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II: The wetlands of Heilongjiang province, north-east China

7. Regional development, environmental change, and improved resource management in the Sanjiang Plain
8. Swamp transformation in the Sanjiang plain by the well-drainage and well-irrigation method
9. The origin and transformation of wetland on the south-eastern slopes of the greater Khingan range (Da Xingan Ling)

 

7. Regional development, environmental change, and improved resource management in the Sanjiang Plain

Liu Xingtu, Sun Guangvou, Zhang Yangzhen
Chen Gangqi, Yi Fuke, Zhao Huanchen
Zhang Wenfen, and Huang Xichou
Institute of Geography, Chinese Academy of Sciences, Changchun. Jilin Province
and
He Yongqi
Institute of Natural Resources, Harbin, Heilongjiang Province

Abstract

Since the large-scale reclamation of the Sanjiang Plain, drought, wind erosion and local desertification have occurred. Indicators of environmental deterioration, the successive droughts in the last several years resulted in large part from changes in the pattern of atmospheric circulation, but human activities in the region have also been significant. The development of the region's resources should be comprehensive and balanced. Water management should combine drainage with irrigation and better land management and farming methods should be used. Some areas of wetland should be preserved because of their essential and varied ecological functions.

The Sanjiang Plain of Heilongjiang Province, north-east China, is composed of the alluvial plain at the confluence of the River Songhua, the River Heilong (River Amur), and the River Wusuli (River Ussuri) together with the alluviallacustrine plain of the River Muling and Lake Xingkai, to the south of the Wanda Shan (fig. 7. 1). It is bounded by the Xiao Xingan Ling (Lesser Khingan Range) in the west, the River Wusuli (Ussuri) in the east, the River Heilong (Amur) in the north, and Lake Xingkai in the south. Its north-south extent is 520 km, and it runs 430 km from east to west. The plain has a total area of 51,300 km (table 7.1).

Fig. 7.1. Location of the Sanjiang Plain

TABLE 7.1. Principal Categories of Land Use in the Sanjiang Plain

Category Area (million ha) %
Forest 3.92 37.2
Cultivated 3.08 29.1
Wetland 2.18 20.6
(Inundated 0 35 -)
Water bodies 0.47 4 4
Pasture 0.18 1.7
Reedbeds 0.09 0 9
Others 0.65 6.1
Total 10.92 100.0

The vast, level and well-watered Sanjiang Plain region is endowed with abundant natural resources, including highly fertile soils, long hours of sunshine, abundant rainfall, and extensive tracts of forest, grassland and reedbeds. The region thus is naturally suited to the development of agriculture. animal husbandry, forestry, fisheries and complementary occupations.

Fig. 7.2. Land-use Patterns in the Middle Bielahong Basin, 1975

Fig. 7 3. Land-use Patterns in the Middle Bielahong Basin. 1978

The rich water resources of the Sanjiang Plain region include the three major rivers - the Heilong, Songhua, and Wusuli - together with their more than 20 major tributaries, plus the Greater and Lesser Xingkai Lakes and many smaller lakes and swamps. The annual surface runoff is 12,300 million m, and recoverable groundwater is estimated to be about 15,000 million m/yr. Rivers, lakes, wetlands and reservoirs in the entire region amount to some 2.74 million ha.

The region has abundant rainfall and enough hours of sunlight for agriculture, with rainfall and temperature maxima in the summer. The annual average rainfall is approximately 550 mm, 70 per cent of which is concentrated in the growing season. The total annual hours of sunshine average 2,300-2,600, with 1,000-1,200 in the growing season. The active accumulated temperature is 2.4002,500C. and the frost-free season is about 130-145 days.

The major soils of the region include brown earth, black soil, Baijiang soil (planosol). meadow soil. and swamp soil. The black-soil layers are generally more than 20 cm thick, and in some localities exceed 1 m in depth. The average organic matter content is about 5-6 per cent, but in some places it may reach 10 per cent.

