Fine-Scale Assessment of Greenhouse Gases Fluxes from a Boreal Peatland Pond

Abstract

Ponds are abundant in the boreal peatland landscape, which are potential hotspots for greenhouse gas (GHG) emissions. However, compared to large lakes, ponds are difficult to identify by satellite, and they have not been adequately studied. Here, we observed methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) fluxes in the growing season at three sites along the water table gradient from the pelagic zone, littoral zone and bog across a shallow pond in a boreal peatland landscape in Northeastern China. The results showed that the littoral zone, dominated by herb Carex, was the hotspot for CH4 emissions. CH4 fluxes in littoral zone averaged 78.98 ± 19.00 mg m−2 h−1. The adjacent bog was a weak source of CH4 emissions, with an average flux of 0.07 ± 0.05 mg m−2 h−1. Within the pond, CH4 was mainly emitted through ebullition, accounting for 88.56% of the total CH4 fluxes, and the ebullition fluxes were negatively correlated with dissolved oxygen (DO). CO2 fluxes were highest in the pelagic zone, with an average of 419.76 ± 47.25 mg m−2 h−1. Wind and strong sediment respiration were key factors that led to the high fluxes. The observed three sites were all atmospheric N2O sinks ranging from −0.92 to −10.90 μg m−2 h−1. This study highlights the spatial variation in greenhouse gas fluxes from the pond and its adjacent bog, ignoring the ecotone area may underestimate CH4 fluxes. Although ponds are a hotspot for CH4 and CO2 emissions, they can also be a sink for N2O, which provides a reference for the quantification of global pond GHG fluxes. Therefore, finer-scale in situ observations are necessary to better understand the feedback of permafrost peatland ponds to global warming.