Study On The Effect Of Afforestation On Windbreak And Sand Fixation In Hebei Bashang District

The soil wind erosion in Bashang area of Hebei is serious,and is the main source of wind and sand in Beijing-Tianjin area.To windbreak and sand fixation,since the late1970s,the region has implemented a series of ecological measures,among which,afforestation is one of the main measures.In recent years,the effect of afforestation has been questioned by the death of a large area of poplar forest in Bashang area of Hebei.In order to determine the windbreak and sand fixation effect of afforestation,this paper takes Kangbao County in Bashang area of Hebei province as the research area,adopting the research methods of field observation and indoor experiment,taking the natural grassland as the control,and measures the soil physical and chemical properties?windbreak and sand fixation effect of three forest types,including the mature arbor forest,shrub forest and young arbor forest.And investigated the vegetation growth of various forest types.The main research results are as follows:(1)The forest land in Bashang area of Hebei is less in the west and more in the east,and woodland and shrub forest are the main forest types in this area,accounting for more than 90%of the total area of forest land.The area of forested land increased in 1980-2015,among them,The proportion of forested areas increased by 25.70%from1056.67 km~2 in 1980 to 1328.13 km~2 in 2015;the proportion of other forested areas increased by 324.39%from 9.02 km~2 in 1980 to 38.28 km~2 in 2015;the area of shrub forest decreased by 9.87%from 1230.81 km~2 in 1980 to 1109.38 km~2 in 2015;and the area of sparse forested land decreased by 23.93%from 172.88 km~2 in 1980 to 131.51km~2 in 2015.(2)In the period of“three north”shelter forest construction(1980-2000),the forest land area has decreased,among them,mainly the decrease of spare forest by 27.6%;during the period of Beijing-Tianjin wind and sand source control project(2000-2010),the forest land area in Bashang area has increased significantly.There is the largest increase in forest land,with an area increase of 24.4%;in the period of comprehensive ecological construction(2010-2015),the area of forest land did not change much.(3)The physical and chemical properties of 20 sample points in 5 groups of plots in the north of Kangbao County were analyzed.Each sample plot includes large area of natural grassland,mature arbor forest,shrub forest and young arbor forest.The results show that compared with natural grassland,a 2.27%reduction in the content of non-erosive particles(>0.85mm)in shrub forest,the content of fine particles such as clay and silt decreased by 2.42%,the soil desertification was reduced,the organic matter increased by 1.85%and the total nitrogen content decreased by 2%;18.03%reduction in non-erosive particles(>0.85mm)in mature arbor forest,the content of clay and silt decreased by 2.93%and the organic matter increased by 0.38%,the total nitrogen content decreased by 5%;a 2.23%reduction in non-erosive particles(>0.85mm)in young arbor forest,and the content of fine particles such as clay and silt particles increased by 11.06%,which aggravated soil desertification,decreased organic matter by 0.30%,and increased the total nitrogen content by 6%,which is caused by the agitation of the surface soil by the afforestation project.Overall,the long-term growth of forest irrigation caused surface soil desertification,nutrient reduction,and even gravelization.(4)A field survey of forest land status in Kangbao County shows that natural grassland grows well as a native vegetation.Compared with the natural grassland,the growing status of forest is poor and the dead rate is high.Shrubs grow better.Most of the young arbor trees have better growth status compared with the mature trees.(5)Taking natural grassland as control,the effect of windbreak and sand fixation of different types of forest land was measured.The results show that the effect of windbreak is the best in shrub forest.Shrub forest reduces wind speed by 13.92%,the windbreak efficiency is the largest,and the surface roughness is also the largest,which has the best effect of wind protection.The wind speed is reduced by 7.92%in mature arbor forest,the wind resistance is higher,but the surface roughness is lower;the wind speed of the young Arbor woodland is increased by 20.34%compared with the natural grassland,and the surface roughness is higher,but the windbreak efficiency is lower.In short,the windbreak efficiency of arbor forest is not as good as that of shrub forest.But compared with natural grassland,the effect of sand fixation is not good,and the wind erosion of adult and young arbor forest is even higher than that of natural grassland.