scholarly journals Deriving a light use efficiency estimation algorithm using in situ hyperspectral and eddy covariance measurements for a maize canopy in Northeast China

2017 ◽  
Vol 7 (13) ◽  
pp. 4735-4744 ◽  
Author(s):  
Feng Zhang ◽  
Guangsheng Zhou
Keyword(s):  
Eddy Covariance ◽  
Northeast China ◽  
Estimation Algorithm ◽  
Light Use Efficiency ◽  
Efficiency Estimation ◽  
Eddy Covariance Measurements ◽  
Use Efficiency

scholarly journals Technical note: Estimating light-use efficiency of benthic habitats using underwater O<sub>2</sub> eddy covariance

2020 ◽  
Vol 17 (16) ◽  
pp. 4343-4353
Author(s):  
Karl M. Attard ◽  
Ronnie N. Glud
Keyword(s):  
Primary Production ◽  
Eddy Covariance ◽  
Technological Development ◽  
Gross Primary Production ◽  
Technical Note ◽  
Light Use Efficiency ◽  
In Situ Conditions ◽  
Use Efficiency ◽  
Habitat Scale

Abstract. Light-use efficiency defines the ability of primary producers to convert sunlight energy to primary production and is computed as the ratio between the gross primary production and the intercepted photosynthetic active radiation. While this measure has been applied broadly within terrestrial ecology to investigate habitat resource-use efficiency, it remains underused within the aquatic realm. This report provides a conceptual framework to compute hourly and daily light-use efficiency using underwater O2 eddy covariance, a recent technological development that produces habitat-scale rates of primary production under unaltered in situ conditions. The analysis, tested on two benthic flux datasets, documents that hourly light-use efficiency may approach the theoretical limit of 0.125 O2 per photon under low-light conditions, but it decreases rapidly towards the middle of the day and is typically 10-fold lower on a 24 h basis. Overall, light-use efficiency provides a useful measure of habitat functioning and facilitates site comparison in time and space.

scholarly journals Simulating Spatiotemporal Dynamics of Sichuan Grassland Net Primary Productivity Using the CASA Model and In Situ Observations

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Chuanjiang Tang ◽  
Xinyu Fu ◽  
Dong Jiang ◽  
Jingying Fu ◽  
Xinyue Zhang ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Net Primary Productivity ◽  
Alpine Meadow ◽  
Growth Period ◽  
Temporal Variations ◽  
Light Use Efficiency ◽  
Important Indicator ◽  
Casa Model ◽  
Use Efficiency

Net primary productivity (NPP) is an important indicator for grassland resource management and sustainable development. In this paper, the NPP of Sichuan grasslands was estimated by the Carnegie-Ames-Stanford Approach (CASA) model. The results were validated with in situ data. The overall precision reached 70%; alpine meadow had the highest precision at greater than 75%, among the three types of grasslands validated. The spatial and temporal variations of Sichuan grasslands were analyzed. The absorbed photosynthetic active radiation (APAR), light use efficiency (ε), and NPP of Sichuan grasslands peaked in August, which was a vigorous growth period during 2011. High values of APAR existed in the southwest regions in altitudes from 2000 m to 4000 m. Light use efficiency (ε) varied in the different types of grasslands. The Sichuan grassland NPP was mainly distributed in the region of 3000–5000 m altitude. The NPP of alpine meadow accounted for 50% of the total NPP of Sichuan grasslands.

