Abstract: Three sides of the Minqin oasis are surrounded by sand; the local population has made unremitting efforts to construct an oasis protection system and monitor and evaluate vegetation changes occurring in the protection belt. This study utilized Landsat TM/OLI remote sensing satellite data from 1996, 2006 and 2016 collected during the vegetation growth period in the Minqin oasis protection belt. Using ENVI 5.3 and Arcgis 10.4 as image processing tools, a normalized difference vegetation index (NDVI) for the study area was calculated while a dimidate pixel model (DPM) was used to calculate vegetation coverage to determine the spatial distribution and dynamic changes in different vegetation types in the Minqin Oasis. A decision tree classification technique based on a CART algorithm and combined multivariate data were used to classify land use types, allowing the area of the oasis protection belt and vegetation changes to be estimated. The results showed that compared with 1996, the area of low and high coverage vegetation in 2006 was 32.48% and 27.65% greater, respectively. However by 2016 the area of low coverage and middle and high coverage vegetation had decreased by 26.28% and 24.00% respectively. In addition, the proportion of low, medium and high vegetation had increased by 205.47%, 4.12% and 44.22%, respectively. Over the past 20 years, the area of low coverage vegetation initially increased and then decreased. Land use classification showed that compared with 2006 the area of farmland shelterbelt and dune windbreak in 1996, was 148.68% and 16.47% higher, respectively. The area of farmland protected by shelterbelts in 2016 was 33.99% lower than in 2006 but the area of windbreak and sand stabilizing plantations forest increased by 3.55%. The research revealed that over the last 20 years, the area of low coverage vegetation in the Minqin oasis has been decreasing and that the ecological environment has improved. The area of windbreak and sand stabilizing forest increased rapidly at first and but more slowly latterly.

Key words: Minqin oasis, shelter belt, vegetation coverage changes, remote sensing monitoring