CO₂ Flux Characteristics Of Different Plant Communities In A Urban Ecosystem

Under the background of global change,CO2 flux is one of the spot researches in the meteorological environment.The research content and scale are more colorful,from the natural ecosystem of the underlying surface to the urban ecosystem of the complex underlying surface,from dynamic characteristics of CO2 flux time to spatial dynamic characteristics of CO2 flux,from CO2 flux source range to CO2 flux footprint.The CO2 flux study not only contributes to carbon cycle research,but also provides a basis for the implementation of carbon management related policies.The underlying surface of the city is very complicated.Based on the carbon flux characteristics of the complex underlying ecosystem,the impact of urban vegetation management on CO2 flux characteristics can be explored,which can provide a scientific basis for urban management of low carbon city construction.The role of urban vegetation in the carbon cycle in the study of urban development has been explored in detail by many researchers.We focus on different plant community types to a greatly impact on CO2 flux,thus providing a scientific basis for urban low-carbon greening and reducing the impact of urban heat island effects.Based on the eddy covariance(EC)observation system,ART Footprint Tool,field plant inventory and ecological community classification,the classification of CO2 flux characteristics of different plant community types showed specifically includes the following findings:(1)The CO2 flux has different characteristics in different seasons.The seasonal variation of seasonality of carbon flux from November 2016 to October 2017 is mainly characterized by the longest time of carbon sink in summer,the duration is about 10 hours,and the peak value of carbon sink is-9.07?mol·m-2·s-1;the minimum carbon sink time in winter is about 7.5 hours,the peak value of carbon sink is-8.36?mol·m-2·s-1;the carbon sink time in spring and autumn is close,both are After 9 hours,the peaks at the carbon sink were 7.29?mol·m-2·s-1 and 7.15?mol·m-2·s-1,respectively.(2)The analysis of CO2 flux source area shows that the distance from the farthest point of CO2 flux to the tower in different seasons is distinct: the longest in winter is 1381 m,followed by 1301 m in summer,and the farthest distance in spring and autumn is 1283 m and 1185 m respectively.The farthest points in spring are mainly concentrated in 90°-150° and 0°-270°,the farthest points in summer are mainly distributed between 120°-180°,and the farthest points in autumn are concentrated in the range of 300 m from the flux tower.The farthest point distribution in winter is consistent with the prevailing wind direction,which is the northwest wind direction.(3)The contribution rates of CO2 fluxes of different vegetation community types are different.The annual average CO2 contribution rate of the Cinnamomum camphora-Trachycarpus fortune community,was 11.88%,and the Metasequoia glyptostroboides + Sabina chinensis community was the smallest,only 0.93%.Then the CO2 flux contribution rate of the same plant community was also very different,and the Cinnamomum camphora-Trachycarpus fortunei community,the contribution rate of CO2 in winter and summer is the largest,which is 11.16%.The CO2 contribution rate of Metasequoia glyptostroboides + Sabina chinensis community is the smallest in winter and summer,which is 0.35%.The general community summer is the season with the lowest contribution rate of CO2 flux,and the winter is the season with the highest contribution rate of CO2 flux,but the Cinnamomum camphora+ Salix babylonica community and the Cinnamomum camphora + Sabina chinensis community are opposite.(4)The characteristics of CO2 flux vary among different plant community types.The CO2 flux value of Metasequoia glyptostroboides community changed greatly,the difference between the maximum value and the minimum value was-4.02?mol·m-2·s-1,and the Cinnamomum camphora + Salix babylonica community was 8.48?mol·m-2·s-1.The mean value of CO2 flux in summer was the smallest,which was-6.41?mol·m-2·s-1,and the mean value of CO2 flux in the Cinnamomum camphora + Sabina chinensis community was the highest in summer,which was-1.33?mol·m-2·s-1.The difference between the minimum and maximum values of CO2 flux in one day was compared and analyzed.The peak value of Metasequoia glyptostroboides community,Cinnamomum camphora + Sabina chinensis and Cinnamomum camphora-Trachycarpus fortunei community was larger,-3.43?mol·m-2·s-1?2.46?mol·m-2·s-1,indicating that these three plant communities have strong absorption capacity for CO2 absorption.