The Change Process Of Wind-break And Sand-fixing Benefits On PLA Sand Barrier

The research’s object is Poly Lactic Acid sand barrier. Taking the wind speed, the surface erosion and deposition, soil physical properties and vegetation recovery of1m×1m、2m×2m and3m×3m PLA sand barrier for continuous measurement and observation at the southeast edge of Ulan Buh Desert from2007to2011,meanwhile taking the same specification straw sand barrier and unprotected dune as a comparison. Through several years of continuous observation and comprehensive analysis to the change of wind efficiency, near-surface erosion and deposition and soil physical properties and vegetation restoration conditions, the main conclusions are as follows:(1) The PLA and straw sand barrier can effectively reduce surface wind speed, at the same time increase the surface roughness, they are PLA> straw sand barrier>contract. With the time going, these two sand barriers protection effect are declining, but the declining of PLA sand protection ability is relatively slow; the changing degree of S wind profile of them is more and more small with the time going. Along with the increase of sand, the specifications "S" is close to control wind speeds.(2) From the analysis of soil’s stability’s changes in the barrier we can see that:PLA and straw barrier are significantly reducing year by year, the extent of PLA is smaller than straw barrier. These two sand barriers all show that the soil stability effect is reducing with the increase of sand specifications and the sand burial is serious at the east and west slope position as time goes, besides PLA sand still has certain protective ability, but straw sand barrier had all been buried by sand.(3) Through several years of continuous observation, the sand soil water content of PLA0-20cm is1.5times as average growth as straw sand barrier, the sand soil water content of PLA2m×2m is the best; the change of PLA0-20cm PLA soil bulk density is large with the time going. The sand specifications and slope position has little effect on straw barrier soil bulk density and they are not the main influencing factors; Soil hardness decrease and there is close relations between the hardness distributionit and the direction of the wind. The specification has not caused the sand soil hardness of significant change, however the slope position have effect on hardness distribution.(4) Through the investigation of vegetation restoration for five years, we can see that there is difference between these two sand barriers of vegetation restoration ability. With the time going, they all appear large sand fixation vegetation, but due to serious sand burial, they have already lost basic protection ability, the vegetation restoration ability is lower than the PLA.