A case study on the effects of a transmission-line corridor on Sika deer habitat use at the foothills of Mt Goyo,northern Honshu,Japan

Forage biomass and habitat use of Sika deer (Cervus nippon) at a transmission-line corridor were studied at the foothills of Mt Goyo, northern Japan. Summer forage biomass in the corridor was five times greater than in the adjacentBetula grossa forest. Among the plants that increased in the corridor,Sasa nipponica (a dwarf bamboo), an important forage plant for Sika deer, was predominant. Winter utilization ofS. nipponica by Sika deer was slightly heavier in the corridor, and estimated removal ofSasa leaves was twice as great there as in the forest. However fecal pellets were more prevalent in the adjacent forest in winter. Sika deer seemed to use the transmission-line corridor as a feeding site and the adjacent forest as cover as it reduces wind speed. A transmission-line corridor is more beneficial than a large clear-cut area because it provides more forest edges.     

Food habits of Sika deer on Mt. Goyo,northern Honshu

The food habits of Sika deer (Cervus nippon) on Mt. Goyo, northern Honshu (the main island of Japan), were studied. Among 88 plant species found in surveys, 36 species (40.9%) were eaten by the deer. The percentage frequency of feeding (F) was highest for graminoids (59.6%), followed by browses (16.6%) and ferns (7.7%) and lowest for forbs (5.4%). Though various kinds of plants were eaten, only limited species formed the bulk of the deer dietary composition.Sasa nipponica, in particular, was the most important constituent, ranking highest inF value (80.3%) and being the dominant component of feces. Fecal analyses revealed that, 1) in areas lower than 900 m in altitude,Sasa nipponica accounted for between 20 and 60% of the content and that pasture grasses were also important, and 2)S. nipponica occupied more than 50% in montane areas higher than 900 m, and even more than 80% in winter. The utilization ofS. nipponica as a forage for Sika deer was discussed. This plant can be a key forage species because it meets all the necessary conditions: abundance and stability of supply, palatability, nutritive quality and tolerance to grazing.     

Use of mires and food habits of sika deer in the Oze Area,central Japan

Sika deer Cervus nippon entered the Oze Area, a snowy area in central Japan, in the 1990s. The use of mires and the food habits of this species were studied in 1999 and 2000. Deer used the mires immediately after snow melted and did not use the mires in mid summer, although they did use them lightly in autumn. The summer food habits differed from those of the deer population living in Nikko in the lower area: non-Sasa graminoids and other monocotyledonous leaves occupied more (approximately 30%) of the feces in the former population, whereas Sasa nipponica, a dwarf bamboo, was the dominant food (60%) of the latter population. Seasonal changes in fecal composition in the Oze deer were that mire graminoids occupied a considerable portion of their food in spring (11.6%) and summer (17.0%), whereas the amount of dwarf bamboo increased in fall (26.0%). Despite the small size of the mires, Oze deer appear to prefer mires to forests. Nitrogen concentrations of the mire plants did not differ from those of the forest plants; however, foraging efficiency would be greater in the mires and this may explain the preference observed. Despite the small total biomass, leaf biomass of the mire was equivalent to that of the adjacent forest floor. In addition, biomass was concentrated near the ground, or the biomass concentration was greater than that of the forest floor.     

Diversity of dung-beetle community in declining Japanese subalpine forest caused by an increasing sika deer population

