A Study On Dynamics Of Soil Evaporation In A Typical Sandy Shrub Community In The Mu Us Desert

In arid and semi-arid areas,water resources are the important factor of limiting plant survival and growth.Soil evaporation,the invalid loss of water,should be taken seriously.In this study,the soil evaporation of Artemisia ordosica community,Salix psammophila community and the mobile duneswere measured by micro-lysimeter in the growth season from 2012 to 2014.The environmental factors(soil temperature,soil water content,air humidity,meteorological factors and so on)were measured at the same time.Water surface evaporation and evapotranspiration were also analyzed.It's aimed to explore the regulation of soil evaporation and the major limiting factors to investigate the reasons for the change of soil evaporation after vegetationrestoration.The main results are as follows:(1)Soil evaporation in the study area showed a certain rule at different time scales.On the daily scale,the fluctuations of soil evaporation is noticeble,and the fluctuations are easier to see in A.ordosicacommunity and S.psammophila community thanthe mobile dunes.The average soil evaporation of A.ordosicacommunity,S.psammophila community andthe mobile dunes is 0.4mm,0.42mm,0.31 mm,respectively.On the seasonal scale,soil evaporation reaches the maximum between June and August and the minimum is observed during May and October.On the yearly scale,soil evaporation showed a significant increase in 2013,higher than those in 2012 and 2014.In additon,soil evaporation was the largestin the period of full leaf expansion,but theproportion of evapotranspiration was low.Soil evaporation account for evapotranspiration during the growing season from 2012 to 2014 are12.85%,21.29%and 19.49%,respectively.And the lowest proportion is found in July(12.58%),the highest in October(29.42%).(2)The effects on soil evaporation caused by meteorological and soil factors were different.Among the meteorological factors,wind speed and the humidity and temperature of air showed no significant effects on soil evaporation.However solar radiation had a correlation with soil evaporationand rainfall had dominant influence on soil evaporation.As for cases of the rainfall>5mm,the influence of rainfall on soil evaporation can last for 4 days;For the rainfall during 1mm to 5mm,the influence of rainfall can last for 2 days.Different rainfall patterns had a significant effect on soil evaporation.Rainfall events of high frequency and small rainfall can accelerate the process of soil evaporation.Soil evaporation of A.ordosica community,S.psammophila community and the mobile dunesaccount for rainfall during the growing season from 2012 to 2014 is24.19%,26.59%,18.26%,respectively.For soil factors,the effect of soil water content on soil evaporation decreased with increasing depth.There isn't significant influence on soil evaporation when the soil temperature was design as 10cm and 30cm.Otherwise,Water surface evaporation has significant relationship with soil evaporation during the wet period,and the soil evaporation of the mobile dunes hasbest fit with water surface evaporation.Soil moisture is the major factor limiting the soil evaporation in the study area.(3)Soil evaporation in vegetation community is remarkably higher than the soil evaporation in the mobile dunes especially during the wet period.The highest soil evaporation of vegetation community were about 210%higher than that in the mobile dunes in wet period.The main reason probably was the change of soil mechanical composition after vegetation restoration.The content of clay and silt particle in community is considerably higher than the mobile dunes and soil structure was improved to a certain extent.