Hiroaki Ishida

Salvia is a taxonomically challenging genus in the Japanese archipelago, comprising 12 distinct species, eight of which are endemic. In this study, the nutlet micromorphology of 19 taxa (species and varieties) assigned to the sections Glutinaria , Heterosphace , Notiosphace , and Sobiso was investigated using light and scanning electron microscopy. This study aimed to evaluate the systematic significance of nutlet morphology in Japanese Salvia . Nutlet size ranged from 0.64 × 0.45 mm in S. plebeia (sect. Notiosphace ) to 3.27 × 2.27 mm in S. koyamae (sect. Glutinaria ). The L/W ratio varied from 1.06 in S. glabrescens var. repens (sect. Glutinaria ) to 2.54 in S. pygmaea var. pygmaea (sect. Sobiso ). Nutlet shapes were elliptic, narrow-elliptic, and ellipsoidal in sect. Sobiso ; ovoid to obovoid and spherical in sect. Glutinaria ; and ovoid in both sect. Heterosphace and sect. Notiosphace . Abscission scar morphology varied among the sections, being squarish, triangular, irregular, or orbicular in sect. Sobiso ; irregular to orbicular in sect. Glutinaria ; orbicular in sect. Heterosphace ; and triangular in sect. Notiosphace . Four major types of surface sculpturing were recognized: colliculate with irregular surface cells in sect. Glutinaria ; reticulate with pentagonal to hexagonal cells in sect. Sobiso ; tuberculate with large rounded knobs in sect. Heterosphace ; and verrucate with small wart-like projections in sect. Notiosphace . Principal component analysis (PCA) based on taxon means demonstrated that nutlet size-related characters contributed most strongly to the observed variation among the studied taxa. Overall, the diversity of nutlet morphology highlights the diagnostic value of these characters for taxonomic identification at both the species and sectional levels within Japanese Salvia .

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.