Vegetation green‐up date is more sensitive to permafrost degradation than climate change in spring across the northern permafrost region
Vegetation green‐up date is more sensitive to permafrost degradation than climate change in spring across the northern permafrost region
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DOI：
10.1111/gcb.16011
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发表时间：
2021-12
影响因子：
11.6
通讯作者：
Jian Wang;Desheng Liu
中科院分区：
文献类型：
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作者：
Jian Wang;Desheng Liu
全球气候变化极大地影响了北部多年冻土地区的植被春季物候，即返绿期（GUD）。 GUD 的变化调节生态系统的碳吸收，进一步反馈到当地和区域气候系统。现有的研究主要集中于气候因素的直接影响，如温度、降水和日照；然而，GUD 对变暖引起的永久冻土退化的反应（即间接影响）仍然难以捉摸。在这项研究中，我们通过分析卫星 GUD 与通过解冻开始 (SOT) 和活动层厚度 (ALT) 测量的永久冻土退化相关的长期趋势，研究了永久冻土退化对 GUD 的影响。我们发现 GUD、SOT 和 ALT 增厚的显着趋势 (p < 0.05)，空间平均斜率分别为 -2.1 天 decade−1、-4.1 天 decade−1 和 +1.1 cm decade−1。通过偏相关分析，我们发现超过一半的春季温度和GUD之间呈显着负相关的区域在考虑永久冻土退化后变得不显着。 GUD 对 SOT 和 ALT 分别表现出显性阳性反应（37.6% vs. 0.6%）和显性阴性反应（1.8% vs. 35.1%）。较早的SOT和较厚的ALT可以提高土壤水分的可用性，从而减轻植被绿化的水分胁迫。根据敏感性分析，41.7%的地区多年冻土退化是控制GUD变化的主导因素，而只有19.6%的地区受到其他气候因素（即温度、降水和日照）的主导。我们的结果表明，在不同植被类型中，GUD 对永冻土退化比春季直接气候变化更敏感，特别是在高纬度地区。这项研究揭示了多年冻土退化对植被 GUD 的重大影响，并强调了多年冻土状况对于更好地了解春季物候对未来气候变化的响应的重要性。
Global climate change substantially influences vegetation spring phenology, that is, green‐up date (GUD), in the northern permafrost region. Changes in GUD regulate ecosystem carbon uptake, further feeding back to local and regional climate systems. Extant studies mainly focused on the direct effects of climate factors, such as temperature, precipitation, and insolation; however, the responses of GUD to permafrost degradation caused by warming (i.e., indirect effects) remain elusive yet. In this study, we examined the impacts of permafrost degradation on GUD by analyzing the long‐term trend of satellite‐based GUD in relation to permafrost degradation measured by the start of thaw (SOT) and active layer thickness (ALT). We found significant trends of advancing GUD, SOT, and thickening ALT (p < 0.05), with a spatially averaged slope of −2.1 days decade−1, −4.1 days decade−1, and +1.1 cm decade−1, respectively. Using partial correlation analyses, we found more than half of the regions with significantly negative correlations between spring temperature and GUD became nonsignificant after considering permafrost degradation. GUD exhibits dominant‐positive (37.6% vs. 0.6%) and dominant‐negative (1.8% vs. 35.1%) responses to SOT and ALT, respectively. Earlier SOT and thicker ALT would enhance soil water availability, thus alleviating water stress for vegetation green‐up. Based on sensitivity analyses, permafrost degradation was the dominant factor controlling GUD variations in 41.7% of the regions, whereas only 19.6% of the regions were dominated by other climatic factors (i.e., temperature, precipitation, and insolation). Our results indicate that GUDs were more sensitive to permafrost degradation than direct climate change in spring among different vegetation types, especially in high latitudes. This study reveals the significant impacts of permafrost degradation on vegetation GUD and highlights the importance of permafrost status in better understanding spring phenological responses to future climate change.