research article estimation model of soil freeze-thaw...

Hindawi Publishing CorporationThe Scientific World JournalVolume 2013 Article ID 636521 7 pageshttpdxdoiorg1011552013636521

Research ArticleEstimation Model of Soil Freeze-Thaw Erosion inSilingco Watershed Wetland of Northern Tibet

Bo Kong1 and Huan Yu2

1 Chinese Academy of Sciences of Mountain Hazards and Environment Chengdu 610041 China2 College of Earth Sciences Chengdu University of Technology Chengdu 610059 China

Correspondence should be addressed to Huan Yu yuhuan0622126com

Received 28 March 2013 Accepted 13 June 2013

Academic Editors J Bai H Cao B Cui and A Li

Copyright copy 2013 B Kong and H Yu This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The freeze-thaw (FT) erosion is a type of soil erosion like water erosion and wind erosion Limited by many factors the gradingevaluation of soil FT erosion quantities is not well studied Based on the comprehensive analysis of the evaluation indices of soilFT erosion we for the first time utilized the sensitivity of microwave remote sensing technology to soil moisture for identificationof FT state We established an estimation model suitable to evaluate the soil FT erosion quantity in Silingco watershed wetlandof Northern Tibet using weighted summation method of six impact factors including the annual FT cycle days average diurnalFT phase-changed water content average annual precipitation slope aspect and vegetation coverage Finally with the support ofGIS we classified soil FT erosion quantity in Silingco watershed wetlandThe results showed that soil FT erosion are distributed inbroad areas of Silingco watershed wetland Different soil FT erosions with different intensities have evidently different spatial andgeographical distributions

1 Introduction

The annual freeze-thaw cycle of soils in cold regions isan important aspect of agricultural and ecological envi-ronments because this cycle may significantly impact soilphysical properties [1 2] On the hydrological side theprecipitation occurring in early spring often results in highrates of runoff and erosion on frozen soil due to its poorinfiltration capacity Information about the depth of frostpenetration in the subsurface is essential to avoid damageto roadbeds structural foundations sewers and pipelines[3] Soil freeze-thaw (FT) erosion is the gravity causedremoving migrating and accumulating process of soil orrocks destructed mechanically by the differential expansionand contraction of different minerals induced by volumealteration of water at different phase due to temperaturechanges [4] The main reason is that the moisture transfersto the freezing front during the freezing period whichresults in water content increasing in places of shallow slopeand then frost heaving occurs under subzero temperatureThe association and arrangement among soil particles was

changed by frost heaving and then themechanical propertiesof the soil changed [5] In the melting period of spring thefrozen layers in shallow slope thawed influenced by kindsof factors such as precipitation and increasing temperatureThe melting water was hampered by unfrozen layer underthem during their infiltration downward results in the watercontent increasing rapidly in the layer between melt layerand frozen layer and reaching saturation or super saturationstate then the effective stress within the slope reduced thepartial or whole of the shallow slope slide down along thewater saturation layer under gravity [6] It occurs mostlyin the cold regions with high latitude and high altitude[7] Recently with the onset of global warming there hasbeen an increasing concern of greenhouse gas release frompermafrost and therefore interest in monitoring freeze-thawerosion dynamics is increasing [8]

Soil freezing creates a situation where water and icecoexist in a near thermodynamic equilibrium When soiltemperature gradually drops below the freezing point aportion of water in the soil turns into ice The remainderof the water exists as adsorbed films around soil particles

2 The Scientific World Journal

in pores with sufficiently small diameters and in crevicesbetween soil particles [9] As the temperature continuesto fall more water becomes frozen leaving residual liquidwater in progressively thinner adsorbed films smaller poresand crevices Consequently a small amount of soil watermay remain in a liquid state at temperatures well belowthe freezing point of water [10 11] In addition an upwardmigration of soil water takes place as the frost penetrates theground surface [12] a consequence of the thermal gradientcausing capillary flow from higher (deeper soil) to lowertemperatures

