Abstract
We investigated the effect of protection fence against deer grazing on the restoration of Sasa nipponica biomass and nitrogen cycle in deciduous broad-leaved secondary forest. Plots covered with Sasa over 50% (Large) and plots covered less 30% (Small) were conducted in both inside and outside the fence. Sasa biomass and litterfall were measured, and also amounts of inorganic nitrogen movement in the seepage soil solution were determined by ion exchangeable resin in each plot. Two years after setting the fence, Sasa biomass increased to around 4,000 kg ha-1 and the amount of leaves nitrogen was 40 kg ha-1 in large plots of the inside. And then the amount of leaf litterfall nitrogen increased, and the nitrogen mineralization enhanced in the surface soil, and also inorganic nitrogen absorbed by Sasa rhizome from soil seepage solution increased. In the large plots of outside the fence, Sasa biomass also increased to around 2,000 kg ha-1 2 years after setting the fence. In contrast, in the small plots, Sasa biomass and litterfall were not remarkably changed 2 years after setting the fence. Sasa rhizome biomass was much smaller in the small plots than in the large plots. Therefore, if we expect rapid restoration of Sasa biomass, the protection against deer grazing is necessary before Sasa rhizome biomass declines.
