10th Asian Regional Conference of IAEG (2015)

Analysis on Vegetation Growth Characteristics of Manas River Basin in Sinkiang

Wang Xiuyan, Liu Shaoyu, Han Shangping, liu Zhimin
Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, China
E-mail:wxiuyan9948@163.com
Abstract
Based on the field research on the characteristis of vegetation growth, soil andshallow groundwater in the Manas River Basin in Sinkiang area and the summary of theresults of relavant laboratory tests, vegetation of the Manas River Basin can be sorted into
four regions by coverage rate, namely, region with high vegetation coverage, region withmedium vegetation coverage, region with medium vegetation coverage and desert region.
Additionally, the relation between vegetation growth characteristics, the buried depth ofshallow groundwater, soil composition, moisture content and soluble salt is also analyzed
comprehensively. Through the analysis, we find that the buried depth of the groundwater isa decisive factor that influences vegetation growth characteristics of this climatic region. In
the area where the buried depth of shallow groundwater is lower than 2.5 m, vegetation
coverage may be high, especially where near rivers and lakes, but the area where the buried
depth of groundwater is higher than 5.0 m is usually desert region. The soil characteristic is
another factor that decides vegetation growth characteristics. That's to say, the soil
composition, moisture content and the content of soluble salt are also important factors that
may influence the development of vegetation. It is further pointed out that the developed
clayey soil is more favorable to the development of vegetation than the sandy soil is where
the buried depth is lower than 50 cm. In the area where the buried depth is lower than 30 cm,
whether the moisture content is higher than 10% or not is a criteria to determine whether thearea belong to high coverage area or low coverage area. In the area with buried depth lower
than 50 cm, the content of soluble salt has the largest influence on the vegetation coverage.
Key Words: Manas river basin in China, the vegetation coverage, Gound water level,
Property of soil, Content of soluble salt
1.

Introductionof the Manas River. Influenced by the weather systemof the temperature zone and the weather system of
the Arctic Ocean, this area is dry and rainless, where
the evaporation capacity is much higher than the
precipitation. As a result, the development of local
vegetation mainly relies on groundwater recharge.
Due to the combined actions of over exploitation ofshallow groundwater and the artificial interception of
surface water, the water yield of the Manas River
Basin have decreased dramatically and the regional
groundwater level have kept decreasing as well. In
addition, the hot dry climate leads to intense
evaporation,
withevaporation
capacity(1500mm-2500mm) much higher than the
precipitation (100mm-200mm) and the annual
evaporation being 10-20 times of the precipitation.
The annual temperature is 6.5 ℃ ，warm in thesummer and autumn, and cold in the spring andwinter. These climatic conditions intensify thesalination and desertization of the soil, deteriorate the

The Manas River Basin of Sinkiang in China islocated in the north slope of Tianshan Mountain andalso the southern Junggar Basin. It stretches from thewatershed in the north slope of Yilianhabierga
Mountain in the south to the Gurbantunggut Desert in
the north and from Taxi River in the east to theBayingou River in the west. Administratively, thebasin covers Manas County, Shawan County, Shihezi
City, 19 regiments, villages of the No. 8 agricultural
production division and the Xinhu regiment of the No.
6 agricultural production division. The Manas River
Basin of Sinkiang is located in the typical arid region,
where a variety of landforms exist including theaccumulative denudation landform, piedmont
alluvial-proluvial fan, floodplain terrace, marshland
in edge-spring overflow area, alluvial-proluvial plainand desert. The microrelief like floodplain terrace,
depression and marshland only exists in the two sides

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10th Asian Regional Conference of IAEG (2015)

basic habitat of plants, forcing vegetation of theManas River Basin evolves from the one that is tall,straight and dense to the one that is thin, small andsparse.
Survival of the fittest(Serafini Y V, Sud Y C.
1987; DelworthT L. 1988; Delworth T. L. andManabe S. 1988; Tsvetsinskaya E.A., et al. 2001;
Wu W, et al. 2002), it is the same way for plants. The
wild vegetation can live in the climate that is suitablefor it to survive. The development of vegetation is
directly related to the buried depth of groundwater,
the property of soil, climate factors, etc. Although,there are already some researches conducted on thevegetation ecology and climatic problems in thisresearch area, comprehensive analysis on vegetation,
the soluble salt in soil and the groundwater is notmuch.
On the basis of previous study achievements, byconducting field survey on the development ofvegetation of the Manas River Basin and the shallow
groundwater and combining the laboratory test resultson the soluble salt in soil and soil composition, thisresearch is conducted, revealing the influence offactors like the soil property in the shallow
groundwater, content of soluble salt, climaticcondition and environmental condition on vegetationin terms of variety and development. It is believedthat the region with medium vegetation coverage has
certain adjustment ability, thus it is easy for it totransform into region with high vegetation coverage.
The research result can provide scientific basis forprotection of the eco-environment of vegetation andfor the effective governance of the desert.
2.

