Needle water potential and soil-to-foliage flow resistance during soil drying: a comparison of Douglas-fir, western hemlock, and mountain hemlock

1985 ◽  
Vol 15 (1) ◽  
pp. 185-188 ◽  
Author(s):  
T. M. Ballard ◽  
M. G. Dosskey
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Flow ◽  
Flow Resistance ◽  
Soil Water Potential ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Soil Drying ◽  
Experimental Conditions ◽  
Needle Water Potential

Needle water potential in western and mountain hemlock falls as the soil dries, but under our experimental conditions, it remained stable in Douglas-fir. Resistance to water flow from soil to foliage is higher for the hemlocks and increases more steeply as the soil dries. These findings physically account for the observation that water uptake is reduced relatively more for the hemlocks than for Douglas-fir, as soil water potential declines.

Soil water matric potential rather than water content determines drought responses in field-grown lupin (Lupinus angustifolius)

1998 ◽  
Vol 25 (3) ◽  
pp. 353 ◽  
Author(s):  
C.R. Jensen ◽  
V.O. Mogensen ◽  
H.-H. Poulsen ◽  
I.E. Henson ◽  
S. Aagot ◽  
...  
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Root Surface ◽  
Lupinus Angustifolius ◽  
Soil Drying ◽  
Matric Potential ◽  
Aba Content

Drought responses in leaves of lupin (Lupinus angustifolius L., cv. Polonez) were investigated in plants grown in lysimeters either in a sand or in a loam soil in the field. Abscisic acid (ABA) content, water potential (ψl) and conductance to water vapour (gH2O) were determined in leaves of both irrigated plants and in plants exposed to gradual soil drying. Amorning-peak of leaf ABA content was found in both fully watered and droughted plants. During soil drying which, on both soils types, only decreased soil water potential of the upper soil layers, mid-day leaf ABA content increased relative to that in fully irrigated plants before any appreciable decreases occurred in ψl. In the part of the soil profile from which water was taken up (0–60 cm depth), gH2O decreased when the relative available soil water content (RASW) on sand was below 12% and RASW on loam, below 30%. At this point the average soil water matric potential (ψsoil) on sand was less than –0.13 MPa and the fraction of roots in ‘wet’ soil was 0.12, while on loam, the fraction of roots in ‘wet’ soil was 0.44 while y soil was similar to that on sand. A critical leaf ABA content of 300–400 ng/g FW was associated with the onset of stomatal closure on both soil types. We suggest that the initial stomatal closure is controlled by ABA which originates from the roots where its production is closely related to ψsoiland the water potential of the root surface and that ψsoil is a more important parameter than RASW or the fraction of roots in ‘wet’ soil for affecting leaf gas exchange. Further drying on both soils led to further increases in leaf ABA and declines in ψl and gH2O. In order to gain further insight, experiments should be designed which combine signalling studies with simulation studies, which take account of soil water potential, root contact area and water flux when calculating the water status at the root surface in the soil-plant-atmosphere-continuum.

Soil water dynamics in forested and irrigated sites in Cyprus 

2021 ◽  
Author(s):  
Marinos Eliades ◽  
Adriana Bruggeman ◽  
Hakan Djuma ◽  
Melpomeni Siakou ◽  
Panagiota Venetsanou ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Potential ◽  
Soil Water ◽  
Water Flow ◽  
Water Retention ◽  
Soil Depth ◽  
Soil Water Potential ◽  
Water Dynamics ◽  
Annual Rainfall ◽  
Irrigation Amount

<p>The water storage in soil is a dynamic process that changes with soil, vegetation and climate properties. Water retention curves, that describe the relationship between the soil water content (θ) and the soil water potential (ψ), are used to model soil water flow and root water uptake by the plants. The overall objective of this study is to derive the retention curves of soils at two forested (Agia Marina, Platania) and two irrigated (Galata, Strakka) sites in Cyprus from in-situ soil moisture and soil water potential observations. <br>The long-term (1980 – 2010) average annual rainfall at Strakka olive grove (255 m elevation), Agia Marina P. brutia forest (640 m), Galata peach orchard (784 m) and Platania P. brutia forest (1160 m) is 298, 425, 502 and 839 mm, respectively.  The average soil depth at Agia Marina is 14 cm, while at other sites it is around 1 m. We installed a total of 18 TEROS21 soil water potential sensors, 37 5TM and 19 SMT100 soil moisture sensors, at different soil depths at the four sites. <br>Results from January 2019 to January 2021 show differences in the water retention curves of the four sites due to different soil textures. At the forested sites, θ reached wilting point at the summer period, indicating that trees extend their roots beyond the soil profile, to the bedrock in order to survive. At the irrigated sites, θ exceeds field capacity during irrigation, indicating over-irrigation. We found different water retention relations after rainfall and after irrigation, indicating that irrigation has an uneven spatial distribution. These findings suggest that the irrigation in these fields is not optimal and farmers may need to increase the number of irrigation drippers, while reducing the irrigation amount per dripper. From a monitoring perspective, increasing the number of sensors may give a better representation of the soil moisture conditions. <br>The research has received financial support from the ERANETMED3 program, as part of the ISOMED project (Environmental Isotope Techniques for Water Flow Accounting), funded through the Cyprus Research and Innovation Foundation.</p>

