Kotaro Yamagata

Characteristics of a crater glacier at Ushkovsky volcano, Kamchatka, Russia, as revealed by the physical properties of ice cores and borehole thermometry

A glacier at the summit of Ushkovsky volcano, Kamchatka peninsula, Russia, was studied in order to obtain information about the physical characteristics of a glacier that fills a volcanic crater. The glacier has a gentle surface and a concave basal profile with a maximum measured depth of 240 m at site K2. The annual accumulation rate was 0.54 m a -1 w.e., and the 10 m depth temperature was -15.8°C. A 211.70 m long ice core drilled at K2 indicates that (1) the site is categorized as a percolation zone, (2) the stress field in the glacier changes at 180 m depth from vertical and longitudinal compression with transversal extension, which is divergent flow, to a shear-dominated stress field, and (3) the frequent occurrence of ash layers can be a good tool for dating the ice core. The borehole temperature profiles were considered to be non-stationary, but the linear profile made it possible to estimate the basal temperature and the geothermal heat flux at K2. Assuming constant surface and the basal boundary conditions, we constructed two depth-age relationships at K2. These predicted that the bottom ages of the ice core were about 511 or 603 years.

LANDFORM DEVELOPMENT ALONG THE MIDDLE COURSE OF THE KUISEB RIVER IN THE NAMIB DESERT, NAMIBIA

The hyperarid to arid Namib Desert extends along the west coast of southern Africa. The Kuiseb River is one of the major ephemeral rivers originating in the interior highland, and crosses the Namib Desert. Fluvial terraces are well developed along the middle reaches of the Kuiseb River near Gobabeb, and are classifi ed into four surfaces: upper (H), middle 1 (M1), middle 2 (M2), and lower (L). Layers of calcrete are founded on the M1 and M2 surfaces, and gypcrete layers are founded on the H surface. Dead tree matter, buried by dune sand on the L surface, dates to 300±60 years BP and 550±50 years BP. The calcareous crusts on the M1 surface date to 5,300±60 years BP and 6,450±50 years BP, and those of the M2 surface date to 22,070±260 years BP. The presence of calcrete suggests that the ground water level was higher when the M1 and M2 surfaces were formed than it is at the present time. Tree size distribution on the L surface demonstrates that the L surface was also formed during a relatively wet period. It may be concluded, therefore, that these fluvial terraces record the humid periods of ca 22 ka, 5-6.5 ka, and 300-600 years BP in the catchment area of the Kuiseb River. The presence of a water-soluble gypsum crust on the H surface suggests that the paleohydrologic environment of these terrace-forming periods probably involved increased rainfall in the interior highland east of the desert.

VEGETATION SUCCESSION AND PLANT USE IN RELATION TO ENVIRONMENTAL CHANGES ALONG THE KUISEB RIVER IN THE NAMIB DESERT

The aim of this study was to clarify the relationship between environmental change and vegetational succession in the Kuiseb River area of the Namib Desert. The results reveal the following: 1. About 5000-7000 years ago, wetter conditions prevailed in the Kuiseb River basin, forming a wider riverbed than at present. 2. About 600 years ago, a low terrace formed. The low terrace was characterized by the growth of acacia trees and other vegetation, which trapped and accreted aeolian sand. 3. About 400 years ago, the trapped and accumulated sand began to form a sand dune, eventually killing the tree population. 4. At the present time, all of the buried acacia trees have died and have been replaced by salvadora bushes, which continue to trap sand and increase the size of the dune. 5. Plants such as Acacia erioloba, Faidherbia albida, and Acanthosicyos horridus are very important food sources and shade plants for the local Topnaar people and their livestock. The succession of vegetation in response to environmental change has a profound impact on life in the Kuiseb River area, owing to the harsh environmental conditions and scarce plant life in the region.

The Great East Japan Disaster and Geography Education: School Damage, Associations’ Support Project, and Trends in Geography Teaching Practices

The Great East Japan Disaster that struck on 11 March 2011 had a massive and wide-ranging impact on all aspects of life. It directly affected schools in the area and indirectly impacted geography associations, education policy, and geography education. This chapter provides a brief explanation of the multifaceted disaster and its aftermath, including earthquakes, tsunamis and the nuclear power plant accident. The authors’ visits to and investigations of affected schools found that needs to support geography teaching post-disaster were dependent on the disaster(s) that struck, school locations, and level of destruction. To respond to these needs, the Association of Japanese Geographers in conjunction with other associations conducted emergency fundraising. At the government level, the disaster prompted discussions on natural hazards prevention education, as demanded by policy makers at the national level. Geography education is considered one of the main subjects of the disaster prevention curriculum. As a result of public demand, disaster prevention practices have notably improved since the event. For example, in the immediate days after the disaster, many lessons were given about its occurrence and processes, along with preventative education to foster students’ knowledge and skills for surviving future natural hazards. Recently, thanks to interest generated by these lessons, geography classes have been increasingly concerned with best methods to restore devastated areas and to create a Japanese society resistant to disasters.

Nitrogen acquisition, net production and allometry of Alnus fruticosa at a young moraine in Koryto Glacier Valley, Kamchatka, Russian Far East

Alders (Alnus spp.) often dominate at nutrient-poor sites by symbiotic relations with atmospheric nitrogen-fixing bacteria. However, little is known about quantitative relationships between root nodule as a nitrogen acquisition organ and leaf as a carbon acquisition organ. To examine carbon allocation, nitrogen acquisition and net production in nutrient-poor conditions, we examined allocation patterns among organs of shrub Alnus fruticosa at a young 80-year-old moraine in Kamchatka. Slopes of double-log allometric equations were significantly smaller than 1.0 for the root mass, leaf mass and root nodule mass against stem mass, and for the root nodule mass against root mass, indicating that smaller individuals invested disproportionally more biomass into resource-acquiring leaf and root tissues than to supportive tissues compared to older individuals. The slope of allometric equation of root depth against stem height was 0.542, indicating that smaller/younger individuals allocate disproportionally more biomass into root length growth than stem height growth. On the contrary, the root nodule mass isometrically scaled to leaf mass. The whole-plant nitrogen content also isometrically scaled to root nodule mass, indicating that a certain ratio of nitrogen acquisition depended on root nodules, irrespective of plant size. Although the net production per plant increased with the increase in stem mass, the slope of the double-log regression was smaller than 1.0. On the contrary, the net production per plant isometrically increased with leaf mass, root nodule mass and leaf nitrogen content per plant. Since the leaf mass isometrically scaled to root nodule mass, growth of each individual occurred at the leaves and root nodules in a coordinated manner. It is suggested that their isometric increase contributes to the increase in net production per plant for A. fruticosa in nutrient-poor conditions.

Changes in Wetland and Floodplain Sedimentation Processes in the Middle Reach of the Amur River Basin

Remarkable land-cover changes have recently occurred in the Amur River Basin. In particular, cultivated area has increased in China, while deforestation has advanced in Russia. It is possible that these land-cover changes will affect the hydrologic environment of the Amur River and the movement of material through the river. We reconstruct historical environmental changes in the Amur River Basin using floodplain sediments. We focused on the Sanjiang Plain in Northeast China, which is on the middle reach of the Amur River. We investigated sediment profiles on the floodplains of the river and its tributaries from outcrops or sediment cores obtained by hand boring. These confirmed recent coarsening of fluvial deposits at many locations on the floodplain, along the Amur, Songhua, and Ussuri rivers. Here, silt-clay layers were covered by 30–70 cm-thick sandy deposits. We postulate that the grain size coarsening of the floodplain deposits ensued from an increase in peak discharge and coarse material supplied by farmland expansion and forest reduction.