Abstract
Zoysia japonica Steud. is a dominant species in native pastures in Japan that is persistent even without fertilizer application. The purpose of this study was to determine the growth and increase of grazed Z. japonica plants under a deciduous forest at three tree densities (thin:30 trees/10 a, medium:44 trees/10 a and dense:63 trees/10a). Z.japonica sods were transplanted in March 1996. The rooting ratios of Z.japonica sods were 75, 86 and 98% under thin, medium and dense tree densities, respectively. The highest rooting ratio recorded under the dense plot was attributable to the higher soil water content that was maintained under the dense canopy. Frequency of occurrence and ground coverage of Z.japonica increased in all the plots in second and third year after transplanting. The most rapid increase in growth and highest dry weight of Z.japonica was recorded in the thin plot with 75% frequency, 60% coverage and 573g/m^2 dry weight in October of the third year. Estimated leaf area index (ELAI) of the trees increased gradually from the first year to the third year in all plots. The highest ELAI value was recorded in the dense plot throughout the experiment. Amount of tree litter decreased from year to year in all plots, and a little difference was recognized among treatments. Therefore, the rooting of transplanted Z.japonica under the tree canopies did not seem to be inhibited by shading within the range of thinning intensity examined, although the growth of Z.japonica (both in frequency and coverage) was higher under low density of 30 trees/10 a with 9 meter high.
