Eikichi Shima

Changes in the quality of chromophoric dissolved organic matter leached from senescent leaf litter during the early decomposition.

Chromophoric dissolved organic matter (CDOM) leached from leaf litter is a major source of humus in mineral soil of forest ecosystems. While their functions and refractoriness depend on the physicochemical structure, there is little information on the quality of CDOM, especially for that leached in the very early stages of litter decomposition when a large amount of dissolved organic matter (DOM) is leached. This study aimed to better understand the variations/changes in the composition of CDOM leached from senescent leaf litter from two tree species during the early stage of decomposition. Leaf litter from a conifer tree (Japanese cedar, D. Don) and a deciduous broad-leaved tree (Konara oak, Thunb.) were incubated in columns using simulated rainfall events periodically for a total of 300 d at 20°C. The quality of CDOM was investigated based on the fluorescence properties by using a combination of excitation-emission matrix fluorescence (EEM) and parallel factor analysis (PARAFAC). In addition, the phenolic composition of DOM was investigated at a molecular level by thermally assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC-MS) in the presence of tetramethylammonium hydroxide (TMAH). The EEM was statistically decomposed into eight fluorescence components (two tannin/peptide-like peaks, one protein-like peak, and five humic-like peaks). A significant contribution of tannin/peptide-like peaks was observed at the beginning of incubation, but these peaks decreased quickly and humic-like peaks increased within 1 mo of incubation. The composition of humic-like peaks was different between tree species and changed over the incubation period. Since tannin-derived phenolic compounds were detected in the DOM collected after 254 d of incubation on THM-GC-MS, it was suggested that tannins partially changed its structure, forming various humic-like peaks during the early decomposition.

Influence of irrigated paddy fields on the fluorescence properties of fluvial dissolved organic matter.

This study investigated seasonal and geographical variation in the fluorescence properties of dissolved organic matter (DOM) in a river system that includes rice paddy fields in its watershed. The river system covers a northern area of the main island of Japan, and between 6 and 45% the watershed area of the tributaries is paddy fields. Water samples were collected monthly from eight tributaries for 1 yr, and the fluorescence properties of DOM were monitored by combined excitation-emission matrix (EEM) and parallel factor analysis. The EEM was statistically decomposed into six fluorescence components with different environmental dynamics. The relative proportion of these components varied with season and geographic location, the former having a greater effect than the latter. Seasonal variation is largely attributed to changes in the source of DOM associated with irrigated rice cultivation practice. The fluorescence component composition showed a stronger autochthonous signature, which varied over a wider range during off-cropping period (October-April) than cropping period (May-September). During the cropping period, a large amount of allochthonous DOM with relatively similar quality was transported into river water from flooded paddy fields and masked the variability in the quality of DOM among tributaries. Therefore, irrigated rice cropping practices are considered to be one of major factors that influence seasonal and geographical variation of fluvial DOM composition.

Effect of cattle behavior on outflow water from grassland in Japan

Our preliminary study demonstrated the promising possibilities of the combination use of GPS and GIS in relating geomorphological and environment information and in subliming a variety of first order information to a higher order. We surveyed geomorphology, soil moisture contents of the surface soil, and the distribution of cattle dung and cattle tracks in a grazed pasture using GPS and GIS. Furthermore, pattern of the water flow on the pasture was simulated on GIS. Some results include (1) water contents of the surface soil in the grazed pasture were high at low-lying area. (2) cattle tracks tended to be formed along cattle fence, and the elevation angle of major cattle tracks was < 10 degrees. (3) A positive correlation was observed between the densities of cattle dung of the watershed and the average of the total dissolved nitrogen concentration in runoff water. As such, GPS-GIS system will be very useful in the management of grazed pasture.

Development of Personal Remote Sensing System for an Extremely Narrow Area

The acquisition cost of the image data by the satellite and the aircraft for the remote sensing is very expensive. And, it may not be able to get a required image by conditions of weather. Particularly, satellite image data is lengthy in case of remote sensing of the extremely narrow area like a paddy field (100 * 100m) in Japan. One of those solutions is to develop an easy and low-cost aerial photography system by the unmanned helicopter. The purpose of this study is to develop the personal remote sensing system for the extremely narrow area. Its system consists of aerial photography device which can acquire the image of 4 band (R,G,B, Near-infrared ) and image processing software of the own work. The made aerial photography device consists with the radio controlled miniature helicopter, two digital still cameras, network camera board, wireless LAN and the notebook computer for the terrestial station. One of the two digital still cameras was remodeled to increase the sensitivity of the NIR stage to 1100nm mostly. And, it can take pictures with seeing the motion picture of the finder of the digital still camera in the terrestial station by the network camera board carried on the R/C helicopter and wireless LAN. A developed aerial photography system can acquire an image by the aircraft altitude of 100m. At this time, that image is a 100*70m area, and that resolution is several cm/pixel. The developed software has the following function: Correction of pixel value of RGB and NIR image by the exposure value, Pixel matching between RGB and NIR image, Composition of the natural color image, Computation of NDVI.

Effect of Behavior of Pasturing Cattle on Water Quality in Grassland

Recently, the river water quality has becomes a problem in the livestock farming areas. Then, in this paper, the effect of behavior in cattle on water quality in grassland were investigated in Aomori Prefecture, Japan. As a result,As a result, total nitrogen concentration was proportional to the grassland area ratio and increased and outflow rate of total nitrogen from the grassland was from 3 to 5 percentage. The behavior of pasturing cattle were roughly classified into four groups, standing rest, lying rest, feeding behavior and locomotion(walking, trotting, galloping and cantering). Rest on shelter woods was observed when it is day, feeding behavior and locomotion was observed when it is morning and evening.The loads of total nitrogen and total phosphorus increased in the grazing time and the rain.