Vol.2, No.2, 86-93 (2011)
doi:10.4236/as.2011.2 2013
C opyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
Agricultural Sciences
Soil reinforcement by a root system and its effects on
sediment yield in response to concentrated flow in the
loess plateau
Peng Li1*, Zhanbin Li1,2
1School of Water Resources and Hydroelectric Power, Xi’an University of Technology, Xi’an, China;
*Corresponding Aut h o r : [e-mail]
2Institute of soil and Water Conservation, Chinese Academy of Sciences, Ministry of Water Resources, Yangling, China.
Received 3 January 2010; revised 1 March 2011; accepted 23 March 2011.
ABSTRACT
The import ance of root s in soil conse rvation has
long been underestimated due to a lack of sys-
tematic studies conducted to evaluate root dis-
tribution patterns and their effects on soil ero-
sion. Current knowledge regarding root morp-
hology and it s impact on soil erosion by water is
limited; therefore, detailed analysis of the role
that root systems play in controlling soil ero-
sion is needed. In this study, stratified runoff sc-
ouring at different soil depths in the field was
conducted in a grassland area. The results indi-
cated that both root biomass and soil water-
stable aggregates decreased as soil depth in-
creased at a ll three sites, while there was almost
no change in soil bulk density at 1.3 g/cm3. Se-
diment yields under different runoff discharge
at different sites showed similar trends, and the
sediment yield increased as the soil depth in-
creased at all three sites. Further analysis re-
vealed that close relationships existed between
root biomass and the amount of water-stable
aggregates and soil organic matter content, and
that these factors greatly influenced soil ero-
sion. Based on the data generated by the exper i-
ment, equations describing the relationship be-
tw een sediment production at different soil depths
and root biomass were determined.
Keyw ords: Root; Soil Properties; Soil Erosion; Se-
diment Yield; Loess Plateau
1. INTRODUCTION
The Loess Plateau is one of the most eroded areas in
the world, and the resistance of loess to erosion forces
has attracted a great deal of attention from researchers. A
study conducted by Zhu [1] revealed that the low resis-
tance of loess was related to its unique deposition pat-
terns during its formation, and that it showed greatly
improved resistance when vegetation was present. Due
to the differences in soil properties across the profile,
soil erosion exhibits various patterns, and these patterns
tend to be more complex when vegetative coverage and
root systems exist [2-4]. Because numerous studies [5-9]
evaluating the impact of vegetation characteristics on
soil erosion have been conducted, it is often assumed
that all aspects of vegetation have been studied. How-
ever, although many studies have investigated the effects
of plant components such as leaves, stems, organic mat-
ter, roots and exudates, on soil erosion, attention has
predominantly been paid to the effects of the above-
ground biomass on runoff hydraulics and soil erosion
[5,10,11]. Conversely, systematic root studies are lacking,
primarily due to difficulties in direct observation of their
effects [12]. Despite this lack of information, a few stu-
dies have verified that roots played a crucial role with
respect to the effects of rainfall and runoff on soil ero-
sion [3,4,9]. The presence of roots in soil provides me-
chanical reinforcement; therefore, their presence is re-
garded as one of the most important contributions of
vegetation to soil stab ility [11,13,14].
The reinforcement of soil resistance to erosion by
plant roots can be attributed to two aspects. First, roots
and root remnants physically bind soil p articles, forming
mechanical barriers to soil and water movement [15].
Major parameters influencing the mechanical influence
of roots include root diameter, degree of bifurcation,
appearance of root hairs, friction between roots and soil,
and root system distribution [16]. Second, roots and root
remnants excrete binding agents and form a food source
for microorganisms that, in turn, produce other organic
bindings [17,18]. These bindings increase the amount of
stable soil aggregates over the long term, thereby reduc-

P. Li et al. / Agricultur al Sciences 2 (2011) 86-93
Copyright © 2011 SciRes. Openl y accessible at http:// www. scirp.o rg/journal/AS/
87
ing soil erodibility [19]. Of these two asp ects, the first is
essential with respect to soil erosion by concentrated
flow.