Present studies mainly focus on the impact of freeze-thaw erosion on the soil bulk density permeability moisturecontent and stability [13ndash16] but about estimation modelof freeze-thaw erosion in large scale are still insufficientThe FT model includes six factors annual FT cycle daysaverage diurnal phase-changedwater content annual averageprecipitation slope and vegetation coverage has interest char-acteristics under the complex effects of freeze-thaw cyclesthat factors take into account the environmental impact ofsoil properties rainfall topography and ecology AnnualFT cycle days referred to freeze-thaw frequency the freeze-thaw frequency at a particular station is the annual numberof times the recorded temperature falls below the point ofeffective freeze following a period when the temperature wasat or above the point of effective thaw Phase change of soilwater is an important sign of the development of soil freeze-thaw process causing the changing of liquid water contentof soil Wegmuller measured the brightness temperaturechange during several freezethaw circles using ground-basedmicrowave radiometer and established a semiempiricalmodel of frozen soil microwave emission [17] Zuerndorferdeveloped a freeze-thaw state classification algorithm basedon radiobrightness data from the Nimbus-7 Scanning Multi-channelMicrowaveRadiometer (SMMR) [18 19]Other threefactors were measured by the FT standard respectively fromclimate topography and vegetation growth status Becausethere are few applications of FT estimate in the high altitudefrozen region of China not much work is done on the impactof freeze-thaw cycle on alpine areas

Freeze-thaw area of more than 1269800 km2 accountedfor about 134 of the entire China according to secondnational soil erosion data by remote sensing survey Themajority of the freeze-thaw erosion area is mainly distributedin Northeast Northwest of high mountainous and TibetanPlateau According to a survey Tibetan Plateau the mainsource of the Yangtze River and Yellow River has FT erosionarea of 104 times 106 km2 which has seriously affected theproduction activity and life of local people and developmentof regional economy Meanwhile [20 21] the products of FTerosion have become the main source of sediment in theYangtze River and Yellow River Previous studies have alsoshown that FT erosion can increase soil erodibility and slopsoil instability thereby increasing the amount of soil lossby water [22ndash24] In some FT erosion areas the snowmeltrunoff erosion at spring accounts for most of annual soilerosion Therefore accelerating researches on FT erosionand finding the effective methods and means to preventFT erosion are extremely urgent and necessary As water

0 12060(km) Senzha

Nima

Bange

Anduo Neirong Baxing

Suo Biru

Jiali

Nagqu

92∘09984000998400998400E

92∘09984000998400998400E88∘09984000998400998400E

88∘09984000998400998400E84∘09984000998400998400E

36∘

0998400

0998400998400

N33

∘

0998400

0998400998400

N

33∘

0998400

0998400998400

N30

∘

0998400

0998400998400

N

N

Figure 1 Spatial location of Silingco watershed wetland

conservation functions of Silingco wetland has highly soilmoisture and large temperature difference between day andnight it is located in the high-altitude of the Tibetan Plateauits freeze-thaw erosion occurred significantly In this paperwe established an estimationmodel of FT erosion and appliedit for analysis of FT erosion in Silingco watershed wetland asan example

2 Materials and Methods

21 Study Area Silingco watershed wetland locates in TibetAutonomous Region bordering the northeastern TibetanPlateau the southern Xigaze Lhasa and Linzhi eastern Aliwestern Ali and the northern Xinjiang and Qinghai It hastotal area of 3946 km2 longitude of E 83∘5210158402010158401015840 sim95∘0110158400010158401015840and latitude of N 29∘5610158402010158401015840 sim36∘4110158400010158401015840 (Figure 1) It has ninecounties including Mani Bange Shenzha Nagqu AnduoSuoxian Baqing Biru and Jiali The area has high altitudeand low temperature [25] The soil erosion in some regionsis mainly FT erosion which has appeared to have more andmore evident influences on peoplersquos life and local economicdevelopment

22 Index Calculation Estimation of the quantities of FTerosion should be based on the amount of the soil loss perunit area per unit time in the FT region Currently methodsused to measure the quantities of FT erosion have not beenreported in China and abroad thus it is very difficult toquantitatively estimate the quantity of FT erosion In factFT erosion intensity or the quantity of FT erosion differsin different FT erosion zones due to the different impactsof FT process migration conditions of FT products andthe climatic factors Therefore we chose six most influentialfactors on FT occurrence and development including annualFT cycle days average diurnal FT phase-changed watercontent average annual precipitation slope aspect andvegetation coverage to comprehensively evaluate the quantityof FT erosion

The Scientific World Journal 3

221 Annual FT Cycle Days The annual FT cycle day is thenumber of days that FT cycles occur in a year We for the firsttime applied the microwave remote sensing technology forjudging FT state The land surface brightness temperaturesat day and night were calculated using the AMSR-E (TheAdvanced Microwave Scanning RadiometermdashEOS) data fromsatellite-borne passive microwave radiometer and used tocalculate the criterion factors for measuring the changes inland surface temperature and emissivity AMSR-E ismodifiedfrom the Advanced Earth Observing Satellite-II in NASAIt observes atmospheric parameters including precipitationsnow water equivalent surface wetness atmospheric cloudwater and water vapor It seems worthwhile to examine theimportance of freezing-thaw by investigating the frequencyof freeze-thaw cycles by the use of AMSR-EThe discriminantanalysis algorithm was used to classify the FT state at theland surface label the regions with FT cycles and statisticallycalculate the annual FT cycle day [26 27] The images werethen used to generate a 30m times 30m grid map and theclassificationmap of annual FT cycle day in the erosion areasThe FT criterion indexes are calculated as follows

