Variation of gross primary production, evapotranspiration and water use efficiency for global croplands

2020 ◽  
Vol 287 ◽  
pp. 107935
Author(s):  
Zhipin Ai ◽  
Qinxue Wang ◽  
Yonghui Yang ◽  
Kiril Manevski ◽  
Shuang Yi ◽  
...  
Keyword(s):  
Primary Production ◽  
Water Use Efficiency ◽  
Water Use ◽  
Gross Primary Production ◽  
Use Efficiency

scholarly journals Primary production in forests and grasslands of China: contrasting environmental responses of light- and water-use efficiency models

2012 ◽  
Vol 9 (4) ◽  
pp. 4285-4321 ◽  
Author(s):  
H. Wang ◽  
I. C. Prentice ◽  
J. Ni
Keyword(s):  
Primary Production ◽  
Water Use Efficiency ◽  
Water Use ◽  
South China ◽  
Net Primary Production ◽  
Gross Primary Production ◽  
Stomatal Closure ◽  
Co2 Response ◽  
Data Set ◽  
Use Efficiency

Abstract. An extensive data set on net primary production (NPP) in China's forests is analysed with two semi-empirical models based on the light use efficiency (LUE) and water use efficiency (WUE) concepts, respectively. Results are shown to be broadly consistent with other data sets (grassland above-ground NPP; globally extrapolated gross primary production, GPP) and published analyses. But although both models describe the data about equally well, they predict notably different responses to [CO2] and temperature. These are illustrated by sensitivity tests in which [CO2] is kept constant or doubled, temperatures are kept constant or increased by 3.5 K, and precipitation is changed by ±10%. Precipitation changes elicit similar responses in both models. The [CO2] response of the WUE model is much larger but is probably an overestimate for dense vegetation as it assumes no increase in runoff; while the [CO2] response of the LUE model is probably too small for sparse vegetation as it assumes no increase in vegetation cover. In the LUE model warming reduces total NPP with the strongest effect in South China, where the growing season cannot be further extended. In the WUE model warming increases total NPP, again with the strongest effect in South China, where abundant water supply precludes stomatal closure. The qualitative differences between the two formulations illustrate potential causes of the large differences (even in sign) in the global NPP response of dynamic global vegetation models to [CO2] and climate change. As it is not clear which response is more realistic, the issue needs to be resolved by observation and experiment.

The role of Evapotranspiration and Water Use Efficiency in Agriculture in Portugal

2020 ◽  
Author(s):  
José Vaz ◽  
Célia M. Gouveia ◽  
Isabel F. Trigo
Keyword(s):  
Climate Variability ◽  
Primary Production ◽  
Water Use Efficiency ◽  
Water Use ◽  
Reference Evapotranspiration ◽  
Gross Primary Production ◽  
Growth Monitoring ◽  
Climate Variability And Change ◽  
Wine Production ◽  
Use Efficiency

<p>Understanding climate variability and change and its impacts on natural systems is becoming more and more important as changes in earth surface condition near surface air temperature and precipitation. Over Portugal, the observed warming trends have been found to be asymmetric with respect to seasonal and diurnal cycles, with greatest warming occurring for the minimum temperature and during winter and spring. These observed trends exert strong influences on agriculture systems, affecting production viability through changes in winter hardening, frost occurrence, growing season lengths and heat accumulation for ripening potential.</p><p>Remote sensing technology has been developing steadily and its products can provide many applications in agriculture, namely crop identification, crop growth monitoring and yield prediction. Recently the LSA SAF team set up a strategy to generate long term data records from Meteosat Second Generation satellite series (2004 to present), releasing Land Surface Temperature (LST), Reference Evapotranspiration (ETREF) and Vegetation parameters (FAPAR, LAI and FVC) using a stable set of input data and algorithm, which would be suitable for climate variability and change detection studies. On the other hand, a new product to characterize the ecosystem processes, the Gross Primary Production (GPP), is under production since 2018.</p><p>In this work we propose to computed Water Use Efficiency (WUE), as the ratio between Gross Primary Production (GPP) and Reference Evapotranspiration (ETREF), using LSA-SAF Products. WUE translates the exchanges of carbon and water gross fluxes, between natural ecosystem and the atmosphere, allowing to monitor the adaptability of the ecosystems to climate change. The role played by Evapotranspiration and Water Use Efficiency for different crops in Portugal is evaluated, namely on Wine Production for Douro Region. Results for 2018 and 2019 highlights the vulnerability of the different sectors of Douro Region to dry and wet conditions, namely helping to analyze the impact of droughts on Douro wine production.</p><p>Acknowledgements: This study was performed within the framework of the LSA-SAF, co-funded by EUMETSAT This work was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under projects CLMALERT (ERA4CS/0005/2016).</p>

