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Features of planted cypress vulnerable to damage by Japanese black

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 ( thibetanus japonicus) causes serious and persistent damage to plantations in some areas of Japan. From 2006–08, we examined bear damage and 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 . 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 consisting of beech (Fagus cre- Wildlife Research Center 2005). A large number of nata) and Japanese (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 of 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 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 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 (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 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 (Abies In the US, supplemental feeding during spring firma), and Japanese hemlock (). 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

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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. Collected width at 3 locations in each of 3 stands. In both years samples were sealed in plastic bags and brought to we ignored trees in which the crown was covered the laboratory. Because digestive efficiency by black

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Table 1. Characteristics of stands of Japanese cypress plantations in the Ikawa University Forest, Japan, 2008. Year of Stand code Studied itemsa measurement Year plantedb Area (ha)b Slopec Aspectc Elevation (m)c 03I1 V 2006 1965 2.8 40 SE 1350 02C2 V 2006 1966 12.0 43 E 1290 13R3 V/G/D 2006–08 1969 2.9 36 WSW 1320 10C1 V/G/D 2007–08 1974 9.1 36 WSW 1240 10T1 V 2006 1975 1.3 26 SW 1180 13R5 V/G/D 2006–08 1981 2.1 42 W 1350 05N1 V 2006 1991 0.4 34 S 1250 aV: vasculartissues collected forsugaranalysis; G: growthringsamples c ollected; D: DBH measured and bear damage examined. bFrom Ikawa University Forest records. cCalculated (ArcView, Version 9.1) based on 1-m grid elevation data; aspect is the most frequent slope aspect of the stand; steepness (degrees) and elevation are the average values for the stand. bears is inversely proportional to the fiber contents per. We measured the width of growth rings of the 3 of the diet (Pritchard and Robbins 1990), we most recent years (2005–07) to the nearest 0.01 mm excluded fibers from the samples in 2007 by straining with a digital vernier caliper along 3 lines perpendi- them through gauzes before taking measurements. cular to the tangential line to the growth-ring arc, On the sampling day, each sample was weighed to using a stereomicroscope when necessary. the nearest 0.1 g on a digital scale, stirred, and sugar We employed generalized linear models (GLMs) concentration estimated by a digital refractometer for the data set from 2006 to determine if DBH and (PR-101a, Atago Corporation, Tokyo, Japan) de- stand ages had significant influence on the quality signed to estimate the total concentration of all and quantity (sugar concentration and mass) of soluble solids in the sample as the Brix scale (%). Japanese cypress vascular tissues. Generalized linear Because the refractometer identified neither non- mixed models (GLMMs) were applied to data from sugar nutrients nor types of sugar, we outsourced 2007 because we sampled only 3 even-aged stands, detailed nutritional analysis to the Japan Food which were set as a random effect (i.e., regarded as Research Laboratory Foundation. For this analysis, sampling blocks). We assumed normal distributions we collected vascular tissues from 3 trees in a 33- for independent variables of all the GLMs and year-old stand (10C1). We brought the tissue GLMMs. We used logistic regression to calculate the samples immediately to the laboratory, froze them, probability of bear damage from DBH, sugar and sent them to the Foundation. The 3 samples concentration, or vascular tissue mass. To quantify were mixed before the analysis. Water was deter- relationships between width of growth rings and mined by the reduced pressure treatment, protein either sugar concentration of vascular tissues, their was identified by the Kjeldahl method, fat was mass, or tree DBH, we calculated Pearson correla- measured by the acid resolution method, and ash by tion coefficients (r). All statistical analyses were done the direct ashing method. Carbohydrate was esti- using R statistical package (R Development Core mated by subtraction (the percent remaining from Team 2008). the sum of water, protein, fat, and ash). Sugars were quantified by high performance liquid chromato- graph (HPLC). The amount and quality of vascular tissues are Results expected to reflect the current vigorousness of a tree, The percent of damaged trees in 3 stands where we but its DBH is an accumulated result of growth for inspected bear damage and measured DBH in 2008 several years. Thus, in 2008 we collected a small was 48.7% (76 of 156 trees) in stand 13R3, 47.2% (67 piece of recent growth rings from trees from which of 142 trees) in stand 10C1, and 41.5% (59 of 142 vascular tissues were collected the year before. trees) in stand 13R5. Mean DBH of damaged trees Growth-ring samples were cut from tree trunks with was significantly larger than that of undamaged a saw to a depth of about 3 cm at 1 m above ground. trees: 21.9 cm versus 16.5 cm in stand 13R3 (Welch’s Samples were air dried at room temperature for t-test, t 528.59, 147.6 df, P , 0.001, n 5 156), about 1 month before being polished with sandpa- 19.5 cm versus 13.3 cm in stand 10C1 (t 528.49,

