As a result of field research of 1996-2010 in the northern- and middle-boreal subzones of European Russia, the dependences of plant species percent cover in Scots pine forests (taken totally, upland vs. bog forests, and by groups of associations) upon bedrock type (silicate vs. carbonate/sulfate) and soil texture (sand vs. loamy sand and loam) were estimated using pair-wise group mean comparisons by Student t-test. Patterns in the affiliation of different European North pine forest syntaxa to silicate or carbonate/sulfate bedrock are confirmed at a species level. The pine forests on silicate bedrock are characterized by a numerous "cortege" of acidophyte species. The presence of calciphytes has just a minor effect on the positive flora differentiation of pine forests on dolomite or gypsum bedrock. The main reasons for establishment of species on carbonate/sulfate bedrock or for increase in their cover are reduction in competitive pressure on the part of acidophytes, preference for soils with an increased level of nutrition or erosion demands of several species, as well as stress-tolerance. There are several groups in the pine forest flora which are distinguished by the restriction of ecological optima of the plant species they consist of, as expressed by the mean percent cover of the latter, to soils of different texture. The group most numerous in species is that of oligotrophic and mesotrophic-oligotrophic plants bound to sand or shallow peat underlain by sand. The group of mesotrophic plants on sandy loam and true loam is the second richest in species; the latter are rather various in their soil moisture requirements. The increase in the plant cover on loams and sandy loam due to attenuation of competitive pressure from oligotrophic dwarf shrubs is also typical of some mesotrophic-oligotrophic species. At the same time, many plant species growing in pine forests seem bedrock- and soil texture-neutral. The Scots pine Pinus sylvestris should be considered a moderately mesotrophic-oligotrophic species in the European North according to both our research and phytoindication scales. It demonstrates a slight decline in canopy density on loam, if compared to loamy sand and sand. The simulation model of N. I. Kazimírov, predicting maximal canopy density and production of pine forests on loam due to soil physics regularities, should be revised.
There are several groups in the pine forest flora which are distinguished by the restriction of ecological optima of plant species they consist of, expressed by projective cover means of the latter, to soils of different texture. Oligotrophic and mesotrophic-oligotrophic plants bound to sand or shallow peat underlain by sand are most numerous in species number. Mesotrophic species on sandy loam and true loam are second best and rather various due to their soil moisture requirements. The increase in cover on loams and sandy loam due to the competitive pressure loose on the side of oligotrophic dwarfshrubs is also typical of some mesotrophic-oligotrophic species. At the same time, many plant species growing in pine forests seem bedrock- and soil texture-neutral.
The Scots pine Pinus sylvestris should be considered moderately mesotrophic-oligotrophic species in the European North according to both our research and phytoindication scales. It demonstrates a slight decrease in canopy density on loam, if compared to loamy sand and sand. The simulation model of N. I. Kazimirov [1995], predicting maximal canopy density and production of pine forests on loam due to soil physics regularities, should be revised.