scholarly journals Trading water for carbon: Sustained photosynthesis at the cost of increased water loss during high temperatures in a temperate forest

2019 ◽  
Author(s):  
Anne Griebel ◽  
Lauren T. Bennett ◽  
Daniel Metzen ◽  
Elise Pendall ◽  
Patrick N.J. Lane ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Water Loss ◽  
Ecosystem Respiration ◽  
Canopy Conductance ◽  
List Type ◽  
Water Fluxes ◽  
Use Efficiency ◽  
The Cost ◽  
The Way

AbstractForest carbon and water fluxes are often assumed to be coupled as a result of stomatal regulation during dry conditions. However, recent observations have indicated increased transpiration rates during isolated heat waves across a range of eucalypt species under experimental and natural conditions, with inconsistent effects on photosynthesis (ranging from an increase to a near total decline). To improve the empirical basis for understanding carbon and water fluxes in forests under hotter and drier climates, we measured the water use of dominant trees, and the ecosystem-scale carbon and water exchange in a mature temperate eucalypt forest over three summer seasons. The forest maintained photosynthesis within 16% of peak photosynthesis rates during all conditions, despite up to 70% reductions in canopy conductance during a 5-day heatwave. While carbon and water fluxes both decreased by 16% on exceptionally dry summer days, GPP was sustained at the cost of up to 74% increased water loss on the hottest days and during the heatwave. This led to ∼40% variation in ecosystem water use efficiency over the three summers, and ∼two-fold differences depending on the way water use efficiency is calculated. Furthermore, the forest became a net source of carbon following a 137% increase in ecosystem respiration during the heat wave, highlighting that the potential for temperate eucalypt forests to remain net carbon sinks under future climates will depend not only on their potential to maintain photosynthesis during higher temperatures, but also on responses of ecosystem respiration to changes in climate.Key PointsGPP of temperate eucalypts was sustained at the cost of increased water use during hot periods, but both fluxes decreased during dry periods.WUE estimates for the same period differed up to two-fold depending on the way it was calculated.Doubling of ecosystem respiration turned the forest from a net sink into a net source of carbon during a longer heatwave.

scholarly journals Remote Sensing of Ecosystem Water Use Efficiency: A Review of Direct and Indirect Estimation Methods

2021 ◽  
Vol 13 (12) ◽  
pp. 2393
Author(s):  
Wanyuan Cai ◽  
Sana Ullah ◽  
Lei Yan ◽  
Yi Lin
Keyword(s):  
Remote Sensing ◽  
Water Use Efficiency ◽  
Analytical Model ◽  
Water Use ◽  
Estimation Methods ◽  
Retrieval Algorithm ◽  
Canopy Conductance ◽  
Coupling Mechanism ◽  
Indirect Methods ◽  
Use Efficiency

Water use efficiency (WUE) is a key index for understanding the ecosystem of carbon–water coupling. The undistinguishable carbon–water coupling mechanism and uncertainties of indirect methods by remote sensing products and process models render challenges for WUE remote sensing. In this paper, current progress in direct and indirect methods of WUE estimation by remote sensing is reviewed. Indirect methods based on gross primary production (GPP)/evapotranspiration (ET) from ground observation, processed models and remote sensing are the main ways to estimate WUE in which carbon and water cycles are independent processes. Various empirical models based on meteorological variables and remote sensed vegetation indices to estimate WUE proved the ability of remotely sensed data for WUE estimating. The analytical model provides a mechanistic opportunity for WUE estimation on an ecosystem scale, while the hypothesis has yet to be validated and applied for the shorter time scales. An optimized response of canopy conductance to atmospheric vapor pressure deficit (VPD) in an analytical model inverted from the conductance model has been also challenged. Partitioning transpiration (T) and evaporation (E) is a more complex phenomenon than that stated in the analytic model and needs a more precise remote sensing retrieval algorithm as well as ground validation, which is an opportunity for remote sensing to extrapolate WUE estimation from sites to a regional scale. Although studies on controlling the mechanism of environmental factors have provided an opportunity to improve WUE remote sensing, the mismatch in the spatial and temporal resolution of meteorological products and remote sensing data, as well as the uncertainty of meteorological reanalysis data, add further challenges. Therefore, improving the remote sensing-based methods of GPP and ET, developing high-quality meteorological forcing datasets and building mechanistic remote sensing models directly acting on carbon–water cycle coupling are possible ways to improve WUE remote sensing. Improvement in direct WUE remote sensing methods or remote sensing-driven ecosystem analysis methods can promote a better understanding of the global ecosystem carbon–water coupling mechanisms and vegetation functions–climate feedbacks to serve for the future global carbon neutrality.

