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Hiroshi Seino
1997 年 52 巻 5 号 p.
367-376
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Carbon dioxide levels in the atmosphere have increased from about 280 to 356ppmv since the pre-industrial period. An IPCC report estimated that the increase in global average surface temperature at equilibrium resulting from a doubling CO
2 would be likely to be between 1.5 and 4.5°C, with a best estimate of 2.5°C. Such climate change is expected to have great impact on crop production. Crop model simulations under the condition of current cultivars and cropping systems indicates that a 2xCO
2 climate would substantially increase crop yield and its stability in northern and north-central Japan, and that, in south-central and south-western Japan, it will decrease the yield and its stability to a marked extent. By aggregating these regional impacts over the whole country, national crop production is concluded that would not change significantly from the current level. However, the variability of yield is likely to increase, reflecting increased high-temperature-induced spikelet sterility in south-central and south-western Japan. Adjustment of agricultural practice, such as advancing the planting date and application of supplemental irrigation, is necessary to adapt to climatic changes projected from the GCMs. The yields of crops could increase by introducing adjustment of agriculture practices under the predicted warm climate; however Kyushu where higher temperature could result in heat stresses on crops, it is expected that the yield reduction 2xCO
2 climate could not be recovered by supplemental irrigation and advancing the planting date.
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The Assessments for Russia Using Alternative Scenarios
Gennady MENZHULIN
1997 年 52 巻 5 号 p.
377-407
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Now world population is near 6 billion and has doubled for the last 35 years. The population increase and its future explosion inevitably attracted the attention of ecologists, because the mankind can face a crisis associated mainly with the fool production for the new six billion of people who will acid to the world community in the middle of next century. The population increase and its future explosion avoiding this food problem? To answer this question, possible effects of carbon dioxide increase and its induced global warming on agriculture should be taken into account.
To reliably assess future agroclimate conditions, it was suggested that GCM generated climate changs and paleoclimate scenarios based on the past warm epochs, when carbon dioxide and mean surface temperature were higher than those in the present time, should be used. The nine models and three paloclimate scenarios have been used to assess agricultural consequences of world climate changes in Russian regions and in the countries of the world.
The major conclusion of the analysis carried out is that expected carbon dioxide increase and anthropogenic warming will in general beneficially affect crop productivity in most agricultural regions of the world, especially in temperate zone and some arid regions.
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Research or Re-Search
E. T. Kanemasu, Ian Flitcroft, Bin Li
1997 年 52 巻 5 号 p.
409-417
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The growing demand for food and fiber will be highest priority for governments in developing countries. There is general consensus among the scientific community that the world population will approximately double in fifty years. By 2025, nine out ten persons on this planet will live in a developing country. The challenge facing global agriculture is to more than double production. In the past several decades, food production increases came from expansion of cultivated land area, intensification of land management (irrigation, cropping systems, etc.) and yield increases. The current view is that biological yield increases will have to account for the major increases in production to meet our future demands. Our major challenge will be to produce more without damaging the environment and hopefully improve the natural resource base.
The “Earth Summit” in 1992 was concerned with the prospects of depleting our natural resources critical to the survival of our future generations. Sustainable agricultural development was seen as a process of making agriculture more efficient in its use of natural resources. In the United States, sustainable agriculture was defined by some as low input and low yield agriculture. By others, it was what agriculture has been doing for the past several decades. Recently, there has been increasing attention on intensive agriculture meeting future food needs and, therefore, protecting marginal lands from being placed into production. Sustainable agriculture should not preclude high crop yields and protection of biodiversity, soil, air and water; resources must be balanced with meeting the food and fiber needs of a growing population.
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Kyaw Tha Paw U
1997 年 52 巻 5 号 p.
419-428
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
A one-dimensional higher-order closure turbulence model for the transport of mass, momentum, and energy, combined with a layered plant canopy description, has been linked to the Ball-Berry model for stomatal conductance and the Farquhar-von Caemmerer model for photosynthesis. This model is compared to a single-layer big-leaf model which uses the same plant physiology as the higher-order closure model. A multiplicative plant physiology model is also used for both the higher-order closure model and the big-leaf model. The results of the combination of these models are investigated, under simulated elevated CO
2 concentrations. The turbulence model is derived from equating the fourth moments of the turbulent terms as a function of the second moments using quasi-Gaussianity, without using any gradient assumptions. This model has been verified against field data. The canopy model includes a radiation model to account for both shortwave and longwave radiative transfer in 10 layers of plant canopy. The plant leaves are separated into 100 classes, representing layers, leaf angles, and sunlit leaves or shaded leaves. The results show that the more accurate higher-order closure model, when coupled with advanced plant physiological models, predicts lower photosynthetic increases in response to CO
2 concentration increases, than when the big-leaf model or the multiplicative models are used. This implies that General Circulation Model predictions for increased CO
2 fertilization effects may be exaggerated.
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from Big-Leaf to Large-Eddy Simulation
Roger H. Shaw
1997 年 52 巻 5 号 p.
429-436
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
A review is presented of the range of schemes used to mathematically model the microclimate of vegetation canopies and the exchanges of momentum, heat, water vapor and other scalars between the living tissue of plants and the atmospheric surface layer. In order, are considered bulk expressions which do not take into account distinct strata within the canopy, Eulerian diffusion models employing either parallel and series resistances or eddy diffusivities, higher-order closure schemes, and large-eddy simulation. Differences primarily involve the degree to which aerodynamic characteristics of the air flow through and above vegetation are treated. The simplest models have utility in offering estimates of exchange rates that may be applied to large geographic areas, while the most advanced models are used for more fundamental studies of environmental physics.
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Toshihiko Maitani, Kohichi Miyashita
1997 年 52 巻 5 号 p.
437-440
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Simultaneous measurements of momentum, sensible heat, latent heat fluxes, vibration of a rice plant, leaf surface temperature and canopy surface temperature were made in a paddy in the summers of 1994 and 1995. Leaf surface temperature and canopy surface temperature decreased about 1-1.5°C with an increase of wind speed, downward momentum flux or vibration of a rice plant. The lower surface temperatures were probably due to the increase of transpiration from the plant canopy, accompanying Honami-like waves. The observations indicate that remotely sensed thermal imagery is a very useful method to study the interaction between vegetation and the atmosphere.
