Author(s)

Deepa Dhital^1*, Rabina Manandhar², Puruswattam Manandhar², Sanu Raja Maharjan²

¹Faculty of Science, Nepal Academy of Science and Technology (NAST), Kathmandu, Nepal.
²Department of Environmental Science, Khwopa College, Kathmandu, Nepal.

Soil CO₂ efflux is an ongoing process of respiration from soil; plant parts/ microbes below the ground to the atmosphere which is known for faster cycling of carbon sources. A large portion of carbon sequestered and fixed by forests is returned to the atmosphere through soil CO₂ efflux and multiple controlling parameters mainly temperature, precipitation, and growth factors interact with the soil CO₂ efflux variation. This study assessed the soil CO₂ efflux every month for consecutive 2-years (August 2015 to July 2017) by using the closed chamber method to determine the role of ecological parameters that govern the soil CO₂ efflux and its temporal modification in a sub-tropical mixed forest of central region in Nepal. The results of this study manifested that soil CO₂ efflux accounted 63.2% (y = 31.96e^0.128x), 71.3% (y = 44.77e^0.123x) and 64.5% (y = 44.11e^0.117x) variations in soil temperature with significantly (p < 0.05) exponential positive relation in the year 2015/2016, 2016/2017 and the two years when merged. And the temperature sensitivity value (Q₁₀) of the soil CO₂ efflux was 3.6, 3.4, and 3.2, respectively. Soil water content also expressed significantly (p < 0.05) positive exponential effect on soil CO₂ efflux and accounted 62.0% (y = 138.3e^0.057x), 46.1% (y = 88.42e^0.052x) and 40.5% (y = 133.1e^0.0447x) in its variability in different years and the merged years. Evident variations of soil CO₂ efflux, soil temperature, soil water content, and litter were observed in the forest seasonally and inter-annually. Two years mean total annual soil CO₂ efflux of the forest was estimated at 904.76 g C·m^-2·y^-1. The study revealed that sub-tropical forests could be more influenced by precipitation regimes in progressing warm climates i.e. vulnerable to climate change, illustrating the comprehensive dynamics of the representative forest carbon cycle in the tropical region.

Soil CO₂ Efflux, Environmental Parameters, Temperature Sensitivity (Q₁₀), Sub-Tropical Forest, Climate Change

Dhital, D. , Manandhar, R. , Manandhar, P. and Maharjan, S. (2022) Soil CO₂ Efflux Dynamics and Its Relationship with the Environmental Variables in a Sub-Tropical Mixed Forest. Open Journal of Forestry, 12, 312-336. doi: 10.4236/ojf.2022.123017.