Outstanding performance of an invasive alien tree Bischofia javanica relative to native tree species and implications for management of insular primary forests.

Invasive alien tree species can exert severe impacts, especially in insular biodiversity hotspots, but have been inadequately studied. Knowledge of the life history and population trends of an invasive alien tree species is essential for appropriate ecosystem management. The invasive tree Bischofia javanica has overwhelmed native trees on Haha-jima Island in the Ogasawara Islands, Japan. We explored forest community dynamics 2 years after a typhoon damaged the Sekimon primary forests on Haha-jima Island, and predicted the rate of population increase of B. javanica using a logistic model from forest dynamics data for 19 years. During the 2 years after the typhoon, only B. javanica increased in population size, whereas populations of native tree species decreased. Stem diameter growth of B. javanica was more rapid than that of other tree species, including native pioneer trees. Among the understory stems below canopy trees of other species, B. javanica grew most rapidly and B. javanica canopy trees decreased growth of the dominant native Ardisia sieboldii. These competitive advantages were indicated to be the main mechanism by which B. javanica replaces native trees. The logistic model predicted that B. javanica would reach 30% of the total basal area between 2017 (in the eastern plot adjacent to a former B. javanica plantation) and 2057 (in the western plot distant from the plantation site), which is a maximum percentage allowing to eradicate under the present guideline of the National Forest. The results suggest immediate removal of B. javanica is required to preserve native biodiversity in these forests.

Plant species diversity, community structure and invasion status in insular primary forests on the Sekimon uplifted limestone (Ogasawara Islands).

Native forests on oceanic islands are among the most threatened ecosystems. The forests formed on Sekimon uplifted limestone in Haha-jima Island (Ogasawara Islands) have not yet been destroyed by human activities and remain as primary forests harboring several narrow endemic endangered plants. In this paper, we described the plant species diversity, community structure, and status of invasion by alien plants in the mesic forests of Sekimon. The Sekimon forest was characterized by low tree diversity (37 species), high stem density (1731 ha-1), and high basal area (63.9 m2 ha-1), comparing with natural forests in world islands. The forests were dominated in the number of stems by the sub-tree Ardisia sieboldii followed by the trees Pisonia umbellifera and Elaeocarpus photiniifolius. The invasive tree Bischofia javanica ranked fourth for basal area and third for the number of stems (DBH ≥ 10 cm), and its distribution expanded, especially near a past plantation site. Surveys of forest floor vegetation revealed that species richness of vascular plants was 109 species and that many alien plants had already invaded the forests. Despite the low species richness of alien (16% for vascular flora and 8% for trees), the high frequency of aliens on the forest floor suggests that they have colonized successfully in the Sekimon forest. Extrapolation analysis based on the rarefaction curves predicted that the vascular plants in the Sekimon (25 ha) accounted for 135 species (29.9% of the vascular flora of the Ogasawara Islands) and endemic plants were 85 species (62.0%). The fact that the 39 vascular species recorded in our plots were listed in Japanese Red List suggests that the Sekimon forest should be conserved as a sanctuary of biodiversity. Because alien plants are invading the forests without apparent anthropogenic disturbance, immediate action to eradicate these invaders is highly needed.

Clinical and immunological assessment of periodontal disease in Japanese leprosy patients.

Periodontitis is a chronic inflammatory disease caused by the infection of periodontopathic bacteria in dental plaque. However, an individual's susceptibility to this disease appears to be associated with multiple genetic factors, as seen in the case of leprosy. In order to gain a better understanding of the pathophysiology of periodontal disease in subjects with leprosy, we investigated the clinical features of periodontitis and the immunological responses against periodontopathic bacteria in 382 subjects with a history of leprosy and 451 age-matched control subjects. The prevalence of periodontitis and the degree of periodontal pocket depth were found to be significantly higher in leprosy patients than in age-matched controls. Furthermore, a comparison of the clinical parameters of lepromatous leprosy (L-lep) and tuberculoid leprosy (T-lep) patients showed that the probing pocket depth of L-lep patients with periodontal disease was significantly higher than that for T-lep patients. In contrast, serum IgG titers against Porphyromonas gingivalis in L-lep patients were significantly lower than in T-lep patients. These results imply that L-lep patients show more severe periodontal disease than T-lep patients or age-matched control subjects, and that low humoral immunity against P. gingivalis might be one of the genetic factors determining periodontal disease susceptibility in leprosy patients.

Study of finite element modeling from CT images.

The use of finite element analysis is becoming more widespread with rapid advancements in computer technology. However, the field of dentistry is not enjoying the spillover benefits of the expanded use of this design simulation and analysis tool. Finite element modeling requires measurement of the object. However, as the living body is morphologically very complex, this requires a great deal of both time and skill using CAD applications, thus preventing its widespread adoption in the dental field. Although there have been reports of finite element modeling from CT images, these methods require skilled programmers for software development--which is another factor that prevents its widespread adoption in dentistry. Therefore, establishing a finite element modeling method that is both accurate and practical will be of great benefit in clinical dentistry. In the present study, a method using computer tomography and existing software was examined for finite element model construction based on computer tomography images. The results suggested that the method developed here is feasible and practical for clinical use.