Simulation Study On The Configuration Of Shelter Forest In The Ulan Buhe Desert Of The Yellow River

The natural conditions in the Ulan Buh desert of the Yellow River are harsh,and mobile sand dunes are widely spread.A large amount of sand blows into the Yellow River each year,which causes the Yellow River to be blocked and the river bed to be raised,which seriously threatens the safety of people’s lives and property,and restricts the sustainable economic development.At present,the protection forests on the Yellow River in Ulan Buh desert coast are severely aging and dead,and the preservation rate is less than 20%.It is urgently needed to renovate.Therefore,the construction of a shelter forest system based on forest belts is of great significance for mitigating wind and sand disasters and improving and restoring the good ecological environment of the Ulan Buh Desert of Yellow River.In this study,the native trees of Pinus sylvestris var.mongolica,Populus sylvestris,Xinjiang Populus sylvestris,Salix spp.,Salix matsudana,Haloxylon ammodendron,flower sticks,Nitraria sylvestris,Artemisia ordosica,and P.sylvestris were selected as the research objects in this study.Based on the analysis and research status of domestic and foreign protection forests,according to tree species composition(pure forest type,broad-leaved arbor-shrub mixed forest type and conifer-broad-tree arbor mixed forest type),forest age(low age,middle age and high age)and plant spacing(low Density,Medium Density and High Density)have designed 81 types of protection forest configuration models in 3 categories.Through wind tunnel simulation tests,the wind speed frequency distribution,wind speed flow field,and windbreak efficiency of windbreak and sandfixation forest belts of different heights and densities are analyzed.Explore the windbreaking effects of different configurations of windbreaks and sand-fixing forest belts,and The typical forest belts were screened,and the wind tunnel test was used to analyze the sand transport volume,wind erosion rate,and dust fall distribution.Based on the comprehensive wind and sand resistance experiment results,a new model of protection forest configuration in the Ulan Buh desert of the Yellow River is proposed,which provides a theoretical basis for the restoration and reconstruction of the protection forest along the Yellow River.The main conclusions of this study are as follows:(1)The windbreak ability of arbor shrub mixed forest belt is higher than that of arbor pure forest belt and shrub pure forest belt.The forest belt consisting of Artemisia ordosica,Tamarix chinensis Lour,Elaeagnus Angustifolia,Salix matsudana Koidz,Populus alba var.pyramidalis Bge and the forest belt consisting of Artemisia ordosica,Tamarix chinensis Lour,Elaeagnus Angustifolia,Salix matsudana Koidz,Pinus sylvestris var.mongolica Litv have outstanding windproof ability.The windbreak efficiency of the forest belt increases with the belt height,and the area with the best windproof efficiency moves backward with the belt height increase.Density weakens its impact,and the windproof effect of the leeward side of low dense forest is better than that of sparse forest at the same height.(2)The sand fixation capacity of the mixed forest belt is better than that of the broad-leaved forest belt,pure coniferous forest belt and shrub pure forest belt.At the same wind speed,the higher the forest belt,the smaller the soil wind erosion rate,and the greater the wind speed,the higher the forest belt The more obvious the effect of reducing soil wind erosion;the dustfall increased with distance after different configuration of forest belts,and the total dustfall was lower than that of pure forest-type forest belts.The amount of soil sediment transport and wind erosion rate of different protection forest configuration modes increase with the increase of wind speed,and the soil wind erosion under the forest belt cover is less than that of bare surface.(3)The coniferous broad-leaved tree shrub mixed forest belt is an ideal configuration mode of the protection forest in the Ulanbuhe desert section of the Yellow River.Comprehensively considering the wind protection effect and sand fixation effect of different configuration forest belts,as well as the special geographical location and climatic environment of the Ulan Buh desert of the Yellow River,without considering the water conditions,the study believes that the multi-species tree-shrub mixed forest belt: Artemisia ordosica,Haloxylon ammodendron,Tamarix chinensis Lour.,Salix matsudana Koidz,The forest belt composed of Artemisia ordosica,Tamarix chinensis Lour.,Elaeagnus Angustifolia,Salix matsudana Koidz,Populus alba var.pyramidalis Bge is the optimal tree species selection for sand-blocking forest belts in the Ulan Buh desert of the Yellow River.At the same time,the height of the forest belts was limited at the beginning of the forest belt construction.Increasing the density of the forest belt can effectively reduce the amount of wind and sand into the yellow.With the increase of the height of the forest belt,proper thinning increases its permeability and maintains the windbreak and sand-fixing capacity of the forest belt and the woodland water balance.