A modelling framework to predict transpiration reductions during drought based on soil hydraulics 

2021 ◽  
Author(s):  
Andrea Carminati ◽  
Mathieu Javaux
Keyword(s):  
Hydraulic Conductivity ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Soil Drying ◽  
Soil Hydraulic Conductivity ◽  
Plant Hydraulics ◽  
Soil Hydraulic

<p>There is increasing need for mechanistic and predictive models of transpiration and stomatal response to drought. Global measurements of transpiration showed that the decrease in soil moisture is a primary constrain on transpiration. Additionally, a recent meta-analysis indicated that stomatal closure is explained by the loss in soil hydraulic conductivity, more than that of the xylem. Despite these evidences on the role of soil drying as a key driver of transpiration reduction, the mechanisms by which soil drying impacts transpiration, including the effect of different soil hydraulic properties, are not fully understood.</p><p>Here, we propose that stomata regulate transpiration in such a way that the relation between transpiration and the difference in water potential between soil and leaves remains linear during soil drying and increasing vapor pressure deficit (VPD). The onset of hydraulic nonlinearity sets the maximum stomatal conductance at a given soil water potential and VPD. The resulting trajectory of the stomatal conductance for varying soil water potentials and VPD depends on soil and plant hydraulics, with the soil hydraulic conductivity and root length being the most sensitive parameters.</p><p>From this hydraulic framework it follows that stomatal closure is not simply a function of soil moisture, soil water potential or leaf water potential. Instead, it depends on transpiration demand and soil-plant hydraulics in a predictable way. The proposed concept allows to predict transpiration reductions during drought with a limited number of parameters: transpiration demand, plant hydraulic conductivity, soil hydraulic conductivity and active root length. In conclusion, this framework highlights the role of the soil hydraulic conductivity as primary constrain on transpiration, and thus on stomatal conductance and photosynthesis.</p>

Effects of disrupting stem sapwood water conduction on the water status in Douglas-fir crowns

1985 ◽  
Vol 15 (5) ◽  
pp. 982-985 ◽  
Author(s):  
H. Brix ◽  
A. K. Mitchell
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Leaf Water Potential ◽  
Water Status ◽  
Soil Water Potential ◽  
Douglas Fir ◽  
Leaf Water ◽  
Cross Sectional ◽  
Breast Height ◽  
Water Conduction

The sapwood cross-sectional area at breast height was reduced by 0 (control), 42, 69, and 100%, in 36-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees to study treatment effects on the water status in the crowns. Only the complete removal of breast-height sapwood affected the leaf water potential which decreased rapidly the 1st day, but then changed little for the next 38 days varying only from −2.3 to −2.6 MPa. Water use for those trees was limited to that stored above breast height, primarily in stem sapwood, and amounted to approximately 45 L. This corresponded to 6.5 mm of precipitation or 4% of potential transpiration. The finding that leaf water potential was not affected by partial sapwood reduction but rather by changes in soil water potential suggests that resistance to water flow in stems was small compared with that in other parts of the water-flow pathways of soil and trees.

Thinning and nitrogen fertilization effects on soil and tree water stress in a Douglas-fir stand

1986 ◽  
Vol 16 (6) ◽  
pp. 1334-1338 ◽  
Author(s):  
H. Brix ◽  
A. K. Mitchell
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Nitrogen Fertilization ◽  
Soil Water Potential ◽  
Early Morning ◽  
Douglas Fir ◽  
Fertilization Effect ◽  
Use Efficiency ◽  
Soil Water Conditions ◽  
Fertilization Effects

Soil and tree water potentials were studied over a 10-year period in a Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand that was treated when 24 years old with different thinning and nitrogen fertilization regimes. Throughout the 10-year period, thinning increased the soil water potential during the dry summer periods (July–September) by as much as 1 MPa both with and without fertilization. Fertilization effect on soil water potential was slight and only apparent in the latter part of the study in spite of large increases in leaf area (50% after 7 years) possibly because of better stomatal control of water loss. Fertilization increased water use efficiency. The favorable soil water conditions produced by thinning led to improved shoot water potential only during predawn and early morning. Removal of understory in a thinned and fertilized plot did not affect soil or shoot water potential.

scholarly journals Effects of wood ash and soil water potential on vegetative development of mung bean (Vigna radiata L.)

