Impact Of Oasis-Desert Ecotone Protection System On Dust Deposition

The oasis-desert ecotone is the connection area between the oasis and the desert ecosystem,and the stability of its ecosystem directly affects the evolution direction of the oasis and desert.The dust activities in the oasis-desert ecotone are frequent and strong,and the resulting dust deposition will pose a great threat to the oasis and promote the spread of desertification.Creating a protection system in the oasis-desert ecotone can effectively reduce the dust deposition in the oasis,improve the ecological environment of the oasis,and ensure the ecological and production safety of the oasis.The dust deposition characteristics in the protection system of the oasis-desert ecotone can directly reflect the effect of regional sand prevention and control,and are of great significance for desertification prevention..In order to study the impact of the oasis-desert ecotone protection system on dust deposition,the Gelintan oasis in the southeast edge of Tengger Desert was chosen as the research object,and the protection system extending from the outer edge of oasis to the inner edge of oasis was established.The protection system is composed of sand barrier sand-fixing belt(SZ),shrub and herbaceous plant belt(GC)and farmland protection forest network(NL).In the bare sand area(CK)and the protection system,dust deposition collectors are set up near the ground,and the dust deposition activities in the bare sand area and the protection system are continuously observed for one year.Through field investigations and indoor experimental analysis,study the law of dust deposition and the response to the main meteorological factors in the oasis-desert ecotone protection system,by testing the grain size characteristics of dust deposition,the source of dust in the study area is judged,and theimpact of the oasis-desert ecotone protection system on dust deposition is studied.The results are as follows:(1)There were significant differences among CK,SZ,GC and NL(P<0.05),and the amount of dust deposition in April is the most,and in December is the least.The seasonal variation trend of the dust deposition in each protection belts is shown as spring>summer>autumn>winter.During the process of moving from the quicksand area to the farmland along the main wind direction through the protective system,the amount of dust deposition is CK>SZ>GC>NL,the amount of dust deposition in the farmland is greatly reduced.(2)After the sand-carrying air flows from the quicksand area to the oasis through the oasis-desert ecotone protection system,the sand composition in non-dust weather conditions gradually decreases and the silt composition gradually increases.In dust weather conditions,the composition of medium sand gradually decreases,and the composition of ultra-fine sand gradually increases.Under the influence of the protection system,the average particle size of the dust deposition in the farmland gradually becomes finer,the sorting property gradually becomes worse,the skewness changes from near symmetry to negative,and the kurtosis has no significant change.(3)In the non-dust weather,the sand carrying air flow from the bare sand area through the protection system to the farmland,the source of the dust deposition changed from the moving particles near the surface to the suspended particles.Under the condition of dust weather,the main source of dust deposition is near surface sand particles,but affected by the protection system,the content of suspended particles in the deposition is gradually increasing.(4)The correlation between the amount of dust deposition in CK,SZ,GC and NL is relative humidity,average wind speed and the days of dust weather is well.The main meteorological factors that affect the change of dust deposition in the protection system are the average wind speed and days of dust weather.The sum of the relative contribution rate of the two factors ismore than 50%.There was a significant linear positive correlation between the amount of dust deposition and wind speed in each protection zone(P<0.05).