salinization can be found occasionally. The wildlandscape is shown in Photo. 1 .

Photo. 1. Region with high vegetation coverage
The shallow groundwater in this region is buried
shallowly, with buried depth lower than 2.5 m.
(2) Region with medium vegetation coverage
For the wild vegetation region, the region withmedium vegetation coverage means the region wherethe vegetation coverage is at 30%～60%. This regionis usually located about 200m-500m far from therivers, lakes and artificial irrigation ditches. The
vegetation characteristics of this region: major plants
growing here include rose willow, Karelinia caspica,
Achnatherum splendens, Acid smartweed, Sophoraalopecuroide, etc. These plants show medium growthtrend, with height mainly at 30cm～40cm, looking
slim and fragile and some even dying up. See Photo 2.

Environment Characteristics ofVegetation

2.1 Relation between the Distribution of
Vegetation and the Depth of Groundwater
According to the survey result, this basin can bedivided into four regions, namely, region with highvegetation coverage, region with medium vegetation
coverage, region with low vegetation coverage anddesert region, of which the detailed characteristics aredescribed as below:(1) Region with high vegetation coverage
For the wild vegetation region, the region withhigh vegetation coverage means the region where thevegetation coverage is higher than 60%. This regionis usually located about 200 m far from the rivers,
groundwater seepage area, marshland and lakes. The
vegetation in this region features wide variety, dense
and strong appearance and vigorous growth trend.
The plants live here include reed, cattail, rose willow,
ulmus parvifolia, populus euphratica forest, etc. In
several regions, there also grows tall and dense
populus euphratica. On the earth's surface,

Photo. 2 Region with medium vegetation coveragefor vegetation characteristics. The salinization of thisregion belongs to moderate degree and is severer thanthat of the high coverage region. The depth of thegroundwater here is 2.5m-4.0 m. The perennial plants
with long root can draw water from groundwater andaeration zone.

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10th Asian Regional Conference of IAEG (2015)(3) Region with low vegetation coverage
The coverage rate of region with low coveragevegetation coverage is at 15%～30%. This region is
located about 500 m-1000 m far from the rivers, lakes
and artificial irrigation ditches. Plants adapted to salt
and alkali condition are growing here, including rose
willow, sacsaoul, Karelinia caspica, Alhagi
camelorum, Achnatherum splendens, Sophoraalopecuroide, suaeda salsa, etc. These plants showpoor growth trend, looking slim and weak, withheight less than 10 cm. The salinization belongs tosevere degree. The landscape is shown in Photo 3.
The buried depth of groundwater here is usually

Photo. 4 Desert region
this region is lower than 5.5 m.
2.2 Relation between Vegetation Distribution andSoil Property
The soil is the basic term for plant growth andwater is the necessary condition for creatures tosurvive. Only by absorbing water, nutrient andsunshine from the environment continuously, can thecreatures maintain their normal life activities.
Additionally, water is a necessary for plants in cellswelling, transpiration, photosynthesis as well as
absorbing and transporting nutrient. The moisture in
the soil mainly comes from climate recharge andsurrounding recharge. The content of water in the soil
is not only related to the regional climate and the soil
property, but also to the buried depth of groundwater.
The content of water in soil has decisive influence on
the development of vegetation. According to a
research, the soil that contains more water has better
water bearing capacity, where the vegetation is morediverse and the vegetation coverage is higher, as
described below:

Photo. 3 Region with low vegetation coverage

4.0m～5.5 m. The root system of most of the plants
can hardly reach to the shallow groundwater. For
example, in the research spot 04-15#, the water levelin the junction of Mahe River and Gurbantunggut(1) Region with high vegetation coverage
This region has buried depth of less than 2.5 m,
where the soil is silty clay, clayey silt and a little bit
sandy soil, appearing yellowish brown to lightgrayish brown. The water content of the soil is
medium to high, at 15%-38%, in a saturation
condition, i.e. saturability ≥ 85%.