Water-use efficiency, photosynthetic characteristics, and high through-put phenotyping methods for soybean (glycine max) genotypes contrasting in carbon isotope discrimination

2016 ◽  
Author(s):  
◽  
Brett Naylor
Keyword(s):  
Drought Stress ◽  
Grain Yield ◽  
Water Use Efficiency ◽  
Water Use ◽  
Water Loss ◽  
Sap Flow ◽  
Carbon Isotope Discrimination ◽  
Flow Sensors ◽  
Use Efficiency ◽  
Sap Flow Sensors

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Drought is a huge concern for soybean growers across the world, and in the Midwestern US is the main limitation to grain yield. A way to protect against drought stress is for plants to use water more efficiently. Carbon isotope discrimination (CID) is a measured trait that is related to water-use efficiency (WUE), and can be used to screen genotypes for higher WUE. Several genotypes were studied in multiple greenhouse and field experiments with varying drought stress treatments. Genotypes exhibiting less CID were shown to have a higher WUE, and CID was related to WUE. The higher WUE genotypes also exhibited differences in photosynthetic traits, especially in their stomatal behavior to restrict water loss. In terms of grain yield, very few differences were observed between the genotypes. Thermal images to estimate canopy temperature and sap flow sensors to estimate field water use provided excellent insight into differences among watering treatments and genotypes for transpiration rates. This research demonstrates, that in soybean, CID can be used as a screening tool to select for higher WUE, and higher WUE is likely a result of increased stomatal restrictions to prevent water loss during periods of drought stress. However, these genotypes exhibiting less transpiration showed minimal, if any grain yield reduction. Further, whole field imaging can also be utilized to identify higher WUE genotypes, and sap flow sensors can be expected to estimate water use in the field. Both resulting in reduced labor and more efficient time use.

Plant Responses to Salinity Under Elevated Atmospheric Concentrations of CO2

1992 ◽  
Vol 40 (5) ◽  
pp. 515 ◽  
Author(s):  
MC Ball ◽  
R Munns
Keyword(s):  
Water Use Efficiency ◽  
Elevated Co2 ◽  
Water Use ◽  
Water Loss ◽  
Salt Flux ◽  
Carbon Gain ◽  
Salt Balance ◽  
Salt Uptake ◽  
Use Efficiency ◽  
Atmospheric Concentrations

This review explores effects of elevated CO2 concentrations on growth in relation to water use and salt balance of halophytic and non-halophytic species. Under saline conditions, the uptake and distribution of sodium and chloride must be regulated to protect sensitive metabolic sites from salt toxicity. Salt-tolerant species exclude most of the salt from the transpiration stream, but the salt flux from a highly saline soil is still considerable. To maintain internal ion concentrations within physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt storage and/or salt export by either retranslocation or secretion from glands. Hence the balance between carbon gain and the expenditure of water in association with salt uptake is critical to leaf longevity under saline conditions. Indeed, one of the striking features of halophytic vegetation, such as mangroves, is the maintenance of high water use efficiencies coupled with relatively low rates of water loss and growth. These low evaporation rates are further reduced under elevated CO2 conditions. This, with increased growth, leads to even higher water use efficiency. Leaves of plants grown under elevated CO2 conditions might be expected to contain lower salt concentrations than those grown under ambient CO2 if salt uptake is coupled with water uptake. However, salt concentrations in shoot tissues are similar in plants grown under ambient and elevated CO2 conditions despite major differences in water use efficiency. This phenomenon occurs in C3 halophytes and in both C3 and C2 non-halophytes. These results imply shoot/root communication in regulation of the salt balance to adjust to environmental factors affecting the availability of water and ions at the roots (salinity) and those affecting carbon gain in relation to water loss at the leaves (atmospheric concentrations of water vapour and carbon dioxide).

Leaf characteristics, wood anatomy and hydraulic properties in tree species from contrasting habitats within upper Rio Negro forests in the Amazon region

2010 ◽  
Vol 26 (2) ◽  
pp. 215-226 ◽  
Author(s):  
M. A. Sobrado
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Water Loss ◽  
Tree Species ◽  
Mixed Forest ◽  
High Water ◽  
Hydraulic Characteristics ◽  
Use Efficiency ◽  
Species Specific

Abstract:Leaf blade physical and chemical characteristics, wood composition and anatomy, as well as long-term water-use efficiency and hydraulic characteristics of leaf-bearing terminal branches were assessed in tree species growing in contrasting forests of the Venezuelan Amazonas: mixed forest on oxisol soil and caatinga on podzol soil. Two upper-canopy tree species were selected in each forest, and three individuals per species were tagged for sampling. Leaf nitrogen isotopic signatures (δ15N) were negative and species-specific, which suggests that in species of both forest the N-cycle is closed, and that tree species can withdraw N from a variety of N-pools. Leaf construction costs, dry mass to leaf area ratio, thickness and sclerophylly index tended to increase in microhabitats with lower fertility and large water table fluctuations. The hydraulic characteristics and long-term water use are species-specific and related to the particular conditions of the habitat at the local scale. Ocotea aciphylla (mixed forest) with a combination of low δ13C and high hydraulic sufficiency may maintain high water loss without risk of xylem embolisms. By contrast, Micranda sprucei (slopes of the caatinga forest), had a combination of relatively high hydraulic sufficiency and the highest long-term water-use efficiency, which suggest that embolism risk would be avoided by water loss restriction. Assuming a warmer and drier climate in the future, the species with more conservative water transport and/or better stomatal control would be at lower risk of mortality.