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O. T. Denmead, R. Leuning, M. R. Raupach
1997 年 52 巻 5 号 p.
441-444
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Lagrangian analysis of transport within the canopy space leads to a physical description by which the mean concentration profiles can be predicted for any given source distribution through knowledge of the turbulence statistics. The concentration profiles are related to the source-sink distributions through a matrix of linear equations, a ‘dispersion matrix’, in which the coefficients are functions of σ
w the standard deviation of the vertical wind velocity, and
TL, the Lagrangian time-scale. The Inverse Lagrangian analysis inverts the dispersion matrix to calculate the source/sink distributions from the mean concentration profiles and profiles of σ
w and
TL. Thus the technique allows separate identification of, say, the respiration of CO
2 at the soil (or paddy water) surface and the uptake of atmospheric CO
2 by plants in the canopy. The observations and the computational scheme required for such applications are relatively simple. The paper describes the use of the technique to infer sources of heat, water vapour and CO
2 in a wheat crop.
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R. L. Desjardins, E. Pattey, J. I. MacPherson, P. H. Schuepp, P. Selle ...
1997 年 52 巻 5 号 p.
445-451
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Most processes on earth involve gas exchange. During plant growth, vast quantities of CO
2 are either absorbed through photosynthesis or lost through respiration. Plants also lose large quantities of water vapour through transpiration. Hence measurements of CO
2/H
2O exchange provide information on how environmental conditions and management practices affect these processes. For example, photosynthetic efficiency, which is a measure of CO
2 uptake as a function of absorbed radiation, and water use efficiency, which is the ratio of CO
2 versus H
2O fluxes, are two very useful parameters that are readily available from these measurements. Gas exchange measurements also provide valuable information on the greenhouse gas buildup in the atmosphere. This paper will review some of the recent progress made in obtaining regional estimates of gas exchange using aircraft-based flux measurements as well as estimating fluxes from the change in CO
2 concentration within the mixed boundary layer.
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Under estimation of eddy correlation fluxes during low wind speed conditions
Y. Ohtani, M. Okano, M. Tani, K. Yamanoi, T. Watanabe, Y. Yasuda, A. R ...
1997 年 52 巻 5 号 p.
453-456
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Eddy correlation observation of sensible, latent heat and carbon dioxide fluxes above a tropical rain forest were conducted in March 1995 in Peninsular Malaysia. The calculated total energy flux consisted of both sensible and latent heats ranged from 50% to 80% of the available energy. Under the low wind speed conditions, the sensible and latent heats were intermittently transported upward according to the plume events. Sum of the sensible and latent heat fluxes generally ranged from 1000 to 2000Wm
-2 during individual plume events, though the time averaged flux was apparently insufficient. It was suggested that the occurrence of large plume events could be spatially localized.
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Yoshisuke Nakano, Masaharu Kuroda, Tomohisa Yano, Koji Inosako
1997 年 52 巻 5 号 p.
457-460
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
In arid regions, evapotranspiration at the edge of irrigated fields sometimes shows a high value. When planning irrigation, spatial differences of water consumption in the field have to be taken into account. A two dimensional numerical model which simulates the formation of boundaries on vapor pressure and temperature was used to estimate evaporation along the fetch. The estimated results of the model were compared with the data obtained from a wind tunnel. The effects of upwind surface temperature on evaporation on the downwind field were clarified.
The data observed in one of the deserts in China were applied in the calculation to discuss the distribution pattern of water consumption along the fetch. The applicability of Bowen ratio method is also discussed and the calculated results show it takes over 200m from the leading edge to achieve a good estimation.
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Seiji HAYAKAWA, Hiroshi TANI, Haruhiko YAMAMOTO, Tamon TSUJI
1997 年 52 巻 5 号 p.
461-464
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Horizontal inhomogeneity is a common occurrence in the lower layers of the atmosphere. For example, in a land-lake interface problem, and in flows over a finite area of irrigated land, abrupt changes of surface conditions, i. e., roughness, temperature and humidity occur simultaneously, and the profiles are no longer in equilibrium. The principal purpose of this paper is to present these phenomena quantitatively from theory.
The profiles of the diffusion coefficient (K) obtained by use of a gradient Richardson number show its peaks at reasonable levels, and the values of K and the peak height increase with the scale of a localized heat source (LHS). These characteristics agree qualitatively with observations in the planetary boundary layer.
When air moves from a cool area to a hot one, the horizontal temperature gradient ∂T/∂x becomes positive above the hot area, and the gradient of vertical sensible heat flux ∂H/∂z becomes positive. On the other hand, when air moves from a hot area to a cool one, ∂T/∂x and ∂H/∂z become negative above the cool area.
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Tamon TSUJI, Seiji HAYAKAWA
1997 年 52 巻 5 号 p.
465-468
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
This rea port gives the result of comparisons between calculated and observed temperature profiles above homogeneous terrain.
The experiment was carried out at the paddy rice field, Natajima, Yamaguchi, with a fetch of over 2km, during 12 August 1995. Temperature profiles up to a height of 10m and wind speeds at a height of 3m were measured using thermocouples and a hot-wire anemometer.
The roughness length and the zero plane displacement height were calculated from the empirical equation (Maid, 1976). Three cases were used in estimation of temperature profiles. In Case 1 and Case 2, they were estimated from the K-theory. In Case 1, diffusion coefficients were calculated by assuming that wind profiles are logarithmic, and in Case 2 the stability of each layer was taken into account, then they were calculated (but wind speeds profiles were logarithmic). In Case 3 temperature profiles and wind speeds profiles were estimated by using the universal function (Businger
et. al, 1971).
For unstable air, observed temperature profiles were much like theoretical profiles obtained from the evaluation in consideration of the stability of each layer (Case 2) and the evaluation using logarithmic profiles of wind (Case 1) did not provide very good fits. Then in comparison between Case 2 and Case 3, Case 3 agreed with observations better than Case 2. For stable air, Case 3 did not agree at all.
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Jun SUZUKI, Keiichi NAKAYAMA, Matsuji MATSUDA
1997 年 52 巻 5 号 p.
469-472
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
During the growing seasons of the last 5 years, we have experienced 3 summer droughts and 1 cool rainy summer. Accurate field water balance information is necessary to manage soil water for stable productivity under such varying conditions.