Desert, the depth of underground water level isdeeper than 4.3m and the wetting line is 2.0 m fromthe ground and 2.3 m from the water surface. The
water here is very salty.
(4) Desert region(2) Regions with medium vegetation coverage
This region has buried depth of less than 2.5 m,
where the soil contains a certain amount of clayey
soil, mainly appearing yellowish brown to lightgrayish brown. The water content of the soil is
medium to high, at 10%-15%, in a saturation
condition, i.e. 50% ≤ saturability ≤ 85%.

The vegetation coverage of this region is lower
than 10% due to its location that it is located over1000 m away from the rivers, lakes and artificial
ditches, most of the region are in desert and Gobi
zone with little vegetation. This region suffers fromsevere salinization and desertization, as shown in(3) Regions with low vegetation coverage
This region has buried depth of lower than 2.5 m,
where the soil is mainly silty soil (i.e., silt or silty

Photo 4. The buried depth of the groundwater level of3

10th Asian Regional Conference of IAEG (2015)

vegetation grows. The region with high vegetation
coverage and the region with medium vegetation
coverage have similar content of K＋, i.e., in the areawith buried depth at 30cm-250cm, the content of K+
is lower than 0.9mmol(1/2B+)/kg soil both in theregion with high and medium vegetation coverage.
And the content of K+ is a little bit higher in themedium vegetation coverage region than in the highone. The area with the buried depth is higher than
250cm and the content of K ＋ higher than 3.2mmol(1/2B+)/kg soil belongs to desert region.

sand) with good water permeability thus easy to makewater evaporable. The ground surface is of highdegree of salinization. In the sandy soil with depth
higher than 1.50 m, the water content is 10%-15%
and thus the soil is in slightly wet condition.
(4) Desert region
The surface soil is in severe salinization anddesertization. The buried depth of this region ishigher than 1.5 m where the soil is mainly sandy soil
or Gobi gravels, with water content less than 6% andthus sees very dry. The detailed changes on relation
between vegetation distribution and water content are
shown in Fig. 1.

(2) Na+The high the Na＋ content in the soil, the lower
the vegetation coverage is. The region with highvegetation coverage and the region with medium
vegetation coverage have similar content of Na+, i.e.,in the area with buried depth at 30cm-250cm, thecontent of Na+ is lower than 57 mol(1/2B+)/kg soil.
And the content of Na+ is a little bit higher in the medium
vegetation coverage region than in the high one. The
content of Na+ in the desert is much higher than 177
mol(1/2B+)/kg soil.
(3) Ca2+
In the area with buried depth within 10cm, thecontent of Ca2+ is similar in no matter the high,medium or low vegetation coverage area. In theregion with high vegetation coverage, the content of
Ca2+ is lower than 19 mol(1/2B2±)/kg soil, but in thedesert region, the content of Ca2+ is higher than 35
mol(1/2B2±)/kg soil.
(4) Mg2+
In the area with buried depth within 2.5m, thecontent of Mg2+ is similar in no matter the high,medium or low vegetation coverage area. But in thedesert region, the content of Mg2+ is higher than
12.7/mmol (1/2B2±)/kg soil.

Fig. 1 Curves between vegetation with watercontent and depth of soil(5) CI_The high the CI_ content in the soil, the lower
the vegetation coverage is. In the area with buried
depth within 30 cm where the vegetation coverage ishigh, the content of CI_ is lower than 38
mol(1/2B2±)/kg soil. But in the desert area, thecontent of CI_ is higher than 83mo(1/2B2±)/kg soil.