119865 = 147Tb365119881+

9169Tb187119867

Tb365119881

minus 22677

119879 = 155Tb365119881+

86339Tb187119867

Tb365119881

minus 24241

(1)

where Tb is the polarized brightness temperature 365119881 isthe119881-polarized brightness temperature of channel 365 GHzand 187119867 is the 119867-polarized brightness temperature ofchannel 187 GHz 119865 gt 119879 indicates frozen soil and otherwiseindicates thawed soil

222 Average Diurnal Phase-Changed Water Content Inthe FT regions the phase-changed water content reflectsthe difference in soil liquid water content during the FTprocess The changes in potential land surface emissivitywere extracted from AMSR-E data and used to estimatephase-changed water content at the land surface Microwaveremote sensing has potential ability tomonitor the soil freeze-thaw process and accompanyingwater phase change Groundexperiments and model simulation of the characteristics ofmicrowave radiation of soil freeze-thaw process constitutethe base of microwave detection of soil freezethaw processSoil freezing process is essentially a phase change process ofliquidwaterThemicrowave emission of soil is sensitive to soilliquid water content mainly because of the large difference ofthe dielectric constant between liquid water and dry soil andice The total phase-changed water content was accumulatedbased on the defined FT erosion zone and FT cycle days andused to calculate the average diurnal phase-changed watercontent [28ndash33] using the following formula

119898pcv = 119860 (Tb1198891065119867

Tb119889365119867

minus

Tb1198861065119867

Tb119886365119867

) + 119861 (2)

where 119898pcv is phase-changed water content 119860 and 119861 are

the regression coefficients subscript 119889 indicates down railand subscript 119886 indicates a rise track

223 Annual Average Precipitation TRMM (Tropical Rain-fall Measuring Mission) 3B42 jointly developed by US NASAand Japanese NASDA was used to measure the tropicalrainfallThe systemhas three resolutions of 3 hours 1 day and1monthThemonthly datawas used in this paperThe averageannual precipitation was calculated based on the monthlyprecipitation during 1998ndash2010

224 Slope and Aspect A 30m times 30m grid slope and aspectdata were generated using ArcGIS software based on theDEM data which was obtained jointly by US NASA andNIMA at 30m using SRTM1 because of its higher spatialresolution

225 Vegetation Coverage The vegetation coverage wasconverted from the data obtained by a NDVI (NormalizedDifference Vegetation Index) MOD13Q1 instrument which isa product of MODIS with resolution of 250m and 16 daysbased on the following formula

FVC = ((NDVI minusNDVImin)

(NDVImax minus NDVImin))

119870

(3)

where FVC is the fractional vegetation coverage NDVI isthe normalized vegetation index NDVImax is the maximumvalue of pure vegetation NDVImin is the minimum value ofpure bare soil and 119870 is an experience factor and its valueis 1 in this paper The resampling resolution of vegetationcoverage is 30m

226 Estimation Model of FT Erosion Content The com-prehensive evaluation of FT erosion quantity is a complexprocess of a number of affecting factors to make it anintegrated single index In fact the evaluation classificationis only possible in one dimension This requires integrationof multiple factors impacting the FT erosion to obtain acomprehensive evaluation index In this paper we adapted aweighted summation method to calculate the comprehensiveevaluation index using the following formula

119868 =

sum119899

119894=1119882119894119868119894

sum119899

119894=1119882119894

(4)

where 119868 is the dimensionless comprehensive evaluation indexof FT erosion corresponding to erosion intensity 119899 is thesix indicators 119882

119894is the weight of each index and 119868

119894is

the dimensionless value of each index in different rangesThe weights of classification factors for FT erosion weredetermined by using analytic hierarchy process First the sixfactors (annual FT cycle days average diurnal phase-changedwater content average annual precipitation slope aspect andvegetation coverage (Figure 2)) were pairwise compared andused to build a comparison matrix Then their weights andconsistency were calculated and tested using the square rootmethod Table 1 lists the weight values of the six factors


0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

NagquBaxing

High 291(d)

Low 107

(a)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

High 012

Low 002

(b)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

75

100

150

200

300

400

500

750

(mm

)

(c)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

NagquBaxing

High 222

Low 1

(d)

