Natural soils in urban areas have been disturbed and transformed to artificial soil as a result of surface filling or mixing of construction waste and garbage. Urban soils with lithological discontinuities are generally classified into Man-made soils, under which two subgroups, Landfill soils and Reformed soils, are placed according to grading method. This study aims to discuss the methodology for classifying urban soils developed under park use. The land creating history, use, management and soil physical-chemical properties were investigated for seven urban parks in western Tokyo. A total of 196 samples collected from the surface layer (0-5cm) and the second layer (5-15cm) at 98 sampling sites were applied for soil analyses by taking into consideration of the properties of Andosols (Kuroboku soils), the widely distributed soil in the western Tokyo region. Soil profile, soil compactness, water content, pH (H_2O) and pH (NaF), total carbon content, C/N ratio, and Melanic Index were examined to obtain soil characteristics. The physical-chemical feature of the second layer was regulated by the stress of miscellaneous urban fill depending on specific land creating history of each park. While that of the surface layer was regulated by the use and management of the parks. A diagnostic surface layer was extracted for each use division in the park; preservation forest, grassland, bare land, and wood chip sections. The results suggested a two-dimension coordination system composed of grading method and use, which may help subdividing urban park soils into soil units. Modification of the criteria on soil properties is required to construct a useful system for regional urban planning.

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The fundamental soil characteristics of eight sites in five regions in Thailand-northeast (NE1, NE2), central highland (CH1), west (W1, W2), north (N1, N2) and south (S1)-were studied. Further, the grouping of the soils in the recently published classification system-the "World Reference Base for soil resources" (WRB) was examined. The values of the CEC/clay, which indicate the activities of clay, were highest (40 cmolc kg^<-1> clay) in the soils of the central highland followed by sites N2, W2, and NE2, which were comparatively high (20 cmolc kg^<-1> clay); the values were relatively low at sites NE1 and S1 (approximately 16 cmolc kg^<-1> clay) and the lowest at sites W1 and N1. The strength of the weathering and the chemical activity of the soils can be reflected in the results. The organic matter content of the surface horizons was highest at site W1, followed by sites W2, N1, and CH1. The soils at these sites, including their lower horizons, had considerable organic carbon storage. On the other hand, the soils at sites S1, N2, NE1, and NE2 had low organic matter contents not only in the subsurface horizons but also in the surface horizons. The exchangeable cations in the profile of sites CH1 and W2 did not diminish in the lower horizon, and the TRB value was high. On the other hand, a distinct decrease in the exchangeable bases in the subsoils was observed at the other sites. A very low TRB level at the northeastern and southern Thailand sites should indicate the low potential fertility of these soils. According to the WRB classification, the soils at sites NE1, NE2, and N2 were grouped as Acrisols, those at sites W1 and N1 were grouped as Ferralsols, those at sites CH1 and W2 were grouped as Luvisols, and the soil at site S1 was grouped as Plinthosols.

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In this study, we explore the possibility of constructing SOM simulation models based on experimentally measurable pools of SOM and seek to determine parameters to be taken into account when comparing the behaviors of SOM under different ecological environments. To achieve this, we conducted a comparative analysis of the physical fractions of SOM (LF and BF) and parameters that were biologically determined by incubation experiment for steppe soils from Ukraine and Kazakhstan and forest soils from Japan. The analyzed parameters include potentially mineralizable organic C (C_0) and the rate constant of decomposition and its temperature/moisture dependence. In analyzing the resulting data, we used two different approaches to simulating the observed C mineralization patterns. The first approach supposes first-order kinetics for C mineralization in each sample, with one fixed pool of SOM (C_0) that is decomposed under k values that vary with temperature and moisture conditions. This was followed by a comparative statistical analysis of the parameters and physicochemical properties or amounts of LF and HF. The second approach supposes, for the analysis of the entirety of each steppe or forest soil sample, a universal relationship between the rates of C mineralization at the initial stage of the incubation, i.e., the 7th day (CR_7), the amounts of C in the LF (LFC) and HF (HFC), and their respective rate constants k_1 and k_2 that vary with temperature and moisture conditions. The general trends of the parameters obtained by the two approaches are similar in that the possible effect of pH and differences in the nature of the LF from the respective environments were considered to be important factors in the SUM decomposition process. Although the first approach, based on long-term incubation, is commonly used to determine the temperature/moisture dependence of SOM decomposition, the second approach successfully incorporates the physical fractions of SUM (i.e., LFC and HFC) as measurable pools in simulating the SOM decomposition rate during the early stages of incubation (7th day) for each ecosystem. Despite several remaining problems, the integration of the measurable fractions into SOM-simulation models is worthwhile because it substantially increases the possibility of validating these models when comparing actual and simulated changes in SOM in different ecosystems.

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