To explore the eco-physiological adaptation of Sabina vulgaris to drought stress,a drought-controlled experiment was performed using PEG(Polyethylene glycol) with three levels of osmotic potential(0.02,-0.1 and-0.34 MPa,respectively) in the culture solution in the greenhouse for 6 years(1997-2003).The seasonal changes of photosynthetic characteristics and pigment composition were investigated for the whole year in 2003.The pattern of seasonal change in stomatal conductance was shown in bimodal distribution with peaks in both May and September in 2003,and the stomatal conductance in the control was much higher than that of the other two water stress treatments,while the photosynthetic rate of low water stress was the highest among the three treatments.The ratio of chlorophyll a to chlorophyll b(Chl a/b) increased for all three treatments through November to March next year,particularly at the high water stress condition.The total leaf Chl content(Chl a+b) increased for all the three treatments through March to September,and the value was the lowest with the high water stress treatment.The total xanthophyll content(V+A+Z) and(A+Z)/(V+A+Z) were significantly higher in winter(November to March) than in summer(May to July) compared to that in other seasons,which was particularly obvious with high drought treatment.

In the Mu Us desert,China,dew condensation from soil surface to 1.5 cm in depth under Sabina vulgaris patch gap was measured by directly weighting method from May to October,2002.Daily and seasonal changes of dew condensation and the controlling factors on dew condensation were analyzed.The results indicated that the net dew deposition of the upper soil layer of S.vulgaris patch gap could be maintained from the late afternoon to the following morning in all seasons.Under natural conditions,the process of dew formation was composed of the following two stages:(1) The process of water molecular absorption of sandy soil could last for a long time,however,the amount of dew was limited.(2) The process of soil condensation determined by dew point temperature.Soil condensation lasted a relatively short period and generated considerable dew condensation in volume at the predawn and therefore accounting for the main part of dew condensation.Although dew occurred every month from May to October,the total amount and the time duration of dew condensation changed seasonally.In May,the condensation duration period was shorter and the net total amount was less than other seasons.In September,the condensation duration period was the longest and the largest amount of dew was produced.In Mu Us desert,dew condensation was influenced primarily by wind speed,air-soil surface temperature deficit,humidity and interactions among them.Wind speed showed a high correlation with dew condensation.Higher air-soil surface temperature deficit interacted with lower humidity in daytime promoted strong evaporation generating from soil surface and facilitated the incipience of water molecular absorption condensation at early time.Higher air-soil surface temperature deficit,however,interacted with certain humidity(50%～60%),the consequence was reverse.Query whether air temperature could trend or reach the dew-point temperature that soil condensation was produced is critical for the amount of dew condensation during night.