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Natural forest recovery on abandoned farmland is hindered by a variety of factors and active restoration plays an important role when quick afforestation is desired. We investigated seedling survival of four transplanted native tree species (Quercus myrsinifolia, Quercus serrata, Aphananthe aspera, and Rhus sylvestris) by experimentally manipulating the vegetation cover, which was mainly dominated by dwarf bamboo (Pleioblastus chino), and herbivore access to the planting sites on farmland that had been abandoned for 15 years at the start of the study. Few transplanted seedlings of any species survived under intact vegetation cover, irrespective of herbivore presence. In gaps in the vegetation cover, winter browsing by Japanese hare (Lepus brachyurus) damaged all species. However, lower browsing frequency and higher resprouting ability after grazing of the seedlings enabled both Quercus species to survive better than the other species. These results indicate that dwarf bamboo and the hare jointly limit the establishment of native trees in old fields. If active afforestation by transplanting seedlings at sites dominated by dwarf bamboo is planned, a combination of vegetation removal, selection of suitable species, and temporary seedling protection will be most effective.

Restoring natural forests after field abandonment is a land management objective that fosters the recovery of forest biodiversity. We performed seeding and transplanting of native tree species 40 years after the abandonment of an arable field that became dominated by a dwarf bamboo (Pleioblastus chino (Franch. et Sav.) Makino) and by kudzu (Pueraria lobata (Willd.) Ohwi). By permutation tests, the removal of competing vegetation (gap creation) significantly increased the survival of three seeded species of Fagaceae and of eight transplanted species. In contrast, intact vegetation prevented most individuals of all species from surviving for 1 year after planting. The lack of natural recruitment of Fagaceae in the nonseeded subplots indicated that seed limitation was a cause of the slow afforestation. Although litter accumulation in gaps at the time of seeding slightly increased survival for late-germinating Quercus myrsinifolia Blume and Castanopsis sieboldii (Makino) Hatus. ex T. Yamaz. et Mashiba, the effect was not consistent among plots and was not statistically significant. Our results suggest that for successful afforestation using native trees in abandoned fields, it will be necessary to remove competitive native species to avoid severe limitations on microsite availability and that simultaneous tree establishment by seeding or transplanting should be implemented to accelerate the establishment of native tree species.

Field abandonment has increased over several decades under a long-term recession in Japanese agriculture. To support effective farmland management or reforestation, the patterns of tree recruitment in abandoned fields, which influence management costs, need to be clarified. We investigated tree seedling establishment and microsite variables along forest–field transects in 11 abandoned fields adjacent to secondary broad-leaved forests in the eastern Kanto region of Japan. Generalized linear mixed model analysis indicated that tree seedling establishment in abandoned fields was not correlated with the period of abandonment. Instead, it was positively correlated with vegetation openness. The dominance of a woody vine (Pueraria lobata), an annual liana (Humulus japonicus), and a dwarf bamboo (Pleioblastus chino) mainly explained low vegetation openness within the fields. In addition, the establishment of evergreen tree seedlings and tree seedlings dispersed by hoarding was negatively correlated with the distance from the forest edge. In the forest interior, taller understory vegetation at the edge correlated with lower seedling establishment. These results suggest that seedling establishment across forest–field ecotones is restricted by the dominance of competitive natives within abandoned fields and distance-dependent limitations in both abandoned fields and adjacent forest.