Abstract
Shanghai, China, is a city that is relatively representative of various cities in China due to its geographical location and socio-economic dynamics. The role of urban vegetation in the carbon cycle of urban developments in these types of cities is now being studied. We focus on identifying which urban plant community types have a greater influence on CO2 flux in cities, thus providing a scientific basis for low-carbon urban greening. Based on the eddy covariance (EC) observation system, ART Footprint Tool, plant inventory, and ecological community classification, we show that the CO2 flux characteristics of different plant communities vary temporally. The carbon sink duration during summer was the longest (up to 10 h) and the carbon sink duration was the shortest during winter (7.5 h). In addition, we discovered that the CO2 flux contribution rates of different plant community types are distinct. The annual average CO2 contribution rates of the Cinnamomum camphora-Trachycarpus fortunei community and the Metasequoia glyptostroboides+Sabina chinensis community are 11.88% and 0.93%, respectively. The CO2 flux contribution rate of the same plant community differs according to season. The CO2 contribution rate of the Cinnamomum camphora-Trachycarpus fortunei community exhibits local maxima during winter and summer, with a maximum difference of 11.16%. In contrast, the Metasequoia glyptostroboides+Sabina chinensis community has a CO2 contribution rate of 0.35% during the same period. In general, summer is the season with the lowest CO2 flux contribution rate of plant communities, and winter is the season with the highest CO2 flux contribution rate. However, the Cinnamomum camphora+Salix babylonica community and the Cinnamomum camphora+Sabina chinensis community present the opposite pattern. Finally, the diurnal variation characteristics of CO2 flux in different communities have the same trend, but the peak values differ significantly. Overall, daily CO2 flux peak value of the Metasequoia glyptostroboides community and the Cinnamomum camphora-Trachycarpus fortunei community indicate that these two plant communities exhibit a strong capacity for CO2 absorption in the study area. According to these research results, urban greening efforts in subtropical climates can increase the green space covered by the Cinnamomum camphora-Trachycarpus fortunei and the Metasequoia glyptostroboides community types when urban greening, so as to appropriately reduce the CO2 emitted into the atmosphere.
Highlights
Human activities are the main source of urban CO2
According to these research results, urban greening efforts in subtropical climates can increase the green space covered by the Cinnamomum camphora-Trachycarpus fortunei and the Metasequoia glyptostroboides community types when urban greening, so as to appropriately reduce the CO2 emitted into the atmosphere
The results show that the CO2 flux contribution rate of different plant fortunei community and the Cinnamomum camphora+Sabina chinensis community to the CO2 flux were communities varies significantly according to season
Summary
Human activities are the main source of urban CO2. Since the industrial revolution, the rapid increase of CO2 concentrations in the atmosphere has been demonstrated by scientists from different fields. The majority of studies of CO2 fluxes have concentrated on the seasonal changes of single vegetation-type ecosystems [7,8,9,10]. The application of the EC method to the CO2 exchange between the atmosphere and the surface in urban ecosystems can be used to better understand the dynamic characteristics and influencing factors of carbon in cities. Few studies have illustrated the effects of different vegetation communities on CO2 flux and identified the plant communities that influence these fluxes. This paper will explore the impact of different urban plant communities on CO2 flux to better explain the relationship between vegetation, CO2 , and related climate change mechanisms, to provide reference data for building green garden cities, and to offer a practical theoretical basis for the emission and absorption of CO2 in subtropical cities. This study will analyze the characteristics of CO2 flux footprints of different vegetation types via the Kormann and Meixner model (ART Footprint Tool), and it will obtain the characteristics of community types that are more effective in absorbing CO2
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