The Estimation For The Irradiation Within Canopy Gap Based On LiDAR

Airborne laser scanning(ALS)is a new type of active remote sensing technology,which can obtain high-precision vegetation structure information and three-dimensional terrain features of forest ecosystem on multiple time and space scales.The high-precision monitoring of canopy gaps by ALS has great potential in understanding forest disturbance,regeneration law and inversion of ecological environment parameters.Most of the researches focus on the use of ALS for forest biomass monitoring,while the measurement of solar radiation at the gaps is rarely involved.In this paper,the research on the estimation of light intensity of gaps based on ALS is carried out,and its theoretical significance and application value are self-evident.The main research contents are as follows:(1)Plots of Wugang forest farm in Hunan Province were taken as the research objects.The structure of gaps was identified by using the point cloud data of ALS.The comparison between the ALS recognition results and the measured data shows that the difference rate of the gap area of the two plots is 8.01%and 7.37%,respectively.The difference rate of edge wood height was-5.95%and-7.39%,respectively.The difference rate of shape coefficient of gap is-2.45%and-5.45%,respectively.The significance of normal distribution shows that there is no significant difference between the results of ALS point cloud data recognition and the field measured results.(2)A method for estimating the solar radiation intensity of forest windows based on ALS is proposed.According to the solar altitude angle and azimuth angle,the solar radiation intensity under the clear weather condition in the area to be measured is estimated.Combined with DEM,the direct and scattered solar radiation received above the canopy under the complex terrain condition is calculated;The linear correlation coefficients R2 of ALS at the center,big,small and edge of forest window were 0.727,0.71,0.674 and 0.408,respectively.The difference between the total solar radiation estimation and the field survey results is not significant.