Land Use/Land Cover Evaluation Using Trajectory Maps Based on Landsat TM/OLI in Southwest China

This study mainly aims to detect the county-level spatio-temporal variability of LULCC (Land Use and Land Cover Change) spatial patterns in Southwest China. Multi-temporal Remote Sensing (RS) images (Landsat TM/OLI in 2000, 2005, 2010, and 2015) were applied to extract land use/cover types at each of the four-time nodes using the Support Vector Machine (SVM) method. Then, the trajectory map methodology was adopted to identify the spatio-temporal distribution characteristics of LULCC patterns throughout the given time series. According to the results, the area of unused land decreased continuously, 0.094% total. An evident decline of grassland by 2.17% was documented, and a notable increase was observed in forestland by 63.94 km2 during the period from 2000 to 2015. Water bodies, built-up land, and unused land showed no significant change throughout the study period. The conversion from grassland to forestland and vice-versa (code 13 or 31) was prominent due to an adjustment made to local forestry policy during the first two periods (2000-2005 and 2005-2010), accounting for 17.55% and 17.56% of the study region, respectively. The anaphase trajectory transition type occupied the smallest area of all the trajectory maps. By contrast, the repetitive trajectory was the leading land-use transition type and covered the largest area. Trajectory analysis provides an effective approach for detecting the spatio-temporal changes in LULCC patterns.