Spatial Variabillity of Soil Nitrogen Dynamics slong a Slope in a Cryptomeria japonica D.Don Plantation

Spatial variabillity of soil nitrogen(N) dynamics was examined along a slope in a 45-year-old Cryptomeria japonica D.Don plantation in the southeastern paet of Shiga Prefecture. Net N mineralization showed no clear gradient along the slope, while net nitrification and percent nitrification were high at lower positions,and very low at upper positions of the slope. Principal component(PC) analysis showed soil properties were divided into three groups which were PC1(water content and pH), and PC3(total C and N). Regressions of net soil N transformations against PCs scores suggested net N mincralization was mainly regulated by PC3, while net nitrification and percent nitrification were mainly regulated by PC1 and PC2. The difference in the main form of inorganic N was expected to affect soil N availability for plants through the difference in the mobility in negatively changed forest soil. We evaluated the soil N availability that reflebted the ion mobility factors by ion exchange resins and found that greater mobility of nitrate lead to greater soil N availability at lower positions of the slope. In addition, gross N transformations were directly measured using 15N isotope dilution, and the influence of microbial caebon (C) availability on the internal soil N cycles were examined by long-term laboratory incubation. Gross nitrifivation was detected in both soils taken at upper and lower positions on the slope, suggesting that nitrification was also an important process at upper positions where almost no net nitrification was detected. Changes in net and gross N transformations, the organic C and N pools, and microbial respiration suggested that start of rapid net nitrifibation might be affected not only by the availability of C for microbial biomass, but also by the relative availability of C and N

Nitrate-use traits of understory plants as potential regulators of vegetation distribution on a slope in a Japanese cedar plantation

[Background and Aims] Plant physiological traits and their relation to soil N availability was investigated as regulators of the distribution of understory shrub species along a slope in a Japanese cedar (Cryptomeria japonica) plantation in central Japan. [Methods]At the study site, previous studies demonstrated that both net and gross soil nitrification rates are high on the lower slope and there are dramatic declines in different sections of the slope gradient. We examined the distributions of understory plant species and their nitrate (NO3[-]-N) use traits, and compared the results with the soil traits. [Results]Our results show that boundaries between different dominant understory species correspond to boundaries between different soil types. Leucosceptrum stellipilum occurs on soil with high net and gross nitrification rates. Hydrangea hirta is dominant on soil with high net and low gross nitrification rates. Pieris japonica occurs on soil with very low net and gross nitrification rates. Dominant understory species have species-specific physiological traits in their use of NO3[-]-N. Pieris japonica lacks the capacity to use NO3[-]-N as a N source, but other species do use NO3[-]-N. Lindera triloba, whose distribution is unrelated to soil NO3[-]-N availability, changes the extent to which it uses NO3[-]-N in response to soil NO3[-]-N availability. [Conclusions]Our results indicate that differences in the physiological capabilities and adaptabilities of plant species in using NO3[-]-N as a N source regulate their distribution ranges. The identity of the major form of available soil N is therefore an environmental factor that influences plant distributions

アモルファスおよびカイラル磁性体における秩序スピン状態の理論研究

Tohoku University藤田全基課

Enhancement of the anomalous Hall effect and spin glass behavior in the bilayered manganite La(2-2x)Sr(1+2x)Mn2O7

The Hall resistivity and magnetization have been investigated in the ferromagnetic state of the bilayered manganite La(2-2x)Sr(1+2x)Mn2O7 (x=0.36). The Hall resistivity shows an increase in both the ordinary and anomalous Hall coefficients at low temperatures below 50K, a region in which experimental evidence for the spin glass state has been found in a low magnetic field of 1mT. The origin of the anomalous behavior of the Hall resistivity relevant to magnetic states may lie in the intrinsic microscopic inhomogeneity in a quasi-two-dimensional electron system.Comment: 7 pages, 4 figures, Solid State Communications (in press

Origin of purple asparagus cultivar ‘Pacific Purple’ based on the sequence of sex determination gene

Garden asparagus is one of the most important crops worldwide. Since this crop is dioecious and male plants generally have higher yields compared to female plants, several DNA markers for sex identification have been developed for acceleration of asparagus breeding. Among these markers, Asp1-T7sp and MSSTS710 were found to be effective in sex determination for many asparagus cultivars. However, we previously found that these markers were not completely suitable for sex identification in the purple asparagus cultivar ‘Pacific Purple’. There are two types of male individuals in this cultivar: One type is PP-m, which is identified the sex type by Asp1-T7sp and MSSTS710 markers, while the other type is PP-m* whose sex type is not identified by these markers. Since the sex identification markers are located on the non-recombining Y region, it was expected that the sequence around this region might be different between PP-m and PP-m*. In this study, the sequence of one of the sex-determining genes, MSE1/AoMYB35/AspTDF1, was analyzed, and a comparative analysis was conducted among PP-m and PP-m* of ‘Pacific Purple’, A. officinalis and related species A. maritimus. The results revealed that PP-m and PP-m* has the similar sequence of MSE1/AoMYB35/AspTDF1 gene from A. officinalis and A. maritimus, respectively. ‘Pacific Purple’ is a cultivar developed through polycross hybrid from Italian landrace ‘Violetto d’Albenga’ (VA), suggesting that VA originated from an interspecific crossing between A. officinalis and A. maritimus and that the pollen parent used in ‘Pacific Purple’ breeding contained two types of male individuals with different MSE1/AoMYB35/AspTDF1 sequence. As a result, PP-m and PP-m* of ‘Pacific Purple’ harbors the similar sequences of the MSE1/AoMYB35/AspTDF1 gene from A. officinalis and A. maritimus, respectively

河川洪水流と浅海域砕波の内部機構および波浪による海底地盤の不安定領域に関する研究

取得学位：博士(工学)，学位授与番号：博甲第218号，学位授与年月日：平成9年3月25日,学位授与年：199