Hiroaki Ishida

Taxillus yadoriki （Loranthaceae） is a hemiparasitic plant species that attaches to the stems and branches of trees. There are many host trees of T. yadoriki in a park in Miyazaki City, Miyazaki Prefecture. In this park, we surveyed the species, size, and degree of debilitation of these host trees and the foliar cover of T. yadoriki in order to examine the host specificity of T. yadoriki and the effects of its parasitism on trees. In addition, we resurveyed the degree of debilitation after 4 to 5 years. A total of 422 host trees from 27 species were observed in the park. This study and a literature survey revealed that there were at least 67 species （29 families） of the host trees of T. yadoriki in Japan. Lithocarpus edulis was the most common host tree, comprising 62.9% of all host trees. The frequency that L. edulis trees were infected by T. yadoriki was higher in taller trees and canopy trees. An analysis of host specificity using Jacob's selectivity index suggested that T. yadoriki had a preference for the tree species L. edulis, Quercus serrata, Cryptomeria japonica, and Eurya japonica var. japonica. The degree of debilitation of the host trees was graded on a scale of one to five. Most host trees （86.7%） were debilitated, and the debilitation grade for L. edulis had a highly positive correlation with the foliar cover of T. yadoriki. Therefore, it was determined that T. yadoriki induced the tree debilitation. A resurvey indicated that T. yadoriki killed host trees and that L. edulis was susceptible to death by parasitism.

<p>Ailanthus altissima, a deciduous tree native to China, is known to invade open and disturbed sites and has been naturalized in many regions of Japan. I examined the species composition and stand structure of A. altissima community established at deforested sites under severe feeding pressure by sika deer （Cervus nippon） in the northern part of Hyogo Prefecture, Japan. These deforested sites were formed by clear^-cutting secondary oak forests and artificial Japanese cedar forests. Many A. altissima individuals of ≥1.5 m in height were found at the deforested sites, but none was found at neighboring sites covered by secondary oak forests and artificial Japanese cedar forests. Many native plant species, but not A. altissima, were browsed on by sika deer, indicating that A. altissima is unpalatable to sika deer. Native pioneer tree species （e.g., Mallotus japonicus and Aralia elata） that are strong competitors of A. altissima showed very low dominance in the A. altissima community.</p><p>This was the case in the community with low dominance of A. altissima, established at the deforested sites.</p><p>These findings suggest that browsing on native plant species by deer greatly contributed to the establishment of the A. altissima community. The height class distribution of A. altissima individuals of ≥1 m in height was unimodal in the A. altissima community, indicating that the regeneration of this species is discontinuous. However, 2880 A. altissima individuals per hectare （<1 m in height） were found in the understory of the community, most of which were ramets that originated from roots. The establishment of such a ramet bank may contribute to the regeneration of the A. altissima community to some extent. The maximum height of A. altissima trees was 15 m; the relationship between height and stem diameter at breast height for A. altissima showed that the height of the species has still not peaked in the study area. Thus, the A. altissima community is likely to continue growing and existing for more than a century.</p>

Natural beech (Fagus crenata) forests in Japan have been rapidly fragmented because of human activities since the end of the Second World War. In order to examine the effects of forest fragmentation on the species richness and composition of such forests, we surveyed the species of forest interior flora and the habitat conditions of 20 natural beech forest patches of various areas (450-856300 m^2) on Mt. Ouginosen, Japan, and analyzed the relationship between species richness or species composition and patch area on a whole-patch scale. A high positive correlation between the number of species and patch area was observed for all species, tree species, shrub species, terrestrial herb species, terrestrial pteridophyte species, endangered species (ES), rare species (RS), and species showing a preference for habitats with moist soil conditions (MS). Analysis of the relationship between the distribution of each species and patch area showed that many species, particularly ES, RS, and MS, tended to be absent in smaller patches. In addition, the first-axis score of a detrended correspondence analysis ordination for the patches was highly correlated with patch area. These results indicate that forest fragmentation has a considerable negative impact on species richness and can simplify species composition to a considerable extent. The absence of ES, RS, and MS in smaller patches may be attributable to certain factors associated with the decrease in patch area, such as a decreased likelihood of occurrence, an increased risk of extinction due to the decrease in population size, and the lack of landforms with moist soil conditions.