It is well known that shortages of soil moisture in the root zone result in decreases in evapotranspiration (ET). Such conditions stimulate the root systems of many crops to develop into the deeper soil layer to prevent injury from drought. In this paper, the authors present a method to determine ET from fields of maize in consideration of root spread (depth & width) and soil moisture condition in the total root zone.
Suzuki & Nakayama (1996) observed high ET rates from a maize field under drought conditions, despite soil moisture conditions in the surface to 1.0m soil layer being less than that required for optimum growth. They showed that ET under such conditions proceeded by water uptake from soil deeper than 1.0m. Those findings suggested that the evaluation of ET from soil moisture content data for only the shallow upper layer may underestimate the actual ET, and this underestimation leads to inadequate control of soil moisture for optimum crop production. Here the authors present a new formula for estimating the actual ET, taking the root system and soil moisture content in the soil mass of the total root zone into account. The accuracy of this formula depends on knowledge of the soil layer of the deepest root end in each growth stage. However, measuring this soil depth is troublesome, a new formula presented in this paper would be more practical if this depth could be estimated based on plant growth stage.
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Houquan Lu, Keiichi Nakayama, Guirui Yu, Jun Suzuki
1997 年 52 巻 5 号 p.
473-476
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Based on measurement in a maize field during 1994 and 1995, the modified Priestley-Taylor model presented by Nakayama
et al. (1993) was tested for predicting soil moisture in the field under drought conditions. It was found that the correction factor in the model was strongly influenced by soil hydraulic property. For a wide region soil moisture prediction, to remove difference of soil hydraulic property, the modifying term in the model should use soil water potential instead of soil moisture content. Under drought conditions, for a maize field, the main soil water depletion was not in the shallow root zone, but extended to a deeper soil layer. In that condition for the deeper root crops, when this modified model is applied, the root zone should be regarded as a thicker soil layer.
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Yoshinobu Harazono, Akira Miyata
1997 年 52 巻 5 号 p.
477-480
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
A new method for calculating diffusion velocities within the canopy boundary layer was established, and applied to the CO
2 flux measurements resulting in grater accuracy than the normal aerodynamic method.
A movable NDIR-CH
4 analyzer for field measurements was developed. The vertical CH
4 concentration gradient showing CH
4 uptake by the ecosystem was obtained continuously over a grassland, which gave a downward CH
4 flux of 30-60mg m
-2h
-1. CH
4 flux over a flooded rice field ranged between 5-10mgCH
4 m
-2h
-1 in the daytime and 3-5mg m
-2h
-1 at night. The daily amount of CH
4 emission from the flooded rice field ranged between 80-210mgCH
4 m
-2d
-1. At night the upward CO
2 flux of the rice field was higher under high temperature conditions, which brought about a higher CO
2 sink strength in cool summer weather than in hot summers.
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Kyoko NAKAMOTO, Seiji HAYAKAWA
1997 年 52 巻 5 号 p.
481-484
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The aim of this study is to clarify the distribution of atmospheric CO
2 concentrations in a hiliside tea garden called “Ono tea garden” located in Ube City, Yamaguchi Prefecture. Observations were made at the top, middle and lowest points of the eastern slope in the garden, and we measured micrometeorological factors and atmospheric CO
2 concentrations over the tea canopy. From observational results we found the following principal characteristics of CO
2 distribution: the CO
2 concentration changed with time, affectedby photosynthesis or respiration of tea plants. Interestingly, the concentration was higher at the lowest point of the slope during the night. This phenomenon could be caused by advection from the surroundings produced by the downward current along the slope. Vertical distributions of CO
2 concentration were also affected by photosynthesis or respiration of the tea plants, in a similar way to those observed over the flat field. But during the night the shape of the vertical CO
2 distributions differed from those of the flat field. Namely, vertical CO
2 distributions in the hillside tea garden could have two peaks of concentration, and it could be affected by micrometeorological conditions such as air stability, intensity of vertical shear with downward currents along the slope.
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Nobuhiro MATSUOKA, Yumiko TANAKA, Takashi MACHIMURA, Shinji MATSUMURA, ...
1997 年 52 巻 5 号 p.
485-488
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
We measured CO
2 concentration in a deciduous forest canopy and compared it with wind speed, net radiation and soil respiration. On a clear day, minimum CO
2 concentration was observed at the height where the canopy was the densest. Maximum concentration was observed just above the ground before sunrise on a calm day. The concentration tended to be higher near the ground than near the top of the canopy on all days and this concentration gradient was steeper at night, resulting from the high respiration rate of the soil and from the small transport of CO
2 out of the canopy due to low wind. This suggests that the respiration rate of the soil should be considered when measuring assimilation and respiration rate of plants by the aerodynamic method.
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Nobutaka Monji, Ken Hamotani, Takashi Hirano, Toshifumi Fukagawa, Kazu ...
1997 年 52 巻 5 号 p.
489-492
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
CO
2 and heat fluxes of the mangrove forest in Thailand are investigated based on observation during a dry season. Clear diurnal change was seen in the sensible heat flux. There was a large amount of latent heat flux even at night. The latent heat flux was larger than the sensible heat flux. CO
2 flux changed sign between day and night. The magnitude of the upward flux during nighttime and the downward flux during daytime was about the same, which is considerably different from the flux characteristics during the wet season.
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Y. Yasuda, T. Watanabe, K. Yamanoi, Y. Ohtani, M. Okano, M. Tani, K. N ...
1997 年 52 巻 5 号 p.
493-496
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The bandpass covariance method is proposed by Horst and Oncley (1995) for long term measurements of scalar flux. This method is similar to the direct measurement in principle, but can be achieved by an instrument with slow response and little maintenance on the assumption that there is spectral similarity among scalar fluxes.
