| The groundwater oasis is a special form of oasis in the arid region.Oasis is the core of human existence and production sites,and the essence of arid areas.The stability of the oasis ecosystem is related to local economic development.The stability of groundwater oasis ecosystem in arid area is a key and hot issue in oasis research,and it is also an oasis problem that has not been fully explored and solved at present.The Yaoba Oasis is a typical groundwater oasis where located in the Alashan Plateau of Inner Mongolia of NW China.However,In recent years,with the increasing development of oasis,the rapid population growth has caused a series of problems of instability of the oasis ecosystem,such as the occurrence of groundwater funnel,land desertification,soil salinization and other ecological and environmental problems.In order to achieve sustainable development of the oasis,this theies summarizes the research status of groundwater oasis ecosystem stability in arid areas,as well as the characterization factors of ecosystem stability in the area.Take the Yaoba Oasis as an example,the rough set theory is applied to the comprehensive evaluation process,and the stability of groundwater oasis ecosystem in arid area is constructed.The three methods,rough set,fuzzy set and rough-fuzzy set theory are applied to evaluate the stability of groundwater oasis ecosystem in arid area.Based on those studies,an idea of the classification of oasis stability evaluation is proposed to achieve the division of stability level of groundwater oasis ecosystem in arid area.In the proposed method,the driving mechanism affecting the stability of groundwater oasis ecosystem in arid area is analyzed,and the coupling of the stability evaluation of groundwater oasis ecosystems in the arid area and spatial information technology are realized.A set of information system platforms for the scientific and technical personnel,government decision-makers and the public are provided for the convenience assessment of groundwater oasis stability in arid areas:(1)In this paper,the characterization factors of the stability of the Yaoba Oasis ecosystem are studied from five aspects: groundwater dynamics,groundwater chemistry,soil physical and chemical properties,land use and vegetation.The research results have shown that the groundwater of Yaoba Oasis is continuously and excessively exploited,and therefore,the general trend of groundwater level changes is decreasing year by year.The hadrochemical types continued to change,with an average TDS of 1994.80 mg/L and a maximum value of 3861.10 mg/L.The area of salinized soil is constantly expanding.Non-salinized soil accounts for 20 %,salinized soil accounts for 72 %,and heavily saline soil accounts for 8 %.The overall soil salt content gradually increased from east to west in the horizontal direction,and gradually decreased from top to bottom in the vertical direction.The land use type domainated by farmland,accounting for 85.15 % of the total land area.In recent years,to reduce groundwater extraction,the amount of the research area has gradually expanded the planting aera of water-saving crops,such as oil sunflower and hybrid millet,and reduced the planting area if high water-consuming crops,such as corn.Groundwater levels have gradually recovered since(2)Based on the analysis of the stability of the arid oasis ecosystem and the full consideration of development,the stability of the groundwater oasis ecosystem in the arid area is divided into five levels: one level(very stable),two levels(stable),three(basically stable),four(unstable),five(very unstable).An evaluation index system is initially constructed: divide the groundwater oasis in the arid area into two subsystems: the natural environment subsystem and the social economic subsystem.Using the rough set theory,the preliminary evaluation index system is reduced,and the redundant indicators are removed.Finally,the comprehensive evaluation 20 indexes system of groundwater oasis ecosystem stability in the arid area is constructed.(3)According to the rough set and fuzzy set theoretical models,a new method combining rough set and fuzzy set theory is proposed to comprehensively evaluate the stability of groundwater oasis ecosystems in arid areas.The study results show that the stability of Yaoba Oasis had significant fluctuation,with the overall oasis in a very unstable or unstable state before the year of 2008;in 2000,2001,2003,2004,2005,the overall stability of the oasis was in "Very unstable" range;in 1998,1999,2002,2006 and 2007,the oasis stability was in the " unstable " range;the value of oasis stability index was the minimum;the oasis in a very unstable state.The Yaoba Oasis ecosystem was unstable from 1998 to 2007,and the oasis in the study area gradually became stable after 2008.In 2008,it achieved basic stability,and the oasis ecosystem became stable from 2009 to 2018.The results of the three evaluations objectively reflect the stability status of the oasis ecosystem in the past 20 years.The evaluation based on the rough-fuzzy set theory is convenient,and the evaluation results can qualitatively and quantitatively reflect the stability of the Yaoba Oasis.(4)The evaluation results also reflect that the oasis ecosystem is an extremely complex system,and its influencing factors are multifaceted.The driven mechanism of the oasis stability is based on a set of multiple factors,both natural and human,as well as the combination of natural and human.This paper analyzes the three aspects of water resources,soil and vegetation.The results show that among natural factors,annual evaporation,TDS and drought are important driving factors.Among the human factors,cultivated area is important driving factor.(5)According to the design plan,the function and database of groundwater oasis ecosystem stability evaluation information platform in arid area,a spatial database of groundwater oasis ecosystems in arid regions are constructed,which contained 5 datasets and 35 image layers,including basic geography,socioeconomics,natural disasters,document data and metadata.The platform uses object-oriented development technology to develop an information platform for evaluating the stability of groundwater oasis ecosystems in arid areas.This platform can perform evaluation index selection and weight calculation.The spatial-temporal evaluation of the stability of groundwater oasis ecosystems in arid regions is achieved. |
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