Effectiveness of turf and topsoil translocation for restoring long-term overgrazed understory herbaceous vegetation in coniferous/broadleaf deciduous mixed forest in Shikoku, Japan

Vegetation over-foraged by deer shows limited recovery potential for some species, even when exclosures are constructed. Turf and topsoil translocation might aid in restoring this vegetation. We evaluated the effectiveness of turf and topsoil translocation in restoring the overgrazed understory herbaceous vegetation in Saorigahara, covered by coniferous/broadleaf deciduous mixed forest in Shikoku, Japan. The herbaceous vegetation there has been degraded by overgrazing, but it has recovered in an exclosure constructed in 2008 (E2008). In November 2021 and March 2022, turf and topsoil of herbaceous communities within the E2008 were translocated to exclosures constructed in 2021. We monitored the recovery of the herbaceous communities, evaluating the impacts of the light environment, the translocation season, and the presence of water puddles, while also comparing the effectiveness of turf and topsoil translocations. We selected 22 herbaceous species, which have been identified within E2008 during 2008–2018, as the restoration target species. Translocated plots exhibited higher restoration in terms of the number of species, coverage, and maximum plant height of the restoration target species compared to the plots where translocations were not implemented. Nine restoration target species did not recover in any of the plots. The restoration target species showed better recovery in plots translocated in November 2021 and in turf translocated plots. This study indicates that turf translocation is more effective in restoring overgrazed understory herbaceous vegetation than merely constructing exclosures.