Revegetation Patterns and Seedbank Structure on Abandoned Pastures in Northern Japan

Abstract

To compare revegetation patterns between native and exotic species on abandoned pastures in northern Japan, we surveyed the vegetation structure and the seedbank using a flotation technique in 140 1 1 m plots. Previously introduced grasses such as Poa pratensis, Phleum pratense, and Dactylis glomerata were abundant 20 yr after the pasture abandonment, while Sasa senanensis, native shrub species, regenerated from propagation that had spread from the surrounding forests. S. senanensis shrublands and P. pratensis/P. pratense grasslands established on deep soils while D. glomerata grasslands established on shallow soils. Trees rarely became established on abandoned pastures. The seed density in the seedbank, representing 19 species, ranged from 542 to 2957 seeds/m2. The dominant species in the vegetation (P. pratensis, Trifolium repens, and Rumex acetosella) were also common in the seedbank, whereas Cerastium holosteoides var. angustifolium, Chenopodium album var. centrorubrum, and Erigeron canadensis were widespread in the seedbank but did not occur in the extant vegetation. S. senanensis regenerated by vegetative propagation, and P. pratensis and P. pratense developed a seedbank. We concluded that for native species, particularly S. senanensis, vegetative reproduction has an important role on revegetation rather than regeneration from the seedbank, and the dwarf bamboo may be a keystone species in the ecosystems.