We measured the energy budget of a deciduous forest on July 25-27 in 1995, including an experiment for measuring turbulence. Instruments used for this experiment were a sonic anemometer, open-path infrared gas analyzer (fast response sensor) for eddy correlation, and an aspirated humidity sensor (slow response) for bandpass covariance. Using these results, we checked the applicability of the bandpass covariance method for latent heat flux by comparing it with the ordinary eddy correlation method. The spectral similarity in our experimental site was confirmed by the measurements taken by the fast response sensors which showed that normalized cospectra were almost identical between the latent heat and the sensible heat. Diurnal variation of the latent heat flux by the bandpass covariance method agreed well with that of the eddy correlation method. The daily mean value of the latent heat flux by bandpass covariance (July 27) was 108.9Wm
-2 and that by eddy correlation was 107.0Wm
-2. From these results, it can be concluded that the bandpass covariance method is applicable to a long term monitoring of the latent heat flux from a forest.
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T. Machimura, T. Nakai, K. Okada, Y. Tanaka, S. Urano, I. Horiguchi
1997 年 52 巻 5 号 p.
497-500
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The decoupling theory presented by Jarvis and McNaughton (1986) was used in the comparison of the evapotranspiration characteristics of forest, corn and alfalfa canopies. The average values of the decoupling factor Ω
c were 0.53, 0.74 and 0.88 in the forest, corn and alfalfa, respectively, which was in the opposite order for the aerodynamic roughness of the canopies. Ω
c varied largely with the change of the canopy resistance. The Ω
c indicated the variability of the ratio of the evapotranspiration to the available energy (
lE/A). When Ω
c<0.8, the reliability of the evapotranspiration models based on the available energy (e. g. Priestley-Taylor model) should decrease.
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A. Naemura, Y. Fukuoka, A. Tsuchiya, K. Nakane
1997 年 52 巻 5 号 p.
501-504
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
In the Seto Inland Sea District, most population and factories are concentrated in the narrow coastal plains. In this study, the distribution of atmospheric nitrogen dioxide (NO
2) concentration was investigated on the seaside slope of Mt. Gokurakuji, Hiroshima Prefecture. The vertical concentration at an interval of every 50m from 100m altitude to the summit was measured by short- and long-term exposure methods from autumn, 1992 to spring, 1994. As a result, high NO
2 concentrations were detected at altitudes of 100m and 150m, where the forest decline was outstanding, and the values decreased with elevation. With regard to seasonal fluctuations, it is relatively higher in spring and in summer. The most frequent wind direction at the southern foot of Mt. Gokurakuji was SSE In the summer, 1993 and in the spring, 1994, while in the autumn, 1993, and in the winter, 1994, it was in the NW direction. It is thought that the NO
2 concentration was closely related to the horizontal wind, that is, land and sea breezes. Next, temperature profiles at night were observed on the seaside slope in June and in November, 1995, and was correlated to the NO
2 concentration by the short-term exposure method. The result showed that the night-time concentration difference between the upper and lower sites was fairly large. From this, it was estimated that air pollutants are difficult to diffuse through the formation of an inversion layer, and they are not transported within the boundary layer during the night.
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Gui-Rui YU, Keiichi NAKAYAMA
1997 年 52 巻 5 号 p.
505-508
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Based on a study of the characteristics of the stomatal response to environmental factors, a new environmental variable model for estimating stomatal conductance over a long time period was developed. This model was based on multiplying the potential stomatal conductance by the relative degree of stomatal opening during daytime. The estimated precision of this model was quite high.
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Yumiko Tanaka, Takashi Machimura, Keiji Okada, Taro Nakai
1997 年 52 巻 5 号 p.
509-512
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The seasonal variations in turbulence above and within a deciduous forest were studied in the Experimental Forest, in Hokkaido, in the northernmost temperate forest zone. Two three-dimensional sonic anemometer/thermometers were used to measure fluctuations in temperature and wind velocity from the period of leaf development to leaf-shedding. Variations in specific humidity above the canopy were determined with fine wire copper-constantan thermocouples placed near the sonic anemometer/thermometer. The sensible and latent heat fluxes were obtained using the WT and Wq covariance.
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K. Yamada, R. Shirooka, T. Hirota
1997 年 52 巻 5 号 p.
513-516
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The feasibility of regional estimation of nocturnal cooling between the evening mean temperatures and the next morning's minimum temperatures was estimated using with a nocturnal cooling model. Here, we used the data of the Automated Meteorological Data Acquisition System (AMeDAS) and the aerological observation at Sapporo. In the present analysis, we suppose that the possible temperature drop by nocturnal cooling on each clear night are a constant across a region of about 100km x 150km. The possible temperature drops in the 32 cases were about from 15 degree to 24 degree. The ratio of the actual temperature drops at the AMeDAS monitoring points to the possible temperature drop were from about 0.5 to 0.6 at the higher elevations of the inland areas, 0.4 to 0.5 in the plains and around 0.3 in the coastal areas. There was an interesting similarity between the values and the geographical and topographical futures. A model using these values as parameters was applied for 11-clear days in 1990. Estimated values were found to be less than the observed values, but their errors were within almost 2 degrees.
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Yoshinori Suzuki, Kota Takahashi, Tur Muhammed, Kenji Wakimizu, Kaoru ...
1997 年 52 巻 5 号 p.
517-520
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
we found a new material that can decrease temperatures in the clear summer daytime. A hydrated ceramic plate can hold water and evaporate water easily from the surface. Through the evaporative cooling process, radiant heat is changed into latent heat and temperature decreases. The relation of temperature decrease and water content of the hydrated ceramic plate are clearly shown. The critical value is 7% and surface temperature becomes lower than air temperature beyond the critical value in summer daytime. If we use them on the roof of an open-type dairy barn, the radiant heat load to cattle should be considerably decreased.
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N. Ishikawa, H. Narita, Y. Ishii, Y. Kodama
1997 年 52 巻 5 号 p.
521-524
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Assessment of the acidification and changes of the chemical contents of seasonal snow within the snowmelt process were carried out in northern Hokkaido, Japan. The range of pH in the dry snow was 4.7 to 5.3 and EC was 11 to 56μS/cm. These values were similar to those of the snow accumulated on the forest floor and the canopy. Horizontal distributions of pH in snow cover were found to be homogenous. However, once melt water penetrated, the homogenous distributions were partly destroyed even in winter. During the snowmelt period pH of the snow increased and EC decreased to below 10μS/cm. pH of the melt water that percolated through 10cm deep soil accounted for 6.4 to 5.8, and those of the stream 7.1 to 6.8. The values did not change much through the snowy season. The percolated water showed high concentrations of SO
42- and NO
3- compared with those of snow, but the water contained higher Ca
2+ concentrations, which neutralized the anion, and pH of the water increased.
