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.

Is deer herbivory directly proportional to deer population density? Comparison of deer feeding frequencies among six forests with different deer density

“…This reach is lower than the reaches of other C. nippon subspecies (C. n. centralis: 185 cm, C. n. yesoensis: about 220 cm) (Furubayashi, 1995;Miyaki and Kaji, 2004). This difference may be due to the fact that C. n. yakushimae has the smallest body size (Takatsuki, 2006), and these data suggest that the surveyed saplings (30-130 cm in height) can be browsed by deer.…”

Pits Conserve Species Diversity in an Overgrazed Grassland

“…Volcanic upheaval formed this island 40,000-50,000 BP. On this island, three major vegetation types are recognized: deciduous forest represented by Acer mono and Tilia japonica, needle-leaved plantation, and grassland [15]. The snow period is from December to April and the maximum snow depth is ca 50 cm on February in usual years.…”

“…Particularly, deer are over-populated on the world-natural heritages assigned by UNESCO in Japan, and modify the ecosystems [30]. Overgrazing by deer has been conspicuous for a few decades in a grassland on Nakajima (or Nakanoshima) Island, Hokkaido, northern Japan, because grassland often shows higher productivity than forest under story [15]. Palatable plants decline greatly in the grassland on Nakajima Island after the explosion of deer density, and then deer tend to eat whatever food is available when food availability is low, e.g., in winter [24].…”

Fecal nitrogen as an index of dietary nitrogen in two sika deerCervus nippon populations

“…The vegetation is divided into three types; deciduous broad-leaved forest (91.8%) dominated by Acer mono and Tilia japonica, coniferous plantation (6.3%), and grassland (1.6%). The rest of the island (0.3%) is inaccessible to deer (Miyaki and Kaji 2004).…”

“…After the population crash, the deer lost about 20% of their body mass and showed delayed age at primiparity (Kaji 2001). Because food availability is low at this site, deer forage on fallen deciduous foliage Kaji 2001, Miyaki andKaji 2004).…”