Tree/pasture interactions at a range of tree densities in an agroforestry experiment. III. Water uptake in relation to soil hydraulic conductivity and rooting patterns

1990 ◽  
Vol 41 (4) ◽  
pp. 709 ◽  
Author(s):  
J Eastham ◽  
CW Rose ◽  
DM Cameron ◽  
SJ Rance ◽  
T Talsma ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Root Length ◽  
Tree Density ◽  
Soil Hydraulic Conductivity ◽  
Tree Transpiration ◽  
Rooting Patterns ◽  
Soil Hydraulic ◽  
Water Contents

Eucalyptus grandis was planted in a Nelder fan design in November 1983 into a previously established pasture dominated by Setaria sphacelata cv. Kazungula, at the CSIRO Sanford Pasture Research Station, Queensland, Australia. Nine concentric rings of 18 trees were planted at radii of 4.4-61.6 m, giving a range of tree densities which decreased from 3580 to 42 stems/ha. Tree transpiration was studied at three tree densities (2150, 304 and 82 stems/ha, representing high, medium and low densities) over a 'drought' period of approximately 1 yr (Nov. 1985-Sep. 1986) and related to rooting patterns and soil hydraulic properties. Over the range of soil water contents studied, the ratio of tree transpiration rate to equilibrium evaporation rate (T/Esub(eq)) decreased linearly with decreasing mean soil water content at each tree density. To investigate the effects of soil hydraulic conductivity and root length density on the total transpirational flux, overall soil conductances (Ksub(s)) were calculated, with soil conductance in each horizon weighted according to the length of root in that horizon. At each tree density, decreases in the ratio T/Esub(eq) were related to decreases in ln Ksub(s) measured at 1.2 m from the stem. A more rapid decrease in T/Esub(eq) with decrease in water content observed at the low tree density was attributed to a greater decrease in Ksub(s) as mean water contents decreased. The greater decrease in Ksub(s) at low tree densities was associated with a larger proportion of water extracted and a higher proportion of total root length in surface soil horizons, which showed a greater decrease in hydraulic conductivity than subsoil horizons for the same decrease in water content.

A parameterised equation to estimate soil hydraulic conductivity in the field

Soil Research ◽  
2004 ◽  
Vol 42 (3) ◽  
pp. 283 ◽  
Author(s):  
K. Reichardt ◽  
L. C. Timm ◽  
O. O. S. Bacchi ◽  
J. C. M. Oliveira ◽  
D. Dourado-Neto
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Water Dynamics ◽  
Water Drainage ◽  
Soil Water Dynamics ◽  
Soil Hydraulic Conductivity ◽  
Exponential Character ◽  
Simplifying Assumptions ◽  
Soil Hydraulic

The description of soil water dynamics using the Darcy–Buckingham approach involves the determination and use of soil hydraulic conductivity K v. soil water content θ functions. Many of the methods developed for the measurement of K are based on simplifying assumptions, such as the unit gradient and the choice of fixed models for the K(θ) relation. The need of quick, simple, and inexpensive methods to measure K(θ) in the field using a large number of replicates has also led soil physicists to develop simple methods. This paper presents a procedure that makes use of parameters of equations used to explain the internal water drainage process, and that naturally leads to the exponential character of the K(θ) relation. Results show that the parameterised equation represents a more rigorous estimation of K(θ), compared with the methods that assume unit gradient.

Libardi's method refinement for soil hydraulic conductivity measurement

Soil Research ◽  
2001 ◽  
Vol 39 (4) ◽  
pp. 851 ◽  
Author(s):  
P. L. Libardi ◽  
P. L. Libardi ◽  
K. Reichardt ◽  
K. Reichardt
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Conductivity Measurement ◽  
Soil Surface ◽  
Hydraulic Gradient ◽  
Saturated Soil ◽  
Soil Hydraulic Conductivity ◽  
Soil Hydraulic

The method of Libardi to estimate soil hydraulic conductivity in the field, during the redistribution of soil water, is discussed and improved. It is shown that if the saturated soil water content is measured at the soil surface, values at any other depth can be calculated from the database used to compute hydraulic conductivity. Since the saturated soil water content is difficult to measure and critical to the establishment of the hydraulic conductivity functions, this is an important refinement of the method. It is also shown that the unit hydraulic gradient assumption, which is part of the methodology, does not introduce significant errors in the estimation of soil hydraulic conductivity.

