Declines in methane uptake in forest soils
Declines in methane uptake in forest soils
复制标题
DOI：
10.1073/pnas.1807377115
复制
发表时间：
2018-08
期刊：
影响因子：
--
通讯作者：
X. Ni;P. Groffman
中科院分区：
文献类型：
--
作者：
X. Ni;P. Groffman
意义 近几十年来，大气中的甲烷 (CH4) 浓度一直在迅速增加。森林土壤是大气CH4的主要汇，但长期原位观测的证据有限，因此人们对土壤CH4汇如何响应不断变化的环境条件知之甚少。我们在马里兰州巴尔的摩（1998-2016 年）和新罕布什尔州哈伯德布鲁克（2002-2015 年）的长期生态研究地点测量了土壤到大气的 CH4 净通量，发现这两个地点的 CH4 吸收量显着下降。此外，文献综述表明，世界各地森林土壤中 CH4 的吸收量也在下降，特别是降水量一直在增加的北纬 0-60 °的森林。我们的结论是，目前大面积区域的土壤 CH4 汇可能被高估。森林土壤是大气甲烷 (CH4) 的汇，在调节全球甲烷预算方面发挥着重要作用。然而，森林土壤吸收 CH4 是否受到全球环境变化的影响尚不清楚。我们测量了 20 世纪 90 年代末至 2010 年代中期美国东北部两个长期生态研究地点温带森林中土壤到大气的净 CH4 通量。我们发现，在此期间，马里兰州巴尔的摩城市和乡村森林的土壤 CH4 吸收量每年下降了 62% 和 53%，而新罕布什尔州哈伯德布鲁克的钙肥和参考森林则下降了 74% 和 89%。尽管氮沉降显着下降并且大气中甲烷浓度和温度增加，但这种减少仍然发生，这应该导致甲烷吸收增加。土壤 CH4 吸收量的减少似乎是由降水量和土壤水文通量的增加造成的。此外，对全球 CH4 吸收量的分析表明，从 1988 年到 2015 年，森林土壤中 CH4 吸收量平均减少了 77%，特别是在降水量不断增加的北纬 0 至 60 °N 的森林中。我们得出的结论是，全球多个地区的土壤 CH4 汇可能正在下降并且被高估。
Significance Atmospheric methane (CH4) concentration has been increasing rapidly over recent decades. Forest soils are a major sink for atmospheric CH4, but evidence from long-term in situ observation is limited, so little is known about how the soil CH4 sink responds to changing environmental conditions. We measured soil to atmosphere net CH4 fluxes at long-term ecological research sites in Baltimore, Maryland (1998–2016) and Hubbard Brook, New Hampshire (2002–2015) and found significant decreases in CH4 uptake at both sites. Moreover, a literature review showed that CH4 uptake in forest soils around the world is also declining, especially forests from 0–60 °N latitude, where precipitation has been increasing. We conclude that the current soil CH4 sink may be overestimated over large regional areas. Forest soils are a sink for atmospheric methane (CH4) and play an important role in modulating the global CH4 budget. However, whether CH4 uptake by forest soils is affected by global environmental change is unknown. We measured soil to atmosphere net CH4 fluxes in temperate forests at two long-term ecological research sites in the northeastern United States from the late 1990s to the mid-2010s. We found that annual soil CH4 uptake decreased by 62% and 53% in urban and rural forests in Baltimore, Maryland and by 74% and 89% in calcium-fertilized and reference forests at Hubbard Brook, New Hampshire over this period. This decrease occurred despite marked declines in nitrogen deposition and increases in atmospheric CH4 concentration and temperature, which should lead to increases in CH4 uptake. This decrease in soil CH4 uptake appears to be driven by increases in precipitation and soil hydrological flux. Furthermore, an analysis of CH4 uptake around the globe showed that CH4 uptake in forest soils has decreased by an average of 77% from 1988 to 2015, particularly in forests located from 0 to 60 °N latitude where precipitation has been increasing. We conclude that the soil CH4 sink may be declining and overestimated in several regions across the globe.