Seasonal and diurnal patterns of soil water potential in the rhizosphere of blue oaks: evidence for hydraulic lift

Ishikawa, Chie; Bledsoe, Caroline S.

doi:10.1007/s004420000470

Cited by 101 publications

(85 citation statements)

References 24 publications

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“…1). Other studies have found that HR begins when soil water potentials reach about −0.4 to −0.7 MPa (Caldwell & Richards 1989;Dawson 1993a;Millikin et al 2000). In a related Daily water use/ water storage (%) study using data from the probes with maximum HR activity, Meinzer et al (2004) found a threshold for HR of − 0.4 MPa for this stand and five others including three Brazilian cerrado stands, and old-growth Douglas-fir and ponderosa pine stands.…”

Section: Discussionmentioning

confidence: 61%

Hydraulic redistribution in a Douglas‐fir forest: lessons from system manipulations

Brooks

Meinzer

Warren

et al. 2005

Plant Cell & Environment

132

134

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Hydraulic redistribution (HR) occurs in many ecosystems; however, key questions remain about its consequences at the ecosystem level. The objectives of the present study were to quantify seasonal variation in HR and its driving force, and to manipulate the soil-root system to elucidate physiological components controlling HR and utilization of redistributed water. In the upper soil layer of a young Douglas-fir forest, HR was negligible in early summer, but increased to 0.17 mm day − − − − 1 (20-60 cm layer) by late August when soil water potential was approximately − − − − 1 MPa. When maximum HR rates were observed, redistributed water replenished approximately 40% of the water depleted from the upper soil on a daily basis. Manipulations to the soil or to the soil/plant water potential driving force altered the rate of observed HR indicating that the rate of HR is controlled by a complex interplay between competing soil and plant water potential gradients and pathway resistances. Separating roots from the transpiring tree resulted in increased HR, and sap flow measurements on connected and disconnected roots showed reversal of water flow, a prerequisite for HR. Irrigating a small plot with deuterated water demonstrated that redistributed water was taken up by small understorey plants as far as 5 m from the watering source, and potentially further, but the utilization pattern was patchy. HR in the upper soil layers near the watering plot was twice that of the control HR. This increase in HR also increased the amount of water utilized by plants from the upper soil. These results indicate that the seasonal timing and magnitude of HR was strongly governed by the development of water potential differences within the soil, and the competing demand for water by the above ground portion of the tree.

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Section: Discussionmentioning

confidence: 61%

Hydraulic redistribution in a Douglas‐fir forest: lessons from system manipulations

Brooks

Meinzer

Warren

et al. 2005

Plant Cell & Environment

132

134

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“…Blue oak trees possess a ring-porous xylem anatomy and are among the most xerophytic of associated oak species, as noted by their ability to achieve pre-dawn water potentials below −4.0 MPa (Griffin, 1973;Johannes et al, 1994;Ishikawa and Bledsoe, 2000;Kiang, 2002;Xu and Baldocchi, 2003).…”

Section: Vegetation Structure and Dynamicsmentioning

confidence: 99%

“…For the oak woodland, we deduced β using data from Ishikawa and Bledsoe (2000). They reported that 70% of excavated root biomass of a blue oak woodland is located, on average, above 0.5 m, which produces a β value of 0.976.…”

Section: Meteorological and Soil Measurementsmentioning

confidence: 99%

“…To survive across the hot dry summer in Mediterranean climates, many grass species adopt an annual life cycle and transmit their genetic information in the form of seed. Trees, growing adjacent to (or over) grasses, tap deeper sources of soil water (Lewis and Burgy, 1964;Griffin, 1973;Ehleringer and Dawson, 1992;Sternberg et al, 1996) or they can remedy soil moisture deficits through hydraulic lift (Ishikawa and Bledsoe, 2000). They also have the physiological capacity to withstand severe soil water deficits (Griffin, 1988).…”

Section: Introductionmentioning

confidence: 99%

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How plant functional-type, weather, seasonal drought, and soil physical properties alter water and energy fluxes of an oak–grass savanna and an annual grassland

