Study On The Relationship Between LAI And NDVI Of Different Forest Types And Its Change Law

In order to reaserch the relationship between forest leaf area index(FCI)and forest stand and the terrain factors,this study took broadleaved forest and coniferous forest in the north of Yan Mountains,Hebei Province as the research object,through field investigation and RS data and the relationship between Lai and NDVI,and the relationship between Lai as resserch methohd,stand factors and terrain factors was analyzed by regression analysis and partial correlation analysis.The results as follows:(1)The leaf area index and Ndvi of broad-leaved and coniferous forests are exponential functions,and their goodness of fit R2(broad-leaved)is 0.845,R2(coniferous)0.841.(2)In the broad leaf forest and coniferous one,the increase of forest age,the leaf area index(LAI)increased gradually,and the increasing rate decreased gradually.The maximum LAI of broad leaf forest was between 40a and 50a,and its value was 6.39,the minimum value is between 0 and 10 years of age,and the value is 2.02.The optimal curve models of broad-leaved forest and coniferous forest in the studied age range are conic curves,and their goodness of fit R2(broad-leaved Forest)is 0.901,R2(coniferous forest)is 0.907.With the increase of stand density,broad-leaved forest and coniferous forest as a whole trend of increasing at first and then decreasing,and the decreasing range was very small and stable,the maximum leaf area index(LAI)of broad-leaved forest was 6.10 when the density was about 900 trees/hm2 and the Minimum LAI was about 400 trees/hm2 when the density was about 3.07,the maximum leaf area index(LAI)of coniferous forest appeared at the density of 1800 trees/hm2,its value was 5.86,and the minimum appeared at the density of 300 trees/hm2,its value was 3.17,the optimal curve models of the two stand types in the range of density studied are conic,and their goodness of fit R2(broadleaved forest)is 0.780,R2(coniferous forest)is 0.878;The Leaf area index of broad-leaved forest and coniferous forest showed a trend of increasing first and then decreasing with the increase of DBH,but the decreasing range was very small,the maximum leaf area index(LAI)of both broad-leaved and coniferous forests appeared in the range of 20cm～30 cm in DBH,but the emergence of broad-leaved forest was earlier than that of coniferous forest,in the range of DBH studied,the best curve model of the two stand types is conic,and its goodness of fit is 0.929 for broad-leaved forest and 0.924 for coniferous forest.With the increase of tree height,the change trend of the whole tree height increased at first and then decreased slowly.When the tree height reached 15m,the leaf area index(LAI)reached its maximum value,and the coniferous forest reached its maximum value at 18m,the best curve models in the range of DBH studied at present are conic,the goodness of fit R2(broad-leaved forest)is 0.849,R2(coniferous forest)is 0.918.(3)With the increase of altitude,the leaf area index increased first and then decreased,the Change Law of broad-leaved forest and coniferous forest was basically the same,the maximum value of broad-leaved forest is about 1500m,its value is 6.10,the minimum value is about 1900m,its value is 4.05,and the maximum value of coniferous forest is between 1300m and 1500m,its value is 6.06,its minimum value is 4.41 when the altitude is 700m～800m,and the best curve models are conic in the altitude range studied at present.Its goodness of fit R2(broadleaf forest)is 0.624,R2(coniferous forest)is 0.437;With the increase of slope gradient,the leaf area index(LAI)of broad-leaved forest increased at first and then decreased.The maximum value was about 10 slope gradient,the value was 5.79,the minimum value was about 50 slope gradient,the value was 4.05,the maximum value of conifer forest is about 10 slope,its value is 5.75,the minimum value is about 50 slope,its value is 3.98,the best curve model in the range of slope studied at present is conic,its goodness of fit R2(broadleaf forest)was 0.538,R2(coniferous forest)was 0.531,and the average change law of leaf area index(LAI)in different slope directions was half-sunny slope(6.14)>half-shady slope(5.5278)>Sunny Slope(5.50)>Shady Slope(4.89),the change rule in coniferous forest was half shady slope(5.99)>Half Sunny Slope(5.70)>Sunny Slope(5.12)>Shady Slope(5.05).(4)The influence degree of stand factors on leaf area index of broad-leaved forest is as follows:Stand Age>DBD>Height>density,the influence degree of stand factors on leaf area index of conifer forest is as follows:DBH>Age>Height>density;The influence degree of topography factor on leaf area index of broad-leaved forest is:altitude>Slope>Aspect,and the influence degree of topography factor of coniferous forest is:Slope>Elevation>aspect.