Tongchuan Yaozhou Plantation Degradation And Soil Drying Mechanism And Control Measures In

The soil desiccation and revegetation deterioration are main problems about Loess plateau section improvement of the ecological environment and revegetation ecology, the reasons are that soil water shortage and the plant growth have contradiction.Yaozhou district, Tongchuan lies in Weibei arid highland Shaanxi Province, where the precipitation is little and uneven, the underground water buried is deep, water resources utilization is difficult, and evaporation of artificial locust stands consume strongly, so soil water shortage is the key factor restricting ecological construction and development. Therefore, it is theoretical and practical significance to survey different site types soil water situation and its revegetation growth, research the relation between different site types soil water and revegetation growth, explore their balance mechanism, and put forward suitable plants about revegetation growth on different site types.This research area is ditch land on slopes around Hanjia plateau, Yaozhou district, Tongchuan. According to the slope aspect , slope position , slope degree and local actual situation, there are twelve site types in the sampling places, it is respectively sunward aspect 1, sunward aspect 2, half sunward aspect, half shady slope , each slope divides into the upper, middle and lower three slope position, each site type includes 2～3 standard places. The gathering sample place is a distance of 50cm from representative tree trunk bottom. There are two times sampling in one year, spring before rainy season and autumn after rainy season. The light manpower drill is used to gather sample, the average depth of drill is 500cm, the sampling distance is 10cm, and the determination of soil water moisture content is tested by drying weight method. Thirty representative trees that were chosen in the standard place were researched about tree height, diameter and volume and so on.Through the determination to rules of different site types 0～500cm soil water changes and revegetation growth, the results show that:(1) The soil moisture content was respectively on different site types: sunward aspect 1< sunward aspect 2 < half sunward aspect < half shady slope. The soil moisture content in autumn was lower than in spring. The annual rainfall amount and situation affected soil moisture content highly.(2) The slope aspect affected soil moisture content extremely remarkably. According to slope aspect, nine site types 0～500cm soil moisture content data in spring and autumn on sunward aspect 1, half sunward aspect and half shady slope were analyzed by one -way ANOVA, the conclusion was locust forest soil moisture content on different sunward aspect had the extremely remarkable difference, which showed that sunward aspect was the primary factor affected the soil moisture content in certain slope degree scope. The reason for soil moisture content difference on different slope aspect was the illumination radiation intensity difference was big, therefore the difference on transpiration intensity of plants and evapotranspiration intensity of soil moisture was big, which caused the soil moisture content difference was big.(3 ) The slope degree affected soil moisture content remarkably. According to slope degree, six site types at 0～500cm soil moisture content data in spring and autumn on sunward aspect land sunward aspect 2 were analyzed by one -way ANOVA, the result indicated that the different slope degree locust tree forest land soil moisture content difference was remarkable in spring, but after the arid year, the difference was not remarkable in autumn. This explained the different slope degree on the same slope aspect has certain influence to soil moisture content.(4) The slope position affected soil moisture content unremarkably. According to slope position, twelve site types at 0～500cm soil moisture content data in spring and autumn on sunward aspect 1, sunward aspect 2, half sunward aspect and half shady slope were analyzed by one -way ANOVA, the result indicated that the different slope position soil moisture content had no difference, which showed the same slope aspect different slope position affected soil moisture content unremarkably, the influence factors on slope position soil moisture content were complex.(5) The dry layer development level and depth are different on different site types. Three site types in spring on sunward aspect 1 appeared slight dry layer at 300～400cm , moderate dry layer at 400～500cm ; in autumn appeared slight dry layer at 100～400cm, moderate dry layer at 4 appeared 00～500cm . Three site types in spring on sunward aspect 2 appeared slight dry layer at 250cm, the upper slope position appeared moderate dry layer at 390cm, the lower slope position appeared at 450cm, the middle slope position didn't appear moderate dry layer. Autumn and spring had no big difference. Three site types in spring on half sunward aspect appeared slight dry layer and there wasn't moderate dry layer under 200cm. Three site types in spring on half shady slope appeared slight dry layer under 300cm on upper and middle slope position, dry layer didn't appear on lower slope position; the result was similar in autumn and spring.(6) The woods grew differently on different site types. Through the determination to tree height, diameter and volume, locust forest grew well on half sunward aspect and sunward aspect 2, but otherwise on half shady slope sunward aspect 1.The locust belongs to sciophytes, soil moisture content on half shady slope was high, so locust forest didn't grow well either, while the reason of sunward aspect 1 was soil moisture content was low.(7) The appropriate allocation was about tree species in research district. It was proved that locust forest grows well on sunward aspect 2 and half sunward aspect, but the density should be lowered; half shady slope was suitable for shade-demanding plant, while sunward aspect was goodfor shrubbery.