Several publications [3,4] describing the influence of
roots on soil erosion by runoff have emphasized the need
for further research in this area. To determine the effects
of root systems on soil erosion quantitatively and to re-
veal the mechanism of rill and gully development as
well as their relationship to root biomass distribution,
soil properties, and sediment yield, it is necessary to
study these relationships across soil profiles under field
conditions. In this study, ru noff scouring at different soil
depths was conducted to investigate the vertical changes
in soil resistance to runoff erosion forces. In addition,
both vertical root distribution and related soil properties
were analyzed to demonstrate the relationships among
those parameters.
2. MATERIALS AND METHODS
2.1. Site Conditions
The experimental sites are located in Wangdong Wa-
tershed of the Changwu Field Experimental Station of
the Institute of Soil and Water Conservation (ISWC),
Chinese Academy of Sciences (CAS). The elevation of
this area ranges from 950 m to 1225 m. The area is sub-
jected to a warm temperate c ontinental seasonal climate,
with an average annual temperature of 9.1˚C. The annual
rainfall in the area is 584.1 mm, most of which is con-
centrated between July and September. The main soil
type on most sites is loess, with a clay (<0.01 mm) con-
tent of 25%.
The dominant species on most slopes are perennial
herbacious grass species of Stipa bungeana and Bothri-
ochlon ischaemum, with similar coverage and biomass.
Runoff plots on different sites were not differentiated
and were considered to be in th e same condition for run-
off scouring (Table 1).
2.2. Setting-Up Runoff-Scouring Plots at
Different Soil Depths
Zhou Peihu [1] and Jiang Dingsheng [20] developed
runoff scouring in fields in loess regions for evaluation of
soil anti-sco urability. This tec hnique is considered to be a
good technology because there is no disturbance of local
soil, vegetation, or topography. This technology was em-
ployed in our study during the growing season of 2002
with a runoff scouring plot size of 1 × 4 m. Twenty-four
hours after scouring of the soil surface, sub-surface soil of
0~5 cm was removed carefully by hand, and runoff with
the same former runoff discharge was conducted again.
After 24 hours, the next sub-surface layer of soil of 5~10
cm was removed and subjected to similar runoff scouring.
This process was repeated until scouring was conducted at
soil depths of 5, 10, 15, 20, 25, 30, 40, and 50 cm (Figure
1). The runoff volume and sediment yield were measured
each minute during the application of runoff.
2.3. Root Biomass Investigation
The soil drilling method was applied for the root in-
vestigation. For each runoff plot, eight points were dis-
tributed evenly on both sides (Figure 2) of the selected
plot. Root samples from each 10 cm layer were collected
and brought back to the laboratory and dried in an oven
at 85˚C for 24 h to measure the biomass. The biomass
density was calculated using the following equation:
Root density (RD) of certain layer (g/m3) was calcu-
lated as follows:
12
1
n
i
m
RD iRh



 (1)
where R = the radius of the soil auger (3.4 cm); h = the
Table 1. General conditions of runoff scouring plots by layers.
Plot
No Runoff discharge (L/min) Gradient (º) Cover Upper part bio-
mass (g/m2) Bulk density
(g/cm3) Exposition Position on slope Location
1 6.5 20 0.86
216.21 1.28 Southern Upper
2 8.5 20 0.81
200.77 1.25 Southern Upper
3 10.5 20 0.82
206.59 1.23 Southern Upper
4 12.5 20 0.81
208.55 1.24 Southern Upper
5 14.5 20 0.85
213.74 1.27 Southern Upper
HBY
6 10.5 25 0.82
212.67 1.27 Southern Middle
7 12.5 25 0.8
209.55 1.21 Southern Middle
8 14.5 25 0.81
209.53 1.29 Southern Middle
TSW
9 10.5 8 0.82 211.69 1.28 Southern Bottom
10 12.5 8 0.82 210.70 1.24 Southern Bottom
YJS
Note: HBY, TSW, YJS indicate the Huangbaiwa, Tongshuwa, and Yuejiashan sites, respec tively.

