Deciduous tree stems can become an important source of methane (CH4) and nitrous oxide (N2O) emissions especially in case of flooding or increase of the soil water-table level. So far, studies were mainly implemented in forests with organic soils, while limited information is available about mineral soils. Within this study we estimated the CH4 and N2O fluxes from the stem surface of silver birch, black alder and aspen in 16 study sites (forest stands) with drained and naturally wet mineral soils in Latvia to evaluate the impact of soil moisture conditions. We found that in forest stands with drained mineral soil, the mean CH4 fluxes from the tree stems were 10.2 ± 3.2 µg CH4-C·m-2·h-1 for aspen, 1.3 ± 2.6 µg CH4-C·m-2·h-1 for black alder, 4.5 ± 2.9 µg CH4-C·m-2·h-1 for silver birch. In forest stands with wet mineral soil, CH4 fluxes from the tree stems were higher for all tree species (21.1 ± 5.5 µg CH4-C·m-2·h-1 for aspen, 6.3 ± 2.4 µg CH4-C·m-2·h-1 for black alder, 10.3 ± 2.3 µg CH4-C·m-2·h-1 for silver birch) than in stands with drained soil. Similarly, higher N2O fluxes from the stem surface were found in forest stands with wet mineral soils for aspen and silver birch (4.1 ± 1.5 and 4.0 ± 1.5 µg N2O-N·m-2·h-1, respectively) than in forest stands with drained mineral soil (-0.8 ± 1.4 and 1.9 ± 1.5 µg N2O-N·m-2·h-1, respectively), while N2O fluxes for black alder were similar under drained and wet condition (3.8 ± 1.3 and 3.6 ± 1.3 µg N2O-N·m-2·h-1, respectively). However, high variation in CH4 and N2O fluxes was observed and the difference in mean fluxes between drained and wet conditions was not statistically significant. In general, the study shows that forest drainage can reduce CH4 and N2O fluxes from the surface of tree stems; however, due to the high variation of the fluxes more data are necessary to increase accuracy of projections of the studied greenhouse gases.
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Petaja et al. (2024) studied this question.