| With the increasingly accelerated process of new-type urbanization,contradictions in the coordination between the natural environment and human activities have become more obvious.The appearance of habitat fragmentation has posed severe challenges on urban and regional ecological planning,and significantly weakened the stability of ecological network.As a particular ecological component in arid and semi-arid area,oases serve as a basic site for the survival,activities and development of human in arid areas,and have an important role in regional ecological environment.Since the ancient times,the Hexi Corridor area has been in a relatively vulnerable ecological environment.In addition,the unreasonable exploitation and utilization of water resources has worsened the severe ecological problems such as land desertification,water shortage,and drying up of inland rivers in this area.Oases ensure the safety of ecological environment and regional sustainable development in Hexi Corridor.A systematic study on oases is a key to solve the ecological problems in this area.The Eco-network concept originated in the 19 th century,and has been widely applied in many developed countries and regions with significant effects.In this study,the author investigates the oases in Hexi Corridor,defining the concept of oasis Eco-network by using the theories of landscape ecology.Using a combination of network analysis and minimum cost pathway approaches,and under the guidance of Eco-network theories,this study focuses on the analysis and identification of already existing and potential ecological nodes and corridors,reasonably building an oasis Eco-network in the Hexi Corridor area and smartly evaluating it,suggesting a compound Eco-network framework for the Hexi Corridor area,planning the desired development direction and potential zones of Eco-network in the Hexi Corridor area in order to achieve sound and sustainable development of regional ecology.Main results are as follows:(1)During 1985-2013,the area of different land use types was constantly changing in Hexi Corridor.The overall land use was unbalanced.The area of grassland and unused land decreased after an increase;arable land,construction land and waters increased continuously,with the most obvious increase seen in arable land,which reached 0.996,close to 1.Research data show that over the past nearly 30 years,the land use transformation was dominated by the transformation of other types of land use to arable land;in terms of the landscape types and landscape level,within the study period,the landscape pattern of different types of land use also changed a lot.The decrease in the number of patches of arable land and the increase in the average density of the patch indicate that the land use types dominated by arable land were going toward intensification.Different land use types became more spatially connected,and more agglomerative.To some extent,this trend is helpful for the installation and construction of farmland irrigation infrastructures.(2)The select ecological abundance index,vegetation coverage index,water network density index,land degradation index,and environmental quality index were selected as evaluation indicators for the ecology in Hexi Corridor Area.The evaluation results of ecological environment quality were obtained for 21 cities and counties in Hexi.By using the BP neural network evaluation model,a smart evaluation was made for the ecological environment quality in 2001 and 2013 respectively.The results showed that,the ecological environment in Jiayuguan City,Yumen City,Jiuquan City,Zhangye City and Shandan County was going backward,while that in Jinta County,Aksay County and Gulang County became somewhat better.The introduction of BP neural network evaluation model provides a scientific measurement and evaluation mechanism for subsequent ecological construction,and avoids any man-made and one-sided evaluation model.(3)According to the mosaic ribbons divided in Hexi Corridor,57 representative ecological nodes were taken from the ecologically functional zones to build a network connecting 78 ecological corridors and ecologically functional zones,with a total length of3635 km.The study found that the Eco-network closure ? index for ecologically functional zones in Hexi Corridor is 0.229,the network line-point ratio ? index was 1.368,the network connectivity ? index was 0.469,and the cost ratio Cr index was 0.9875.The evaluation results index indicates that both the mosaic Eco-network distance and the network density were at a significantly low level,suggesting ordinary characteristics of the Eco-networks;in terms of the network density,the ecological corridor network had adensity of 0.1067,with an average of 2.56 connecting lines per node;the water network ecological corridor had a density of 0.0989,with an average of 1.64 connecting lines per node.The number of connecting lines between nodes reflects the close degree of the relation between nodes.Both the road ecological corridors and the water network ecological corridors had a density lower than ordinary network density,indicating a relatively poor correlation between current ecological corridors of Hexi Corridor,showing an outstanding ecological isolation.Moreover,main ecological nodes are roughly distributed in oasis areas,and the connectivity within the ecosystems is declining.(4)The creation of a compound Eco-network integrates the oasis Eco-network,road Eco-network and river Eco-network.Key ecological nodes were given,and potential ecological corridors were simulated.On the whole,the overall statistic characteristics of the number of nodes and connections of this network system follow the power-law distribution and have scale-free properties,good agglomeration effect and strong growth.The analysis of simulated potential ecological corridors shows that the oasis Eco-network is different from the real road networks and river networks in terms of spatial distribution.Uneven distribution led to ecological breaking points.Compound Eco-network provides a powerful theoretical basis for future ecological construction.The future efforts should place greater focus on the ecological construction of ecological breaking points in order to enable regional ecological barrier protection.The creation of compound Eco-network verifies that the study on oasis Eco-network conducted in regional scale is theoretically feasible.(5)Based on the core ecological nodes and potential ecological corridors present in the compound Eco-network,this paper presents the conception of oasis Eco-network framework consisting of “one center,one ring,and three belts”,with “Zhangye oasis as the center,Minle-Zhangye oasis as the core development ring of Eco-network,Yumen-Jiuquan-Dunhuang oasis belt,Heihe River Basin belt and Minqin ecological belt as the core expansion zone.” With enhanced connectivity of Hexi Corridor Eco-network and improved ecological environment as the starting point,this conception is of great significance for improving the connectivity of landscape ecosystem,intensifying the spatialassociation between ecological source places,ecological corridors,and ecological substrates,thus maintaining the overall stable development of regional ecology in Hexi Corridor. |
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