P. Li et al. / Agricultur al Sciences 2 (2011) 86-93
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
88
Figure 1. Cutaway view of runoff
scouring plots on the soil profile.
P
o
in
t
o
f r
oot
sa
m
p
lin
g
50
400cm
Figure 2. Sketch map of root sampl-
ing on runoff scouring plot.
thickness of the soil layer (10 cm); m = the root weight;
and i = the number of sampling points
Soil properties related to soil erosion such as the soil
organic matter content, water-stable aggregate content
and soil bulk density were also measured.
3. RESULTS AND DIS CUS SIONS
3.1. Vertical Root Biomass and Soil
Properties
The vertical root biomass distributions on the three
sites showed a similar decrease as soil depth increased
(Figure 3). Root biomass was concentrated in the sur-
face soil, after which it decreased to less than 0.2 kg/m3
in soil below a depth of 40 cm. There was no significant
difference in the root biomass at the same soil depth at
different sites, indicating that root distribution was uni-
form at the same depth among sampling points. There-
fore, the experimental conditions can be considered to be
the same for all sites. The distribution patterns of th e soil
organic matter content were also similar at the three sites
(Figure 4). The soil organic matter content decreased as
the soil depth increased, and there was no obvious dif-
ference in soil organic matter content in deep soil when
compared at the same soil depth among sites.
As shown in Figure 5, the results of soil water-stable
aggregates indicate that the aggregate content decreased
as the soil depth increased. In addition, the aggregate
content was almost the same at all three sites. Analysis
0
0.2
0.4
0.6
0.8
1
1.2
10 30 50 70 90
soil de pt h ( c m)
root biomass (kg/m3)
HBY
YJS
TSW
Figure 3. Root biomass distribution in natural
grassland and abandoned lands of different years.
0
5
10
15
10 30 50 70 90
soil depth (cm)
SOM (g/kg)
HBY
TSW
YJS
Figure 4. Vertical soil organic matter distribution
patterns.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
020406080100120
soil de pth ( cm)
aggregate content (%)
HBY
TSW
YJS
Figure 5. Vertical distribution patterns of soil aggregate
content.
of the aggregate class distribution (Figure 6) revealed
that there was little difference in content among small
diameter classes of aggregates, but that large differences
existed among aggregates with large diameter classes
(2～5 mm and 1~2 mm). Soil bulk density, which is an
important factor influencing soil erosion, was measured,
and the results showed that soil bulk density varied
slightly as the soil depth increased (Figure 7). However,
the soil bulk density in the surface soil was almost the
same (1.3 g/cm3) at all three sites.
20 cm 30 cm
50 cm
Point of root sampling
root biomass (kg/m3)
soil depth (cm)
soil depth (cm)
aggregate content(%)
50
400 cm

P. Li et al. / Agricultur al Sciences 2 (2011) 86-93
Copyright © 2011 SciRes. http://www.scirp. org/journal/AS/
89
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
020406080100 120
0
100
200
300
400
500
600
700
800
900
0 24 6 810121416
5c m
15c m
40c m
50c m
sediment yi eld (g/min)
Openly accessible at
soil de pth (cm)
aggregate co ntent (%)
>5mm
5-2mm
2-1mm
1-0.5mm
0.5- 0.25mm
Figure 6. Vertical distribution patterns of soil aggregate
content in different classes on HBY.
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
1.4
1.45
0 20406080100120
soil depth (cm)
bulk density (g/cm
3
)
HBY
TSW
YJS
Figure 7. Vertical distribution patterns of soil b ulk density.
3.2. Sediment Yield Processes at Different
Soil Depths under Different Runoff
Discharges and Slope Gradients
To avoid confusion, only sediment yield processes at
soil depths of 5 cm, 15 cm, 40 cm, and 50 cm are illus-
trated in the figures. As shown in Figure 8, the sediment
yield decreased with time at all sites and tended to be
stabilized two minutes after beginning the experiment.
The high sediment yield in the beginning was the result
of soil disturbance caused by soil division in the experi-
ment.
Sediment yield processes under different runoff dis-
charges at different sites demonstrated similar trends
(Figure 8 and Table 2), and the sediment yield increased
as soil depth increased at all three sites. Specifically,
sediment yield on surface soil was similar at these sites.