Mapping the aerodynamic roughness of the Greenland ice sheet surface using ICESat-2

2021 ◽  
Author(s):  
Maurice van Tiggelen ◽  
Paul C.J.P. Smeets ◽  
Carleen H. Reijmer ◽  
Bert Wouters ◽  
Jakob F. Steiner ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Elevation ◽  
Spatiotemporal Variability ◽  
Atmospheric Models ◽  
Laser Altimeter ◽  
Eddy Covariance Measurements ◽  
Aerodynamic Roughness

&lt;p&gt;The roughness of a natural surface is an important parameter in atmospheric models, as it determines the intensity of turbulent transfer between the atmosphere and the surface. Unfortunately, this parameter is often poorly known, especially in remote areas where neither high-resolution elevation models nor eddy-covariance measurements are available.&lt;/p&gt;&lt;p&gt;In this study, we take advantage of the measurements of the ICESat-2 satellite laser altimeter. We use the geolocated photons product (ATL03) to retrieve a 1-m resolution surface elevation product over the K-transect (West Greenland ice sheet). In combination with a bulk drag partitioning model, the retrieved surface elevation is used to estimate the aerodynamic roughness length (z&lt;sub&gt;0m&lt;/sub&gt;) of the surface.&lt;/p&gt;&lt;p&gt;We demonstrate the high precision of the retrieved ICESat-2 elevation using co-located UAV photogrammetry, and then evaluate the modelled aerodynamic roughness against multiple in situ eddy-covariance observations. The results point out the importance to use a bulk drag model over a more empirical formulation.&lt;/p&gt;&lt;p&gt;The currently available ATL03 geolocated photons are used to map the aerodynamic roughness along the K-transect (2018-2020). We find a considerable spatiotemporal variability in z&lt;sub&gt;0m&lt;/sub&gt;, ranging between 10&lt;sup&gt;&amp;#8722;4&lt;/sup&gt; m for a smooth snow surface to more than 10&lt;sup&gt;&amp;#8722;1&lt;/sup&gt; m for rough crevassed areas, which confirms the need to incorporate a variable aerodynamic roughness in atmospheric models over ice sheets.&lt;/p&gt;

scholarly journals Assessing the ability of three land ecosystem models to simulate gross carbon uptake of forests from boreal to Mediterranean climate in Europe

2007 ◽  
Vol 4 (4) ◽  
pp. 647-656 ◽  
Author(s):  
M. Jung ◽  
G. Le Maire ◽  
S. Zaehle ◽  
S. Luyssaert ◽  
M. Vetter ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Model Comparison ◽  
Gross Primary Production ◽  
Radiation Use Efficiency ◽  
Mediterranean Forests ◽  
Area Index ◽  
Limited Region ◽  
Eddy Covariance Measurements ◽  
Use Efficiency ◽  
Radiation Use

Abstract. Three terrestrial biosphere models (LPJ, Orchidee, Biome-BGC) were evaluated with respect to their ability to simulate large-scale climate related trends in gross primary production (GPP) across European forests. Simulated GPP and leaf area index (LAI) were compared with GPP estimates based on flux separated eddy covariance measurements of net ecosystem exchange and LAI measurements along a temperature gradient ranging from the boreal to the Mediterranean region. The three models capture qualitatively the pattern suggested by the site data: an increase in GPP from boreal to temperate and a subsequent decline from temperate to Mediterranean climates. The models consistently predict higher GPP for boreal and lower GPP for Mediterranean forests. Based on a decomposition of GPP into absorbed photosynthetic active radiation (APAR) and radiation use efficiency (RUE), the overestimation of GPP for the boreal coniferous forests appears to be primarily related to too high simulated LAI - and thus light absorption (APAR) – rather than too high radiation use efficiency. We cannot attribute the tendency of the models to underestimate GPP in the water limited region to model structural deficiencies with confidence. A likely dry bias of the input meteorological data in southern Europe may create this pattern. On average, the models compare similarly well to the site GPP data (RMSE of ~30% or 420 gC/m2/yr) but differences are apparent for different ecosystem types. In terms of absolute values, we find the agreement between site based GPP estimates and simulations acceptable when we consider uncertainties about the accuracy in model drivers, a potential representation bias of the eddy covariance sites, and uncertainties related to the method of deriving GPP from eddy covariance measurements data. Continental to global data-model comparison studies should be fostered in the future since they are necessary to identify consistent model bias along environmental gradients.