Figure 2 Distribution maps of annual FT cycle days (a) average diurnal phase-changed water content (b) average annual precipitation (c)and vegetation coverage (d)

3 Results

31 Classification Map and Analysis of Each Indicator Byintroducing the indexes we obtained the annual FT cycledays and the average diurnal phase-changed water con-tent in eight years from 2003 to 2010 the average annualprecipitation slope and aspect with 30-meter resolutionin 12 years from 1998 to 2010 and the average fractionalvegetation coverage from 2003 to 2010 (Figure 1) Table 1 liststhe assigned classification value of each evaluation factor

As shown the annual FT cycle day did not have similardistribution pattern with diurnal phase-changed water con-tent Shenzha County and Anduo County in south Silingcowatershed wetland had higher FT cycle day while NeirongBiru Jiali and Suoxian in the east Silingco watershed wetlandhad higher diurnal phase-changed water contentThe 12-yearaverage annual precipitation increased mainly from west toeast The areas with relatively flat terrain abundant rainfalland relatively low altitude in the east Silingco watershedwetland had higher vegetation coverage

32 Estimation of the Quantity of FT Erosion Based on theerosion index calculated from formula (4) the FT erosion

in Silingco watershed wetland could be divided into 6categories no erosion (119868 lt 1) slight erosion (1 lt 119868 lt 22)mild erosion (22 lt 119868 lt 25) moderate erosion (25 lt 119868 lt28) intensive erosion (28 lt 119868 lt 33) and severe erosion(33 lt 119868 lt 4) The index standard distribution of erosionzones in Silingco watershed wetland is shown in Figure 3

Erosion is widely distributed in Silingco watershed wet-land of Northern Tibet with FT erosion intensity mainlyin moderate and intensive categories The total FT erosionarea in the region is 391 times 105 km2 Among them the slightmild moderate intensive and severe erosion areas are 307times 104 km2 689 times 104 km2 17 times 105 km2 106 times 105 km2 and155 times 104 km2 accounting for 78 1762 4347 271 and39 of the total erosion area respectively

33 The Spatial Distribution of FT Erosion The spatialdistribution of the different FT erosion zones differed sig-nificantly The slight erosion zone was concentrated in thesouthwest areas and southeast river of Silingco watershedwetland (Figure 3) and distributed in the low-lying potentialof lakes rivers and wetlands Its rainfall is between 200 and300mm slope was less than 3∘ and aspect was less than 45∘


Table 1 Classification assignment of evaluation indices and their weights

Index Assignment criteria Weight (119882119894)

Annual FT cycle days (day) le60 100ndash120 120ndash200 gt200 015Average diurnal phase-changed watercontent () le003 003ndash005 005ndash007 gt007 015

Average annual precipitate (mm) le150 150ndash300 300ndash500 gt500 005Slope (∘) 0ndash3 3ndash8 8ndash15 gt15 035

Aspect (∘) 0ndash45 45ndash90 90ndash135 135ndash225 005315ndash360 270ndash315 225ndash270

Vegetation coverage () 60ndash100 40ndash60 20ndash40 0ndash20 025Assigned value 1 2 3 4

Table 2 Error matrix of the quantity of FT erosion

FT erosion results being evaluatedSevere erosion Intensive erosion Moderate erosion Mild erosion Slight erosion Sum

Level of sampling pointSevere erosion 5 1 2 1 1 10Intensive erosion 0 23 3 5 9 40Moderate erosion 3 2 27 4 5 41Mild erosion 2 0 4 16 6 28Slight erosion 1 3 7 1 121 133Sum 11 29 43 27 142 252

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

SlightMildModerate

IntensiveSevere

Figure 3 Classification map of the quantity of freeze-thaw erosionin Silingco watershed wetland

In addition the area has high vegetation coverage and thelowest spatial position of average diurnal phase-changedwater content For example Gerencuo basin in Shenzhacounty Jiali basin and Suoxian basin had less FT erosionMild FT erosion was distributed mainly in the south ofSilingcowatershedwetland and located in the transition areasof the slight and moderate erosion zones such as Nagqu

Neirong and Anduo These areas had rainfall between 300and 500mm and higher degree of vegetation coverage Themoderate FT erosion zones accounted for the most majorityand were distributed mainly along Silingco watershed wet-land These areas had high incidence of avalanche relativelyhigh elevation and different rainfall from 75mm to 750mmThe intensive FT erosion zones accounted for the secondmost majority and were distributed mainly in northernSilingco watershed wetland These areas were uninhabitedand had a greater degree of natural disasters and quitedifferent average annual temperature The severe FT erosionzones were surrounded by the intensive erosion zones andincluded Jiali Biru and north of Nimaxian These areashad minimum proportion and distributed mostly around thewatershed

