scholarly journals Modeling stomatal conductance in the Earth system: linking leaf water-use efficiency and water transport along the soil-plant-atmosphere continuum

2014 ◽  
Vol 7 (3) ◽  
pp. 3085-3159 ◽  
Author(s):  
G. B. Bonan ◽  
M. Williams ◽  
R. A. Fisher ◽  
K. W. Oleson
Keyword(s):  
Soil Moisture ◽  
Stomatal Conductance ◽  
Water Use Efficiency ◽  
Water Use ◽  
Functional Dependence ◽  
Moisture Stress ◽  
Leaf Water ◽  
Sensitivity Analyses ◽  
Carbon Gain ◽  
Use Efficiency

Abstract. The empirical Ball–Berry stomatal conductance model is commonly used in Earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must both be empirically parameterized. We evaluated the Ball–Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil–plant–atmosphere continuum (SPA) to numerically optimize photosynthetic carbon gain per unit water loss while preventing leaf water potential dropping below a critical minimum level. We evaluated two alternative optimization algorithms: intrinsic water-use efficiency (Δ An/Δ gs, the marginal carbon gain of stomatal opening) and water-use efficiency (Δ An/Δ El, the marginal carbon gain of water loss). We implemented the stomatal models in a multi-layer plant canopy model, to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using: (1) leaf analyses; (2) canopy net radiation, sensible heat flux, latent heat flux, and gross primary production at six AmeriFlux sites spanning 51 site–years; and (3) parameter sensitivity analyses. Without soil moisture stress, the performance of the SPA stomatal conductance model was generally comparable to or somewhat better than the Ball–Berry model in flux tower simulations, but was significantly better than the Ball–Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from the physiological theory linking leaf water-use efficiency and water flow to and from the leaf along the soil-to-leaf pathway rather than being imposed a priori, as in the Ball–Berry model. Similar functional dependence of gs on Ds emerged from the water-use efficiency optimization. Sensitivity analyses showed that two parameters (stomatal efficiency and root hydraulic conductivity) minimized errors with the SPA stomatal conductance model. The critical stomatal efficiency for optimization (ι) was estimated from leaf trait datasets and is related to the slope parameter (g1) of the Ball–Berry model. The optimized parameter value was consistent with this estimate. Optimized root hydraulic conductivity was consistent with estimates from literature surveys. The two central concepts embodied in the stomatal model, that plants account for both water-use efficiency and for hydraulic safety in regulating stomatal conductance, imply a notion of optimal plant strategies and provide testable model hypotheses, rather than empirical descriptions of plant behavior.

scholarly journals Modeling stomatal conductance in the earth system: linking leaf water-use efficiency and water transport along the soil–plant–atmosphere continuum

2014 ◽  
Vol 7 (5) ◽  
pp. 2193-2222 ◽  
Author(s):  
G. B. Bonan ◽  
M. Williams ◽  
R. A. Fisher ◽  
K. W. Oleson
Keyword(s):  
Soil Moisture ◽  
Stomatal Conductance ◽  
Water Use Efficiency ◽  
Water Use ◽  
Functional Dependence ◽  
Moisture Stress ◽  
Leaf Water ◽  
Carbon Gain ◽  
Soil Moisture Stress ◽  
Use Efficiency

Abstract. The Ball–Berry stomatal conductance model is commonly used in earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must be empirically parameterized. We evaluated the Ball–Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil–plant–atmosphere continuum (SPA). The SPA model simulates stomatal conductance numerically by (1) optimizing photosynthetic carbon gain per unit water loss while (2) constraining stomatal opening to prevent leaf water potential from dropping below a critical minimum. We evaluated two optimization algorithms: intrinsic water-use efficiency (ΔAn /Δgs, the marginal carbon gain of stomatal opening) and water-use efficiency (ΔAn /ΔEl, the marginal carbon gain of transpiration water loss). We implemented the stomatal models in a multi-layer plant canopy model to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using leaf analyses, eddy covariance fluxes at six forest sites, and parameter sensitivity analyses. The primary differences among stomatal models relate to soil moisture stress and vapor pressure deficit responses. Without soil moisture stress, the performance of the SPA stomatal model was comparable to or slightly better than the CLM Ball–Berry model in flux tower simulations, but was significantly better than the CLM Ball–Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from water flow along the soil-to-leaf pathway rather than being imposed a priori, as in the CLM Ball–Berry model. Similar functional dependence of gs on Ds emerged from the ΔAn/ΔEl optimization, but not the ΔAn /gs optimization. Two parameters (stomatal efficiency and root hydraulic conductivity) minimized errors with the SPA stomatal model. The critical stomatal efficiency for optimization (ι) gave results consistent with relationships between maximum An and gs seen in leaf trait data sets and is related to the slope (g1) of the Ball–Berry model. Root hydraulic conductivity (Rr*) was consistent with estimates from literature surveys. The two central concepts embodied in the SPA stomatal model, that plants account for both water-use efficiency and for hydraulic safety in regulating stomatal conductance, imply a notion of optimal plant strategies and provide testable model hypotheses, rather than empirical descriptions of plant behavior.

