![RESEARCH ON FPAR VERTICAL DISTRIBUTION IN DIFFERENT GEOMETRY MAIZE CANOPY Dr.Liu Rongyuan [email_address] Pro. Huang Wenjiang huangwj@nercita.org.cn Beijing Normal University Beijing Agriculture Information Technology Research Center July 27, 2011](https://image.slidesharecdn.com/we4-110727180149-phpapp01/85/WE4-T05-2-ppt-1-320.jpg)
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- 1. RESEARCH ON FPAR VERTICAL DISTRIBUTION IN DIFFERENT GEOMETRY MAIZE CANOPY Dr.Liu Rongyuan [email_address] Pro. Huang Wenjiang huangwj@nercita.org.cn Beijing Normal University Beijing Agriculture Information Technology Research Center July 27, 2011
- 4. Why we do this research? The leaf vertical distribution caused the FPAR vertical distribution! (more than 10 leaves for maize) The leaf angle distribution ( LAD) affect the FPAR distribution It is important to establish the model to retrieve canopy structure parameters based on remote sensing data.
- 6. Methods Upward Flux Downward Flux （ SHAW model ) (Flerchinger ， 2007 ） (beam radiation) (scattering radiation) How to establish models to describe the flux upward and downward based on the radiation transmission equations of SHAW (Simultaneous Heat and Water)) model?
- 7. Methods we derived the Downward flux of short-wave radiation between canopy layer i and the next layer i+1, which contain two parts, the first part is the downward flux of beam radiation , and the other one is the downward flux of scattering radiation . represent the total flux of beam radiation penetrating through the canopy, is the albedo of the canopy leaves by leaf transmissivity, and represent the fraction of beam radiation and scattering radiation passing through the layer i unimpeded by vegetation, respectively is the fraction of reflected upward diffuse radiation that is scattering downward. is the fraction of reflected downward diffuse radiation that is scattering downward is the fraction of reflected upward direct radiation that is scattering downward
- 11. Precision Agriculture Research and Demonstration station (167ha)
- 14. Validation The results show that the model could simulate the FPAR vertical distribution in maize canopy well . The result of simulation FPAR was validated by SUNSCAN measurement The model simulation fit measurement in situ well in two different stages. The maximum RMSE is 0.168. In the figure P and V stands for measuring parallel and perpendicular to the row, respectively.
- 15. LAI/Leaf Angle and Canopy Spectra Asner, 1998 MLA is Mean Leaf Angle
- 21. Leaf Angle Distribution (LAD) by beta distribution function and radiative transfer SAILH model for different LAD varieties.
- 22. Leaf Angle Distribution (LAD) by beta distribution function and radiative transfer SAILH model for different LAD varieties. The proportion of leaf angle in 5° angle classes ( 5°-90°) erectophile varieties is dominated by about 75°, planophile varieties is dominated by about 55° , horizontal varieties is dominated by about 35 °
- 23. Identification of crop canopy geometry by bidirectional canopy reflected spectrum
- 26. Identification of crop canopy geometry based on bidirectional canopy reflected spectrum NW1 NW2 NW4 NW3 NW5
- 29. Thank you very much for your attention! Dr. Liu Rongyuan [email_address] Pro. Huang Wenjiang [email_address]
Hinweis der Redaktion
- As known to us all, PAR is an key parameter for estimating plants net primary productivity. It is the radiation (400-700nm) which can be absorbed by plants directly to realize their material accumulation. FPAR is the fraction of absorbed PAR captured by canopy. To study the regularity of the distribution of FPAR in the canopy have important meaning to quantitatively simulate crops photosynthesis process 、 analysis crop material productive forces, and crop yield prediction ability in agricultural application. Also it is the foundation to build a model to retrieve canopy structure parameters based on remote sensing data.
- As known to us all, PAR is an key parameter for estimating plants net primary productivity. It is the radiation (400-700nm) which can be absorbed by plants directly to realize their material accumulation. FPAR is the fraction of absorbed PAR captured by canopy. To study the regularity of the distribution of FPAR in the canopy have important meaning to quantitatively simulate crops photosynthesis process 、 analysis crop material productive forces, and crop yield prediction ability in agricultural application. Also it is the foundation to build a model to retrieve canopy structure parameters based on remote sensing data.