The Ohdaigahara subalpine plateau in Japan has recently suffered a reduction in primary forest land caused by an increasing population of sika deer (Cervus nippon). Deer have debarked many trees, causing dieback, gradually changing the primary forest first to light forest with a floor that is densely covered with sasa grass (Sasa nipponica) and then to S. nipponica grassland. To examine the effects of vegetative transformation on the dung-beetle community, we compared the diversity and abundance of dung-beetle assemblages in the primary forest, transition forest, and S. nipponica grassland using dung-baited pitfall traps. The species richness and species diversity (Shannon-Wiener index) were significantly highest in the primary forest and lowest in the S. nipponica grassland. The evenness (Smith-Wilson index) was highest in the primary forest and nearly equal in the transition forest and S. nipponica grassland. The abundance was apparently greater in the transition forest than in the primary forest and S. nipponica grassland. These results suggest that loss of primary forest resulting from an increasing deer population decreases the diversity of the dung-beetle community while increasing the abundance of dung beetles in the transition forest. Sika deer use transition forests and grasslands more frequently than primary forests as habitat, but an increase in dung supply there does not necessarily increase the diversity or abundance of dung-beetle assemblages.     

Botanical and chemical composition of rumen contents of Sika deer on Mt Goyo,northern Japan

Botanical and chemical compositions of the rumen contents of 58 Sika deer on Mt Goyo, northern Japan, collected from summer of 1988 to spring of 1989, were analyzed.Sasa nipponica, a dwarf bamboo, was important in summer (35.0%) and winter (61.4%), but it decreased to 5.6% and was replaced by browse leaves in fall, and to 28.0% and was replaced by dead leaves, twigs and bark of woody plants in winter. Crude protein was 20–25% lower in the washed fraction than in the gross fraction. It was highest (16.2%) in summer and lowest (8.6%) in winter. High protein content in summer and fall foods was attributed to forb and browse leaves. Seasonal fluctuation in protein content in the foods of these Sika deer was greater than red deer on Rhum, Scotland and smaller than wapiti in Yellowstone National Park, Wyoming, USA. Climatically, winter severity of Mt Goyo is intermediate between the two localities, which seems to explain the seasonal fluctuation of the protein level. Crude fiber wasca 33% in the ‘washed’ fraction, and did not change seasonally.     

Characteristics of Sasa nipponica grassland as a summer forage resource for sika deer on Mt Ohdaigahara, central Japan

Recently, the sika deer, Cervus nippon Temminck, population has increased on Mt Ohdaigahara, central Japan. The dwarf bamboo, Sasa nipponica Makino et Shibata, is a primary forage plant for sika deer in this area. To demonstrate the characteristics of S. nipponica grassland, especially as summer forage for sika deer, the habitat use intensity of sika deer was estimated by fecal densities, and biomass, growth rate, removal by deer and crude protein content were examined. Sika deer utilized the S.nipponica grassland on Mt Ohdaigahara during summer when the biomass, growth rate and crude protein content of S. nipponica were high. The recent increase in the deer population seems to be partly due to S.nipponica grassland being a favorable summer habitat.     

Summer dietary compositions of sika deer on Yakushima Island,southern Japan

Summer food habits of Sika deer (Cervus nippon yakushimae) on Yakushima Island, southern Japan, were studied focusing in particular onPseudosasa owatarii, a dwarf bamboo native to the island. Fecal analyses showed that the food habit of the Sika deer on Yakushima island was plastic: the dietary composition was dominated by graminoids (ca. 90%), particularlyP. owatarii (50%–60%) in the bamboo grassland of theP. owatarii zone above the timber line, whereas leaves and non-leafy parts of woody plants were important in the crytomeria forest and evergreen broad-leaved forest below the timber line. The maximum culm age ofP. owatarii was 8.5 yr, but the majority of leaves (97.8%) were younger than 2.5 yr. Since the weight contribution of the leaves is great (27.7%) and the turnover rate is high, theP. owatarii grassland affords a good foraging place for the Sika deer on Yakushima Island.     

How do deer affect tree seedlings on a dwarf bamboo-dominated forest floor?

