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Table of Content

    15 June 1982, Volume 1 Issue 2 Previous Issue    Next Issue
    ECOLOGICAL BALANCE AND GEOGRAPHIC RESEARCH OF AGRICULTURE II THE CONCEPT OF ECOLOGICAL BALANCE AND ECOSYSTEM AND SUCH TERMS AS NATURAL RESOURCES,ENVIRONMENT, PHYSICAL PLANNING ETC.
    Huang Pingwei
    1982, 1 (2):  1-7.  doi: 10.11821/yj1982020001
    Abstract ( 649 )   PDF (647KB) ( 798 )   Save
    The term ecological balance or its equivalents may not exist in many biolo-gical and ecological books and dictionaries, but their pages are full of treatments on energy flow, nutrient cycling, trophic levels, biotic potential and environmental resistance, balances between vegetation, herbivores and carnivores, and between competing species,etc. This signifies what is important is not the term, but investigations with the concept in mind on the processes at work in ecosystems. As most of the processes are governed by the law of conservation of energy and matter, serious studies are more often than not characterized by quantification on a sound observational and experimental basis. As an example, the CO2 transfer between the atmosphere and terrestrial ecosystem is discussed in brief.The most important measure for this purpose is the net ecosystem production of carbon=net primary production minus heterotrophic respiration, a figure varies widely with a host of factors. The scarcity of data can hardly bring out a global picture. In recent publications in China, one ton of CO2 per hectare per day has repeatedly been quoted as a representative estimate of absorption of broad leaved forests during the growing season. In the light of present knowledge of carbon cycle, the acceptance of this would lead one to go amis. A fashionable term and superficial talk are of little use to problem solution. Much of geographic research in China should be focussed on agricultural problems. The notions of ecological balance and ecosystem are in close connection with this pursuit and should help geographers to correlate and coordinate various components and processes of the agricultural industry. Also in vogue are such terms as utilization and conservation of natural resources,environment protection, environmental system, physical planning, etc. In conceptual framework, they are not synonymous and investigations are differently oriented. But there is no great difference in the majority of information to be acquired. A cursory survey of geographic publications-since the latter half of the nineteenth century will not fail to find these concepts at least in their rude form, although geographers have contributed not much in their elaboration. In the geographic studies of agriculture, we have to learn from neighbouring sciences,weld together the foremention-ed concepts and broaden our scope to include physical, biological, economic, social and environmental implications. Our work should provide answers to two questions. (1) for any piece of land, which use or uses would offer the greatest advantages? and (2) for any use or uses of a piece of land, how can the potential productivity be retained or improved?
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    POSSIBLE IMPACTS OF CLIMATIC VARIATION ON AGRICULTURE IN CHINA
    Zhang Jiacheng
    1982, 1 (2):  8-15.  doi: 10.11821/yj1982020002
    Abstract ( 766 )   PDF (639KB) ( 1540 )   Save
    In this article the potentiality of agricultural climatic resources is approximately estimated. 1℃ temperature change and 100 mm rainfall change are taken as units of climatic variation. In the case of 1℃ temperature change, the potentiality of agricultural climatic resources might have a change about 30 million tons of grain in magnitude; in the case of 100 mm rainfall change, the change of potentiality would be 80 million tons. Besides, analysing the greatest amplitudes of climatic change in historical and geological times, the author succeeds in giving some preliminary deductions of possible impacts of climatic variation in different time scales, which may be summarized as a climatoecological series.
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    AGROCLIMATOLOGICAL ANALYSIS OF HEATING LOAD AND VENTILATION REQUIREMENT FOR GREENHOUSES IN CHINA
    Lu Qiyao
    1982, 1 (2):  16-31.  doi: 10.11821/yj1982020003
    Abstract ( 511 )   PDF (1076KB) ( 955 )   Save
    Heating and ventilatioo are two important agrotechniques for regulating and controlling the micrometeorological environment in the greenhouses, and the data of heating load and ventilation requirement for greenhouses are necessary in greenhouse planning and management and in more profitable use of energy in greenhouse cultivation.
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    NONLINEAR RELATIONSHIPS OF CONCENTRATION FOR A WATERSHED AND A METHOD OF DEALING WITH THEM
    Liu Changming, Wang Guangde, Wu Kai
    1982, 1 (2):  32-38.  doi: 10.11821/yj1982020004
    Abstract ( 622 )   PDF (483KB) ( 664 )   Save
    The paper briefly reviews the research work on nonlinear relationships between rainfall and runoff for a watershed at home and abroad. According to experimental data of overland flow on field in northwest regions of China and those of channel and laboratory watershed in the laboratory,there are H groups that consist of 316 events on field and 2 groups that consist of 234 events in laboratary. Nonlinear relationships are further proved and the relationships between the index of nonlinearity and characteristics of watershed are preliminarily analysed, the mathematical formula of which is as follows.
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    ANALYSIS OF RECOGNIZING LAND COVER OF A WATERSHED WITH MULTISPECTRAL REMOTE SENSOR DATA
    Ling Meihua, Liu Zhensheng
    1982, 1 (2):  39-50.  doi: 10.11821/yj1982020005
    Abstract ( 573 )   PDF (886KB) ( 866 )   Save
    The launching of land satellites makes it possible to make a quick and accurate study of land cover of a watershed, which is of great significance in hydrography.The present article takes Da-Wen River in the lower reaches of the Huang He River as an example, and selects seven kinds of typical land cover, mountains covered with dense forests, mountains covered with sparse forests, hills covered with grass and bush, hilly fields, plain fields, water and city. By the use of the digital data of films of the second land satellite of Oct.31, 1975 in 4 bands and the digital data of photograph of the third land satellite of April 1, 1978, MSS7, land cover of a watershed was analysed in a quantitative way and its was result compared with that of visual interpretation.
