植被对水土流失和水源涵养的影响

植被对水土流失和水源涵养的影响(Crockford

and

Richardson,

2000;

Li

et

al.,

2014;Quintonet

al.,

1997;

Janssens

et

al.,

1998;

Martin

et

al.,

2010;

Puigdefabregas,

2005;

Bochet

et

al.,

1998;

Feng

et

al.,

2012;

Lu

et

al.,

2012;

Liu

et

al.,

2018;

)Multidimensional

analysis

of

the

effects

of

vegetation

onrunoff

and

soil

lossØ

Vertical

vegetationstructures;Ø

Plant

diversity

;Ø

Vegetation

spatialdistributionEFFECTS

OF

VEGETATION

INMINIMIZING

EROSION

ü

Absorbs

the

energy

offalling

rain;ü

Removes

water

from

soil

and

transpires

it

into

the

air;ü

Roots

hold

surface

soil

andstabilize

bank

materials;ü

Helps

the

ground

to

absorb

water;ü

Slows

the

runoff

velocity

and

traps

sediment.Questions

discussed

in

this

research

:1.

How

does

the

vegetation

coverage

and

litter

coverage

influence

soil

erosion

process?

What

is

the

dynamic

process

of

soil

water

infiltration

during

rainfall?2.

The

regulation

mechanism

of

vegetation

coverage

on

soil

erosion?MethodsRunoff

bucketPrecondition

of

experimentRainfall

simulation

experimentVegetation

coverage/Litter

coverageGrass:

CarexShrub:

Twigs

of

the

CHASTE

TreeRainfallintensity:

60mm/hDuration

of

rainfall:

60minSlope：15°Measuring

experimental

indexes2MethodsControl

conditionVegetation

Coverage:

0,

25%,

50%,

75%,100%;

Litter

Coverage:

0,

50,

100,

150，200,

250g/mEffects

of

vegetation

and

litter

coverage

on

soil

erosion

processTime/minSlope

Runoff

and

Sediment

Process12001000800600400200020.0018.0016.0014.0012.0010.008.006.004.002.000.000

25%

50%

75%

100%0

10

20

30

40

50

60Time0

25%

50%

75%

100%Time0

10

20

30

40

50

601100100090080070060050040030020010000

5

10

15

20

25

30

35

40

45

50

55

60

650g50g100g150g200g250gFig.

1

Dynamic

changes

of

surface

runoff

rate

and

sediment

rate

under

different

vegetation

coverage

conditionsFig.

2

Dynamic

changes

of

surface

runoff

rate

and

sedimentrate

under

different

Litter

coverage

conditionsInfiltration

rate(mm/min)Soil

moisture

incrementSoil

moisture

incrementInfiltration

rate(mm/min)Effects

of

vegetation

and

litter

coverage

on

soil

erosion

processSlope

Soil

Infiltration

Process141210864200

25%

50%

75%

100%0

10

20

30

40

50

60

70

80

90Time(min)10.009.008.007.006.005.004.003.002.001.000.000g

50g

100g

150g

200g

250g0

10

20

30

40

50

60

70

80

90Time/min1.201.000.800.600.400.200.000

25%

50%

75%

100%0

10

20

30

40

50

60Duration

of

rainfall(min)1.000.800.600.400.200.000g

50g

100g

150g

200g

250g0

10

20

30

40

50

60Time

(min)Fig.

3

Dynamic

changes

of

Soil

moisture

increment

and

soil

infiltration

rate

under

different

vegetation

coverage

conditionsFig.

4

Dynamic

changes

of

Soil

moisture

increment

and

soil

infiltration

rate

under

different

Litter

coverage

conditionsEffects

of

vegetation

and

litter

coverage

on

soil

erosion

processØ

With

the

increment

of

vegetation

and

litter

coverage,

soil

moisture

increased

and

the

surface

runoff

rate

decreased.Ø

It

shows

that

more

water

was

used

for

infiltration,

and

thus

increasedsoilmoisture

with

the

increment

of

vegetation

and

litter

coverage.Ø

Vegetation

and

litter

coverage

can

achieve

good

water

storage

effect.Effects

of

vegetation

coverage

on

hydrodynamic

parametersnmEffects

of

vegetation

coverage

on

runoff

velocityTal.

1

Fitted

Equations

of

Slope

Runoff

Velocity

withDifferentVegetation

CoverageV=K·J

·qFig.

5

Variation

of

mean

velocity

of

slopeflow

with

vegetation

coverageK

is

the

coefficient

related

to

the

roughness

of

slope

surface.p

With

the

increment

of

vegetation

coverage,

the

K

value

decreased,

It

indicates

that

the

rougher

the

slope

was,

the

smaller

the

V

value

was.Effects

of

vegetation

coverage

on

hydrodynamic

parametersEffects

of

vegetation

coverage

on

runoff

morphology

andresistance

characteristics

Tal.

1

Characteristics

of

hydrodynamic

parameters

ofslope

runoff

under

different

coverageLaminar

flowSlow

flowFig.

6

Resistance

Coefficient

(f)

of

Slope

Flow

under

Different

Vegetation

Coverageu

Vegetation

coverage

can

reduce

the

runoff

velocity

on

the

slope,

alleviate

the

runoff

morphology

and

increase

the

surface

resistance

coefficient.u

Vegetation

can

greatly

increase

the

roughness

of

slopes.

With

the

increment

of

vegetation

coverage,

the

resistance

of

runoff

on

slopes

becomed

larger

and

larger.

The

more

energy

of

runoff

was

used

to

overcome

resistance,

the

less

energy

was

used

for

erosion

and

sediment

transport,

the

weaker

soil

erosion

was.Effects

of

vegetationcoverage

on

soil

shearstrength

and

anti-erodibilityTal.2

soil

internal

friction

angle

(φ),soil

cohesion

force

(C)

and

shear

strength(τf)

on

different

vegetation-covered

slopesFig.

7

Fully

automatictriaxial

compressioninstrumentu

It

shows

that

cohesion

force

(C)

and

internal

friction

angle(φ)

increased

significantly

of

BE,

IE,

AE

compared

with

BF

and

bare

land

in

all

vegetation

coverages.u

With

the

increment

of

soil

moisture

content,

the

C

and

φ

decreased,

which

indicates

that

the

soil

shear

strength

decreased.u

The

C

and

φ

decreased

after

the

experiment,

which

indicates

that

C

and

φ

were

not

only

affected

by

the

coverage

conditions,

but

also

affected

by

the

moisture

content

of

vegetation

slope.u

Vegetation

coverage

increased

the

C

and

φ

,

which

had

a

strong

effect

of

soil

consolidation

and

erosion

resistance.Subsequent

Work1.

Field

Observation

Experimentwater

balance

experimentLysimeterSystemsSap

flow（Vegetationtranspiration）Soil

waterThrough

fallStem

flowMeasuring

WeirThe

water

balance

factors

of

soil

evaporation,

vegetation

transpiration,

canopy

interception,

soil

moisture

and

litter

holding

capacity

of

different

vegetation

types

were

monitored

by

field

fixed-point

monitoring.Subsequent

Work2.

Standard

Runoff

PlotsSubsequent

Work3.

Field

Rai