Soil Water Dynamics And Evapotranspiration Rule Of Vitex Nesundo In Xiaolangdi

The soil moisture dynamics and the evapotranspiration water consumption law of the Henan Xiaolangdi were studied with the method of large weighing lysimeter and the data of automatic meteorological station.The results of evapotranspiration are affected by wind.The large weighing type lysimeter plants the larger trees of the canopy,and the results of the evapotranspiration are influenced by the wind to produce errors,analyze the characteristics of the influence of the wind,and discuss the method of determining the daily evapotranspiration by the artificial windshield.According to the Penman formula,the possible evapotranspiration of the vegetation under the local meteorological conditions is calculated.According to the Penman formula,the possible evapotranspiration of the vegetation under the local meteorological conditions was calculated.The total evapotranspiration of the observed year was 1249.8mm,the rainfall in the observed period was 528.4mm,less than half of the possible evapotranspiration,and the root of the Vitex negundo had the soil water consumption in the deep soil.Different vegetation treatments were carried out on Vitex negundo and the results showed that there were differences in the growth status of Vitex negundo.The leaf area index and transpiration rate under different soil moisture were observed.It was found that the maximum leaf area index of Vitex negundo in summer was 4.46 and the maximum transpiration rate could be achieved.9.18 mmol/m2 ·s.The soil moisture is stratified in vertical section,which is divided into active layer of soil water(0~20cm),the soil moisture is sub active layer(20~40cm),and the soil moisture is relatively stable(60~80cm).Because of seasonal variation of precipitation and plant water use in growing season,soil moisture changes seasonally.In the late winter and early spring,soil moisture content is relatively high.In summer,plants are used,with high temperature and high evapotranspiration,and soil moisture is at the lowest level in late summer and early autumn.At the end of the autumn,soil moisture recovered.After a precipitation,the change rule of soil moisture first increased and then decreased.At last,it basically returned to the level of humidity before precipitationl.1~2days after precipitation,soil moisture decreased significantly,followed by a decreasing amplitude,while active layer(0~20cm)decreased soil moisture by more than 40 cm.10cm soil minimum effective precipitation is 5mm,20 cm soil effective rainfall is 10 mm.The diurnal variation of the evapotranspiration of Vitex negundo was measured by lysimeter.The diurnal variation of the evapotranspiration measured by a typical sunny day evaporative apparatus was single-peak with three different moisture treatments.The maximum daily evapotranspiration at different seasons was between 12:00 and 16:00.Due to the effects of plant transpiration and daytime temperature and illuminationt,evapotranspiration changes at night less than during the day.The evapotranspiration calculated by Lysimeter and the calculated evapotranspiration calculated by Penman formula were used to calculate the plant coefficient of shrub under different seasons.The vertical change of soil moisture has a daily humidity invariant layer,that is,in a day,the depth of soil moisture remains unchanged within a day.The evapotranspiration of active layers is calculated by the method of daily wet constant layer.The highest proportion of Evapotranspiration to the measured evapotranspiration is 50.8% in winter wet constant layer method and 25.4% in summer.There is a correlation between meteorological factors and evapotranspiration,and the daily and net radiation are positively related to the evapotranspiration,and the relative humidity and wind speed are negatively correlated with the evapotranspiration.