- Some research have found out some parameters can effect the distribution of PAR in canopy, such as canopy structure, including both single plant and colony ‘s structure. and solar zenith angle\\ incidence intensity and so on.. But there are few research done to study the vertical distribution of FPAR. Our research is mean to build a quantitative model taking these effective factors into account to simulate the FPAR vertical distribution.
- Our methods is using models to describe the flux upward and downward based on the radiation transmission equations of SHAW (Simultaneous Heat and Water)) model. Based on the upward flux model of the SHAW model, we derived the Downward flux of short-wave radiation between canopy layer i and the next layer i+1, which contain two parts, the first part is the downward flux of beam radiation , and the other one is the downward flux of scattering radiation. represent the total flux of beam radiation penetrating through the canopy, is the albedo of the canopy leaves is the leaf transmissivity. and represent the fraction of beam radiation and scattering radiation passing through the layer i unimpeded by vegetation, respectively is the fraction of reflected upward diffuse radiation that is scattering downward. is the fraction of reflected downward diffuse radiation that is scattering downward.is the fraction of reflected upward direct radiation that is scattering downward
- Our methods is using models to describe the flux upward and downward based on the radiation transmission equations of SHAW (Simultaneous Heat and Water)) model. Based on the upward flux model of the SHAW model, we derived the Downward flux of short-wave radiation between canopy layer i and the next layer i+1, which contain two parts, the first part is the downward flux of beam radiation , and the other one is the downward flux of scattering radiation. represent the total flux of beam radiation penetrating through the canopy, is the albedo of the canopy leaves is the leaf transmissivity. and represent the fraction of beam radiation and scattering radiation passing through the layer i unimpeded by vegetation, respectively is the fraction of reflected upward diffuse radiation that is scattering downward. is the fraction of reflected downward diffuse radiation that is scattering downward.is the fraction of reflected upward direct radiation that is scattering downward
- Moreover, Due to the bottom is soil and the boundary condition was set as the equation (right one, red underline). At this point, we have revised a minor error of the original paper of SHAW model. Finally we build a model to calculate Layer’s FPAR when obtained the upward flux and downward flux of each layer.
- In order to validate our model ,we developed a test in China National Experimental Station for Precision Agriculture in the summer of 2010. We choose two different variety maize—compact and half compact, setting them in two dates, it means to obtain the data of two different grow stages at one experiment.
- In the test ,we captured these fowling parameters, including the spectrum character of Laves and soil by integral sphere device and ASD 、 plant features such as LAI\\LAD, and vertical distribution of flux of PAR by SUNSCAN—the canopy analysis system.
- Leaf’s shapes of plant always can be express by curves, thus the plant features could obtained by measuring the height of plant, the certain coordinates of feature point and the angle of leaf’s bending, show as this image. By analyzing the relationship among leaf’s shape, area, and position. we can get LAI and LAD in arbitrary space. This figure (fig.2) is the result of LAI distribution of maize by setting the layer space 20cm
- This figure is the comparison result of simulation FPAR and measuring FPAR by SUNSCAN, from this figure we can see our model fit measurement in situ well in the both Little coiled stage and the jointing stage. The maximum RMSE is 0.168. In the figure P and V stands for measuring parallel and perpendicular to the row, respectively.
- The simulation result show that a big LAI of layer is corresponding with big FPAR for upper part of plant but small FPAR for lower part of the plants. The increase of LAI of the canopy caused the increase of the total absorption ratio inner the canopy until the FPAR becomes saturation with LAI about equal to seven.
- However, the influence from ALA of the layer showed a opposite result that the decrease of this parameter brought a increase to FPAR for upper part of plant while the FPAR decrease in lower part of plant. For total canopy, the increase of ALA lead the total FPAR in the canopy to decrease, which indicated that the canopy will intercept more incident light flux if the distribution of its leaf angles is close to the feature of half compact canopy.
- From the influence from Solar elevation angle on layer FPAR inner canopy, the increase of solar elevation angle can make the FPAR decrease in the parts with height less than 80 while make the FPAR increase in the rest part of the plant. From the right figure of this slide, we can see that the increase of solar elevation angle reduce the total FPAR in canopy. However, this result did not mean that a bigger solar elevation angle will make the absorbed incident flux decrease, because the absorbed flux by the canopy is also determined by the total amount of incident solar flux.
- From the figure, For the total FPAR, the increase of the ratio of sky scattering light leads the total FPAR to increase.