Hydraulic limitations and water-use efficiency in Pinus pinaster along a chronosequence

2008 ◽  
Vol 38 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Federico Magnani ◽  
Abdelkader Bensada ◽  
Sergio Cinnirella ◽  
Francesco Ripullone ◽  
Marco Borghetti
Keyword(s):  
Stomatal Conductance ◽  
Water Use Efficiency ◽  
Water Potential ◽  
Water Use ◽  
Leaf Water Potential ◽  
Pinus Pinaster ◽  
Hydraulic Conductance ◽  
Leaf Water ◽  
Stand Development ◽  
Use Efficiency

Hydraulic constraints to water transport and water-use efficiency were studied in a Pinus pinaster Ait. chronosequence in Italy, consisting of four even-aged stands ranging from young (10 years old) to mature (75 years old), to explore the mechanisms involved in the decline of stand productivity as tree grow taller. Leaf-specific transpiration was estimated from sapflow rates measured by the heat dissipation technique, leaf-specific hydraulic conductance was computed from the slope of the relationship between transpiration and leaf water potential, long-term water-use efficiency was estimated from carbon isotope discrimination (Δ13C) in xylem cores, and photosynthetic capacity was assessed from CO2 assimilation/CO2 intercellular concentration curves. Leaf-specific transpiration decreased with stand development, suggesting a reduction in stomatal conductance, and a negative relationship was found between leaf-specific hydraulic conductance and tree height, suggesting a role of hydraulic constraints in the decline of current annual increment. Minimum daily leaf water potential did not change with stand height, suggesting that homeostasis in leaf water potential is achieved through a reduction in leaf transpiration. The Δ13C values increased with stand development, indicating a decline of water-use efficiency. Leaf level stomatal conductance was higher in the younger stand; no significant difference in maximum carboxylation rate was found among stands.

Partial rootzone drying increases water-use efficiency of lemon Fino 49 trees independently of root-to-shoot ABA signalling

2012 ◽  
Vol 39 (5) ◽  
pp. 366 ◽  
Author(s):  
J. G. Pérez-Pérez ◽  
I. C. Dodd ◽  
P. Botía
Keyword(s):  
Stomatal Conductance ◽  
Water Use Efficiency ◽  
Water Potential ◽  
Water Use ◽  
Leaf Water Potential ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Leaf Water ◽  
Use Efficiency ◽  
Partial Rootzone Drying

To determine whether irrigation strategy altered the sensitivity of Citrus leaf gas exchange to soil, plant and atmospheric variables, mature (16-year-old) Fino 49 lemon trees (Citrus limon (L.) Burm. fil. grafted on Citrus macrophylla Wester) were exposed to three irrigation treatments: control (irrigated with 100% of crop potential evapotranspiration, ETc), deficit irrigation (DI) and partial rootzone drying (PRD) treatments,which received 75% ETc during the period of highest evaporative demand and 50% ETc otherwise. Furthermore, to assess the physiological significance of root-to-shoot ABA signalling, the seasonal dynamics of leaf xylem ABA concentration ([X-ABA]leaf) were evaluated over two soil wetting–drying cycles during a 2-week period in summer. Although stomatal conductance (gs) declined with increased leaf-to-air vapour pressure deficit (LAVPD), lower leaf water potential and soil water availability, [X-ABA]leaf was only related to stomatal closure in well irrigated trees under moderate (<2.5 kPa) atmospheric vapour pressure deficit (VPD). Differences in [X-ABA]leaf were not detected between treatments either before or immediately after (<12 h) rewatering the dry side of PRD trees. Leaf water potential was higher in control trees, but decreased similarly in all irrigation treatments as daily LAVPD increased. In contrast, DI and PRD trees showed lower stomatal sensitivity to LAVPD than control trees. Although DI and PRD decreased stomatal conductance and photosynthesis, these treatments did not significantly decrease yield, but PRD increased crop water use efficiency (WUE) by 83% compared with control trees. Thus PRD-induced enhancement of crop WUE in a semiarid environment seems to involve physiological mechanisms other than increased [X-ABA]leaf.

