Desertification Controlling And Its Effect Assessment Of Huangyangtan Sandy Land In Xuanhua County, Hebei

Desertification is the main manifestation of desertification area in the north of China. In the past some sandy land, such as Huangyangtan Sandy Land, were paid inadequate concentration, which is the important geographical location. By the field investigation and sampling, indoor samples analysis and comprehensive analysis, the main measure on restoring and controlling Huangyangtan Sandy Land was systematic researched from the following aspects which included the wind-breaking and sand-binding effects, laws of soil moisture variation, succession rule of vegetation and soil fertilizing effects. Its result will be expected to play typical demonstration effect to perfect and improve the control projects to the area and sandstorm source area around Beijing and Tianjin.Yanghe's diluvial chapada and all levels terrace have large of material containing sand in the north of Huangyangtan sandy land, which have low coverage. As coupling effect of material containing sand with heavy wind and frequent wind, sandy land were formatted and developed. According to the grain size data, the dust average output of Huangyangtan Sandy Land whose φ-value is more than 7 is estimated at 3.23×10²t a^-1. The output was contributed to the sand dust storms in Beijing. Based on landscape pattern analysis, integrate natural and artificial factor, the main cause of desertification enlargement is the result of land misusing by human.Young farmland shelterbelt still not playing its expected role at the protection farmland, which should coordinate the covering and mulching measures can effectively control farmland soil erosion. All vegetation's wind-breaking effect is closely related to stand structure. Among the different vegetation restoration measures, the roughness of shrub-grass complex forest is the biggest, then the grass's, the forest land's is the least. The soil erosion effect of different vegetation is related with stand disposition, wind protection effect and herb cover degree under the forest and so on.The soil moisture's vertical distribution and rules of seasonal variations on the different plant condition show that the grassland have good water conservation function, the deep level soil water content of Populus alba var. pyramidalis and Elaeagnusangustifolia forest appear exhausted trend, soil water status of shrub water content is situated between the two. Eco-mat and plant measure were adopted to control shift sandy land for the first time in the domestic and abroad in the area. Soil water content under the eco-mat is dependent on the strong and weak diaphragming function of rainfall and evaporation in physics aspect, the influence of soil temperature effect to evaporation and plant transpiration and so on. The soil average moisture content is higher than the shift sand in July and August, other month are lower than the shift sand, the soil water content in deep layer of eco-mat cannot obtain the supplement for a long time. So we must improve the laid measure.During the process of vegetation restoration from the shift sand to half fixed sand and the fixed sand in Huangyangtan, the phenomena of species replacement is obvious. The different stage corresponds the different superiority population, plant family and genus composition and life-form plant. Artificial forest land may speeds up or delays natural plant succession process.The different biological measure or the biological measure combine project measure both has the improvement effect on sand soil fertility condition. Soil fertility condition of decertified grassland fencing 26 years has improved obviously. In the artificial pure forest built in 2001, the C. microphylla forest improvement effect of soil improving is best, the following in turn is Elaeagnus angustifolia, Platycladus orientalis, Salix gordejevii, P. alba van. pyramidalis. Mixed forests with different tree species and plant with different absorbency on N-P rotated have the function on improving the sandy land.