However, the yield increased sharply at soil depths over
30 cm, and this change was apparently closely related to
runoff discharge and slope gradient. Considering the root
distribution pattern, it can be concluded that, on surface
soil layer, the effect of the root system on sediment yield
was dominant, but that this effect decreased as the soil
depth increased. When the soil depth was greater than 40
time (min)
60c m
HBY—(10.5 L/min)
0
50
100
150
200
250
300
350
400
450
500
024681
time (min)0121416
sediment yield (g/min)
5c m
15c m
40c m
50c m
YJS—(10.5 L/min)
0
100
200
300
400
500
600
700
800
0246810121416
ti me (min)
sediment yield (g/min)
5cm
15cm
40cm
50cm
TSW(25˚)—(10.5 L/min)
Figure 8. Sediment yield process at different depth and sites.
cm, the effect of the root system on soil properties, and
consequently on sediment yield, was especially limited
due to its reduced distribution in deeper soil. As a resu lt,
sediment yield tended to increase as the runoff discharge
and slope gradient increased. Fluctuations in sediment
yield can be interpreted by the existence of animal holes
and biopores of roots and their r emnants.
During the runoff scouring, changes in th e so il ero sion
forms were focused on. Sheet erosion occurred on the
surface soil layer; however, as the soil depth increased,
soil erosion holes appeared on the slope, and their size
and number increased with depth. At a depth of 40 ~ 50
cm, these erosion holes tended to be connected, and
sheet erosion tended to transform into rill erosion, indi-
＞5 mm
5 - 2 mm
2 - 1 mm
1 - 0.5 mm
0.5 - 0.25 mm
soil depth (cm)
5 cm
15 cm
40 cm
50 cm
sediment yield (g/min)
60 cm
5 cm
15 cm
40 cm
50 cm
time (min)
sediment yield (g/min)
time (min)
5 cm
15 cm
40 cm
50 cm
sediment yield (g/min)
time (min)

P. Li et al. / Agricultur al Sciences 2 (2011) 86-93
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
90
Table 2. Vertical sediment production on different slopes and in response to different runoff discharge.
Soil depth (cm)
Location Runoff discharge
(L/min) 0-5 5-10 10-15 15-20 20-25 25-30 30-40 40-50 50-60
12.5 13.14 25.06 31.68 - 37.73 37.84 46.00 59.16 -
YJS 8º 10.5 11.27 20.81 23.87 - 34.73 34.05 38.90 50.84 -
6.5 19.48 18.23 24.81 25.27 25.73 28.14 33.48 62.90 -
8.5 14.24 20.67 12.46 18.13 23.81 16.80 65.71 111.53 -
10.5 16.47 25.17 21.00 36.86 23.24 65.06 84.91 129.91 156.19
12.5 22.47 27.25 31.94 69.32 53.99 80.94 161.42 255.79 -
HBY 20º
14.5 19.20 24.09 25.28 26.46 40.08 114.61177.14 271.77 -
10.5 15.91 19.57 22.50 39.67 111.83 118.42134.43 143.03 -
12.5 22.30 29.67 39.86 71.33 98.93 130.44135.39 149.51 - TSW 25º
14.5 18.03 25.18 45.39 80.33 107.62 133.19151.42 179.71 -
Note: There was no runoff scouri ng on the soil layers with “-“due to poor control when separating layers.
cating a decrease in the resistance of soil to runoff
scouring. Notably, there were some very fine roots
present in these erosion holes, suggesting that not all
roots improve soil resistance to runoff scouring.
3.3. Relationship between Root Biomass
and Soil Properties
As main bridges for communication between mate-
rial and energy, ecological and physiological features
of the root system had a deep impact on amelioration
and improvement of soil properties, especially those
properties related to soil erosion. According to some
former studies, the main soil properties related to ero-
sion, including soil organic matter and water stable
aggregate content, were closely related to the distribu-
tion of root systems. In this study, the relationships
among root systems, soil organic matter and aggregate
content were established based on experimental data.