scholarly journals Primary production in forests and grasslands of China: contrasting environmental responses of light- and water-use efficiency models

2012 ◽  
Vol 9 (11) ◽  
pp. 4689-4705 ◽  
Author(s):  
H. Wang ◽  
I. C. Prentice ◽  
J. Ni
Keyword(s):  
Primary Production ◽  
Water Use Efficiency ◽  
Water Use ◽  
Net Primary Production ◽  
Upper And Lower Bounds ◽  
Co2 Response ◽  
Data Set ◽  
Use Efficiency ◽  
Vegetation Models ◽  
Environmental Responses

Abstract. An extensive data set on net primary production (NPP) in China's forests is analysed with the help of two simple theoretically derived models based on the light use efficiency (LUE) and water use efficiency (WUE) concepts, respectively. The two models describe the data equally well, but their implied responses to [CO2] and temperature differ substantially. These responses are illustrated by sensitivity tests in which [CO2] is kept constant or doubled, temperatures are kept constant or increased by 3.5 K, and precipitation is changed by ±10%. Precipitation changes elicit similar responses in both models. But NPP in South China, especially, is reduced by warming in the LUE model, whereas it is increased in the WUE model. The [CO2] response of the WUE model is much larger than that of the LUE model. It is argued that the two models provide upper and lower bounds for this response, with the LUE model more realistic for forests. The differences between the two models illustrate some potential causes of the large differences (even in sign) in the global NPP response of different global vegetation models to temperature and [CO2].

scholarly journals Drone-Based Hyperspectral and Thermal Imagery for Quantifying Upland Rice Growth and Water Use Efficiency After Biochar Application

2021 ◽  
Author(s):  
Hongxiao Jin ◽  
Christian Josef Köppl ◽  
Benjamin M. C. Fischer ◽  
Johanna Rojas-Conejo ◽  
Mark S. Johnson ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Upland Rice ◽  
Gross Primary Production ◽  
Physical Models ◽  
Control Group ◽  
Transfer Model ◽  
Thermal Imagery ◽  
Rice Growth ◽  
Use Efficiency

Low-cost miniature hyperspectral and thermal cameras onboard lightweight unmanned aerial vehicles (UAV) bring new opportunities for monitoring land surface variables at unprecedented fine spatial resolution with acceptable accuracy. This research applies hyperspectral and thermal imagery from a drone to quantify upland rice growth and water use efficiency (WUE) after biochar application in a Costa Rican dry region. The field flights were conducted over two experimental groups with bamboo biochar and sugarcane biochar amendments and one control group without biochar application. Rice canopy biophysical variables were estimated by inversion of a canopy radiative transfer model on hyperspectral reflectance. Variations in gross primary production (GPP) and WUE across treatments were estimated from the normalized difference vegetation index (NDVI), canopy chlorophyll content (CCC), and evapotranspiration. We found that GPP was increased by 41.9±3.4 % when using bamboo biochar and 17.5±3.4 % when using sugarcane biochar, which was probably due to higher soil moisture in the biochar-amended plots and led to significantly higher WUE by 40.8±3.5 % in bamboo biochar and 13.4±3.5 % in sugarcane biochar. This study demonstrated the use of hyperspectral and thermal imagery from drone to provide indicators for quantifying biochar effects on tropical dry cropland by integrating with ground point samples and physical models.

scholarly journals Water use efficiency of net primary production in global terrestrial ecosystems

