Necessity and Academic Significance of Construction of Experimental Stations

China is among the countries with large water and soil losses in the world. The research on generation and development law of soil erosion should become main subjects for prevention and control of water and soil loss. While through control experiments the indoor simulation can study the law of erosion caused by single factor or combination of limited multiple factors, the filed experimental station can make up and validate the results obtained through indoor simulation. In 1944, our country established its first water and soil conservation experimental station for day-night observation, and successively established more water and soil conservation experimental station along the Yellow River Valley which provided first-hand observation data for resolution of soil erosion problems in the Loess Plateau. The soil erosion problems in the black soil regions of Northeast China, due to its subdued topography, however have not been paid much attention to for a long time. Although the regions currently suffer from severe water and soil losses (see Fig. 10), researchers cannot provide correct answers to a number of scientific questions due to lack of long-term reliable observation data.

Fig. 10 Soil Erosion Status of Black Soil Region, Northeast China

The black soil region in Northeast China with broad definition refers to the region with distribution of black surface soil mainly consisting of black soil, chernozem, meadow soil, baijiang soil, dark brown forest soil and brown forest soil. The total land area of the region is 1.03 million k^m2, including a major part of Liaoning Province (except for Chaoyang City, West Jingzhou City and West Huludao City) with area of 122.9 thousand k^m2, the whole Jilin Province with area of 187 thousand k^m2; the whole Heilongjiang Province with area of 452.5 thousand k^m2; and east Hulun Buir City, major part of Xing'an League and north Tongliao City of Inner Mongolia Autonomous Region (with total area of 267.6 thousand k^m2). The black soil region of Northeast China is important production base for energy, timber materials, coals, metallurgy and steel, and also key production base for commodity grains. The total grain yield in the black soil region in 2004 amounts to 76.74 million tons (covering 16.35% of total yield of the whole country), among which, corns 39.76 million tons (covering 30.52%); soybeans 9.69 million tons (covering 55.69%), and paddy, covering 9.6%; In 2004, the total delivery volume of commodity grains was 41.87 million tons (covering 1/3 of the total volume of the whole country). Moreover, the potential of the region to increase grain production in future covers 60% of the potential of the whole country.

As per the statistics data obtained from the third RS survey, the current area of water erosion in the black region is 177 thousand k^m2 (covering 17.2% of the total regional area), among which, 88.6 thousand ^{m2 in Heilongjiang Province, 40.4 thousand km2 in east Inner Mongolia, 30.7 thousand km2 in Liaoning Province, and 17.3 thousand km2 in Jilin Province. The black soil layer is turning thinner and soil fertility is being reduced due to water and soil loss. A large number of fertile lands are greatly deteriorated by erosion. According to investigations, the average loss of slope lands in the black soil region is 3-8mm per year. In some places with severe water and soil losses, only thin surface soils remain, or even no black soil remains. The initial thickness of the black soil layer was between 40cm and 80cm, however, 40 years later, the thickness was reduced to 30-60cm, and after 80 years, only 20-40cm left. While the black soil layer is getting thinner, the organic matters and fertility of black soils are losing. After 20 years’ cultivation, the fertility of black soils is decreased by 1/3 while after 40 years, decreased by 1/2, and after 80 years, 2/3. Now the organic matters contained in black soils are decreased by 5‰ every years. The annual soil loss in the black soil region amounts to 200 million m3, and the lost Nitrogen-Phosphorus-Potassium elements can be converted into 5 million tons of fertilizer. Each year, grains production is reduced by 16.31 million tons (taking corns for example) due to surface erosion. In addition, gully erosion is damaging farmlands. Currently there are 460 thousands erosion gullies in the black soil region, and the lost cultivate area due to gully amounts to 483 thousand hm2}. Provided each h^m2 of cultivate land may produce 6000kg of corns, the annual loss of grains in the damaged lands by gully erosion is estimated to be 2.9 million tons.

Although the cultivation history of the black soil region is less than one hundred years, the soil erosion situations are getting worse. As the physical and chemical properties of the yellow clay-like loam parent materials under the black soils are not suitable for agricultural production, once the layers of black soils are completely damaged, the agricultural production will be greatly influenced. Therefore, it is of significant strategic meanings for the security of grain production of China to reinforce the treatment of water and soil losses in the black soil region (especially for slope cultivated lands), and control the reduction trends of black soil layers and soil fertility. In 2001, Premier Wen Jiabao instructed that, the works for prevention of water and soil losses in the black soil region should be placed on the agenda of the government. At the same time, CCTV, the People’s Daily and China Water Resources News respectively made relevant reports. Academician Guan Junwei, Wu Chuanjun and others respectively wrote articles to appeal that, “Don’t stay to let black soils turn into yellow soils”.

However, at present time few researches are made on the soil erosion in the black soil region of Northeast China. The soil erosion in Northeast China has particular features, and are different from that of other regions in the following aspects: (1) long slope (see Fig. 11): located in the Songliao Plain, the region has a feature of gentle topography, where erosion phenomenon is usually ignored. In fact, a majority of the region is rolling hill area where Daxing'anling and Xiaoxing'anling Mountains transit to the plains at both sides. Therefore the area features wave landform with small slope gradient (usually below 5°) but long slope length (usually 300-500m; maximum 1500m). As no research on the law of soil erosion of long slope surface has been made in the world, it is unavailable to obtain any observation data for long slope erosion. Because the length scope of slopes contained in most of observation data of the USA is from 11m to 44m (max. 192m), and the length scope of slopes contained in the domestic plot observation data is from 10m to 60m (max. 100m), it is unavailable to use current observation data to study the law of long slope surface erosion. (2) large proportion of snowmelt erosion: Although about 60% of land area of the world are covered with seasonal snow or frozen soils, theoretical research on snowmelt erosion is not among hot topics. Located in the north temperate zone, the average annual snowfall in the black soil region covers 15% of the total rainfall (max. 40%). Snows mainly fall from November to March of the following year. The snowfalls accumulated in about five months are quickly melt in April and May which forms snowmelt runoff. As during this period the earth surface is free of vegetation coverage and the soil structure is damaged due to frost thawing effect, the soil erodibility and soil loss in this period are both increased. (3) severe gully erosion (see Fig. 12): gully refers to the eroded groove with the same longitudinal section with the slope surface where it locates. Gully is not available for cross cultivation and it is the most severe stage of soil water erosion. The sediment produced by gully erosion covers more than half of the total sediment yield in the basin. The sediment silting in river not only cracks lands but also damages land resources. While the cultivated area is decreased by gully erosion, the efficiency of mechanization of agricultural production is also greatly reduced.

Fig. 11 Long Slope Surface of the Black Soil Region in Northeast China

Fig. 12 Severe Gully Erosion

The construction of Jiusan Experimental Station provides great support to resolve the above mentioned scientific questions. The resolution of these questions will undoubtedly provide an important scientific and research platform for our country to realize both protection and sustainable utilization of black soil resources, and a demonstration base to transform scientific research findings into productivity.