scholarly journals Simulation of Evapotranspiration and Its Response to Plant Water and CO2 Transfer Dynamics

2008 ◽  
Vol 9 (3) ◽  
pp. 426-443 ◽  
Author(s):  
Shusen Wang
Keyword(s):  
Water Potential ◽  
Correlation Coefficient ◽  
Soil Water Potential ◽  
Flux Measurement ◽  
Co2 Concentration ◽  
Absolute Error ◽  
Water Transfer ◽  
Eddy Correlation ◽  
Plant Water ◽  
Transfer Scheme

Abstract Evapotranspiration (ET) is controlled by atmospheric demand, plant and soil hydraulic constraints, and the plant physiological activities that determine canopy resistance. This paper introduces a new ET scheme developed for the Ecological Assimilation of Land and Climate Observations (EALCO) model that integrates these controls into one dynamic system. This scheme is based on solving the governing equation system that represents the coupled canopy energy–water–CO2 transfer dynamics, where the canopy temperature Tc, plant water potential ψc, and leaf intercellular CO2 concentrations Ci are simultaneously obtained and used in ET calculations. Modeled ET was compared with eddy correlation flux measurement at a boreal aspen forest. Results showed that the correlation coefficient (R) between modeled and measured daily ET was greater than 0.96. The average absolute error was approximately 0.3 mm day−1. Modeled ET was generally higher than measured ET by 10%. This is consistent with the energy balance closure analyses from observations that showed that turbulent energy flux was frequently less than 90% of the total available energy. The effects of the plant CO2 and water transfer dynamics on ET simulations were investigated by running the model in two additional settings. These were 1) static Ci—where the ratio of Ci to atmospheric CO2 concentration was set to a constant value, and 2) static ψc—where the ψc was linearly related to soil water potential. The dynamic CO2 transfer scheme and the static Ci scheme produced relatively small differences in ET that mainly occurred at a subdaily time scale. Differences in ET produced using the dynamic water transfer scheme and the static ψc scheme depended on ecosystem water conditions and were more significant when the plant was under water stress. Ignoring the dynamic water transfer process in the model decreased the correlation coefficient between modeled and measured ET more significantly in drier years. This implies that the dynamic water transfer scheme is of more importance for ET estimates in arid or semiarid ecosystems.

Water relations of winter wheat. 5. The root system and osmotic adjustment in relation to crop evaporation

1984 ◽  
Vol 102 (2) ◽  
pp. 415-425 ◽  
Author(s):  
M. McGowan ◽  
P. Blanch ◽  
P. J. Gregory ◽  
D. Haycock
Keyword(s):  
Winter Wheat ◽  
Water Potential ◽  
Root System ◽  
Soil Water ◽  
Osmotic Adjustment ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Plant Water ◽  
Potential Evaporation ◽  
Plant Water Potential

SummaryShoot and root growth and associated leaf and soil water potential relations were compared in three consecutive crops of winter wheat grown in the same field. Despite a profuse root system the crop grown in the second drought year (1976) failed to dry the soil as throughly as the crops in 1975 and 1977. Measurements of plant water potential showed that the restricted utilization of soil water reserves by this crop was associated with failure to make any significant osmotic adjustment, leading to premature loss of leaf turgor and stomatal closure. The implications of these results for models to estimate actual crop evaporation from values of potential evaporation are discussed.

scholarly journals The impact of broadleaved woodland on water resources in lowland UK: I. Soil water changes below beech woodland and grass on chalk sites in Hampshire

2005 ◽  
Vol 9 (6) ◽  
pp. 596-606 ◽  
Author(s):  
J. Roberts ◽  
P. Rosier
Keyword(s):  
Energy Balance ◽  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Water Potential ◽  
Eddy Correlation ◽  
Seasonal Differences ◽  
Water Potential Measurements ◽  
Shallow Soils

