Effects of bark stripping by sika deer, Cervus nippon, on wind damage to coniferous trees in subalpine forest of central Japan

We evaluated the effect of bark stripping by sika deer (Cervus nippon), and subsequent wood decay, on tree fall in a coniferous forest on Mt Ohdaigahara in central Japan from July to September 2006. This valuable primeval coniferous forest is declining because of bark stripping. Broken trunks of Abies homolepis and Picea jezoensis var. hondoensis had more serious decay and larger bark-stripping wounds on the trunk than standing trees, suggesting that bark stripping causes trunk decay and results in broken trunks and uprooting by typhoons.     

Population density and range use of sika deer,Cervus nippon, on Mt. Ohdaigahara, central Japan

We investigated the population density and range use of sika deer,Cervus nippon, on Mt. Ohdaigahara, central Japan, from July 1996 to July 1997. The deer population density estimated by the block count was high at 17.5–30.9 deer/km². Although the deer remained this area from spring to fall, they moved out in winter, probably because of deep snow. A spotlight count showed that the deer prefer the eastern area as spring-summer range, where the forest consists of coniferous trees over a floor cover ofSasa nipponica, andS. nipponica grassland. The deer also use dense coniferous forest for cover, especially in summer and fall. Part of this study was presented at the 108th Annual Meeting of the Japanese Forestry Society (1997). This study was financially supported by the Environment Agency, Japan.     

Bark stripping by sika deer on veitch fir related to stand age, bark nutrition, and season in northern Mount Fuji district, central Japan

We carried out this study to clarify the relationships between the seasonal changes of bark stripping and food quality, and between bark-stripping intensity and bark nutrition with age of veitch fir (Abies veitchii) by sika deer (Cervus nippon) in the northern Mount Fuji district, from June 2000 to July 2003. We found that sika deer gnawed and ate all of the bark stripped, and a seasonal change in bark stripping occurred from December to May or June with a peak in March–April. The stripping period largely overlapped with the periods of low food availability and poor food nutrition (indicated by fecal chemical component index) of sika deer, from January to April. Both bark nutritional quality and bark-stripping intensity related to stand age and tree size of veitch fir negatively. Consequently, bark-stripping intensity related to bark nutritional quality positively. February is the worst forage period in terms of both quantity (due to deep snow) and quality (indicated by fecal chemical components). There was a time lag of 1 to 2 months in the peak of bark stripping in March–April when compared with the poor forage period in February. This time lag may suggest that sika deer need more nutritious and easily digested food from March due to increased nutrient demands that result from depleted body condition in both sexes, gestation of pregnant females, and the recovery of active metabolism.     

Food habits of sika deer as assessed by fecal analysis in Mt. Ohdaigahara,central Japan

Food habits of sika deer,Cervus nippon centralis temminck, in Mt. Ohdaigahara, central Japan, were investigated by the fecal analysis method from September, 1990, to June, 1991. The fecal analysis showed that the percentage ofSasa nipponica Makino et Shibata in the fecal composition was approximately 50% throughout the year, indicating that it was the main food plant. Bark and twigs were also found in the feces in all seasons, suggesting that the deer ate bark throughout the year. Even though the amount of the bark eaten per capita was small, the high density of deer may possibly cause serious bark damage. Barking can be one of the main causes of the mortality ofPicea jezoensis Sieb. et Zucc. var.hondoensis (Mayr) Rehder andAbies homolepis Sieb. et Zucc. in Mt. Ohdaigahara. A part of this study was presented at the 105th Annual Meeting of the Japanese Forestry Society (1994).     

Resistance of larches to bark stripping by sika deer in Hokkaido,northern Japan

Resistance of the Japanese larch (Larix kaempferi) (Lk), the Kurile larch (L. gmelinii var. japonica) (Lg), and their F₁ hybrid (Lg × Lk) to bark stripping by sika deer (Cervus nippon yesoensis) were studied in a forest in Hokkaido by cafeteria tests. Several sets of logs prepared from Lk, Lg, and Lg × Lk were fed to the deer. The stripped areas of logs significantly differed between the Lk/Lg set and the Lk/Lg × Lk set (P 0.05). The resistances of Lg and Lg × Lk to bark stripping was stronger than Lk. This result was similar to those of previous studies on gray-sided voles and mountain hares in Hokkaido.     

