Subarctic soil carbon losses after deforestation for agriculture depend on permafrost abundance
Subarctic soil carbon losses after deforestation for agriculture depend on permafrost abundance
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DOI：
10.1111/gcb.16307
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发表时间：
2022-06
影响因子：
11.6
通讯作者：
Tino Peplau;J. Schroeder;E. Gregorich;C. Poeplau
中科院分区：
文献类型：
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作者：
Tino Peplau;J. Schroeder;E. Gregorich;C. Poeplau
由于气候变化，北方环极永久冻土区正在经历相当大的变暖，这使得农业生产扩大到不连续和连续的永久冻土区。将森林转化为耕地可能会进一步促进永久冻土的融化，并影响以前受到冻土保护的土壤有机碳。多年冻土丰度和森林砍伐对SOC储量的相互作用几乎没有研究。在这项研究中，土壤采样的18个农场横跨育空地区的永久冻土和非永久冻土，以量化土地利用变化的影响，从森林到耕地和草地的SOC股票。此外，土壤的物理和化学分级，以评估土地利用变化对不同功能的SOC库的影响。平均而言，受冻土影响的森林土壤失去了15.6 ± 21.3%的SOC时，转换为耕地和23.0 ± 13.0%时，转换为草地。在森林砍伐的土壤中没有检测到永久冻土，这表明土地利用的变化强烈地增强了变暖和随后的融化。相比之下，在没有冻土的网站SOC的变化不显着，但有轻微的趋势是积极的。SOC股票普遍较低的网站下没有永久冻土森林。此外，土地利用变化增加了矿物相关的SOC，而土地利用变化后颗粒有机物（POM）的命运取决于永久冻土的发生。土地利用变化后，多年冻土表现出显着的POM损失，而草地网站没有多年冻土获得POM在表土。结果表明，土地利用变化后土壤有机碳的去向主要取决于原始森林中冻土的丰度，而冻土丰度的变化更多地受气候条件的影响，而非土壤性质的影响。可以得出结论，特别是在不连续的永久冻土区，森林土壤的初始条件应考虑砍伐森林之前，以尽量减少其气候影响。
The northern circumpolar permafrost region is experiencing considerable warming due to climate change, which is allowing agricultural production to expand into regions of discontinuous and continuous permafrost. The conversion of forests to arable land might further enhance permafrost thaw and affect soil organic carbon (SOC) that had previously been protected by frozen ground. The interactive effect of permafrost abundance and deforestation on SOC stocks has hardly been studied. In this study, soils were sampled on 18 farms across the Yukon on permafrost and non‐permafrost soils to quantify the impact of land‐use change from forest to cropland and grassland on SOC stocks. Furthermore, the soils were physically and chemically fractionated to assess the impact of land‐use change on different functional pools of SOC. On average, permafrost‐affected forest soils lost 15.6 ± 21.3% of SOC when converted to cropland and 23.0 ± 13.0% when converted to grassland. No permafrost was detected in the deforested soils, indicating that land‐use change strongly enhanced warming and subsequent thawing. In contrast, the change in SOC at sites without permafrost was not significant but had a slight tendency to be positive. SOC stocks were generally lower at sites without permafrost under forest. Furthermore, land‐use change increased mineral‐associated SOC, while the fate of particulate organic matter (POM) after land‐use change depended on permafrost occurrence. Permafrost soils showed significant POM losses after land‐use change, while grassland sites without permafrost gained POM in the topsoil. The results showed that the fate of SOC after land‐use change greatly depended on the abundance of permafrost in the pristine forest, which was driven by climatic conditions more than by soil properties. It can be concluded that in regions of discontinuous permafrost in particular, initial conditions in forest soils should be considered before deforestation to minimize its climate impact.