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Factors Influencing Environmental Change
The fundamental cause of environmental change in the Sanjiang Plain appears to be related to the alterations in the pattern of atmospheric circulation. Anthropogenic factors are also important.
Historically in the Sanjiang Plain wet and dry periods alternated, each lasting about 20 years (table 7.7). This local pattern is similar to those of Heilongjiang Province and North China6 7 and suggests that the general climatic changes of the Sanjiang Plain are subject to the control of large-scale air circulation. The extraordinary drought of 1975-1979 occurred within a dry period, which, in turn, is closely related to the increase in latitudinal air circulation and to the decrease of both meridional circulation and blocking high pressures. It is also related to the weak Pacific high-pressure system, the location of which has shifted eastwards, thus deflecting both the southerly lowpressure systems and the typhoon tracks further eastwards than usual.
However, the decreases of precipitation in various places of the Sanjiang Plain have been greater than that of Harbin, located in the central part of the Songnen Plain (table 7.8). The decline of precipitation also varies in magnitude within the Sanjiang Plain itself, which is located in the same general climatic zone. The rate of decrease has been greater in such places as the Youyi State Farm and Fujin County, where large-scale reclamation and drainage of water have more severely altered the natural vegetation, than in Hulin and Baoquing, where the vegetation change has been less drastic. This suggests that deforestation and large-scale reclamation of wetlands and meadows intensify environmental desiccation.
Micro-climatic changes in swamps and swamp-meadows before and after reclamation also provide further evidence in support of the above conclusion. Based on the observations along the River Qihulin, the daily average surface temperature on reclaimed land tilled in summer was 2-5°C higher than that of the swamp-meadows. Summer temperatures on reclaimed land at a depth of 40 cm were 18-20°C, compared with temperatures of only 6-8C at the same depth in the swamps (fig.7.8).
TABLE 7.7 Climatic Cycles in the Sanjiang Plain, 1876-1978 (Based on: (a) historical records since 1870,11 (b) changes in depth of Lake Xinghai; (c) recent climatic data; and (d) from Xiao Xinagan Liang)
|Moisture level||Humid||Slightly dry||Humid changer to dry||Humid||Dry||Humid||Dry||Humid||Dry|
|Temperature||Cold||Cold||Warm||Cold||Wram||Cold changed to warm||Warm||Cold||Wram|
(Based on: (a) historical records since 1870,(b) changes in depth of Lake Xinghai; (c) recent climatic data; and (d) tree-ring data from Xiao Xingan Ling)
TABLE 7.8. Precipitation Changes in Heilongjiang Province
|Station||Average annual precipitation 1975-1978 (mm)||Average annual precipitation 1958-1978 (mm)||Difference (mm)||Trend equations since 1958|
|Jiamusi||389.4||542.7||- 153.3||X=654.9-8.31 t|
|r = - 0.625a|
|X= 587.4 + 1.404 t- 0.358 t2|
|Luobei||426.2||559.2||- 132.9||X= 656.0 9.23 t|
|r = - 0.436b|
|Fujin||382.5||559.1||- 146.6||X= 627.5-9.82 t|
|r = - 0 495b|
|Youyi||351.3||506.3||- 155.0||X= 613.4 9.69 t|
|r = - 0.548b|
|Hulin||456.8||575.8||- 119.0||X= 640.2-6.13 t|
|r = - 0. 454b|
|Baoqing||415.3||540.3||- 125.0||X = 610.2-6.69 t|
|r = 0.289|
|Harbinc||421.5||506.2||- 84.7||X= 597.2-6.75 t|
|r = - 0.535a|
|X= 575.4-1.73 t-0.785t2|
Note: X = Precipitation; t = Years; r = Correlation coefficient; a = 1% significance level; b = 5% significance level; c = Outside the Sanjiang Plain:
From the perspective of energy conservation and transformation, environmental change is the inevitable result of the changes in water and heat balance. In the equation of radiation equilibrium, the albedo of the surface depends on the nature of the surface. Reclamation in the Sanjiang Plain has transformed the original surface of forest, meadow. and swamp-meadow into cultivated land on which the exposed dark soil now has a lower albedo. As a result of changes in the albedo and in the thermal property of the soil, the surface temperature of the cultivated land became higher than that of the swamps.
