Features of planted cypress trees vulnerable to damage by Japanese black bears Akimi Yamada1,3 and Masahiro Fujioka2,4 1Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8072, Japan 2Agricultural and Forestry Research Center, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8077, Japan Abstract: The Japanese black bear (Ursus thibetanus japonicus) causes serious and persistent damage to conifer plantations in some areas of Japan. From 2006–08, we examined bear damage and tree characteristics (diameter at breast height [DBH], width of growth rings, and amount and nutritional content of newly-developing vascular tissues) in 7 even-aged stands of Japanese cypress (Chamaecyparis obtusa) growing at similar elevations in a university forest. Larger-diameter trees were more likely than smaller trees to be damaged by bears in each stand. The major nutritional component of vascular tissues was sugar, mainly sucrose. Sugar concentration of vascular tissues showed little variation, and was correlated with neither DBH nor stand age. Mass of vascular tissues was highly variable and was positively correlated with DBH, but not with stand age. To reduce bear damage, foresters should concentrate direct protection efforts on larger-diameter trees. Key words: Asiatic black bear, Chamaecyparis obtusa, conifer damage, Japan, Japanese cypress, nutrition, sugar, Ursus thibetanus japonicus, vascular tissue Ursus 21(1):72–80 (2010) The Japanese black bear (Ursus thibetanus japoni- Black bears are often regarded as a nuisance in cus), a subspecies of the Asiatic black bear (Wozencraft Japan. They damage agricultural crops (Deguchi et 2005), occurs on 3 of the 4 main islands of Japan: al. 2003), commercial timber (Watanabe 1980, Honshu, Shikoku, and Kyushu (Ministry of the Toyoshima and Narita 1982, Yamane et al. 1988, Environment, Japan 2004). Its distribution within Yamazaki 2003), and apiaries. Bears also threaten these islands coincides well with that of deciduous and injure people occasionally (Hayashi 1984, Japan broad-leaved forests consisting of beech (Fagus cre- Wildlife Research Center 2005). A large number of nata) and Japanese oak (Quercus crispula), which black bears are captured and killed annually. During provide beechnuts and acorns in autumn (Hashimoto 1946–2004, annual mortality was approximately 500 and Takatsuki 1997). The Asiatic black bear is listed as bears killed by hunting with guns and 1,000–2,000 vulnerable in the IUCN (International Union for bears killed by pest control, mostly using barrel Conservation of Nature) Red List (2008). National (culvert) traps (Oi and Yamazaki 2006). Such killing, surveys show that the Japanese subspecies has however, did not necessarily result in reduced expanded its range from 1978 to 2003 (Oi and damage (Huygens et al. 2004). Yamazaki 2006). However, 6 isolated local popula- In timber stands, Japanese black bears remove the tions are listed in the Japanese Red List. The Kyushu bark of conifers to eat the underlying, newly- population is believed to be extinct, and the Shikoku developing vascular tissues (containing photo- population is estimated at much less than 100 synthate), in the same manner as American black individuals (Ministry of the Environment, Japan 2002). bears (Ursus americanus) do in the Pacific Northwest of the United States (Lutz 1951, Barnes and Enge- 3 man 1995, Ziegltrum and Nolte 2001). Because black Present address: International Forestry Cooperation bears remove bark from older trees, they cause more Office, Planning Division, Private Forest Department, Forestry Agency, 1-2-1 Kasumigaseki, Chiyoda-ku, Tokyo serious economic damage to forests than other large 100-8952, Japan mammals such as the Japanese serow (Capricornis [email protected] crispus), which damage younger trees or saplings 72 TREES VULNERABLE TO BEAR DAMAGE N Yamada and Fujioka 73 (Watanabe 1980). A single bear may peel the bark vascular tissues or their nutritional contents was off up to 10 trees in a feeding bout (Watanabe 1980), correlated to tree diameter at breast height (DBH) or as many as 50–70 trees a day in North America and hence to bear damage. We only measured bear (Schmidt and Gourley 1992). Complete girdling by damage to Japanese cypress trees (Chamaecyparis peeling is lethal to the trees. Partial girdling reduces obtusa) in plantations at similar elevations within a the growth rate and leads to further damage by university forest, where Japanese cypress is more insects and fungal infestations (Hennon et al. 1990, frequently damaged than other planted conifers, Yamada et al. 1992). In their search for food, black Japanese cedar (Cryptomeria japonica) and Japanese bears peel the bark of conifers to obtain high caloric larch (Larix kaempferi) (Kadowaki et al. 1997). sugars such as fructose, glucose, and sucrose that occur in newly-developing vascular tissues (Radwan 1969, Nishi et al. 2003). It has been shown that food Study area preferences of American black bears are related to This study took place