Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark.
Glob Chang Biol. 2019 May;25(5):1704-1716. doi: 10.1111/gcb.14582. Epub 2019 Feb 25.
Vast amounts of carbon are bound in both active layer and permafrost soils in the Arctic. As a consequence of climate warming, the depth of the active layer is increasing in size and permafrost soils are thawing. We hypothesize that pulses of biogenic volatile organic compounds are released from the near-surface active layer during spring, and during late summer season from thawing permafrost, while the subsequent biogeochemical processes occurring in thawed soils also lead to emissions. Biogenic volatile organic compounds are reactive gases that have both negative and positive climate forcing impacts when introduced to the Arctic atmosphere, and the knowledge of their emission magnitude and pattern is necessary to construct reliable climate models. However, it is unclear how different ecosystems and environmental factors such as drainage conditions upon permafrost thaw affect the emission and compound composition. Here we show that incubations of frozen B horizon of the active layer and permafrost soils collected from a High Arctic heath and fen release a range of biogenic volatile organic compounds upon thaw and during subsequent incubation experiments at temperatures of 10°C and 20°C. Meltwater drainage in the fen soils increased emission rates nine times, while having no effect in the drier heath soils. Emissions generally increased with temperature, and emission profiles for the fen soils were dominated by benzenoids and alkanes, while benzenoids, ketones, and alcohols dominated in heath soils. Our results emphasize that future changes affecting the drainage conditions of the Arctic tundra will have a large influence on volatile emissions from thawing permafrost soils - particularly in wetland/fen areas.
大量的碳被束缚在北极的活动层和永冻层土壤中。随着气候变暖，活动层的深度在增加，永冻土正在融化。我们假设在春季，近地表活动层会释放出大量生物源挥发性有机化合物，而在夏末，解冻的永冻土也会释放这些化合物，随后在解冻的土壤中发生的生物地球化学过程也会导致排放。生物源挥发性有机化合物是反应性气体，当它们被引入北极大气时，会对气候产生负面影响和正面影响，因此，了解它们的排放规模和模式对于构建可靠的气候模型是必要的。然而，不同的生态系统以及环境因素（如永冻土融化后的排水条件）如何影响排放和化合物组成尚不清楚。在这里，我们表明，从高北极荒地和沼泽采集的冻结的活动层 B 层和永冻土在解冻时以及随后在 10°C 和 20°C 的培养实验中释放出一系列生物源挥发性有机化合物。沼泽土壤中的融水排水使排放速率增加了九倍，而在较干燥的荒地土壤中则没有影响。排放通常随温度升高而增加，沼泽土壤的排放模式主要由苯类和烷烃主导，而荒地土壤则以苯类、酮类和醇类为主。我们的研究结果强调，未来影响北极苔原排水条件的变化将对解冻的永冻土土壤的挥发性排放产生重大影响——特别是在湿地/沼泽地区。
