Study On The Dynamics Of Water And Salt In Saline Soil And Amelioration Of Saline Soli By Salt-resstance Plants In Bohai Bay

The salinized soil is widely distributed in our country,which does not only influences the agricultural and forestry production, also damages ecological environment.For this reason, it is very important to treat and develop saline-alkail soil.Both evolution of salinized soil and prevention of soil secondary salinity are based on water and salt dynamic in soil, while biological measure can effective meliorate salinized soil.Four locations as Tanghai, Dagang, Huanghua, Dongying were chosen with 6 sampling spots each location from north to south throughout Bohai Bay, and soil samples of 0²0cm,20⁴0 cm,40⁶0 cm,60⁸0 cm soil layers were monthly collected using soil sampler from March to October in 2009,besides,. soil water content,soil electrical conductivity and salt ions concentration were analysed.In order to explore Ameliorative effect of saline-alkali land through planting Nitraria tangutorum, Pyrus betulaefolia, Shepherdia argentea in Tianjin coastal region, the amount of microorganisms, nutrient content and salt content of soil in the three woodlands were studied after three plants were afforested for 4 years.The main results were summarized as follows:1.There was difference in soil water content between 4 locations,The soil water content in 4 locations was ranked from Dagang to Dongying,Huanghua,Tanghai. There were difference in soil water content monthly for 4 locations. On the whole, soil water content was the lowest in June, the highest in Septemper. Soil water content was increased with the depth, and the rangeability of 0²0 cm soil water content was greatest.2. Except HCO3-, there was difference in other 6 salt ions and electrical conductivity between 4 lccations. The monthly variation regularity of electrical conductivity and Cl^- content was similar. On the whole, The fluctuate of electrical conductivity and various salt ions content was greater. Soil salt content in Dongying and Huanghua concentrated in the surface horizon, soil salt content was highest in 0²0 cm soil layer, soil salt content is almost identical in 20⁸0 cm soil layer. 3.Electrical conductivity was positively correlated with Na+ content and Cl^- content in 4 locations, it shows soil salt content in Bohai Bay determined by Cl^- and Na⁺ content. In Huanghua and Tanghai, there was a negative relation between HCO3– and Ca²⁺,Mg²⁺.,it suggests that the more Ca²⁺and Mg²⁺ contents,the less HCO3–content. The dynamics laws of soil water salt was different beween 4 locations.4. Total soluble salt content was calculated by sum of all ions in every location, So we can see that Dongying belongs to extremely severe saline soil area,Huanghua belongs to severe saline soil area,Dagang and Tanghai both belong to middle severe saline soil area. The formulas of the regression relations were set up though the relation between total salt and electrical conductivity, R2 are above 90% in 4 locations, degree of fitting was well, so we can calculation soil salt content quickly by using the formulas.5. Cluster analyses indicated that the Bohai Bay saline soil was divided into 3 kinds, the southern part of Bohai Bay was a type represented by Dongying;the middle part of Bohai Bay was a type represented by Huanghua; the northern part of Bohai Bay was a type represented by Dagang and Tanghai.6. Through planting Nitraria tangutorum, Pyrus betulaefolia, Shepherdia argentea in Tianjin coastal region, 4 years later ,the amount of microorganisms, nutrient content increased significantly,while the salt content of soil sharply declined.It showed that the three species of salt-resistance plant could accelerate edaphic desalination, improve soil structure,improve soil fertility, The improvement was enormous. Over all, N. tangutorum is the best plant for saline-alkali soil improvement, the second-best is P. betulaefolia, S. argentea is relatively poor.