THE REGENERATION OF PIONEER TREE SPECIES UNDER BROWSING PRESSURE OF SIKA-DEER IN AN EVERGREEN OAK FOREST

The effects of Sika deer (Cervus nippon) browsing on the regeneration of pioneer species were studied in relation to canopy gaps in a warm temperate evergreen oak forest in Kasugayama, Nara City. Four study sites, three in canopy gaps and one under a closed canopy, were selected and each divided into fenced and unfenced plots. Under the dosed canopy, seedlings of all the pioneer species died irrespective of browsing pressure. However, in the canopy gap sites, seedlings of the pioneer species could establish and grow well. The seedling survival ratio in the fenced plots in the canopy gaps was > 60% 1 year after germination. However, in the unfenced plots, only < 20% of the seedlings survived 1 year, with all dying within 3 years after germination. Thus, the regeneration of pioneer trees in this forest was strongly inhibited by deer browsing. Successful regeneration of a pioneer, Zanthoxylum ailanthoides, occurred for several years even after two major wind disturbances during the past 90 years. This may be due to less browsing pressure from the deer.