Altitudinal differences in bark stripping by sika deer in the subalpine coniferous forest of Mt. Fuji

Deer expansion is a growing concern for forest ecosystem management. In Japan, upward expansion to subalpine and alpine areas has reached alarming proportions in recent years. We examined bark stripping by sika deer along an altitudinal gradient in the subalpine coniferous forest at three altitude ranges (1800-2000 m, 2000-2200 m, and 2200-2400 m) on the southern slope of Mt. Fuji. We tested differences in densities and diameter at breast height (DBH) of trees and those with bark-stripped stems of all tree species among the three altitude ranges. Then, we compared the relative densities of deer, based on pellet counts, to determine the impact of deer in relation to deer use and forest stand patterns across the altitudinal range studied. The results of the study show that differences in bark stripping by sika deer depended largely on the elevation and the species. Larger stems were sparsely distributed in the lowest elevation zone between 1800 and 2000 m. The relative density of deer was highest in the areas exhibiting high bark-stripping intensity on small regenerating trees of the dominant coniferous species, Abies veitchii, and on broadleaf species. In the highest elevation zone between 2200 and 2400 m, smaller stems were densely distributed, and the relative deer density was lowest where the bark-stripping intensity on small stems was lower for all three species studied. The damage to subalpine tree stems corresponded to the availability of palatable tree species with a small diameter, as reflected by the successional stage along the elevational gradient of subalpine forest on Mt. Fuji. These results suggest that the continuous impact of bark stripping on the dominant tree species might cause severe changes in forest succession.     

Deer-proof fence prevents regeneration of Picea jezoensis var. hondoensis through seed predation by increased woodmouse populations

The indirect consequence of sika deer (Cervus nippon) grazing on the regeneration of Picea jezoensis var. hondoensis through its effect on the small rodent population was assessed by evaluating seed predation by mice inside and outside the deer-proof fence on Mt Ohdaigahara, central Japan. Following construction of the deer-proof fence, Sasa nipponica, which covers the forest floor and is the main forage of deer, grew thicker inside the fence due to the absence of deer grazing than outside of the fence. Higher numbers of two species of woodmice (Apodemus speciosus and A. argenteus) were found inside the fence, possibly because the thick S. nipponica growth provides better cover. Inside the fence, more seeds of P. jezoensis var. hondoensis were eaten by the mice than outside the fence. These results suggest that the mouse populations inside the fence increased due to changes in S. nipponica cover, which subsequently increased seed predation by the mice, possibly preventing regeneration of P. jezoensis var. hondoensis.     

Assessing decline in physical structure of deciduous hardwood forest stands under sika deer grazing using shrub-layer vegetation cover

For 345 stands of deciduous hardwood forest in Hyogo Prefecture, Western Japan, we assessed the decline of shrub-layer vegetation due to sika deer in each stand by using the shrub-layer decline rank (SDR), determined by combining the shrub-layer vegetation cover and the presence of signs of grazing by sika deer in a stand. Since there was a geographical correlation between SDR and sighting per unit effort (SPUE), which is an index of the relative density of sika deer, it appeared that decline of shrub-layer vegetation in a stand can be accurately evaluated by SDR. There were correlations between SDR and several variables that indicate the status of components in forests (presence of saplings of tall trees, occurrence of bark stripping of tall trees, proportion of bark-stripped stems of Clethra barvinervis, decline of subtree-layer vegetation by bark stripping, cover of litter on the ground, and area of soil surface erosion). These results indicate that the status of these components changes with decline of shrub-layer vegetation by sika deer grazing. It is thought that such synchronizations are caused by sika deer grazing or a direct or indirect effect by decline of shrub-layer vegetation due to sika deer. Therefore, it is reasonable to assess decline in physical structure due to sika deer for stands of deciduous hardwood forests according to SDR.     

Effects of deer and mice on seedling survival in a temperate mixed forest of Japan

To detect the magnitude of indirect positive effects of deer and mice on seedling survival of some woody species in a Japanese temperate forest, we analyzed the data from an earlier field experiment using a hierarchical Bayesian approach. The forest studied was inhabited by sika deer (Cervus nippon) and mice (Apodemus spp.), and the floor was covered with dwarf bamboo, Sasa nipponica, which negatively affected tree seedlings and was in turn negatively affected by deer and mice. The field experiment was designed as the combination of exclusion or removal of these factors: deer, mice and dwarf bamboo. A hierarchical Bayesian model was constructed and the parameters were estimated by the Markov chain Monte Carlo method. The model successfully showed the indirect positive effects of deer and mice, which improved the survival rate of five cohorts of the seedlings of three tree species by ameliorating the direct negative effect of dwarf bamboo. The cohorts studied were formed by the seedlings of Abies homolepis that emerged in 1997 and 2002, those of Fraxinus lanuginosa f. serrata that emerged in 1998 and 2002, and those of Fagus crenata that emerged in 1999. The positive indirect effect was especially large in F. crenata, which is known to be severely affected by dwarf bamboo. The total effect of deer was shown to be positive for all cohorts except the A. homolepis cohort that emerged in 1997, at which time the dwarf bamboo had not yet fully recovered from the browsing pressure of deer. The total effect of mice was shown to be positive for all of the cohorts. We conclude that these positive effects were due to the large negative effect of dwarf bamboo on the seedlings.     

