Frankia communities at revegetating sites in Mt. Ontake, Japan.

In 1984 at Mt. Ontake in Japan, an earthquake caused a devastating landslide, and as a result, the vegetation on the south slope of the mountain was completely eliminated. In higher elevation (2000 m) areas, revegetation has not yet been completed even 30 years after the landslide. Revegetation progress throughout the area was heterogeneous. In the partially revegetated areas, actinorhizal plant species such as Alnus maximowiczii and Alnus matsumurae have been found. In the present study, we investigated the Frankia communities in the higher-elevation area using sequence analysis of the amplified nifH (dinitrogenase reductase) gene from nodule and soil samples collected in the disturbed region, undisturbed forest, and in the boundary between the disturbed region and the undisturbed forest. Phylogenetic analysis of partial nifH sequences revealed the presence of six clusters, each of which consisted of highly similar (> 99%) sequences. Four clusters showed significant sequence similarity to Frankia (three Alnus- and a Casuarina-infecting strains). Diversity in the Frankia community was relatively low-only one or two clusters were detected in a site. At most of the sampling sites, a dominant cluster in a nodule coincided with that in rhizosphere soil, indicating that community structure in the rhizosphere is a primary factor that determines occupancy in a nodule. No significant difference in community structure was observed between plant species. Diversity in the Frankia community varied depending on revegetation progress. Cluster A, which was the most dominant in the disturbed region, was likely to have invaded from undisturbed forest.

Three-rods test as drivers' license vision test from the viewpoint of reproducibility, eye deviation, and functional visual acuity.

BACKGROUND: Three-rods test is required as depth perception vision test to obtain motor vehicle license to drive taxies, buses, and trucks in Japan. Functional visual acuity is measured automatically by successive visual target presentation in a fixed period of time. This study examined three-rods test from the viewpoint of reproducibility, eye deviation, and functional visual acuity to assess the feasibility for drivers' license vision test. METHODS: At three-rods test, a central rod was moved at the speed of 50 mm/sec forward and backward automatically against two fixed rods on both sides inside an illuminated box. An examinee at the distance of 2.5 m observed the rods inside the box from a small window and pushed a button to stop the central rod in alignment with the fixed rods. Erred distance of the central rod from the fixed rods as a mean of 4 measurements was used. At functional visual acuity test, an examinee moved a joystick to the same direction as Landolt-C opening as a visual target which was sequentially presented every 2 seconds for 30 times in 1 minute. RESULTS: The mean erred distance of three-rods test was reproducible between two tests done on separate occasions (n = 44, ρ = 0.679, P < 0.0001, Spearman rank correlation). Exophoria induced by wearing 4-prism-diopter base-out prism did not significantly influence the mean erred distance while vertical diplopia induced by wearing 4-prism-diopter base-up prism disrupted the measurement (n = 9). The mean erred distance of three-rods test was better correlated with functional visual acuity tested with both eyes open than with conventional visual acuity with both eyes open (n = 17, ρ = 0.2 versus ρ = 0.179). CONCLUSION: In the context of the small sample size in the present study, the three-rods test was reproducible, and testable in the presence of phoria, but not testable in diplopia, indicating the feasibility as a depth perception vision test.