Research On The Evolution Of Habitat Quality In Xianyang City Based On The Change Of Landscape Pattern

At present,with the accelerating process of social,economy and urbanization,human activities becomes increasingly pronounced.The speed and scope of surface landscape pattern change greatly exceeds the natural landscape change process under the disturbance of human activities.Then problems of land degradation and environmental pollution can threaten the stability of regional ecological environment and habitat quality.Xianyang is located in the central part of Guanzhong Plain,adjacent to Xi'an.As an important part in the integration of Xi'an and Xianyang,it has a great influence on Xi'an's politics,economy and culture both in the historical period and in the present.However,the intense human activities bring severe challenges to the ecological construction and sustainable development of Xianyang.Therefore,based on the landscape pattern change,the relationship between landscape pattern and ecological process is discussed from the perspective of habitat quality service,which is of great significance to analyze the changes of regional ecological environment and even the global environment.It can provide the basis for the landscape pattern optimization,biodiversity conservation and ecological security planning of Xianyang,which has important ecological guiding value for the future development of Guanzhong urban agglomeration.Under the review of foreign related researches,this paper selects Xianyang City as the research area,which has the complex human activity characteristics.Based on the classification data of landscape types which interpreted by remote sensing in 2000,2008 and 2016,supported by GIS and RS techniques,landscape metrics and moving window methods are used to study the spatial-temporal features and gradient changes of landscape pattern in Xianyang.The InVEST model are introduced to evaluate the habitat degradation,habitat quality and habitat rarity of Xianyang.Then we analyze the spatio-temporal variation of habitat quality pattern based on county scale and spatial autocorrelation analysis.On the premise of exploring the influence factors of Habitat quality change,the management suggestions are put forward.It can provide the scientific reference for the sustainable utilization of resources,ecological construction and protection.The main conclusions are as follows:(1)Landscape types of this study area from 2000 to 2016 are mainly cultivated land,woodland,grassland and construction land,whose changes is obvious.Woodland and grassland have increased than 2000,indicating that Xianyang has achieved achievements in ecological restoration since the Green for Grain Project.The growth of construction land is the fastest.The reason for this is that cultivated land decreases,and it's also related to the increasing demand for construction land caused by urban expansion.The comprehensive land use dynamic degree is 2.76%and 2.93%respectively in two periods of 2000-2008 and 2008-2016,and the change rate of landscape type is generally slow.(2)The degree of landscape fragmentation promotes from 2000 to 2016,the distribution of landscape types tends to homogenize,and the complexity of landscape structure composition increases.The main performance is that small patch area whose mainly in construction land raises,and the cultivated land is unceasingly divided.The proportion difference of each landscape type area decreases,and the landscape type tends to be broken,which is coincides with the fact whose study area is developing and the urbanization is expanding constantly.(3)The analysis range of 750m is the best scale for the analysis by moving window method in this study area,and the landscape pattern shows obvious spatial-temporal distribution characteristics.Forest land is the main area in the northeast because of the higher terrain,and the weak human disturbance factor.Therefore,the degree of landscape fragmentation during this study period is relatively low.With the continuous expansion of urbanization,the flat southern plain area is influenced by human activities,whose fragmentation degree is higher,landscape uncertainty information becomes more than ever before,and tends to homogenize.(4)Under the influence of urbanization development and the difference of terrain,the overall landscape characteristics of different directions are significantly different.Taking the east-west transect 'a' in the rapid urbanization area and the north-south transect 'b' across different terrain and geomorphology as the research object.It shows that the landscape fragmentation degree of transect 'a' becomes higher during the study period.The landscape composition difference between cultivated land and construction land is reduced,and the landscape structure is gradually equalized.The fragmentation degree and complexity of landscape type in transect 'b' are increased.Then differences among different landscape components becomes smaller,the diversity of landscape increases,and the landscape fragmentation degree near Bijia Mountain's highest point is lower.At the same time,there are differences between the north and the south.With rising altitude,human disturbance factors has decreased,while the correlation between elevation factor and landscape metrics is significant,which leads to the effect on landscape change is strengthened.The results show that urban expansion and human disturbance have great influence on landscape pattern change,while 'mountain barrier'and altitude have certain influence.(5)The degree of habitat degradation in Xianyang has increased from 2000 to 2016,the habitat quality is higher in the north and lower in the south.Although the habitat rarity value has increased,the overall value is relatively low.In the research period,the whole degradation level of habitat increases.Compared with the northern region,the degradation rate in the south is faster.As time goes on,high degradation type spreads northward.With the south center as the core,the trend of decreasing gradually toward the surrounding.In terms of habitat quality index,the better habitat areas are more distributed in the middle and the north while the poorer regions are mostly distributed in the south.Habitat quality in the southern middle zone has improved in 2008 and 2016,and the average grades increase from 0.578 in 2000 to 0.626,and then decrease to 0.519.The range of habitat rarity values is enlarged,which shows that the difference of landscape patch stability become larger.However,the highest score is still less than 0.6,indicating that the whole habitat rarity is generally at a low level in the study area.(6)The habitat quality pattern at county scale has obvious spatial-temporal differentiation characteristics.Xunyi county has the best habitat quality,and Liquan county has the most significant improvement in habitat quality among 14 counties(cities and districts).The habitat quality score in southern cities and towns is relatively lower,and there is a certain spatial agglomeration of habitat quality in each county.Global Moran's I decreases first and then increases,indicating that the spatial agglomeration of habitat quality weakens first and then increases.The high-quality habitats areas are surrounded by each other and the low-quality counties have the same situation,which is consistent with the characteristics that northern part of this study area being higher than the southern part.(7)The change of habitat quality in the study area is mainly affected by the landscape pattern change.Considering its influencing factor,priority can be given to increasing landscape patch areas with good habitat quality,such as forest,grassland and water,etc.The emphasis is on protecting the landscape types with good ecological effects.At the same time,carrying out the road and forest belt greening and ecological corridor construction so as to alleviate the negative effects of human activities and landscape fragmentation.While continuing to implement the existing ecological construction measures,the protection and construction should go hand in hand.Promote the ecological environment of whole city,thereby to realize the coordinated development of landscape pattern and ecological environment.