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Table 2. Statistical analyses of the relationship between mass (g) and sugar concentration (%) of developing vascular tissues, stand age (years), diameter at breast height (DBH, cm), growth-ring width (mm), and bear damage of Japanese cypress trees in the Ikawa University Forest, Japan. Dependent Independent Year (sample size) variable variable Statisticsa P 2006 (59) Age Mass GLM coefficient 520.037 (0.024 SE) 0.137 DBH Mass GLM coefficient 5 0.190 (0.037 SE) ,0.001 Age SugarGLM coefficient 520.003 (0.008 SE) 0.760 DBH SugarGLM coefficient 5 0.002 (0.013 SE) 0.857 2007 (92) Sugar Damage Logistic regression coefficient 5 2.411 (0.685 SE) ,0.001 Damage Mass Welch t 523.872, 52.6 df ,0.001 DBH Mass GLMM coefficient 5 0.639 (0.073 SE) ,0.001 2007 (89) Growth DBH Pearson correlation r 5 0.726, t 5 5.284 ,0.001 Growth Mass Pearson correlation r 5 0.746, t 5 10.451 ,0.001 2007 (81) Damage SugarWelch t 525.111, 65.0 df ,0.001 Growth Sugar Pearson correlation r 5 0.322, t 5 3.028 ,0.001 DBH SugarGLMM coefficient 5 0.034 (0.028 SE) 0.232 Mass Damage Logistic regression coefficient 5 0.213 (0.072 SE) ,0.01 2008 (440) DBH Damage Logistic regression coefficient 5 0.307 (0.031 SE) ,0.001 Damage DBH Welch t 5214.559, 437.3 df ,0.001 aGLM 5 generalized linear models; GLMM 5 generalized linear mixed models.