Thermal changes affect changes in the water balance. Swamps and swamp-meadows have a higher evaporation power than does cultivated land, as a result of both their abundant water surface and the transpiration of their dense vegetation cover. According to our comparative observation, the evaporation power of swamp-meadows was 2.2-2.5 times higher than that of unplanted, cultivated land (table 7.9).
The evaporation capacity and humidity of air are closely interacting factors. At the surface, in daytime, the relative humidity of the swamps is 7-13 per cent higher than that of cultivated land. The average annual relative humidity in Fujin County in the last five years was 6.2 per cent lower than that in 1953-1957, before large-scale reclamation started. The changes in atmospheric humidity exert a further, although minor, influence on the amount of precipitation.
TABLE 7.9. Evaporation Power of Swamp Meadows Before and After Reclamation
|Time||Evaporation capacity (mm)|
of wafer surface
Fig. 7.8. Comparison of Summer Soil Temperature between Swamps with Peat Bog Soil and Tilled, Reclaimed Land, at 5 a.m. and 2 p.m.
Decreased river discharge in this region is related to the declining precipitation and to the hydrologic functions of the swamps. In the Sanjiang Plain the porosity of the grassroot layer of the swamps reaches 72-93 per cent, and its maximum water-holding capacity is 149-552 per cent. In addition, the water-holding capacity of the herbaceous peat is 400-800 per cent. and that of the moss peat is 1,000 per cent. Thus, the swamps function as an enormous "biological reservoir; " when dry a large quantity of precipitation is stored in the grassroot and peat layers, giving the swamps a lower rate of discharge than cultivated land (table 7.10). The runoff coefficients of the Naoli Basin and the Bielahong Basin also indicate that the greater the swamp rate, the smaller the annual runoff coefficient during the dry season (table 7.11).
Principles and Recommendations for the Development of the Sanjiang Plain Region
Natural forces and human activities that have rapaciously plundered renewable natural resources have wrought major changes in the environment of the Sanjiang Plain. As a result of inadequate comprehensive planning and a lack of plan enforcement, indicators of environmental deterioration have emerged. Drought periods are mainly influenced by atmospheric circulation, whereas changes on the land surface are of secondary importance. Floods and waterlogging will still occur, but meanwhile the drought problem continues to intensify. Although many environmental problems remain localized, those such as wind erosion and desertification, in areas north of the River Songhua, and water and soil erosion will become more widespread if left unchecked.
TABLE 7.10. Comparison of Runoff between Swamps and Cultivated Land
TABLE 7.11. Comparison of Runoff Coefficients of the Bielahong and Naoli River Basins
To prevent further environmental deterioration in the Sanjiang Plain, to solve its resource problems scientifically, as well as to establish a rehabilitated environment that will benefit future generations and yet still meet the requirements of China's modernization programmes, the principles of resource use and management discussed below must be correctly understood and put into operation.
1. Natural Conditions should be Improved through a Better Understanding of Nature
The underlying task in the Sanjiang Plain region is to improve the environment with the help of science, technology, and human efforts, and especially by better understanding nature. Different environmental systems may appear in a single natural zone as a result of distinct human activities. Only through an accurate assessment of these activities can sound policies for the development, restoration, and management of the natural resources of the Sanjiang Plain emerge.
2. The Concept of Regional Development should be Based on the Laws of Nature and Economics
Regional development should be viewed comprehensively, and include all aspects involved in converting natural into man-made ecosystems, based on the laws of ecology and economics. The development of the Sanjiang Plain must be accomplished via careful and sound planning that accommodates both the reclamation and incorporation of virgin land as well as the management of the 3.3 million ha that has previously been reclaimed for cultivation. In planning the development of this region, four basic ideas should be explored: (a) maximization of the volumes of biomas derived from development; (b) use of the ecosystem approach; (c) maximization of the productivity of labour; and (d) maximization of the efficiency of land use and land productivity.
3. Development Policy for the Sanjiang Plain should be Based on Controlled Local Development
The limited funds available for the development of this region must be put to the best possible use. However, what this use is is open to debate. Some suggest that reclaimable areas should be reclaimed rapidly, while the climate is still dry, and used first for grain production: other developments could be considered later. An alternative viewpoint is that no further reclamation should occur until swamps reclaimed earlier are used more efficiently, and so funds earmarked for reclamation would be better used to strengthen existing farms and for reafforestation.