Baldocchi

Kiang

2004

Agricultural and Forest Meteorology

531

415

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Savannas and open grasslands often co-exist in semi-arid regions. Questions that remain unanswered and are of interest to biometeorologists include: how do these contrasting landscapes affect the exchanges of energy on seasonal and annual time scales; and, do biophysical constraints imposed by water supply and water demand affect whether the land is occupied by open grasslands or savanna? To address these questions, and others, we examine how a number of abiotic, biotic and edaphic factors modulate water and energy flux densities over an oak-grass savanna and an annual grassland that coexist in the same climate but on soils with different hydraulic properties.The net radiation balance was greater over the oak woodland than the grassland, despite the fact that both canopies received similar sums of incoming short and long wave radiation. The lower albedo and lower radiative surface temperature of the transpiring woodland caused it to intercept and retain more long and shortwave energy over the course of the year, and particularly during the summer dry period.The partitioning of available energy into sensible and latent heat exchanged over the two canopies differed markedly. The annual sum of sensible heat exchange over the woodland was 40% greater than that over the grassland (2.05 GJ m −2 per year versus 1.46 GJ m −2 per year). With regards to evaporation, the oak woodland evaporated about 380 mm of water per year and the grassland evaporated about 300 mm per year. Differences in available energy, canopy roughness, the timing of physiological functioning, water holding capacity of the soil and rooting depth of the vegetation explained the observed differences in sensible and latent heat exchange of the contrasting vegetation surfaces.The response of canopy evaporation to diminishing soil moisture was quantified by comparing normalized evaporation rates (in terms of equilibrium evaporation) with soil water potential and volumetric water content measurements. When soil moisture was ample normalized values of latent heat flux density were greater for the grassland (1.1-1.2) than for the oak savanna (0.7-0.8) and independent of moisture content. Normalized rates of evaporation over the grassland declined as volumetric water content dropped below 0.15 m 3 m −3 , which corresponded with a soil water potential of −1.5 MPa. The grassland senesced and quit transpiring when the volumetric water content of the soil dropped below −2.0 MPa. The oak trees, on the other hand, were able to transpire, albeit at low rates, under very dry soil conditions (soil water potentials below −4.0 MPa). The trees were able to endure such low water potentials and maintain basal levels of metabolism because * Corresponding author. Baldocchi et al. / Agricultural and Forest Meteorology 123 (2004) ecological forcings kept the tree density and leaf area index of the woodland low, physiological factors forced the stomata to close progressively and the trees were able to tap deeper water sources (below 0.6 m) than the grasses.

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“…Previous studies indicated that SWP varies across plant growing season induced by the changes in plants requirements in water and minerals (Joslin, Henderson 1987;Ishikawa, Bledsoe 2000). In an arid desert region, SWP increases along growing season in shallow soil layers, whereas decreases in deep soil layers (Yang, Lü 2011;Hao et al 2013).…”

mentioning

confidence: 98%

Soil water potential determines the presence of hydraulic lift of Populus euphratica Olivier across growing seasons in an arid desert region

Fei¹,

Xu²,

Yang³

et al. 2018

J. For. Sci.

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Wang F., Xu Y., Yang X., Liu Y., Lv G.H., Yang S. (2018): Soil water potential determines the presence of hydraulic lift of Populus euphratica Olivier across growing seasons in an arid desert region. J. For. Sci., 64: 319-329.Hydraulic lift (HL) of deep-rooted plants is a water adaptation phenomenon to extreme drought conditions which would subsequently improve the survival of shallow-rooted plants in an arid desert area. There is an ongoing debate on whether the difference in water potential between plant roots and soils determine the presence of HL, thus considerable research efforts are needed to improve our understanding. In this study, we used the Ryel model and comparative analysis to determine the changes in soil water potential (SWP), the soil layer of obtaining water from plant roots (SLOW), the amount water released from plant roots into soils, and the total amount of release water of HL (H T ) of five stratified soil layers at different depths (i.e. 0-10, 10-40, 40-70, 70-100 and 100-150 cm) across plant growing season (i.e. June, August and October). The results showed that SLOW always appeared in the lowest SWP soil layer, and that lowest SWP differed among soil layers. The lowest SWP soil layer and SLOW shifted from shallow to deep soil layers across the growing seasons. Additionally, H T decreased across the growing seasons. Fine root biomass decreased in shallow whereas increased in deep soil layers across growing seasons. Our results proved the water potential difference among soil layers determined the presence of HL in an arid desert region. The changes in water potential difference among soil layers might shift the lowest SWP soil layer from shallow to deep soil layers, and as a consequent decrease H T across plant growing seasons.

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Seasonal and diurnal patterns of soil water potential in the rhizosphere of blue oaks: evidence for hydraulic lift

Cited by 101 publications

References 24 publications

Hydraulic redistribution in a Douglas‐fir forest: lessons from system manipulations

Hydraulic redistribution in a Douglas‐fir forest: lessons from system manipulations

How plant functional-type, weather, seasonal drought, and soil physical properties alter water and energy fluxes of an oak–grass savanna and an annual grassland

Soil water potential determines the presence of hydraulic lift of Populus euphratica Olivier across growing seasons in an arid desert region

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