139.2 df, P , 0.001, n 5 142), and 24.5 cm versus probability of bear damage (Table 2). Mass of 15.8 cm in stand 13R5 (t 5210.33, 132.6 df, P , vascular tissues was much more variable than sugar 0.001, n 5 142). All combined, mean DBH of concentration; coefficients of variation were 7 to 10 damaged trees was 21.9 cm (SD 5 4.4, n 5 202) and times larger for the vascular tissue mass (0.42 in 2006 that of undamaged trees was 15.3 cm (SD 5 5.0, n 5 and 0.59 in 2007) than for the Brix value (0.06 in 238), the difference being significant (Table 2). 2006 and 2007). Larger-DBH trees were more likely to be damaged GLM revealed that sugar concentration was (Fig. 2). Logistic regression showed that DBH correlated neither with the stand age nor with tree significantly affected the probability of bear damage DBH in 2006, and GLMM showed that DBH did (Table 2). not influence sugar concentration in 2007 (Table 2). The average vascular tissue mass was 113 g/m2 In contrast, DBH had great effects on vascular tissue (SD 5 47, n 5 60) for samples obtained in 2006 and mass both in 2006 and 2007 (Table 2). Stand age did 182 g/m2 (SD 5 108, n 5 92) for samples obtained in not influence vascular tissue mass in 2006. 2007 (sampling method differed; see Methods). The mean growth-ring width (2005–07) was Significantly more mass of vascular tissues was 1.5 mm (SD 5 0.8, n 5 89) in 3 stands. The mass collected from damaged trees (243 g/m2,SD5 78, of vascular tissues sampled in 2007 was positively n 5 23) than undamaged trees (161 g/m2,SD5 109, correlated with the width of growth rings (Table 2, n 5 69) in 2007 (Table 2). Similarly, logistic Fig. 3). Although the coefficient of correlation was regression showed that vascular tissue mass had a low, sugar concentration of vascular tissues was also positive effect on the probability of bear damage positively correlated with width of the growth rings (Table 2). The average Brix value, a relative index of (Table 2). The width of growth rings was positively sugar concentration as measured by the digital correlated with DBH measured in 2007 (Table 2, refractometer, was 9.1% (SD 5 0.5, n 5 59) in Fig. 4). 2006 and 9.2% (SD 5 0.5, n 5 81) in 2007. One Vascular tissues were mostly water (89.7%), sample in 2006 and 11 in 2007 contained insufficient followed by carbohydrate (8.7%; Table 3). Protein, material to be measured by the digital refractometer. fat and ash were less than 1% of the vascular tissues. Sugar concentration was significantly higher in Three kinds of sugars were detected by HPLC: damaged trees (9.6%,SD5 0.34 SD, n 5 23) than sucrose, fructose, and glucose. Total sugar content undamaged trees (9.1%,SD5 0.55, n 5 58) in 2007 was 5.16 g/100 g, with sucrose the most abundant (Table 2). Similarly, logistic regression showed that (Table 3). On a dry-mass basis, the vascular sample sugar concentration had a positive effect on the was 50.1% sugar.

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Fig. 3. Vascular tissue mass plotted against growth- ring width (2007) of Japanese cypress in 3 stands in the Tsukuba University Forest at Ikawa, Japan (n = 89).

Discussion Large diameter trees, which produce more vascular tissues, are more vulnerable to bear damage than smaller diameter trees within any given stand; we found that ratios of damaged to undamaged trees were positively correlated with DBH (Table 2, Fig. 2). Other studies suggest that vigorous or large diameter trees are more vulnerable to bear damage (Watanabe 1980, Noble and Meslow 1998, Yamazaki 2003). Kimball et

Fig. 2. Number of Japanese cypress trees damaged by Japanese black bears (black portion) and un- Fig. 4. Diameter at breast height (DBH) and growth- damaged (white portion) as a function of diameter at ring width (2007) of Japanese cypress in 3 stands breast height (DBH; cm) for 3 stands in the Tsukuba (10C1, 13R3, and 13R5) in the Tsukuba University University Forest at Ikawa, Japan, 2008. Forest at Ikawa, Japan (n = 89).