Before reclamation the Sanjiang Plain was a vast tract of meadow and swampland, known locally as the Beidahuang (the northern wilderness). The natural landscape of the region was characterized by dense and mixed coniferous forests in the uplands of the Xiao Xingan Ling (Lesser Khingan Range), the Wanda Shan, and the Laoye Ling; by extensive swamps, swampmeadows and meadows in the plains; by deciduous broad-leaf forests (with Quercus mongolica, Betula spp., and Tilia mandshunca as the main species) and partial meadows on the sloping piedmont plains;' and by sporadic broad-leaf forests on the hills, secondary terraces, gently undulating watersheds, and on the former natural levees along old river courses. The original vegetation was dominated by meadows and forests. Approximately 1,000 distinct plant taxa, or one-third of those in the entire North-east Region, have been identified in the Sanjiang Plain. There are 2.4 million ha of forest land in the Plain, 90 per cent of which is natural, and 24 per cent of the region is forest covered. The total reserve of timber is an estimated 232.71 million m. The Sanjiang Plain has abundant grasslands, particularly of Calamagrostis angustifolia komarov, a widespread, fine pasture grass second only to fescue in quality, and which yields about 380 kg/ha of edible material. There are more than 88,000 ha of reedbeds, which annually produce about 134,000 t of reed. The total grass fibre reserves of the region are 8.84 million t.

The wildlife resources are also abundant. More than half the species of birds, mammals, and fish documented for Heilongjiang Province occur in the Sanjiang Plain, where 192 species of birds, 50 of mammals, and 51 kinds of fish are found.

Although natural conditions favour the development of primary resources. in recent years, concomitant with reclamation of wetlands and development of the region, signs of environmental deterioration have appeared. This chapter summarizes the results of preliminary studies of changes in the natural environment of the Sanjiang region, conducted in 1973-1975 and 1979, and recommends suitable forms of regional development for future application.

Resource Development and Environmental Change

Because of the difficulty of wetland reclamation and its frontier location, the economic development of the Sanjiang Plain began relatively recently, and although prior to 1949 the region had already been seriously deforested, little land had been reclaimed for agriculture, and only some 3 per cent of the total area was cultivated.2 But since the mid-1950s the area farmed has expanded each year. Between 1975 and 1978, for example, the percentage of cultivated land in the upper and middle Bielahong Basin, in Heilongjiang Province, increased by almost 10 per cent (table 7.2, figs.7.2 and 7.3). In this area land is being reclaimed at about 20,000 ha/yr, and in 1979 the area cultivated in the Sanjiang Plain amounted to 1.8 million ha, or 36.1 per cent of the total area of the region. As a consequence. in the last two decades many State Farms and People's Communes have been built in the Sanjiang Plain, which has become one of China's leading grain production regions. Meanwhile, in the absence of comprehensive planning and as result of problems caused by reclamation, the landscape of the region has undergone tremendous changes.

TABLE 7.2. Land-use Changes along the Upper and Middle River Bielahong,1975-1978 (Compiled from LANDSAT images, 25 July 1975 and 30 June 1978)

  1975 (%) 1978 (%)
Agriculture 29.3 39.9
Forest 12.2 11.5
Waste 55 4 44 9
Other 3.1 3.7
Total 100.0 100.0

Indicators of Environmental Deterioration

As a consequence of land reclamation and related development projects implemented in the Sanjiang Plain during the past three decades, clear signs of a serious decline in environmental quality and resource productivity are visible. In the region the principal indicators are, inter alia, decreased rainfall and an increase in drought severity, a decrease in groundwater levels and river discharge, increased wind and other types of erosion, local desertification and soil salinization.

1. Decreasing Rainfall and Increasing Drought

The Sanjiang Plain is a relatively humid area, the average annual rainfall of which, under natural conditions, should be about 550 mm, with a maximum of 800 mm. But since the 1950s, when large-scale resource development started, a remarkable change has taken place on the region's land surface as a consequence of both changing regional patterns of atmospheric circulation and human activities, particularly the massive land reclamation and excessive deforestation, and precipitation amounts have varied considerably.

Analysis of rainfall averages and empirical data reveal a decline in precipitation during the last three decades (fig.7.4). From 1975 to 1978, at various locations in the Sanjiang Plain, rainfall totals decreased 120-180 mm below past averages. Compared with other areas of Heilongjiang Province, the Sanjiang Plain has historically always been the area most seriously stricken by flood disasters and the least subject to drought. From 1949 to 1974, for example. three drought years occurred. but there were 12 flood years (table 7.3). Since 1975, however, this region was drought-stricken for four consecutive years, which severely reduced agricultural productivity. In 1978, for example, because of drought, wheat yields at Youyi State Farm averaged only 500 kg/ha, and 3.600 ha of wheat (23.6 per cent of the total sown area) were lost entirely.