As shown in Figure 9, as the root biomass in-
creased, the soil organic matter content or content of
soil aggregates (1 ~ 2 mm) increased logarithmically.
The large data error that was observed may indicate
that these properties in surface soil were greatly in-
fluenced by human activities, such as fire, grazing,
trampling, etc., as well as by natural factors such as
rainfall, freezing and thawing. The relationship be-
tween root biomass and soil properties in deep soil
layers tended to be more significant, especially in
areas in which the root density was lower than 0.2
g/cm3. Furthermore, the relationship between root and
soil properties was not linear, indicating that the exis-
tence of root biomass could only improve soil to a
certain level.
3.4. Relationship between Sediment Yield,
Root Biomass and Soil Properties
The improvement of soil properties and soil resis-
tance to runoff can be attributed to a well-developed
root system. As shown in Figures 10-12, there were
close relationships between sediment yield and root
biomass, soil organic matter content or content of
water-stable aggregates. Thus, further consideration
must be given to selecting indexes to reflect the ef-
fects of vegetation on soil erosion.
As the main source of energy and material in soil,
the root system radically reflects the improvement of
soil properties by vegetation, especially which of
herbaceous vegetation with root systems primarily
composed of fine roots. Those roots are more easily
transformed into soil organic matter due to their
shorter fibers; therefore, it is rational to select root
biomass as the main index to reflect the effects of
vegetation on sediment yield. As shown in Figure 11,
the sediment yield per unit of runoff discharge de-
creases as the root biomass density increases, indicat-
ing that root biomass is effective at improving soil
resistance to soil erosion forces. Following data anal-
ysis, the following equation describing the relation-
ship between sediment production at different soil
depths and root biomass was determined:
1
ln
Yab x 
where Y is the sediment yield at different soil depths,
x is the root biomass, a and b are constants. The si-
mulated results (Table 3) indicated that this fitting
equation reflected the relationship between the root
system and sediment yield well under different runoff
discharges. As shown in Table 3, it is clear that the
value of a and b decreased as the runoff discharge
increased, implying that their reciprocal values may
be related to soil erodibility.
When the root biomass density was greater than 0.2
kg/m3, the effects of root biomass on sediment yield
reduction were remarkable. In addition, when the root

P. Li et al. / Agricultur al Sciences 2 (2011) 86-93
Copyright © 2011 SciRes. Openl y accessible at http:// www. scirp.o rg/journal/AS/
91
y = 1.8489Ln(x) + 11.905
2 = 0.6451
0
2
4
6
8
10
12
14
16
00.20.4 0.6 0.8
oot biomass(kg/m3
SOM (%)
R
r)
y = 0.9362Ln(x) + 4.775
4
R2 = 0.7011
0
1
2
3
4
5
6
00.20.4 0.6 0.8
root biomass(kg/m3)
soil aggregate 1<D<2mm (%)
Figure 9. Relationship between root biomass and
soil properties.
0
0.005
0.01
0.015
0.02
0.025
0.03
00.2 0.4 0.6 0.8
root biomass (kg/m3)
sediment yild (kg)
6.5l/min
8.5l/min
10.5l/min
12.5l/min
14.5l/min
Figure 10. Relationship between sediment yield and root
biomass.
0
0. 00 5
0.01
0. 01 5
0.02
0. 02 5
0.03
024
water s t abl e ag gregate (%)
sediment yield (kg)
6
6. 5l/mi
n
8. 5l/min
10. 5 l/min
12. 5 l/min
14. 5 l/min
Figure 11. Relationship between sediment yield and water
stable aggregate content.
0
0.005
0.01
0.015
0.02
0.025
0.03
46810121
SOM (%)
sediment yield (kg)
4
6.5l/min
8.5l/min
10.5l/min
12.5l/min
14.5l/min
Figure 12. Relationship between sediment yield and
soil organic matter conte n t.
0
0.0005
0.001
0.0015
0.002
0.0025
00.2 0.4 0.6 0.8
ro ot bio ma ss density (kg/m3)
sedim ent yield per r uno ff dis charge
Figure 13. Relationship between root biomass and
sediment yield per unit of runoff discharge.