34 Accuracy Assessment To test the accuracy of the calcu-lated freeze-thaw erosion rank we adopted the basic errormatrix and precision index in the field survey A total of 252points were sampled with different spatial location land usetypes fractional vegetation cover change landforms aspectslope and erosion types and so on and analyzed using theprincipal component analysis to obtain the optimum indexand weights Table 2 lists the error matrix of the calculatederosion category and the field survey

The map precision proved the effectiveness of the clas-sification method The mild intensity erosion map reached91 precision and the extreme intensity high intensityand middle intensity erosion maps reached 60 precision(Table 3) reflecting the high credibility of the classification


Table 3 Precision index of the quantity of FT erosion

Cartographicprecision Omission User

accuracy Commission

Severe erosion 050 050 045 055Intensive erosion 058 043 079 021Moderate erosion 066 034 063 037Mild erosion 057 043 059 041Slight erosion 091 009 085 015

results The mild and extreme intensity erosion maps alsohad high preciousness although the area distribution ofsharp erosion was low The overall precision indicated thatthe classification results were in agreement with the actualerosion level Their probability reached 762 illustratingthat the freeze-thaw erosion model of Silingco watershedwetland is effective and accurate

4 Discussions and Conclusions

FT erosion as one of the of major erosion types in China ismainly located in the western China and has not yet attractedenough attention in China and abroad Studies on FT erosionare rare and far behind those on the water and wind erosionIn particular usually occurred freeze-thaw erosion researchof Plateau wetlands is insufficient

Previous models for FT erosion estimation are not veryaccurate and lack scientific basis due to poor selection ofimpact factors such as temperature slope aspect vegetationcoverage annual precipitation and soil In this paper wefrom the scientific point of view introduced microwaveremote sensing techniques to determine the state of FT ero-sion andmonitor the FT process which allow us attribute FTerosion to the development of surface permafrost and param-eters monitoring By using the microwave remote sensingtechniques we can detect the soil sensitivity to the changes ofmoisture and calculate the annual FT cycle days and averagediurnal phase-changed water content These selected factorsare reasonable and scientific by the high erosion accuracy

TheFT erosion estimationmodel established in this paperhas certain scientific basis and strong operationality andpracticability The results have certain significance for thein-depth understanding of the occurrence and developmentprocess of FT erosion in Silingco watershed wetland ofNorthern Tibet and for the rational use and preservation ofthe ecological environment Follow-up studies will furtherstrengthen the mechanisms underlying the capacity of atypical FT erosion zone the causes for the spatial distributionof moderate erosion area the evaluation precision and theecological consequences of erosion

Acknowledgments

The authors gratefully acknowledge the good researchARCGIS provided by Institute of Mountain Hazards andEnvironment Chinese Academy of SciencesThey also thank

the editors and anonymous referees for their helpful sugges-tions on the earlier freeze-thaw erosion study of their paperaccording to which they improved the contentThis work wassupported by Grant nos KZZD-EW-08-01 2012BAC19B05and sds-135-1205-03 and The Action Plan for West of CAS(KZCX2-XB3-08-01 and XDB03030507)

References

[1] J Qi W Ma and C Song ldquoInfluence of freeze-thaw onengineering properties of a silty soilrdquo Cold Regions Science andTechnology vol 53 no 3 pp 397ndash404 2008

[2] P Viklander ldquoPermeability and volume changes in till due tocyclic freezethawrdquo Canadian Geotechnical Journal vol 35 no3 pp 471ndash477 1998

[3] K D Eigenbrod ldquoEffects of cyclic freezing and thawing onvolume changes and permeabilities of soft fine-grained soilsrdquoCanadian Geotechnical Journal vol 33 no 4 pp 529ndash537 1996

[4] K L Tang Soil and Water Conservation in China pp 3ndash27Science Press Beijing China 2003

[5] W Shan Y Guo and H Liu ldquoEffect of freeze-thaw on strengthand microstructure of silty clayrdquo Journal of Harbin Institute ofTechnology vol 16 no 1 pp 207ndash211 2009

[6] F Niu G Cheng Y Lai and D Jin ldquoInstability study onthaw slumping in permafrost regions of Qinghai-Tibet PlateaurdquoChinese Journal of Geotechnical Engineering vol 26 no 3 pp402ndash406 2004

[7] K L Tang ldquoCharacteristics and perspectives on scientificdiscipline of soil erosion and soil and water conservation inChinardquo Research of Soil and Water Conservation vol 6 no 2pp 2ndash7 1999