Effects of heavy,repeated bark stripping by Cervus nippon on survival of Abies veitchii in a subalpine coniferous forest in central Japan

The management of deer impacts on forested lands requires quantification of the negative factors(e.g.,bark stripping) on tree survival in relation to other ecological variables(e.g.,competition from neighboring trees).This study measured the effects of bark stripping by sika deer,Cervus nippon,and competition among trees on the survival of Abies veitchii in a subalpine coniferous forest in central Japan over 12 years.Most of the trees subjected to bark stripping by deer were small(10 cm in diameter at breast height);however,some trees were stripped repeatedly.Although light bark stripping did not strongly influence tree survival after 12 years,heavily stripped stems(i.e., 65% of the stem circumference stripped) were severely affected.The effect on longevity for each tree after bark stripping was explained by maximum bark stripping intensity during the study period,rather than initial bark stripping intensity.When 85% of the stem circumference had been stripped,survival rates decreased.Bark stripping influenced survival rates much more than competition from neighboring trees.Because bark stripping occurred repeatedly,frequent measurements are important to grasp the full effects caused by this action.Heavy bark stripping of a stem enhances tree mortality.Thus,management of bark stripping is an essential element of stand maintenance and species composition in subalpine coniferous forests in Japan.     

Over-winter weight dynamics in supplementally fed free-ranging sika deer (Cervus nippon)

Continuous body weight dynamics in supplementally fed free-ranging sika deer (Cervus nippon) during the three consecutive overwinters (from January to April), 1992–1994 were surveyed. Almost all individuals lost weight continuously throughout each winter (adult deer 5–13%; young deer 3–19%) and several deer lost weight even in April. Weight gain after loss began in the mid-April when ambient temperature increased and when plant growth began. Weight dynamics varied according to sex, age and reproductive status. Adult deer showed significant large weight loss than the young. Young deer lost weight (calves 18±11 g/day, yearling and two-year-olds 27±29 g/day) more slowly than the adults (65±23 g/day). Following this study of over-winter body weight dynamics, it seems that early springs are the most critical periods for the survival of free-ranging sika deer because of their poor nutritional condition. A portion of this report was presented at the 106th Annual Meeting of the Japanese Forestry Society (1994).     

Development of a method for forest cafeteria tests for evaluating chemical deterrents against bark stripping by sika deer (Cervus nippon yesoensis)

Damage caused by sika deer (Cervus nippon yesoensis) is a serious problem in commercial and environmental (non-harvested) forests in Hokkaido, northern Japan. Cafeteria tests in forests may be useful for evaluating the efficacy of chemical deterrents against bark stripping by deer. To develop a method for forest cafeteria tests in the continuous snow cover period, two experiments were carried out. In the experiments, logs were produced from tree trunks, and used as carriers of chemical deterrents. Carriers were installed in forests and fed to deer. The first experiment was to find suitable sites and installation methods for carriers. Criteria for the local suitability and the installation methods were as follows: a) Sites where deer are active should be selected; b) Carriers should be installed along actively used deer trails; c) Installation sites of carriers should be changed in response to deer movement; d) Carriers should be produced from tree species that deer naturally prefer; and e) Each carrier should be partially buried in the snow. The second experiment evaluated the feasibility of a cafeteria test method based on the results of the first experiment. The method was used for 13 sets of the cafeteria test, in which the deterrent effectiveness of 5 chemicals (wood tar, rosin, wood vinegar, and 2 pyroligneous liquors) was examined. We obtained results from all the sets. The chemicals tested did not deter bark stripping by deer. Nevertheless, the method used in the present study was practical for the cafeteria tests.     