Table3. Determination of the constants of a and b in the
equation.
6.5 L/min8.5 L/m in 10.5 L/m i n 12.5 L/min14.5 L/min
a 547.8126411.9401 338.4305 226.8418200.5907
b 125.8726 92.8135 78.6954 53.084849.8790
Standard Error0.0005 0.0005 0.0006 0.0008 0.0009
Coefficient 0.9817 0.9893 0.9956 0.9933 0.9958
biomass distribution was below 0.2 kg/m3, there was a
linear relationship between root biomass and sediment
yield.
Selection of appropriate root indexes has long been
the subject of debate. In studies related to root physi-
ology and ecology, root length and surface area have
been chosen as indexes because they are directly re-
lated to the area in which the root and soil environ-
ment touch and they reflect the physiological func-
tions of the root in the processes of vegetation im-
provement. The results of the present stud y imply that
there is an intrinsic relationship among the root, soil
organic matter and water-stable aggregates, and that
root biomass turnover is the main reason for the im-
provement of soil organic and water-stable aggregates.
Therefore, these findings indicate that root biomass is
a better index than other root indexes in studies re-
lated to soil erosion.
y = 1.8489 Ln( x) + 11.905
R2 = 0.6451
root biomass (kg /m3)
root biomass (kg /m3)
y = 0.9362 Ln( x ) + 4.7754
R2 = 0.7011
soil agg
r
egate 1 ＜ D ＜ 2 mm (%)
root biomass density(kg/m3)
root biomass (kg /m3)

P. Li et al. / Agricultur al Sciences 2 (2011) 86-93
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
92
In addition, although there were herbaceous grass
roots distributed in deep soil, there were also small,
fine roots in the erosion holes. These findings indicate
that not all the roots effectively improve soil resis-
tance to erosion. Using root biomass as an index for
describing the relationship between vegetation and
erosion not only includes non-significant factors such
as fine roots, but, more importantly, may undermine
the significance of root length and surface area.
4. CONCLUSIONS
Many publications have discussed the impact of
vegetation on soil erosion and reported that the influ-
ence of plants is mainly attributed to the aboveground
biomass. Indeed, the importance of belowground bio-
mass with respect to soil erosion by water can easily
be neglected. In this study, systematic investigations
of the root distribution, soil properties, and sediment
yield were conducted to reveal the relationships
among these factors. Based on the experiments con-
ducted in the field, the following conclusions can be
reached.
Runoff scouring of different soil depth indicated
that, because of the difference in root biomass distri-
bution in the soil profile, there was a remarkable dif-
ference in sediment yield, which emphasized the im-
portance of reinforcement of roots in soil.
There was also a close relationship between root
biomass and soil properties, including soil organic
matter content and content of water stable aggregates.
As the main source of material and energy, root bio-
mass was selected as the main index to determine the
effects of vegetation on sediment yield. The sediment
yield by unit runoff discharge decreased as the root
biomass increased. A root density of 0.2 g/m3 was
found to be the critical value for the sediment yield
patterns.
5. ACKNOWLEDGEMENTS
This article was financially supported by the national natural
scientific foundation (No: 41071182). In addition, the authors
would like to express their appreciation to the staff of Mr. Shen
Mingyun and Mr. Zheng Liangyong for their useful suggestions and
technical assistance during the study.
REFERENCES
[1] Zhou, P. and Wu C.L. (1993) Researches on the me-
thods of soil anti-scourability on Loess Plateau. Jour-
nal of Soil and Water Conservation (in Chinese). 7,
29-34
[2] Gyssels, G. and Poesen, J. (2003) The importance of
plant root characteristics in controlling concentrated
flow erosion rates. Earth Surface Processes and
Landforms, 28, 371-384 doi:10.1002/esp.447
[3] Ghidey, F. and Alberts, E.E. (1997) Plant root effects
on soil erodibility, splash detachment, soil strength,
and aggregate stability. Transactions of the American
Society of Agricultural Engineers, 40, 129-135.