[8] Y Sun Q Cheng and X Xue ldquoDetermining in-situ soil freeze-thaw cycle dynamics using an access tube-based dielectricsensorrdquo Geoderma vol 189 pp 321ndash327 2012

[9] J H Bai H F Gao and R Xiao ldquoA review of soil nitrogenmineralization as affected by water and salt in coastal wetlandsissues and methodsrdquo Clean-Soil Air Water vol 40 no 10 pp1099ndash1105 2012

[10] E J A Spaans and J M Baker ldquoExamining the use of timedomain reflectometry for measuring liquid water content infrozen soilrdquo Water Resources Research vol 31 no 12 pp 2917ndash2925 1995

[11] J Bai W Deng Q Wang B Cui and Q Ding ldquoSpatialdistribution of inorganic nitrogen contents of marsh soils ina river floodplain with different flood frequencies from soil-defrozen periodrdquo Environmental Monitoring and Assessmentvol 134 no 1ndash3 pp 421ndash428 2007

[12] J Lee and S Lee ldquoThe frost penetration with the modified soilin the landfill bottom liner systemrdquo Geosciences Journal vol 6pp 7ndash12 2002

[13] H Kok and D K McCool ldquoQuantifying freezethaw-inducedvariability of soil strengthrdquo Transactions of the American Societyof Agricultural Engineers vol 33 no 2 pp 501ndash506 1990

[14] S Mostaghimi R A Young A R Wilts and A L KenimerldquoEffects of frost action on soil aggregate stabilityrdquo Transactionsof the American Society of Agricultural Engineers vol 31 no 2pp 435ndash439 1988

[15] E J Chamberlain and A J Gow ldquoEffect of freezing and thawingon the permeability and structure of soilsrdquo Engineering Geologyvol 13 no 1ndash4 pp 73ndash92 1979


[16] J Bai B Cui B Chen et al ldquoSpatial distribution and ecologicalrisk assessment of heavy metals in surface sediments froma typical plateau lake wetland Chinardquo Ecological Modelling vol222 no 2 pp 301ndash306 2011

[17] U Wegmuller ldquoThe effect of freezing and thawing on themicrowave signatures of bare soilrdquo Remote Sensing of Environ-ment vol 33 no 2 pp 123ndash135 1990

[18] B Zuerndorfer and A W England ldquoRadiobrightness decisioncriteria for freezethaw boundariesrdquo IEEE Transactions onGeoscience and Remote Sensing vol 30 no 1 pp 89ndash101 1992

[19] J Zhang A R Mark and G Jeffery ldquoDiscretization approachin integrated hydrologic model for surface and groundwaterinteractionrdquo Chinese Geographical Science vol 22 no 6 pp659ndash672 2012

[20] G E Formanek D K McCool and R I Papendick ldquoFreeze-thaw and consolidation effects on strength of a wet silt loamrdquoTransactions of the American Society of Agricultural Engineersvol 27 no 6 pp 1749ndash1752 1984

[21] J H Bai Q Q Lu J JWang et al ldquoLandscape pattern evolutionprocesses of alpine wetlands and their driving factors in theZoige plateau of Chinardquo Journal of Mountain Science vol 10no 1 pp 54ndash67 2013

[22] J Bai H Ouyang R Xiao et al ldquoSpatial variability of soilcarbon nitrogen and phosphorus content and storage in analpine wetland in the Qinghai-Tibet Plateau Chinardquo AustralianJournal of Soil Research vol 48 no 8 pp 730ndash736 2010

[23] B S Sharratt and M J Lindstrom ldquoLaboratory simulationof erosion from a partially frozen soilrdquo in Proceedings of theInternational Symposium on Soil Erosion Research for the 21stCentury pp 159ndash162 January 2001

[24] B S Sharratt M J Lindstrom G R Benoit R A Youngand A Wilts ldquoRunoff and soil erosion during spring thawin the northern US Corn Beltrdquo Journal of Soil and WaterConservation vol 55 no 4 pp 487ndash494 2002

[25] J P Zhang Y L Zhang and L S Liu ldquoPredicting potential dis-tribution of Tibetan spruce (Picea smithiana) in Qomolangma(Mount Everest) National Nature Preserve using maximumentropy niche-based modelrdquo Chinese Geographical Science vol21 no 4 pp 417ndash426 2011

[26] R B G Williams and D A Robinson ldquoExperimental frostweathering of sandstone by various combinations of saltsrdquoEarth Surface Processes and Landforms vol 26 no 8 pp 811ndash818 2001