The best approach to developing the Sanjiang Plain region would be to make, implement, and monitor a comprehensive development plan aimed at improving the ecosystems of the entire region. Development of the region should occur area by area, following the comprehensive plan. Thus the development of the whole region would be controlled, and selected local areas would combine land reclamation with the scientific management of resources.
4. Determination of the Basic Geographic and Administrative Unit for Development
The size of the basic geographic and administrative unit best suited to the development of the Sanjiang Plain is of fundamental importance since it will affect settlement size and the development of industry, trade and agriculture. At present the Production Team of the State Farm is the basic unit of production, most having 990 ha of land. Some teams are experimenting with larger areas, ranging from 1,980 to 6,600 ha. Research shows that People's Communes and State Farms, rather than their Production Teams, should be the basic units where industry, trade and agriculture should be developed because greater savings on investment could be realized at these levels, and small towns and intermediate cities could develop. It would be appropriate for these units to develop a diversified economy with crop raising as the major activity.
5. Comprehensive and Balanced Use and Development of Natural Resources
The correct determination of the proportion of land devoted to various uses to ensure balanced development is of fundamental importance. Since the large-scale reclamation of the Sanjiang Plain began. the overemphasis on grain has greatly and unduly reduced the proportions of other types of production. Statistical data from various State Farms show that the value of forestry comprises a mere 0.75-1.06 per cent of the total value of agricultural output, and that of animal husbandry constitutes only 3.5-11 per cent.
The Sanjiang Plain should be developed so that agriculture, forestry, and animal husbandry are properly balanced, interdependent, and mutually beneficial. The present irrational structure of primary production must be changed. In the forestry sector, a network of windbreaks should be established and more trees should be planted as soon as possible. In the meantime, forests should be established for the production of timber and fuelwood as well as for water and soil conservation. Existing forests must be protected and renewed.
In animal husbandry, the extensive meadows of Deyeuxia angustifolia in this region and those where Carex spp. is dominant must be fully utilized. Agriculture and animal husbandry should be developed in combination, with greater efforts devoted to the latter. The existing reedbeds and water bodies should be protected for the development of complementary occupations and fisheries.
The relative proportions of agriculture, forestry, and animal husbandry must be determined according to local conditions. In the Sanjiang Plain, 45-50 per cent of the total area should be cultivated. About 20 per cent of the area should be devoted to animal husbandry, 10-15 per cent to forests, 10-15 per cent to complementary production and swamp reserves, and 3 per cent to water bodies. This proposed allocation of land use takes into consideration the natural conditions existing prior to reclamation. Although the area of paddy fields should be increased, a proper proportion of pasture and a higher ratio of forest cover should also be maintained to prevent further environmental deterioration. In addition, the gleyed meadow soil and the meadow-swamp soil have a comparatively high potential fertility and can be partially reclaimed. The reclaimed sandy burozem is prone to desertification and should be returned entirely from farming to either forestry or animal husbandry. Part of the reclaimed Baijiang soil with very low fertility should also be returned to animal husbandry. Cultivated land with slopes in excess of 3 degrees and which has suffered from serious water and soil erosion should be returned to forestry. On the other hand, in view of the national need to increase grain production and the present productive capacity, the area of cultivated land in the Sanjiang Plain should not be too little.
6. The Policy of Water Management should be Adapted to Local Conditions
The quality of the Sanjiang Plain environment depends basically on the management of its water resources. Various propositions about water problems have been advanced. On the basis of historical data, it has long been proposed that the major task is the elimination of waterlogging, especially through drainage, though there are few complete and effective drainage projects. On the basis of recent drought conditions others have argued that the environment has become so dry and that the principal objective of water management should be to deal with drought. However, the total irrigated area remains irrationally small.
In the plain region there are numerous waterlogged depressions. Whereas drainage should never be neglected, frequent spring droughts demand irrigation, which besides boosting production also contributes to atmospheric humidity and reduces wind erosion. Systems of water management combining drainage and irrigation should be widely established in this region, since 50 per cent of the area is suitable for them. Further, such systems can facilitate the interchange of surface water with groundwater and lead to a fuller use of the region's hydrological resources.
The Sanjiang Plain has abundant water resources. which, when combined with its heavy clay soils and flat topography, provide favourable conditions for flooded field rice cultivation. Rice production should be expanded both to increase grain yield per hectare and to assist in maintaining a better hydrological environment.
