou, Ruikun; Feng, Jianxiang; Zhou, Haichao; et al. (2024)
Agriculture, Ecosystems & Environment
Coastal wetlands have great potential to mitigate climate change. However, in recent decades, the construction of aquaculture ponds has degraded coastal habitats, especially mangroves. Meanwhile, the lack of synchronized monitoring of carbon dioxide (CO₂) fluxes in coastal ponds and mangroves hinders the promotion of carbon neutrality target through the implementation of coastal wetland rehabilitation. To address this issue, we deployed two eddy-covariance systems in the ponds and nearby mangroves to measure the net ecosystem CO₂ exchange between atmosphere and ecosystems for two years. The results indicated that both the ponds and mangroves were CO₂ sinks at the annual scale, with mean net ecosystem production (NEP) of 123 ± 39 and 1296 ± 32 g C m⁻² year⁻¹, respectively. During the 2-year period, the ponds acted as CO₂ sources in certain seasons, while the mangroves displayed consistently high seasonal NEP. The construction of ponds by clearing mangroves would reduce NEP along the coasts of the Leizhou Peninsula by about 91% (96% for China), while abandoning all ponds for mangrove rehabilitation could have a significant CO₂ mitigation benefit (i.e., 214.7 Gg year⁻¹). Moreover, we compared how CO₂ fluxes responded to global solar radiation and temperature by analyzing relevant parameters in the two ecosystems. Overall, the ponds showed lower light-saturated net CO₂ exchange and Q₁₀ values compared to the mangroves. Finally, we applied an advanced machine learning local interpretation algorithm to investigate the crucial drivers and their main effects on NEP. This analysis highlighted global solar radiation as the predominant driver for NEP in both ecosystems. High temperature and vapor pressure deficit inhibited mangrove NEP, particularly during summer, whereas pond NEP exhibited greater volatility in response to meteorological conditions such as temperature. Our findings provide insights for further proceeding with mangrove restoration and management to enhance the carbon sequestration capacity of coastal wetlands.
Spatial patterns and driving factors of carbon stocks in mangrove forests on Hainan Island, China
Meng, Yuchen; Gou, Ruikun; Bai, Jiankun; et al. (2022)
Global Ecology and Biogeography
Aim Mangrove forests are important coastal wetlands for the blue carbon budget and play a significant role in mitigating global climate change. However, spatial patterns of carbon stocks in mangrove forests on an island scale have not been quantified owing to methodological limitations and lack of understanding of controlling factors. We took the entire Hainan Island as a case study and aimed to carry out a comprehensive investigation of the spatial patterns and driving factors of carbon stocks in mangrove forests. Location Southern China. Time period 2017–2020. Major taxa studied Mangrove forest. Methods The upscaling method combined with field surveys and Sentinel-2 imagery analysis were used to compare different models for optimization of mangrove ecosystem carbon stock estimations. We also used structural equation modelling (SEM) to evaluate the factors driving the distributional patterns of mangrove carbon stocks on an island scale. Results The current total mangrove carbon stock of the entire Hainan Island was estimated to be 703,181 Mg C (with a mean density of 192 Mg C/ha), with the above- and below-ground carbon stocks averaging at 44.7 and 147.3 Mg C/ha, respectively. The mangrove carbon storage in the north-eastern region of the island was the highest and in the west region the lowest. Sediment nitrogen content and plant species diversity had the most positive driving effects on the distribution of total carbon stock for Hainan Island mangroves. Main conclusions The combination of field surveys and Sentinel-2 imagery analysis can be applied to regional-scale estimations of carbon stocks for mangrove forests. Spatial pattens of mangrove carbon stocks vary among locations on Hainan Island, and soil nutrient (especially nitrogen) availability is the dominant factor regulating carbon stock variations along the land-to-sea gradient. Our findings have significant implications for better understanding the distribution of mangrove carbon stocks and quantification of the global blue carbon budget.
Temporal variations of carbon and water fluxes in a subtropical mangrove forest: Insights from a decade-long eddy covariance measurement
Gou, Ruikun; Buchmann, Nina; Chi, Jinshu; et al. (2023)
Agricultural and Forest Meteorology
Mangroves, highly efficient ecosystems in sequestering CO2, are strongly impacted by climate change. The lack of long-term observation in mangroves hinders the evaluation of seasonal and inter-annual variability in carbon and water fluxes and their responses to various environmental drivers. In this study, we measured net ecosystem CO2 exchange and evapotranspiration between the atmosphere and subtropical mangroves using the eddy covariance technique over a decade (2010–2019) in southern China. This mangrove forest acted as a strong CO2 sink, with annual net ecosystem production (NEP) ranging from 622.5 to 832.8 g C m−2 year−1. The annual evapotranspiration (ET) varied between 934.6 and 1004.9 mm year−1. During the study period, ET consistently remained higher in the wet season (May to October) compared to the dry season, while NEP did not exhibit consistent seasonal variation. Path analysis indicated that during the dry season, NEP was primarily influenced by global solar radiation and vapor pressure deficit. However, in the wet season, NEP was regulated by a combination of global solar radiation, vapor pressure deficit, air temperature, and tidal inundation time. Additionally, the promoting effect of global solar radiation on NEP decreased in the wet season, while the inhibitory influences of higher temperature and vapor pressure deficit on NEP intensified during the period. Unlike NEP, the dominant factors affecting ET (global solar radiation, air temperature, and vapor pressure deficit) and their intensities remained relatively consistent during both seasons. Furthermore, the relative importance of global solar radiation on NEP and ET increased over the decade, while the influence of tidal inundation time diminished. This study not only improves the understanding of the response of subtropical mangroves to climate change but also provides a valuable benchmark dataset to validate the interannual variability of mangrove carbon and water fluxes estimated from the models.

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Ruikun Gou

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