[27] B W Zuerndorfer A W England M C Dobson and F TUlaby ldquoMapping freezethaw boundaries with SMMR datardquoAgricultural and ForestMeteorology vol 52 no 1-2 pp 199ndash2251990

[28] PWang LM Jiang and L X Zhang ldquoEvaluation of the impactof lake ice on passive microwave snow retrieval algorithmsusing ground-based observationrdquo Remote Sensing Applicationvol 5 pp 59ndash64 2011

[29] T Schmugge P E OrsquoNeill and J R Wang ldquoPassive microwavesoil moisture researchrdquo IEEE Transactions on Geoscience andRemote Sensing vol 24 no 1 pp 12ndash22 1986

[30] S H Li D M Z Demin and Z Q Luan ldquoQuantitativesimulation on soil moisture contents of two typical vegetationcommunities in Sanjiang Plain Chinardquo Chinese GeographicalScience vol 21 no 6 pp 723ndash733 2011

[31] T J Jackson and T J Schmugge ldquoPassive microwave remotesensing system for soil moisture some supporting researchrdquoIEEE Transactions on Geoscience and Remote Sensing vol 27pp 225ndash235 1989

[32] J L Foster D K Hall A T C Chang and A Rango ldquoAnoverview of passive microwave snow research and resultsrdquoReviews of Geophysics amp Space Physics vol 22 no 2 pp 195ndash208 1984

[33] A T C Chang J L Foster and D Hall ldquoNimbus-7 SMMRderived global snow cover parametersrdquo Allnals of Glaciologyvol 9 pp 39ndash44 1987

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in pores with sufficiently small diameters and in crevicesbetween soil particles [9] As the temperature continuesto fall more water becomes frozen leaving residual liquidwater in progressively thinner adsorbed films smaller poresand crevices Consequently a small amount of soil watermay remain in a liquid state at temperatures well belowthe freezing point of water [10 11] In addition an upwardmigration of soil water takes place as the frost penetrates theground surface [12] a consequence of the thermal gradientcausing capillary flow from higher (deeper soil) to lowertemperatures

Present studies mainly focus on the impact of freeze-thaw erosion on the soil bulk density permeability moisturecontent and stability [13ndash16] but about estimation modelof freeze-thaw erosion in large scale are still insufficientThe FT model includes six factors annual FT cycle daysaverage diurnal phase-changedwater content annual averageprecipitation slope and vegetation coverage has interest char-acteristics under the complex effects of freeze-thaw cyclesthat factors take into account the environmental impact ofsoil properties rainfall topography and ecology AnnualFT cycle days referred to freeze-thaw frequency the freeze-thaw frequency at a particular station is the annual numberof times the recorded temperature falls below the point ofeffective freeze following a period when the temperature wasat or above the point of effective thaw Phase change of soilwater is an important sign of the development of soil freeze-thaw process causing the changing of liquid water contentof soil Wegmuller measured the brightness temperaturechange during several freezethaw circles using ground-basedmicrowave radiometer and established a semiempiricalmodel of frozen soil microwave emission [17] Zuerndorferdeveloped a freeze-thaw state classification algorithm basedon radiobrightness data from the Nimbus-7 Scanning Multi-channelMicrowaveRadiometer (SMMR) [18 19]Other threefactors were measured by the FT standard respectively fromclimate topography and vegetation growth status Becausethere are few applications of FT estimate in the high altitudefrozen region of China not much work is done on the impactof freeze-thaw cycle on alpine areas

Freeze-thaw area of more than 1269800 km2 accountedfor about 134 of the entire China according to secondnational soil erosion data by remote sensing survey Themajority of the freeze-thaw erosion area is mainly distributedin Northeast Northwest of high mountainous and TibetanPlateau According to a survey Tibetan Plateau the mainsource of the Yangtze River and Yellow River has FT erosionarea of 104 times 106 km2 which has seriously affected theproduction activity and life of local people and developmentof regional economy Meanwhile [20 21] the products of FTerosion have become the main source of sediment in theYangtze River and Yellow River Previous studies have alsoshown that FT erosion can increase soil erodibility and slopsoil instability thereby increasing the amount of soil lossby water [22ndash24] In some FT erosion areas the snowmeltrunoff erosion at spring accounts for most of annual soilerosion Therefore accelerating researches on FT erosionand finding the effective methods and means to preventFT erosion are extremely urgent and necessary As water