We examined the following three types of semi-natural grasslands established on the levee slopes of paddy fields in Northern Hyogo Prefecture, Japan: (1) traditional grassland (TG), i.e., grasslands managed on traditional paddy fields (paddy terraces); (2) abandoned traditional grassland (AG); and (3) non-traditional grassland (NTG), i.e., grasslands restored after consolidation of paddy terraces. In this study, the vegetation structure, dominant species, species composition, and species richness were compared among the three grassland types. Vegetation height was much higher in AG than in TG and NTG. The dominant species was Imperata cylindrica var. koenigii in TG and NTG, and Miscanthus sinensis in AG. The species composition of TG clearly differed from that of the other two types: many species found in TG were absent or rare in both AG and NTG. The number of native plant species per plot was the highest in TG, followed by NTG and AG. Species richness of alien plants was very low in not only TG but also NTG. Recovery of species composition and species richness after paddy consolidation tended to be faster for annual herbs than for perennial herbs. To examine the soil seed bank of AG, we conducted germination tests for soil samples taken from AG using the seedling emergence method. Of the 48 species found in TG, but absent or rare in AG, 17 species germinated from seeds buried in the soil of AG. This result suggests that the soil seed bank of AG could not play a significant role in the restoration of TG.

We examined the effects of cutting and agricultural land reclamation on species diversity, species composition, and cover of pteridophytes. For this purpose, we compared natural evergreen broad-leaved forests with secondary deciduous broad-leaved forests established on post-agricultural sites in south Yunnan, China. The results showed that pteridophyte species diversity in secondary forests was similar to that in natural forests even considering the ecological traits of pteridophytes. Meanwhile, there remained slight differences in pteridophyte species composition: secondary forests were characterized mainly by the persistence of non-forest terrestrial species, whereas natural forests were characterized by the luxuriance of forest epiphytic species. In addition, the cover of non-forest terrestrial species was higher in secondary forests, whereas the covers of forest terrestrial species and forest epiphytic species were higher in natural forests. These findings suggest that although the study sites have a high potential for facilitating pteridophyte re-establishment, expansion of human interference should be avoided for ensuring the conservation of pteridophytes.

Secondary lucidophyllous (evergreen broad-leaved) forests with different population densities of sika deer (Cervus nippon yakushimae) were investigated in lowland areas of Yakushima Island, Japan, to clarify the effects of deer feeding pressure on such forests and to evaluate the naturalness of these forests. The vegetation structure, species composition, and species richness of secondary forests with a low population density of deer (deer-scarce forests) were compared with those of the secondary forests with a high deer density (deer-abundant forests). The vegetation cover of the ground layer (approximately 2 m high) was significantly lower in the deer-abundant forests than in the deer-scarce forests. The species composition of the ground layer greatly differed between the deer-scarce and the deer-abundant forests; many species occurred less frequently in the latter. These findings indicate that deer feeding pressure can simplify the species composition in secondary lucidophyllous forests to a considerable extent. The ground-layer species richness (number of the component species of lucidophyllous forest per 100 m^2) was significantly lower in the deer-abundant forests than in the deer-scarce forests, and it was negatively correlated with deer density. Many species consisting of primeval lucidophyllous forests with a low population density of deer were found to be absent or rare in the deer-scarce forests. In addition, the species richness of the deer-scarce forests was much lower than that of the primeval forests. On the basis of these results, it was concluded that the naturalness of the secondary lucidophyllous forests in lowland areas of Yakushima Island is very poor, and that deer feeding pressure has a great negative impact on forest naturalness.