EFFECT OF SOIL MOISTURE STRESS ON YIELD, WATER-USE EFFICIENCY AND MINERAL COMPOSITION OF OATS AND ALFALFA GROWN AT TWO FERTILITY LEVELS

1962 ◽  
Vol 42 (1) ◽  
pp. 7-12 ◽  
Author(s):  
S. J. Bourget ◽  
R. B. Carson
Keyword(s):  
Soil Moisture ◽  
Water Use Efficiency ◽  
Water Use ◽  
Phosphorus Content ◽  
Soil Phosphorus ◽  
Moisture Stress ◽  
Soil Moisture Stress ◽  
Use Efficiency ◽  
Crops Yield ◽  
Nitrogen Phosphorus

Yields of oats and alfalfa grown in two soils in the greenhouse, with and without fertilizer, usually decreased with increasing moisture stress obtained by depleting the available moisture to 75, 50, 25 and nearly 0 per cent.An application of 6-20-20 fertilizer for oats and of 0-20-20 for alfalfa at the rate of 1000 pounds per acre gave a marked increase in crops yield and it resulted in a more efficient use of water by the crops than was obtained without fertilizer, although the total amount of water used was greater with than without fertilizer. The water-use efficiency values for oats usually increased with decreasing available water whereas those for alfalfa were less consistent.The composition in nitrogen, phosphorus, potassium, calcium and magnesium of the plant tissues did not vary greatly. However, the phosphorus content of oats grain decreased with increasing soil moisture stress unless fertilizer was added, indicating that soil phosphorus became less available for oats at high moisture stress.

scholarly journals Hydro-Priming of Seed Improves the Water Use Efficiency, Grain Yield and Net Economic Return of Wheat under Different Moisture Regimes

2014 ◽  
Vol 11 (2) ◽  
pp. 149-159 ◽  
Author(s):  
Raj Pal Meena ◽  
R Sendhil ◽  
SC Tripathi ◽  
Subhash Chander ◽  
RS Chhokar ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Grain Yield ◽  
Water Use Efficiency ◽  
Water Use ◽  
Seed Priming ◽  
Moisture Stress ◽  
Plain Water ◽  
Crop Establishment ◽  
Use Efficiency ◽  
Dry Soil

Wheat is the second most important staple food crop of India and contributes a major share to food basket of the country. Since majority of the area under wheat is irrigated, it consumes huge quantity of fresh water for its cultivation. The availability of good quality water for irrigation is decreasing over a period of time due to vagaries of monsoon, urbanization and industrialization. The biggest challenge on this front is to improve the efficiency and productivity of water being used in existing cropping system. Therefore, it is the need of hour to improve water use efficiency for wheat production. In the milieu, the present investigation was taken with an objective of studying the effect of pre-germinated seed in crop establishment under sub-optimal soil moisture conditions by using the residual soil moisture after harvesting of rice in Indo-Gangetic plains, so that pre sowing irrigation requirement for crop establishment may be cut and reduced in time period which require from pre-sowing irrigation to field preparation. This experiment was conducted for two consecutive years 2010-11 and 2011-12 to evaluate the influence of hydropriming on the water use efficiency and grain yield of wheat (Triticum aestivum L.) under moisture stress. The experiment was conducted in split plot design with three replications keeping moisture stress treatments (optimum moisture, sub-optimal moisture and dry soil followed by irrigation) in main plots and seed priming treatments (dry seed, hydropriming, and pre-germinated seeds) in subplots. Pregerminated seed produced significantly higher grain yield (5.49 t ha-1), which was statistically similar to hydropriming (5.30 t ha-1). Various seeding methods were statistically at par. The hydro-primed and pregerminated seeds established earlier than dry seeds leading to better crop establishment under optimum, sub optimum soil moisture as well as dry soil conditions leading to higher tillering and grain yield. The results of experiment showed that priming with plain water and pre-germinated seeds improved germination indices, seedling growth and crop establishment. Since priming with plain water and to have pregerminated seeds is simple and cheap method, which can increase germination percentage and homogeneity of seedling emergence under water stress conditions and it can be easily used by farmers. Interactive effect of different seed priming techniques along with seeding at sub optimal soil moisture level proved to be an efficient technique for enhancing water productivity of wheat crop. DOI: http://dx.doi.org/10.3329/sja.v11i2.18410 SAARC J. Agri., 11(2): 149-159 (2013)

scholarly journals Root−to−Shoot Signaling and Leaf Water−Use Efficiency in Peach Trees under Localized Irrigation

Agronomy ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 437
Author(s):  
Evangelos Xylogiannis ◽  
Adriano Sofo ◽  
Bartolomeo Dichio ◽  
Giuseppe Montanaro ◽  
Alba N. Mininni
Keyword(s):  
Stomatal Conductance ◽  
Water Use Efficiency ◽  
Water Use ◽  
Water Status ◽  
Water Productivity ◽  
Stomatal Closure ◽  
Leaf Water ◽  
Ground Water Recharge ◽  
Use Efficiency ◽  
Soil Volume

