抄録
Large herbivores can affect the regeneration and succession of vegetation through selective leader browsing, bark stripping, antler rubbing, and thus are often the key species in ecosystems. For over a decade, the density of the Formosan sambar (Rusa unicolor swinhoii) has rapidly increased, as well as its possible influence on subalpine forests. The damage frequency and mortality rate of forest trees due to bark stripping and antler rubbing by sambar were surveyed in the southern area of the Yushan National Park in Taiwan. Formosan sambars have strong selectivities regarding the tree species and DBH ranks for bark stripping and antler rubbing. Sambar stripped the bark of the saplings (DBH ＜ 20cm) of Taiwan fir (Abies kawakamii), Taiwan hemlock, and Taiwan Armand pine (Pinus armandii var. masteriana) more frequently than expected ( X2 =81.2, 90.4, 17.1, respectively, p ＜ 0.001). They selected the saplings f TAiwan fir and Taiwan Armand pine for antler rubbing more frequently than expected (p ＜ 0.001 and p = 0.016, respectively). Of the dominating canopy species preferred by sambar (Taiwan hemlock and Taiwan fir), the damage frequency of saplings smaller than 15 cm was greater than expected. Generally, the bark stripping and antler rubbing of sambars resulted in significantly higher mortality raes for saplings of Taiwan fir and Taiwan hemlock. Ont eh contrary, very few saplings of Taiwan red pine were damaged by antler rubs. Our results suggest that Formosan sambar at high population densities have a profound impact on the survival of the Taiwan fir and Taiwan hemlock saplings in subtropical, subalpine areas. The massive death of saplings with DBH under 15 cm is detrimental to the renewal of these two dominating, late-successional canopy species, diverging the DBH structure of these two species from their natural DBH distributions. They also kill many Taiwan hemlocks and Taiwan firs within red pine forests. The behavior of selective bark-stripping by sambar might enhance the competitive advantage of Taiwan red pine.
