The growth of felled individuals of Eucalyptus camaldulensis was measured in order to develop techniques for regenerating afforested stands in drylands. All felled individuals sprouted multiple stems, and no individual died during the measurement period. Therefore, it is considered that afforested stands of E. camaldulensis in drylands are able to regenerate by sprouting. By 5 years after felling, the crown projection area had become larger than that before felling, whereas the timber volume was still much smaller than that before felling. Thus, the sprouted individuals preferentially expanded their crown projection area during the early developmental stages. As a result of this rapid reconstruction of photosynthetic organs, their annual production would become larger than that of saplings, and the sprouted individuals would be able to reconstruct the lost biomass within a relatively short time. However, too short a cycle of felling would offset the advantage of sprout regeneration. The felling cycle must be regulated according to the growth rate of the stand, and is considered to be more than 5 years in drylands. Further research and analysis of the growth patterns are required to optimize the technique for managing dryland afforestation.
Two afforestation technologies aimed at carbon fixation on arid lands were developed, and the available area where those technologies could be applied was estimated. Eucalyptus camaldulensis grew well on saline and hardpan soils in an arid region in Australia. This species, with tolerance to salt, waterlogging, and drought, showed a prospective annual growth rate of approximately 5.0 t/ha/yr (aboveground biomass) at a planting density of as low as 200 trees/ha under such stressful environment. By classifying the total area of arid land by climate and soil type, a prospect that our technologies could be use to afforest approximately 12% of the world's arid land area was obtained.
Climate change and its impact on human lives are one of the most important issues at the present time. In this study, changes in temperature, in relative humidity, and in precipitation, which may have brought about by global warming, were detected by a long-term observation of the Japan Meteorological Agency (JMA). The analysis is particularly significant since it revealed increase in temperature and decrease in relative humidity statistically in two local meteorological observatories in Toyama Prefecture. These changes in broad area of Toyama Prefecture were also investigated by observations during the last three decades. In almost of the area, decreases of ice days and frost days related to the warming in winter and increases of tropical night, hot days, and extreme hot days related to the warming in summer were estimated. Increase in precipitation amount in December and March, and decrease in precipitation days in January and February were also estimated. Prominent climate changes are in spring and autumn, and they presumably affect timing of seasonal transition.
The degradation processes of organoarsenic compounds in aquatic environments depend on microbial activities and significantly influence the arsenic cycles. In Lake Kahokugata, inorganic arsenic was detected through all seasons, while dimethylarsinic acid (DMAA) appeared at only winter seasons, and monomethylarsonic acid (MMAA) was not detected. The Most Probable Number (MPN) procedure detected the DMAA-degrading bacteria at cell densities ranging from 120 to 910 cells/ml. Moreover, when 1 μmol/l of DMAA was added to the water samples collected from Lake Kahokugata at every season, the 99% of DMAA was converted into inorganic arsenic within 35 days of incubation, suggesting that the biodegradation activities maintained same levels throughout all seasons. Total 352 isolates of DMAA-degrading bacteria seasonally obtained were classified into 10 types of which compositions seasonally varied, by the restriction-fragment-length polymorphism (RFLP) analysis of 16S rDNA. The representative 67 isolates degraded DMAA at the various degradation percentages of maximum 64% for 28 days. In particular, the dominated types at all seasons and winter seasons indicated high degradation activities, and phylogenetically belonged to the alpha-proteobacteria and the genus Pseudomonas, respectively. The seasonal similar activities of DMAA-degradation in Lake Kahokugata would depend on the several bacterial species of which compositions seasonally changes.
This study investigated the mobility characteristics of iron slag, as a heavier density granular material compared to natural sand, under currents and waves. Investigation was conducted by running a series of laboratory experiments. The experiment was targeted to reveal the iron slag critical shear stresses (τc) under currents and waves and the advantage of the iron slag to resist wave forces. Bed deformation and local scouring depths were among the main observed parameters. All the parameters were compared to the natural sand. Experiments were mostly conducted in a wave flume that generated regular waves with some variations of wave heights (H) and wave periods (T).
Toyama Prefecture has five government-controlled rivers and a complete water hydrologic basin from 3000 meter-level mountains to estuaries. Taking advantage of these unique geological benefits, College of Technology, Toyama Prefectural University has established an educational program for better understanding of whole river basin environment. The program consists of regular lectures and Field practice. Field practice is a newly offered and core course. Educational effectiveness of Field practice was evaluated through submitted reports and questionnaires results from current and graduated students. According to the results, the students took Field practice in highly positive way and thought that Field practice played a very important role to help them to understand knowledge and skills which they had learned in lectures and laboratory experiments. On the other hand, several weak points were also found and need to be improved.