Estimating photosynthetically active radiation distribution in maize canopies by a three-dimensional incident radiation model

2008 ◽  
Vol 35 (10) ◽  
pp. 867 ◽  
Author(s):  
Xiping Wang ◽  
Yan Guo ◽  
Xiyong Wang ◽  
Yuntao Ma ◽  
Baoguo Li
Keyword(s):  
Photosynthetically Active Radiation ◽  
Three Dimensional ◽  
Incident Radiation ◽  
Parallel Projection ◽  
Central Projection ◽  
Plant Canopy ◽  
Radiation Model ◽  
Area Index ◽  
Active Radiation ◽  
Radiation Distribution

The three-dimensional (3-D) radiation distribution model in plant canopy is pivotal for understanding and modelling plant eco-physiological processes. Diffuse and direct radiations penetrate into plant canopies in different ways and may present different intensity and wavelength composition. Sunfleck (the canopy surfaces where the direct radiation reaches) distribution in the plant canopy is usually regarded as an important index for crop development, especially under dense canopy conditions. Distributions of direct and diffuse components of photosynthetically active radiation (PAR) in maize (Zea mays L.) canopies were estimated respectively using a 3-D incident radiation model (3DIRM). The 3DIRM model was set up for computing incident radiation in crop canopies by applying a parallel-projection based submodel for direct solar radiation and a central-projection based submodel for incident diffuse radiation simulation in crop canopy. It was well assessed with a field experiment with multi-point PAR measurement in maize canopies with relative errors of 2.6, 4.5 and 2.6%, respectively, for sunfleck area ratio, diffuse PAR and total PAR. The results suggest that the 3DIRM model could be used to estimate the direct, diffuse and total PAR at any specific surface part in the 3-D canopy space. The exponential distinction model for direct, diffuse and total PAR along with leaf area index in different heights in maize canopies was also evaluated based on the 3DIRM simulation results.

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.

Light interception and canopy radiation balance of staghorn sumac (Rhus typhina)

2008 ◽  
Vol 38 (6) ◽  
pp. 1695-1700
Author(s):  
Peter M. Lafleur ◽  
Andrew G. Farnsworth
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Photosynthetically Active Radiation ◽  
Solar Zenith Angle ◽  
Radiation Balance ◽  
Area Index ◽  
Mean Values ◽  
Active Radiation ◽  
Rhus Typhina ◽  
Flux Incident

We measured interaction of photosynthetically active radiation (PAR) at a staghorn sumac ( Rhus typhina L.) canopy near Peterborough, Ontario, during summer 2006. Measurements included above-canopy and below-canopy incoming and reflected PAR fluxes and leaf area index (LAI). The ratio of down-welling PAR below the canopy to the flux incident at the top of the canopy (τ) and proportion of incident PAR absorbed by the canopy (fPAR), were calculated. While the canopy was leafless, the sumac stems absorb 10%–20% of incident PAR. LAI increased rapidly during the month of June, and correspondingly τ decreased rapidly while fPAR increased rapidly. Mean values of τ and fPAR at maximum LAI were 0.38±0.09 (SD) and 0.60 ±0.04, respectively. Neither variable showed a relationship with solar zenith angle. We present a simple idealized model of PAR interaction with sumac. Although only one stand was studied, we hypothesize that these results may be more widely applicable to other mature sumac stands.

scholarly journals Impact of Vermicompost, Poultry Manure and Jeevaamrit on Growth Parameters of Kiwifruit (Actinidia deliciosa) cv. Allison

2020 ◽  
pp. 31-40
Author(s):  
Ashok K. Garg ◽  
Rajesh Kaushal ◽  
Vishal S. Rana
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Photosynthetically Active Radiation ◽  
Poultry Manure ◽  
Growth And Yield ◽  
Recommended Dose ◽  
Inorganic Fertilizers ◽  
Area Index ◽  
Active Radiation ◽  
Chlorophyll Index

The present investigation was conducted on 6 years old kiwifruit vines cultivar ‘Allison’ at a spacing of 4.0 m × 6.0 m for two consecutive years 2018-19 and 2019-20 at experimental block of Department of Fruit Science, Dr YS Parmar University of Horticulture and Forestry, Nauni, Solan (HP). The experiment was laid out in triplicate in Randomized Block Design with 8 treatments under three farming systems viz., Inorganic Fertilizer Based System (IFBS), Organic Farming Based System (OFBS) and Subhash Palekar’s Natural Farming System (SPNFS). The maximum leaf area (158.1 cm2), leaf area index (4.36), chlorophyll index (51.2), comparative photosynthetically active radiation (612 µ mol quanta m-2 s-1) was found in the treatment (T8) receiving 30 liters of jeevaamrit (JM) + 3 kg ghana jeevaamrit and 40 kg FYM per vine under SPNFS. Among OFBS, the treatment T2 (100% recommended dose of nitrogen (RDN) through vermicompost and poultry manure on 50:50 basis) observed maximum leaf area (151.8 cm2), leaf area index (4.35), comparative photosynthetically active radiation (642 µ mol quanta m-2 s-1) but lower significantly lower chlorophyll index (51.2) over T1 (Recommended dose of inorganic fertilizers + FYM) treatment of IFBS. Hence application of 30 litres jeevaamrit and 3 kg ghana jeevaamrit (both in 3 equal splits first in end of January, second in February and third in the month of April) along with 40 kg FYM per vine or alternatively substitution of 100% RDN through vermicompost and poultry manure on 50:50 basis along with 40 kg FYM were found to be best and alternate different option in place of inorganic fertilizers to ‘Allison’ cultivar of kiwifruit under mid-hill conditions of Himachal Pradesh, India. Furthermore, the research emphases mainly on improving soil health without compromising growth and yield of kiwifruits in the region. By using alternative sources of nutrients, farmers can obtain the comparable growth and yield of kiwifruits.

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