A field experiment was conducted in Mt. Ôdaigahara, west-central Japan, to reveal the effects of two herbivores, Sika deer (Cervus nippon) and mice (Apodemus spp.), on the seedlings of five cohorts of three tree species, Abies homolepis, Fraxinus lanuginosa f. serrata and Fagus crenata. The forest floor of the study site was covered with dwarf bamboo, Sasa nipponica, which would also affect the seedlings. Eight combinations of three treatments were set: exclusion of deer, exclusion of mice and removal of dwarf bamboo. Deer were expected to affect the seedlings not only negatively by foraging but also positively by browsing dwarf bamboo that overshadows seedlings. The survival of these cohorts was analyzed by survival analysis and the differences in their survival between the treatments were investigated. The results of the experiment showed that: (1) exclusion of deer increased the aboveground biomass of dwarf bamboo and made it more difficult for seedlings to survive under the regenerated dwarf bamboo stand, and (2) deer negatively affected the seedlings, but they had positive, indirect effects in some cohorts by decreasing the aboveground biomass of dwarf bamboo. However, such effects were not detected in some cohorts which were affected excessively by deer or dwarf bamboo. No clear results on the effect of mice on seedlings were obtained. We conclude that a positive, indirect effect of deer on seedling survivorship would be observable when the magnitude of a positive, indirect effect caused by decreasing dwarf bamboo is larger than that of a negative, direct effect of deer.     

Development and characterization of polymorphic microsatellite DNA markers for Sasa senanensis (Poaceae: Bambuseae)

Sasa senanensis is a dwarf bamboo species distributed on the floors of cool temperate forests in Japan and adjacent regions. We isolated eight polymorphic microsatellite loci from this species. The number of alleles ranged from two to eight and the observed heterozygosity per locus from 0.13 to 0.74. Seven of the eight loci were also polymorphic in Sasa nipponica. Most of these markers were successfully amplified in other dwarf bamboo species. These markers will be useful for investigating clonal structure and population genetics in some dwarf bamboo species.     

Effects of deer,mice and dwarf bamboo on the emergence,survival and growth of <Emphasis Type="Italic">Abies homolepis</Emphasis> (Piceaceae) seedlings

In the subalpine mixed forest of Mt. Ôdaigahara, mid-western Japan, the understory is dominated by dwarf bamboo (Sasa nipponica), which is the major forage of overly populous sika deer (Cervus nippon). In the present study, we monitored the survival and growth of Abies homolepis seedlings over 5years to determine how they responded to the experimental removal of dwarf bamboo and to the exclusion of sika deer and mice (Apodemus argenteus and A.speciosus). Deer and dwarf bamboo reduced the survival of seedlings but had different effects on growth. The stems of seedlings were shorter in the presence of deer, indicating that taller seedlings were apt to be browsed by deer, whereas the diameters of seedlings were smaller in the presence of dwarf bamboo, mainly owing to its shading effect. The presence of mice decreased the number of seedlings germinating in a particular site, but had no effect on seedling survival after germination. There was no significant indirect effect whereby the survival of seedlings was predicted to be facilitated by the decreased biomass of bamboo because of grazing by deer. We supposed that this might be because the direct negative effect of deer was so large as to conceal the positive indirect effect.     

Food habits of sika deer in the Shiranuka Hills,eastern Hokkaido: a northern example from the north–south variations in food habits in sika deer

Seasonal changes in the composition of the diet of the sika deer population in the Shiranuka Hills, eastern Hokkaido, in 1998 were determined by fecal analyses. The deer were dependent on Sasa nipponica, a dwarf bamboo, throughout the year, particularly in winter when it accounted for as much as 77.7% of the diet. It accounted for 33.1% and 45.6% in spring and summer, respectively, and this decreased to 12.2% in autumn. Besides S. nipponica, all the graminoid categories accounted for large amounts (66–96.7%), while dicotyledonous plants accounted for little (3–8%) except in autumn when they accounted for 31%. The strong dependence of the Shiranuka population on graminoids was different from other Hokkaido deer populations, for example the population from Ashoro/Onbetsu and the extremely high density population on Nakanoshima Island. In spite of these differences, food for all Hokkaido sika deer was poor in winter. Along the north–south geographical cline in the food composition of sika deer along the Japanese archipelago, the Shiranuka population was positioned as a grazer type, in contrast to the southern populations. However, it is important to note that variations are great among local populations in Hokkaido.     

