Extraction And Analysis Of Vegetation Coverage In The Source Region Of The Yellow River Based On The Multiple Endmember Spectral Mixture Analysis

Vegetation is an important part of land ecosystem environment.The change of the vegetation coverage has an important meaning for the ecological system and land desertification.As one of the essential component part of the Three-River Headwaters National Park,monitoring the vegetation coverage of the Yellow River Headwaters Region plays an key role in ecosystem system of the Three-River Headwaters Region.Based on Landsat satellite land as the main data source,supplemented by the Yellow River source area DEM data,meteorological data and 1:1000000 vegetation classification figure and soil classification figure,combined with Multiple Endmember Spectral Mixture Analysis extracted respectively 1996,2000,2004,2006,2008,2013,2015,when the Yellow River source area seven 44000 km~2 of vegetation coverage,The variation trend of vegetation coverage was analyzed by linear regression analysis and transfer matrix.At the same time,based on the geodetector model,analyzing the climatic factors such as annual average temperature and annual average precipitation and non-climatic factors such as elevation,slope,land use pattern and vegetation form quantitatively.As follows are some results:(1)The MESMA model adopted in this paper avoids the Liner Spectral Mixture Analysis's limitation in which the pixels of the model are all the same endmembers,because it takes into account the phenomenon of"the same object and different spectrum".In addition,the MESMA model can classify the vegetation types and then extract the poisonous weeds in the study area.(2)In terms of spatial distribution,medium and low vegetation coverage was the main part of the source region of the Yellow River's the vegetation coverage.It decreased from southeast to northwest gradually.In terms of time distribution,the vegetation coverage showed an overall improving trend from 1996 to 2015.From 1996 to 2004,the vegetation coverage showed a decreasing trend on the whole,and the bare land showed an increasing trend on the whole,while the low,middle and low cover types basically remained unchanged on the whole,and the vegetation coverage was mainly transformed to the lower vegetation coverage types.And the high coverage type showed a decreasing trend.From 2004 to 2015,the vegetation coverage showed an overall increasing trend,which was mainly represented by the overall decreasing trend of bare land,while the low,medium and low cover types basically remained unchanged,and all of them mainly shifted to the higher vegetation coverage types.And the high coverage type showed an increasing trend.(3)The poisonous weeds'area in the source region of the Yellow River increased from16060 km~2 in 1996 to 22942 km~2 in 2015,with an overall change of 6882 km~2,indicating that the area of poisonous weeds increased with the increase of vegetation coverage,so it had a negative impact on the development of local animal husbandry.(4)In terms of climatic factors,average annual precipitation(q value 0.207)was the main influencing factor for spatial distribution of FVC in the source region of the Yellow River.In terms of non-climatic factors,soil type(q value 0.21)was the dominant factor.The interaction of soil type and precipitation,land use,and annual mean temperature and annual mean precipitation had great influence on the spatial distribution of vegetation coverage.In general,the relative influence of vegetation coverage distribution is the soil type>annual average precipitation>vegetation type>land use type>annual average temperature>elevation>slope,and the interaction of the two factors is stronger than the single factor.