Figure 4

Partition of the topsoil (0–10 cm) and plants in different thermal zones of catena studied: (a) Element and mineral composition. Significant (p < 0.05) differences between composition of soils: 1—adjacent zones (I and II, II and III or III and IV), 2—zone I and other zones (II, III and IV), 3—in the zone under consideration and composition of soils both in zone I and in a cooler adjacent zone. The concentration of chemical elements and minerals are normalized to the composition in soils of zone I: depletion—blue and green, accumulation—yellow and red. Main groups of minerals (100%): cl—clay minerals (kaolinite, smectite, boehmite), ncl—non-clay minerals (microcline, albite, anorthite, clinoptilolite, heulandite, anatase, quartz, cristobalite), f—minerals of iron (pyrite, hematite, goethite, jarosite, marcasite). Clay minerals (100%): Sm—smectite, K—kaolinite, Bm—boehmite. (b) The thermophilic species observed along the catena on the phylogenetic tree of all the vascular plants occurred in the Valley of Geysers. (c) The key factors limiting plant species (black, non-thermal species; blue, facultative thermophytes; red, obligate thermophytes) growth within 1 × 1 m plots at the catena studied. 1–16, numbers of plots.