scholarly journals Remote sensing of ecosystem light use efficiency with MODIS-based PRI

2011 ◽  
Vol 8 (1) ◽  
pp. 189-202 ◽  
Author(s):  
A. Goerner ◽  
M. Reichstein ◽  
E. Tomelleri ◽  
N. Hanan ◽  
S. Rambal ◽  
...  
Keyword(s):  
Meteorological Data ◽  
Vapour Pressure Deficit ◽  
Ground Truth ◽  
Light Use Efficiency ◽  
Wide Range ◽  
Evaluation Exercise ◽  
Use Efficiency ◽  
Study Sites ◽  
Absorbed Photosynthetically Active Radiation

Abstract. Several studies sustained the possibility that a photochemical reflectance index (PRI) directly obtained from satellite data can be used as a proxy for ecosystem light use efficiency (LUE) in diagnostic models of gross primary productivity. This modelling approach would avoid the complications that are involved in using meteorological data as constraints for a fixed maximum LUE. However, no unifying model predicting LUE across climate zones and time based on MODIS PRI has been published to date. In this study, we evaluate the effectiveness with which MODIS-based PRI can be used to estimate ecosystem light use efficiency at study sites of different plant functional types and vegetation densities. Our objective is to examine if known limitations such as dependence on viewing and illumination geometry can be overcome and a single PRI-based model of LUE (i.e. based on the same reference band) can be applied under a wide range of conditions. Furthermore, we were interested in the effect of using different faPAR (fraction of absorbed photosynthetically active radiation) products on the in-situ LUE used as ground truth and thus on the whole evaluation exercise. We found that estimating LUE at site-level based on PRI reduces uncertainty compared to the approaches relying on a maximum LUE reduced by minimum temperature and vapour pressure deficit. Despite the advantages of using PRI to estimate LUE at site-level, we could not establish an universally applicable light use efficiency model based on MODIS PRI. Models that were optimised for a pool of data from several sites did not perform well.

scholarly journals Estimation of Terrestrial Global Gross Primary Production (GPP) with Satellite Data-Driven Models and Eddy Covariance Flux Data

2018 ◽  
Vol 10 (9) ◽  
pp. 1346 ◽  
Author(s):  
Joanna Joiner ◽  
Yasuko Yoshida ◽  
Yao Zhang ◽  
Gregory Duveiller ◽  
Martin Jung ◽  
...  
Keyword(s):  
Primary Production ◽  
Eddy Covariance ◽  
Satellite Data ◽  
Gross Primary Production ◽  
Satellite Observation ◽  
Data Driven ◽  
Spatial And Temporal Variability ◽  
Light Use Efficiency ◽  
High Productivity ◽  
Use Efficiency

We estimate global terrestrial gross primary production (GPP) based on models that use satellite data within a simplified light-use efficiency framework that does not rely upon other meteorological inputs. Satellite-based geometry-adjusted reflectances are from the MODerate-resolution Imaging Spectroradiometer (MODIS) and provide information about vegetation structure and chlorophyll content at both high temporal (daily to monthly) and spatial (∼1 km) resolution. We use satellite-derived solar-induced fluorescence (SIF) to identify regions of high productivity crops and also evaluate the use of downscaled SIF to estimate GPP. We calibrate a set of our satellite-based models with GPP estimates from a subset of distributed eddy covariance flux towers (FLUXNET 2015). The results of the trained models are evaluated using an independent subset of FLUXNET 2015 GPP data. We show that variations in light-use efficiency (LUE) with incident PAR are important and can be easily incorporated into the models. Unlike many LUE-based models, our satellite-based GPP estimates do not use an explicit parameterization of LUE that reduces its value from the potential maximum under limiting conditions such as temperature and water stress. Even without the parameterized downward regulation, our simplified models are shown to perform as well as or better than state-of-the-art satellite data-driven products that incorporate such parameterizations. A significant fraction of both spatial and temporal variability in GPP across plant functional types can be accounted for using our satellite-based models. Our results provide an annual GPP value of ∼140 Pg C year - 1 for 2007 that is within the range of a compilation of observation-based, model, and hybrid results, but is higher than some previous satellite observation-based estimates.

