Soil Quality Evaluation And Improvement Suggestions For Typical Difficult Sites Of Afforestation In Beijing Plain

In 2012?2017,the afforestation project afforested a total area of 1 million 170 thousand mu in Beijing,which increased the forest coverage rate to 26.8%in the plain area and achieved good ecological and environmental benefits.However,a large number of plain afforestation distribution in the abandoned gravel pit flood land,difficulties in sustainable and healthy operation.Therefore,chemical and biological system improvement measures,combined with the restriction factor of typical difficult site key construction,creating soil improvement technology system of Beijing plain afforestation is typically need in mading low maintenance of plain afforestation as well as high demand for sustainable and healthy operation comes true.Through the sampling survey of soil samples of typical difficult sites,analyzed the physical and chemical properties of the data,then use the weighted matrix and the common f(x)to set that construction of soil quality evaluation system and analysis restrictive factors of corresponding typical difficulties,finally give each typical difficulties the soil quality improvement suggestions.The soil of Tongzhou Tai Lake area,the soil of Shunyi Shunping Road area,the soil of the Daxing Ying Hai area and the soil of the Miyun West fields in the area are above 0.5 points.Among them,the first score of the soil displacement in the Tongzhou Lake area is 0.5279 points,followed by the Shunyi Shunping Road area.The soil,with a score of 0.5256 points,has a score of more than 0.4 points,including soil in Fengtai Huifang area,soil in Changyang area in Fangshan,soil in northern Huairou area of Huairou,soil in Xiji area of Tongzhou,and soil in the locust area of Fengtai,and the soil quality evaluation of Changyang area of Fangshan in the front,with a score of 0.45 points.In order to score 0.4878 points and 0.4688 points in turn,the soil in Fengtai locust area is superior to the soil in Changyang,Fangshan.The area with a score of 0.45 points is the soil in northern Huairou,with a score of 0.4182 points and the soil of Tongzhou Xiji area,with a score of 0.4170 points,and the only soil below the score of 0.3 points is the village of Daxing Zang,which is below the score of 0.3 points.It is also the smallest area in the 9 regions,and the difference between the quality of the soil at the previous level is also very large,and the total score is 0.2490 points.The overall order is Tongzhou Tai Lake>Shunyi Shunping road>Daxing YingHai>Miyun West TianGeZhuang>Fengtai Huai house>Fangshan Changyang>Huairou north house>Tongzhou West Collection>Daxing North Zang village.On the whole,the conditions of afforestation sites in the plain of Beijing area are quite different,and corresponding measures should be adopted to improve the conditions for different restrictive factors.The main limiting factors of soil physical properties are 3 points:(1)the soil layer is thin,and the soil layer in some areas is only 20?30cm,which seriously restrict vegetation growth.(2)soil sand is strong,and water as well as fertilizer conservation is poor.(3)there are large stones in the soil.The above factors should be improved by means of replacing soil with soil,artificial fertilization and removing stone or applying soil structural modifier.The contents of soil nutrients,including soil organic matter,total nitrogen,available phosphorus and available potassium,are in the four to five grades in most areas.Nutrient deficiency is not enough for vegetation growth.The above factors should be improved by adding organic manure,green manure,feeding earthworms and chemical modifiers.The soil in the investigated area is not salinization,and the pH value of the soil is all weak alkaline to alkaline.Therefore,the pH value can be reduced by artificial fertilization or plant growth of development.The heavy metal content of soil is higher than the background value of soil heavy metal environment in Beijing,but it is far below the screening value.It is not necessary to take measures to control it,but attention should be paid to controlling the application amount in the application of sludge,which may contain more heavy metals.