Abstract
In order to determine the present state and potential conservation strategies of the endangered Pteridophyta, Polystichum neolobatum Nakai, we investigated whole individuals, leaf size and habitat for the species. P. neolobatum was found in only two of the four sites it had previously been observed in. Only 21 individuals were found in 2004, 18 individuals in 2006, and 15 individuals in 2007. There were two mature individuals with spores found on three different occasions. Eleven individuals were found in places where sika deer could enter (ET) and seven in places where there were no sika deer (NS). There was no difference in the average leaf number per individual between ET and NS sites, but leaf size was smaller at ET sites, as compared to NS. Furthermore, individuals at ET sites more frequently lacked the tip of their leaves, which sika deer may have ingested. There was less vegetation cover and a lower frequency of Sasamorpha borealis at ET than at NS sites. These findings suggest that P. neolobatum may be facing extinction in the Tanzawa Mountains. To conserve P. neolobatum, deer-proof fences must be established to prevent sika deer from browsing on forest floor vegetation, and propagation technology must be developed as an emergency measure.
