An ultrasonic humidification fluorescent tracing method for detecting unsaturated atmospheric water absorption by the aerial parts of desert plants

Atmospheric water absorption by plants has been explored for more than two centuries, and the aerial parts of plants, particularly the leaves of certain species, have been demonstrated to have an ability to absorb and utilize saturated atmospheric water such as fog, dew and condensed water. So far, however, there have been few studies on the aerial parts of desert plants in their absorption of unsaturated water from the atmosphere. This study presents an ultrasonic humidification fluorescent tracing method of detecting unsaturated atmospheric water absorption by the aerial parts of desert plants. We constructed an organic glass room based on the sizes of field plants. Then, the aboveground parts of the plants were humidified in the sealed glasshouse using an ultrasonic humidifier containing fluorescent reagents. The humidity and wetting time were controlled by turning on or off the humidifier according to the reading of a thermo-hygrometer suspended in the glasshouse. Fluorescence microscopy was employed to observe these plant samples. This method can generate unsaturated atmospheric water vapor and incorporate other fluorescent reagents or water-soluble chemical reagents for gasified humidification. In addition, it can identify plant parts that absorb unsaturated atmospheric water from the air, detect water absorption sites on the surface of leaves or tender stems, and determine the ability of tissues or microstructure of aerial parts to absorb water. This method provides a direct visual evidence for the inspection of leaf or tender stem microstructure in response to unsaturated atmospheric water absorption. Moreover, this method shows that aqueous pores in the cuticles of leaves or tender stems of desert plants are large enough to allow the passage of ionic fluorescent brightener with a molecular weight of up to 917 g/mol. Thus, this paper provides an important approach that explores the mechanism by which desert plants utilize unsaturated atmospheric water.

Effects of Different Gravel Mulched Years on Soil Microbial Flora and Physical and Chemical Properties in Gravelsand Mulched Fields

Soil microbial flora and influencing factors of soil microbes in soil and gravel-sand mixed layer( SGSML),roots denseness layer( RDL),eluviate layer( EL) and calcium accumulation layer( CAL) in gravel-sand mulched fields( GSMFs) with different gravel mulched years( 1,6,12,19 and 25 years) were studied. The results showed that in the composition of soil microbes in the GSMFs,the quantity of bacteria was the largest,followed by actinomycetes,while the number of fungi was the smallest. The total quantity of soil microorganisms in the GSMFs dropped rapidly with the increase of soil depth,which was related to the sudden decrease in the quantity of bacteria. The number of microbes in the RDL was larger than that in the SGSML with few roots due to the effects of root distribution. The number of bacteria and actinomycete in the growing season was larger than that in the non-growing season,while the quantity of fungi in the growing season was smaller than that in the non-growing season. The quantity of bacteria and fungi was the largest in the GSMFs which had been mulched with gravel for 6-12 years. With the increase of mulching time,the GSMFs aged gradually,so their quantity reduced gradually. The quantity of actinomycetes was the smallest in the GSMFs which had been mulched with gravel for 6-12 years and increased with the increase of mulching time. The number of soil microbes in the GSMFs had a good correlation with soil moisture content,p H and mulching time. Soil total carbon content was an important factor restricting the quantity of soil microbes in the GSMFs.

Isotopic evidence for the moisture origin and composition of surface runoff in the headwaters of the Heihe River basin

We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data and variations in the stable hydrogen and oxygen isotope ratios(δ D and δ 18O) of precipitation,spring,river,and melt water. The similar seasonality in precipitation δ 18O at different sites reveals the same moisture origin for water entering the headwaters of the Heihe River basin. The similarity in the seasonality of δ 18O and d-excess for precipitation at Yeniugou and Urumchi,which showed more positive δ 18O and lower d-excess values in summer and more negative δ 18O and higher d-excess values in winter,indicates a dominant effect of westerly air masses in summer and the integrated influence of westerly and polar air masses in winter. Higher d-excess values throughout the year for Yeniugou suggest that in arid inland areas of northwestern China,water is intensively recycled. Temporal changes in δ 18O,δ D,and d-excess reveal distinct contributions of different bodies of water to surface runoff. For example,there were similar trends for δ D,δ 18O,and d-excess of precipitation and river water from June to September,similar δ 18O trends for river and spring water from December to February,and similar trends for precipitation and runoff volumes. However,there were significant differences in δ 18O between melt water and river water in September. Our results show that the recharge of surface runoff by precipitation occurred mainly from June to mid-September,whereas the supply of surface runoff in winter was from base flow(as spring water) ,mostly with a lower runoff amount.