Plant indicator species for the conservation of priority forest in an insular forestry area, Yambaru, Okinawa Island

Abstract

Degradation of old-growth forests is an important issue for global biodiversity conservation. Robust indicator species greatly facilitate the identification of old-growth forests requiring protection. Understanding why particular species are associated with priority forests is necessary for assessing the reliability of indicator species. Here, we surveyed the vegetation of 69 sites in Yambaru forests (Okinawa Island) varying in forest age and analyzed the relationships between the dominance of vascular species and three criterion parameters (forest age and species richness (SR) of epiphytes and endangered plants). Eleven species showing significant positive correlations with three parameters were designated as potential candidate indicator species, ten of which were woody species. Of the above eleven candidate indicator species, Distylium racemosum was considered one of the most useful indicator species because it can be easily identified in the field and its ecological characteristics are well documented. Regarding three woody traits -sprouting ability, annual growth rate and wood density -which are expected as the cause of indexing, endangered SR increased when tree species with low sprouting ability and high wood density were dominant, and epiphyte SR increased when tree species with low annual growth rate and high wood density were dominant. These woody species traits were associated with forest age and could explain why D. racemosum is an indicator of priority forest. These results suggest that large trees with such woody characteristics are effective indicators of priority forests.

Ecological management of insular forests: conservation of endangered species and native ecosystems in Ryukyu Archipelago

“…The next paper focuses the old-growth forests in Yambaru, northern Okinawa Island. Abe et al (2021) searched indicator vascular species for biodiversity conservation in Yambaru forests (Okinawa Island) and found that several plant species including Distylium racemosum, a native dominant tree species, are good indicators of priority forests to be protected. Because of their commonness and easy-to-identify looks, they would be helpful to find and conserve forest habitats for many endangered species.…”

Catchment-based sampling of river eDNA integrates terrestrial and aquatic biodiversity of alpine landscapes

“…Yet, plant composition can be very informative for evaluating the ecological quality of a site (Spyreas 2019 ). Plant inventories play an important role in evaluating ecosystem functionality and recovery (Abe et al 2021 ; Bachand et al 2014 ), such as food resources for species at higher trophic levels (Felton et al 2010 ). To better evaluate ecosystem health, plant assemblages must be sampled, and not just the animals depending on them.…”

Resilience of native ant community against invasion of exotic ants after anthropogenic disturbances of forest habitats

“…Yanbaru is of considerable interest in the study of community resilience. Although there are extensive forests with large areas of wilderness, most of these have been subjected to logging or other artificial modifications in the past (Abe et al, 2021). A large number of spectacular endemic animals, such as the Okinawa Rail ( Gallirallus okinawae ) and Okinawa Woodpecker ( Dendrocopos noguchii ) still inhabit the area, with no faunal species extinctions reported to date.…”