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Rutang Liao, Kenji Tanabe, Fumio Tamura, Akihiro Itai
1997 年 52 巻 5 号 p.
525-528
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Seasonal changes in lipids and their fatty acid composition were measured in bark tissues of three wild pear species,
Pyres betulaefolia, P. calleryana and
P. serotina, to investigate their relation with cold hardiness and air temperature. From September to mid-December, cold hardiness of the three species developed gradually in response to the drop of air temperature. Simultaneously, the increase in the proportion of linolenic acid (C 18:3) in galactolipids was accompanied by the increase of linoleic acid (C 18:2) and decrease of oleic acid (C 18:1) in phospholipids. During this period, variations of fatty acid composition and cold hardiness were closely correlated with the change of air temperature. All of the three species obtained the strongest cold hardiness in mid-December, associated with higher levels of unsaturation in all individual lipids. From January to February, air temperature reached its lowest point, which seems likely to maintain the cold hardiness of trees, thereafter, it started to rise slowly, and gradually reduced the cold hardiness. The variation trends of C 18:3 in galactolipids and C 18:2 in the most dominant phospholipid were obviously reversed after January, which had a pronounced effect on the decrease of cold hardiness.
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Effect of Automobiles and Factories on Environment
PRABAL KANTI ROY, Seiji HAYAKAWA
1997 年 52 巻 5 号 p.
529-532
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
This paper attempts to make clear the characteristics of the magnitude and scope of automotive and factory pollutant emissions in Dhaka city-which are creating an environmental problem in the city. About 451 factories in this city discharge and dump hazardous waste with no regard for the resulting surface and ground water or air-pollution. Most of these factories are bereft of adequate emission treatment. In addition, the increasing traffic, inadequate urban transport infrastructure and services, and an aging and obsolete motor vehicle fleet are giving rise to high air pollution levels. About 86% of the total motor vehicles in this city emit black smoke above the International Standard of 65 HSU. Changing meteorological conditions, such as average wind velocities, wind direction and frequency of showers have influenced the pollutant concentration in the city's air. Without effective measures to control pollutant emissions, the city dwellers will be exposed to unhealthy and dangerous levels of air pollution from automobiles and factories.
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Ken-ichi SUDO, Masashi IWAI
1997 年 52 巻 5 号 p.
533-536
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
In order to observe solar radiation, we set up Agricultural Meteorological Stations (AMS) at 17 sites in Hyogo Prefecture in 1994 and 1995. An AMS was equipped with a thermometer, a rain gauge, a pyranometer and a data-logger. Using the observed solar radiation data at the AMS sites, daily solar radiation (DSR) in each non-AMS site in both July and August 1995 was calculated.
The estimating method was as follows: in the first step, DSR of an average year was calculated by the harmonic method from monthly solar radiation as standardized by the National Institute Agro-Environmental Science of Japan. In the second step, the estimated DSR in the non-AMS site was caluculated from: DSR e, t=DSR a, t+Σ[(DSR e, i-DSR a, i)/Li]/Σ(1/Li), where DSR e, t and DSR a, t are respectively the estimated and an average year's DSR of the target non-AMS site, DSR e, i and DSR a, i are respectively the estimated and an average year's DSR of i-th selected AMS site, and Li is the distance between the target non-AMS site and i-th selected AMS site. Errors between estimated DSR and observed DSR at each AMS site were shown by the Root Mean Square Error. Daily RMSEs in July and August ranged from 1.0 to 3.1MJ/m
2/day, and this estimation method is useful in obtaining accurate solar radiation for all non-AMS sites.
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Y. Aono, X. Zhang, N. Monji
1997 年 52 巻 5 号 p.
537-540
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The heat budget of the forest in the Mt. Ikoma area, located at the boundary of Osaka and Nara Prefectures in Japan, was estimated using satellite remote sensing data. LANDSAT/TM data, sensed in April, June and August, were analyzed, and heat budget terms were compared. The surface temperature, NDVI and surface albedo were calculated from the radiometric data of each band and used in combination with meteorological measurements from neighboring weather stations to estimate heat budget terms. Sensible and latent heat fluxes were derived using the bulk equations for each pixel. The bulk transfer coefficient was corrected using the bulk-Richardson number for each pixel. The moisture availability, a parameter of the bulk equation for latent heat flux, was determined by the analysis of residual variance in the heat budget terms. Averaged values for sensible heat flux in forest area fell within 180-300Wm
-2 and the greatest value was obtained for June. Mean latent heat flux fell within 200-260Wm
-2 and the greatest value was obtained for August. The moisture availability fell in the range of 0.06 (June)-0.19 (April), according to moisture conditions in the forest.
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Wenjing ZHAO, Hidenori TAKAHASHI, Huanchen ZHAO
1997 年 52 巻 5 号 p.
541-544
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
A method has been developed for estimating the filtered narrow band surface albedo using Landsat/TM data. The surface albedo from the filtered range of Landsat/TM is converted to the surface albedo with unfiltered spectral range. The atmospheric effects on each channel are systematically different, because of the different spectral behavior of the atmospheric parameters. As a result, in this study, atmospheric correction has been done in different parameters for visible and infrared channels respectively. The surface albedos of the Kushiro Mire gotten with this method were compared with the observed data in the Kushiro Mire. The results show that the satellite inferred albedos agree well with the diurnal mean of ground observed albedos (with a 3% systematic error). There is a seasonal variation of albedo in the high and low mires, the albedo decreased gradually from April to July and reached its minimum in July, and then it rose gradually from August to October. It is also clear that there is a characteristic pattern of surface distribution according to the vegetation types of this area. The average surface albedos of each type of community are 0.164 for
Sphagnum, 0.175 for
Carex, 0.179 for
Pragmltes and 0.177 for
Alnus. In other words, the albedo in high mire (mainly covered by
sphagnum) is lower than in the low mire (mainly covered by
phragmites and
carex).
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Shenbin Chen
1997 年 52 巻 5 号 p.
