Carbon dynamics in the forest ecosystem have an increasing importance from the view point of the global warming. Relationships between topography, vegetation, soil and microclimate were investigated to clarify soil type distribution and soil development processes in a broad-leaved deciduous experiment forest (1ha) in the cool-temperate climate zone at Takayama, Gifu prefecture. As the result of field survey, B_A and B_B type of Brown forest soils developed on the sites where plenty of tree species grow accompanying poor Sasa as a floor vegetation. On the contrary, B_E type of Brown forest soils existed on the sites where the poor tree species grow with a vigorous Sasa vegetation. High positive correlations were found between thickness of litter, decomposition rate of litter and thickness of A layer of soil. Soil development processes are strongly affected by the movement of soil water that was controlled by topography. Here, B_D type developed on the top and south slopes, while B_A and B_B types mainly appeared on the ridges or steep slopes where are oftenly suffered by drought and soil erosion. At the bottom of valley, B_E type distributed which had a thick and humid soil layers. As the results of the study, soil type distribution and thickness of each soil layer was clarified spatially, which provided basic information for carbon storage in the rhizosphere in the experiment forest.

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We propose a method for estimating cultivated land area in arbitrarily selected areas such as small basins. The method uses both statistical data on cultivated land area and land-use data KS-202-1 from the National Land Numerical Information in a Geographical Information System (GIS). The land-use data KS-202-1 are nationwide digital map information of about 100-m resolution made in 1987-1989, sourced from 1:25000-scale topographical maps. We used the statistical data on cultivated land area in each municipality as a base, and information on the spatial distribution of the agricultural land from land-use data as a supplement. We studied land in the west of Aichi Prefecture to calculate the accuracy of our estimation method. In this region, detailed land-use data of 10-m resolution, called the Detailed Digital Information, were compiled as a result of a 1997 investigation into trends in residential land use. Assuming that an estimation derived from 1997 statistical data and the Detailed Digital Information would give accurate values, we used the estimation to evaluate the error in an estimation derived from the 1997 statistical data and the land-use data KS-202-1 from the National Land Numerical Information. When we estimated the cultivated land area in 10-km² rectangular zones, the relative error was 14% for the rice fields and 33% for the upland fields. When we estimated the cultivated land area in 20-km² rectangular zones, the relative error was 12% for the rice fields and 24% for the upland fields.

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We determined diurnal and seasonal changes in the soil respiration rate in a grapevine orchard and clarified their dependence on temperature and rainfall, from autumn of 1998 to summer of 1999. Measurements were carried out at eight points using a multichannel dynamic closed chamber technique. Daily soil respiration rates were 2.6 g CO₂ m^-2 d^-1 in autumn, 0.9 g CO₂ m^-2 d^-1 in winter, 3.8 g CO₂ m^-2 d^-1 in spring, and 5.3 g CO₂ m^-2 d^-1 in summer. There was significantly exponential relationship between summer soil respiration rate and the soil temperature, irrespective of dry or wet soil condition. Soil respiration rates in autumn, winter and spring did not significantly correlate with soil surface temperatures, except for a dry period before rain in spring. The relationship between the soil temperature at 5 cm depth and the soil respiration rate was significant in winter, but not in autumn and spring. This significant relationship was not observed during a wet period with light rainfall (totally ≦4.5 mm over 6-12 h) in autumn and spring, and was observed during a dry period in spring. Post-rainfall soil respiration bursts were observed after light rain in autumn and spring and the bursts disappeared at least within 12 h after the rain. The bursts were not observed after heavy rain in summer. These results indicate that light rainfall accelerates the soil respiration rate. There was no difference in Q₁₀ calculated for soil respiration through all seasons between the soil surface temperature and soil temperature at 5 cm depth, while summer Q₁₀ was larger at 5 cm depth than at the soil surface. The estimated annual soil respiration in our grapevine orchard was 349.4 g C m^-2 y^-1. This value is lower than those in other agro-ecosystems because of lower content of the soil organic matter depending on the cultivation regime peculiar to the grapevine orchard.

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The rainfed rice production in Northeast Thailand is unstable with low yield. In order to analyze the stability of the production quantitatively, it is important to establish a method to calculate water conditions in rainfed paddy fields and to simulate the rice production based on the conditions. So far the authors have constructed a hydrologic model for expressing the water storage and movement in a series of rainfed paddy field lots. This study aims at developing a model that can estimate the rice production inputting the water conditions calculated by the hydrologic model. The rice production model consists of two sub-models, namely a growth sub-model and a yield sub-model. The growth sub-model estimates the seeding, transplanting and heading days based on the water conditions calculated by the hydrologic model. The yield sub-model estimates the decrease ratio in rice production based on evapotranspiration (ET) ratio (= actual ET / potential ET) calculated by the hydrologic model. In the modeling site, simulations on the rice production were carried out by combining these models. The simulation results were examined by comparing the calculation results and the observed data. Application results showed that the model can be used efficiently for quantitative analysis on the rice production.

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