Comparison Of Measurement Methods Of Leaf Area Index Of Mountain Steppe Vegetation On The Northern Slope Of Tianshan Mountains

Based on the six typical plant species of mountain steppe in northern slope of Tianshan mountains in Xinjiang as the research material,the camera was used to auxiliary computer image processing software to determine the leaf area of actual value of the samples,and then through the PSR-3500 filed spectrometer measured canopy reflectance of plants,the samples back to the laboratory determination of the fresh weight and dry weight.The regression equation was established between the fresh weight,dry weight and canopy spectral data and the actual values of leaf area.The results are as follows:(1)The sample leaves were photographed by high-definition digital camera,through the Photoshop and ENVI 5.2 software for processing the photos can be quickly determined the actual leaf area of six plants species,for measuring the leaf area also has a higher accuracy of the different leaf.(2)The regression equation can be used to determine the leaf area directly by using the fresh weight and dry weight of leaf and the actual value of leaf area.The fresh(dry)weight and the correlation coefficients of leaf area was above 0.85(P<0.001);the correlation coefficient of the fresh(dry)weight and leaf area prediction value and the actual value is more than 0.90(P<0.001);the accuracy of plant leaf area predicted by the fresh weight method and the actual value of Artemisia frigida and Stipa capillata precision higher than 70%,Festuca ovina is up to 83%,respectively,while the contents of Carex turkestanica,Astragalus sp.and forbs precision is less than 70%;the accuracy of plant leaf area predicted by the dry weight method and the actual value of A.frigida,S.capillata,F.ovina,and C.turkestanica accuracy was higher than 70%,only less than 70% of Astragalus sp.and forbs.(3)TSAVI,NDVI,SAVI,MSAVI 2 and RVI were in accordance with the measurement accuracy.Only the coefficient of determination of TSAVI were 0.5872 of the fitting equation,the other four were all around 0.62;to predict the leaf area values for accuracy verification,prediction accuracy of the five indices were above 70%,which is consistent with the results measured by fresh weight and dry weight method.(4)Compared with camera-aided computer image processing software and fresh(dry)weight method,vegetation index method can not only realize the rapid determination of non-destructive measurement of leaf area and is suitable for large scale,is a more as an ideal method.