new environmentasia - open development mekong · 2015. 6. 29. · included soil survey and...

Critical Factors Affecting the Desertification in Pa Deng, Adjoining Area of Kaeng Krachan National Park, Thailand

Saowanee Wijitkosum

Environmental Research Institute, Chulalongkorn University, Bangkok 10330, Thailand

Abstract

Theaimof this study is tobring forwardandanalyzekey factors thathaveaneffecton thedesertification inPaDengSub-districtinordertoassessthedesertificationriskofthesites.TheMEDALUSModelwasusedtoconductthe desertificationriskassessment.ThespatialanalysisstudywasdonewithGeographicInformationSystem(GIS)andRemoteSensing(RS)programs.ThekeyfactorsthathadanimpactonthedesertificationinPaDengareaareclimaticfactor(aridityindex:AI),soilfactors(soiltexture,soilfertilityandsoilerosion)andhumanactivityfactor(landuse).TheresultsrevealedthatthemajorityoftheplainareainPaDengwasatamoderatedesertificationrisk.Thecriticalfactorthatincreasedtheriskofdesertificationwassoilerosion.

Keywords:criticalfactor;desertification;soilerosion;landuse;climatechange

1. Introduction

Desertification predicates current features of aglobal problem despite different characteristics in distinct geographical locations, economy, social and environmental conditions. The United Nations ConventiontoCombatDesertification(UNCCD)defined thedesertificationas“landdegradationinarid,semi-arid anddrysub-humidareasresultingfromvariousfactors, including climatic variations and human activities” (FAO,1993).Desertificationhasbecomemoresevere. Hai et al. (2013) examined human activities that affectedthedesertificationincludinghighpopulationand poverty, inappropriate cultivating techniques, deforestation, ill-adopted legal frameworks,weakmanagementcapacity,lackofadequateknowledge,andlackofawarenessinlocalpopulation.Theunsustainableland use may lead to soil degradation which is known asdesertification(Núñezet al.,2012;Cebecaueret al., 2008;García-Ruiz,2010). Desertification is nothing new inAsia.Many studies have been undertaken for assessing and mapping desertification risk in particular areas but the identification of critical factors that affect desertification risks have not been thoroughly studied. Thailand is a tropical country that has savannaclimate(Aw),theclimatechangethataffectsevapotranspiration is expected to cause an increase of drought and an expansion in dry areas. Someparts of the country are classified as dry sub-humid areas, aridity index (AI), between 0.51 and 0.65,which showed that Thailand can be considered

as an affected country although it is located in monsoon climate. Similar to other countries, many studies conducted in Thailand focus on the overall desertification risks of the country, but notspecificonspatialstudy.Moreover,nofurtherstudyhas been conducted in the areas identified as high desertificationrisks,thusthecriticalfactorsandhowtheyaffecttheriskshavenotbeenidentified. This study was conducted in the Pa Deng Sub-district, the adjoining area ofKaengKrachan NationalPark,Thailand,wherethedesertificationcanpotentiallybecomemoresevere.PaDenghasaplainareaofapproximately49.87km2locatedonthecentralpart(11.94%ofthewholearea).Themajorpartoftheplainarea(76.62%)isatamoderateriskofdesertification (Wijitkosum,2012). The population of PaDenghas expanded their settlements and cropping in the plain area that liesbetweentheNationalParkandthereservedforestofKaengKrachanNationalPark.Currently,thetrespassing in the study area has become more serious which triggerslanduse,landusechange,landslideandsoilerosionproblems.Itispossiblethatthedesertificationinthissensitiveareamaycarrysevereconsequencesduetoanacceleratinglossofforestarea(Wijitkosum,2012).Therefore, the study of factors affecting the desertification inPaDeng,whichcanbeappliedfordesertification risk assessment, aims to provide a significantdatabasefordevelopingplansandmeasuresagainst the desertification based on the sustainabledevelopmentconcept.Inaddition,thestudyresultsareapplicableforspatialdevelopmentplansetting.