Abstract. The possible effects of broadleaved woodland on recharge to the UK Chalk aquifer have led to a study of evaporation and transpiration from beech woodland (Black Wood) and pasture (Bridgets Farm), growing in shallow soils above chalk in Hampshire. Eddy correlation measurements of energy balance components above both the forest and the grassland enabled calculation of latent heat flux (evaporation and transpiration) as a residual. Comparative measurements of soil water content and soil water potential in 9 m profiles under both forest and grassland found changes in soil water content down to 6 m at both sites; however, the soil water potential measurements showed upward movement of water only above a depth of about 2 m. Below this depth, water continued to drain and the soil water potential measurements showed downward movement of water at both sites, notwithstanding significant negative soil water potentials in the chalk and soil above. Seasonal differences occur in the soil water content profiles under broadleaved woodland and grass. Before the woodland foliage emerges, greater drying beneath the grassland is offset in late spring and early summer by increased drying under the forest. Yet, when the change in soil water profiles is at a maximum, in late summer, the profiles below woodland and grass are very similar. A comparison of soil water balances for Black Wood and Bridgets Farm using changes in soil water contents, local rainfall and evaporation measured by the energy balance approach allowed drainage to be calculated at each site. Although seasonal differences occurred, the difference in cumulative drainage below broadleaved woodland and grass was small.

Soil water potential does not affect leaf morphology or cuticular characters important for palaeo-environmental reconstructions in southern beech, Nothofagus cunninghamii (Nothofagaceae)

2012 ◽  
Vol 60 (2) ◽  
pp. 87 ◽  
Author(s):  
Mark J. Hovenden ◽  
Jacqueline K. Vander Schoor
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Availability ◽  
Leaf Morphology ◽  
Soil Water Potential ◽  
Co2 Concentration ◽  
Environmental Reconstruction ◽  
Leaf Form ◽  
Southern Beech ◽  
The Impact

Leaf form is closely related to local prevailing abiotic conditions and thus the morphology of fossil and sub-fossil leaves is often used to reconstruct both historical and palaeo-environmental conditions. However, palaeo-environmental reconstruction is difficult because leaf form is controlled potentially by many interacting environmental factors such as temperature, CO2 concentration, light and water availability. We used a glasshouse trial to investigate the impact of water availability on the leaf and cuticle morphology of a species important for palaeo-environmental reconstruction, the southern beech, Nothofagus cunninghamii. We found that reducing soil water potential to –0.2 or –0.5 MPa had no impact on leaf form or cuticular characters, despite reducing leaf carbon assimilation and severely restricting plant growth. Although plant accession affected many leaf characters, there were few significant impacts of altitude of origin and no substantial interactions between altitude of origin and soil water potential. Thus, both cuticular and gross leaf morphology seem to be stable across a range of soil water potentials in this species, meaning that palaeo-environmental signals from this species are unlikely to be affected by changes in water availability.

Soil Moisture as Predictor of Plant Water Status

2021 ◽  
Vol 47 (3) ◽  
pp. 110-115
Author(s):  
Johannes Hertzler ◽  
Steffen Rust
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Status ◽  
Soil Water Potential ◽  
Irrigation Scheduling ◽  
Plant Water Status ◽  
Plant Water ◽  
Estimation Errors ◽  
Plant Available Water ◽  
The Relationship

Soil water potential can be used as a proxy for plant available water in irrigation scheduling. This study investigated the relationship between soil water potential and plant water status of pines (Pinus sylvestris L.) planted into two different substrates. Predawn leaf water potential as a well-established measure of the plant water status and soil water potential correlated very well. However, estimating the plant water status from individual sensor readings is subject to significant estimation errors. Furthermore, it was shown that heterogeneous soil/root ball combinations can lead to critical effects on the soil water balance, and that sensors installed outside of the root balls cannot estimate the plant water status without site-specific calibration.

Location of hydraulic resistance in the soil–plant pathway in seedlings of Pinussylvestris L. grown in peat

1986 ◽  
Vol 16 (1) ◽  
pp. 115-123 ◽  
Author(s):  
Göran Örlander ◽  
Karin Due
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Dry Weight ◽  
Membrane System ◽  
Point Of View ◽  
Plant Water ◽  
Water Conductance ◽  
Dry Conditions ◽  
Total Dry Weight

Seedlings of Pinussylvestris L. were grown in three different soil media: 100% peat, 40% silt–60% peat, and 60% silt–40% peat. The percentages refer to total dry weight. Needle conductance, needle water potential, and plant water conductance were measured at different levels of soil water potentials controlled with a semipermeable membrane system. Seedlings grown in the 60:40 silt–peat mixture had a plant water conductance at a soil water potential of −0.1 MPa 3 times that of seedlings grown in pure peat. In an experiment where the roots were dipped in a silt slurry before planting, it was found that the plant water conductance at low soil water potential (−0.1 MPa) increased more than 2 times compared with undipped controls. We concluded that an important resistance to water flow in the soil–plant pathway was located in the soil outside the roots and probably was the most important resistance in the root–soil interface. The use of low humified peat as a growth medium is open to discussion from a silvicultural point of view because of its hydraulic properties under dry conditions.

