Permafrost Causes Unique Fine-Scale Spatial Variability Across Tundra Soils

Abstract Spatial analysis in earth sciences is often based on the concept of spatial autocorrelation,
expressed by W. Tobler as the first law of geography: “everything is related to everything else, but near
things are more related than distant things." Here, we show that subsurface soil properties in permafrost
tundra terrain exhibit tremendous spatial variability. We describe the subsurface variability of soil organic
carbon (SOC) and ground ice content from the centimeter to the landscape scale in three typical tundra
terrain types common across the Arctic region. At the soil pedon scale, that is, from centimeters to 1–2 m,
variability is caused by cryoturbation and affected by tussocks, hummocks and nonsorted circles. At the
terrain scale, from meters to tens of meters, variability is caused by different generations of ice-wedges.
Variability at the landscape scale, that is, ranging hundreds of meters, is associated with geomorphic
disturbances and catenary shifts. The co-occurrence and overlap of different processes and landforms
creates a spatial structure unique to permafrost environments. The coefficient of variation of SOC at the
pedon scale (21%–73%) exceeds that found at terrain (17%–66%) and even landscape scale (24%–67%).
Such high values for spatial variation are otherwise found at regional to continental scale. Clearly,
permafrost soils do not conform to Tobler's law, but are among the most variable soils on Earth. This
needs to be accounted for in mapping and predictions of the permafrost carbon feedbacks through various
ecosystem processes. We conclude that scale deserves special attention in permafrost regions.