scholarly journals Assessing the ability of three land ecosystem models to simulate gross carbon uptake of forests from boreal to Mediterranean climate in Europe

2007 ◽  
Vol 4 (2) ◽  
pp. 1353-1375 ◽  
Author(s):  
M. Jung ◽  
G. Le Maire ◽  
S. Zaehle ◽  
S. Luyssaert ◽  
M. Vetter ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Radiation Use Efficiency ◽  
Mean Annual Temperature ◽  
Mediterranean Forests ◽  
Area Index ◽  
Eddy Covariance Measurements ◽  
Use Efficiency ◽  
Radiation Use

Abstract. We evaluate three terrestrial biosphere models (LPJ, Orchidee, Biome-BGC) with respect to their capacity to simulate climate related trends in gross primary production (GPP) of forests in Europe. We compare simulated GPP and leaf area index (LAI) with GPP estimates based on flux separated eddy covariance measurements of net ecosystem exchange (NEE) and LAI measurements along a gradient in mean annual temperature from the boreal to the Mediterranean.The three models capture qualitatively the pattern suggested by the site data: an increase in GPP from boreal to temperate and a subsequent decline from temperate to Mediterranean climates. The models consistently predict higher GPP for boreal and lower GPP for Mediterranean forests. Based on a decomposition of GPP into absorbed photosynthetic active radiation (APAR) and radiation use efficiency (RUE), the overestimation of GPP for the boreal zone appears to be primarily related to too high simulated LAI - and thus light absorption (APAR) – rather than too high radiation use efficiency. On average, the models compare similarly well to the site GPP data (RMSE of ~30% or 420 gC/m2/yr) but differences are apparent for different ecosystem types. Given uncertainties about the accuracy in model drivers, a potential representation bias of the eddy covariance sites, and uncertainties related to the method of deriving GPP from eddy covariance measurements data, we find the agreement between site data and simulations acceptable, providing confidence in simulations of GPP for European forests.

scholarly journals Modeling light use efficiency in a subtropical mangrove forest equipped with CO<sub>2</sub> eddy covariance

2013 ◽  
Vol 10 (3) ◽  
pp. 2145-2158 ◽  
Author(s):  
J. G. Barr ◽  
V. Engel ◽  
J. D. Fuentes ◽  
D. O. Fuller ◽  
H. Kwon
Keyword(s):  
Eddy Covariance ◽  
Environmental Conditions ◽  
Mangrove Forest ◽  
Environmental Drivers ◽  
Model Parameters ◽  
Co2 Uptake ◽  
Light Use Efficiency ◽  
Co2 Fluxes ◽  
Use Efficiency ◽  
Reflectance Data

Abstract. Despite the importance of mangrove ecosystems in the global carbon budget, the relationships between environmental drivers and carbon dynamics in these forests remain poorly understood. This limited understanding is partly a result of the challenges associated with in situ flux studies. Tower-based CO2 eddy covariance (EC) systems are installed in only a few mangrove forests worldwide, and the longest EC record from the Florida Everglades contains less than 9 years of observations. A primary goal of the present study was to develop a methodology to estimate canopy-scale photosynthetic light use efficiency in this forest. These tower-based observations represent a basis for associating CO2 fluxes with canopy light use properties, and thus provide the means for utilizing satellite-based reflectance data for larger scale investigations. We present a model for mangrove canopy light use efficiency utilizing the enhanced green vegetation index (EVI) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) that is capable of predicting changes in mangrove forest CO2 fluxes caused by a hurricane disturbance and changes in regional environmental conditions, including temperature and salinity. Model parameters are solved for in a Bayesian framework. The model structure requires estimates of ecosystem respiration (RE), and we present the first ever tower-based estimates of mangrove forest RE derived from nighttime CO2 fluxes. Our investigation is also the first to show the effects of salinity on mangrove forest CO2 uptake, which declines 5% per each 10 parts per thousand (ppt) increase in salinity. Light use efficiency in this forest declines with increasing daily photosynthetic active radiation, which is an important departure from the assumption of constant light use efficiency typically applied in satellite-driven models. The model developed here provides a framework for estimating CO2 uptake by these forests from reflectance data and information about environmental conditions.