Height growth of young larch (Larix kaempferi) in relation to the frequency of deer browsing damage in Hokkaido, Japan

The effect of browsing frequency by Sika deer (Cervus nippon yezoensis) on the height growth of Japanese larch (Larix kaempferi) in Hokkaido, Japan, was analyzed. Tree heights at the time of the census and at the start of the current growing season were determined for 100 trees selected randomly at each site. The tallest shoot on each tree was identified and the number of browsing occurrences on the current-year shoot was determined. Young larches browsed by deer repeatedly develop new shoots during a growing season. Larch is a browsing-tolerant species, and the average height growth of the most heavily browsed trees was >15 cm. Although resprouting partly compensated for decreased height growth caused by browsing, the annual increase in height decreased with increased browsing frequency. Thus, browsing frequency during a growing season best reflects the intensity of browsing damage to larch trees.     

Effects of sika deer (Cervus nippon) and dwarf bamboo (Sasamorpha borealis) on seedling emergence and survival in cool-temperate mixed forests in the Kyushu Mountains

Effects of sika deer (Cervus nippon) and dwarf bamboo (“sasa;” Sasamorpha borealis) on seedling emergence and survival were investigated in cool-temperate mixed forests in the Kyushu mountain range, Japan. We compared the effects of sika deer between two sites with different sika deer densities. One site (no-sasa forest) has sparse cover of S. borealis and a high density of sika deer, and the other site (sasa forest) has dense cover of S. borealis with a low density of sika deer. In the no-sasa forest, more seedlings emerged and the survival rate of the seedlings was higher compared with the sasa forest. Compared with the sasa forest, the canopy in the no-sasa forest was more open, the organic layer was shallower and drier, the mean daily soil temperature was higher, and soil temperature fluctuated more widely. Those environmental parameters did not differ between unfenced and fenced plots. The comparison between the sasa and no-sasa forests suggested that removal of S. borealis by sika deer had an indirect positive effect on seedling emergence and survival. However, the fenced-plot experiments indicated that sika deer inhibited seedling emergence and survival. These contradictory conclusions could result from the much larger negative effects of S. borealis on seedling emergence and survival compared with the effects of sika deer browsing.     

Impact of bark stripping by sika deer, Cervus nippon, on subalpine coniferous forests in central Japan

We investigated the effect of bark stripping by sika deer, Cervus nippon, on forest regeneration in subalpine coniferous forests on Mt. Ohdaigahara and in the Ohmine Mountains of central Japan. Bark stripping by sika deer occurred in five major tree species: Abies homolepis; Abies Veitchii; Tsuga diversifolia; Picea jezoensis var. hondoensis; and Chamaecyparis obtusa. The percentage of damaged trees on Mt. Ohdaigahara was higher than in the Ohmine Mountains, probably because of the higher deer density. On Mt. Ohdaigahara, the DBH distributions of stems for P. jezoensis var. hondoensis, A. homolepis, T. diversifolia andC. obtusa were bell-shaped with fewer smaller and larger trees. On the other hand, in the Ohmine Mountains the distributions for P. jezoensis var. hondoensis and A. Veitchii showed a reverse-J shaped with more smaller trees. Larger overstory conifers on Mt. Ohdaigahara were killed by bark stripping when 100% barked, although in the Ohmine Mountains ca. 50% of the trees survived even when 100% barked. After the disappearance of the overstory conifers on Mt. Ohdaigahara, the dwarf bamboo, Sasa nipponica, expanded into the forest floor due to changes in light reaching the forest floor. Since S. nipponica is the main forage of deer in this area, this increase caused a corresponding increase in the deer population, which in turn, could cause a further decline in the coniferous forests.     

Effects of deer browsing on the survival and growth of <Emphasis Type="Italic">Abies homolepis</Emphasis> and <Emphasis Type="Italic">Picea jezoensis</Emphasis> var. <Emphasis Type="Italic">hondoensis</Emphasis> seedlings after fencing on Mt. Ohdaigahara

We evaluated the survival and growth of Abies homolepis and Picea jezoensis var. hondoensis seedlings on Mt. Ohdaigahara, where the population of sika deer (Cervus nippon) is high and an experimental fence has been in place for 13 years. No significant differences were detected in the survival of small seedlings between fenced and unfenced plots. The growth of A. homolepis was significantly higher in the fenced plot, but growth of P. jezoensis var. hondoensis did not show significant differences between fenced and unfenced plots. Seedlings of height ≤5 cm in the forest floor vegetation of the unfenced plot were probably too small for deer to find and browse, so they survived.     

