Quantifying plant transpiration and canopy conductance using eddy flux data: An underlying water use efficiency method

2019 ◽  
Vol 271 ◽  
pp. 375-384 ◽  
Author(s):  
Yan Bai ◽  
Xiaoyan Li ◽  
Sha Zhou ◽  
Xiaofan Yang ◽  
Kailiang Yu ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Canopy Conductance ◽  
Eddy Flux ◽  
Plant Transpiration ◽  
Flux Data ◽  
Use Efficiency

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.

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 Canopy Gas Exchange and Water Use Efficiency of ‘Empire’ Apple in Response to Particle Film, Irrigation, and Microclimatic Factors

2010 ◽  
Vol 135 (1) ◽  
pp. 25-32 ◽  
Author(s):  
D. Michael Glenn
Keyword(s):  
Gas Exchange ◽  
Water Use Efficiency ◽  
Water Use ◽  
Growing Season ◽  
Canopy Conductance ◽  
Supplemental Irrigation ◽  
Isotope Discrimination ◽  
Wide Range ◽  
Use Efficiency ◽  
Seasonal Water Use

This study examined the interaction between a reflective particle film and water use efficiency (WUE) response of irrigated and non-irrigated apple trees (Malus ×domestica) over a wide range of environmental conditions. The objectives were to measure isotopic discrimination (Δ13C and δ18O), specific gas exchange, and WUE response of ‘Empire’ apple treated with a reflective particle film (PF), with and without supplemental irrigation, compared with an untreated control, with and without supplemental irrigation, over a range of leaf area indices (LAI), seasonal evapotranspiration (ETo), and vapor pressure deficits (VPD) to determine the mechanisms of action affecting WUE in apple. Short-term whole canopy gas exchange studies and isotope discrimination analysis were used to test the hypothesis that WUE was modified by the use of a PF. In whole canopy gas exchange studies, carbon assimilation (A) and transpiration tended to increase, and WUE and canopy conductance tended to decrease, with VPD within each LAI class from 2 to 6. For VPD > 1 kPa, the PF irrigated treatment consistently had the greatest WUE and other treatments were intermediate for LAI of 2 to 4. The PF irrigated and non-irrigated treatments had greater WUE than the control irrigated and non-irrigated treatments for VPD ≤ 2 kPa and there were no treatment effects for VPD > 2 kPa in the LAI range of 4 to 6. The PF non-irrigated was equivalent to the control non-irrigated treatment at VPD of 1 to 3 kPa, but was significantly lower at VPD of 3 to 4 kPa. PF irrigated and non-irrigated treatments had the greatest carbon isotope discrimination (Δ13C), the control non-irrigated treatment had the lowest Δ13C, and the control-irrigated treatment was intermediate. Oxygen isotope enrichment (δ18O) was positively correlated with the mean growing season VPD and mean growing season evapotranspiration. Δ13C was significantly and positively correlated with δ18O. Seasonal WUE was negatively correlated with Δ13C and there was an interaction with LAI. The seasonal water use of apple is better evaluated with stable isotope discrimination integrating seasonal variation rather that the use of whole canopy gas exchange measurements that measure WUE for brief periods of time. Δ13C was an accurate measurement of apple WUE and indicated that the PF irrigated treatment had the greatest Δ13C and so the lowest WUE compared with the control non-irrigated treatment at LAI from 4 to 6. The reduced WUE of the PF irrigated treatment compared with the control non-irrigated treatment is likely due to increased gS from lower canopy temperature and increased canopy photosynthetically active radiation diffusion that drove increased A. δ18O was an indicator of seasonal water use over six growing seasons due to its high correlation with ETo. In ‘Empire’ apple, A can be increased with PF and irrigation treatments, but at the cost of decreased WUE.

scholarly journals Interannual and seasonal variability of water use efficiency in a tropical rainforest: Results from a 9 year eddy flux time series

2015 ◽  
Vol 120 (2) ◽  
pp. 464-479 ◽  
Author(s):  
Zheng-Hong Tan ◽  
Yi-Ping Zhang ◽  
Xiao-Bao Deng ◽  
Qing-Hai Song ◽  
Wen-Jie Liu ◽  
...  
Keyword(s):  
Time Series ◽  
Water Use Efficiency ◽  
Water Use ◽  
Seasonal Variability ◽  
Tropical Rainforest ◽  
Eddy Flux ◽  
Use Efficiency

Increasing intrinsic water-use efficiency over the past 160 years does not stimulate tree growth in southeastern China

2018 ◽  
Vol 76 (2) ◽  
pp. 115-130 ◽  
Author(s):  
G Guo ◽  
K Fang ◽  
J Li ◽  
HW Linderholm ◽  
D Li ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Tree Growth ◽  
Southeastern China ◽  
The Past ◽  
Intrinsic Water Use Efficiency ◽  
Use Efficiency

A comparative appraisal of urea super granule application in raised bed and prilled urea application in conventional planting for transplanted boro rice (Oryza sativa)

2016 ◽  
Vol 6 (1) ◽  
pp. 822-832
Author(s):  
Halim Mahmud Bhuyan ◽  
Most. Razina Ferdousi ◽  
Mohammad Toufiq Iqbal ◽  
Ahmed Khairul Hasan
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
N Fertilizer ◽  
Deep Placement ◽  
Prilled Urea ◽  
Planting Methods ◽  
Weed Infestation ◽  
Use Efficiency ◽  
Raised Bed ◽  
Boro Rice

Utilization of urea super granule (USG) with raised bed cultivation system for transplanted boro (winter, irrigated) rice production is a major concern now days. A field experiment was conducted in the chuadanga district of Bangladesh to compare the two cultivation methods: deep placement of USG on raised bed with boro rice, and prilled urea (PU) broadcasting in conventional planting. Results showed that USG in raised bed planting increased grain yields of transplanted boro rice by up to 18.18% over PU in conventional planting. Deep placement of USG in raised bed planting increased the number of panicle m-2, number of grains panicle-1 and 1000-grains weight of boro rice than the PU in conventional planting. Better plant growth was observed by deep placement of USG in raised bed planting compared to PU in conventional planting. Sterility percentage and weed infestation were lower on USG in raised bed planting compared to the PU in conventional planting methods. Forty seven percent irrigation water and application time could be saved by USG in raised bed planting than PU in conventional planting. Deep placement of USG in bed saved N fertilizer consumption over conventional planting. Water use efficiency for grain and biomass production was higher with deep placement of USG in bed planting than the PU broadcasting in conventional planting methods. Similarly, agronomic efficiency of N fertilizer by USG in bed planting was significantly higher than the PU broadcasting in conventional planting. This study concluded that deep placement of USG in raised bed planting for transplanted boro rice is a new approach to achieve fertilizer and water use efficiency as well as higher yield and less water input compared to existing agronomic practices in Bangladesh.

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