Does hydraulic lift exist in shallow-rooted species? A quantitative examination with a half-shrub Gutierrezia sarothrae |
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Authors: | Changgui Wan Ronald E Sosebee Bobby L McMichael |
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Institution: | (1) Department of Range and Wildlife Management, Texas Tech University, 79409 Lubbock, TX, USA;(2) Cropping Systems Research Laboratory, USDA-ARS, Route 3, 79409 Lubbock, TX, USA;(3) Gansu Grassland Ecological Research Institute, Lanzhou, China |
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Abstract: | Hydraulic lift occurs in some deep-rooted shrub and herbaceous species. In this process, water taken up by deep roots from
the moist subsoil is delivered to the drier topsoil where it is later reabsorbed by shallow roots. However, little is known
about the existence of hydraulic lift in shallow-rooted xeric species. The objectives of this study were 1) to ascertain whether
hydraulic lift exists in Gutierrezia sarothrae (broom snakeweed), a widespread North American desert species with a shallow root system, grown in pot and field conditions
and 2) if it does, how much water can be transferred from the subsoil to the 30 cm topsoil during the night. Snakeweed seedlings
were transplanted in buried pots allowing the deeper roots to grow into the subsoil 30 cm below the surface. Soil water content
inside and outside of the pot was measured seasonally and diurnally with time domain reflectometry technique (TDR). An increase
in water content was detected in the pot after the plant was covered for 3 h by an opaque plastic bag during the day, suggesting
hydraulic lift from deeper depths and exudation of water into the drier topsoil. Root exudation was also observed on native
range sites dominated by snakeweed. Water efflux in the pot was 271 g per plant per night. which was equivalent to 15.3% of
the extrapolated, porometer-derived whole-plant daily transpiration. Hydraulic lift observed in Gutierrezia improved water uptake during the day when evaporative demand is high and less water is available in the topsoil. We concluded
that hydraulic lift might help snakeweed to alleviate the effect of water stress. |
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Keywords: | desert xerophyte root exudation semiarid grassland |
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