Changes in the understory vegetation of a Japanese red pine forest, including the grass-growing area and grazed by beef cattle, were studied. The forest was grazed from mid- May to mid-October. The average grazing pressure was 130 animal unit days/ha/year. Measurements were recorded in late July each year for 9 years. In the grass-growing area produced by the withering of red pines and grazing, sweet vernal grass (Anthoxanthum odoratum L.) was dominant. Under the continued grazing, sweet vernal grass gradually decreased while Japanese lawn grass (Zoysia japonica Steud.) increased. However, further increase in Japanese lawn grass was prevented by the growth of red pine seedlings. In the shrub-dominated area, cattle grazed the shrub leaves well. The vegetation cover of the area decreased rapidly and sweet vernal grass began to appear continuously. These findings indicated that if red pine trees are thinned and grazing of understory vegetation is continued, Japanese red pine forests will change to the Zoysia-type grassland mixed with red pines. In this case, some newly growing red pine seedlings should be removed because cattle do not graze on these seedlings, which will then rapidly grow and suppress the growth of Japanese lawn grass.

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The perennial C_4 grass Erianthus arundinaceus is a novel energy crop because of its high yield potential and good tolerance of environmental stresses. We conducted a field experiment in Nasushiobara City (36°55'N, 139°56'E) in Japan over a 2-year period to determine the dry weight of three plant parts (harvestable shoots at heights above 30cm from the ground, basal shoots below 30cm, and roots), and the corresponding concentrations of minerals and nonstructural carbohydrates during winter. Mineral concentrations in the harvestable shoot decreased during winter, possibly due to translocation to the basal parts. Nitrogen contents in the basal shoot plus root increased by about 20% during winter. Starch content, which was highest in the roots at each sampling time, increased during winter, indicating that roots were the major storage organ. The nitrogen and potassium removals from the field by harvesting in October of the second year were about 2.4 times the amounts supplied in chemical fertilizer. Biomass yield in the March-harvest of the second year decreased by 25%, compared with that in the October-harvest due to shattering of winter-withered leaves, but nitrogen and potassium removals in the March-harvest decreased to about 55% of those in the October-harvest.

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We conducted a field experiment in Nasushiobara City (36°55'N,139°56'E) in Japan to determine the effects of cutting time and height on regrowth after overwintering in three lines of Erianthus arundinaceus with different plant type. The plants were cut at 5 or 30 cm above the ground in November 2010 or February 2011. Plant regrowth, defined using by number of tillers and dry matter yield, was affected more by the cutting time than by the cutting height. The number of regrown tillers in May 2011 and the yield in October 2011 were larger in the February-cutting than in the November-cutting of the previous year. The higher cutting produced more tillers in May 2011 and a larger yield in October 2011 in the November-cutting, whereas the opposite results were obtained in the February-cutting. The effect of cutting time and height was apparent in the lines of tiller-weight type. Highly positive correlation coefficients were obtained between the number of regrown tillers in May 2011 and the dry matter yield in October 2011 for the three lines. These results suggest that poor regrowth in the November-cutting might be caused by a reduction of tiller bud potential in the overwintered stubble.

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