EGU21-15979, updated on 21 Oct 2023
https://doi.org/10.5194/egusphere-egu21-15979
EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Long-term soil methane uptake in a mature pine forest in Soontaga Forest Station, Estonia

Muhammad Kamil Sardar Ali1, Ülo Mander1,2, Thomas Schindler1,2, Katerina Machacova1,2, Kaire Rannik3, Veiko Uri4, and Kaido Soosaar1,2
Muhammad Kamil Sardar Ali et al.
  • 1Department of Geography, Institute of Ecology & Earth Sciences, University of Tartu, Tartu, Estonia
  • 2Global Change Research Institute of the Czech Academy of Sciences, Brno, Czech Republic
  • 3Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, Estonia
  • 4Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Tartu, Estonia

Methane (CH4) has high global warming potential, and its atmospheric concentration is increasing rapidly at the present rate of 0.3% yr-1. Forest ecosystems cover a large part of the biosphere and play a significant role in climate change. Upland forest soils are considered as important terrestrial sinks for atmospheric CH4; however, the complex interactions between microbial processes of CH4 production and oxidation, and environmental drivers are not well understood. Balance of CH4 in the forest ecosystems depends on two main natural processes, i.e., anaerobic methanogenesis and aerobic methanotrophy, driven by multiple environmental factors. A forest ecosystem's ability to exchange CH4 depends on the soil type, environmental conditions, species composition, living trees and deadwood, age and health conditions of the tree stand, and their CH4 balance can vary between seasons and years.

In this study, we present long-term CH4 fluxes (from 2015 to 2019) in a 60-200-year-old coniferous forest site of Scots pine (Pinus sylvestris) grown on loose sandy soil in Soontaga research station (58°01'N 26°04'E) in Estonia. The fluxes of CH4 were measured every two weeks, using a manual static soil chamber (n = 6) and gas chromatography method. Air temperature, precipitation and humidity, and soil moisture and temperature (10 cm depth) were measured continuously. The average annual temperature and precipitation recorded were 7.3 + 1.0 °C and 54.3 + 3.9 mm, respectively.

The results showed that mature pine forest soil was an annual net sink of CH4: −21.14 + 0.59 g ha−‍1 yr-1 (mean + SE). No significant difference (p < 0.05) was found between the soil CH4 uptake and tree age. Methane uptake correlated negatively (r= 0.61, p < 0.05) with soil temperature and showed similar seasonal dynamics being highest during the vegetation period (Apr-Oct) and lowest during the non-vegetation period (Nov-Mar). The highest CH4 uptake (−36.93 g ha−‍1) was observed in July 2018, the warmest and driest month during the overall period. Even though soil moisture was only weakly correlated (r2 = 0.15, p < 0.05) with CH4 uptake, the CH4 flux was affected by precipitation. As a result of this, it is noticed that CH4 uptake in the cold and wet conditions decreased with increasing precipitation in winter and increased with warming during warm and dry conditions in summer.

Concluded, our coniferous pine forest was sequestering CH4 during the investigated five years. The soil CH4 uptake could be explained by CH4 oxidation at optimal temperature in the water-unsaturated surface soil regulating the soil's microbial activity.

How to cite: Sardar Ali, M. K., Mander, Ü., Schindler, T., Machacova, K., Rannik, K., Uri, V., and Soosaar, K.: Long-term soil methane uptake in a mature pine forest in Soontaga Forest Station, Estonia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15979, https://doi.org/10.5194/egusphere-egu21-15979, 2021.

Corresponding displays formerly uploaded have been withdrawn.