In this paper, the author discussed in detail the following facts: the situation of the use of rangelands of China, the rangelands in the relation with ranching industry. In the same time, the author proposed some technical ideas for managing the rangelands in China from the view-point of the sustainable use, that is, the combination of the two sub-systems of farming and ranching, the improvement of environment and conservation of range resources, and the maintenance of the dynamic balance between conservation and use of the rangelands.

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A model fusion method by weighted average is proposed; weights are optimized through cross-validation or 10-fold cross-validation. This method produces a combined model which incorporates models under similar conditions into data in hand. A model to predict rice yield in Fukushima area is improved by a model for Ibaraki area in terms of predictability. Furthermore, a model for discrimination of crab by sizes and sex exemplifies a similar effect when models in different forms are integrated.

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The environmental impacts related with growing international trade of primary products are the world concerns today. Our focus here is forest resources, which contributes significantly to keep the environmental quality, farther liberalization of which has been argued on the table of APEC. Causes of deforestation are various depending on regions; in Asia, timber trade played a key role in wiping out the ancient forests. In this paper, we start with the history and status of forest resource trade in Asia. Then we discuss affects of timber trade on forest resources using some models. The arguments here is not special for forest resources, but applicable for other renewable resources such as fishery products. Because of their physical attributes, treating renewable resources as traditional goods is not always appropriate.

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This study aimed at evaluating nitrogen flows from a manure supply system in a mountainous area where livestock farming was prosperous with a view to environmental conservation. The production and utilization of animal waste, straw as manure and the nitrogen balance were estimated in the agricultural lands. Nitrogen flows were estimated based on official statistics and related studies. The study area was located in Satomi Village, northern part of Ibaraki Prefecture. Forests and woodlands dominated 90% of the total area. Agricultural land area amounted to 8%, 942 ha. The majority of the agricultural land was occupied by rice field and grassland. Density of cows of the agricultural land area was 1.62 ha^-1. Animal wastes were produced 139kg N ha^-1 yr^-1 of agricultural land, 91% of which were used as manure. Sixty one percent of the animal wastes were used as manure in Satomi Village and 29% were carried out to other districts. Crop residues such as straw, leaves and stems were produced 95kg N ha^-1 yr^-1, and 97% of them were plowed in agricultural land.The amount of nitrogen supply to agricultural land was 175kg N ha^-1 yr^-1 in organic matter and 93kg N ha^-1 yr^-1 in chemical fertilizer. The total amount of nitrogen supply to the agricultural land was 336kg N ha^-1 yr^-1. The total amount of nitrogen removal from the agricultural land was 227kg N ha^-1 yr^-1, Consequently, excessive nitrogen on the agricultural land was 109kg N ha^-1 yr^-1. Considerable environmental load was estimated from such a large amount of nitrogen leaching from the agricultural land. If all the animal waste had been applied to the agricultural land in Satomi Village, the proportion of excessive nitrogen would have been considerably increase. However, it was not the case, because part of the animal waste was moved out from the Village to the other districts. But, a large amount of nitrogen remained still in the agricultural land. In Satomi Village, for purpose of environmental conservation, the manure supply system in which animal waste is carried out to other districts should be further enhanced.

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Rice (Oryza sativa L. cultivar 'Akita-Komachi') was grown in a temperate region in northern Japan at ambient (391 μL L^-1) and twice elevated (664-752 μL L^-1) CO₂ concentrations from seedlings until harvesting under field conditions using Free-Air CO₂ enrichment (FACE) system. Under elevated CO₂ conditions, rice showed a significant increase in total dry weight by 15% (ANOVA, P<0.01), no increase in tissue carbon concentration, and decreasing tendency in tissue nitrogen concentration. The carbon fixed by rice was significantly large at elevated CO₂ concentration by 16% (P<0.05), but there was no statistical difference in the nitrogen absorbed. The C/N ratio of rice became significantly high at elevated CO₂ concentration (P<0.05). Plant N derived from fertilizer was 25-27%. In the fertilized N, 37-39% was absorbed by rice, 29% remained in soil, and 31-33% unrecovered in the present experiment. Elevated CO₂ conditions caused no difference in the dependency on soil and fertilizer nitrogen in this first year FACE experiment. Increasing carbon input to the soil by the increase in carbon fixed and high C/N ratio of rice tissue, however, can cause high C/N ratio of soil in the future. This would result in nitrogen deficiency through accelerating the competition for N between rice plants and microorganisms, and require additional use of chemical fertilizer.

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A series of pot experiments were carried out to evaluate the effect of water flow (deference between infiltration and surface flow systems) and the existence of vegetation on the nitrogen removal rate of wetland microcosm. Observed nitrogen removal rates of vegetated pots were 0.77-0.92 g-N m^-2 d^-1 for infiltration systems and 0.40-0.57 g-N m^-2 d^-1 for surface flow systems. Non-vegetated pots revealed the removal rates of 0.40 g-N m^-2 d^-1 for a infiltration system and 0.31 g-N m^-2 d^-1 for a surface flow system, at the approximate average soil and water temperature of 27°C and approximate water feed rate of 0.1 m d^-1. The difference in removal rates between vegetated and non-vegetated pots were more significant in infiltration systems than in surface flow systems. A plausible reason is that in infiltration systems, supply of organic matter from the soil and roots enhanced the removal rate of nitrate nitrogen.

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