Inversion of Rice Canopy Construction Parameters from the Hemispherical Photograph

Abstract

It is important to find a fast, reliable and accurate method for estimating canopy construction parameters in the study of vegetation-climate interaction. In the present study, three rice varieties with different canopy structures were chosen as experimental materials. A digital camera with a fisheye lens was used to take photos in eight heights of rice canopy to develop a new approach for concluding rice canopy. Canopy gaps were extracted from those photos, and then leaf area index(LAI) and mean leaf angle(MLA) could be inversed by Beer-Lambert theory, based on the quantitative relationship between the radiation condition and the canopy structure. Results showed that LAI inverted from the hemispherical photograph was 7.6%–13.1% less than that measured manually, and the root mean square error(RMSE) between them was 1.2–1.5. The data showed that hemispherical photography was better than Sunscan canopy system. Moreover, MLA inverted from the hemispherical photograph was related to that measured manually with 0.9205** of correlation coefficient and 11.7° of RMSE. Therefore, hemispherical photography is a feasible technology to indirectly measure the rice canopy structure.