The Variations Of The Soil Temperature And Moisture And Its Relationship With Dynamics Of Vegetation Cover In Qaidam Basin

The process of land Underlying is one of the important factors that causes climate change, atmospheric motion and circulation characteristics will be affected by the underlying surface water and heat.As a part of the underlying surface climate system, soil is an energy regulator of the weather changes, and its energy storage and release will have a significant impact on long-term weather change. The Qaidam Basin is located in the northeast edge of the Qinghai Tibet Plateau, and it is a typical inland arid plateau basin.In recent years, the temperature and rainfall in Qaidam Basin rises obviously. The ecological environment of soil desertification changes obviously. Vegetation growth condition is also affected by the changes in climate and soil, which cause changes in the local ecological environment.Understanding the variation characteristics of soil temperature and humidity and the relationship between them have a great significance on the research of ecological construction, ecological balance, environmental protection and sustainable development.Through the data analysis of soil temperature from July 2010 to June 2011, we can conclude the spatial and temporal variations of soil temperature in the four sampling sites (Golmud, Nuomuhong, Delingha and Da Qaidam) of Qaidam Basin, and come to the preliminary discussion on the reasons for such changes. By using, the method of mathematical statistics, correlation, we analysis the relationship between the temperature and humidity of soil, climate and vegetation cover change.Four sampling sites have similarity in daily variation of soil temperature. The temperature of shallow soil (10cm,30cm) changes dramatically every day, and the daily temperature variation of deep soil (50cm,70cm and 90cm) is relatively stable; The soil temperature of four sites in observation years shows approximate like a sine curve, which reaches the highest in August and the lowest in January. In February and March the temperature in different depth of soil is basically the same. The depth of the soil there is almost no energy flow.Soil moisture of three sampling points changed obviously. Analysis from the vertical direction, the 10cm soil temperature changes can be divided into two stages:heat accumulation and heat release. Soil moisture has significant effects on soil temperature change, and there is a significant correlation between them. The perspective of seasonal soil moisture change is periodicity and similarly. But each sampling site has their own relative specialty. The amplitude of soil moisture is not the same:Da Qaidam> Delingha> Nuomuhong, and extremum appearance time is different. Four sample point of seasonal change of soil moisture in wet season is affected by precipitation, in the dry season is strongly influenced by soil temperature.There is a significant correlation between soil temperature and soil moisture. Quadratic function relation between temperature and humidity of the soil depth in the Nomuhong sample. Delingha and Da Qaidam two sampling points in shallow layer soil (10cm and 30cm and 50cm) temperature and humidity similarto Nomuhong, a quadratic function changes. The deep soil (70cm and 90cm) linearly related to temperature and humidity.Four sampling points in June 2010 the overall trend of five days, from 21 to 30 September the average NDVI change agreement, five average NDVI values fluctuate between 0.06-0.35, five days each point average NDVI values are in the mid to late August the highest value. However, changes in five days on average NDVI value four sampling points and a regional particularity.The average NDVI values of the four sample points for five days and a positive correlation between soil temperature, soil depth deeper, the more obvious this relationship, the effect of soil temperature on vegetation indices stronger. The average NDVI of five days was closely related to soil moisture, however, there was no significant correlation with temperature and precipitation, it could not deny the effect of air temperature and precipitation on vegetation growth. This phenomenon may be caused by the short time scale, the statistical data is limited, the influence of the hysteresis and the meteorological data and the sampling point is not complete correspondence and so on.