The degradation of rice straw ploughed into a paddy field was studied using ¹³C as a tracer. The changes in the δ¹³C value of soil organic carbon of the paddy field where ¹³C-enriched rice straw had been buried in April 2008 were determined. The amounts of organic materials contained in the buried rice straw decreased to about 50% of the initial value during the first month of the experiment, and thereafter, decreased relatively slowly during the experimental period. The ¹³C concentration in rice plants grown in this paddy field increased rapidly and then decreased. The high ¹³C concentration in the rice plants suggested that they took up carbon derived from rice straw buried in the paddy field soil by photosynthesis. The ¹³C concentration of the air in the hollow stems of the rice plants immersed in a solution of ¹³C-labeled sodium bicarbonate was high. These results suggest that rice can take up inorganic carbon from soil through the roots.

The functions of extracellular substances (ESs) that contribute to the protection of cells against ultraviolet (UV) radiation were investigated in the terrestrial cyanobacterium, Nostoc sp. HK-01. The original advanced method was used successfully and was found useful for UV- protective bioassay. Cells with and without ESs were exposed to UV radiation, and results showed the survival rate of the cells with ESs was higher than that of the cells without ESs. The ES of Nostoc sp. HK-01 did not show the specific reflection; however, the high absorption in the UV range, especially UV-C range, was investigated. The results indicated the presence of substances with UV-C protection properties in the ES. Additionally, we confirmed other functions related to cell differentiation, namely, akinete germination, differentiation to vegetative cells, and differentiation to hormogonia, in ES. This phenomenon showed in a limited concentration of ES. In the germination test, contribution of elements in ESs had great effect; however, some inhibiting and promoting effects were confirmed as some organic compound. The occurrence of differentiation in hormogonia by ESs was first examined and confirmed during the early stages of akinete germination. Our results demonstrated that Nostoc sp. HK-01 cells may have unique abilities during cell hydration and drying under harsh environmental conditions.

Knowing the stand timber volume in a forest is necessary for good forest management. A typical way to work out stand timber volume is to use the area-based approach (ABA) with airborne LiDAR. The ABA requires checking the model applicability and parameters against other forest areas. The present study developed a stand timber volume estimation based on publicly available data on the Internet. The objectives of the present study were 1) to evaluate errors in stand timber volume using the ABA and 2) to examine the factors affecting these errors. The study area was located in the eastern part of Shizuoka Prefecture, with 15 plots in Cryptomeria japonica-dominated forests and 13 plots in Chamaecyparis obtusa-dominated forests. Errors in stand timber volume were evaluated by comparing the airborne LiDAR results with results of conventional methods. Relative root-mean-square error (RMSE) and bias were 20% and –14% for the coniferous forest parameter and 17% and –11% for the mixed forest parameter, respectively, resulting in underestimations. The multiple regression analysis showed that the determination coefficient (R²) was 0.66, the relative error was underestimated as the total basal area increased, and the relative error was underestimated more for C. japonica than for C. obtusa. The errors in the present study were relatively small compared to seven previous studies. Therefore, the present study showed that estimating the stand timber volume by using the ABA was valid in the eastern part of Shizuoka Prefecture.