SWCF of Forest in Three-Gorges of Yangtze River

doi:10.4236/gep.2014.21003

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Journal of Geoscience and Environment Protection

2014. Vol.2, No.1, 12-14

Published Online January 2014 in SciRes (http://www.scirp.org/journal/gep) http://dx.doi.org/10.4236/gep.2014.21003

OPEN ACCESS

SWCF of Forest in Three-Gorges of Yangtze River

Kang Chen

Beijing SWC Ecological Engineering Consulting Co., Ltd., Beijing, China

Email: [email protected], [email protected]

Received ********* 2014

In Qinjiagou watershed of Three-Gorge of Yangtze River, 18 indices were selected from canopy layer,

litter layer, soil layer and topography to evaluate the soil and water conservation capacities of four com-

mon plantation types by ideal point method. Results indicated that the broadleaf plantation of robur (Li-

thocrpus glabra) and Chinese gugertree (Schima superba) (LS) has the biggest soil and water conserva-

tion capacity. The rank of three other plantation types from big to small is the mixed broadleaf plantation

of sweetgum (Liguidambar formosana), Chinese gugertree and camphor tree (Cinnamomum camphora)

(LSC), the mixed broadleaf-conifer plantation of Chinese fir (Cunninghamia lanceolata), Masson pine

(Pinus massoniana) and Chinese gugertree (CPS), and the mixed Pine plantation of Chinese fir and Mas-

son pine (CP). Under the same climate and topographical condition, the broadleaf plantation has better

soil and water conservation capacity than the conifer plantation. Sensitivity analysis showed that the three

most sensitive indices are soil non-capillary porosity, soil aggregation, and soil initial infiltration rate. The

litter amount and soil properties are the most important indicators of soil and water conservation capacity

of plantations. Therefore, suitable measurements such as deep tillage should be taken to improve the

properties of soil under different plantations.

Keywords: The Three-Gorge Area; Soil and Water Conservation; Function; Soil Properties; Sensitivity

Analysis

Introduction

Soil erosion is one of the biggest environmental problems in

the Southwest region of China. Many measurements have been

taken to protect soil and water resources. Researches indicated

that various types of plantations are all able to reduce surface

runoff and soil erosion effectively (Woodward et al., 1995;

Jiang et al., 2007), and their function was affected by human

and natural disturbances (Noske et al., 2010; Uzun et al., 2011).

In the upper reaches of the Yangtze River, people have rep-

lanted most of farmlands with Chinese fir (Cunninghamia lan-

ceolata), Masson pine (Pinus massoniana), robur (Lithocrpus

glabra), sweetgum (Liguidambar formosan), camphor tree

(Cinnamomum camphora) and other tree species. Are these

plantation types suitable for reforestation, and are they helpful

to protect soil and water? The information is urgently needed to

understand soil and water conservation capacity of different

plantation types.

Methods and Materials

Study Area

Simian Mountain, belongs to the Three Gorges Reservoir

Area, is a typical case in terms of its complexity of natural en-

vironment and fragility of ecosystem in China. The soil erosion

is posing a serious threat to the ecological security and regional

sustainable development in upper reaches of Yangtze River.

The study area, Qinjiagou watershed (28˚31ʹN - 28˚46ʹN,

106˚17ʹE - 106˚30ʹE), is situated in the middle part of Simian

Mountain, Southwest of China. The forest land of Qinjiagou

watershed belongs to the upstream of Yangtze River. The alti-

tude is from 900 m to 1,500 m. Soils are mainly yellow loam

and purple soil, which is infertile, with a depth ranging from 10

to 70 cm. The representative types in Simian Mountain are

mixed forest of CP, CPS, LS, LSC. All the four plantation types

were planted in 1999, with 1 ha of LSC, CP, CPS, and 0.8 hm2

of LS. The previous shrubs were cut off before new plantations

were planted, but the litter is kept. There was no management

after the plantations were planted except irrigation in spring.

Samples Collection and Treatment

Ideal Point Method

Ideal point, a popular method for multiple objective deci-

sion-making, is objective thus avoiding large deviation due to

subjective opinion (Henry et al., 1989; Zhang et al., 2006; Ha-

gemann, 2007). That method could reduce the disturbance of

subjectivity in the course of assessment, and reflect the contri-

bution of each index to regional ecological safety more objec-

tively (Jia et al., 2006). Therefore, normalizing indices and

weighting determination was dealing with the above methods.

Sensitivity Analysis

Sensitivity analysis is necessary for evaluation (Chen, 1987;

Fan et al., 2004). The analysis will determine the certainty of

the rank of every two plantation types. Taking

as the pos-

sibly changed value of

y′

, then

( )

1**

ijjk k

yV yV

−

′+

= −

∑

(1)

()( )

ii j

k ij

TT V

yy V

−

′

∆= − =

∑

(2)

K. CHEN

OPEN ACCESS

When

min ,max

kij ij

y yy



′′

∈

, the change of

will not

induce the change of

. When

is very close to

y′

, the

original rank is not steady.

y′

is the sensitive index. If

very close to

y′

when the Δ value belongs to

[ ]

0,0.1

, it

means that

y′

is sensitive. And the lower the value is, the

more sensitivity indices are. If the numbers of sensitive indices

between two plantation types are more than 3, the rank of them

is uncertain.

