Land Cover Change in
R
esponse to Climate Variation in the Source
Region of the Yangtze River (SRYR), Central Tibetan Plateau
Guangyin Hu
1,*
, Zhibao Dong
2
, Yanhong Gao
3
, Lunyu Shang
3
, Junfeng Lu
1
and Changzhen Yan
1
1
Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy
of Sciences, Lanzhou 730000, China;
2
School of Geography and Tourism, Shaanxi Normal University, Xi’an, China;
3
Key Laboratory for Land Surface Process and Climate Change in Cold and Arid Regions, Chinese Academy of Sciences,
Lanzhou 730000, China;
Keywords: Source region of the Yangtze River (SRYR), land cover change, climate change, Tibetan Plateau
Abstract: The Yangtze River is China's longest river and its source region is sensitive to climate variation due to its
high elevation. With the influence of global warming, the land cover change can be taken as the joint result
of climatic factors. However, during the time when air temperature increased rapidly from 1975 to 2005, the
relative importance of global warming to these land cover changes in Qinghai-Tibet Plateau is not well
understood. To accurately assess the land cover change during 1975-2005, Landsat images and GIS
techniques were used to monitor its distribution in 1975, 1990, and 2005. By overlay analysis, the dynamic
patterns of land cover change were observed. The main transition patterns are the higher coverage grassland
converted to lower coverage grassland (grassland degradation), grassland converted to swamped land, and
the lower coverage grassland converted to sandy land (grassland desertification). The rapid increased air
temperature was mostly responsible for the observed land cover change in SRYR.
1 INTRODUCTION
Monitoring the temporal land cover changes are
important for sustainable development (Lambin et
al., 2000) due to their close relationship with the
ecosystem processes (Shi et al., 2009) such as soil
erosion (Wang et al., 2014). The interactions
between land cover variation and climate variation is
complicated (Bonan, 2008; Pielke, 2005). Nearly
25 % of the Yangtze River’s flow originates in the
SRYR. This region lies at an altitude greater than
3,500 m above sea level, which makes it’s fragile
and susceptible to climate variations (Ren et al.,
2010).
During the last fifteen years, the environmental
problems of the Tibetan Plateau have been receiving
more and more attention due to the impacts from
global warming and increasing regional human
activities (Ren et al., 2010; Fang et al., 2011; Shen
et al., 2015; Arthur et al., 2008). The mean annual
temperature of the Tibet Plateau increased by 2.0 °C
during 1960-2010, and the ground surface
temperature increased by 1.7 °C (Shen et al., 2015).
The rapid climate change in this region is causing
lots of environmental problems. From 1986 to 2009,
the total glacier area loss was approximately 119.3
km
2
(Yao et al., 2014). Simulated results show that
the area of permafrost has reduced 18,900 km
2
from
1980s to 2000s (Fang et al., 2011). Meanwhile,
aeolian desertification land increased by 2,678 km
2
(Hu et al., 2012). As a result, the newly built
Qinghai-Tibet Railway (completed in 2006), which
runs through the SRYR undergoes serious
windblown-sand damages (Zhang et al., 2012), and
sand-damage–prevention measures have been used
along this railway (Cheng and Xue, 2014).
Furthermore, air temperature is expected to
continue increasing in the Tibetan Plateau during the
next one-hundred year (Shen et al., 2002), and this
will cause further more permafrost degradation (Nan
et al., 2004) and aeolian desertification (Wang et al.,
2002). To compare with the developed regions of
China, relatively less attention has been paid to land
cover change in sparsely populated Tibetan Plateau.
Hu, G., Dong, Z., Gao, Y., Shang, L., Lu, J. and Yan, C.
Land Cover Change in Response to Climate Variation in the Source Region of the Yangtze River (SRYR), Central Tibetan Plateau.
In Proceedings of the International Workshop on Environment and Geoscience (IWEG 2018), pages 477-483
ISBN: 978-989-758-342-1
Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
477

Understanding the dynamic patterns of land cover
evolution will provide more information for
environmental management.
