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Park green spaces (PGSs) are an important component of urban natural carbon sinks, while their spatial morphological patterns can affect the carbon sequestration capacity themselves. This study selected six typical urban parks in the central district of Shanghai and analyzed the correlation between spatial morphological indices and CO2 concentration distribution of the PGSs based on ENVI-met and BRT models. It further explored the interaction mechanisms in the carbon cycling process of urban PGSs under the influence of different spatial morphology. The results shows that urban PGSs play the role of carbon sink in diurnal period, and the difference of CO2 concentration distribution in green space is the largest at 11 a.m. The green biomass (Gb) and arboreal area ratio (Ar) are the most important indices affecting the distribution of carbon concentration. The two indices describing spatial patterns, namely, Cohesion (Co) and canopy density (CanopyD) also significantly impact CO2 concentration. These indices have a positive impact on carbon sinks. The parkway area ratio (Pr) is a disturbing index that also has an obvious negative impact on the distribution of CO2 concentration. The moderate herbs area ratio (Hr) and open land area ratio (Or) are conducive to regulating the microclimate environment and enhancing carbon sink capacity. There is an interactive relationship between spatial indices and microclimate environment indices, as well as physical and physiological indices in the carbon sink process of green areas. The study suggested that in green space management aiming at carbon reduction, combined with the influence threshold of Gb on carbon reduction and paying attention to the importance of green amount on carbon sequestration, the vegetation density and allocation ratio should be rationally distributed to form a park green space landscape with efficient carbon fixation. [ABSTRACT FROM AUTHOR]

• Envi-met was used to simulate carbon concentration distribution in green space. • The waterbody enhanced the carbon sink of the waterfront green space. • The waterfront distance factor is the key spatial factors affects the carbon sink. • The mechanism relies on soil-vegetation-water-atmosphere coupling carbon process. Urban ecological spatial patterns affect the carbon sequestration capacity of green spaces. High-resolution carbon concentration data simulated by Envi-met4.4.5 were obtained in Nanyuan Riverside Green space in Huangpu District, Shanghai. And the correlation among green space morphology factors, microclimatic and bioclimatic factors were explored by Random Forest model. The results showed that the importance of the waterfront distance factor to the carbon sink impact reaches 28.88%, and gradually decreased with the change of distance from water from south to north. The importance of the arboreal area ratio and green biomass reached 15.79% and 12.65% respectively, which was much more important than non-green vegetation space proportion indices. The importance of Cohesion reflecting green patches connectivity was 10.33%. In terms of the internal influencing microclimate factors of green space carbon cycle, relative humidity, air temperature and wind speed, had a more significant influence, with the importance degree of influence being 33.50, 29.02 and 10.29%, respectively. Compared with the influence effect between the factors of the bioclimate, the index of photosynthetically active radiation was greater than the influence of the vapor flux. The study provides a reasonable explanation for the theoretical of coupling carbon sink enhancement of hydrological and green spatial factors. [ABSTRACT FROM AUTHOR]

The interaction between water and green spaces holds significant importance as an urban carbon sink, but there has been insufficient attention to how the specific morphology of waterfront landscapes affects their capacity for carbon sink. This study focuses on typical riverfront spaces in Shanghai, employing an improved Carnegie-Ames-Stanford-Approach (CASA) model fused with remote sensing spatiotemporal images to simulate vegetation fixed carbon within urban riverfront green spaces. Furthermore, an interpretable machine learning method was utilized to unveil the mechanism driving spatial heterogeneity in carbon sink efficiency. The results reveal the carbon sink efficiency of urban riverfront green spaces exhibits noticeable spatial heterogeneity, varying according to the location, type, scale, and river elements; The internal green component factors, including vegetation coverage and tree green ratio, along with surrounding environmental factor water surface ratio, are key factors influencing the carbon sinks efficiency; Hydrological elements within specific thresholds, namely, water surface ratio ranges between 0.245 and 0.281, can effectively enhance the carbon sink capacity of green spaces. And the maximum influencing value of distance from the water body is about 1800 m. The study contributes to developing a more scientific layout for climate-adaptive urban riverfront green spaces on the mesoscale. • Green carbon sink efficiency is affected by spatial morphology and the surrounding environment. • Hydrological elements can enhance carbon sink efficiency in riverfront green patches. • Landscape spatial morphology elements interact with each other during the carbon sequestration process. [ABSTRACT FROM AUTHOR]