摘要：Earth hummocks constitute the most common surface structures of Arctic regions. In hummock tundra ecosystems, small mounds of earth alternate with depressions, the so-called interhummock areas. This study aimed at elucidating how differences in microtopography and associated variations in abiotic and biotic factors control biogeochemical cycles in hummock tundra soils. We assessed N pools and N transformation rates in hummocks and interhummock areas in the southern tundra subzone and along a soil-moisture gradient in the typical tundra subzone of the Taymyr Peninsula, Siberia, Russia. On a regional scale, N pools and transformation rates were positively related to latitude and therefore to temperature. Generally, wetter or waterlogged soil conditions tended to decrease gross mineralization rates and soil microbial N at least in interhummock areas. In contrast, at small spatial scales, soil microclimatic conditions were not the main determinant of the observed nitrogen cycling pattern. We found higher N pools and N gross mineralization rates at interhummock areas (wetter and cooler) compared to the hummocks (warmer and drier). The observed differences in N cycling between microsites of hummock tundra may be the consequence of different plant-cover and variable substrate inputs resulting from differences in microrelief.
