Changes in species composition and density on soil seed bank after a wildfire at a Cryptomeria japonica forest in Kamaishi, northeast Japan.

Abstract

The species composition and density of soil seed banks were investigated at burned and unburned Cryptomeria japonica forest. The majority of seeds in the seed bank at the unburned site were C. japonica. The number of species and density of seed bank in the first autumn after the fire were smaller than at the unburned site. The soil seed bank in the first year was characterized by numerous seeds of Commelina communis and no seeds of C. japonica. It is suggested that the dormancy of buried seeds of C. communis was broken by fire stimulation, and mature plants produced many seeds. Disappearance of C. japonica seeds in the soil seemed to be caused by short seed longevity, and lack of newly dispersed seeds from mother trees due to above-ground vegetation burning. The soil seed bank tended to recover from fire impact in the second year after the fire. The number of species on the seed bank in the second year was larger than the first year. Density of C. communis seeds, which increased just after the fire, decreased in the second year. In contrast, the seeds of C. japonica, Alunus hirsuta and so on, which disappeared after the fire, reappeared. In the second year, the seed bank consisted of both seeds produced by regenerated plants after the fire and seeds dispersed from the neighboring undisturbed area.