Measuring the dynamics of leaf area index of vegetation using fisheye camera

The rapid and accurate measurement of LAI is of great importance for the research of ecological processes. Photos from typical land use types in the northern Loess Plateau, including Caragana, Salix, alfalfa, wild grass, soybean and maize, were measured by digital hemispherical photography (DHP). Meanwhile, photos were daily taken by video camera with fisheye lens and the pictures were analyzed by image processing software to obtain the dynamics of LAI in soybean, maize and Caragana fields. The results showed that a linear correlation existed between the LAI measured by DHP and LAI-2200. The coefficient of determination (R²) was 0.85 (P<0.05) and root mean square error (RMSE) was 0.256. The key parameters of professional software were affected by the local solar radiation. When the downward lens was used, the green index was the key parameter which increased with the increase of solar radiation. However, the brightness index decreased with the increase of solar radiation when the lens was upward. Through the adjustment of the key parameters, the results of LAI of maize, soybean, and Caragana were consistent with the LAI-2200 results, well reflecting LAI dynamics during the plant growth. The downward lens in Caragana field was better. The fisheye camera could be used for monitoring the dynamic LAI of different vegetations.