TABLE 7.3. Frequency of Drought and Waterlogging in Heilongjiang Province, 1949-1974

Region Drought Waterlogging
Frequency of
continuous
Frequency of
continuous
drought
Frequency of
occurrence
Frequency of
occurrence
waterlogging
Sanjiang Plain 3 0 12 1
Songnen Plain 19 6 9 2
Central Mountains 4 1 5 1

Fig. 7.4 Precipitation Changes at Jiamusi City, Heilongjiang Province

Fig. 7.5. Annual Runoff Changes in the River Bielahong, Heilongjiang Province

As a result, the annual average rainfall of the Sanjiang Plain is now 180 mm less than that of 20 years ago, and is 100 mm less than that of comparable areas nearby. In the Songnen Plain, located at the same latitude and immediately west of the Sanjiang Plain, rainfall has decreased annually by 4 mm, and in the Soviet Far East the annual decrease has been about 5 mm. But in the Sanjiang Plain the decrease has been on the order of 9 mm/yr. During the same period the decrease in the region's relatively humidity is 2 per cent greater than that of other comparable areas, the largest annual decrease in the Sanjiang Plain being 0.12 per cent. compared with only 0.01 per cent in the Songnen Plain. In the same period the average summer temperature in the Sanjiang Plain increased by about 0.8C. whereas in other areas the average summer temperatures were lower than those of two decades ago.

2. Decrease in River Discharge and Groundwater Levels

Owing to a continuous decline in rainfall, the volume of discharge in the smaller rivers of the Sanjiang Plain has decreased drastically and floods no longer occur. Within the 4,340 km watershed of the River Bielahong the average annual rate of discharge in the last three years has been less than 2 m/sec (fig.7.5). The average depth of river runoff during the period 1974-1978 was only 14.8 per cent of the normal depth. The groundwater level in the plain area has also declined seriously. In 1960, the groundwater level in Luobei was 0-3 m below the surface, but now its depth is 3-8 m. The static level of the pressure water on the Qianjin State Farm dropped by 2.63 m during the period 1974-1979.

3. Increased Frequency of Wind Storms and Acceleration of Wind Erosion

In the past, the Sanjiang Plain rarely experienced winds greater than 11 on the Beaufort scale. But recent observations in the Yilan and Jiamusi areas of Heilongjiang show that the frequency of winds between 9 and 11 on the Beaufort scale has increased, the maximum wind speed recorded being 40 m/sec. As many as 63 days/yr with winds in excess of Beaufort 8 has been recorded. Meteorological data show that the frequency of winds with speeds greater than 17 m/see increased by 33.5 per cent in two decades, from 8 occurrences in the 1950s, 11.4 in the 1960s, to 14.2 in the 1970s.

Similarly, prior to land reclamation, when the natural vegetation remained largely intact, wind erosion was an insignificant factor in the Sanjiang Plain. Now, however, it has become a serious problem and more than 60 per cent of the region's cultivated area has been affected by wind erosion to various degrees. This problem is particularly serious in the central part of the plain, where reclamation began earlier than elsewhere. One particularly severe instance will serve to illustrate this new phenomenon. For four consecutive days (6-9 May 1979) a violent sandstorm raged across the plain. The maximum wind velocity in such places as Jiamusi, Luobei, Fujin and Tongliang reached 22.7-25 m/sec. and visibility was less than 500 m. Some 2,000 ha of wheat seedlings at Baoquanling State Farm were swept away. and a further 990 ha were buried under sand; 6,600 ha of wheat suffered from root exposure and another 14,000 ha from leaf dehydration.

TABLE 7 .4. Decrease in Soil Fertility Resulting from Wind Erosion

Fertility element Degree of wind erosion and depth of erosion (cm)
Unreclaimed land not
affected by wind
Moderately
eroded
Severely
eroded
2-20 20-40 1-20 20-40 0-1 1-40
Humus (%) 5.96 0.46 0.59 0.32 0.08 0.06
N (%) 0.20 0.04 0.05 0.02 0.02 0.02
P(%) 0.14 0.06 0.48 0.33 0.03 0.04
K (%) 2.94 3.09 2.99 3.20 3.65 2.89
Rapidly available N
(mg/100g)
44.09 24.94 26.71 19.47 26.88 18.45
Rapidly available P
(mg/100g)
19.10 6.57 1.30 0.79 2.55 2.18
Rapidly available K
(mg/100g)
26.20 6.80 11.10 4.80 1.90 2.40