2.3 Relation between Vegetation Distribution andContent of Soluble Salt
The research finds that the degree ofmineralization of ground water is higher than 5.0g/L,
thus the water belongs to SO42_- Cl_ - Na type withhigh degree of mineralization. As for the distribution
condition of water quality, the water shows increasing
mineralization from the upstream area to thedownstream area accompanied with increasing
content of SO42_ and Cl_. The mineral substance inthe shallow groundwater mainly comes from theupper soil mass. In natural condition, the degree ofvegetation coverage is determined by the content of
K+,Na+, CI_and some other ions. The distribution
characteristics are as below:(6) CO32_ and HCO3_
The high the content of CO32_ in the soil, thebetter the vegetation grows. In the regions withmedium or low vegetation coverage, the content of
CO32_; but the distribution shows little regularity. In
the desert region with buried depth within 50 cm，
the content of CO32_ approaches to 0.
The lower the content of HCO3_ in the soil, thebetter the vegetation grows. In the area with buried
depth within 30 cm, the content of HCO3_ is lower
than 1.3mol(1/2B2_)/kg soil in the high vegetation
coverage area but higher than value in the desert area.

(1) K＋The less the K ＋ in the soil, the better the4

10th Asian Regional Conference of IAEG (2015)(7)SO42_
The less the SO42-, the high vegetation coverage
is. The area with buried depth within 250 cm and thecontent of SO42_ lower than 2.2mol(1/2B2_)/kg soil
belongs to high vegetation coverage region while theone with the content of SO42 － higher than
79.0mol(1/2B2_)/kg soil is desert region.

the higher the vegetation coverage is. The area withburied depth within 250cm and the content of NO3_
lower than 1.0mol(1/2B2_)/kg soil belongs to highvegetation coverage region while the one with thecontent of NO3－ higher than 6.2mol/kg soil is desert
region.
Those ions mentioned above all decrease theircontent with the deepening of buried depth. Detailed
changes are shown in Fig. 2.

(8) NO3_
Similar with SO42_, the less the NO3_ in the soil,

Fig. 2 Curves of relationship between content of soluble salt with depth in soil

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10th Asian Regional Conference of IAEG (2015)

3.

AnalysisontheGrowthEnvironment of Vegetation

2.5 m, the vegetation coverage is high. These regions
are mainly distributed near rivers or lakes. The areawith buried depth of groundwater level lower than
5.0m belongs to desert region.

The climate is a decisive factor for why theevaporation capacity is higher than the precipitationin the Manas River Basin. The water for growth of
local vegetation is mainly recharged by groundwater.
Therefore, the growth of vegetation is not only
related to the buried depth of groundwater, but also to
the soil composition, the degree of acid and alkali of
soil, the content of soluble salt ions, etc. Anotherinfluencing factor is artificial river closure whichmakes sharp decrease of water discharge in thedownstream section and thus causes frequent cutoff
in downstream and end section of the Manas River.
These factors make the wetland near the river andlakes degrade into desert area. These deserts are notnaturally formed before, but formed under the climate
force. In the desert area shown in Photo 5, the shell(2) The water content of soil is an important factor
that influences the growth of vegetation. Whether thewater content is higher than 10% or not at the areawith buried depth at 30cm is an indicator todetermine whether the vegetation coverage is high ornot.
(3) The soil property is another key factor that
determines the growth characteristics of vegetation.
In the clayey soil area with water buried depth higher
than 50cm and where the water bearing capacity isrelatively stronger than that of the sandy soil, i.e., themoisture in this area is not easy to evaporate, thevegetation coverage is relatively higher, and the areaof this type is more favorable to vegetation growth.
(4) Then content of soluble salt in the soil is an
important factor that determines the growth vigor ofvegetation. In the research area, the content of soluble
salt ions usually decreases with the deepening ofburied depth. In the area with buried depth within 30
cm, the content of soluble salt has relatively higher
influence on the vegetation. The respective vegetation
coverage of high vegetation coverage region and the
medium one are similar, while that in the low
vegetation coverage area is much lower and that in
the desert area is the lowest.
(5) The vegetation coverage may keep changing.
Under the influence of climate or artificial conditions,such as atmospheric precipitation and artificial
irrigation, the groundwater level may rise thus toeasily improve the vegetation coverage.

Photo. 5 Desert region around the Manas Riverremains of some aquatic shellfish and snails and theroot remains of cattail and reed can be found. Thus it
can be deduced that this desert area was originallyriver or lake area. The desolate scene shown in Photo
5 seems to tell us that this area was originally a marsh
wetland and due to the decrease of groundwater level
and the dry climate, it has become the desolate desert.
4.

Acknowledgements
The authors are grateful for the financial support
from the projects of National Natural Science
Foundation of China No. 41272301 andNo.40472139.

Conclusions

To sum up, we come to the conclusions as
below:

References
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