気候および土壌水分条件にもとづく地域の生産力評価法
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概要
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The growth of vegetation including agricultural crops depends primarily on such environmental conditions as soil, water, climate and topography. Especially, the physiological phenomena of a plant, i. e. , transpiration, photosynthesis and respiration, are influenced by the available energy. Consequently the ecological limit of agricultural products is set by these conditions even if agricultural practice is intensively controlled and managed. Therefore, potential productivity, which is the maximum plant production rate under favorable environmental conditions, takes an important role in giving one of the targets of the production in future agricultural activities. In Chapter II, the estimation model of potential productivity at an arbitrary point has been treated. The productivity was calculated from the temperature, leaf area, photosynthesis-light curve and the incident solar radiation restricted by the arbitrary topographical conditions. Using this model, a simulation analysis was made on several plant communities. The results gave a good representation of the actual production. Of the factors, the role of spatial and temporal variations of solar radiation was the most important in estimating production. This means that potential productivity depends mainly on incoming solar radiation. It becomes clear that the proposed model is useful for estimating potential productivity of a point under arbitrary environmental conditions. In Chapter III, the estimation of potential productivity for an arbitrary region has been presented by the extension of the point model which has been described in the previous chapter. The fundamental of the extending the point model to a regional one was to devide a region into small squares having an arbitrary side length (mesh), and the various data which were sufficient to estimate the potential productivity were collected at every mesh. The potential productivities were estimated for each mesh, including the influence of topographical conditions ; namely, light interception by the surrouding mountains and variations of temperature at the different elevations. Chapter IV deals with application of above regional model to actual region and verification of estimated production values by the actual production． The model was applied to the Lake Suwa watershed in Nagano prefecture under the actual conditions； namely， exisiting plants， topographical and meteolorogical conditions． The potential productivity of the existing plant communities and the regional distribution of agricultural prodcucts were estimated by the model． The estimated values comprehensively agreed with the maximum actual production on paddy rice． Furthermore， the results agreed with the possibility of getting higher production in this watershed． These facts show the effectiveness and possibility of using this model for practical purposes． The proposed potential productivity can possibly be used in re-evaluating the technical level on the actual agricultural fields and for performing reasonable landuse planning． By the way， to estimate actual plant production under various environmental conditions， a vast number of factors are lnvolved in the interacting processes of plant growth， i. e. , solar radiation, temperature, water, soil and fertilizer etc． Of the factors， water is essential for transpiration and plant production process. When available water is limiting， production depends mainly on water. Therefore the knowledge of the effect of water on plant growth and yields under different growing stages is important in the estimation of regional mass production. Chapter V deals with the results of experiments on the effect of soil moisture stress imposed at the different stages of growth on the development and production of soybean． The results of experiments were as follows： （1） Transpiration under limited soil water was directly related to plant growth and productivity at each stage of growth．（2） The relative production （the ratio of actual to potential dry matter production） was nearly equal for the individiual growth stage and over a period of two stages. （3） The relative leaf area （the ratio of actual to potential leaf area） was linearly related to relative cumulative transpiration at each stage． In Chapter VI, estimation of transpiration and productivity with limited soil water has been presented by using experimental results which has been described in Chapter V. A model to predict transpiration and production with soil water deficits was devised． It comprised three submodels dealing with transpiration， growth of leaf area and dry matter production. The transpiration submodel determined potential transpiration from leaf area. The growth of leaf area was estimated based on relationship between relative leaf area and relative cumulative transpiration， including the effect of soil moisture stress． Dry matter production was also calculated from relative cumulative transpiration. Solving the above three submodels alternately， the results gave transpiration and productivity at an arbitrary growth period of soybean． The estimated transpiration and production were compared with the experimental data which were measured under various soil moisture conditions. The estimated values were in close agreement with the ovserved. As a result， the simplified model is usefull for estimating the effect of soil moisture deficits on plant production.
- 信州大学教養部の論文
- 1988-02-25
信州大学教養部 | 論文
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