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Table 3. Nutritional composition of developing vascular tissues. These findings imply that vascular vascular tissues of Japanese cypress sampled from tissue mass is a more important factor than sugar 3 trees in a 34-year-old stand in the Ikawa University concentration when black bears choose trees for Forest, Japan, June 2007. bark-peeling, although bears may also be sensitive to Constituents Content (g/100 g) sugar concentration because it was found to be Water89.7 significantly correlated with damage (Table 2). Protein 0.8 Nutritional analysis indicated that the major non- Fat 0.3 Ash 0.5 water component of vascular tissues of Japanese Carbohydrate 8.7 cypress was sugar (Table 3), supporting Radwan Sucrose 4.37 (1969) for Douglas-fir ( menziesii), wes- Fructose 0.43 tern hemlock (), western red cedar Glucose 0.36 (), and red (Alnus rubra). Kimball et al. (1998a) reported that black bears preferred a high-carbohydrate diet to a low-carbohydrate diet. Several studies found that vascular tissues are an al. (1998b) showed that thinning and fertilization in excellent food resource with relatively high levels of timber stands increased vascular tissue mass and sugar sugar (Radwan 1969, Partridge et al. 2001). Sugar content. Mason and Adams (1989) reported that concentration of Japanese cypress was comparable to thinned timber stands were preferred by black bears. that of wild berries in our study area. For example, However, it is unknown how bears perceive abundance sugar concentrations of Momiji-Ichigo (Rubus palma- of vascular tissue mass of trees. Foraging preferences of tus var. coptophyllus, 8.2%) and wine berry (R. black bears may result from learning processes or may phoenicolasius, 8.7%) were lower than Japanese be mediated by flavor (Kimball et al. 1998a). cypress vascular tissues (about 9%), though other Sugar concentration of Japanese cypress vascular berries, such as strawberry-raspberry (R. illecebrosus, tissues showed relatively small variation compared 12.7%), were higher than Japanese cypress (measured with tree mass and was not much influenced by the by the authors using the same method). stand age or DBH (Table 2). This result supports The difference in values of sugar concentration those of Radwan (1969), who reported that newly- between HPLC and digital refractometer was pre- formed vascular tissues from 20- to 30-year-old trees sumably caused by the difference in the method. The had little variation in sugar content. Kimball et al. digital refractometer measures total concentration of (1998b) showed that when timber stands were thinned, all soluble solids such as amino acids and salts. As a low-density stands had greater sugar concentration result, it may overestimate sugar concentration. than mid- or high-density stands. However, stands are However, our results show that the digital refract- typically thinned to 2,000 to 1,500 stems/ha in Japan, a ometer can be used to compare relative sugar much higher density than in North America, where concentration of Japanese cypress. thinning results in 250 to 325 stems/ha (Kimball et al. Using our results of vascular tissue mass of damaged 1998b). Sugar concentration is unlikely to increase by trees (243 g/m2), sugar concentration (9.2%), and thinning practices in Japan, because sugar concentra- peeled area (an average of 0.30 m2 of bark from each tion did not increase in mid-density (400 to 700 stems/ tree damaged [Yamada 2009], comparable to 4.3 ha) stands (Kimball et al. 1998b). square feet [0.40 m2; Noble and Meslow 1998] in There was no correlation between vascular tissue Oregon), we calculated the number of trees necessary mass and stand age. However, DBH had a positive to meet daily maintenance requirements for bears effect on vascular mass both in 2006 and 2007 based on the relationship between body mass and (Table 2). Similarly, vascular tissue mass was posi- energy requirement (Kleiber 1987). A 70-kg bear tively correlated with width of growth rings, which would have to peel the bark of 75–150 trees/day to represent tree growth (Table 2, Fig. 3). Since there obtain all its energy from this source. was positive correlation between width of growth rings and DBH (Table 2, Fig. 4), DBH can be regarded as representative of tree vigorousness in Management implications these stands. Mass of vascular tissues showed 7–10 Bear damage does not occur uniformly over the times more variation than sugar concentration of geographic range of the black bear in Japan;