2021 ◽  
pp. 354-361
Author(s):  
Luana Glaup Araujo Dourado ◽  
Edna Maria Bonfim- Silva ◽  
Tonny José Araújo da Silva ◽  
Everton Alves Rodrigues Pinheiro ◽  
William Fenner
Keyword(s):  
Plant Growth ◽  
Water Potential ◽  
Soil Water ◽  
Vigna Radiata ◽  
Mung Bean ◽  
Soil Water Potential ◽  
Wood Ash ◽  
Soil Conditions ◽  
Experimental Conditions ◽  
Mato Grosso

This research aimed to evaluate the amending potential of eucalyptus’s wood ash on soil chemical properties and soil-water potential. The experiment was conducted in a greenhouse at the Federal University of Mato Grosso, campus in Rondonópolis. The experimental design was composed of randomized blocks in a 5x5 factorial scheme, including five soil-water potentials (‒4, ‒8, ‒16, ‒32 and ‒64 kPa), and five wood ash doses (0; 8; 16; 24 and 32 g dm-3). The soil samples were collected from the top layer of an Oxisol under natural Cerrado vegetation. Mung bean (Vigna radiata L.) growth variables (plant height, numbers of leaves, stem diameter, and SPAD index) were analyzed at three different phenological periods. In general, the wood ash doses increased soil pH, eliminated the exchangeable aluminum, and improved soil essential nutrients availability. As a result, mung bean plants responded positively to wood ash, achieving superior results at doses ranging from 24 to 26 g dm-3. The interaction between wood ash doses and soil water potential was not significant. However, drier soil conditions constrained plant growth severely. According to our experimental conditions, plant growth variables achieved higher performance at soil water potential of -4 kPa

Effects of salal understory removal on photosynthetic rate and stomatal conductance of young Douglas-fir trees

1986 ◽  
Vol 16 (1) ◽  
pp. 90-97 ◽  
Author(s):  
D. T. Price ◽  
T. A. Black ◽  
F. M. Kelliher
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Vapour Pressure Deficit ◽  
Basal Area ◽  
Douglas Fir ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Data Set

The effects of salal (Gaultheriashallon Pursh.) understory removal on the growth of thinned 32-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees were determined in a stand subject to growing season soil water deficits. Four pairs of similar trees were selected and the understory was completely removed from around one of each pair, the root zones of which were both isolated using plastic sheeting buried to bedrock. Photosynthesis, stomatal conductance, soil water potential and canopy microclimate were measured intensively in one pair on 4 clear days during an extended dry period in June 1982. Basal area increment of the four pairs of trees was measured over three growing seasons. To determine the effect of soil water potential on tree photosynthesis, the same variables were intensively measured over 3 consecutive days in late August 1982 for another tree initially subjected to a soil water potential of approximately −1.6 MPa, but irrigated to approximately −0.02 MPa between the 1st and 2nd days. Solar irradiance decreased markedly between the 2nd and 3rd days, thereby creating a unique data set. Findings were as follows: (i) removal of understory significantly increased rates of photosynthesis in the trees, both diurnally and seasonally, (ii) photosynthesis was not generally limited by stomatal conductance unless vapour pressure deficit was high and photon flux density was saturating, and (iii) tree growth response to salal removal was due to higher soil water potential, which increased both photosynthetic capacity and stomatal conductance.

scholarly journals SIMULATION OF TRANSPIRATION OF CITRUS GOVERNED BY LEAF CONDUCTANCE

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 609d-609
Author(s):  
Leon H. Allen ◽  
Mary P. Brakke ◽  
James W. Jones
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Water Flow ◽  
Root Length Density ◽  
Soil Water Potential ◽  
Small Time ◽  
Vapor Concentration ◽  
Time Step ◽  
Concentration Difference

A water flow model was developed which uses irradiance, leaf-to-air vapor concentration difference, and soil water potential to establish stomatal conductance. Water flow to the roots was computed using a linear approximation of radial flow through the soil toward the axis of the roots across concentric shells. Root length density and soil rooting volume within four separate layers or compartments were included in the model. The simulation was executed in small time step iterations. A small increment of transpiration was translated to a water content deficit at the root and then sequentially through the concentric shells to simulate water uptake and change of soil water potential. The change in soil water potential was used to increment changes in stomatal conductance and transpiration. The output of the model simulated the pattern of diurnal stomatal behavior observed in other types of experiments, as well as the total soil water extraction patterns of young potted citrus trees.

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