545-554
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The objective of this study is to set up a working system for estimating the main cereal crop (wheat, maize, rice) yields and productions over a large area by remote sensing and GIS. Wheat is taken as an example to interpret the improvement of the key links of the technique, such as regionalization for yield and production estimations, extraction of the crop growing area, monitoring of crop growth and development, yield and production estimations, application of GIS. The working system has been carried out on a large area since 1994. It is also useful for monitoring the environment of agricultural ecology under global climate change.
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N. LI, S. HAYAKAWA, W. GU
1997 年 52 巻 5 号 p.
555-558
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
In this study, we found that the most effective spectral reflectance for estimating the dust concentration in snow was mean spectral reflectance of 425-500, which corresponds to Band-1 of Landsat/TM data. The experimental equations for estimating the concentration were expressed in logarithmic form, and the correlation coefficients obtained from the estimated formula were more then 0.89. On the basis of these results, the method can estimate the dust concentration in snow deposited on the ground during winter in the concentration range of 0.5-6.0mg/cm
3.
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Chiharu OKANO, Michikazu FUKUHARA
1997 年 52 巻 5 号 p.
559-562
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The cool and wet summer of 1993 in Tokachi district, Hokkaido, Japan, resulted in damage to sugar beet and caused an overall reduction in yield. Landsat/TM and Mos-1/MESSR images were analyzed for detecting the location and extent of the damaged area. Data for the period of July to September 1993 (alow-yield year), were compared to data for August 1991 (a bumper year).
Yield estimation equations for 1991 and 1993 derived from Landsat/TM data taken on August 29 1991 and those on July 8 corresponded with actual yield. Results showed severe damage in the fields with low soil organic matter. The change in KVI (vegetation index) values was small in July, medium in August and medium in September. No damaged fields were found in the area with higher soil organic matter. In these areas the KVI value was medium in July, high in August and low in September.
The relationships amcng the extent of the damage, the changes of KVI, and soil organic matter content suggested that the production drop was partly due to leaching of fertilizer by high precipitation in addition to damage from the cool and wet summer.
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Suehiro Otoma, Yoshifumi Yasuoka, Tadakuni Miyazaki, Akira Shimizu, Ya ...
1997 年 52 巻 5 号 p.
563-566
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Mosaiced cloud-free images and distributions of the vegetation index for 1986, 1987, 1988, 1987/1988, 1989, 1993 and 1994 were produced from NOAA AVHRR Local Area Coverage (LAC) satellite data in order to monitor the vegetation and land cover conditions in the Southeast Asian region on a macroscopic scale. These images were obtained by applying precise radiometric and geometric corrections which maintained the original 1km spatial resolution.
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Kengo ITO, Kyoichi OTSUKI, Makio KAMICHIKA
1997 年 52 巻 5 号 p.
567-570
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The analysis of the perpendicular structure of vegetation by remote sensing would provide valuable information for classification of vegetation and estimation of the environment. The purpose of this paper is to investigate the relationship between perpendicular structure of vegetation and spectral reflectance in visible and near infrared. The spectral reflectance is measured in the range of 400nm to 2500nm at intervals of 1nm by changing the number of overlap leaves, perpendicular space between leaves, angle of leaf, incident angle and sensor look angle.
The results indicate the following features. First, spectral reflectance in red and near infrared increases with increasing the number of overlap leaves and narrowing the perpendicular space between leaves, but visible rays are not affected by these factors. Secondly, when the perpendicular space between leaves is wide, the spectral reflectance is affected by incident angle. Thirdly, the changes of spectral reflectance differ with leaf angle. These results lead to the conclusion that the relationship between those parameters is complex.
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Haruhiko YAMAMOTO, Seiji HAYAKAWA, Tamiko TSUTSUMI, Yoshiyuki HONDA, Y ...
1997 年 52 巻 5 号 p.
571-574
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Rice Leaffolder
Cnaphalocrocis medinalis GUENEE is a major pest of the rice crop in the western part of Japan. We investigated the relationship between the percentage of damaged leaf area and the surface temperature using thermal infrared imagery and the transpiration rate using a porometer at the early and late ripening stage.
When the percentage of damaged leaves was high, the transpiration rate was low and the surface temperature was high. The percentage of damaged leaf area=9.05+13.1X (r=0.976, p<0.01). Where X was the difference of the surface temperature and the air temperature. However, the percentage of damaged leaf area by
Cnaphalocrocis medinalis was estimated by surface temperature using infrared radioactive thermometer.
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Ryuichi SHIROOKA, Kazushige YAMADA, Tomoyoshi HIROTA
1997 年 52 巻 5 号 p.
575-578
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
A statistical method is presented for the estimation of global solar radiation at the ground surface. Daytime averaged “infrared” data taken by a geostationary meteorological satellite are applied to estimate the daily amount of global solar radiation around the tropics. In order to use the infrared equivalent blackbody temperature (IR T
BB) data as an indicator of cloud amount and activity in the daytime, the satellite data on each point of a 0.1×0.1 degree grid are averaged from 06 to 18 LST in one hour intervals. Surface solar irradiance is evaluated with the averaged T
BB and a calculated solar radiation at the top of the atmosphere. Results are compared with measured radiation values over the ocean and on islands in the tropics. From the results of the estimation, the correlation coefficient is 0.88 and the root mean square error is 2.41MJ/m
2 for daily estimation over the ocean, and 0.79 and 2.78MJ/m
2 on islands.
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Muneharu Sato, Etsuji Ishiguro, Shinsuke Fujita, Koichi Hirata, Takaka ...
1997 年 52 巻 5 号 p.
579-582
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The methodology of biomass estimation of forest areas in Japan has heavily depended on the mesh method. The method, however, demands a large amount of time-consuming labor to attain a reliable accuracy. Therefore, we have been working on the use of satellite data to assess the biomass as one of the alternatives to the conventional method.
As the first step in our research, we put our efforts into identifying specific objects on the ground and into evaluating their quantities. So far we have succeeded in estimating crop yield and volcanic ash deposits from the satellite data. They are, however, at level ground showing rather small variations in spectral reflectance.
The next step is to clarify the topographic effects on the biomass estimation of mountainous areas. Since the system to receive and analyze NOAA/AVHRR data was installed at United Graduate School of Agricultural Sciences, Kagoshima University in 1995, attempts have been made to use their data for those purpose.
