Soil seed banks of an old-growth forest and an adjacent conifer plantation in a medium altitude region in Shikoku, Japan

Abstract

We investigated the composition of soil seed banks both in an old-growth forest and an adjacent conifer plantation (Cryptmeria japonica) in Shikoku, Japan. The old-growth forest was mainly composed of temperate conifers and evergreen oaks. Twenty-nine soil samples (20cm × 30cm × 5cm in depth) were collected from the old-growth forest (10 on the ridge, 8 in the canopy gap and 11 on the slope) and 36 from the plantation. We counted emergent seedlings in the soil samples placed in an open space, and estimated the composition of soil seed banks. In the old-growth forest, there were an estimated 386 seeds/m^2 of 22 species on the slope, 158 seeds/m^2 of 11 species on the ridge and 119 seeds/m^2 of 8 species in the canopy gap. Canopy-tree species of the old-growth forest were not included in the soil seed bank except for Betula grossa. On the other hand, 383 seeds/m^2 of 38 species were detected on the slope of the C. japonica plantation showing higher species richness than the old-growth forest. It was assumed that large and intermittent human disturbance in the conifer plantation would accelerate the abundance of herbaceous species and pioneer species in the soil seed bank.