Sapium sebiferum, an alien tree species that originated in China, has been naturalized in many areas of Japan. We examined the ecological characteristics of S. sebiferum community and the causal factors for its establishment at deforested sites, which were formed by clear-cutting the Quercus phillyraeoides community, on the Awaji Island in Japan. We recorded the locations of escaped S. sebiferum individuals of &ge;1-m height in a 4-ha sampling area; 1118 individuals were found at the deforested sites, but none were found at the neighboring sites covered by the Q. phillyraeoides community. The S. sebiferum community mostly developed within 100 m of mature S. sebiferum individuals that were planted as ornamental roadside trees. Major component species of the Q. phillyraeoides community (e.g., Q. phillyraeoides and Q. serrata) and native pioneer tree species (e.g., Mallotus japonicus and Aralia elata), which are strong competitors of S. sebiferum, were rare or absent at the deforested sites because of browsing by sika deer. This suggests that browsing on native plant species by sika deer, clear-cutting of the Q. phillyraeoides community, and the presence of seed sources of S. sebiferum in the vicinity of the deforested sites greatly contributed to the establishment of the S. sebiferum community. The S. sebiferum community was similar to the Q. phillyraeoides community with regard to soil depth, although soil erosion was clearly caused by sika deer in areas of bare ground at the deforested sites. The native plant species were much more abundant in the S. sebiferum community than in the native plant communities established at the deforested sites. The maximal height of escaped S. sebiferum individuals was 7.6 m, whereas that of planted S. sebiferum individuals was 19.0 m. For escaped S. sebiferum individuals, the height highly correlated with the stem diameter at breast height and the height growth rate did not show a decreasing trend. Thus, the S. sebiferum community is likely to continue growing and exist for a long period. This may pose various problems for the conservation of indigenous ecosystems.

Seed germination traits and seed storage techniques for the threatened plant species Chikusichloa aquatica Koidz. (Poaceae) were assessed to facilitate the planning of conservation strategies for this species. Germination tests based on a gradually increasing and decreasing temperature method indicated the following seed dormancy and germination characteristics: (1) a 2-3 week moist-chilling treatment was necessary to break dormancy; (2) higher temperatures induced secondary dormancy; and (3) the lower temperature limit for seed germination was approximately 20℃. These thermal-germination characteristics suggest that the seeds of this species are dispersed in autumn, their dormancy is broken during winter, and germination occurs the following spring. Tests performed using seeds stored under different moisture conditions indicated that a submerged-chilling treatment implemented for several months did not adversely affect the viability and germination of the seeds. The results of germination tests performed under different water-depth conditions showed that submerging the seeds a few centimeters under water did not restrict seed germination. These traits related to moisture and water-depth conditions are likely to be advantageous for establishment success in frequently inundated wetlands. Tests performed using seeds maintained under different storage conditions indicated that when a vacuum-packaging treatment was used, most seeds retained their viability for at least 3 years, suggesting that seed storage using vacuum packaging is helpful for the conservation of this species.

Changes in species richness and species composition due to grazing by sika deer were examined in warm-temperate deciduous broad-leaved secondary forests in southeastern Hyogo Prefecture and northwestern Osaka Prefecture. The vegetation structure, species richness, and species composition of stands with apparent signs of deer grazing (grazed stands) were compared with those of ungrazed stands. The vegetation cover of the shrub layer (approximately 2m in height) and herb layer was lower in grazed stands than in ungrazed stands. A similar trend was observed for the number of deciduous plant species per 100m^2, even when deciduous plants were classified into four life forms (trees, shrubs, herbs, and climbers). Differences in the species richness of deciduous plants between ungrazed and grazed stands were larger for the shrub layer than for the herb layer, suggesting that the negative effect of deer grazing on species richness is greater in the shrub layer than in the herb layer. The species composition of the shrub and herb layers greatly differed between ungrazed and grazed stands; many species had lower frequencies of occurrence in grazed stands, whereas Illicium religiosum exhibited the opposite trend. Based on these results, we concluded that deer grazing considerably simplified the species composition of warm-temperate secondary deciduous broad-leaved forests.

