Abstract
Vegetation coverage is an important indicator in regional ecological environment monitoring and plays a key role in its quality assessment. We consider Landsat7 ETM+ in 2000 and Landsat8 in 2016 as data sources using a different time phase partial image substitution method to eliminate cloud effects and an NDVI dimidiate pixel model to invert the vegetation coverage of the two time phases. We further classify them into five grades, provide statistics and analyse the areas of different grades at different time periods, while monitoring the spatial evolution of vegetation coverage over the past 16 years in Tongren. Experimental results showed that: (1) the different time phase partial image substitution method could reduce the influence of clouds on vegetation extraction; (2) in Tongren, the vegetation coverage area was decreased from 17,300.1 km2 to 17,224.8 km2 (i.e. decreased by 75.3 km2); (3) the areas of grade I and V increased by 0.42% and 15.08%, respectively, whereas the areas of grade II, III and IV decreased by 3.15%, 6.98% and 5.37%, respectively, which indicates that most of the area containing lower amount of vegetation gradually altered into an area containing a higher coverage of vegetation, whereas a few areas became bare land; and (4) the vegetation areas decreased due to expansion of cities and construction of dams, while vegetation increased due to the cultivation of crops and trees. Research shows that the overall evolution of vegetation coverage in Tongren is considerably good. However, while undertaking future development in the mountainous Karst region, one should be aware of the land's intensive use and environmental protection.
Highlights
Vegetation is an important component of the ecological environment and directly reflects the status of the environment (Liu et al 2009)
By searching the US geological survey (USGS) website, we found Landsat8 imagery that was imaged on February 12nd, 2017 when the region was not covered by any clouds
Based on the pixel dimidiate pixel model of the NDVI, vegetation coverage information was extracted from a Landsat7 ETM+ image in 2000 and a Landsat8 image in 2016
Summary
Vegetation is an important component of the ecological environment and directly reflects the status of the environment (Liu et al 2009). The Fanjing Mountain is an area under Tongren’s jurisdiction and is a member of the United Nations Human and Biosphere Reserve Network It is a national nature reserve and a famous Buddhist mountain in China, with a regional forest coverage rate that is greater than 95% and contains negative oxygen ions per cubic centimetre ranging from 6-12 million. The panchromatic and multispectral image resolutions were 15 and 30 m, respectively, and the track number of the two scenes images were 126/40 and 126/41, respectively Since they were affected by clouds at the location, it is difficult to find images containing less than 20% of cloud coverage in the Tongren prefecture. We queried earlier dates and found that the Landsat ETM+ images (track number is 126/40 and 126/41) of obtained on 21st May 2000 has no cloud coverage We downloaded these two scenes of remote sensing images. A 15-m spatial resolution image data with different times and data sources were obtained, and the captured final image was processed at latitude and longitude ranges of 107°44’15.93”–109°29’33.78” E, and 27°06’27.95”–29°04’4.67” N, respectively
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