The WormEx I Experiment: Effects of biopores and earthworm holes on soil hydraulic conductivity, sorptivity and macroscopic capillary length

2020 ◽  
Author(s):  
Dario Pezzotti ◽  
Marco Peli ◽  
Roberto Ranzi ◽  
Stefano Barontini
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Soil Conditions ◽  
Pressure Potential ◽  
Capillary Length ◽  
Soil Hydraulic Conductivity ◽  
Adverse Conditions ◽  
Soil Hydraulic ◽  
Infiltration Tests

<p>The WormEx I Experiment was launched on 9 March 2016 to investigate the effects of biopores and earthworms holes on soil-water constitutive laws.<br>Particularly, changes in the soil hydraulic conductivity, in the soil sorptivity and in the macroscopic capillary length were evaluated in different soil conditions, by means of infiltrometric tests performed in a shallow anthropogenic soil of the Central Italian Alps (Cividate Camuno, Italy).<br>About 50 field infiltration tests were performed by means of a tension infiltrometer (TI) and by means of a small single ring infiltrometer, in view of applying the simplified BEST method (Beerkan Estimation of Soil Transfer parameters).<br>The worms presence was accounted for by counting worms' castings in 1 m<sup>2</sup> experimental plots, and it was considered a proxy of the biogenic activity.<br>Various meteorological conditions and various conditions of the presence of worms' castings were sampled during a period of three years.<br>Obtained results highlight how soil hydrological properties change depending on the biopores presence.</p><p>As a result, the hydraulic conductivity greatly increased in presence of soil biopores, both in ponding and in near-saturation conditions.<br>Conductivity at saturation increased on average by 45% (TI method), between great and small presence of earthworms' holes.<br>Considering soil conditions that stimulate the biological activity (e.g. the previous days precipitation and the great water content at the beginning of the infiltration tests), the conductivity at saturation increased more, i.e. by 85% (TI) and by 105% (BEST) on average.<br>The increase is even more relevant passing from adverse conditions (low castings number and small initial soil-water content) to optimal conditions (high castings number and great initial soil-water content).<br>In these cases average increments are more than 200% (TI).</p><p>Also the hydraulic conductivity of the nearly saturated soil, with pressure potential ranging between -5 cm and  0 cm, meaningfully increased in case of biopores presence.<br>The greatest (relative) increase of the soil hydraulic conductivity was observed in most of the cases at a pressure potential of -2 cm.</p><p>Sorptivity meaningfully increased from low to high wormholes number (45% at saturation) and from optimal to adverse conditions (114% at saturation).<br>As for the hydraulic conductivity, this increase was even greater nearby ponding conditions.<br>Field-tests results changed greatly depending on time and space: great standard deviations were observed for both hydraulic conductivity and sorptivity at all the values of pressure potential.</p><p>The macroscopic capillary length λ<sub>c</sub>, which provides concise information about the soil attitude to diffusion, determined by numerically evaluating the subtended area to the experimental hydraulic-conductivity curve, also evidenced the presence of earthworms' burrows, ranging from 16.9 mm to  11.6 mm in optimal and adverse conditions respectively.</p>

Routine measurement of the soil water potential gradient near saturation using a pair of tube tensiometers

Soil Research ◽  
2001 ◽  
Vol 39 (5) ◽  
pp. 1147 ◽  
Author(s):  
P. A. Hutchinson ◽  
W. J. Bond
Keyword(s):  
Hydraulic Conductivity ◽  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Potential Gradient ◽  
Darcy's Law ◽  
Deep Drainage ◽  
Soil Hydraulic Conductivity ◽  
Soil Hydraulic ◽  
Water Potential Gradient