Dwarf bamboo as an ecological filter for forest regeneration

Quantitative relationships between the aboveground biomass of dwarf bamboo, Sasa nipponica, and the survivorship and emergence of seedlings of Abies homolepis, Fraxinus lanuginosa f. serrata, and Fagus crenata were estimated. We show that dwarf bamboo acts as an ecological filter since the responses of tree species differ according to the biomass of dwarf bamboo. Deer exclusion without management of dwarf bamboo would make it impossible for any tree species to regenerate due to rapid increases in the biomass of dwarf bamboo.     

A comparison of food habits of two sympatric ruminants of Mt. Yatsugatake,central Japan: sika deer and Japanese serow

Comparison of food habits of sympatric animals provides understanding of interspecific relations. Previous studies of food habits of the two ruminants of Japan, sika deer (Cervus nippon) and Japanese serows (Capricornis crispus), have shown that sika deer are variable, and they are gazers in northern Japan, but browsers in southern Japan, whereas Japanese serows are browsers. However, these studies described the food habits of each species separately, and no study has compared the food habits of these species living in sympatry. Therefore, we examined these species on Mt. Yatsugatake, central Japan, using microhistological analyses and nutritional analyses of feces. Sasa nipponica, a dwarf bamboo, predominated in the fecal composition of sika deer, whereas both S. nipponica and dicotyledonous plants were found in the feces of Japanese serows. Crude protein levels of serow feces were higher than those of deer. The particle sizes of plant fragments in serow feces were smaller than those in deer feces, suggesting that serow fed more selectively on digestible plants than deer did. These results support the suggestions of previous studies conducted in different habitats and show that sika deer are less selective grazers, and Japanese serows are more selective browsers. Thus, food differences are likely explained by the feeding ecophysiology of the animals and not habitat differences.     

Effects of Sika deer on the regeneration of aFagus crenata forest on Kinkazan Island,northern Japan

Kinkazan Island, a sanctuary island that has been conserved for over 100 years, is inhabited by a Sika deer population of high density (60 km⁻²). AFagus crenata forest, a climax forest of this region, was composed of only large sized trees (30–60 cm diameter breast height) and lacked young trees. However, many saplings were found inside a deer proof fence, indicating this forest had a potential to produce seedlings. They were tentatively protected by shrubs ofLeucothoe grayana var.glabra, an upalatable ericaceous shrub, but did not exceed the shrub height. Heavy browsing by the deer suppressed recruitment of saplings ofF. crenata. The forest will be reduced without population control of the deer.     

Suppression of Regeneration in New Zealand Mountain Beech Forests is Dependent on Species of Introduced Deer

We compared the impacts on forest regeneration of introduced sika (Cervus nippon) and red (Cervus elaphus) deer in New Zealand. Plot data were used to compare mountain beech (Nothofagus solandri var. cliffortioides) regeneration between a region with sika deer, and four regions without sika deer. All regions surveyed had red deer present. In the region where sika deer had been present for more than a decade, there was evidence of poor mountain beech seedling regeneration. In the four regions without sika deer, there was evidence of a strong regenerative response at stands with low occupancy by trees. When compared to larger deer species, sika deer have a digestive morphology allowing greater dietary versatility, which may result in them impeding forest regeneration where red deer do not. In contrast to mountain beech, some small-leaved shrub species may have been competitively advantaged by intensive browsing from sika deer. This is contra to a current view that small-leaved shrub species with interlacing branches were able to tolerate browsing from extinct ratite birds, but not introduced deer. Sika deer have been introduced into countries where other deer species are indigenous, such as Canada, Denmark, Great Britain, Czech Republic, Ireland and the United States of America. Because of their dietary advantage, sika deer may have a greater potential to impede forest regeneration and competitively exclude larger deer species, particularly at low basal area sites where impacts on tree regeneration are likely to be greatest.     