Ursus 21(1):72–80 (2010) TREES VULNERABLE TO BEAR DAMAGE N Yamada and Fujioka 79 significant damage has been reported mostly in the on statistical analyses. Also, we thank S. Kamijo for central to southwestern part of the bear’s range helping us measure growth-ring widths and T. (Watanabe 1980), although damage has decreased in Arima, N. Bessho, M. Kawagoe, M. Kobayashi, S. the southwestern part due to the decline of some Kurihara, T. Morosawa, H. Saegusa, M. Sawada, T. isolated populations (Hazumi 2003). Bears mostly Terada, D. Toyoda, and Y. Tsuchiya for assistance fed on berries and insects in summer, and little tree in the field. damage was observed in the Chichibu Mountains (Hashimoto 2002), where the steep topography, natural vegetation, and altitude are similar to those Literature cited of our study area about 90 km southwest. Such local BARNES, V.G., JR., AND R.M. ENGEMAN. 1995. Black bear variation in the occurrence of bark stripping suggests damage to lodgepole in central Oregon. North- that either alternative food or appropriate forest western Naturalist 76:127–129. management can reduce bear damage, although the DEGUCHI, Y., S. SATO, AND K. SUGAWARA. 2003. Behaviour of Asiatic bear (Ursus thibetanus) and crop damage in reason for this variation remains unknown. the forage corn field. Nihon Chikusan Gakkaiho Yamazaki (2003) proposed that pruning, thinning, 74:383–388. (In Japanese with English summary.) and reducing undergrowth can reduce bear damage HASHIMOTO, Y., AND S. TAKATSUKI. 1997. Food habits of because he found less damage in stands with less Japanese black bears: A review. Mammalian Science visual obstruction in his study area, about 90 km east 37:1–19. (In Japanese with English summary.) and north from ours. We did not measure visual ———. 2002. Seasonal food habits of the Asiatic black obstruction, but little undergrowth was seen in most bear (Ursus thibetanus) in the Chichibu Mountains, of our study stands. In the United States, pruning Japan. Study 27:65–72. may reduce damage by American black bears HAYASHI, T. 1984. The people attacked by the Japanese (Kimball 1998c), whereas thinning may trigger black black bear — Instances in Fukui Prefecture from 1970 bear peeling (Mason and Adams 1989, Kimball et al. to 1983. Journal of the Mammalogical Society of Japan 10:55–62. (In Japanese with English summary.) 1998b). Therefore, improving visual obstruction in a HAZUMI, T. 2003. Bear damage and forestry in the future. stand might not necessarily reduce bear damage in Shinrin Kagaku 39:4–12. (In Japanese.) some areas, including ours. HENNON, P.E., E.M. HANSEN, AND C.G. SHAW, III. 1990. Our research and the work of several other Causes of basal scars on Chamaecyparis nootkatensis in scientists suggest that vigorous trees have a relatively southeast Alaska. Northwest Science 64:45–54. rich mass of vascular tissues, and larger diameter HUYGENS, O.C., F.T. VAN MANEN, D.A. MARTORELLO,H. trees are more likely to be damaged by bears than HAYASHI, AND J. ISHIDA. 2004. Relationships between smaller diameter trees within a stand. To reduce bear Asiatic black bear kills and depredation costs in damage, it is advisable that foresters focus protec- Nagano Prefecture, Japan. Ursus 15:197–202. tion efforts such as net- or tape-wrapping on larger INTERNATIONAL UNION FOR CONSERVATION OF NATURE. diameter trees to decrease foraging efficiency for 2008. 2008 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland, http://www.iucnredlist.org, bears. The mass of vascular tissues did not correlate accessed 10 December 2008. with tree age, suggesting that such protection must JAPAN WILDLIFE RESEARCH CENTER. 2005. Research report be continued for several years until harvest. on widespread appearance of Asiatic black bears. Japan Wildlife Research Center, Tokyo, Japan. (In Japanese.) KADOWAKI, S., T. ENDOH,M.WADE,A.TAKINAMI, AND T. Acknowledgments OHTSUBO. 1997. A study of ecology and natural history This study was partly conducted as the master’s of Japanese black bear Ursus thibetanus and its damage thesis of A. Yamada supervised by M. Fujioka. We to forest trees at Tsukuba university forest at Ikawa. I. are appreciative of B.A. Kimball, T. Nakamura, and A report on the status of bear damage to forest trees. T. Kamijo, who gave us useful comments on earlier Bulletin of Tsukuba University Forests 13:73–102. (In Japanese with English summary.) manuscripts. We thank F. Imaizumi, who provided KIMBALL, B.A., D.L. NOLTE, R.M. ENGEMAN, J.J. JOHN- GIS data for the Ikawa University Forest and T. STON, AND F.R. STERMITZ. 1998a. Chemically mediated Endoh, A. Takinami, Y. Endoh, and Y. Shibata, foraging preference of black bears (Ursus americanus). who gave us logistic support in the field. This study Journal of Mammalogy 79:448–456. could not have been done without advice from E. ———, ———, D.L. GRIFFIN, S.M. DUTTON, AND S. Nozaki on tissue sampling and from T. Morosawa FERGUSON. 1998b. Impacts of live canopy pruning on

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