Monitoring land cover change and its dynamic mechanism on the Qehan Lake Basin, Inner Mongolia, North China, during 1977–2013

Abstract

The Qehan Lake Basin is located in the north of the Otindag Sandy Land, where the fragile eco-environment is sensitive to climate change and human activity. We analyzed land cover change and the concomitant processes of ecological change based on multi-spectral scanning (MSS), thematic mapper (TM), and enhanced TM (ETM+) images. The results showed that from 1977 to 2000, the area of dune sand increased significantly by 840.2 km, while the area of high cover grassland (HCGL), medium cover grassland (MCGL), and low cover grassland (LCGL) reduced by 140.6, 207.3, and 463.3 km, respectively. Additionally, the area of wetland decreased by 112.9 km. During the period of 1977 to 2000, the land cover condition index (LCCI) reached a low of 27.7, which indicated serious eco-environmental challenges in the Qehan Lake watershed. However, the process of desertification was reversed, and vegetation cover was gradually restored after 2000. From 2000 to 2013, the area of LCGL increased by 369.2 km (13.4%), while the area of dune sand decreased by 560.1 km (29.4%). The LCCI improved to reach 29.18 in 2013, demonstrating a significant eco-environmental improvement. Although climate change, human activity, and ecological policies have together determined the scope and extent of desertification in the watershed, the most fundamental factor in the restoration of vegetation was precipitation.

Normalized Difference Vegetation Index‐based assessment of climate change impact on vegetation growth in the humid‐arid transition zone in northern China during 1982–2013

“…The area with most significant negative residual trends seems to be located in the cropland on the Sanjiang Plan in the east tip of the study area. This suggests that the significant decline in NDVI in this area is largely caused by human activities such as over‐farming (Chun et al , ). Another possible reason is a shift in the dominant crop from wheat to soybean, which has shorter growing season (Liu et al , ).…”

“…() and Chun et al . (). In order to capture the full range of climate effect on vegetation, we incorporated additional climate variables in the MLR models based on their potential impacts on vegetation growth.…”

“…The uncertainty of estimated trends for both the modelled NDVI (climate factors) and residuals (human factors) is by calculating the standard errors for the trends (slope of the trend line). Similar methods have been used in previous studies such as Wessels et al (2012) and Chun et al (2018). In order to capture the full range of climate effect on vegetation, we incorporated additional climate variables in the MLR models based on their potential impacts on vegetation growth.…”

Complex disturbance‐driven reactivation of near‐surface sediments in the largest dunefield in North America during the last 200 years

“…Chun, 2018;Zhang and Huisingh, 2018;Xu et al, 2019) have looked at the relative contribution of climate change and human activities in driving changes in dune activity, but similar analyses have not been extended to other dryland environments, nor to time periods before the availability of recurrent satellite imagery in the 1970s and 1980s. In North China, a series of studies (e.g.…”

“…In North China, a series of studies (e.g. Chun, 2018;Zhang and Huisingh, 2018;Xu et al, 2019) have looked at the relative contribution of climate change and human activities in driving changes in dune activity, but similar analyses have not been extended to other dryland environments, nor to time periods before the availability of recurrent satellite imagery in the 1970s and 1980s. In this study, we use empirical data from the sedimentary record to test relationships between disturbances and surface sediment mobilization in the Niobrara Valley Preserve and surrounding ranches in the northern Nebraska Sandhills (Figure 1).…”