N2O AND CH4 EMISSIONS FROM NATURALLY WET AND DRAINED NUTRIENT-RICH ORGANIC FOREST SOILS

Abstract

According to general knowledge rewetting of drained organic soils is a measure that can reduce net greenhouse gas emissions from ecosystem, however there is lack of evidence that approves such an assumption in hemiboreal forests. The aim of the study was to quantify N₂O and CH₄ flux from nutrient-rich organic soils in naturally wet (NWS) and drained (DS) hemiboreal forest sites in Latvia.

In central Latvia, 26 NWS (Dryopterioso–caricosa and Filipendulosa) and DS (Oxalidosa turf. mel.) were selected to evaluate annual N₂O and CH₄ soil flux by manual chamber method. Gas sampling was performed once a month in five replicates in every sampling plot for period of one year covering all seasons from October of 2019 till November of 2020. During gas sampling soil temperature and groundwater level were measured. In addition, soil and groundwater was sampled and tested.

Study results show that soil CH₄ flux has strong correlation with groundwater level and weak correlation with soil temperature in booth DS and NWS. Moderate correlation between soil temperature and N₂O flux were found in DS, however in rest of the study sites significant impact of soil temperature and groundwater level on N₂O flux was not found. Estimated annual average soil CH₄ flux is average ‑3.5±1.0 kg C‑CH₄ ha^-1 yr^-1 in DS and average 100.6±101.0 kg C‑CH₄ ha^-1 yr^-1 in NWS. While estimated annual average soil N₂O flux is average 1.1±0.4 kg N‑N₂O ha^‑1 yr^-1 in DS and 2.6±0.9 kg N‑N₂O ha^-1 yr^-1 in NWS.