Pteridophyte communities established on levees modified by slope protection using iron cage frames in Heiwadai Park, Miyazaki City, were surveyed to understand the habitat conditions suitable for pteridophytes. In this study, 2 types of levees were compared: levees with cage frames and those without slope protection materials. The number of pteridophyte species and the coverage of pteridophytes were higher on the levees with cage frames than on those without slope protection materials. The occurrence frequency for many pteridophyte species was also higher on the levees with cage frames than on those without slope protection materials. The species composition of the levees with cage frames was characterized by a higher proportion of pteridophytes and a lower proportion of seed plants. The number of pteridophyte species per unit area was also higher on these levees than in the surrounding lucidophyllous forests. Although epiphytic pteridophytes were rarely found on the levees with cage frames, these results indicate that the levees with cage frames function as suitable habitats for terrestrial pteridophytes. The possible factors that promote the development of pteridophyte communities on levees with cage frames are vertical soil surfaces and soil stability.

The lucidophyllous forests on Mt. Ichibusayama (Kumamoto Pref.), Kawanaka (Miyazaki Pref.), Mt. Omoridake (Miyazaki Pref.), Mt. Kurinodake (Kagoshima Pref.) and Shiratani (Yakushima Island, Kagoshima Pref.), were studied in order to clarify the species composition of the vascular epiphytes of the lucidophyllous forest and the relationship between host tree size at breast height (DBH) and species richness of the vascular epiphytes (epiphytic richness) on each host tree. In these forests, a total of 586 host trees (45 species), including 84 Distylium racemosum, 66 Persea thunbergii, 60 Quercus acuta, and 376 others were chosen as sample trees. The vascular epiphytes on the host trees comprised 37 species, including Lemmaphyllum microphyllum, Bulbophyllum drymoglossum, and Davallia mariesii. The common characteristic of the vascular epiphytes flora of the lucidophyllous forest in Japan was the dominance of ferns and orchids. The species composition of the vascular epiphytes was compared among five localities. The vascular epiphytes were assorted into 8 species groups according to the summarized table of the frequency (%) of occurrence and mean coverage (%) of each species. The species composition of the vascular epiphytes in five localities was characterized by the combination of the species groups, respectively, and each locality had a different species combination. The species composition of Mt. Kurinodake was similar to that of Mt. Ichibusayama. The species composition of Kawanaka and Shiratani was different from each other. The ordination obtained by Detrended correspondence analysis (DCA) revealed that three groups (Kawanaka, Omoridake-Mt. Ichibusayama-Mt. Kurinodake and Shiratani) of host trees (stands) were clearly different from each other. The difference of species composition among the five localities was due to the climatic conditions of the localities. The species richness of the vascular epiphytes on each host tree in five localities or in seven host tree species had a high positive correlation with host tree DBH (cm), respectively. This relationship in five localities or in seven host tree species was expressed by the equation: y=ax+b (where y is the number of vascular epiphytes, x is the DBH (cm) of the host tree, and a and b are the constants). The constants of the five localities or seven host tree species are different, respectively, due to the precipitation and humidity of the localities or the properties of the host tree bark.

Stand structure and dynamics of Betula alnoides forests in the Caiyanghe Nature Reserve located in Yunnan Province, China, were studied. These were secondary forests distributed over the subtropical zone; they were established after human activities led to the destruction of evergreen broad-leaved forests. A total of 10 plots were established in stands that were aged 10-40 years and were at different stages of development i.e., from young, small-sized stands to fairly mature stands. The height and DBH (diameter at breast height) of stems≧3cm in DBH were recorded. The number of stems per hectare of B. alnoides showed a strong negative correlation with the maximum DBH of the species. Juveniles (<3cm in DBH) of B. alnoides were not found in any of the stands. DBH- and height-class distributions of the mature stands showed that regeneration of B. alnoides was discontinuous. More than 89.7% of B. alnoides stems found in the mature stands were canopy trees. On the basis of these results, it was concluded that B. alnoides is a typical shade-intolerant pioneer species that regenerates in sites with ample sunlight. In addition, the present study suggested that B. alnoides grows to a height of 25m and 40m within 20 years and 40 years, respectively.

