| Minqin liangucheng Nature Reserve,which accounts for 1/4 of Minqin area,is the largest desert ecological nature reserve in China.Minqin oasis is the main source of sandstorm,and it's one of the most serious areas of floating dust,blowing sand and sandstorm in China.It is locateded between Badain Jaran Desert and Tengger Desert,plays an important role in blocking the two deserts from converging.It is a "bridgehead" on the sandstorm line in Northwest China.The scientific and effective management of Liangucheng Nature Reserve is of great significance for protecting the ecological environment of Minqin Oasis and the whole Shiyang River Basin,and it's important for maintaining the regional ecological balance.The study on the evolution characteristics of land use/cover and landscape pattern in Liangucheng Nature Reserve can provide scientific basis and guidance for the construction and management of the reserve.Based on remote sensing and geographic information technology,using the TIFF remote sensing images of 2002,2009,2013,2016,2020 and Landsat images of 2002,2009,2014,2016,2018,combined with field survey and ecological monitoring data,this paper analyzes the land use/cover change,landscape pattern evolution characteristics and vegetation cover change trend since the establishment of Liangucheng National Nature Reserve in Minqin County,Gansu.The results are as follows:1.Using transfer matrix to analyze the change of land use structure in the reserve,the results show that:The development of the reserve can be divided into three stages: the initial stage of establishment(2002-2009),the period of protection work(2009-2013),and the period of consolidation and development(2013-2020).The main land types in the reserve are grassland,sandy land and forest land,accounting for 16%,30% and 48% of the reserve area respectively.Compared with 2002,the area of grassland,cultivated land,forest land and saline alkali land in the reserve increased by 2.23%,24.29%,0.10% and 0.20% respectively,while the area of construction land and sandy land decreased by 18.42% and 1.79% respectively.And the area of bare land remained unchanged.After 2013,the development trend is stable and the specific change trend is: the area of forest land and grassland grows slowly,and the area of cultivated land,sandy land and construction land declines.2.The landscape pattern index method was used to analyze the evolution characteristics of the landscape pattern in the study area.The results showed that the landscape pattern index of different areas in the reserve changed few,and there were significant differences between different areas except index FRAC(1.04-1.11)and index AI(72-99).The order of NP is:grassland > arable land > forest land > sandy land > bare land ? saline alkali land ?construction land,the order of LPI is: forest land > sandy land > grassland > bare land >arable land > saline alkali land > construction land,and the order of LSI is: arable land >grassland ? forest land > saline alkali land > sandy land ? bare land ? construction land.Generally speaking,the nature reserve is dominated by dominant patches with good connectivity;it also has many small patches.Affected by human activities and sandstorms,the land types are mostly clustered and distributed,the patch boundary is relatively regular,the shape is regular,and the land use types and species diversity are not high.3.the main driving forces of land use type and landscape pattern change in the reserve are as follows: favorable transformation(sand pressing and afforestation,etc.)of the reserve by the staff,weather factors such as sandstorm weather conditions and annual evaporation,vegetation growth conditions,temperature and precipitation that affect vegetation growth.4.The vegetation index of the reserve is extracted and the vegetation coverage is calculated.The results show that the vegetation coverage of Liangucheng Nature Reserve is mainly of extremely low coverage and low coverage,the proportion of which decreases year by year,from 77.46% to 73.67% in 2002-2018;the proportion of medium coverage and medium high coverage increases by 3.17% and 1.31% respectively,the proportion of high coverage decreases by 0.68%,and the proportion of high coverage decreases by 0.68% The coverage vegetation may not be suitable for the current ecological environment of the reserve,and the future work should be mainly to increase the medium and high coverage vegetation.The vegetation coverage of forest land(0.35%-0.44%)and grassland(0.19%-0.26%)is less than that of cultivated land(0.66%-0.94%)and construction land(0.36%-0.42%).The ecological restoration of forest land and grassland should be paid attention to in the future work. |
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