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    GEOGRAPHICAL DISTRIBUTION OF SELENIUM CONTENT OF GRAINS IN CHINA
    Wang Mingyuan
    1982, 1 (2):  51-58.  doi: 10.11821/yj1982020006
    Abstract ( 1076 )   PDF (561KB) ( 1189 )   Save
    Selenium is an essential trace elenint to animal and man, but abnormal content (deficiency or excess) of selenium in environment is harmful. Selenium in environment has an influence on animal and man by means of biogeochemical food chain, rock-soil and water-plant-animal and man. Grain is the key link of them.This paper studies geographical distribution of selenium content of grains (wheat, corn and rice) in China and its relation to geographical epidemic of white muscle disease of animal and kashin disease and Kaschin-Beck's disease of man, which are endemics with relation to selenium deficiency in environment, by the method of statistical plotting.Statistics shows that frenquency distribution of selenium content of grains belongs to the approximate longnormal distribution. Therefore, according to' classifica-iton of equal ratio,different selenium content of grains is sorted out into three classes; high, medium and low, and a distribution map of selemium content degree of grains in China has been plotted. As shown in the map, grains containing high selenium mainly grow in the Northwestern part of China, next in Enshi county in Hu-bei province and Ziiyang county in Shaanxi province (There are areas in these two counties where selenium toxicosis occurs in livestock and man). Grains containing medium selenium are distributed in Southeast China, Northwest China and Northeast China plain, North China plain, Fenhe basin, Weibe plain and Sichuan basin. Grains containing low seleniumare distributed in the Lesser Hinggan Mountains, the Changbai Mountains, the Luzhong Mountains, the Loess plateau, the Qinling Mountains, the Daba Mountains, the eastern part of the Qinghai-Tibet plateau and the Qaidam Basin. It is outlined that low selenium zone is mostly distributed in mountainous and hilly regions in the so-called transition zone situated between the dry desert and steppe zone of the Northwest China and humid-hot evergreen forest zone of the Southeast China.Geographical distribution of the above-mentioned three endemics is fundamentally in accordance with that of grains containing low selenium. A difference of selenium mean content of grains between endemic areas and nonedemic areas is statistically very significant.
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    A PRELIMINARY STUDY ON THE HOLOCENE TRANSGRESSION ON THE COASTAL PLAIN ALONG THE NORTH-WESTERN BOHAI BAY
    Wang Yiman
    1982, 1 (2):  59-69.  doi: 10.11821/yj1982020007
    Abstract ( 579 )   PDF (971KB) ( 876 )   Save
    The plain at the lower-reaches of Jiyun and Chaobai River to the north of Hai-ho River along the north-west coast of Bohai Bay is a lowland on which rivers meander and shallow lakes scatter. The Holocene transgression here was rarely systematically studied before because of the discontinuance of the cheniers that usually appear south of Haiho River.Three cores were drilled after the field observation. The association of spore-pollen and mollusc and foraminifer in the strata was analysed. It shows that the climate fluctuated during the period of the Holocene from cold to damp and hot and then became cool. The sedimentary environment changed correspondingly as limnetic-fluvial-fluvial-marine-limnetic-fluvial. So the Holocene stratum can bedivided into three layers with the lower depth of 17-20m., 12-15m.and 2-3m.respectively. The Holocene transgression took place at the stage of Atlantic when the climate was optimum and the sea level rose in the Middle Holocene.According to the marine sediment and the foraminifer association combined with the relief and the distribution of underground saline water, etc., the limits of the Holocene transgression on this plain are drawn from east to west as follows. Anniou-dian in Luannan County, Hongqiao in Yutian County, the south of Zhangguzhuang in Baodi County, eastern Yungqing County and Xinglunggung in Werian County. The outline of the transgressive extent on the plain along northern Bohai Bay is then linked as a whole.There are crowded and well-developed oyster reefs and shells buried just below the land surface in the north-west coastal plain.It presents a contrast between oyster reefs and cheniers on the west coastal plain. The difference is due to the different dydro-dynamic of river and sea. On the north-west coastal plain, rivers were small with clear waters. The tides and waves were weakened in this small bay inside the Bohai Bay.All these provided a very good ground for the growth of the oyster reef although the lack of high energy of the coast made it impossible for chenier to be formed.
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    APPROACH TO AN ELECTRICAL MEASUREMENT OF LOW-DISCHARGE IN THE SIMULATION EXPERIMENT OF BAINFALL-BIINOFF
    Fang Xiang
    1982, 1 (2):  70-77.  doi: 10.11821/yj1982020008
    Abstract ( 550 )   PDF (567KB) ( 821 )   Save
    The present paper deals with an elementary principle of a new measurement of runoff with very low discharge by means of resistance measuring-flow, and the nonlinear Flow-Voltage relationships with the resistance measuring-flow. A method of linearization handling is provided to make the Measuring-Runoff Flume in a better linear relationship. The analysis of dynamic response charactertics of Resistance Measuring-flow Flume is based on system dynamics theory, as a result, system parameters ωn and ζ are obtained for judging regulating-storage of measuring-flow device' The Measuring-flow Flume has been applied to measure small discharge in the Hydro-logic Runoff Laboratory. As it belongs to instantaneous flow-rate measurement method, the runoff hydrography measured is very clear as regards its duration, peak discharge, lag of time, and relevant parameters. In addition, the device has a higher stability of electronic circuit and better signal-to-noise ratio, and the problem of electolytic action at electrodes surface due to impurity of the water has been solved, so it is more convenient to make research of the rainfall-runoff relationship in laboratory. Finally, in this paper a comparison of cumulative sum of hydrography from Resistance Measuring-flow Flume with cumulative water-volume-method is given, and satisfactory results have been obtained.
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