EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Seasonal variability and magnitude of soil CO2 fluxes in a warming experiment in a secondary subtropical forest in Hong Kong

Duo Lou1, Naishen Liang2, and Derrick Yuk Fo Lai1
Duo Lou et al.
  • 1The Chinese University of Hong Kong, Geography & Resource management, Hong Kong, China (
  • 2Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan (

The increase of CO2 in the atmosphere has led to warming of the Earth’s surface and other climate changes. As heterotrophic respiration has great potential to increase atmospheric CO2 concentrations, it is important to quantify the variation in soil CO2 emission and to find its control factors under climate change. Though there are numerous studies about the warming effect on soil CO2 fluxes, the duration and variation of the effect remains unclear in subtropical forests. Here, we conducted a soil warming experiment with a multichannel automated chamber system in a secondary subtropical broad-leaved evergreen forest in Hong Kong. 15 chambers were set up in forest and were divided into 3 treatments, including a control, a root trenching, and an infrared-warming with root trenching chamber to determine the effect of warming on soil heterotrophic respiration in forest.

So far, after 3-year warming, soil temperature at 5 cm depth was increased by 2.47 °C, compared with the control chambers. Soil CO2 fluxes in experimental warming chambers have been significantly stimulated by 33.06%. There is significant relationship between soil temperature and soil CO2 fluxes in all the treatments, while in heating chambers, the relationship was weaker. The warming effect on soil CO2 emission was high in hot and humid summer, indicating that summer precipitation and the resulting soil moisture level also strongly influenced the soil warming effect in this forest. A moderately strong relationship was only found between soil moisture and temperature-normalized CO2 flux data in trenched chambers in 2020, when annual precipitation was the highest among 3 years. We found a significant reduction in the warming effect on soil respiration and highest Q10 values for soil respiration and its components in 2021, when annual precipitation was the lowest. Experimental warming significantly decreased Q10 value for heterotrophic respiration, which may be due to the reduction of soil moisture. Cross-correlation analysis showed that there was evident diel hysteresis between CO2 and soil temperature, while no significant seasonal hysteresis was observed. Longer-term monitoring on soil respiration under warming conditions is still needed to confirm if the reduction of warming effect is caused by microbial acclimation in our site.

How to cite: Lou, D., Liang, N., and Lai, D. Y. F.: Seasonal variability and magnitude of soil CO2 fluxes in a warming experiment in a secondary subtropical forest in Hong Kong, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13071,, 2022.