Data from: Ground ice melt in the high Arctic leads to greater ecological heterogeneity

1. The polar desert biome of the Canadian high Arctic Archipelago is currently experiencing some of the greatest mean annual air temperature increases on the planet, threatening the stability of ecosystems residing above temperature-sensitive permafrost. 2. Ice wedges are the most widespread form of ground ice, occurring in up to 25% of the world's terrestrial near-surface, and their melting (thermokarst) may catalyze a suite of biotic and ecological changes, facilitating major ecosystem shifts. 3. These unknown ecosystem shifts raise serious questions as to how permafrost stability, vegetation diversity, and edaphic conditions will change with a warming high Arctic. Ecosystem and thermokarst processes tend to be examined independently, limiting our understanding of a coupled system whereby the effect of climate change on one will affect the outcome of the other. 4. Using in-depth, comprehensive field observations and a space-for-time approach, we investigate the highly structured landscape that has emerged due to the thermokarst-induced partitioning of microhabitats. We examine differences in vegetation diversity, community composition, and soil conditions on the Fosheim Peninsula, Ellesmere Island, Nunavut. We hypothesize that: (i) greater ice wedge subsidence results in increased vegetation cover due to elevated soil moisture, thereby decreasing the seasonal depth of thaw and restricting groundwater outflow; (ii) thermokarst processes result in altered vegetation richness, turnover, and dispersion, with greater microhabitat diversity at the landscape scale; (iii) shifts in hydrology and plant community structure alter soil chemistry. 5. We found that the disturbance caused by melting ice wedges catalyzes a suite of environmental and biotic effects: topographical changes, a new hydrological balance, significant species richness and turnover changes, and distinct soil chemistries. Thermokarst areas favour a subset of species unique from the polar desert and are characterized by greater species turnover (β-diversity) across the landscape. 6. Synthesis. Our findings suggest that projected increases of thermokarst in the polar desert will lead to the increased partitioning of microhabitats, creating a more heterogeneous high arctic landscape through diverging vegetation communities and edaphic conditions, resulting in a wetland-like biome in the high Arctic that could replace much of the ice-rich polar desert.

1. 加拿大高北极群岛的极地荒漠生物群系，目前正经历全球范围内最为显著的年平均气温升幅之一，这正威胁着栖息于对温度敏感的永久冻土（permafrost）之上的生态系统稳定性。
2. 冰楔（ice wedges）是分布最广泛的地下冰形态，覆盖全球近地表陆地面积的25%之多，其消融引发的热融喀斯特（thermokarst）效应可能触发一系列生物与生态变化，推动生态系统发生重大转变。
3. 这些未知的生态系统转变，引发了严峻的疑问：随着高北极地区变暖，永久冻土稳定性、植被多样性以及土壤条件（edaphic conditions）将发生何种变化？生态系统过程与热融喀斯特过程往往被独立研究，这限制了我们对耦合系统的认知——气候变化对其中一方的影响，会改变另一方的演化结果。
4. 本研究借助深入全面的野外观测与空间替代时间（space-for-time）方法，探究了因热融喀斯特作用导致微生境分区而形成的高度结构化景观。我们于努纳武特地区埃尔斯米尔岛的福谢姆半岛，调查了植被多样性、群落组成与土壤条件的差异。我们提出如下假说：(i) 冰楔沉降程度越高，土壤水分含量越高，植被覆盖度随之提升，进而减小季节解冻深度并限制地下水外流；(ii) 热融喀斯特过程会改变植被丰富度、周转速率与扩散格局，在景观尺度上提升微生境多样性；(iii) 水文与植物群落结构的变化会改变土壤化学性质。
5. 研究发现，冰楔消融引发的扰动触发了一系列环境与生物效应：地形变化、新的水文平衡、显著的物种丰富度与周转变化，以及独特的土壤化学特征。热融喀斯特区域青睐一类区别于极地荒漠的特有物种，其特征为全景观范围内更高的物种周转速率（β多样性（β-diversity））。
6. 总结。本研究结果表明，极地荒漠中热融喀斯特作用的预期增强，将推动微生境分区程度进一步提升，通过分化植被群落与土壤条件，形成更为异质化的高北极景观，最终可能形成类似湿地的生物群系，取代大片富冰极地荒漠。