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Gansu Agricultural University (2017)

Study on Movement Regularity of Barchan Dunes and Its Relationship with Environment Factors along the Oasis Fringe in Minqin

石学刚

Titre : Study on Movement Regularity of Barchan Dunes and Its Relationship with Environment Factors along the Oasis Fringe in Minqin

Auteur : 石学刚

Grade : Master’s Theses 2017

Université : Gansu Agricultural University

Résumé
In order to explore the dynamic changes of the Barchan dunes and its relationship with environment factors,eleven typical Barchan dunes were selected at the oasis fringe in Minqin.Use the goolge earth to measure the morphological parameters of the Barchan dunes,and made a comprehensive investigation and observation to environment factors around the dunes.Sometimes,the correlation was analyzed between the data and environment factors.The following results were obtained.(1)On the 11 Barchan dunes that have been selected along the Oasis Fringe in Minqin 72.7% of Barchan dunes area increased,63.6% of dunes windward slope lengthincreased,27.3% dunes leeward slope length decreases,54.5% of dunes width increases,The Dunes height increased trends,an average annual increase of 0.1 0.5m.(2)Among eleven typical Barchan dunes were selected at the oasis fringe in Minqin,the largest movement distance and movement speed repectively are 79.9m and 11.4m/a,the minimummovement distance and movement speed repectively were34.4m and 4.9 m/a.Barchan dunes,the highest is 12.5m,the minimum is 5.2m.All dunes average width are 289.2m,the average height are 8.6m,dunes movement speed and height were significantly negative correlation(P<0.05).(3)Barchan dunes are located distribution area is flat beach land of gravel quality and more open between the dunes.On the wind of barchan dune there is average 321.7m flat sand gravel beach land,and in downwind of barchan dune there is average 578.2m flat sand gravel beach land.The windward slope beach is longer than leeward slope beach,and significant difference(P<0.05).This suggests that the Barchan dunes distribution density is smalle at oasis fringe in Minqin.The windward slope beach and leeward slope beach vegetation coverage are less than 4.8%,windward slope beach is 2.7%,leeward slope beach is 3.1%.No significant difference between windward slope beach and leeward slope beach(P>0.05).(4)The meteorological factors that affects the barchan dunes at oasis fringe in Minqin : Annual strong wind days and annual sandstorm days were very significant positive correlation effects on dunes height,annual precipitation effects on dunes height was significantly negative correlation(P<0.05).Dunes moving distance and the annual average wind speed,annual strong wind days,annual sandstorm days were extremely significant positive correlation(P<0.01),and with annual average temperature,annual rainfall,maximum principal direction was significantly positive correlation(P<0.05).The three main factors that affects the dune dynamic are annual precipitation,annual average wind speed,annual strong wind days,the annual precipitation have largest contribution rate in all climate factors.(5)The environment factors that affects the barchan dunes at oasis fringe in Minqin : Vegetation in the windward slope have a obvious affect to <6 m/s wind speed to ≥6m/s wind speed affect is not obvious,it will have a good start of sand inhibition(grains of sand start wind speed≥5 m/s).Soil water content is biggest in windward slope bottom,it is positively correlated with vegetation distribution of the dunes ;Each part of the dunes windward slope,≥4 m/s wind speed and water content were significantly positive correlation(P<0.05) ;≥4 m/s wind speed and water content were significantly negative correlation(P < 0.05).The higher the water content,the demand higher for grains of sand start wind speed,sand dunes move more slowly,and vice versa.(6)The stability factors that affects the barchan dunes at oasis fringe in Minqin:Coarse dunes underlying surface(flat sand gravel beach land),the higher soil water content in windward slope bottom,≤4 m/s wind speed,these factors increase the grains of sands to the starting wind speed,and it is the necessary condition of dunes moving slowly.The main wind direction and the main opposite winddirection is the limiting factors increase and increased.(7)The instability factors that affects the barchan dunes at oasis fringe in Minqin :≥6 m/s wind speed,less leeward slope vegetation coverage and height,the main wind direction process lead to windward slope sands from fine to coarse from dunes top to windward slope bottom,this is a key factor of dunes movement faster,the single main wind direction process is the decisive factors of dunes moving forward.

Mots clés : Barchan dunes; Minqin; Oasis fringe; Movement regularity; Environment factors; Correlation;

Présentation (CNKI)

Page publiée le 5 février 2018