in the Ikawa University both chemical constituents (simple sugars, terpenes) Forest, University of Tsukuba, in northern Shizuoka, and mass of vascular tissues (Kimball et al. 1998a). on the island of Honshu, Japan (35u209230N, Bark stripping and feeding by bears generally begins 138u139300E, Fig. 1). The 1,760 ha forest occupies the in late spring (May), when natural food resources are upstream half of the catchment area of the Higashi- scarce, and declines in late summer (August), when gouchi River, a tributary of the Ohi River. The fruits such as acorns and berries become available in topography is characterized by steep slopes of 38–40u Japan (Watanabe 1980, Kadowaki et al. 1997), a few on average with many landslides. The elevation ranges weeks later than in US (Witmer et al. 2000). Damage from 950 to 2,406 m. Average yearly temperature was is concentrated in stands with lower tree densities 9.0uC and precipitation averaged 280 cm during 1993– (Stewart et al. 1999). Bears typically select vigorous 2002. Most forest stands were clear-cut in the 1960s, trees in productive stands (Noble and Meslow 1998). before and around the time the University Forest was Furthermore, the intensity of bear damage can be established. About 1,355 ha (77%)oftheforestare influenced through silvicultural methods. For exam- secondary forests that naturally regenerated after ple, damage to trees increases after stand improve- clear-cutting. The secondary forests were dominated ments such as thinning and fertilization (Mason and by Japanese oak, Japanese wing nut (Pterocarya Adams 1989, Kimball et al. 1998b) and decreases rhoifolia), Japanese bird cherry (Prunus grayana), after pruning (Kimball et al. 1998c). Japanese maple (Acer palmatum), Japanese fir (Abies In the US, supplemental feeding during spring firma), and Japanese hemlock (Tsuga sieboldii). Stands provides bears with an alternative food resource totaling 300 ha in all were conifer plantations, when natural foods for bears are still scarce. This has consisting of Japanese cypress (or hinoki cypress), been shown to reduce bear damage in timber stands Japanese cedar, and Japanese larch. Conifer seedlings (Ziegltrum and Nolte 1997, Witmer et al. 2000, were planted during 1965 to 1981, typically at a density Ziegltrum 2004). Few damage control techniques are of 3,000 stems/ha. Bear damage to planted conifer trees employed in Japan, partly because most Japanese has been recognized in this area since 1981 and now foresters manage small forests compared to US affects most conifer stands (Kadowaki et al. 1997). foresters. Therefore, it is more difficult for foresters in Japan to invest in large-scale techniques. Yagami (2007) has recently recommended wrapping trees Methods with biodegradable nets or tapes. Although this We measured DBH and inspected bear damage in method can reduce bear damage, it is labor intensive 3 even-aged stands of age 27 to 39 years in August and the materials are very expensive. It would 2008 to determine if bears prefer trees of certain therefore be of great help to Japanese foresters if diameter classes (Table 1). In this paper, stand or they were able to select trees to be wrapped based on tree age refers to years after planting of seedlings scientific and practical standards. The objective of that are usually 3 years old. All planted trees within 5 this study was to determine features of trees in belt transects of 30 m length and 4 m width were commercial timber stands that are vulnerable to assessed in each stand. We did not count dead trees. black bear damage. We were especially interested in To evaluate the nutritional value of bark-stripping determining if either amount of newly-developing behavior for bears, we collected newly-developing Ursus 21(1):72–80 (2010) 74 TREES VULNERABLE TO BEAR DAMAGE N Yamada and Fujioka Fig. 1. Stands (black circles; see Table 1) in the Tsukuba University Forest at Ikawa in Shizuoka Prefecture, Japan for a 2006–08 study of Asiatic black bear damage to Japanese cypress. The broken lines and shaded areas represent streams and conifer plantations, respectively. vascular tissues from live Japanese cypress trees in 7 with vines. After measuring the DBH of a sample stands aged 15 to 41 years in the peak season of bear tree, we removed its bark using hatchets from a damage, June of 2006 and 2007 (Table 1). In 2006 we patch 40 cm long by 10 cm wide at 1 m above the selected 5 pairs composed of a large-diameter tree ground and collected newly-developing vascular and the smallest tree within 5 m from that tree in tissues by using plastic spatulas according to Nishi each of 6 stands, producing a data set from 60 trees. et al. (2003). We scrubbed the surface of the peeled We did not sample trees damaged by bears. In 2007 patch only once in 2006, but did so repeatedly for we selected a total of 92 trees, including damaged 5 minutes in 2007 to collect all available newly- trees, within belt transects of 20 m length and 3.6 m developing vascular tissues and sap.