With the aim of developing efficient methods for sweet potato production in arid or semi-arid regions, we investigated effects of soil water content in the root zone on the growth and yield of sweet potato grown in sandy soil. In the first experiment with potted plants, the effects of soil water content on the leaf stomatal conductance of sweet potato were compared with four other agricultural plant species in order to examine the drought tolerance level of sweet potato. The soil water content were controlled by different irrigation regimes. The results showed that sweet potato after a period of drought stress had the ability to quickly increase its leaf conductance after re-watering. In the second experiment, sweet potato was grown in containers filled with sandy soil and water table levels in soil were maintained at 15 cm (treatment code: D15), 20 cm (D20), 25 cm (D25) and 30 cm (D30) from the soil surface. The volumetric water content and O₂ and CO₂ concentrations in sandy soil were monitored periodically. Water table depth in sandy soil affected soil volumetric water content and O₂ and CO₂ concentrations in the root zone. The soil volumetric water content and soil CO₂ concentration at 15 cm depth from the soil surface varied from 7% to 46% and 0.8 to 2.7%, respectively, in the following order: D15 > D20 > D15 > D30. Tuberous root dry mass were the greatest in D25 and the least in D30, and the decreasing order of the ratio of root dry mass to whole-plant dry mass was D25 > D20 > D15 > D30. In conclusion, tuberous root production of sweet potato can be promoted by maintaining sufficient distance of the water table from the soil surface to keep volumetric water content at 10-15% and low CO₂ concentrations in sandy soil with the bottom irrigation system.

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The coexistence of seagrasses and corals at Bise, Okinawa, Japan, was investigated in terms of nutrient dynamics, dissolved organic carbon (DOC), and microbial abundance. Four incubation conditions (seawater, seagrass, coral, and seagrass with coral [sg+cr]) were examined using in situ incubation methods. ¹³C was used as a tracer to evaluate primary production in the water column and carbon fixation in seagrass and coral tissues. Primary production was higher in the water column in seagrass incubations, resulting in increased dissolved oxygen (DO) concentrations in the surrounding water. In this treatment, DO was also significantly positively correlated with DOC concentration. Seagrass produced higher amounts of DOC in sg+cr compared to coral incubations (1.2 ± 8.8 μM) by generating 21.6 ± 19.1 μM into the water column. DOC concentrations in the seawater were positively correlated with bacterial abundance. Bacteria are important in the recycling of carbon in the system of coexisting coral and seagrasses due to their use of DOC exuded from both seagrasses and coral, which, in turn, enhances the assimilation of carbon by corals. Therefore, the production of carbon in coral tissues increased when coral was incubated together with seagrass. Similarly, nutrient uptake was highest in the sg+cr incubations. In this environment, where seagrass and coral coexist, corals can utilize DOC exuded by seagrass to increase carbon assimilation via microbial activity, while seagrass can assimilate nutrients and microbially degraded DOC from coral metabolism in the environment.

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Water mass conditions in Lagoon Notoro-ko are affected by the hydrodynamics of the Okhotsk Sea out of the lagoon. In the present study, the relationship between seasonal replacement of the water masses and seasonal variation in abundance of copepods (or copepod species) was examined. During summer and fall, high saline water (>33 psu) originating from the Soya Warm Current occupied the lagoon. In winter, this water was replaced by lower saline water (<32 psu) from the East Sakhalin Current. Abundance of copepods in the lagoon was highest in May and lowest in November, and then increased again in December. Although relative abundances of cold-water and eurythermic species was comparable in May and July, the latter became dominant in August and September and the former in October and December. This indicates that seasonal change of the community structure of copepods in Lagoon Notoro-ko is strictly controlled by the seasonal water mass replacement.

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The antioxidant capacity of food is vital for maintaining our health, and miso is a food rich in antioxidants. We used soybean koji, the antioxidant content of which we expected to be high, as an ingredient of rice koji miso, and we examined the effect of the proportion of added soybean koji on the antioxidant capacity of miso during preparation and maturation. The oxygen radical absorbance capacity (ORAC) value was used as a measure of the antioxidant capacity of miso in this experiment. The ORAC value of soybeans was 10 or more times higher than that of rice. The ORAC value of rice did not change after immersion of the rice in cold water but increased by 3.2 times after the production of koji. The ORAC value of steam-boiled soybeans increased by 1.2 times after the production of koji, and that of crushed soybean koji was 1.6 times that of steam-boiled soybeans. The hydrophilic antioxidant content values were higher than the lipophilic antioxidant content values in both rice and soybeans. Maturation testing showed that the greater the amount of soybean koji used in the miso, the greater the increase in antioxidant capacity. The final ORAC value was 176.3 μmol TE/g for miso without soybean koji and 460.9 μmol TE/g for miso with soybean koji added at 60% of the total ingredient weight. The ORAC values after 8-weeks of maturation were 2.4 to 3.7 times those before maturation. Our results demonstrated that soybean koji can improve the antioxidant capacity of rice koji miso.

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In the present study, we confirmed the utility of portable scanning lidar for landscape modeling of a garden with tree communities and quantification of biophysical variables of the trees in the garden. Multiple measurement positions were established between each tree in the garden and laser beams were fully illuminated to the trees. Obtained 3-D point cloud images were registered and shading effect was added to the data corresponding to a building and trees. Through these processes, a 3-D landscape model of the garden was produced. The model allowed to visual assessment of the garden from any viewpoints and it was confirmed that the model faithfully reproduced the complicated form of the trees and the one of the building within the garden. Then, 10 trees were selected from the model and their tree heights, diameters at breast height were estimated. By comparing the estimation and the actual values, the errors of the tree heights and diameters at breast height ranged from -0.48 to 0.28 m and -0.04 to 0.05 m, respectively. Moreover, stem volume was estimated from the lidar-derived tree heights and diameters and a stem volume map was produced.

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Dual-polarimetric SAR (Synthetic Aperture Radar) was used for estimating abandoned rice paddies. First, ground validation data was prepared based on the data reported in a previous study and a google earth image. Second, a dualpolarimetric SAR image taken just after water filling in rice paddies was prepared and the lexicographic covariance matrix was calculated in each pixel from the scattering elements of the SAR image. Third, classification of three categories (rice paddies, abandoned rice paddies, residential area) was conducted to the image based on each element of the covariance matrix. For the comparison of the classification, the classification was also conducted using other two satellite images, i.e. the ones of AVNIR-2 and single-polarimetric SAR. As a result, overall accuracy and kappa were 55%, 63% and 22% and 0.32, 0.48, -0.04 for dual-polarimetric SAR, AVNIR-2, and single-polarimetric SAR images, respectively. In the dual polarimetric SAR image, abandoned rice paddies were overestimated, while rice paddies were underestimated.

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