Contrasting patterns of hydraulic redistribution in three desert phreatophytes

Abstract

We measured sap flow in taproots, lateral roots and stems within a single individual in each of three co-occurring tree species in a Chihuahuan desert arroyo to assess the seasonality and magnitude of hydraulic redistribution. Nocturnal reverse flow (hydraulic redistribution) was detected in shallow lateral roots of Fraxinus velutina and Juglans major during periods when surface soils were dry. Reverse flow in the Fraxinus lateral root ranged from near zero to 120 g h(-1), and was inversely correlated with nighttime vapor pressure deficit (D), suggesting that nighttime transpiration may have inhibited hydraulic redistribution. Reverse flow in the Juglans lateral root ranged from near zero to 18 g h(-1). There was no relationship between reverse flow and nighttime D in the Juglans lateral root, despite a weak positive relationship between nighttime D and rates of basipetal flow (flow towards the stem) in the taproot. Reverse flow in Fraxinus and Juglans ceased when surface soils were wetted by monsoon rains and flooding. We found no reverse flow or seasonal variation in root sap flow in Celtis reticulata. However, basipetal sap flow in Celtis roots continued throughout most of the evening, even during periods when D was near zero, and commenced in the morning more than two hours after the onset of sap flow in the main stem. Patterns of nocturnal root sap flow in Celtis may have been facilitated by the diurnal withdrawal from, and refilling of above ground storage compartments (i.e. above ground diurnal storage capacity), which may have prevented hydraulic redistribution. Species differences in nocturnal root function may have significant impacts on ecosystem hydrological fluxes, and should be considered when scaling fluxes to catchment, landscape, and regional levels.

Hydraulic Redistribution from Wet to Drying Roots of Potatoes (Solanum tubersosum L.) During Partial Rootzone Drying

“…Thus, the 'drying roots' were probably being rehydrated both from above-ground plant parts due to hydraulic redistribution and from deeper moist soil layers due to hydraulic lift, thereby neutralising the deuterium concentration to some extent. Hultine et al [41] found that the magnitude of hydraulic redistribution was greater in roots when night-time vapour pressure deficit was low.…”

“…Scholz et al [14] found that the rate of reverse flow was linearly related to soil-leaf water potential gradient, with the greatest reverse flow rates occurring when this potential gradient was at its most negative values. Hultine et al [15] reported greater magnitude of hydraulic redistribution in roots when night-time vapour pressure deficit was low. The onset and the magnitude of hydraulic redistribution is thought to be regulated by the development of water potential gradients within the plant parts, between the plant parts and soil, and the nocturnal demand for water by the plant [16].…”

Modelación matemática de la interacción entre la vegetación de ribera y el régimen hídrico del río en condiciones semiáridas

“…Se procedió a la adaptación de la propuesta de la Ecuación 6.20 con base en el modelo conceptual de RibAV: para la modelación a escala diaria se asumió un valor 1 para S time desde la consideración de que "HLw" es un fenómeno que usualmente ocurre de noche (Amenu y Kumar, 2008;Caldwell y Richards, 1989;Caldwell et al, 1998;Dawson, 1993;Hultine et al, 2003); se tomó como parámetro de ecuación la duración de 10 horas al día que se ha reportado (Ryel et al, 2002).…”

“…En este sentido es de resaltar que el "HLw" simulado para la época seca es mayor que el correspondiente a la época de lluvias, lo que se explica en función de la demanda evaporativa en mención y de los potenciales mátricos del suelo característicos de períodos con ausencia de lluvia: en total, las tasas de ascenso hidráulico radicular simuladas con RibAV están entre 0.83 y 1.02 mm/día para RA y 0.69 y 1.29 mm/día para RF, durante el período de simulación de 2922 días. Estas cantidades se encuentran dentro del rango preliminar que citan algunos autores (Hultine et al, 2003;Ryel et al, 2002), aunque aún se están perfeccionando los métodos de estimación de este movimiento de agua.…”

“…Se han hecho importantes avances para demostrar la relevancia del ascenso hidráulico radicular y de la redistribución hidráulica de agua en el suelo, para la disponibilidad de agua de las plantas (Caldwell y Richards, 1989; Caldwell et al, 1998; Dawson, 1993 Dawson, y 1996Hultine et al, 2003;Ryel et al, 2002 Ryel et al, y 2003 Zheng y Wang, 2007). Recientemente se ha consolidado la necesidad de modelar la redistribución del agua del suelo propiciada por la conectividad del sistema radicular con zonas más húmedas del perfil, a través de la realización de los primeros valiosos esquemas de modelación físicamente basados (Amenu y Kumar, 2008; Lee et al, 2005;Ryel et al, 2002; Zheng y Wang, 2007;).…”