Optimal Patterns Of Shelterbelt In A Vineyard Base Of The Ulan Buh Ecological Sand Industry Demonstration Region

In this study,to improve the windbreak effect of shelterbelt in ecological sand industry demonstration region and enhance survival rate and seed setting rate of grapes,typical shelterbelt in the demonstration zone is selected as the object.On the basis of analysis wind regime and surveys on shelterbelt conditions,growth indicators of vineyard shelterbelt,conditions of understory vegetation and characteristics of wind velocity are researched via field observation in the Ulan Buh ecological sand industry demonstration region,then combined with the flow field simulation in the indoor wind tunnel,the changes,distribution and acceleration rate of wind velocity,and efficiency of windbreak in different typical shelterbelt are researched,to determine the reasonable trend,tree species and spacing of forest belts,thereby optimizing the shelterbelt system in Ulan Buh ecological sand industry demonstration region and providing the reference for its research of the vineyard in the future.The main results are as follows:(1)The average wind velocity in Ulan Buh ecological sand industry demonstration region from April to July is relatively high,with 4.40 m/s as the maximum,and 2.38 m/s as the minimum.The wind direction in the area is mainly from the west and south.The growing season of grapes is from April to June,mainly with the south wind,and the dust emission wind velocity is relatively large.(2)The understory vegetation in the sheltebelt is dominated by annual herbaceous plants,as well as farmland crops and seedlings of their own tree species.The understory is mostly common sandy plants in desert areas,such as: Salsola collina Pall,Artemisia filifolia,Pugionium cornutum,and fewer bushes.Shannon-Wiener index and Pielou index of Populus alba L.var.pyramidalis Bge are the highest(0.89 and 0.78),while Shannon-Wiener index and Pielou index of Robinia pseudoacacia are the lowest(0.63 and 0.54).Simpson index and Margalef index are the highest and the lowest respectively.(3)Forest belt structure has a significant impact on the efficiency of windbreak.Based on the windbreak effect of different structures at different heights,it is concluded that the windbreak effect of widely spaced belt is relatively average,and is better than the other two belts at a height of 20 cm.Also its highest windbreak efficiency can reach 84.53%.Yet,the close spacing forest belt is better than the widely spaced belt at the height of 200 cm,and the highest windbreak effect is 64.16%.According to the investigation,the height of local grapes in the first year is about 10-20 cm,so the widely spaced forest belt is supposed to be selected.(4)Through flow field experiments of wind tunnel in typical forest belts and observations in horizontal and vertical directions,it is concluded that under various wind velocities,the average near-surface wind velocity of triangular forest belt is lower than that of the rectangular forest belt,with the difference of 0.36,1.08 and 1.75.As the wind velocity increases,the gap gradually increases.From the perspective of acceleration rate of wind velocity,forest belts of Populus alba L.var.pyramidalis Bge are more sensitive to the configuration mode.Under the 3different wind velocities,the triangular ones decrease by 81.71%,68.00% and 53.15%respectively compared with the rectangular.The gap of acceleration rate decreases with the increase of wind velocity,therefore,Populus alba L.var.pyramidalis Bge is suitable for the triangular ones,while the influence of configuration mode on the other two forest belts is not significant.From the perspective of forest lines,the average near-surface wind velocity of 4forest lines is less than that of 2 forest lines,and the windbreak effect of 4 lines is generally greater than that of 2 lines,when the differences of acceleration rate of wind velocity are 0.64,1.57,1.77.Also,the gap rises with the increase of wind velocity.Forest belts of Populus alba L.var.pyramidalis Bge are suitable for 4 forest lines,while Pinus sylvestris var.mongolica is not sensitive to the change of forest lines,and the acceleration rate of wind velocity in 2 forest lines of Robinia pseudoacacia is less than that 4 lines;The average near-surface wind velocity of the three tree species shows no obvious discipline under different wind velocities.From the aspect of the acceleration rate of wind velocity,the effect of Populus alba L.var.pyramidalis Bge on the wind velocity reduction behind forests is significantly better than that of the other two species.(5)Shelterbelt system of the vineyard is divided into 3 parts,mechanical sand barriers plus shrub belts,belts for windbreak and sand fixation(backbone forest belts)and shelterbelt network of the vineyard.By determining the trend and spacing of forest belts,as well as tree species selection,finally 1.5 m×1.5 m PLA sand barriers are selected as the mechanical sand barrier of sand-fixation belt,Populus bolleana and Locust mixed forest with 8 lines as backbone forest belts,Populus bolleana with the configuration of triangular square-grid and 4 lines as farmland shelterbelts.