The eddy covariance technique is a micrometeorological method to directly measure the exchanges of carbon, water and energy between the vegetation and atmosphere. The spatial resolution of meteorological observation of fluxes can expand from tens of meters to kilometers. The eddy covariance method is most accurate when the contributing area of the fluxes is topographically flat, and vegetation extends uniformly within the footprint area. Currently there are more than 100 eddy covariance flux observation sites in China. Most of them are established in non鄄ideal conditions such as forest, undulating surface, patchy canopy area. Therefore, it is important to accurately interpret the ecological representativeness of flux data by evaluation of the spatial representativeness of its footprint in China. This paper reviews basic theories of the footprint, along with progress and applications about footprint functions. It discusses the research focus and difficulties when

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Urban green space plays a significant role on carbon cycling in urban areas. Accurate estimation of CO 2 fluxes above urban green space using the long鄄term field observation method provides critical information about climate change reactions and regional carbon sequestration evaluations. Continuous eddy鄄covariance measurements of CO 2 fluxes were conducted to analyze the carbon exchange status in 2009 and 2010. The analyses included daily variations in the CO 2 fluxes during different seasons, annual variations in light response parameters, including apparent light use efficiency (琢) and maximum photosynthetic productivity (P max). Annual variations in the net ecosystem CO 2 exchange (NEE) and the ecosystem respiration (R eco) were also studied. A tower located in the botanical garden of Dongguan with 4 levels and a total height of 20 m was used for the measurements. The CO 2 flux at a height of 20 m was analyzed to study the CO 2 exchange between an urban green space and the atmosphere interface. According to the eddy鄄covariance method and the detection limits of the instrument, abnormal data were removed to ensure accuracy. The daytime NEE and the photosynthetic active radiation (PAR) were used to

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