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首页> 美国卫生研究院文献>PLoS Clinical Trials >Isotopic compositions of ground ice in near-surface permafrost in relation to vegetation and microtopography at the Taiga–Tundra boundary in the Indigirka River lowlands, northeastern Siberia
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Isotopic compositions of ground ice in near-surface permafrost in relation to vegetation and microtopography at the Taiga–Tundra boundary in the Indigirka River lowlands, northeastern Siberia

机译：西伯利亚东北部英迪吉尔卡河低地大河-滕德拉边界的近地表多年冻土中地下冰的同位素组成与植被和微形貌的关系

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摘要

The warming trend in the Arctic region is expected to cause drastic changes including permafrost degradation and vegetation shifts. We investigated the spatial distribution of ice content and stable isotopic compositions of water in near-surface permafrost down to a depth of 1 m in the Indigirka River lowlands of northeastern Siberia to examine how the permafrost conditions control vegetation and microtopography in the Taiga–Tundra boundary ecosystem. The gravimetric water content (GWC) in the frozen soil layer was significantly higher at microtopographically high elevations with growing larch trees (i.e., tree mounds) than at low elevations with wetland vegetation (i.e., wet areas). The observed ground ice (ice-rich layer) with a high GWC in the tree mounds suggests that the relatively elevated microtopography of the land surface, which was formed by frost heave, strongly affects the survival of larch trees. The isotopic composition of the ground ice indicated that equilibrium isotopic fractionation occurred during ice segregation at the tree mounds, which implies that the ice formed with sufficient time for the migration of unfrozen soil water to the freezing front. In contrast, the isotopic data for the wet areas indicated that rapid freezing occurred under relatively non-equilibrium conditions, implying that there was insufficient time for ice segregation to occur. The freezing rate of the tree mounds was slower than that of the wet areas due to the difference of such as soil moisture and snow cover depends on vegetation and microtopography. These results indicate that future changes in snow cover, soil moisture, and organic layer, which control underground thermal conductivity, will have significant impacts on the freezing environment of the ground ice at the Taiga–Tundra boundary in northeastern Siberia. Such changes in the freezing environment will then affect vegetation due to changes in the microtopography of the ground surface.
机译：预计北极地区的变暖趋势将引起剧烈变化，包括多年冻土退化和植被转移。我们调查了西伯利亚东北部英迪吉尔卡河低地近1m深处的近地表多年冻土中冰含量和水的稳定同位素组成的空间分布，以研究多年冻土条件如何控制Taiga-Tundra边界的植被和微地貌生态系统。在落叶松树生长的微地形高海拔地区（树丘），冷冻土壤层的重量水分含量（GWC）明显高于湿地植被（即湿润地区）的低海拔地区。观察到的在树丘中具有高GWC的地冰（富含冰的层）表明，由霜冻形成的陆地表面相对较高的微观形貌强烈影响了落叶松树的生存。地下冰的同位素组成表明，在树丘的冰分离过程中发生了平衡的同位素分馏，这意味着冰形成的时间足以使未冻结的土壤水迁移到冰冻的前沿。相反，湿区的同位素数据表明在相对非平衡的条件下发生了快速冻结，这意味着没有足够的时间发生冰分离。由于土壤水分和积雪的差异取决于植被和微地形，树木丘的冻结速度比湿润地区的冻结速度慢。这些结果表明，控制地下热导率的积雪，土壤水分和有机层的未来变化将对西伯利亚东北部Taiga-Tundra边界处的地下冰的冻结环境产生重大影响。由于地表微观形貌的变化，这种冻结环境的变化将影响植被。

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