Relationship between a high density of sika deer and productivity of the short-grass (<Emphasis Type="Italic">Zoysia japonica</Emphasis>) community: a case study on Kinkazan Island,northern Japan

An extremely high-density (ca. 800 deer km^–2) wild sika deer population uses a short-grass community dominated by Zoysia japonica on Kinkazan Island in northeastern Japan. To explain why the density of wild deer is quite high on the Zoysia community, (1) we quantified the seasonal productivity of the Zoysia community, (2) we compared food availabilities among the plant communities, and (3) we described the habitat selection by the deer in different seasons. Food availability was greater on the Zoysia community than in the forest understory from spring to fall. The productivity of the Zoysia community was high enough to support the actual high density of the deer (814 deer km^–2) in summer. However, the productivity markedly decreased in winter, when the deer density decreased to less than half (358 deer km^–2) of the summer value. In contrast, the deer density of the adjacent forests was highest in winter (154 deer km^–2) and lowest in spring (19 deer km^–2). These results suggest that the deer using the Zoysia community in summer left and were absorbed into the adjacent forest in winter. If such an adjacent community were absent, many deer would not survive, and consequently the deer density on the Zoysia community in summer would not be so high. This intercommunity movement is particularly important for the deer using a plant community like the Zoysia community, which is highly productive but has a small standing biomass.     

Effects of introduced ungulates on forest understory communities in northern Patagonia are modified by timing and severity of stand mortality

Natural disturbances such as fires, windstorms, floods, and herbivory often act on plant communities, affecting their structure and the abundance and composition of their species. Most research has focused on the effects of single disturbances on plant communities whereas the synergistic effects of several disturbances have received less attention. In this study, we evaluated how timing and severity of tree mortality modified plant use by introduced deer and early post-mortality successional trajectories in northern Patagonian conifer forests. We sampled understory composition and deer use in Austrocedrus chilensis (ciprés de la cordillera) forest stands undergoing varying timing and severity of forest mortality as reconstructed using dendroecological techniques. In addition, we evaluated the effect of fallen logs on plant composition and deer use of plants by monitoring areas of massive dieback where fallen logs had been removed for fire hazard reduction, and nearby control areas not subjected to such removal. Stepwise regression analyses showed that history and severity of tree mortality strongly influence plant composition and deer use of plants. For deer use (with pellet counts and browsing index as response variables), results showed a positive relationship with degree of stand mortality and a negative relationship with cover of fallen logs. Similarly, cover of unpalatable shrub species was explained by canopy mortality history, whereas cover of palatable shrub species was positively associated with severity of canopy mortality. In areas where fallen logs had been removed, pellet counts were six times higher than those in control areas. Though total shrub species cover was similar between log removal and control areas, proportion of unpalatable shrubs increased in areas where fallen logs had been removed. In conclusion, deer use of plants was strongly limited by tall fallen logs, allowing palatable species to establish and grow. Fallen log removal accelerated deer entrance and changed understory composition toward more browse-resistant and unpalatable species. These results underscore the importance of considering the dynamics (timing, severity, and extent) of fallen woody debris influencing understory herbivory and post-disturbance succession. In addition, experimental results underpin the importance of maintaining snags and large woody debris in disturbed landscapes where salvage logging is a routine procedure.     

