Details

Autor(en) / Beteiligte

• Zou, Xiaochen
• Mõttus, Matti
• Tammeorg, Priit
• Torres, Clara Lizarazo
• Takala, Tuure
• Pisek, Jan
• Mäkelä, Pirjo
• Stoddard, F.L.
• Pellikka, Petri

Titel

Photographic measurement of leaf angles in field crops

Ist Teil von

• Agricultural and forest meteorology, 2014-01, Vol.184, p.137-146

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2014

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• •We tested the novel method of photographic leaf angle measurement in field crops.•Long and narrow cereal leaves were measured in segments.•Leaf angles from photography and LAI-2000 were highly correlated.•Crop reflectance at 748nm was highly correlated with leaf angle. Leaf angle distribution (LAD) is one of the most important parameters used to describe the structure of horizontally homogeneous vegetation canopies such as field crops. LAD affects how incident photosynthetically active radiation is distributed on plant leaves, thus directly affecting plant productivity. Knowledge of LAD is also required for retrieval of other important biophysical variables from measurements of canopy radiation transmittance or spectral reflectance. Unfortunately, its determination is laborious and measured data is rarely available. In this study, we applied a recently developed method for determination of the inclination angles using leveled digital photography to the leaves of six cool-temperate crops: faba bean, narrow-leafed lupin, turnip rape, wheat, barley, and oat. The method, previously applied only to small and flat leaves of broadleaved trees and bushes, was extended to be applicable to the narrow and curved leaves of cereals. A reasonable match was found between the leaf angles determined by photographic measurements and the mean leaf tilt angles (MTA) measured using a LAI-2000 plant canopy analyzer for five out of the six species (R2=0.92). The error caused by assuming a spherical LAD, when calculating LAI from canopy transmittance measurements, varied between 0 and 1.5 LAI units, depending on species. Finally, we analyzed the correlation between photographically determined species-specific LADs and airborne imaging spectroscopy data acquired for the same species in a similar growth stage. The highest correlation between spectral reflectance factor and leaf mean tilt angle was found at a wavelength of 748nm (R=0.80). The high correlation between MTA and this red edge waveband can be useful for MTA determination from imaging spectroscopy.