10:45 〜 12:15
[ACG39-P01] Response of CO2 fluxes to precipitation event in a grassland ecosystem in central Mongolia
キーワード：Chamber, Dryland, Climate change, Respiration, Photosynthesis, Carbon cycle
Precipitation events remarkably influence the dynamics of CO2 fluxes like net ecosystem CO2 exchange (NEE), ecosystems respiration (Re), and gross primary production (GPP), especially in water-limited semi-arid and arid regions. But the magnitude of the response varies in each ecosystem and the study. Understanding the mechanism and the magnitude of the response of CO2 fluxes to precipitation events is becoming more and more important because of the changing precipitation pattern due to global climate change.
This study was conducted in a grassland ecosystem in Bayan-Unjuul in Mongolia in early August 2022. In the study site, we set 6 rectangle frames (inner size: 29.6 cm × 45.6 cm) made of aluminum flames and aluminum plates for CO2 flux measurement. After one night from the setup, we measured NEE with no shading and Re under complete shading in the daytime. GPP was calculated as Re minus NEE. For CO2 flux measurement, we used a portable automated chamber measurement system consisting of a transparent cuboid chamber and a control box that includes a datalogger (CR1000, Campbell Scientific Inc., Logan, UT, USA) and a CO2 analyzer (LI-830, LI-COR, Lincoln, NE, USA). The measurement was conducted before (Aug 5) and after (Aug 6) the precipitation event.
Both GPP and Re significantly increased (about 3.2 times for GPP and 4.0 times for Re) after the precipitation event (precipitation size = 7.6 mm d-1) compared with each flux value before the precipitation (p < 0.01), but there was no significant change in NEE (p > 0.05). This point suggests that the productivity of the herbivorous vegetation in the study site was remarkably promoted by the precipitation event, but the promotion was concealed by the activated respiratory components like soil organic carbon decomposition by microbes and plant respiration after the precipitation event. To better understand the response of CO2 fluxes to precipitation in this site, we will further need to examine CO2 flux responses in the case of different precipitation sizes.
This study was conducted in a grassland ecosystem in Bayan-Unjuul in Mongolia in early August 2022. In the study site, we set 6 rectangle frames (inner size: 29.6 cm × 45.6 cm) made of aluminum flames and aluminum plates for CO2 flux measurement. After one night from the setup, we measured NEE with no shading and Re under complete shading in the daytime. GPP was calculated as Re minus NEE. For CO2 flux measurement, we used a portable automated chamber measurement system consisting of a transparent cuboid chamber and a control box that includes a datalogger (CR1000, Campbell Scientific Inc., Logan, UT, USA) and a CO2 analyzer (LI-830, LI-COR, Lincoln, NE, USA). The measurement was conducted before (Aug 5) and after (Aug 6) the precipitation event.
Both GPP and Re significantly increased (about 3.2 times for GPP and 4.0 times for Re) after the precipitation event (precipitation size = 7.6 mm d-1) compared with each flux value before the precipitation (p < 0.01), but there was no significant change in NEE (p > 0.05). This point suggests that the productivity of the herbivorous vegetation in the study site was remarkably promoted by the precipitation event, but the promotion was concealed by the activated respiratory components like soil organic carbon decomposition by microbes and plant respiration after the precipitation event. To better understand the response of CO2 fluxes to precipitation in this site, we will further need to examine CO2 flux responses in the case of different precipitation sizes.