0 12060(km) Senzha

Nima

Bange

Anduo Neirong Baxing

Suo Biru

Jiali

Nagqu

92∘09984000998400998400E

92∘09984000998400998400E88∘09984000998400998400E

88∘09984000998400998400E84∘09984000998400998400E

36∘

0998400

0998400998400

N33

∘

0998400

0998400998400

N

33∘

0998400

0998400998400

N30

∘

0998400

0998400998400

N

N

Figure 1 Spatial location of Silingco watershed wetland

conservation functions of Silingco wetland has highly soilmoisture and large temperature difference between day andnight it is located in the high-altitude of the Tibetan Plateauits freeze-thaw erosion occurred significantly In this paperwe established an estimationmodel of FT erosion and appliedit for analysis of FT erosion in Silingco watershed wetland asan example

2 Materials and Methods

21 Study Area Silingco watershed wetland locates in TibetAutonomous Region bordering the northeastern TibetanPlateau the southern Xigaze Lhasa and Linzhi eastern Aliwestern Ali and the northern Xinjiang and Qinghai It hastotal area of 3946 km2 longitude of E 83∘5210158402010158401015840 sim95∘0110158400010158401015840and latitude of N 29∘5610158402010158401015840 sim36∘4110158400010158401015840 (Figure 1) It has ninecounties including Mani Bange Shenzha Nagqu AnduoSuoxian Baqing Biru and Jiali The area has high altitudeand low temperature [25] The soil erosion in some regionsis mainly FT erosion which has appeared to have more andmore evident influences on peoplersquos life and local economicdevelopment

22 Index Calculation Estimation of the quantities of FTerosion should be based on the amount of the soil loss perunit area per unit time in the FT region Currently methodsused to measure the quantities of FT erosion have not beenreported in China and abroad thus it is very difficult toquantitatively estimate the quantity of FT erosion In factFT erosion intensity or the quantity of FT erosion differsin different FT erosion zones due to the different impactsof FT process migration conditions of FT products andthe climatic factors Therefore we chose six most influentialfactors on FT occurrence and development including annualFT cycle days average diurnal FT phase-changed watercontent average annual precipitation slope aspect andvegetation coverage to comprehensively evaluate the quantityof FT erosion



119865 = 147Tb365119881+

9169Tb187119867

Tb365119881

minus 22677

119879 = 155Tb365119881+

86339Tb187119867

Tb365119881

minus 24241

(1)



119898pcv = 119860 (Tb1198891065119867

Tb119889365119867

minus

Tb1198861065119867

Tb119886365119867

) + 119861 (2)








119870

(3)



119868 =

sum119899

119894=1119882119894119868119894

sum119899

119894=1119882119894

(4)



119894is



0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

NagquBaxing

High 291(d)

Low 107

(a)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

High 012

Low 002

(b)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

75

100

150

200

300

400

500

750

(mm

)

(c)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

NagquBaxing

High 222

Low 1

(d)


3 Results

















0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

SlightMildModerate

IntensiveSevere









accuracy Commission







Acknowledgments



References







































Journal of












Volume 2014

Advances in









Geophysics
















119865 = 147Tb365119881+

9169Tb187119867

Tb365119881

minus 22677

119879 = 155Tb365119881+

86339Tb187119867

Tb365119881

minus 24241

(1)



119898pcv = 119860 (Tb1198891065119867

Tb119889365119867

minus

Tb1198861065119867

Tb119886365119867

) + 119861 (2)








119870

(3)



119868 =

sum119899

119894=1119882119894119868119894

sum119899

119894=1119882119894

(4)



119894is



0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

NagquBaxing

High 291(d)

Low 107

(a)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

High 012

Low 002

(b)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

75

100

150

200

300

400

500

750

(mm

)

(c)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

NagquBaxing

High 222

Low 1

(d)


3 Results

















0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

SlightMildModerate

IntensiveSevere









accuracy Commission







Acknowledgments



References







































Journal of












Volume 2014

Advances in









Geophysics















0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

NagquBaxing

High 291(d)

Low 107

(a)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

High 012

Low 002

(b)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

75

100

150

200

300

400

500

750

(mm

)

(c)

0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

NagquBaxing

High 222

Low 1

(d)


3 Results

















0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

SlightMildModerate

IntensiveSevere









accuracy Commission







Acknowledgments



References







































Journal of












Volume 2014

Advances in









Geophysics
























0 12060(km)

Senzha

Nima

Bange

AnduoNeirong

SuoBiru

Jiali

Nagqu

Baxing

SlightMildModerate

IntensiveSevere









accuracy Commission







Acknowledgments



References







































Journal of












Volume 2014

Advances in









Geophysics

















accuracy Commission







Acknowledgments



References







































Journal of












Volume 2014

Advances in









Geophysics





































Journal of












Volume 2014

Advances in









Geophysics














research article estimation model of soil freeze-thaw...

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