2 STUDY AREA
The SRYR is located in China's Qinghai Province,
in the center of the Tibetan Plateau, covering an area
of 1.42×10
5
km
2
as shown in Figure. 1. The altitude
ranges from 3,350 to 6,519 m, with a mean altitude
of 4,754 m. Many rivers originate in this region,
which are Chumaer, Beilu, Tuotuo and Dangqu
rivers. Bayan Har Mountains is a southern branch of
the Kunlun Mountains. Glacier, lakes, swamped and
sandy lands are widely distributed.
This region is characterized by chilly, high-
altitude climate. The mean annual precipitation is
about 350 mm, and the difference in precipitation is
very obvious between dry and wet seasons.
The main vegetation includes high-cold meadow
species. Soils in this region are mainly alpine steppe
soils. More than 400 km of the Qinghai-Tibet
railway was built across the SRYR between Kunlun
and Tanggula mountains, which is called the
“World's highest railway” because over 80 % of the
railway is at altitudes above 4000 m, and the highest
point is 5,072 m above sea level at Tanggula
Mountains, and most of the railway on this sector
was laid atop permafrost. The Quaternary sediments
are widely distributed in this region (Wu et al.,
2006), which provide abundant of materials for wind
erosion (Huang et al., 1993).
Figure 1: Location of the source region of the Yangtze River in the Tibetan Plateau.
IWEG 2018 - International Workshop on Environment and Geoscience
478

2.1 Data Sources
Remote sensing (RS) technique and geographical
information system (GIS) software were applied to
get the extent of land cover at three years (1975,
1990 and 2005). The remote sensing images
included Landsat multi-spectral scanner (MSS)
acquired in 1975 (80-m spatial resolution); and
Landsat Thematic Mapper (TM) images acquired in
1990 and 2005 (30-m spatial resolution). Images
between June and October were selected, on account
of vegetation is more easily recognized in this
season (Ruelland et al., 2010).
2.2 Classification System for Land
Cover
The classification system of Chinese Resources and
Environment Database of the Chinese Academy of
Sciences was adopted in this study. In this study,
classification system is divided into two levels. At
first level, there are six classes viz. cultivated, forest,
grass, building and unused land as well as water
bodies. In this study, grassland were divided into
three categories (high, moderate, and low vegetation
coverage) as it was the main land cover type in this
region. All subcategories of water bodies, cultivated
land, building land, and forest were grouped into
first-level category, while, wetlands and sandy land
were separated from unused land since they are
particularly sensitive to climate change.
3 RESULTS
3.1 Land Cover Changes
Based on Landsat images, vector maps of land cover
in 1975, 1990 and 2005 were obtained as shown in
Figure. 2. It shows that grassland and unused land
were the dominant land cover types in the SRYR in
2005, accounting for 58.9 and 24.4 % of the total
study area, respectively. In 2005, high, moderate,
and low coverage grassland accounting for 10.3,
21.4, and 27.2 %, respectively of the total study area
(Table 1), and which were mainly distributed in the
south of this region (Figure. 2). Unused land had
consistently been the second most extensive land
cover type in the three periods, which accounting for
24.4 % of the area in 2005 (Table 1). Waters bodies
account for 7.2 % of the total study area in 2005,
and was mainly distributed in the west of the study
region. Although the distribution area of swamped
and sandy lands were relatively scarce, accounting
for only 4.2 and 3.7 %, respectively, the changes of
which can be taken as the responses of land covers
to climate change. Due to high-cold climate, only a
minority of forest is distributed in the southeast of
the study region, where altitude is relatively low
(3000~4000 m). As a lot of places of the study area
is no man's land, so the area of cultivated and
building lands is only 5 and 13 km
2
, respectively in
the whole SRYR.
Table 1: Area and percentage of each land cover type in the SRYR (km2).