[4] Li, Y., Zhu, X.-M. and Tian, J.-Y. (1991) Effective-
ness of plant roots to increase the anti-scourability of
soil on the Loess Plateau. Chinese Science Bulletin, 36,
2077-2082.
[5] Morgan, R.P.C. (1995) Soil Erosion and Conservation.
2nd edition, Longman Group, Harlow.
[6] Carroll, C., Merton, L. and Burger, P. (2000) Impact
of vegetation cover and slope on runoff, erosion, and
water quality for field plots on a range of soil and
spoil materials on central Queenland coal mines. Aus-
tralian Journal of Soil Research, 38, 313-327.
doi:10.1071/SR99052
[7] Hoffmann, L. and Ries, R.E. (1991) Relationship of
soil and plant characters to erosion and runoff on pas-
ture and range. Journal of soil and water conservation,
46, 143-147
[8] Loch, R.J. (2000) Effects of vegetation cover on run-
off and erosion under simulation rain and overland
flow on a rehabilitated site on the Meandu Mine, Ta-
rong, Queenland. Australian Journal of Soil Research,
38, 299-312. doi:10.1071/SR99030
[9] Li, P., Li, Z.B. and Zheng, L.Y. (2002) Advances in
researches of the effectiveness for vegetation con-
serving soil and water. Research of Soil and Water
Conservation (in Chinese), 9, 76-80.
[10] Thornes, J.B. (1987) The palaeoecology of erosion. In
Landscapes and Culture. In: Wagstaff, J.M. Ed. Basic
Blackwell, Oxford, 37-55.
[11] Morgan, R.P.C. and Rickson, R.J. (1995) Slope Stabi-
lization and Erosion Control: A Bioengineering Ap-
proach. Chapman and Hall, Taylor & Francis, Lon-
don.
[12] Jansen, R.C. and Coelho Netto, A.L. (1999) Root sy-
stems distribution and functions in a mountainous
tropical rainforest environment. Geomorphic Re-
sponses to Vegetation Changes: Problems and Reme-
dial Work. Proceedings of the International Geo-
graphical Union, Earth Surface Processes and Land-
forms, John Wiley & Sons, Ltd, 28, 371-384.
[13] Greenway, D.R. (1987) Vegetation and slope stability.,
In: Anderson, M.G. and Richards, K.S, Eds., Slope
Stability, John Wiley & Sons, Chichester; 187-230.
[14] Waldron, L.J. and Dakessian, S. (1981) Soil rein-
forcement by roots: Calculation of increased soil shear
resistance from root properties. Soil Science, 132,
427-435. doi:10.1097/00010694-198112000-00007
[15] Tengbeh, G.T. (1993) The effect of grass roots on
shear strength variations with moisture content. Soil
Technology, 6, 387-295.
doi:10.1016/0933-3630(93)90017-9
[16] Abe, K. and Ziemer, R.R. (1991) Effect of tree roots
on shallow-seated landslides. USDA Forest Service
General Technical Report, 22, 95-108.
[17] Reid, B.J. and Goss, M.J. (1987) Effect of living roots
of different plant species on the aggregate stability of
two arable soils. Journal of Soil Science, 32, 521-541.
doi:10.1111/j.1365-2389.1981.tb01727.x

P. Li et al. / Agricultur al Sciences 2 (2011) 86-93
Copyright © 2011 SciRes. http://www.scirp. org/journal/AS/Openly accessible at
93
[18] Cresswell, H.P. and Kirkegaard, J.A. (1995) Subsoil
amelioration by plant roots—The process and evident.
Australian Journal of Soil Research, 33, 221-239.
doi:10.1071/SR9950221
[19] Hartman, R. and De Boodt, M. (1974) The influence
of the moisture content, texture and organic-matter on
the aggregation of sandy and loamy soils. Geoderma
11, 53-62. doi:10.1016/0016-7061(74)90006-8
[20] Jiang, D.S., Fan X.K. and Li X.H. (1995) Researches
on vertical and horizontal patterns of soil anti-scour-
ablity on Loess Plateau. Journal of Soil and Water
Conservation, 9, 1-8.