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Liu S.,Beijing Normal University | Su X.,Beijing Normal University | Dong S.,Beijing Normal University | Cheng F.,Beijing Normal University | And 4 more authors.
GIScience and Remote Sensing | Year: 2015

Grassland biomass on the Qinghai-Tibet Plateau is of great significance for the study of wildlife habitat and climate change. Based on Systéme Pour l’Observation de la Terre Vegetation normalized difference vegetation index (NDVI) data from 1998 to 2012 and a field survey investigation in 2013, we assessed aboveground biomass (AGB) dynamics in the Altun Mountain Nature Reserve. The results demonstrated that annual NDVI values varied greatly with an increasing trend. Areas of high- and medium-coverage grassland showed similar increasing trends. The NDVI–biomass relationship could be quantified by an exponential model and previous models overestimated the amount of biomass in the alpine desert grassland. The total biomass was estimated to be 62 × 106 kg per year with large annual variations. No significant relationship was found between AGB and soil organic carbon contents, and the total grassland area (NDVI > 0.1) was positively correlated with the annual average temperature. © 2015 Taylor & Francis Source


Liu S.-L.,Beijing Normal University | Zhao H.-D.,Beijing Normal University | Dong S.-K.,Beijing Normal University | Su X.-K.,Beijing Normal University | And 2 more authors.
Chinese Journal of Ecology | Year: 2014

Alpine desert grassland dynamics is important for global change study. As one of the four largest “no-man lands” in China, Altun Mountain National Nature Reserve is facing alpine desert grassland ecosystem changes, which may have a tremendous impact on the habitats of wild animals. Especially, the landscape along the rive corridor could be greatly affected by climate change. Based on GIS and RS technology, we selected a typical river corridor in Aya Lake Basin as the case study site and classified the landscape types using remote sensing data in 1990, 2001 and 2007. Taking advantages of landscape theories and methods, we analyzed the landscape pattern and dynamics in the region. The results showed that the areas of both water and saline-alkali lands in the region increased significantly, while the grasslands with different coverage degraded due to the conversion into other land uses. The integrated pattern of landscape changed greatly. Patch density and landscape diversity index increased, while the landscape shape became simple. Largest patch index increased and the splitting index decreased. The increases of water area and saline-alkali land with grassland degradation caused the decrease of the NDVI values. Climate change trend analysis suggested that the increases in precipitation and temperature were the major driving forces for the landscape change in the region. The rise of the lake water area changed the distribution of the swamp, leading to the increase of water table and the increase of soil salinization. © 2014, Editorial Board of Chinese Journal of Ecology. All rights reserved. Source


Zhao H.,Beijing Normal University | Liu S.,Beijing Normal University | Dong S.,Beijing Normal University | Su X.,Beijing Normal University | Zhang X.,Nature Reserve Administration of Altun National Nature Reserve
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

The distribution and dynamics of vegetation can reflect the distribution and changes of wildlife habitat to some extent. Tibetan Antelope, well-known as 'the numen of plateau', is an endemic animal on the Qinghai-Tibetan Plateau. However, the survival and distribution of Tibetan Antelope have been threatened by environmental deterioration and illegal poaching. This animal has been listed as an Class I species by the Convention on International Trade in Endangered Species (CITES) and as Category I by the Key Protected Wildlife List of China. This situation has attracted a great deal of attentions from government and conservation professionals. The population distribution of Tibetan Antelope remains unkown in Altun National Nature Reserve. The Altun National Nature Reserve, the largest inland nature reserve of China established in May of 1983, is one of the four "no man's-lands"in China. Due to its unique natural conditions, this reserve is preserving the rich natural resources, rare wild animals and plants. In this study, we analyzed the dynamics of vegetation in Altun National Nature Reserve based on remote sensing image data and GIS tool. The Normalized Difference Vegetation Index (NDVI) data were collected in 2000, 2005 and 2010. We merged the regions, which were covered by vegetation in the study years and the suitable habitats were identified through interpreting vegetation types, which can be used by Tibetan Antelopes as grazing pastures. Based on NDVI datasets collected in different years, we calculated the vegetation coverage and analyzed the spatial and temporal variations of vegetation coverage. Moreover, the changes of habitat were analyzed on the basis of vegetation coverage variations. The results showed that the vegetation coverage of the reserve was at a low level, and grids with low vegetation coverage took up about 50% of the regions that were covered by vegetation. The grids with high vegetation coverage were mainly distributed in the southwest of Kardun inspection station. The vegetation coverage in the regions where Tibetan Antelopes mainly lived was relatively higher, and that in the regions where the animal lambed was lower. The upward trends of vegetation coverage over time reflected the increase of the reserve's carrying capacity for animals, and it may also imply that the area of suitable habitat of this animal increased. The vegetation coverage of alpine steppe dominated by feather grass experienced a significant upward trend, also suggesting that carrying capacity of the reserve for Tibetan Antelope increased. The change of spatial distribution of feather grass steppe coverage indicated that habitat of Tibetan Antelopes might spread from east to southwest. The relationship between the altitude and vegetation coverage was not significant correlated. The study of habitat variations based on vegetation coverage is meaningful and can be used for better protecting this wildlife. Furthermore, we suggested that more factors could be integrated with vegetation coverage to precisely identify suitable habitat for animals, and more field surveys and monitoring should be conducted in the future. Source


