| Co-integration analysis of Minqin oasis agricultural systems |
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| DOI：10.7606/j.issn.1000-7601.2016.01.43 |
| Key Words: agricultural system johansen co-integration vector error correction model (VECM) Granger causality Minqin oasis |
| Author Name | Affiliation | | LI Xiao-lin | College of Environmental Sciences and Engineering, Southwest Forestry University, Kunming, Yunnan 650224, China | | LIU Xiao-na | Institute of Comprehensive Research, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China | | SUN Dan-feng | Department of Land Resources Management, College of Resource and Environmental Science, China Agricultural University, Beijing 100193, China |
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| Abstract: |
| Based on long time series statistical data from 1956 to 2008, the general changes of agricultural production system (crop and livestock) and environmental system under the condition of land degradation in Minqin oasis were analyzed comprehensively using the method of the Johansen co-integration vectors model. Vector error correction model and Granger causality tests were adopted to examine the interactions among different systems. Through the analyses of the long-term equilibrium relationship and short-term fluctuation in agricultural system, the adjustment of agricultural structure and comprehensive management policies of the Shiyang river basin would be supported. The result showed that under the condition of land degradation, there was a long time co-integration relationship between agriculture production system and environmental system, which avoided agricultural system crash. Whereas, there was a vicious circle among extensive crop production expansions, groundwater overdraw, overgrazing and sever land and water resources degradation. Additionally, in light of short term fluctuations deviated from the long run equilibrium, the adjusting speed of weather (sand storms) and groundwater resources (motor-pumped well number) were the fastest, which were 0.9129 and -1.2583, respectively. Dust storms times and motor-pumped well were chosen to monitor desertification. Moreover, the result of Granger causality tests showed that sheep population and groundwater resources (motor-pumped well number) were the granger reason of sand and dust storms. With the development of animal husbandry, carrying capacity of nature was exhaust, and frequencies of dust storms were increased. Exploitation of groundwater caused degradation of local water resources, the deaths and the recession of vegetation. Thus, reducing grazing and effective management of groundwater resources could counteract desertification in arid western region. |
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