| Liangucheng National Reserve is an important nature reserve which is located in Minqin,Gansu Province of Northwest China.Minqin oasis is surrounded by the reserve.It is a main source of sandstorm and one of the worst areas of sand dust in China.Minqin oasis is located between Badain Jaran Desert and Tengger Desert.It wedges between the two deserts,hindering the closure of the two deserts.Because of this,the ecological status of Minqin oasis is extremely important.Liangucheng National Reserve is located in the desert area around Minqin oasis.The establishment and development of the reserve is of great significance to the improvement of the natural environment in Minqin Oasis and its surrounding areas.Due to the vulnerability of its desert ecosystem,the reserve is easy to be affected by many factors,such as desertification,the expansion of surrounding population and other factors.The situation of ecological environment is very severe in the reserve.It is urgent to strengthen its protection and management.The analysis in the reserve can provide scientific basis for fixed-point control of desert,and the basic data of vegetation community and soil characteristics is useful for ecological restoration and sustainable development of regress desert grassland in the reserve.In order to explore the basic characteristics of vegetation community and soil properties in arid desert area around Minqin oasis and to improve the natural environment of arid desert area.In this paper,the landscape pattern index method was used to analyze the vegetation community pattern of Liangucheng National Reserve,and the vegetation community situation of the reserve was explored from three aspects(patch stability,landscape fragmentation and landscape diversity).We collected soil from different vegetation types and landforms,and measured soil physical and chemical properties(such as p H,organic matter,water content,nitrogen,phosphorus and potassium)in laboratory.The traditional statistical method,geostatistical method and spatial analysis method were used to explore the basic characteristics of soil and vegetation communities with their relationship in the study area.The results are as follows:(1)The general characteristics of vegetation community landscape structure were analyzed.The results show that there are 13 types of vegetation patches in Minqin Liangucheng National Reserve,covering an area of about 6.5 hectares,accounting for only16.33%of the total area in the reserve.The number of patches of Nitraria tangutorum,Caragana korshinskii and Nostoc flagelliforme is the largest among the plant communities.The area of Nitraria tangutorum is the largest,which is about 1.8 hectares,accounting for 4.5%of total area of the reserve,and the patches of Nitraria tangutorum are scattered.The communities with higher marginal density include three communities of Nitraria tangutorum,Caragana korshinskii and Nostoc flagelliforme.(2)The patch stability and vegetation fragmentation of the reserve were analyzed.The patch stability of Ephedra sinica Stapf was the highest among these plant communities.Fractal Dimension Index and Landscape Shape Index of this community were the smallest among the communities,which were 1.0215 and 1.2076 respectively.The shape of Ephedra community was the closest to regular pattern,and the community's stability was the highest among the plant communities.Shannon's evenness index of Liangucheng Nature Reserve is low,which is 0.2962.The distribution of different types of patches in the landscape system is uneven and scattered.Shannon's diversity index is high(which is 0.7818)and Simpson's diversity index is low(which is 0.2956)in the reserve,the landscape abundance and diversity of Liangucheng Nature Reserve are high.The patch size of the nature reserve is uneven and the patches with the area of more than 50 hm~2 are dominant,accounting for 83.02%of the total area of the patches.The overall fragmentation degree of the community landscape is small.(3)The correlation study of soil physical and chemical properties shows that:the soil in the nature reserve is alkaline soil and the soil salt content fluctuates greatly.The soil conditions are poor with low water content and nutrient content.Soil physical and chemical properties are correlated with each other,and are not affected by soil p H and salt content.The results of geostatistical analysis of soil elements show that:the measured soil elements have certain spatial distribution characteristics and their spatial distribution patterns are similar in many regions.The spatial autocorrelations of soil total phosphorus and p H are the strongest.The spatial autocorrelation ranges of soil properties are mostly between 200 m and 600 m.The soil conditions in the north of the reserve are the best,especially near Qingtu Lake.the soil conditions in the middle are the worst.(4)The main geomorphic types of the reserve are sandy land,Gobi,hilly land,beach land,saline-alkali land and wetland.Among them,the soil moisture content of wetland is the highest,which is 7.05%,and the p H of hilly land is the highest,which has the value of 8.10.The values of soil properties in saline-alkali land are highest in many indexes,the indexes are as follows:the electrical conductivity is 293.48 us/cm,the content of soil organic matter is16.96‰,the content of total nitrogen is 1.13 g/kg,the content of nitrate nitrogen is 542 mg/kg,the content of available phosphorus is 21.8 mg/kg.In addition,the content of ammonium nitrogen(14.20 mg/kg)and the content of total phosphorus(0.35 g/kg)of the soil in sandy land are the highest.And the content of total potassium in beach soil was the highest which is4.41 g/kg.Among these geomorphic types,beach land has the best soil conditions with low salt content,high soil moisture and good nutrient conditions,and the content of organic matter and other soil properties are high.(5)Except for soil electrical conductivity and nitrate nitrogen content,the values of soil physical and chemical properties in the vegetation patches of Liangucheng Nature Reserve are small with small variation ranges.And there is little difference among the soil properties of different vegetation types.Among them,the soil conditions in the area where Zygophyllum xanthoxylon(Bunge)Maxim.and Potaninia mongolica Maxim.are located are the best.The salt content in the area is the lowest among the plant communities,the soil moisture is at the medium level,the soil organic matter content is the highest,and the content of total phosphorus and potassium is also very high.These two plants require relatively high soil nutrients.The adaptabilities of the communities of Reaumuria songarica,Tamarix chinensis and Zygophyllum xanthoxylon(Bunge)Maxim.are poor.The ranges of the values of soil physical and chemical properties in the area are very small.And the distribution area of the two plant communities is small.The communities of Haloxylon ammodendron,Nitraria tangutorum,Artemisia desertorum and Caragana korshinskii have the strongest adaptability to the environment of the nature reserve.The soil properties in the region where these plant communities located are large in scope.And the distribution area of these plant communities is large.(6)The relationship between soil characteristics and plant communities in different small areas of the nature reserve was analyzed,the results show:in the study area,when FRAC(Fractal Dimension Index)and LSI(Landscape Shape Index)of the reserve region are small,the content of soil available potassium is low,and the p H of the soil is high.When the landscape diversity level is high,and the soil p H is low,the content of total nitrogen and available phosphorus of the soil is high.And when the Patch Cohesion Index is high,there is small patch density.The number of scattered patches is low,and the water content and total nitrogen content of the soil is low.The soil p H is high. |
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