## 2 Materials and Methods  
### The Study Sites  
All samples of investigation were sampled in several key points in different natural zones in Russia, with natural and anthropogenic disturbed soils. Six key sites for soil sampling were selected. Sampling locations vary from the natural region of the southern taiga to the southern tundra. The locations of the sampling areas are presented in a geographic map (Figure 1).  
Figure 1: The sample plot locations (further on in the main text: B—Borovichy; E—Elizavetino; U—Ukhta; V—Vorkuta; N—Nadym; S—Salekhard).  
The first site--South taiga--Umbric Retisols in the surroundings of Borovichy city (sample code--B, Novgorod region, European part of Russia) with agricultural soils and newly formed soils of dumps of former heaps of mines. The climate in the region is continental, specifically humid continental. The site is located on the Msta River 170 km from Veliky Novgorod, 320 km from St. Petersburg, and 430 km from Moscow. The Novgorod region is located in the forest zone, which is divided into two subzones--taiga and mixed forests. Along with coniferous and softwood species, there is a small admixture of hardwood species (oak, linden, maple, elm, and ash). Significant areas of the southern taiga subzone are occupied by swamps and meadows.  
The second site--South taiga--Rendzic Leptosols in the vicinity of the Elizavetino settlement (sample code--E, Gatchina district, Leningrad region, European part of Russia) with agricultural soils and the soil of the bottom of a limestone quarry. The climate is transitional from marine to continental. The region is located in the southern taiga belt with a predominance of coniferous forests.  
The third site--Northern taiga--in the vicinity of Ukhta city (sample code--U, Komi republic, European territory of Russia) with sandy Podzol as mature soils and various Technosols. Located in the central part of the Komi Republic. The climate is continental subarctic with long, cold winters and short, warm summers.  
The fourth site--Tundra--in the vicinity of Vorkuta city (sample code--V, Komi republic, European territory of Russia) with Histic Gelisols as zonal soils and various primary soils on mining heaps and agricultural soils. Vorkuta is located in the Polar Urals about 150 km north of the Arctic Circle and 180 km from the coast of the Arctic Ocean. The climate is moderately continental. Winters are long and cold, summers are short, and warm in the south and cold in the north. The forests are dominated by spruce, pine, birch, aspen, larch, fir, and Siberian cedar occur. In tundras willows, bogwood, and dwarf birch prevail. The greatest species diversity is characterized by grasses, mostly perennial.  
The fifth site--the northern part of the Western Siberia investigation was conducted in the vicinity of Nadym city (sample code--N, forest tundra). Located on the left bank of the Nadym River, 290 km southeast of Salekhard. Nadym has a continental subarctic climate. The flora includes spruce, larch, gray alder, birch, Siberian cedar, and many shrubs (cowberries, blueberries, blueberries, etc.).  
The sixth site--Salekhard city (sample code--S, south tundra). The mature soils were Podzols and Gelisols, correspondingly, with agriculturally transformed soils and soils of the mining heaps of sandy quarries. The city is located on the Polui Upland of the West Siberian Plain at the confluence of the Polui River into the Ob River. Salekhard has a subarctic climate with short, mild summers and severely cold winters. The flora is represented by birch (mostly dwarf), willow, and the like. Diversity in low plants, herbs, and shrubs: Ledum, linguonberries, etc., are common.  
Thus, a wide spectra of locations have been included in our research. To maintain the comparability of results, samples were performed from a depth of 0-10 cm in all cases. The toposils were presented by A (humus) horizons, Ap (arable humus horizons), and Au (sod horizons of initial primary soils).