			Home About us Contact

Northeastern Japan (northeastern + japan)

Distribution by Scientific Domains

Humanities and Social Sciences	50%

Selected Abstracts

Reciprocal distribution of two congeneric trees, Betula platyphylla var. japonica and Betula maximowicziana, in a landscape dominated by anthropogenic disturbances in northeastern Japan

JOURNAL OF BIOGEOGRAPHY, Issue 12 2005
Katsuhiro Osumi
Abstract Aim, Information has been compiled on disturbance regimes and the life-history characteristics of Betula platyphylla var. japonica (Miq.) Hara and B. maximowicziana Regel to investigate the impact of humans on the present distribution patterns of these two congeneric tree species. Location, The study area is in the central region of the northern Kitakami Mountain Range, located in the northeast of Honshu Island, Japan. Methods, First, the present distributions of B. maximowicziana and B. platyphylla var. japonica were mapped at the landscape scale. To examine the factors affecting the distribution patterns, topographic features and past land use were taken into account. Second, life-history traits of both species were clarified at various growth stages either by fieldwork or through a literature search. Previous studies have provided some information on seed production, seed dispersal, seedling dynamics, sprouting, and growth. In the present study, field observations and experiments were conducted regarding seed-bank formation, size and age at reproduction, and the life span of canopy trees. Results,Betula platyphylla var. japonica and B. maximowicziana were spatially segregated in the studied landscape (14,000 ha). The distribution of each species was correlated more strongly with land use at the beginning of the twentieth century than with site environmental factors such as altitude or slope angle. Betula platyphylla var. japonica was distributed more frequently on former grasslands, whereas B. maximowicziana was almost exclusively limited to past old-growth forests. As typical pioneers, the two species showed similar life-history traits but differed in several critical points. Betula platyphylla var. japonica has a vigorous sprouting ability, which might increase its resistance to burning and logging, whereas B. maximowicziana forms a persistent seed bank in the soil, indicating an advantage in regenerating in disturbances found in forest communities. Other critical differences were detected in age-related characteristics such as minimum age of reproduction and life span. Main conclusions, The earlier reproductive maturity and the shorter life span of B. platyphylla var. japonica indicate a shorter population cycle than that for B. maximowicziana. The latter would be excluded from grasslands that were burned frequently, as a result of the longer time span before initial reproduction and its poor sprouting ability. In contrast, B. platyphylla var. japonica would be excluded from old-growth forests, where disturbance was infrequent, owing to its shorter life span and lack of a persistent seed bank. [source]

Involutions resulting from annual freeze,thaw cycles: a laboratory simulation based on observations in northeastern Japan

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 4 2007
Yoshiko Ogino
Abstract A pilot laboratory experiment using a reversed two-layer soil model simulated small-scale involutions formed in a seasonal frost environment during the last glacial period. At the modelled site, the interface between the upper aeolian sandy loam and the lower volcanic pumice constitutes small-scale involutions that display upward-extending tapered projections and downward-extending round hollows. Two scale-reduced laboratory models were subjected to three accelerated annual freeze,thaw cycles with monitoring of frost heave, soil temperature, moisture and pressure. Ice segregation near the layer interface induces upheaving of coarse pumice grains on freezing and earlier settlement of mobilised loam on thawing, resulting in deformation of the interface. A reconstructed 3-D interface displays mounds and depressions with a diameter of 15,20,cm and a height increasing with freeze, thaw alternations. The experimental results imply that the repetition of differential heave and soft-loam settlement promotes decimetre-scale involutions in near-saturated soils subject to deep seasonal frost penetration. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Food/nutrient intake and risk of atrophic gastritis among the Helicobacter pylori -infected population of northeastern Japan

CANCER SCIENCE, Issue 4 2003
Ai Montani
Although Helicobacter pylori (H. pylori) infection is considered a key risk factor for atrophic gastritis, along with other environmental factors, it is still unclear which factor is involved in the development of atrophic gastritis among H. pylori -infected subjects. In the present cross-sectional study, therefore, we analyzed various dietary factors in relation to the presence of atrophic gastritis among H. pylori -infected subjects who participated in a health check-up program in a town in northeastern Japan. One thousand and seventy-one subjects (362 males and 709 females) who provided both self-administered validated food frequency questionnaires and blood samples were the basis for the study, and all of them were serologically positive for H. pylori immunoglobulin G (IgG) antibody. Among them, 663 (223 males and 440 females) were diagnosed as having atrophic gastritis on the basis of serum pepsinogen levels. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated based on tertile categories of subjects without atrophic gastritis, using logistic regression analysis. Among females, high consumptions of rice (OR=1.6, 95% CI: 1.1,2.3), cod roe (OR=1.5, 95% CI: 1.0,2.2) and cuttlefish (OR=1.5, 95% CI: 1.0,2.3) were associated with a moderately increased risk of atrophic gastritis after adjustment for age (P for trend=0.02 for these items). Among males, high consumptions of rice and miso soup showed a tendency toward an increased risk (P for trend=0.12 and 0.13, respectively). Vegetables and fruits showed no association among either males or females. From these results, it is suggested that the dietary habits of consumers of traditional Japanese foods may play a role in the development of atrophic gastritis after H. pylori infection. (Cancer Sci 2003; 94: 372,377) [source]