Evidence of High Microbial Abundance and Spatial Dependency in Three Arctic Soil Ecosystems

Microbial spatial heterogeneity has significant implications for ecological processes. Although microbial spatial patterns have been investigated agricultural and pristine soil ecosystems, little information is available on microbial spatial scaling in Arctic soils and how it is correlated with soil resources. In this comprehensive study, we assessed microbial abundance in 279 soil samples collected from three Canadian Arctic ecosystems and elucidated microbial spatial heterogeneity from fine (10 cm) to large (300 m) scales. Our results demonstrate that the abundance of archaeal 16S rRNA, bacterial 16S rRNA, and fungal 18S rRNA ITS gene copies (10(8)-10(11), 10(8)-10(10), and 10(8)-10(10) per gram of dry soil, respectively) in Arctic soils is similar to agricultural and pristine soils. Microbial spatial distribution is well structured in Arctic soils and shows high spatial dependency (0.50-0.99) at the scale of measurement of the experiment. The spatial range of microbial distribution is regularly <3 m which may be attributed to the periglacial processes such as thermokarst, cryoturbation, and gelifluction. Microbial spatial distribution is significantly (P < 0.01) correlated to the soil moisture, pH, dissolved organic C, dissolved organic N, total organic C, and total N content; however, the correlation is more consistent in Histels than Orthels or Turbels.