The international journal published by the Thai Society of Higher Education Institutes on Environment

EnvironmentAsia

Genotoxicity Assessment of Mercuric Chloride in the Marine Fish Therapon jaruba

Nagarajan Nagarani, Arumugam Kuppusamy Kumaraguru, Velmurugan Janaki Deviand Chandrasekaran Archana Devi

Center for Marine and Coastal Studies, School of Energy, Environment and Natural Resources,Madurai Kamaraj University, Madurai-625021, India

Abstract

The aim of the present study was to standardize and to assess the predictive value of the cytogenetic analysisby Micronucleus (MN) test in fish erythrocytes as a biomarker for marine environmental contamination. Micronucleusfrequency baseline in erythrocytes was evaluated in and genotoxic potential of a common chemical was determinedin fish experimentally exposed in aquarium under controlled conditions. Fish (Therapon jaruba) were exposed for 96hrs to a single heavy metal (mercuric chloride). Chromosomal damage was determined as micronuclei frequency infish erythrocytes. Significant increase in MN frequency was observed in erythrocytes of fish exposed to mercuricchloride. Concentration of 0.25 ppm induced the highest MN frequency (2.95 micronucleated cells/1000 cells comparedto 1 MNcell/1000 cells in control animals). The study revealed that micronucleus test, as an index of cumulativeexposure, appears to be a sensitive model to evaluate genotoxic compounds in fish under controlled conditions.

Keywords: genotoxicity; mercuric chloride; micronucleus

Available online at www.tshe.org/EAEnvironmentAsia 2 (2009) 50-54

1. Introduction

In India, about 200 tons of mercury and itscompounds are introduced into the environmentannually as effluents from industries (Saffi, 1981).Mercuric chloride has been used in agriculture as afungicide, in medicine as a topical antiseptic anddisinfectant, and in chemistry as an intermediate inthe production of other mercury compounds. Thecontamination of aquatic ecosystems by heavymetals and pesticides has gained increasing attentionin recent decades. Chronic exposure to andaccumulation of these chemicals in aquatic biotacan result in tissue burdens that produce adverseeffects not only in the directly exposed organisms,but also in human beings.

Fish provides a suitable model for monitoringaquatic genotoxicity and wastewater qualitybecause of its ability to metabolize xenobiotics andaccumulated pollutants. A micronucleus assay hasbeen used successfully in several species (De Flora,et al., 1993, Al-Sabti and Metcalfe, 1995). Themicronucleus (MN) test has been developedtogether with DNA-unwinding assays asperspective methods for mass monitoring ofclastogenicity and genotoxicity in fish and mussels(Dailianis et al., 2003).

The MN tests have been successfully used asa measure of genotoxic stress in fish, under both

laboratory and field conditions. In 2006 Soumendraet al., made an attempt to detect genetic biomarkersin two fish species, Labeo bata and Oreochromismossambica, by MN and binucleate (BN)erythrocytes in the gill and kidney erythrocytesexposed to thermal power plant discharge atTitagarh Thermal Power Plant, Kolkata, India.

The present study was conducted to determinethe acute genotoxicity of the heavy metal compoundHgCl2 in static systems. Mercuric chloride is toxic,solvable in water hence it can penetrate the aquaticanimals. Mutagenic studies with native fish speciesrepresent an important effort in determining thepotential effects of toxic agents. This study wascarried out to evaluate the use of the micronucleustest (MN) for the estimation of aquatic pollutionusing marine edible fish under lab conditions.

2. Materials and methods

2.1. Sample Collection

The fish species selected for the present studywas collected from Pudhumadam coast of Gulf ofMannar, Southeast Coast of India. Theraponjarbua belongs to the order Perciformes of thefamily Theraponidae. The fish species, Theraponjarbua (6-6.3 cm in length and 4-4.25 g in weight)was selected for the detection of genotoxic effect

Available online at www.tshe.org/EAEnvironmentAsia 7(2) (2014) 87-98

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The objective of this study was to indicate and analyzethekeyfactorsthatimpactonthedesertificationinthePaDengareainordertoassessthedesertificationrisksofthesite.

