[A-CG39] Biogeochemical cycles in Land Ecosystem

[ACG39-01] Research on carbon budget in urban green area

*Tatsunori Tabata¹, Hirofumi Sugawara¹ (1.National Defence Academy)

Keywords:urban green area, net ecosystem production, seasonal variation

Green spaces in urban area mitigate the urban heat island and acts as a sink of CO₂. On the other hand, ecosystems in urban green spaces are affected by heat and pollutants from the surrounding urban areas. Then, heat balance and CO₂ exchange in urban green spaces may differ from those in rural forests. This point has not been well studied because there were small number of studies with micrometeorological measurements in urban green spaces. This study clarified CO₂ exchange in an urban green space with the measurements.The measurements are continued since 2009 in the Institute for Nature Study (200,000 m2) located in Shirokanedai, Minato-ku, Tokyo. The area is surrounded by mid-rise buildings and the metropolitan expressway. The green spaces was covered with forest canopy whose mean height was 14 m. The main green species whose DBH >= 10 cm or large number of individuals were the Trachycarpus fortunei, Castanopsis sieboldii, and Swida controversa. Area ratio of green space was deciduous broad-leave; 43%, evergreen broad-leave; 36%, monocotyledonous; 19%, and deciduous needle-leaf; 2%.The CO₂ flux has been measuring with an ultrasonic anemometer and an open-path gas analyzer at 20 m above the ground (6 m above the tree canopy) at the center of the forest canopy. The data were quality-controlled for the turbulence conditions, and gap-filled using nonlinear regression methods for the missing measurement runs.Seasonal and inter-annual variations in CO₂ exchange were analyzed. In monthly mean basis, CO₂ was absorbed from March to October. The maximum monthly absorption of carbon was 157 gC/m² /month in June. The maximum monthly emission was 35 gC/m² /month in December. The annual average of carbon sink from 2010 to 2021 was 652 gC/m²/year.