Class
1975 1990 2005
Area
(km
2
)
% of
total
Area
(km
2
)
% of
total
Area
(km
2
)
% of
total
Cultivated land 12 0.0 12 0.0 13 0.0
Forest land 2336 1.6 2305 1.6 2280 1.6
High coverage
grassland
15392 10.8 15056 10.6 14631 10.3
Moderatecoverage
grassland
30822 21.7 30383 21.4 30389 21.4
Low coverage grassland 38766 27.2 38749 27.2 38752 27.2
Bodies of water 9932 7.0 10175 7.2 10280 7.2
Building land 4 0.0 6 0.0 5 0.0
Unused land 34707 24.4 34909 24.5 34783 24.4
Sandy land 4879 3.4 5117 3.6 5210 3.7
Swamped land 5450 3.8 5588 3.9 5958 4.2
Total 142299 100.0 142299 100.0 142299 100.0
Land Cover Change in Response to Climate Variation in the Source Region of the Yangtze River (SRYR), Central Tibetan Plateau
479

Figure 2: Land cover map of the SRYR in 1975, 1990, and
2005.
The high coverage grassland experienced the
most significant decrease during 1975-1990 and
1990-2005, decreased by 336 and 425 km
2
respectively. Meanwhile, the forest also experienced
a continuous declining trend during the two periods,
decreased by 56 km
2
from 1975 to 2005. On the
contrary, the area of water bodies, sandy and
swamped lands experienced a continuous increasing
trend. The area of water bodies increased by 243
km
2
from 1975 to 1990, and increased by 105 km
2
from 1990 to 2005. Sandy land increased by 238
km
2
from 1975 to 1990, and increased by 93 km
2
from 1990 to 2005. Swamped land increased by 139
km
2
from 1975 to 1990, and increased by 369 km
2
from 1990 to 2005.
In the period from 1975 to 2005, land covers in
the SRYR experienced sharp changes (Figure. 3).
The area of swamped, sandy lands and water bodies
increased obviously, increased by 508, 331 and 348
km
2
, respectively. The area of high and low
coverage grassland decreased sharply, decreased by
761 and 434 km
2
, respectively. Besides, the area of
forest decreased by 56 km
2
.
Figure 3: Net change area in each land cover type from
1975 to 2005.
3.2 Spatial Dynamic Processes of Land
Cover Change
The transition matrix for LUCC from 1975 to 2005
was calculated by overlay analysis (Table 2). A total
of 11,588 km
2
land cover changed during 1975-2005,
accounting for 8.1 % of this region. From the LUCC
transition matrix (Table 2), the main transition
patterns can be clearly observed, including the
transitions of moderate coverage grassland to low
coverage grassland (1255 km
2
), and high coverage
grassland to moderate (962 km
2
) and low coverage
grassland (242 km
2
). Besides, the transition of
grassland to sandy land (362 km
2
) and swamped
land (698 km
2
) were also obvious.
Table 2: The transition matrix of LUCC between 1975 and 2005 in the SRYR (km2).
Class CL FL HCGL MCGL LCGL BW BL UL SL SWL Total
Area in
2005
CL 12 1 0 0 13
FL 2266 5 6 3 0 2280
HCGL 17 13704 522 180 6 73 1 127 14631
MCGL 37 962 28105 811 36 353 6 79 30388
LCGL 6 242 1255 35787 138 1219 51 54 38751
BW 0 24 230 148 9107 0 644 101 26 10280
BL 1 1 0 3 0 5
UL 3 39 325 1570 511 1 32104 220 12 34783
SL 2 180 180 94 267 4480 7 5210
SWL 8 414 198 86 40 47 21 5143 5957
Total Area
in 1975
12 2336 15391 30822 38766 9932 4 34707 4879 5450
*CL=Cultivated land; FL=Forest land; HCGL=High coverage grassland; MCGL=Moderate coverage grassland;
LCGL=Low coverage grassland; BW=Bodies of water; BL=Building land; UL=Unused land; SL=Sandy land;
SWL=Swamped land.
