FIG 4.

Multivariate analysis of the bacterial communities based on the relative abundances of bacterial phyla and proteobacterial classes estimated by 16S rRNA gene pyrosequencing analysis. Multivariate analysis was conducted separately for each type of tree stand: beech, coppice with standards, and Corsican pine. The same analysis was conducted for each mineral type, excluding the bulk soil samples: obsidian, apatite, and calcite. For legibility, the samples are presented as follows: orange, stand of beech; green, coppice with standards; blue, Corsican pine stand; circles, calcite samples; squares, apatite samples; triangles, obsidian samples; open diamonds, bulk soil samples. Vectors show the direction of maximum change for variables and longer arrows indicate a greater change in relative abundance. The percentages of the total variance explained by the first two axes, PC1 and PC2, are presented on each graph.