Pine needle consumption and bark stripping by sheep grazing annual pastures in young stands of widely spaced Pinus radiata and P. pinaster

The consumption of the pine needles and the stripping of bark by sheep grazing annual pastures in three open stands of P. radiata and one of P. pinaster were measured. The P. radiata were four years old and the densities were 250, 500 and 750 trees ha^-1. The P. pinaster included two, three and four year-old trees and the density was 440 trees ha^–1.Needles were eaten immediately after the sheep were admitted and this continued throughout the year. Within ten weeks of the start of winter grazing, sheep stocked at 7–10 ha^–1 had eaten about half of the accessible needles on both species where densities were less than500 trees ha^–1. The estimated consumption was about 260 g sheep^–1 day^–1 for the P. radiata. Bark stripping then commenced and continued throughout spring and summer on most plots. In some plots at low tree density, bark was stripped from more than 35% of the trees. In denser stands, needle consumption per tree was less and bark was stripped from less than 5% of the trees.Bark damage was most common on the smaller trees, and severity of stripping was negatively correlated with tree size. Of all the trees with bark damage, 22% of the P. pinaster and 14% of the P. radiata had more than half of the stem circumference stripped. A number of these will probably suffer both stem distortion and growth retardation, and some may die.Methods of reducing the incidence of bark damage are discussed.     

Virulence of ophiostomatoid fungi associated with the spruce bark beetleIps typographus f.japonicus in Yezo spruce

Yezo spruce trees (Picea jezoensis), approximately 40-year-old were inoculated with eight ophiostomatoid fungi associated withIps typographus f.japonicus to compare relative virulence of the fungi. Among them,Ophistoma penicillatum formed the longest necrotic lesion on inner bark around inoculation points, followed byO. aenigmaticum, Ceratocystis polonica, andO. bicolor, whileC. polonica formed a larger dry zone in sapwood than the other fungi. Yezo spruce trees were also mass inoculated withC. polonica, O. penicillatum, O. piceae singly or mixed to demonstrate the ability of the fungi to kill Yezo spruce trees. The trees inoculated withC. polonica, O. penicillatum or the mixed inoculum showed discoloration of needles in the early summer of the next year and died by autumn. However, the trees inoculated withO. piceae or the control inocula did not die, except for one tree. These results indicated thatC. polonica andO. penicillatum were more virulent thanO. piceae and suggested that they might be at least partially responsible for the mortality of the beetle-infested Yezo spruce trees. Part of this study was supported by the Sumitomo Foundation, Japan to Y. Yamaoka and I. Takahashi. Part of this study was presented at the 107th meeting of the Japanese Forestry Society, April 1–4, 1996, Tsukuba, Ibaraki, at the 42nd annual meeting of the Mycological Society of Japan, May 16–17, 1998, Kyoto, and at the 110th meeting of the Japanese Forestry Society, April 2–5, 1999, Matsuyama, Ehime. Contribution No. 143, Laboratories of Plant Pathology and Mycology, Institute of Agriculture and Forestry, University of Tsukuba.     

Host selection of small cedar longicorn beetle, <Emphasis Type="Italic">Callidiellum rufipenne</Emphasis> (Coleoptera:Cerambycidae), on Japanese cedar, <Emphasis Type="Italic">Cryptomeria japonica</Emphasis>, in terms of bark water content of host trees

We caught the adults of a secondary wood-boring insect, Callidiellum rufipenne (Motschulsky), on Japanese cedar, Cryptomeria japonica D. Don., trees and logs with manipulated bark water contents to clarify the mechanism of host selection by C. rufipenne. More C. rufipenne were trapped when the bark water content range was ca. 120–200%. Fewer C. rufipenne were trapped at higher and lower bark water contents. These findings indicate that C. rufipenne adults do not simply select weakened or dying trees. Bark water content is one of important factors for C. rufipenne choosing their host for oviposition.     

Effects of 13-year fencing on browsing by sika deer on seedlings on Mt. Ohdaigahara, central Japan

We examined the effects of fencing on deer browsing on seedlings 13 years after the building the experimental fence on Mt. Ohdaigahara, central Japan, where the sika deer (Cervus nippon) population is high. There was no difference in the species number of seedlings between 1991 and 2004. The density of seedlings in the fenced plot in 2004 was three times higher than in 1991. Although the unfenced plots had no seedlings higher than 20 cm, there were seedlings up to 120 cm in the fenced plot. These results suggest that 13-year fencing promoted regeneration of seedlings in this area.