Summer forage biomass and the importance of litterfall for a high-density sika deer population

The biomass of summer forage and their contributions were surveyed to show that litterfall supported a high-density population of sika deer (Cervus nippon Temminck) in summer on Nakanoshima Island, Toya Lake, Japan. In July 1974, the grassland had the highest productivity among understory vegetations (228 +/- 55 kg ha(-1): mean +/- SE). In deciduous forests, palatable plants occupied only 0.1% of the biomass of 0.872 +/- 0.366 kg ha(-1), and deciduous leaves within the reach of deer (=220 cm at height) produced 0.208 +/- 0.070 kg ha(-1). However, litterfall during this period had the highest productivity, 28.7 +/- 5.3 kg ha(-1). The deer consumed litterfall (75.6% in dry weight), short grasses (17.2%), deciduous forest understory (4.1%), deciduous leaves within the reach of deer (3.0%) and conifer plantation under story (0.1%). It is suggested that the high-density deer population would be maintained by litterfall through the year instead of browsing in deciduous forests, which has been overlooked.