Global climate change is affecting important natural resources including water. Increasing temperature will change rate of evaporation and transpiration, leading to variations in water availability, ground water recharge, and water consumption by plants. Thus, competition for water will be a major future challenge for agriculture. Increasing water productivity at farm level is necessary to increase the efficiency of the irrigation system, plant water−use efficiency (WUE) and to optimize irrigation management. We test the hypothesis that in field−grown, drip−irrigated nectarine trees, the roots in the un−irrigated inter−row soil produce chemical signals that increase in summer to induce stomatal closure and so increase WUE. Concentrations of abscisic acid (ABA) were determined in leaf, root, and xylem sap of drip−irrigated (D) trees in which only about 25% of the soil volume was wetted and compared with those of trees irrigated using microjets (M) in which the whole soil volume was wetted. We also examined the effects of increased ABA on root−to−shoot dry matter ratio, the ratio ABA to indole−3−acetic acid (IAA), sap pH, and fruit and shoot growth. Both D and M trees were maintained at optimal water status as judged by pre−dawn leaf water potentials (about −0.3 MPa). There were no significant differences between treatments in mean fruit size (fruit diameter) or in tree yield (total fruit weight). However, shoot length was strongly reduced in D trees (to 75%) compared to M trees (100%). The concentrations of ABA in the inter−row roots of D trees were increased by 59% and that in the leaves by 13% compared to in the M trees. Despite the similar water status of D and M trees, a clear chemical signal was triggered in terms of a significant increase in the ABA/IAA ratio. This signal influenced leaf stomatal conductance which was 40% lower in D trees than in M trees. The associated responses in photosynthesis and transpiration raised the WUE of D trees by 7%–10% compared to M trees. This field study shows that in drip−irrigated trees, an ABA root−to−shoot signal issues from the inter−row roots growing in soil that dries out during a Mediterranean summer (hot, low rainfall). This ABA−induced WUE increase was achieved principally through reduced stomatal conductance and reduced transpiration.

scholarly journals Differential water-use efficiency and growth among Eucalyptus grandis hybrids under two different rainfall conditions

2020 ◽  
Vol 29 (2) ◽  
pp. e006
Author(s):  
José Gándara ◽  
Silvia Ross ◽  
Gastón Quero ◽  
Dellacassa Gonzalo ◽  
Dellepiane Joaquín ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Water Use Efficiency ◽  
Water Potential ◽  
Water Use ◽  
Leaf Water Potential ◽  
Eucalyptus Grandis ◽  
Leaf Water ◽  
Daily Fluctuation ◽  
Leaf Transpiration ◽  
Use Efficiency

Aim of the study: To analyze the course of leaf water status, water-use efficiency and growth in Eucalyptus grandis and hybrids throughout seasons with different rainfall.Area of study: The study was conducted in northern Uruguay.Methods: A randomized block trial was established containing E. grandis (ABH17), E. grandis × Eucalyptus camaldulensis (GC172), E. grandis × Eucalyptus tereticornis (GT529), and E. grandis × Eucalyptus urophylla (GU08). Predawn leaf water potential (Ψpd) and midday leaf water potential (Ψmd) were measured every six weeks from the age of 16 months, throughout two growing seasons. Stomatal conductance (gs), net photosynthetic rate (A), and leaf-level transpiration (E) were measured once in each growing season, along with leaf carbon isotope discrimination (∆13C) and tree growth. Stomatal density and distribution were studied.Results: ABH17 and GU08 had the lowest daily fluctuation of leaf water potential and showed stronger stomatal regulation; they were hypostomatic, and stomata on the adaxial leaf surfaces remained immature. GC172 and GT529 (Red-Gum hybrids) were amphistomatic and transpired more intensively; they were less efficient in instantaneous and intrinsic water use and grew faster under high soil moisture (inferred from rainfall). Under such conditions, GC172 reached the highest gas-exchange rate due to an increase in tree hydraulic conductance. ABH17 and GU08 were hypostomatic and used water more efficiently because of stronger stomatal regulation.Research highlights: Red-Gum hybrids evidenced less water use efficiency due to lower stomatal regulation, different stomatal features, and distinct growth patterns as a function of soil moisture (inferred from rainfall).Keywords: Eucalypt hybrids; stomatal conductance; water-use efficiency; transpiration.Abbreviations used: Ψpd:predawn leaf water potential;Ψmd: midday leaf water potential; ΔΨ: daily fluctuation of leaf water potential ( ; A: net photosynthetic rate, E: leaf transpiration rate, gs: stomatal conductance, WUE: instantaneous water-use efficiency; WUEi: integrated water-use efficiency; A/E: leaf photosynthesis-to-leaf transpiration ratio; ∆13C: leaf carbon isotope discrimination; K: tree hydraulic conductance; E/∆Ψ: ratio between leaf transpiration and daily fluctuation of leaf water potential; δ13C: natural abundance of 13C.

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