Fig. 2
Microhabitat characteristics around seed-offer devices. Position of the 300 seed-offer devices according to the first two components of a PCA on ten vegetation and soil variables measured at the microhabitat scale. Microhabitats are identified by their a priori categorization at field according to previous studies of the soil seed bank [21, 22]: beneath tree canopy (black), beneath tall shrubs (green), beneath low shrubs (blue), beneath grasses (yellow) and bare soil (red). Smaller gray points were microhabitats with intermediate characteristics according to those criteria. Ellipsis include at least 90% cases in each category. Bars show the biomass of forb (full) and grass (open) seeds of each microhabitat category during the same winter of the field experiment (L. Marone, unpublished data). Relative sizes of bars look similar when number of seeds, instead of biomass, was represented (0.5 g/m2 ≈ 2000 seeds/m2; not shown)