Abstract
Plant leaf surface moisture is a frequent meteorological phenomenon that has complicated sources. As such, the determination of whether surface moisture is the input water or only the redistribution of water in the soil–plant–atmosphere ecosystem is of great importance. In this study, δ18O and δD characteristic values of dew, guttation, and soil waters in Buxus sinica var. parvifolia M. Cheng were monitored during the frost-free period (June–September 2017) in Changchun, China, to differentiate the hydraulic relationship among atmospheric vapor, rainwater, soil, dew, and guttation waters and quantitatively distinguish the leaf surface moisture on the canopy and bottom of plants. The water vapor sources of the leaf surface moisture on plants’ canopy and bottom were quantitatively verified in accordance with isotope fractionation and mass conservation principles. Results demonstrated that leaf surface moisture, atmospheric vapor, soil water, and dew were closely related. Leaf surface moisture was mainly the condensation of dew. The sources of canopy and bottom leaf surface moisture were basically the same. The proportions of canopy moisture from plant guttation, atmospheric vapor, and soil water were 2.4%–2.5%, 79.8%–92.4%, and 5.1%–17.8%, respectively. By comparison, the proportions of bottom leaf surface moisture were 0.6%–1.4%, 80.0%–93.0%, and 6.4%–18.6%, respectively. Leaf surface moisture is an important water input in urban systems. Moreover, the characteristic values of stable hydrogen and oxygen isotopes of urban dew are supplemented, and the transformation of atmospheric vapor, rainwater, and soil and dew waters is revealed.
Highlights
The condensation of water on leaves is a common occurrence on urban plants in the morning.The sources of leaf surface moisture include dew and guttation [1]
In terms of canopy height, δ18 O and δD in leaf surface moisture and dew had r values of 0.98 and 0.99, respectively. δ18 O and δD in leaf surface moisture and atmospheric vapor had r values of 0.96 and 0.98, respectively. This result was similar to the soybean canopy in the USA [16]. These findings demonstrated that the four types of water had a close hydraulic relationship
This study monitored the dew condensation in an urban ecological system to quantitatively analyze the sources of plant dew vapor in urban ecosystems and reveal the near-surface water vapor cycle
Summary
The condensation of water on leaves is a common occurrence on urban plants in the morning. The sources of leaf surface moisture include dew and guttation [1]. Dew condensation is a normal weather phenomenon that can replenish the available moisture of plants and soil [2]. Two main water sources are involved in dew formation. First is water vapor in the lower atmosphere (dewfall), which is the dominant source, and the other is water vapor that originates from flooded soil (dewrise) [5]. Guttation is the secretion of water and dissolved materials from the pores of plants, mainly at night. Dewfall is a kind of pure water input for plants, whereas dewrise (distillation) is only a part of soil, plant, and atmosphere system water redistribution
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