Tomoyasu Ishida

USE OF BALLOON AERIAL PHOTOGRAPHY FOR CLASSIFICATION OF KUSHIRO WETLAND VEGETATION, NORTHEASTERN JAPAN

Kushiro wetland in northeastern Japan is a Ramsar-designated wetland of international importance (1980) that is characterized by high biodiversity and spatial heterogeneity. These characteristics of the wetland also present innumerable challenges for mapping and monitoring such unique ecosystems. Recent advances in remote sensing technology have provided many sensors with different spatial and spectral scales and resolutions. However, they are still inadequate for mapping wetland vegetation at a large scale for various reasons, such as inadequate resolution and high costs. This study was designed to evaluate the potential of balloon aerial photography to acquire high resolution (15 cm pixel size) imagery for mapping wetland vegetation in the Akanuma marsh. We used a standard 28-mm non-metric camera (Nikon-F-801), which seven specific categories (species mixes) were successfully delineated. It was possible to classify small shrubs mixed with herbaceous plants; moss bogs with pools; dwarf shrubs with sedges; and moss with alpine plants. From this research, it seems that balloon aerial photography is a powerful tool for mapping temperate wetland vegetation, allowing classification of specific and typical vegetation types to the genus and species level.

Automated 3D Forest Surface Model Extraction from Balloon Stereo Photographs

We upgraded an automated forest digital surface model (DSM) extraction method from balloon stereo photographs of a tropical peat swamp forest in Narathiwat, Thailand by evaluating the image matching accuracy and forest surface height (FSH) estimation. We modified an image correlation matching method based on the characteristics of the tree crown shapes. The mismatched area was less than 3 percent of the total area. We estimated an FSH map in a 60 m 60 m plot by both photo estimation and field measurement, and set the unit area for FSH averaging at 10 m 10 m. The root mean square of the differences between the mean photo-estimated and mean field-measured FSH was 3.8 m, which was revised to 1.9 m when the forest gaps were extracted offline. These differences were within a reasonably practical range since the range of the mean field-measured FSH was 10.0 to 21.4 m.

Assessment of spatial variability of penetration resistance and hardpan characteristics in a cassava field

Soil compaction is generally defined as an increase of the natural density of soil at a particular depth. This compacted soil layer spatially varies over the field. Describing within-field variability is a fundamental first step towards determining the size of management zones. The purpose of the study was to explain the spatial variability of penetration resistance (PR) and hardpan characteristics. Soil PR, dry bulk density (BD), and water content (WC) were measured on the nodes of a mesh. Statistical and geostatistical analysis were used to analyse the spatial variability of PR at 5 depths: 0.0–0.1, 0.1–0.2, 0.2–0.3, 0.3–0.4, and 0.4–0.5 m, and hardpan characteristics. PR had the maximum variability among the measured properties. Hardpan lower edge depth varied from 0.297 to 0.714 m, having a mean and CV of 0.411 m and 20.43, respectively. PR was inversely related to WC. Correlation between BD and WC and PR for the same layer was relatively high. PR and hardpan characteristics showed spatial variability across the field, except PR at depth 0.1–0.2 m. Spherical isotropic models fitted all the measured properties. The range of values of the spatial structure was greater than 7.6 m. The results showed that hardpan and PR spatially varied across the field. These results are important in determining the necessary tillage technique as well as the tillage depth and the target compacted area for a suitable land management. These results also have important implications for how site-specific management information should be collected and explained.