| In recent years,with the development and application of forest remote sensing technology,remote sensing becomes an effective means to obtain woodland information.TM images in 1990 and OLI images in 2017 of the Philippines are used as data sources for image preprocessing including radiometric calibration,band synthesis,image mosaic and image clipping.The woodland types of two stages are obtained by combining vegetation index method,tasseled cap transform,maximum likelihood supervised classification and decision tree.Through the extent of change in land use,the relative change rate of land use type,the woodland transfer matrix and the landscape index,this paper analyzes the characteristics of the woodland distribution change and transformation in the Philippines.Topographic factors such as elevation and slope are extracted from DEM of Philippines and their effects on the relative change rate of woodland are analyzed.Based on my tutor’s project "remote sensing interpretation of land cover in the Philippines",a strategic pilot science and technology project of the Chinese academy of sciences,this study investigates the temporal and spatial pattern change of woodland in the Philippines.The results show that:(1)during the period from 1990 to 2017,the structure of woodland in the Philippines did not change significantly.Natural forest and secondary forest still played a dominant role,accounting for more than 60%of the total area of the country.Natural forest,grass and shrub area decreased,secondary forest,plantation and mangrove area increased;In the Philippines,the change range of woodland is plantation,shrub,grass,natural forest,mangrove and secondary forest.(2)in the 17 regions of the Philippines,the regions with significant changes in woodland are the Western Visayas region,the National Capital Region and the Caraga region.(3)the interconversion of woodland in the Philippines is mainly manifested as the interconversion of natural forest,secondary forest and grass,and the transfer area is relatively large.(4)in the Philippines,the largest patch index(LPI)and the largest landscape shape index(LSI)of natural forest shows a decreasing trend.The maximum patch index(LPI)and the largest landscape shape index(LSI)of plantation shows an increasing trend;(5)the proportion of natural forest in the 100-200m elevation zone in the Philippines decreased the most,and the proportion of natural forest increased with the increase of slope;Plantations are mainly distributed below the slope of 20,with the highest percentage increase in the 100-200m elevation zone.The proportion of secondary forest decreased with the increase of slope,and the proportion of secondary forest increased the most in the 400-600m elevation zone.(6)natural forest is more affected by terrain factors than other woodlands. |
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