Width Identification And Dynamic Analysis Of Transition Zone Among Different Sandy Landscape Types

Ecological transition zone is a key area for terrestrial ecosystems to respond to global climate change,which usually has high environmental heterogeneity,and the sum of ecological factors and biodiversity are in the critical state of phase transition.the ecological function,structure and ecological process here are very complex,which play a more "indicative" and "early warning" role in global change.The discrimination of the width and location of the transition zone is the premise and basis for an in-depth understanding of the ecological ecotone.Horqin Sandy Land is located in the semi-arid area of northern China.Under the influence of precipitation and wind,the ecotone between different landscape types changes obviously.In the existing research on the recognition of interlaced zones,good results have been obtained based on a variety of different methods,but the results depend on the spatial scale of the data and the process of data acquisition is time-consuming and laborious,and the calculation process is more complex.From the perspective of research methods,the inflection point of landscape boundary change can be quickly found by using remote sensing images,which is a more efficient and fast identification method.Therefore,based on satellite remote sensing images,land satellite(Landsat)series satellites and UAV remote sensing images(near-ground remote sensing based on community scale),the position and width of transition zone between different landscape types are calculated by using GIS and RS techniques,and the seasonal variation(April-August 2017)and interannual variation(2000-2020)of three typical sandy land landscape transition zone width in Horqin sandy land are analyzed.The results show that:(1)NDVI is a good starting point in the process of defining the boundary width between different sandy landscapes,because no matter what the type of adjacent landscape is,the NDVI transition at the boundary has an obvious attenuation process,and the boundary thickness can be captured by the inflection point.At the same time,the spatial distribution pattern of edge species is analyzed by ground UAV remote sensing to explain and verify the fluctuation of landscape boundary thickness.(2)The boundary thickness formed between different boundary types and mobile sand dunes is different,and the boundary thickness of the two kinds of boundary shows an increasing trend in terms of seasonal variation.Precipitation has no significant effect on the boundary thickness of mobile sand dunes and fixed sand dunes(P < 0.01),but has a significant effect on the boundary thickness of semi-fixed sand dunes and mobile sand dunes(P < 0.05).In the interannual variation,the boundary thickness of the two kinds of boundary thickness shows a fluctuating increasing trend.Precipitation has a significant effect on the boundary thickness of mobile sand dunes and fixed sand dunes(P < 0.05),but has no significant effect on the boundary thickness of semi-fixed sand dunes and mobile sand dunes(P < 0.05).This is due to the spatial distribution characteristics of marginal species.(3)The spatial distribution of avant-garde vegetation is the factor affecting the change of landscape boundary width.When the scale is greater than 8m or 20 m,there is no spatial distribution of Artemisia mandshurica and Artemisia mandshurica at the edge of the mobile dune,which contributes negatively to the NDVI calculation,which leads to the decrease of the boundary width.(4)The curvature has an important influence on the landscape process on both sides of the transition zone.When the curvature increases gradually,one side of the fixed sand dune shows a state of convergence and contraction,while the landscape of mobile sand dunes on one side of the transition zone tends to spread and disorder.(5)The area of mobile dunes in the study area gradually decreased,the area of semi-fixed dunes increased at first and then decreased in normal distribution,and the area of fixed dunes decreased before 2010,and then increased.The areas of semi-fixed dunes,mobile dunes and fixed dunes in the semi-fixed dune-mobile dune transition zone show a decreasing trend.In the transition zone between fixed dunes and mobile dunes,the area of semi-fixed dunes decreased,while the areas of fixed dunes and mobile dunes decreased at first and then increased.