Terrestrial CO2 Fluxes, Concentrations, Sources and Budget in Northeast China: Observational and Modeling Studies

2020 ◽  
Author(s):  
Xiaolan Li ◽  
Xiao-Ming Hu ◽  
Changjie Cai ◽  
Qingyu Jia ◽  
Yao Zhang ◽  
...  
Keyword(s):  
Land Surface ◽  
Northeast China ◽  
Ecosystem Respiration ◽  
Mixed Forest ◽  
Net Ecosystem Exchange ◽  
Growth Period ◽  
Rice Paddy ◽  
Light Use Efficiency ◽  
Maximum Light ◽  
Use Efficiency

&lt;p&gt;CO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;fluxes and concentrations are not well understood in Northeast China, where dominant land surface types are mixed forest and cropland. &amp;#160;Here, we analyzed the CO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;fluxes and concentrations using Eddy Covariance&amp;#160;(EC)&amp;#160;measurements, satellite observations, and the Weather Research and Forecasting model coupled with the Vegetation Photosynthesis and Respiration Model (WRF-VPRM). &amp;#160;We also used WRF-VPRM outputs to examine CO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;transport/dispersion, and to quantify the biogenic&amp;#160;and anthropogenic contributions to atmospheric&amp;#160;CO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;concentrations. &amp;#160;Finally, we investigated the uncertainties&amp;#160;of simulating&amp;#160;CO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;fluxes&amp;#160;related to&amp;#160;four VPRM parameters (including&amp;#160;maximum light use efficiency,&amp;#160;photosynthetically active radiation half-saturation value, and two&amp;#160;respiration parameters) using offline ensemble simulations with&amp;#160;randomly selected&amp;#160;parameter values.&amp;#160;&amp;#160;The results indicated that&amp;#160;mixed forests&amp;#160;acted as a larger CO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;source&amp;#160;and sink than rice paddies&amp;#160;on average in 2016 due to a longer growth period and stronger ecosystem respiration, although the minimum EC-measured daily mean net ecosystem exchange (NEE) was smaller at rice paddy&amp;#160;(-10 &amp;#956;mol m&lt;sup&gt;-2&lt;/sup&gt;&amp;#160;s&lt;sup&gt;-1&lt;/sup&gt;) than at mixed forest&amp;#160;(-6.5 &amp;#956;mol m&lt;sup&gt;-2&lt;/sup&gt;&amp;#160;s&lt;sup&gt;-1&lt;/sup&gt;) during the growing season (May through September). &amp;#160;The monthly&amp;#160;fluctuation of column-averaged CO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;concentrations (XCO&lt;sub&gt;2&lt;/sub&gt;) exceeded 10 ppm&amp;#160;in Northeast China during 2016. &amp;#160;Biogenic contribution&amp;#160;(large&amp;#160;negative&amp;#160;in summer&amp;#160;and insignificant in other months)&amp;#160;offset about 70% of anthropogenic contribution of XCO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;in this region. &amp;#160;WRF-VPRM modeling successfully captured seasonal&amp;#160;and episodic variations of NEE and CO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;concentrations, however, the NEE in mixed forest was overestimated during daytime, mainly due to the uncertainties of VPRM parameters,&amp;#160;especially maximum light use efficiency.&lt;/p&gt;

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