Changes in vegetation coverage, species richness, and species composition inside and outside of deer-proof enclosures designed to protect endangered plants on Yakushima Island: Effects of fence protection and the light environment

Abstract

To determine whether the decline in forest understory vegetation on Yakushima Island, Japan is due only to the increase in deer or whether it is also affected by changes in the light environment, we compared changes in vegetation coverage and plant species richness between 2006 and 2016 inside and outside of four deer-proof enclosures on eastern Yakushima Island, in which canopy openness varied from 1.4% to 8.2%. The effects of environmental factors were tested using a generalized linear mixed model. Vegetation coverage was higher inside the enclosures, irrespective of the light environment. Species richness (for vegetation with coverage of at least 1%) increased inside enclosures, although this differed by species. Further research examining other sites is needed, with explicit consideration of the ecological traits of various species.