NOAA data have been conventionally used to study surface properties not requiring high resolution because of their low resolutions, 1.1
km at best. The satellites, however, can supply the data four times a day. Therefore, in this study, some attempts were made to use NOAA data efficiently to estimate the biomass of the mountainous forest areas in Japan. The results suggest that the data supplied by NOAA can be used to estimate biomass of the forest areas with sufficient reliability.
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Jun Hayasaka, Nobuhiro Matsuoka, Hisashi Kon, Keiichi Nakayama
1997 年 52 巻 5 号 p.
583-586
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
From September 27 to 28, 1991, Typhoon 9119 struck Kyushu Island, Japan, and wind damage to trees occurred around the northern part of this area. In the forests, we used two scenes of Landsat TM data, obtained on September 21, 1990 (before the damage) and March 5, 1993 (after the damage). The ground truth datum of the damaged forests is “Damaged forest map”, which illustrates the fraction of damaged trees (100%, 80%, 60% and others). Specifying the location of the forest, we adopted the maximum likelihood method for the TM data. To assess the intensity of the damage, we calculated a Normalized Difference Vegetation Index (NDVI). Before the damage, there were smaller differences in the averaged reflectance of each band and NDVI than after the damage among the damaged forest classes (100%, 80%, 60% and others). After the damage, there were differences in the average reflectance of band 5 (1.55 to 1.75μm) and band 7 (2.08 to 2.35μm) among the damaged forest classes. Therefore band 5 and band 7 were useful to detect damaged forests. Since the reflectance of the band 5 and band 7 were increased after the damage and the reflectance of both band 5 and band 7 are related to the water contents of the plants we presume that the damaged forests suffered water stress
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Hiroshi Tani, Seiji Hayakawa, Ikuo Horiguchi
1997 年 52 巻 5 号 p.
587-590
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
A method of estimating surface net radiation using visible, near-infrared and thermal-infrared data from the Advanced Very High Resolution Radiom eter (AVHRR) onboard NOAA-11 was examined. Shortwave radiation balance was evaluated from measured incident solar radiation and surface albedo estimated by the use of visible (Ch1) and near-infrared (Ch2) channels of AVHRR. Longwave radiation balance was evaluated from surface temperature estimated by the use of thermal-infrared channels of AVHRR, and atmospheric radiation calculated from radiosonde data. The derived surface net radiation was compared to that collected with ground-based instruments at a forest and a sand dune during several days coincident with NOAA-11 passing over. Overall, satisfactory results were obtained. The results imply that net radiation maps of a large area can be constructed by combining ground-based and remote-sensed data. In order to improve the albedo estimation accuracy, it is necessary to apply a bidirectional reflectance model to the estimated isotropic albedos.
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An Shunqing, Liu Gengshan
1997 年 52 巻 5 号 p.
591-599
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
During the growing season of winter wheat, the precipitation amount in the North China Region, where the water resource is seriously insufficient, amounts to only 100-250mm and can not meet the demand of winter wheat.
This paper demonstrated the geographic distribution of the difference between the water demand and supply of winter wheat in different climatic years (guaranteed probability of precipitation during growth period of winter wheat at 75%, 50% and 25% respectively). The water differences were calculated with a field water balance equation.
To determine proper irrigation time and amount, and to ensure stable and high production of winter wheat with limited water resource, Monitoring Forecasting Assessing Decision-Making Service System (MFADSS) of soil moisture stress of winter wheat was constructed on the basis of experimental research on the relationship between soil moisture and winter wheat. The techniques and functions of each subsystem are also demonstrated.
The system was applied to more than 3 million ha. of winter wheat in 90 counties of the North China Region. Accuracy of the decision of the irrigation reached about 95 per cent. The water-saving and high yield function of the system was shown clearly. Obvious social, economical and ecological benefits were obtained during 1990-1995 under the support of the government.
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Masatoshi AOKI, Yoshiaki HIDESHIMA, Takashi MACHIMURA, Norio OBASE, Ka ...
1997 年 52 巻 5 号 p.
601-604
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The authors developed a simple model to estimate the long term transition of soil moisture tension (daily average pF value at 15cm depth in soil) for the next day (PFi+
1) by the following formula, where PFi, Ei, Pi and PFmin are, pF value, daily total amount of evapotranspiration (mm·day
-1), daily amount of precipitation (mm·day
-1) and the minimum PF value of the field after heavy rain fall, respectively: PFi+
1=α(Ei-Pi)+β·PFi+γ (when calculated PFi+
1 is larger than PFmin); PFi+
1=PFmin (when PFi+
1 calculated by above equation is less than or equal to PFmin). The constants α, β and γ for the beet field in 1993 were 0.025a, 0.876 nd 0.25, respectively. PFmin was 1.9 for three crop fields in 1993. The standard estimate errors in PF by the equations were less than 0.2 for three crop fields in 1993.
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Masatoshi AOKI, Takashi MACHIMURA, Yoshiaki HIDESHIMA, Norio OBASE, Mi ...
1997 年 52 巻 5 号 p.
605-608
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
A system is developed using a mobile telephone to continuously measure evapotranspiration in remote fields over long period and transmit the collected data. The necessary electric power for the system is supplied by a propane gas-driven small DC generator (approximately 24W). Evapotranspiration and micrometeorological elements are automatically measured every minute by a 16-channel data logger. After 10-minute averages are calculated the data are stored every ten minutes in IC card which has storage capacity of 11 days of data. The software for transmitting data, calculating evapotranspiration rates, printing graphs and others is written in BASIC. The average time required for transmitting data for one day was approximately 4min. The functions and applicability of the system were examined for a total of approximately 20 months from 1992 to 1994. It was found that the system developed is simple to operate and effective for collecting data in remote fields.
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Hiroaki Okabe, Takuya Marumoto, Tsugio Ezaki, Kazuo Yamamoto
1997 年 52 巻 5 号 p.
609-612
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Selection of effective ECM (ectomycorrhizal) fungi are very important for inoculation and infection to pioneer trees. The candidates of effective ECM fungi for revegetation collected at volcanic and at poor granite sites in Japan were as follows;
Pisolithus tinctorius f.
tinctorius, P. tinctorius f.
turgidus, P. tinctorius f.
pisocarpius, Astraeus hygrometrics, Laccaria amethystea. Particularly, the elementary species
P. tinctorius showed the widest host range and was the most common candidate of all. This fungus was associated with
Pinus densiflora, Pinus Thunbergii, Betula Ermani, Betula Maximowiczii, Alnus firma, Larix leptolepis and probably
Quercus serrata. Above all the association with
Larix and
Betula trees appeared to be efficient for the revegetation in a cool temperate zone.