Nitrogen leaching from surface soil in a temperate mixed forest subject to intensive deer grazing

We aimed to determine the grazing impact on soil nitrogen (N) mineralization and N leaching in a temperate mixed forest on Mt. Ohdaigahara, central Japan, where Sika deer (Cervus nippon Temminck; hereafter deer) grazing has decreased biomass of Sasa nipponica Makino et Shibata (hereafter sasa) that dominates the forest understory. Soil N mineralization and N leaching of the top 0.3-m layer were measured in situ from 2006 to 2007 by an ion-exchange resin core method inside and outside a deer exclosure. Deer grazing decreased the carbon to nitrogen (C:N) ratio of sasa litter because of the declining dead culm C:N ratio and the increasing ratio of leaves with a lower C:N ratio than culms in the aboveground biomass. Grazing increased N mineralization and nitrification rates as well as annual N (ammonium-N and nitrate-N) and nitrate-N leaching. In contrast, deer grazing did not increase the total soil C and N content. The positive effect of grazing on the N mineralization rate may have resulted from a qualitative change in sasa litter due to grazing. The higher annual N leaching resulting from deer grazing may have been related to the facilitated N mineralization rate and decreased N uptake in plants, e.g., sasa with less aboveground biomass due to grazing.     

Consequences of forest fragmentation in an understory plant community: extensive range expansion of native dwarf bamboo

Understory bamboo species are important and influential components of temperate forests in at least several parts of the world. Here we report a study testing the effect of forest fragmentation on the dynamics of the dwarf bamboo Sasa chartacea and on forest herb communities in the Tokachi plain of Hokkaido, Japan. We studied 16 forest fragments of different sizes and small plots established in these fragments to examine the relationship between the abundance of S. chartacea, landscape and environmental conditions, and forest herb communities. Sasa chartacea was more abundant near forest edges and in smaller fragments, suggesting that the species has expanded its local range and increased its abundance in response to forest fragmentation. Edge‐related changes in light and soil moisture might have facilitated this range expansion. The species richness of forest herbs was strongly negatively related to the density of S. chartacea. Because much larger variation in species richness was explained by S. chartacea density than distance to the nearest forest edge, the expansion of S. chartacea has likely excluded other understory species by competition. In addition, the density of S. chartacea significantly explained variation in the species composition of forest herbs across plots. Taken together, our results emphasize the key roles of dwarf bamboos in changing plant communities following forest fragmentation.     

Resistance of Island Rainforest to Invasion by Alien Plants: Influence of Microhabitat and Herbivory on Seedling Performance

Experiments have promise in determining mechanisms by which communities resist invasion. Growth and survivorship of transplanted seedlings of introduced tree species (Leucaena leucocephala, Muntingia calabura, Adenanthera pavonia, and Clausena excavata) were used to assess abiotic (light regime) and biotic resistance (herbivory) to invasion of rainforest on Christmas Island (Indian Ocean). At four sites, seedlings were transplanted into the forest edge along roadside verges and into adjacent intact forest; half were caged to prevent access by the dominant seedling consumer, the red land crab (Gecarcoidea natalis). Red crab densities did not differ between roadside and forest plots. Red crabs initially reduced survivorship of Leucaena in both edge and interior plots but virtually all seedlings in the forest interior were dead after 41 weeks. Survivorship of Muntingia was also initially reduced by crabs in the forest edge, but again, all but one seedling died by the end of the experiment. Seedlings of Adenanthera and Clausena fared much better overall, surviving well in both locations. Red crabs had no overall effect on Adenanthera survival but significantly reduced survival of Clausena in forest plots. For both species, seedling performance was greater in the forest edge than in the forest interior. Red crabs had no effect on height increment for either species; however, for Clausena, red crabs reduced seedling mass in the forest interior. Both Adenanthera and Clausena were able to persist in the intact forest. Clausena is now actively invading intact rainforest, but Adenanthera appears dispersal-limited. Resistance factors in intact forest appear hierarchical: biotic resistance afforded by land crabs can impede establishment of some plant invaders but seedling responses to abiotic factors (e.g., the light regime) largely overwhelm its effect. Together, these two community attributes are likely to restrict the range of plant invaders to a small suite of species that can successfully establish in intact rainforest on the island. However, increased propagule pressure from a variety of shade-tolerant species and further declines in the abundance of the dominant seedling consumer may lead to increasing invasion success in this island rainforest. This revised version was published online in July 2006 with corrections to the Cover Date.