2015 ◽  
Vol 124 (5) ◽  
pp. 921-931 ◽  
Author(s):  
Lei Xia ◽  
Fei Wang ◽  
Xingmin Mu ◽  
Kai Jin ◽  
Wenyi Sun ◽  
...  
Keyword(s):  
Primary Production ◽  
Water Use Efficiency ◽  
Water Use ◽  
Net Primary Production ◽  
Terrestrial Ecosystems ◽  
Use Efficiency

scholarly journals Water-Use Efficiency of the Terrestrial Biosphere: A Model Analysis Focusing on Interactions between the Global Carbon and Water Cycles

2012 ◽  
Vol 13 (2) ◽  
pp. 681-694 ◽  
Author(s):  
Akihiko Ito ◽  
Motoko Inatomi
Keyword(s):  
Carbon Cycle ◽  
Primary Production ◽  
Water Use Efficiency ◽  
Water Use ◽  
Ecosystem Management ◽  
Water Budget ◽  
Terrestrial Ecosystems ◽  
Terrestrial Biosphere ◽  
Use Efficiency ◽  
Water Cycles

Abstract Carbon and water cycles are intimately coupled in terrestrial ecosystems, and water-use efficiency (WUE; carbon gain at the expense of unit water loss) is one of the key parameters of ecohydrology and ecosystem management. In this study, the carbon cycle and water budget of terrestrial ecosystems were simulated using a process-based ecosystem model called Vegetation Integrative Simulator for Trace Gases (VISIT), and WUE was evaluated: WUEC, defined as gross primary production (GPP) divided by transpiration; and WUES, defined as net primary production (NPP) divided by actual evapotranspiration. Total annual WUEC and WUES of the terrestrial biosphere were estimated as 8.0 and 0.92 g C kg−1 H2O, respectively, for the period 1995–2004. Spatially, WUEC and WUES were only weakly correlated. WUES ranged from <0.2 g C kg−1 H2O in arid ecosystems to >1.5 g C kg−1 H2O in boreal and alpine ecosystems. The historical simulation implied that biospheric WUE increased from 1901 to 2005 (WUEC, +7%; WUES, +12%) mainly as a result of the augmentation of productivity in parallel with the atmospheric carbon dioxide increase. Country-based analyses indicated that total NPP is largely determined by water availability, and human appropriation of NPP is also related to water resources to a considerable extent. These results have implications for 1) responses of the carbon cycle to the anticipated global hydrological changes, 2) responses of the water budget to changes in the terrestrial carbon cycle, and 3) ecosystem management based on optimized resource use.

Capability of maize water use efficiency estimation at field scale using Sentinel-2 data

2020 ◽  
Author(s):  
Zonghan Ma ◽  
Bingfang Wu ◽  
Nana Yan ◽  
Weiwei Zhu
Keyword(s):  
Water Management ◽  
High Resolution ◽  
Water Use Efficiency ◽  
Water Use ◽  
Water Consumption ◽  
Precision Agriculture ◽  
Gross Primary Production ◽  
Field Scale ◽  
Use Efficiency ◽  
Sentinel 2

<p>Water use efficiency (WUE) is defined as the ratio between gross primary production (GPP) and evapotranspiration (ET) at ecosystem scale, which can help understand the mechanism between water consumption and crop production in guiding field water management. Water consumption control is important in precision agriculture development. Mapping WUE at field scale using remote sensing data could provide crop water use status at high resolution and acquire the WUE spatial distribution. In this study we proposed a method to estimate field-scale maize WUE with Sentienl-2 data. The GPP of maize is estimated by a light use efficiency model with RS observed albedo, sunshine radiation, fraction of photosynthetically active radiation (fpar) fitted using in site observation. Maize ET is modelled using FAO-PM model with crop coefficient simulated using vegetation indexes acquired from Sentinel-2 bands. We compared the GPP, ET and final WUE estimation with eddy covariance (EC) observations in a maize field of North China Plain where water scarcity is a main limit factor of crop development. Comparation results show a high correlation between in site observation and modelled results. Combining the phenology development of maize, the temporal characteristics of maize WUE change is associated with phenology. WUE was low after sowing, then increased during Elongation stage. Maize WUE peaked at Heading and Grouting period and decreased in Maturation stage. Our WUE estimation method with high resolution could guide adopting various irrigation strategies based on different WUE conditions at field scale. This research could help shed light on the future WUE development under climate change background and improve our knowledge of precise water management.</p>

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