Thus a flexible water-management policy should be adopted by all areas to suit local needs, rather than specific policies that define the water problems of the region as a whole. Both waterlogging and drought should be tackled simultaneously (See chapter 8 of this volume).
7. Improved Land Management and Scientific Farming
A sound system of crop rotation is important to the implementation of the planned economy and for better land use. Two opinions now exist regarding the kind of crop-rotation system most suitable for the Sanjiang Plain. One insists that 3-4 areas should be rotated for the production of soybeans with minor plots devoted to other crops. The other advocates the rotation of grass and crops better to maintain soil fertility and for the combined development of agriculture and animal husbandry. Our opinion is that despite conditions favouring the second approach, experience in using the resources of the Sanjiang Plain region is scarce. In the short run, therefore, the first approach should be adopted while experiments on the second are conducted. Results of land-use experiments should be carefully evaluated prior to adopting a particular rotation system on a large scale.
The main soil types reclaimed in the Sanjiang Plain are clayey, humid, and cold, with poor permeability. Poor land use and management in the past have resulted in the destruction of soil structure and a rapid loss of fertility. This situation should be remedied by the application of more organic fertilizers, expanding the use of green manures, assiduously returning crop wastes and residues to the fields, and applying peat to the soil. In some fields, crops should be rotated with grass to increase soil fertility and to promote animal husbandry. Land that has been reclaimed and used for many years should be loosened by deep ploughing. The practice of burning land prior to reclamation has devastated soil fertility, and should be strictly prohibited.
8. Preservation of Swamps
The swamps of Sanjiang Plain developed on low-lying plains and have characteristics distinct from those in other parts of China. Swamps can serve different functions. Hydrologically, those on alluvial plains can reduce flood peaks and regulate food flows. In the Bielahong Basin, where swamps abound, the coefficient of natural regulation of runoff by swamps reaches 0.647.10 The regulatory ability of swamps matches those of forests and lakes. Climatically, swamps help reduce environmental desiccation. in terms of resource provision, they contain abundant peat, reeds, and other types of fibrous plants. They also serve as the breeding and nursery habitats for many species of fish and aquatic birds.
Thus, the swamps of the Sanjiang Plain are an important ecological element. As suggested in subsection 1 above, about 10-15 per cent of the region should be left in swamps. We recommend that: (a) the difficult-to-reclaim swamps in flood-prone areas should be protected because they can equalize river flows and are beneficial to the development of fishery; (b) large areas of reed swamps should be administered by agencies for reed management and that bases of reed production should be established; and (c) natural swamp preserves and ecological research stations should be established in the region for better environmental protection and to enhance the scientific understanding of local wetland ecology.
Notes and References
1. Zhang Yuliang, A Study of the Vegetation on the Friendship State Farm (1956). Beijing: Sciences Press (in Chinese).
2. Wu Chuanjun, An Economic Geography of the Heilong River and the Wusuli River Regions of Heilongjiang Province (1957). Science Press, Beijing (in Chinese).
3. Central Bureau of Meteorology, Historical Data of Drought and Flood in North and Northeast China in the Last 500 Years (1975). Central Bureau of Meteorology. Beijing (in Chinese).
4. Derived from data supplied by the Fertilizer Network of the Heliang Agricultural Scientific Research Institute, Heilongliang Province.
5. Data from Muling Hydrometric Station.
6. Gong Gaofa et al., "Climatic Changes in Heilongjiang Province," Dili Xuebao (Acta Geographica Sinica), 34 (2) (1979) (in Chinese).
7. Zhang Jiacheng et al., Climatic Changes and Their Causes (1976). Science Press, Beijing (in Chinese).
8. Xie Xianqun and Bao Shizhu, "Surface Heat Balance in the Reclaimed Land and Grassland of Eastern Hailaer, and its Effect on Dust Transport, " Dili Xueboo (Acta Geographica Sinica), 33 (2) (1978) (in Chinese).
9. S.A. Sapozhnikova, Microclimate and Local Climate (1950). Hydrometeorology Publishing House, Leningrad (Russian ed.): (1955) Science Press, Beijing (Chinese ed.).
10. Calculated by
where P (K) is the annual distribution function of daily discharge-duration curve, K is the ratio between daily runoff to the average daily runoff.
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