Basidiospore and vegetative inocula of
Pisolithus were effective for young seedlings and especially 1-year-old seedlings in volcano and granite stands. Introduction of ECM fungi to each site brought about good results for enhanced survival rate and increased growth of seedlings, especially just after sprouting, which were further promoted by using a mulching sheet made of non-woven polyester fiber.
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Takuya Marumoto, Seiji Hayakawa, Tsugio Ezaki, Kazuo Yamamoto, Hiroaki ...
1997 年 52 巻 5 号 p.
613-616
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
From the experiments at model and actual slopes, several effective functions of a mulching sheet (MS) were indicated on soil erosion and reforestation as follows: 1) drainage of flow water, 2) reduction of muddy water, 3) prevention of soil erosion, 4) decrease of drought damage to soil, 5) decrease of the fluctuation of temperature and moisture in surface soil, 6) reduction of wintry withering, 7) promotion of plant growth, 8) environmental conservation of root zone, 9) environmental improvement of soil microorganisms.
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Tsugio Ezaki, Takuya Marumoto, Seiji Hayakawa, Hiroaki Okabe, Kazuo Ya ...
1997 年 52 巻 5 号 p.
617-620
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
In order to investigate the possibility of utilizing a combination of a mulching sheet (MS) composed of Polyester random fiber web as the main material and mycorrhizal fungi (MF), effects of their utilization were surveyed for 2-4 years on the growth of
Pinus thunbergii Parl. and
P. densiflora Sieb. et Zucc. at model and actual slopes. At plots where spores of
Pisolithus tinctorius Coker et Couch f.
tinctorius (Pt) were dispersed as MF and MS were applied after
P. densiflora was seeded, the stem diameter at ground level and planting stock height showed greater values from the first year, compared with those at control plots.
The growth at the experimental site belonging to Ehime University where seeds of
P. densiflora were incorporated into the MS showed greater values of stem diameter at ground level and planting stock height from the first year, compared with those at control plots. MS were stuck at the site where 4 years had elapsed after
P. thunbergii was planted at Mt. Tanakami in Ohtsu, Shiga. An increase of 66-494% was shown in the stem diameter at ground level and tree height of
P. thunbergii, compared with those of control plots during 4 years. At the Nojiri River experimental site on Sakurajima Island in Kagoshima where
P. thunbergii of a two year-old planting stock was planted after MS were stuck,
P. thunbergii showed a strong tolerance against sulfurous acid gas (SO
2 gas). From these findings, it was estimated that MS and MF were effective for the regeneration of forests devastated by various causes.
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Sen-Hsiung Hsu, Chia-Chun Wu
1997 年 52 巻 5 号 p.
621-628
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
The effectiveness of a mulching material for conserving soil and water is not only dependent upon the material itself, but also controlled by the microclimatic environment that the material is subjected to; especially for bio-degradable materials. Therefore, the objectives of the study are (1). to monitor the soil loss and surface runoff produced from tested mulching materials and (2). to monitor the microclimatic characteristics between mulching materials. A variety of mulching materials was used in this study; including Bahia grass residue, chaff, Japanese silver grass residue, tree branches, and synthetic multi-function filter. Two outdoor experimental sites with the slope steepness of 9% and 60% respectively were used to collect data.
Field data indicate that Bahia grass residue and multi-function filter were very effective in soil loss reduction on the 60% slope; whereas, Bahia grass residues, chaff, and Japanese silver grass residue could greatly reduce soil losses on the 9% slope. Because of the weak contact that multi-function filter provided to the soil, under-Tilling problem was found on sites. Bahia grass residue and chaff were the best ones among test materials in conserving moisture.
Microclimatical characteristics that test materials created could provide reasonable explanations to moisture conservation. Because of the close contact that it produced, Bahia grass residue had the highest variation of 28.7°C in ground temperature and 18.5°C in air temperature beneath the mulch. On the other hand, chaff had the lowest variation of 8.0°C and 10.0°C in ground and air temperatures beneath the mulch, respectively. Even though chaff has limited capacity withholding moisture, the spaces between chaff grains actually form small air pockets that affect the heat transfer within chaff mulch. In addition, chaff mulch had the greatest Albedo of 30.9%. Hence, the ground and air temperatures beneath the chaff mulch did not vary correspondingly with the temperature above the mulch. With the assistance from air pockets between grains, trapped moisture can not easily get out of the micro-environment. Therefore, chaff mulch had highest relative humidity of 86% among all test materials.
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Kiyoshi Ozawa, Yang Ge Gulinur, Ryoji Sameshima
1997 年 52 巻 5 号 p.
629-632
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
To save water and promote vegetable growth, we conducted experiments at the Fukang Desert Ecosystem Observation and Experiment Station of Xinjiang Chinese Academy of Sciences in summer 1995. Effects of newly developed practices, furrow bottom seeding (FBS), folia water spraying and row cover, were confirmed.
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T. MAKI, M. DU, R. SAMESHIMA, B. PAN
1997 年 52 巻 5 号 p.
633-636
発行日: 1997年
公開日: 2010/03/16
ジャーナル
フリー
Arid and semi-arid lands account for one third of the total surface area of the earth. Desertification is now prevailing and is based on the decrease of rainfall due to climatic change. However, it is mainly based on the adverse human impact of population increase, i. e., over cultivation, grazing, deforestation and consumption of water resources.
There are various countermeasure against desertification in arid lands of the world. In this paper, we demonstrated the situation of sand erosion and movement of sand dunes, and we propose the prevention method by using windbreak facilities, i. e., windbreak forests and windbreak nets, straw-mat networks and so on.
We also demonstrate that the use of windbreak facilities alleviated the adverse effects of wind speed, air temperature, soil temperature and relative humidity. Under very dry condition, it was recognized that wind erosion and the movement of sand dune could be prevented and adverse meteorological conditions could be alleviated by the use of windbreaks.
Agricultural fields can be protected by the windbreak facilities and, finally, desertification could be prevented in arid lands.
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