scholarly journals Strategic Vision of Container Nursery Irrigation in the Next Ten Years

2004 ◽  
Vol 22 (2) ◽  
pp. 113-115 ◽  
Author(s):  
R.C. Beeson ◽  
M.A. Arnold ◽  
T.E. Bilderback ◽  
B. Bolusky ◽  
S. Chandler ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Irrigation Water ◽  
Irrigation Water Use Efficiency ◽  
Strategic Vision ◽  
Irrigation Water Use ◽  
Use Efficiency ◽  
The Cost ◽  
Irrigation Runoff ◽  
Container Nursery

Abstract Visions of the future for container nursery irrigation were collected from twelve nursery irrigation scientists, growers and nursery organization leaders. The amount of water available for nursery irrigation unanimously is forecasted to decline over the next decade. Along with declining availability, the cost of water for irrigation is predicted to increase substantially for most nurseries. Limited availability, higher direct cost, and irrigation runoff issues are projected to compel the container nursery industry to adopt procedures and technology that will increase irrigation water use efficiency. Evidence in support of these prognoses, current solutions and suggested options are discussed.

scholarly journals Heterologous Expression of Arabidopsis thaliana rty Gene in Strawberry (Fragaria × ananassa Duch.) Improves Drought Tolerance

2020 ◽  
Author(s):  
Maofu Li ◽  
Yuan Yang ◽  
Ali Raza ◽  
Shanshan Yin ◽  
Hua Wang ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Transgenic Plants ◽  
Drought Tolerance ◽  
Heterologous Expression ◽  
Water Use Efficiency ◽  
Water Use ◽  
Water Loss ◽  
Loss Rate ◽  
Water Loss Rate ◽  
Use Efficiency

Abstract Background: Strawberry (Fragaria × ananassa Duch.) is an important fruit crop worldwide. It was particularly sensitive to drought stress because of their fibrous and shallow root systems. Mutant rty of Arabidopsis thaliana ROOTY (RTY) results in increased endogenous auxin levels, more roots, and shoot growth. It is still unclear whether the rty gene improves stress tolerance in strawberry. Results: rty gene was isolated from Arabidopsis thaliana and placed under the control of the cauliflower mosaic virus (CaMV) 35S promoter in the pBI121-rty binary vector carrying the selectable marker of neomycin phosphotransferaseⅡ(NPTⅡ). Seven transgenic lines were confirmed by PCR and western blot analysis. Accumulations of IAA and ABA were significantly increased in the transgenic plants. The endogenous IAA contents were 46.5 ng g–1 and 66.0 ng g–1in control and transgenic plants respectively. The endogenous ABA contents in the control plant were 236.3 ng g–1 and in transgenic plants were 543.8 ng g–1. The production of adventitious roots and trichomes were enhanced in the transgenic plants. Furthermore, transcript levels of the genes including IAA and ABA biosynthetic, and stress-responsive genes, were higher in the transgenic plants than in the control plants under drought conditions. Water use efficiency and a reduced water loss rate were enhanced in the transgenic strawberry plants. Additionally, peroxidase and catalase activities were significantly higher in the transgenic plants than in the control plants. The experiment results revealed a novel function for rty related to ABA and drought responses. Conclusions: The rty gene improved hormone-mediated drought tolerance in transgenic strawberry. The heterologous expression of rty in strawberry improved drought tolerance by promoting auxin and ABA accumulation. These phytohormones together brought about various physiological changes that improved drought tolerance via increased root production, trichome density, and stomatal closure. Our results suggested that a transgenic approach can be used to overcome the inherent trade-off between plant growth and drought tolerance by enhancing water use efficiency and reducing water loss rate under water shortage conditions.

Water Use Efficiency as a Method for Predicting Water Use by Weeds

1996 ◽  
Vol 10 (1) ◽  
pp. 153-155 ◽  
Author(s):  
Robert F. Norris
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Production Costs ◽  
Weed Growth ◽  
Irrigated Crops ◽  
Use Efficiency ◽  
The Cost ◽  
Agriculture Water

Water use by weeds is one type of loss that contributes to the cost of weeds to agriculture. Water use efficiency provides a mechanism by which water use by weeds can be estimated. Uncontrolled weed growth could result in estimated irrigation costs exceeding $50.00/ha. Weeds like barnyardgrass at threshold densities in irrigated crops like sugarbeet or tomato are estimated to increase production costs by about $20.00/ha depending on water cost.

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