We describe a new tensiometer for routine measurements of the soil water potential near saturation. The device is called the tube tensiometer because it is a long, open-topped, vertical tube (>1 m long) that is filled with porous material. The tube tensiometer has advantages over other known tensiometers as it does not require maintenance when the sensing tip dries beyond its air entry pressure and it is capable of being completely buried beyond the cultivation zone so that it does not foul tillage and harvesting equipment. The disadvantage of the tube tensiometer is that it only operates in the range of soil water potentials from –L to 0 cm of water, where L is the length of the tube tensiometer. The output from the tube tensiometer was compared with mercury tensiometers in a 120-day controlled field drainage and evaporation experiment. The regression between instruments was high (r2 = 0.99) and the accuracy of the tube tensiometer was <0.5 cm of water. The soil water potential gradient near saturation can be measured by installing a pair of vertically separated tube tensiometers. If the soil hydraulic conductivity is known then the soil water flux near saturation can be estimated using Darcy's Law. When the installation depth is below the active rooting zone of a crop then deep drainage can be estimated. This application of the tube tensiometer was demonstrated by measuring the vertical soil water potential gradient at a depth of 1 m beneath a wheat field near Harden, NSW, in response to winter rainfall. The major limitation to the use of Darcy's Law for the routine monitoring of deep drainage remains the estimation of the soil hydraulic conductivity. Ongoing work is focussing on the use of tube tensiometers to provide simultaneous measurements of both hydraulic gradient and hydraulic conductivity.

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>

scholarly journals Assessing Water Infiltration and Soil Water Repellency in Brazilian Atlantic Forest Soils

2020 ◽  
Vol 10 (6) ◽  
pp. 1950 ◽  
Author(s):  
Sergio Esteban Lozano-Baez ◽  
Miguel Cooper ◽  
Silvio Frosini de Barros Ferraz ◽  
Ricardo Ribeiro Rodrigues ◽  
Laurent Lassabatere ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Atlantic Forest ◽  
Water Repellency ◽  
Water Infiltration ◽  
Brazilian Atlantic Forest ◽  
Soil Water Repellency ◽  
Soil Hydraulic Conductivity ◽  
Soil Hydraulic ◽  
Remnant Forest

This study presents the results of the soil hydraulic characterization performed under three land covers, namely pasture, 9-year-old restored forest, and remnant forest, in the Brazilian Atlantic Forest. Two types of infiltration tests were performed, namely tension (Mini-Disk Infiltrometer, MDI) and ponding (Beerkan) tests. MDI and Beerkan tests provided complementary information, highlighting a clear increase of the hydraulic conductivity, especially at the remnant forest plots, when moving from near-saturated to saturated conditions. In addition, measuring the unsaturated soil hydraulic conductivity with different water pressure heads allowed the estimation of the macroscopic capillary length in the field. This approach, in conjunction with Beerkan measurements, allowed the design better estimates of the saturated soil hydraulic conductivity under challenging field conditions, such as soil water repellency (SWR). This research also reports, for the first time, evidence of SWR in the Atlantic Forest, which affected the early stage of the infiltration process with more frequency in the remnant forest.

Assessing Water Infiltration and Soil Water Repellency in Brazilian Atlantic Forest Soils

2020 ◽  
Author(s):  
Sergio Esteban Lozano-Baez ◽  
Miguel Cooper ◽  
Silvio Frosini de Barros Ferraz ◽  
Ricardo Ribeiro Rodrigues ◽  
Mirko Castellini ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Atlantic Forest ◽  
Water Repellency ◽  
Water Infiltration ◽  
Brazilian Atlantic Forest ◽  
Soil Water Repellency ◽  
Soil Hydraulic Conductivity ◽  
Soil Hydraulic ◽  
Remnant Forest

<p>This study presents the results of the soil hydraulic characterization performed under three land covers, namely pasture, 9-year-old restored forest, and remnant forest, in the Brazilian Atlantic Forest. Two types of infiltration tests were performed, namely tension (Mini-Disk Infiltrometer, MDI) and ponding (Beerkan) tests. MDI and Beerkan tests provided a complementary information, highlighting a clear increase of the hydraulic conductivity, especially at the remnant forest plots, when moving from near-saturated to saturated conditions. In addition, measuring the unsaturated soil hydraulic conductivity with different water pressure heads also allowed to estimate the macroscopic capillary length in the field. This approach, in conjunction with Beerkan measurements, allowed to generate better estimates of the saturated soil hydraulic conductivity under challenging field conditions, such as soil water repellency (SWR). This research also reports for the first time evidence of SWR in the Atlantic Forest, which affected the early stage of the infiltration process with more frequency in the remnant forest.</p>

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