Schaller Jörg, Stimmler Peter, Göckede Mathias, Augustin Jürgen, Lacroix Fabrice, Hoffmann Mathias
Leibniz Center for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.
Leibniz Center for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.
Sci Total Environ. 2023 Apr 20;870:161943. doi: 10.1016/j.scitotenv.2023.161943. Epub 2023 Jan 31.
Arctic soils are the largest pool of soil organic carbon worldwide. Temperatures in the Arctic have risen faster than the global average during the last decades, decreasing annual freezing days and increasing the number of freeze-thaw cycles (temperature oscillations passing through zero degrees) per year as the temperature is expected to fluctuate more around 0 °C. At the same time, proceeding deepening of seasonal thaw may increase silicon (Si) and calcium (Ca) concentrations in the active layer of Arctic soils as the concentrations in the thawing permafrost layer might be higher depending on location. We analyzed the importance of freeze-thaw cycles for Arctic soil CO fluxes. Furthermore, we tested how Si (mobilizing organic C) and Ca (immobilizing organic C) interfere with the soil CO fluxes in the context of freeze-thaw cycles. Our results show that with each freeze-thaw cycle the CO fluxes from the Arctic soils decreased. Our data revealed a considerable CO emission below 0 °C. We also show that pronounced differences emerge in Arctic soil CO fluxes with Si increasing and Ca decreasing CO fluxes. Furthermore, we show that both Si and Ca concentrations in Arctic soils are central controls on Arctic soil CO release, with Si increasing Arctic soil CO release especially when temperatures are just below 0 °C. Our findings could provide an important constraint on soil CO emissions upon soil thaw, as well as on the greenhouse gas budget of high latitudes. Thus we call for work improving understanding of freeze-thaw cycles as well as the effect of Ca and Si on carbon fluxes, as well as for increased consideration of those factors in wide-scale assessments of carbon fluxes in the high latitudes.
北极土壤是全球最大的土壤有机碳库。在过去几十年中，北极地区的气温上升速度超过了全球平均水平，每年的冰冻天数减少，每年的冻融循环次数（温度波动穿过零度）增加，因为预计温度将在0°C左右波动更大。与此同时，随着季节融化的持续加深，北极土壤活性层中的硅（Si）和钙（Ca）浓度可能会增加，因为根据位置不同，融化的多年冻土层中的浓度可能更高。我们分析了冻融循环对北极土壤CO通量的重要性。此外，我们测试了硅（促进有机碳）和钙（固定有机碳）在冻融循环背景下如何干扰土壤CO通量。我们的结果表明，随着每一次冻融循环，北极土壤的CO通量都会下降。我们的数据显示，在0°C以下有相当数量的CO排放。我们还表明，随着硅增加和钙减少CO通量，北极土壤CO通量出现了明显差异。此外，我们表明，北极土壤中的硅和钙浓度都是北极土壤CO释放的主要控制因素，特别是当温度略低于0°C时，硅会增加北极土壤的CO释放。我们的研究结果可能对土壤解冻时的土壤CO排放以及高纬度地区的温室气体预算提供重要限制。因此，我们呼吁开展工作，增进对冻融循环以及钙和硅对碳通量影响的理解，并在高纬度地区碳通量的大规模评估中更多地考虑这些因素。