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480

In detail, during 1975-2005, the loss in high
coverage grassland was mainly converted to low
coverage grassland, moderate coverage grassland,
and swamped land, conversion area were 242, 962,
and 414 km
2
, respectively. The gain of high
coverage grassland was also mainly converted from
low and moderate coverage grassland to swamped
land, the conversion area was 522, 180, and 127 km
2
,
respectively, but the gain areas were all less than the
loss areas, which resulted in a general decreasing
tendency of high coverage grassland. The gain and
loss area of swamped land was 814 km
2
and 306
km
2
, respectively, and which mostly converted with
grassland. The gain of sandy land was primarily
converted from unused land, moderate and low
coverage grassland, the area was 267, 180, and 180
km
2
, respectively. In addition, the decrease of forest
land was mainly converted to high and moderate
coverage grassland, and swamped land.
4 DISCUSSION
The change of vegetation is the result of drought in
the shallow soil of the habitat, and which is greatly
controlled by temperature and precipitation (You et
al., 2014). Although some study points out that
overgrazing will cause the degradation of alpine
ecosystems by ruining vegetation coverage (Song et
al., 2009; Wang et al., 2008), climate warming is
taken as the most close driving factors of grassland
degradation in the Tibetan Plateau (Wang et al.,
2006; Shen et al., 2011; Gao et al., 2014). So we
analyzed changes in the temperature and
precipitation in the SRYR based on meteorological
data from 1975 to 2005 (Hu et al., 2012).
The climate in the SRYR got warmer and wetter
between 1975 and 2005. During this period, the
mean annual precipitation increased at a rate of 21
mm per decade. The increase of precipitation would
helpful for vegetation growth and increase soil
moisture, and would thereby get rid of of grassland
degradation and desertification, even resulted in the
extension of swamped land. In the meantime, the
annual temperature increased at a rate of 0.47 °C per
decade, and the increase rate accelerated in the last
15 years (at rate of 0.71 °C per decade). The air
temperature increase rate are much greater than the
global increase rate (0.03 to 0.06 °C per decade)
(Folland et al., 2002).
Increasing temperature has been taken as the key
climatic factor responsible for land degradation (Gao
et al., 2014) and aeolian desertification Tibetan
Plateau (Xue et al., 2009). In the SRYR, permafrost
has reduced and unstable permafrost has increased
due to temperature increase since 1980s (Fang et al.,
2011). Permafrost plays an crucial role in
maintaining the alpine vegetation in the Tibetan
Plateau (Yang et al., 2004), but the degradation of
vegetation can enhance the effects of climate change
(Wang et al. 2012) . This barrier also leads to soil
organic matter accumulation (Wang et al. 2006).
Aeolian desertification in the SRYR always occurs
with the degradation of vegetation which protects
the underlying sediments from wind blowing.
Therefore, these factors which damaged the
vegetation cover are likely to lead to aeolian
desertification. So, it is concluded that the increase
of air temperature was the key factor responsible for
the eco-environmental degradation in the SRYR.
5 CONCLUSIONS
This study conducted in the center of sparsely
populated Tibetan Plateau advocates that multi-
temporal satellite images play a vital role in
quantifying spatial and temporal variations of land
cover which is otherwise not possible to attempt
through conventional mapping. The results showed
grassland and unused land were the main land cover
types in the SRYR, accounting for 58.9 and 24.4 %
of the total study area in 2005, respectively. A total
of 11,588 km
2
（8.1 % of the total study area）land
cover changed during 1975-2005. Land cover
change was mainly characterized by grassland
degradation, sandy and swamped lands expansion.
As the mean annual temperature increased and the
increasing rate accelerated during1990-2005,
resulted in grassland degradation and sandy land
increase. Air temperature rise, combined with the
dry, cold, and windy climate of the SRYR appear to
be the driving forces of the land cover changes.
ACKNOWLEDGMENT
We are grateful for the financial support provided by
the Opening Fund of Key Laboratory for Land
Surface Process and Climate Change in Cold and
Arid Regions, Chinese Academy of Sciences (Grant
N. LPCC2017008), Opening Fund of Key
Laboratory of Desert and Desertification, Chinese
Land Cover Change in Response to Climate Variation in the Source Region of the Yangtze River (SRYR), Central Tibetan Plateau
481

Academy of Sciences (Grant N. KLDD-2017-005),
and the Ministry of Science and Technology of the
People's Republic of China (2013CB956000).
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