Formation Mechanism Of Condensation Water And It's Effects On The Moisture Characteristics Of Plant In Semi-arid Area

Condensation water is important water source in semiarid Ecosystems. We used homemade micro-lysimeter, detached shoots, artificial condensation surface, pressure chamber and plants of drought stress to determined characteristics of soil condensation water, characteristics of canopy condensation water, and condensation water's effect on water characteristics of Sabina vulgaris, Artemisia ordosica and Artemisia sphaerocephala from 2007 to 2009 at the test base of Grassland Experimental Station of Science and Technology Park of Inner Mongolia Agriculture University and Mu Us Sandland Development and Research Center. The results showed as follows:1. There were three kinds of water vapor source, water vapor of direct adsorption by soil from air, condensation water from air and water vapor from the lower soil layer about condensation water of soil in Semi-arid areas; Condensation water of soil is mainly occurred at 0~2cm and 2~4cm of soil surface,there was linear positive correlation between condensation volume of 0~2cm, 2~4cm and condensation volume of 0~10cm.The contribution rate of water vapor from air was smaller than from lower soil layer to upper 5cm soil condensation water, their contribution ratios usually were from 3.1:10 to 4.5:10.When condensation volume of soil surface reduced , the contribution rate of water vapor from air would increased and the contribution rate of lower soil layer would reduced , their maximum contribution ratio was 8:10 in the dry season. Water vapor from air always condensated and evaporated earlier than water vapor from lower soil layer at upper 5cm soil layer.2. Soil condensation water would change with the seasons, condensation volume and evaporation volume of soil condensation water was higher in the rainy season than in the dry season,a strong and significant linear positive correlation was found between today's condensation volume(x) and next day's evaporation volume(y), their equation was y=0.947x+0.0103(R2=0.9454,n=348,P<0.05). There was linear positive correlation between initial soil water content and increasing of soil surface moisture,their equation was y=-0.2618x+0.7192(R2=0.5609,n=51,P<0.0001). If soil contained more and more small particle sand and physical clay, which would help the formation of condensation water of soil, condensation ability of the soil from big to small was undisturbed soil of Sabina vulgaris's plot, undisturbed soil of Artemisia ordosica's plot, undisturbed soil of bare land's plot, and aeolian sandy soil.3. Where there were more plant-covered will help the formation of condensation water of soil. In Mu Us Sandland, condensation ability of the canopy from big to small was Sabina vulgaris, Artemisia ordosica and bare land. Duration ability of 100% relative humidity from big to small were 100cm, 50cm,150cm and 5cm in the vertical height of Sabina vulgaris canopy. There were no significant difference between the ability of intercepting condensation water of artificial condensation surface and detached shoots'of Sabina vulgaris, the intercepting volumes of condensation water by artificial condensation surface and detached shoots of Sabina vulgaris were linear positive correlation with condensation water's duration. PVC condensation plate of Sabina vulgaris canopy were able to intercept condensation water from May to September in 2009, the biggest rainy season's intercepting volume was 0.0994mm and the biggest dry season's intercepting volume was 0.0086mm. Condensation volume of Sabina vulgaris canopy was significantly correlated with condensation volume of soil.4. Relative humidity was the main meteorological factor that will effect the formation of soil condensation water in rainy season, and absolute humidity was the main meteorological factor that will effect the formation of soil condensation water in dry season. Condensation volume of PVC condensation plate was significantly positive correlated with 24h average relative humidity and 12h average relative humidity of night, and was significantly negatively correlated with 24h average temperature and 12h average temperature of night.5. Condensation water'effects on the moisture characteristics of Sabina vulgaris,Artemisia ordosica and Artemisia sphaerocephala were significant, it could keep and enhance water potential and relative water content of shoots. After spraying fog and sealing bag indoors, the average water potential increment of Sabina vulgaris,Artemisia ordosica and Artemisia sphaerocephala were 0.0454~0.1646MPa/12h, 0.1725~0.3466MPa/12h and 0.6553~0.7792MPa/12h, respectively; the average increment of relative water content of were 0.92%~ 3.01%/12h, 2.47%~4.68%/12h and 1.57%~4.95%/12h, respectively.