Journal of the Japanese Agricultural Systems Society
Online ISSN : 2189-0560
Print ISSN : 0913-7548
ISSN-L : 0913-7548
Volume 20 , Issue 2
Showing 1-4 articles out of 4 articles from the selected issue
Contributed paper
  • WUYUNNA, Yunxiang CHENG, Katsuo OKAMOTO, Ichiro TANIYAMA
    2004 Volume 20 Issue 2 Pages 160-167
    Published: October 10, 2004
    Released: October 31, 2016

    The productivity of the semiarid grasslands in Inner Mongolia, China has been decreasing rapidly due to the vegetation degradation. Using vegetation as an index, this research analyzed the changes in the characteristics of the vegetation community along a profile from inhabitants to protected non-grazing areas, and evaluated the affects of grazing to the grasslands. With an increase in grazing intensity, the dominance of Aneurolepidium chinensis and Stapa grandis in primary communities have decreased, while the dominance of Artemisia frigida and Potentilla acaulis have increased. With the increase in grazing intensity, physical properties of surface soil changed, i.e., the soil hardness and capacity increased, and the soil porosity decreased. Such changes can be used as an index to evaluate grassland degradation. The growth and development of vegetation communities depend on their biological characters and environmental conditions. The height of plant and the biomass in a vegetation community decreased with the increase in grazing intensity, while the composition of the community remained unchanged. Effects on synusias depend on grazing intensities. In the sub-shrub synusia composed of diverse species, Artemisia frigida was the most grazing-resistant. In terms of the moisture ecological type of vegetation, arid-growth species dominated in the community, communities and were complemented by mid arid-growth type of vegetation according to grazing intensity. The mid-growth and arid mid-growth types of vegetation were affected by grazing intensity, i.e., an increase in grazing intensity caused decreases in the biomass and diversity of mid-growth and arid mid-growth types of diverse vegetation.

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  • 3. A new simple survey method of soil carbon storage based on the characterized soil horizon
    Shugang JIA, Tsuyoshi AKIYAMA
    2004 Volume 20 Issue 2 Pages 168-175
    Published: October 10, 2004
    Released: October 31, 2016

    As soil is the largest pool of carbon storage in the terrene, it is important to measure the amount of storage of soil carbon in each ecosystem. But there exist many difficulties, because it needs both data of bulk density and carbon content at each soil layer. A simple survey method of soil carbon storage is proposed based on the characterized soil horizon, is "characterized soil horizon survey method". The new method is developed using the results obtained in the previous study. It was done by the precise field investigation method of soil carbon storage with 100 plots in the 1-ha experimental cool-temperate forest ecosystem. The characterized soil horizon reflects the soil nature, which lies at a specific depth of soil layers. To estimate carbon storage in the whole soil layers, 50-60 cm layer was selected by the stepwise multiple regression analysis, which contributed 77.2% of accuracy. The equation obtained by the characterized soil horizon survey method was:

    y= 5.298a + 1670.839

    where, y is total carbon storage in whole soil layers (kgC/ha), and a is carbon storage in 50-60 cm layer (kgC/ha). In the validation test, soil profile samples at 50-60 cm layers taken at random 20 points were enough to estimate the remaining 80 points with the accuracy of 76.7%. To decide the characterized soil horizon in the whole study area, it requires much information at many points of the areas. So the improved soil sampler puts teeth in the new survey method, which can collect soil samples just in the original field state. As the new method combined with soil sampler can reduce time and labors comparing the existing digging method, it could substitute the existing method, contribute to the standardization of soil survey and become a powerful tool for the comparison obtained by other methods such as model and remote sensing.

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  • Motoko INATOMI, Hideshige TODA, Hiroshi KOIZUMI
    2004 Volume 20 Issue 2 Pages 176-184
    Published: October 10, 2004
    Released: October 31, 2016

    To investigate the effect of artificial nitrogen load on soil respiration, the experiment was carried out in a cool-temperate forest in Japan. Three experimental sites, which consists of a coniferous forest, a broad-leaved deciduous forest with Sasa community and a broad-leaved deciduous forests without Sasa community, were established in the cool-temperate forest. We loaded 0 kg N ha-1 yr-1, 20 kg N ha-1 yr-1 and 40 kg N ha-1 yr-1 as NO3NH4 in each experimental site. The treatment of nitrogen load was started from 1999 to 2001, and soil respiration rates were measured in 2000 and 2001 using the closed chamber method. Soil respiration rates showed clear seasonal changes in both years of 2000 and 2001, irrespective of the amount of nitrogen load. The soil respiration rates in 20 kg N load treatment were higher than those in 0 kg N load in 2000 in all experimental sites. On the contrary, in 2001, the soil respiration rates in 0 kg N load were higher than those in 20 kg N load in both of the broad-leaved experimental sites, although the soil respiration in the coniferous site showed the same result as in 2000. Moreover, developing a statistical model based on the relationships between soil respiration and soil temperature, we compared temperature sensitivities obtained from each experimental site. Temperature sensitivities obtained from 20 kg N load site had a largest sensitivities in all experimental forests, whereas that from 0 kg N load site had a smallest sensitivities. These facts suggests that temperature sensitivities of soil respiration might become stronger by the nitrogen load treatment. In addition, considering global environmental issues which are both of global warming and increase in nitrogen deposition, we compared the differences in soil respiration among the experimental sites. The amount of soil respiration increased in 33%-47% when soil temperature was raised by 3 ℃ than the present condition. The effects of the global environmental issues on soil respiration were different among vegetation types and nitrogen load treatments.

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  • Fumihito MIYATAKE, Takeo SHIINA, Yukio TASAKA
    2004 Volume 20 Issue 2 Pages 185-192
    Published: October 10, 2004
    Released: October 31, 2016

    In order to develop a distribution model of food resources in a local level, material flow on food industry, which used original weight, nitrogen-base and carbon-base as index, was investigated. Flowing quantity was estimated based on official statistics and survey data so that everyone can construct a flow model easily. This study focused on material flow of Ibaraki prefecture in the year 1990 and 1995. The results showed that there were three features, which were associated with food self-supporting ratio, food wastes and food service industry. Food self-supporting ratio with original weight was about 24% in 1990, but decreased to about 14% in 1995. The discharge of food wastes hardly changed during five years, but about 30% of food consumed in Ibaraki prefecture were thrown away as food wastes. Therefore, it is necessary to tackle the problem against reduction of the food wastes. The growth rate of the quantity of food distribution into the food service industry was high compared with food manufacturing industry and food distribution industry, suggesting a promotion of eating out. The material flow model developed by this study made clear the flow of food resources in a local level. It is possible for everyone to make easily this material flow model, because this model is made basically by official statistics. In addition, this material flow model is effective as a model analyzing a local area.

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