4. Decline in Soil Fertility

The organic matter and the total N content in several major soil types tended to decline during the period 1964-1974 (table 7.4). Organic matter in soils reclaimed in earlier years decreased from about 5 to 2 per cent, at a rate of 0.09 per cent/yr. The greatest decline occurred in the Baijiang soil whereas little decrease took place in meadow and black soils. The decline of the total N content averaged 0.06 per cent/yr. and the Baijiang soil again experienced the greatest drop. The total Ph content, however, increased at an average annual rate of 0.02 per cent, because of the application of phosphatic fertilizer. The increase was particularly noticeable in the meadow soil.

Wind erosion has been a significant factor in the rapid loss of soil fertility, especially in burozem and Baijiang soils. At Laolonggang, Luobei County, the content of organic matter in wind-affected surface layers is 0.08 per cent, compared with the normal 5.96 per cent in the topsoil of unreclaimed land undamaged by wind erosion.

5. Local Desertification

With the intensification of wind erosion, local desertification and change in soil structure has occurred around Luobei and Suibin, where some natural levees have been eroded by wind thereby exposing the alluvial sand and forming dunes. The area affected by drifting sand is expanding continually, as is exemplified by Junchuan State Farm, where, in the No.7 Field of the Fifth Brigade, the area affected by drifting sand has increased from 0.99 ha (1970) to 4 ha (1979). Until the early 1950s, birch forests, growing on black soil 18-20 cm thick and underlain by medium fine sand, thrived at Laolonggang and Heilinzi, in Luobei County. But since 1956 deforestation and reclamation have caused localized denudation of the black soil, and these heavily eroded areas now support only sparse grasses such as Setaria lutescens, Digitaria linearis, Xanthium stumanum and Salsola collina.

In some areas north of the River Songhua, deflation has resulted in a coarser soil structure (fig.7.6). In the land of the 24th Brigade of State Farm 290, for example, the surface soil before reclamation had 23.23 per cent clay particles and 40.85 per cent physical clay. After reclamation, which led to accelerated wind erosion, the clay particle content decreased to 5.48 per cent, and that of physical clay to 15.94 per cent. Meanwhile, the content of sand particles increased from 34.85 to 72.14 per cent.

6. Increase in Soil Salinization

With the increasing aridity of the Sanjiang Plain the salinization of meadow soil has been aggravated. In the early 1950s, patches of salinized meadow soil and gleyed and salinized meadow soil were limited to only the piedmont area at the Youyi State Farm. But large-scale reclamation has resulted in an expansion of the areas affected, and by 1975 the area of such soils amounted to 118,000 ha, or 0.7 per cent of the total cultivated area. in addition, salt has tended to accumulate in the surface layers (table 7.5), and the salinity of some tracts reclaimed earlier has increased from light to medium.

Fig. 7.6. Structural Changes in Burozem Soil Resulting from Local Desertification

TABLE 7.5. Changes in Salt Content of Saline Meadow Soil (mg/100g soil)

Years since
reclamation
Soil depth (cm)
0-5 5-10 15-30 0-30
2 63.0 123.0 17.0 101.5
3 70.5 17.5 74.5 162.5
9 121.6 24.8 25.6 172.0

7. Aggravation of Soil Erosion

With the destruction of forests and meadows, soil erosion has become increasingly serious on the sloping Piedmont plains, hills, and low mountains which surround the Sanjiang Plain, as well as on the terraces in the plain itself. Near Wuerhuli Mountain, in south-eastern Fujin County, for example, there occurs a large area of secondary terraces. The area has been almost completely deforested during the last 70 years, and after three decades of cultivation the black-earth soil layer has been reduced from 30 to 10 cm in depth. Also new gullies, some over 100 m long and 6-7 m deep, are being formed on the slopes. By 1979,792,000 ha, or 26 per cent of the cultivated land in the region had been affected by soil erosion. An average of 5-6 mm/yr of surface soil is washed from cultivated slopes, the equivalent of 800-950 m/ha/yr. The sand content in the River Muling, Heilongjiang Province, averaged 33.5 kg/m in the five years before 1962, whereas it increased to 46.7 kg/m in 1975.5 Wind erosion in the Sanjiang Plain has always been common, and 670,000 ha are affected, 337,000 ha seriously.