Liu S.L.,Beijing Normal University | Zhao H.D.,Beijing Normal University | Su X.K.,Beijing Normal University | Deng L.,Beijing Normal University | And 2 more authors.
Rangeland Journal | Year: 2015

One of the focuses of global change research is on the impact of climate change on alpine vegetation. The Altun Mountain National Nature Reserve is the largest alpine desert rangeland reserve in China to protect wild endangered ungulate species. This paper aims to detect changing trends in rangeland conditions in this region. Temporal changes in the Normalised Difference Vegetation Index (NDVI) for the rangelands in the Altun Nature Reserve and its correlation with climatic variables were studied over the period from 1998 to 2012. Based on the NDVI index and using ArcGIS spatial analyst, the areas of likely rangeland degradation and areas of improved in rangeland condition were identified using linear regression analysis. The results showed that NDVI values were relatively low, varying from 0.04 to 0.1, and there existed distinct monthly changes. The highest NDVI values were exhibited in August. Generally, the NDVI showed an increasing trend over time with several annual fluctuations. High values were distributed mainly in the core area of the nature reserve. Trend analysis showed that vegetation near rivers and lakes was most likely to be degraded but, overall, the vegetation conditions improved over the 15 years of the study, which meant an improvement in the habitats of key wild ungulate species. Precipitation and temperature had a significant linear positive correlation with NDVI, which suggested that they were the main driving forces for rangeland improvement. The vegetation at the edge of the protected areas appeared degraded due to human activities. © Australian Rangeland Society 2015. Source


Zhao H.,Beijing Normal University | Liu S.,Beijing Normal University | Dong S.,Beijing Normal University | Su X.,Beijing Normal University | And 4 more authors.
Rangeland Journal | Year: 2015

This paper evaluated changes in vegetation from 2000 to 2012, based on 1-km resolution 16-day composite Moderate Resolution Imaging Spectroradiometer (MODIS) Normalised Difference Vegetation Index (NDVI), and related them to changes in estimates of human disturbance on the rangelands of the Qinghai-Tibet Plateau. The main rangeland types studied were desert, steppe and meadow with the latter mainly found in the southern and eastern parts of the study area. The results indicated that human disturbance was distributed mainly in the southern and eastern parts of the study area and corresponded with high NDVI values. The NDVI values showed an upward trend over the study period, with 28.5% of the study area exhibiting a significant increase. The proportion of rangelands that experienced a downward trend in NDVI increased as the level of human disturbance increased. Of the different rangeland types, meadow had the highest NDVI values, the greatest human disturbance, and the highest proportion of rangelands that exhibited a significant decrease in NDVI. Compared with areas with no human disturbance, meadow and steppe rangelands that experienced an increase in human disturbance had lower rates of increase in their NDVI values but, conversely, desert rangelands showed the opposite trend. In addition, it was found that precipitation had the dominant influence on NDVI values and that higher precipitation and slighter lower temperatures over the period of the study were related to an increase in NDVI values. © Australian Rangeland Society 2015. Source

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