| Speeding up the tempo of environmental protection and construction is one of the major issues in the West Development Strategy. Making a thorough study to find out the reliable measures to ecological resumption in this oasis agricultural area has an important scientific and practical significance. It can provide scientific basis for making a better decision for the ecological resumption. A systematic research has focused on the present ecological condition, development traces, existing problems, ecological footprint, assets and liabilities, energy flow and transformation, and resuming measures through applying such research modes and analyzing methods like ecological footprint, environmental assets and liabilities, systematic analysis, problem tree analysis, comparative evaluations etc. Based on the research, the conclusions drawn are as follows:1.Research on the ecological footprint in this area has shown that the ecological carrying capacity was on the remainder stage from 1949 to 1980. Each person's ecological carrying capacity in 1949 was 0.55hm2, the ecological footprint was 0.42hm2, on an average level, each has an ecological remainder of 0.13 hm2. In 1980, both the ecological carrying capacity and footprint for each person were 1.02 hm , which showed well balance. From 1980 to 1985, both the ecological carrying capacity and footprint were on a rapid growth stage, which showed a relative balance for a short period. From 1985 to 2000, the ecological carrying capacity was on deficit stage, both the ecological carrying capacity and footprint assumed a decline tendency. Each person's ecological carrying capacity and footprint were 1.78 hm2 and 2.08 hm2, each had a deficit of 0.3 hm2. The study shows that the ecological deficit in Jiuquan, Wuwei, Zhangye three cities and Yongchang county were 0.63hm , 0.30 hm 0.13 hm and 0.11 hm respectively. These deficits have shown that the agricultural development in this area has deviated far away from a sustainable one. No matter viewed locally or globally, agricultural development in this area can't be sustainable.2.Research on environmental assets and liabilities in this area has shown that the environmental assets have been reducing continually. Changed bystages, it assumed a decreasing tendency during 1949 to 1975, from 9.6 to 1.6. Then it somewhat rose during 1980 to 1991, from 2.1 to 4.4. From 1995 to 2000, it kept relatively stable, with changing ranges of 3.2 to 3.3. The environmental liabilities also has been decreasing, from -1.2 in 1949 to -28.1 in 2000. During this period, it assumed three obvious stages. On an average level, it decreased by -1.41 from 1949 to 1970, -4.12 from 1975 to 1985 and -20.33 from 1991 to 2000. The environmental net assets assumed a decline tendency from 1949 to 1970, with decreasing ranges of 8.4 to 1.3. In 1975, the decreasing rate began with a negative value (-0.5), and decreased to -24.9 in 2000, which has also shown the environmental assets deposits are decreasing continually.3.Conclusions drawn on the basis of the study on energy characteristic and developing law of Hexi Oasis Agro-ecological system have shown that the inorganic energy input from 1991 to 2000 was increased by 50 times compared with that from 1949 to 1960, while the organic energy input at the same period was increased by 97.2%. The structure of energy input also changed radically, from an organic energy input dependant pattern to an inorganic energy input dependant one. The ratio between the total amounts of energy input and the organic energy input from 1949 to 1960 was 1:13.7, and was 1.9:1 from 1991 to 2000. The energy output capacity from 1991 to 2000 in the whole area was increased by 3.5 times compared with that from 1949 to 1960. But the proportion between output and input at the same period decreased from 2.34 to 1.98. Currently the energy input level is just within an appropriate range, only reached the theoretical energy input critical value of 65.8%. This means, on one hand, there are still spaces for energy input in this area, on the...
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