8. Vegetation Changes

Historically, dense forests and vast stretches of grassland covered the Sanjiang Plain. But in recent years they have decreased conspicuously as a result of excessive felling of timber, inadequate replanting, clearance for agriculture, and the lack of afforestation after swamp reclamation. In 1962,3.16 million ha were forested and 29.9 per cent of the region was under forest. But by 1976, forests had declined to 2.25 million ha, or 21.2 per cent of the regional area, an astonishing loss of 916,000 ha of forest in just 14years.

In 1973-1975,1.1 million ha of swampland and 1.2 million ha of swamp-meadows, together comprising 46.7 per cent of the total area, remained in the Sanjiang Plain. But owing to constant reclamation this area is decreasing. In 1973, water still accumulated in various types of wetland, but by 1978 the overwhelming majority of the swamps had become dry, a change that has led to a major alteration in the wetland and meadow vegetation (fig.7.7). At the Qianjin State Farm it took just one year for the dried Carex lasiocarpa swamps to evolve into swampmeadows, where Cirsium sp. also emerged (table 7.6). Most wetlands in the Sanjiang Plain are gradually becoming swamp-meadows or meadows. Control of the rivers has either reduced or cut off the water supply to the swamps during flooding. Further, owing to the steady improvement of drainage projects in the plain, it would be difficult, even with prolonged rainfall, to return to a condition whereby rivers frequently flooded and replenished the swamps.

Since 1974, an additional 26,000 ha of reed swamps have been reclaimed by burning. In some areas this process destroyed the long-accumulated root and peat layers of the soil, and the organic matter content was reduced from 50.65 to 1.53 per cent. The land was thoroughly desiccated.

9. Heightened Pollution

The River Songhua receives daily an enormous sewage load. At the confluence of the Rivers Songhua and Heilong, near Tongjiang, where the total discharge is 336 m/sec., the volume of sewage amounts to 27.19 per cent. More than 100 rivers in the region are polluted. Air pollution has also appeared in the region, particularly in the cities and around industrial and mining centres. Coal consumption is more than 8 million t/yr, and about160,000 t/yr of sulphur dioxide and 1.36 million t/yr of ash are discharged into the atmosphere.

Fig. 7.7. Sequence of Vegetation Changes with Varying Moisture Levels in Swamps and Meadows of the Sanjiang Plain, Heilongjiang Province

TABLE 7.6. Changes in Community Composition and Structure of Carex lasiocarpa Swamps with Desiccation

Scientific name Plant characteristics

1 July 1978

13 Sept. 1979

Abundance Height (cm) Abundance Height (cm)
Carex lasiocarpa Cop3 30 40 Sp 45
Deyeuxia angustifolia Sp 30-40 Cop3 40
Menyanthes trifoliata Sp 10 Un 15
Sium suare var. angustifolium Un 20 Un 110
Cicuta virosa van tenuifolia Sp 30-35 Un 15
Equisetum heleocharis Sol 40-45 Sol 40 45
Naumburgia thyrsiflora Sol 10-15 Sol 10-20
Iris laevigata Sol 10 - -
Caltha palustris Un 7 Un 20
Chenopodium glaucum - - Sp 18
Cirsium sp. - - Un 23
Inula sp. - - Un 25

Note: Cop3 = many; Sp = few and dispersed; Sol = sparse; Un = single specimen

Newly built industries simply have neither installed pollution-control equipment as required by law nor implemented other necessary measures for environmental protection simultaneous with plant construction. As a result, industrial pollution is becoming increasingly serious, and in addition, noise, the residues of agricultural chemicals, and artificial radionuclides are also now emerging as serious pollutants in the region.

10. Rapid Decrease in Wildlife

Such changes in the natural environment have played havoc with wildlife. In former times the Sanjiang Plain was so rich in wildlife that one could "catch a musk-deer with a stick and fish with a wooden dipper. " But with industrial and agricultural development and the careless exploitation of natural resources, many valuable elements of the biota have been disappearing at an alarming rate. Only 18 northeast tigers remain in the area. Fish catches have also shown a drastic decline, from 22,000 t (1960), an all-time record, to only 3,200 t (1970), including 1,100 t accounted for by aquaculture.

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