scholarly journals Variations in fraction of absorbed photosynthetically active radiation and comparisons with MODIS data in burned black spruce forests of interior Alaska

Polar Science ◽  
2013 ◽  
Vol 7 (2) ◽  
pp. 113-124 ◽  
Author(s):  
Hiroki Iwata ◽  
Masahito Ueyama ◽  
Chie Iwama ◽  
Yoshinobu Harazono
Keyword(s):  
Photosynthetically Active Radiation ◽  
Black Spruce ◽  
Active Radiation ◽  
Spruce Forests ◽  
Modis Data ◽  
Interior Alaska ◽  
Absorbed Photosynthetically Active Radiation

scholarly journals Upscaling from Instantaneous to Daily Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) for Satellite Products

2020 ◽  
Vol 12 (13) ◽  
pp. 2083
Author(s):  
Siyuan Chen ◽  
Liangyun Liu ◽  
Xue He ◽  
Zhigang Liu ◽  
Dailiang Peng
Keyword(s):  
Zenith Angle ◽  
Photosynthetically Active Radiation ◽  
Solar Zenith Angle ◽  
Field Measurements ◽  
Area Index ◽  
Active Radiation ◽  
Sensing Applications ◽  
Typical Satellite ◽  
Absorbed Photosynthetically Active Radiation ◽  
Local Noon

The fraction of absorbed photosynthetically active radiation (FAPAR) is an essential climate variable (ECV) widely used for various ecological and climate models. However, all the current FAPAR satellite products correspond to instantaneous FAPAR values acquired at the satellite transit time only, which cannot represent the variations in photosynthetic processes over the diurnal period. Most studies have directly used the instantaneous FAPAR as a reasonable approximation of the daily integrated value. However, clearly, FAPAR varies a lot according to the weather conditions and amount of incoming radiation. In this paper, a temporal upscaling method based on the cosine of the solar zenith angle (SZA) at local noon ( c o s ( S Z A n o o n ) ) is proposed for converting instantaneous FAPAR to daily integrated FAPAR. First, the diurnal variations in FAPAR were investigated using PROSAIL (a model of Leaf Optical Properties Spectra (PROSPECT) integrating a canopy radiative transfer model (Scattering from Arbitrarily Inclined Leaves, SAIL)) simulations with different leaf area index (LAI) values corresponding to different latitudes. It was found that the instantaneous black sky FAPAR at 09:30 AM provided a good approximation for the daily integrated black sky FAPAR; this gave the highest correlation (R2 = 0.995) and lowest Root Mean Square Error (RMSE = 0.013) among the instantaneous black sky FAPAR values observed at different times. Secondly, the difference between the instantaneous black sky FAPAR values acquired at different times and the daily integrated black sky FAPAR was analyzed; this could be accurately modelled using the cosine value of solar zenith angle at local noon ( c o s ( S Z A n o o n ) ) for a given vegetation scene. Therefore, a temporal upscaling method for typical satellite products was proposed using a cos(SZA)-based upscaling model. Finally, the proposed cos(SZA)-based upscaling model was validated using both the PROSAIL simulated data and the field measurements. The validated results indicated that the upscaled daily black sky FAPAR was highly consistent with the daily integrated black sky FAPAR, giving very high mean R2 values (0.998, 0.972), low RMSEs (0.007, 0.014), and low rMAEs (0.596%, 1.378%) for the simulations and the field measurements, respectively. Consequently, the cos(SZA)-based method performs well for upscaling the instantaneous black sky FAPAR to its daily value, which is a simple but extremely important approach for satellite remote sensing applications related to FAPAR.

Absorbed photosynthetically active radiation and sun‐view geometry effects on remote sensing relationships∗

1998 ◽  
Vol 17 (1-4) ◽  
pp. 89-102 ◽  
Author(s):  
E.A. Walter‐Shea ◽  
B.L. Blad ◽  
M.A. Mesarch ◽  
C.J. Hays ◽  
D.W. Deering ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Photosynthetically Active Radiation ◽  
Active Radiation ◽  
Geometry Effects ◽  
Absorbed Photosynthetically Active Radiation

Potential use of bialaphos, a microbially produced phytotoxin, to control red raspberry in forest plantations and its effect on black spruce

1991 ◽  
Vol 21 (4) ◽  
pp. 489-497 ◽  
Author(s):  
Robert Jobidon
Keyword(s):  
Active Ingredient ◽  
Photosynthetically Active Radiation ◽  
Black Spruce ◽  
Growth Increment ◽  
Height Growth ◽  
First Year ◽  
Quadratic Relation ◽  
Foliar Injury ◽  
Red Raspberry ◽  
Active Radiation

Bialaphos foliar sprays were tested in eastern Quebec for control of red raspberry (Rubusidaeus L.), and the tolerance of planted black spruce (Piceamariana (Mill.) B.S.P.) seedlings was determined. Approximately 3 weeks after bialaphos was applied in July, August, or September, virtually all raspberry plants were killed. Efficiency of the June application, however, was much reduced. Spruce current-year foliage was more affected than older foliage. Foliar injury was more pronounced for bialaphos applications in June and July than for applications in August. First-year spruce survival was not affected by the treatments. Second-year evaluations revealed a significant quadratic relation of (i) month of application × bialaphos rate on raspberry density and (ii) bialaphos rate on raspberry height growth. Reduction in raspberry density and height growth was greater with the 2.0 and 2.5 kg active ingredient per hectare rates applied in August. As part of the evaluation of treatment efficiency, photosynthetically active radiation reaching spruce seedlings was measured using a portable integrating radiometer. Raspberry density and height growth were both negatively correlated with photosynthetically active radiation reaching spruce seedlings. A significant quadratic relation was found between bialaphos rate and 2nd-year spruce survival, which reached 95%, regardless of month and rate of application. A significant quadratic relation was found between spruce diameter growth increment and bialaphos rate. Except for calcium, 2nd-year spruce foliar mineral content was not affected by the treatments. Bialaphos treatments in August, with rates ranging from 1.0 to 2.0 kg active ingredient per hectare, had only slight or no adverse effects on spruce survival, foliar injury, and growth increment. Selective control of red raspberry in young black spruce plantations is a function of bialaphos rate and month of application.

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