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在奇台县绿洲中部平原区和绿洲沙漠交错带选择不同耕种时间的农田,分析其剖面土壤可溶性总盐、pH值含量随耕种时间的变化。探讨在地下水埋深不断下降的过程中,不同发展阶段农田土壤盐渍化的时空变化规律。研究表明:奇台县绿洲地下水埋深已低于影响地表盐渍化的地下水埋深临界值(5m),地下水矿化度低于3g/L,研究区整体处于有利于土壤盐渍化逆向演替的环境。土壤含盐量与地下水埋深关系最为密切,地下水埋深在3-5m时,土壤脱盐速度最快,大于5m时,含盐量减少的速率明显降低。土壤盐渍化逆向演替具有时空特征。时间特征表现在,无论农田在绿洲的什么位置,耕种时间越长,土壤含盐量越低,盐渍化逆向发展的越好。当农田耕种时间和地下水埋深低于临界值的时间超过20年时,盐渍土基本可以自然恢复为非盐渍土。空间特征表现在,由绿洲下部向上部,土壤盐渍化逆向演替阶段逐渐向高级过渡。
The farmland of different tillage time was selected in plain area of central oasis in Qitai County and ecotone of oasis desert to analyze the change of total soluble salt content and pH value in the soil profile with the tillage time. The spatial and temporal variation of soil salinization in farmland at different stages of development are discussed during the process of declining groundwater depth. The results show that the groundwater depth of Qitai Oasis is lower than the threshold value of groundwater depth (5m) which affects the surface salinization, and the salinity of groundwater is less than 3g / L. The study area is in the reverse of favorable for soil salinization For the environment. Soil salinity has the closest relationship with groundwater depth. When the groundwater depth is 3-5m, the soil desalting speed is the fastest. When the soil salinity is more than 5m, the rate of salt reduction obviously decreases. The reverse succession of soil salinization has the characteristics of space-time. The temporal characteristics are manifested in that no matter where the farmland is in the oasis, the longer the cultivation time, the lower the salinity of the soil, the better the reverse development of salinization. When farmland cultivation time and groundwater depth are lower than the critical value for more than 20 years, saline soil can basically recover to non-saline soil. Spatial characteristics are characterized by the gradual transition from the lower part of the oasis to the upper part and the step of reverse succession of soil salinization.