scholarly journals Water potential characteristics and yield of summer maize in different planting patterns

2008 ◽  
Vol 54 (No. 1) ◽  
pp. 14-19 ◽  
Author(s):  
L. Quanqi ◽  
C. Yuhai ◽  
L. Mengyu ◽  
Z. Xunbo ◽  
D. Baodi ◽  
...  
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Leaf Water Potential ◽  
North China ◽  
Soil Water Potential ◽  
Soil Layer ◽  
Water Transfer ◽  
Leaf Water ◽  
Summer Maize ◽  
Transfer Resistance

A study was conducted in the Shandong province in North China to investigate the effects of different planting patterns on water potential characteristics of soil-plant-atmosphere continuum (SPAC) and yield of summer maize. Three planting patterns were applied, i.e. bed planting (BE), furrow planting (FU) and flat planting (FL). The results showed that although soil moisture content in 0–20 cm soil layer in BE was decreased, soil temperature was increased; as a result, soil water potential in BE was increased. Compared with FL, leaf water potential in BE and FU was enhanced, but water transfer resistance between soil-leaf and leaf-atmosphere was decreased; feasible water supply conditions were thus created for crops colony. Maize yield of BE and FU was significantly (LSD, <I>P</I> < 0.05) higher than that of FL, by 1326.45 and 1243.76 kg/ha, respectively. These results obtained in field crop conditions support the idea that planting patterns affect soil water potential, leaf water potential, water transfer resistance between soil-leaf and leaf-gas of summer maize in North China.

scholarly journals Horizontal soil water potential heterogeneity: simplifying approaches for crop water dynamics models

2014 ◽  
Vol 11 (1) ◽  
pp. 1203-1252 ◽  
Author(s):  
V. Couvreur ◽  
J. Vanderborght ◽  
L. Beff ◽  
M. Javaux
Keyword(s):  
Analytical Solution ◽  
Winter Wheat ◽  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Water Dynamics ◽  
Implicit Assumption ◽  
Plant Water ◽  
Row Crops ◽  
D Model

Abstract. Soil water potential (SWP) is known to affect plant water status, and even though observations demonstrate that SWP distribution around roots may limit plant water availability, its horizontal heterogeneity within the root zone is often neglected in hydrological models. As motive, using a horizontal discretisation significantly larger than one centimetre is often essential for computing time considerations, especially for large scale hydrodynamics models. In this paper, we simulate soil and root system hydrodynamics at the centimetre scale and evaluate approaches to upscale variables and parameters related to root water uptake (RWU) for two crop systems: a densely seeded crop with an average uniform distribution of roots in the horizontal direction (winter wheat) and a wide-row crop with lateral variations in root density (maize). In a first approach, the upscaled water potential at soil–root interfaces was assumed to equal the bulk SWP of the upscaled soil element. Using this assumption, the 3-D high resolution model could be accurately upscaled to a 2-D model for maize and a 1-D model for wheat. The accuracy of the upscaled models generally increased with soil hydraulic conductivity, lateral homogeneity of root distribution, and low transpiration rate. The link between horizontal upscaling and an implicit assumption on soil water redistribution was demonstrated in quantitative terms, and explained upscaling accuracy. In a second approach, the soil–root interface water potential was estimated by using a constant rate analytical solution of the axisymmetric soil water flow towards individual roots. In addition to the theoretical model properties, effective properties were tested in order to account for unfulfilled assumptions of the analytical solution: non-uniform lateral root distributions and transient RWU rates. Significant improvements were however only noticed for winter wheat, for which the first approach was already satisfying. This study confirms that the use of 1-D spatial discretisation to represent soil-plant water dynamics is a worthy choice for densely seeded crops. For wide-row crops, e.g. maize, further theoretical developments that better account for horizontal SWP heterogeneity might be needed in order to properly predict soil-plant hydrodynamics in 1-D.

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