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

Abstract

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.