Results and Discussion

Plant Investigation

In July 2009, three 20 × 20 m2 plots were established at each

plot of four plantation types in study area. The height of all

trees was measured. The number of trees in each subplot was

counted and recorded. In each 20 × 20 m2 plot, four 5 × 5 m2

subplots were established for investigation of shrub diversity.

The number and names of the different shrubs were recorded.

In each shrub plots, two 1 × 1 m2 subplots were established for

investigation of grass diversity and the names and amounts of

the different grasses were recorded. Five 1 × 1 m2 subplots

were randomly chosen in each 20 × 20 m2 plots and leaf litter

fall was sampled. A total of 15 leaf litter fall samples were

taken in each plot of every plantation type. The maximum wa-

ter capacity of litter was measured by putting leaf litter fall in

water 24 hrs.

Soil Properties

In June 2009, soil samples for physical properties measure-

ments were collected from each location of plantation types.

Five replicated soil cores for bulk soil density, total porosity

and non-capillary porosity were taken in each 20 × 20 m2 plot

along a diagonal transect. Analyses of physical soil properties

were conducted. Three composite surface soil samples were

collected from the plots of each plantation. The soil samples

were sieved to pass a 2 mm mesh and the percent of soil par-

ticles bigger than 2 mm equals the percent of gravel in the soil.

The infiltration rate (IR) of the soils was measured by using a

double-ring infiltrometer with a 22 cm outer diameter, a 10.5

cm inner diameter and a height of 25 cm (Song et al., 2007).

Organic matter of the soil was determined by an oil bath-

K2Cr2O7 titration method.

Implementing Ideal Point Method

Values of All the Indices

18 indices were selected for ideal point model. That is one of

differences from the previous research (Truman et al., 1990;

Deuchras et al., 1999). There into two indices, aspects and roots

distribution, are qualitative indices obtained by the method of

expert’s gradation according to the studies about the relation-

ship between indices and soil erosion. And the other 15 indices

values are all obtained from field measurements.

Normalization of Indices

The evaluation system is composed of 4 programs (4 planta-

tions) and 18 indices. Then, the original matrix of the evalua-

tion system is

( )

4 18

46 2.87 300.15202.7919.170.2371.096 0.049 0.186 0.397 0.085 4.53 0.1810.7536901161

702.2700.03191.82 16.820.1131.033 0.031 0.313 0.502 0.1125.04 0.3717.4238.5 501160

78 3.26 30 0.043246.94 25.430.1341.1390.097 0.238 0.484

X=0.1275.240.3537.923690 1166

55 3.83 500.2664.476.040.0691.236 0.117 0.203 0.525 0.126 5.29 0.3010.08 28.8 701170







The matrix after normalization is

( )

4 18

00.411000.7580.67710.6900.20900 0 0 00.0240.25810.9

0.75010.556 0.6980.556 0.2621010.820 0.643 0.67110.263001

10.65001110.387 0.478 0.7670.409 0.68010.9340.83310.25810.4

0.2811 0.50.407 00001 0.134 1 0.976 1 0.83301 0.5







According to entropy method, the weights of different indices were calculated.

Evaluation Results

After normalization and weights’ determination, the final matrix Y′ is as following,

( )

4 18

ij j

Yy Y

′′

= =

(1)

where

( )

4 18

is the matrix after normalization; ωj means weights of different indices.

00.016000.043 0.048 0.065 0.032 0.009000000.0010.0160.042 0.028

0.03400.06 0.0310.040 0.040 0.017 0.04700.071 0.038 0.046 0.028 0.0780.017000.031

0.045 0.02500.056 0.058 0.072 0.025 0.022 0.035 0.029 0.032 0.072 0.039 0.065

Y′=

0.065 0.016 0.042 0.012

0.013 0.039 0.03 0.02300000.046 0.009 0.047 0.070 0.042 0.06500.064 0.0210







K. CHEN

OPEN ACCESS

After normalization, the value of 18 indices all belonged to

interval [0, 1]. The maximum was the best. Therefore, the ideal program

should be composed of the maximum value of

each index as follows,

( )

0.045 0.039 0.060.056 0.058 0.072 0.0650.047 0.046 0.0710.0470.072 0.039 0.0780.0650.064 0.042 0.031

( )

0.634 0.437 0.3540.523

( )

0.202 0.1560.1210.170

Therefore, the evaluation of soil and water conservation ca-

pacity of LS is the minimum, that of CP is the maximum. The

second one is CPS, followed by LSC.

Conclusion and Suggestion

Conclusion

Soil and water conservation is one of the most important tar-

gets of eco-environment construction in Southern China. We

found that under the same condition, soil and water conserva-

tion capacity of hardwood forest is better than that of mixed

forest of hardwood and softwood, and much better than that of

conifer forest.

According to the sensitivity analysis, it showed that hard-

wood LS has the best soil and water conservation capacity

among the others. Therefore, the mixed broadleaf forest of

robur and Chinese gugertree should be the first choice when we

implement the “returning farmland to forest” policy in the

Three Gorges area.

It also showed that the soil and water conservation capacity

of CP is difficult to improve over a short time from now.

However, the soil and water conservation capacity of LS, LSC,

and CPS can be improved by taking proper managing practices.

Litter and soil layer under the forest play a very important

role in protecting soil and water. Improving the soil properties

should be taken to enhance the soil and water conservation

capacity of these plantations.

That proves that ideal point method is suitable for evaluating

forest soil and water conservation capacity. Using the ideal

point method to evaluate the capacity of soil and water conser-

vation of different forest types can avoid long-time processing

measurement, but with more objective and precise results.

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