植被對水土流失和水源涵養(yǎng)的影響

植被對水土流失和水源涵養(yǎng)的影響Vertical

vegetationstructures;Plantdiversity;Vegetation

spatialdistributionMultidimensionalanalysisoftheeffectsofvegetationonrunoffandsoilloss(CrockfordandRichardson,2000;Lietal.,2014;Quintonetal.,1997;Janssensetal.,1998;Martinetal.,2010;Puigdefabregas,2005;Bochetetal.,1998;Fengetal.,2012;Luetal.,2012;Liuetal.,2018;

)EFFECTSOFVEGETATION

INMINIMIZING

EROSIONAbsorbs the energy offallingrain;Removes water from soilandtranspiresitintothe

air;Roots hold surface soil andstabilizebank

materials;Helpsthegroundtoabsorb

water;Slows the runoff velocity

andtraps

sediment.Questions discussedinthisresearch

:1. How does the vegetation coverage andlitter coverage influence soilprocess? What is the dynamicof soil water infiltrationerosionprocessduringrainfall?2. Theregulationmechanismofvegetationcoverageonsoil

erosion?MethodsMeasuringexperimental

indexesGrass:CarexShrub:TwigsoftheCHASTE

TreeRunoff

bucketPrecondition

of

experiment Rainfallsimulation

experimentVegetationcoverage/LittercoverageRainfallintensity:

60mm/hDurationofrainfall:60minSlope：15°VegetationCoverage:0,25%,50%,

75%,100%;LitterCoverage:0,50,100,150，200,

250g/m2Control

conditionMethods1000800600400200012000

1020304050Surfacerunoff

rate(mL/min)60Time025%50%75%100%Fig.1Dynamicchangesofsurfacerunoffrateandsedimentrateunderdifferentvegetationcoverage

conditionsSlopeRunoffandSediment

ProcessSedimentrate

(g/min)20.0018.0016.0014.0012.0010.008.006.004.002.00Time0.000102030405060025%50%75%100%110010009008007006005004003002001000SurfaceRunoff

(ml/min)Time/min0 5 10 15 20 25 30 35 40 45 50 55 60 650g50g100g150g200g250gFig.2DynamicchangesofsurfacerunoffrateandsedimentrateunderdifferentLittercoverage

conditionsEffectsofvegetationandlittercoverageonsoilerosion

process1.201.000.800.600.400.200.00Infiltration

rate(mm/min)0 10 20 30 40 50 60Durationof

rainfall(min)025%50%75%100%Fig.3DynamicchangesofSoilmoistureincrement

and

soil Fig.4DynamicchangesofSoilmoistureincrementandsoilinfiltrationrateunderdifferentvegetation

coverage

conditions infiltrationrateunderdifferentLittercoverage

conditions141210864200 10 20 30 40 50 60 7090Soilmoisture

increment80Time(min)025%50%75%100%SlopeSoilInfiltration

Process10.009.008.007.006.005.004.003.002.001.000.000 10 20 30 40 50 60 70Soilmoisture

increment80 90Time/min0g50g100g150g 200g 250g0.800.600.400.200.001.000 10 20 3050 60Infiltration

rate(mm/min)40Time

(min)0g 50g 100g150g 200g 250gEffectsofvegetationandlittercoverageonsoilerosion

processWith the increment of vegetation and litter

coverage, soil moistureincreasedandthesurfacerunoffrate

decreased.Itshowsthatmorewaterwasusedforinfiltration,andthusincreasedsoilmoisturewiththeincrementofvegetationandlittercoverage.Vegetationandlittercoveragecanachievegoodwaterstorage

effect.Effectsofvegetationandlittercoverageonsoilerosion

processEffectsofvegetationcoverageonhydrodynamic

parametersFig.5Variationofmeanvelocityofslopeflowwithvegetation

coverageTal.1FittedEquationsofSlopeRunoffVelocity

withDifferentVegetation

CoverageWiththeincrementofvegetationcoverage,theKvaluedecreased,Itindicatesthattheroughertheslopewas,thesmallertheVvalue

was.Effectsofvegetationcoverageonrunoff

velocityKisthecoefficientrelatedtotheroughnessofslope

surface.V=K·Jn·qmEffectsofvegetationcoverageonhydrodynamic

parametersEffectsofvegetationcoverageonrunoffmorphologyandresistance

characteristicsTal.1Characteristicsofhydrodynamicparametersofsloperunoffunderdifferent

coverageLaminar

flowSlow

flowFig.6ResistanceCoefficient(f)ofSlopeFlowunderDifferentVegetation

CoverageVegetationcoveragecanreducetherunoffvelocityontheslope,alleviatetherunoffmorphologyandincreasethesurfaceresistance

coefficient.Vegetationcangreatlyincreasetheroughnessofslopes.Withtheincrementofvegetationcoverage,theresistanceofrunoffonslopesbecomedlargerandlarger.Themoreenergyofrunoffwasusedtoovercomeresistance,thelessenergywasusedforerosionandsedimenttransport,theweakersoilerosionwas.Effectsofvegetationcoverageonsoilshearstrengthand

anti-erodibilityTal.2soilinternalfrictionangle(φ),soilcohesionforce(C)andshearstrength(τf)ondifferentvegetationcovered

slopesItshowsthatcohesionforce(C)andinternal

frictionangle(φ)increasedsignificantlyofBE,

IE,AEcomparedwithBFandbarelandinall

vegetationcoverages.Withtheincrementofsoilmoisturecontent,theCandφdecreased,whichindicatesthatthesoilshearstrength

decreased.TheCandφdecreasedaftertheexperiment,whichindicatesthatCandφwerenotonlyaffectedbythecoverageconditions,butalsoaffectedbythemoisturecontentofvegetationslope.VegetationcoverageincreasedtheCandφ,which

hadastrongeffectofsoilconsolidationanderosion

resistance.Fig.7Fullyautomatictriaxialcompressioninstrument1.FieldObservation

Experimentwaterbalance

experimentMeasuring

WeirLysimeterSystemsSap

flow（Vegetationtranspiration）Through

fallStem

flowSoil

waterSubsequent

WorkThewaterbalancefactorsofsoilevaporation,vegetationtranspiration,canopyinterception,soilmoistureandlitterholdingcapacityofdifferentvegetationtypesweremonitoredbyfieldfixed-point

monitoring.2.StandardRunoff

PlotsSubsequent

Work3.FieldRai