Invasion of the natural habitat of fragmented, secondary deciduous oak forests by greening/garden trees is frequently observed in urban areas of Japan. We investigated the flora of the invading greening/garden trees in such urban forests in the Hyogo, Osaka, and Saitama prefectures. There were more than 30 species of the invading trees in every region, and a total of 60 species were detected for all the regions. More than 70% of the invading species were bird-dispersed species, suggesting that the invasion of the forests by greening/garden trees is mainly caused by avian seed dispersal. The invading trees comprised many native species, and the number of these native species was approximately twice that of the invading alien species. The number of invading species correlated highly and positively with the area of the forest, regardless of the region. However, the species composition of the invading trees, expressed by sample scores obtained using detrended correspondence analysis, showed no significant relationship with the forest area in every region. In the Hyogo prefecture, most invading trees of 5 bird-dispersed species were found in forests that were located within a 200-m radius of the planted trees of the same species. This suggests that the extent of invasion of the forests by these species greatly depends on the distance from their seed source. Based on these results, we proposed certain measures to prevent greening/garden trees from invading and reproducing in the secondary deciduous oak forests.

In areas with high sika deer density the loss of regenerated vegetation at previously deforested sites, due to herbivory, is a serious problem. However, there are plant species with anti-herbivory strategies, such as Hypolepis punctata, that form a relatively large community at deforested sites under severe feeding pressure by sika deer. This suggests that planting H. punctata may be effective in improving the revegetation of such places. In order to evaluate the effectiveness of revegetation using H. punctata, we investigated stands of the H. punctata community and areas of bare ground at deforested sites in the southern part of Awaji Island in Hyogo Prefecture, Japan. We also investigated secondary forests in the vicinity of the deforested sites. The stands of the H. punctata community were similar to the secondary forests with regards to soil depth and soil chemistry. Soil erosion was clearly observed at the bare ground sites. The number of forest species per 25m^2 was higher in the stands of the H. punctata community than in the secondary forests. Comparison of species composition between the three types of site showed that most species found in the secondary forests were also present in the stands of the H. punctata community. These results suggest that the H. punctata community has a high capacity to reduce erosion and maintain forest species richness. Thus, we concluded that H. punctata is a useful species for the revegetation of deforested sites that are under severe feeding pressure by sika deer.

The spatial distribution, population structure, habitat condition, and seed production of Fagus crenata and Fagus japonica, which are the dominant species of beech (Fagus crenata) forests, were investigated. The investigation was carried out on Mt Rokko in the southeastern part of Hyogo Prefecture, and it aimed to clarify the present states of the two species and collect information that can contribute to the restoration of Fagus crenata forests of Mt. Rokko. We identified 130 Fagus crenata and 1151 Fagus japonica individuals in the study area. Both species occurred disproportionately on the northern slope of Mt. Rokko, and their main habitats were steep slopes. Nut-bearing Fagus japonica individuals accounted for approximately 94% of the individuals more than 10 m in height. On the other hand, only a smaller proportion of Fagus crenata produced nuts. Fagus crenata mostly existed as canopy trees, and its saplings and seedlings were rare. Hence, it appeared that the restoration of the Fagus crenata forests of Mt. Rokko would be extremely difficult without human intervention. It was suggested that planting Fagus crenata seedlings is a requisite for restoring the beech forests of Mt. Rokko.

Witches' - broom of bamboo is the most destructive disease in bamboo in Japan, and its causative agent is Aciculosporium take MIYAKE (Cavicipitaceae) . We investigated the influence of the witches' - broom of bamboo on the structure, species composition, and species richness of bamboo forests, particularly in the Phyllostachys bambusoides and P. pubescens forests. We found that most of the P. bambusoides forests were affected by this disease, and more than 50% of their patch areas were covered with dead culms in a quarter of the investigation spots. On the other hand, the P. pubescens forests were completely unaffected by the disease. The species composition in the diseased bamboo forests was more diverse than that of the healthy bamboo forests, and the species richness of the former was higher than that of the latter. We suggest that the disease had a negative impact on the structure of the P. bambusoides forests and a positive impact on its species composition and species richness. Further, it had an unusual influence on the P. pubescens forests.