2. Materials and Methods

2.1. Study area

The PaDeng Sub-district is located inKaeng Krachan District, Phetchaburi Province, in the watershedsofthePranburiRiver.Thestudyarea,PaDeng, covers an area of approximately 417.80km2.Geographically,it liesbetweenthelatitudes99˚20’Eto99˚37’Eand12˚33’Nto12˚45’Natanaltitudeof140mabovemeansealevel. PaDeng is piedmontplateau, slopinggraduallyfromwest to east.Themajorityof the land is slopecomplexwith slopes greater that 35%.Overall, the terrainatPaDenghasbeenclassifiedasundulatingandrollingterrain.Duetotheslopes,soilsintheseareashavenotyetbeensurveyedorclassified. SomepartsofthearealiewithintheperimeterofthereservedforestandtheKaengKrachanNationalPark,whichisatropicalrainforest.PaDengissurroundedbymountainswithaplainareaatthecenter.Agricultureisthemainoccupationofthemajorityofthepopulation;dominatedbymonoculture.Theagriculturalpracticeswereimplementedwithoutsoilimprovementandtherewasnolivestockfarming. Themeanannualtemperatureandannualrainfallare 27˚C and 1,070mm respectively.The areawasfacinganincreasingpopulationpressureduetolimitedutilizable land.Thecentralplain (9.14%of the totalarea),whichcanbeutilizedforagricultureorhousing, representsonly12%ofthetotalareawhilethepopulation growthis2.80%(Wijitkosumet al.,2013)

2.2. Data analysis

Thecriticalfactorsthataffectthedesertificationwereidentifiedbytheresultsoftheanalysisoffactors that affected the risks.The characteristics of each factorwere comparedwith specifications definedby both national and international organizations that attempted tomonitor and assess desertification. In Thailand, the LandDevelopment Department of Thailand(LDD)tookpartinassessingandmonitoringdesertificationaswellasconductedseveralgeographicstudiesusingtheRemoteSensing(RS)andGeographic InformationSystem(GIS)(vanLyndenet al.,2001;Santini et al.,2010;Rangzanet al.,2008);theresponsibilityincludedsoil surveyandclassification, soilanalysis,landuseplanning,conductingexperimentsandcarrying

variousaspectsoflanddevelopment.Thedatacollectedwasusedforspatialanalysisandmapping. Spatialdataandattributedataforthefivefactors;AI,soiltexture,soilfertility,soilerosionandlandusewerepreparedinshapefileformatforArcGISsoftware.Followingtheanalysisofthedesertificationrisklevelforeachfactor,adesertificationriskmapofthestudyareawascreatedbyoverlayingthepreparedshapefiledatausingArcGIS.

2.2.1. Assessment of desertification risk factors for desertification risk mapping Desertificationoccurswhenthelandbecamearidand barren because topsoilwas completely eroded. InThailand, the twomajor causes of desertificationare(a)climatice.g.leachingandtranslocationofsoil mineralsandseasonaldroughtand(b)anthropogenice.g.landusewithoutsoilimprovement,over-exploitation ofland,inappropriateuseofsteep-slopelandscausingsoilerosionandsalinization.Theinvestigationofthedesertificationriskindicatorswastakingintoaccountthe parameters suggested by previous research intheregionalscale(LDD,2004)aswellas theactual possibilityofhavingspecificdatabasesatnationalscale.Thedesertificationriskassessmentrequiredaninputof data of the three major factors and their indicators; climaticfactor(AI),soilfactors(soilcomposition,soilfertilityandsoilerosion)andhumanactivityfactor(landuse),inordertobeanalyzedin5mapunits. Thedesertificationriskassessmentwascalculated byusingtheMEDALUSapproach(Kosmaset al.,1999). TheMEDALUSmodel,“MediterraneanDesertificationandLandUse”, aims toassess the sensitivityof thedesertificationarea(Honardoustet al.,2011;Abdalla,2008;Giordanoet al.,2002).ThisapproachissuitableforAsianregionsandcanbeappliedtoreliablyevaluate desertification conditions inmany countries inAsia(Sepehret al., 2007;Gholamet al., 2006;Rangzanet al., 2008; Farajzadeh et al., 2007). In the study,theMEDALUSmodelwasmodified by integratingfivefactorsasinformationlayersprovidinganoverallpictureoftheenvironmentalconditionswithouttakingintoaccountthelandmanagementfactorinthearea. Themodeltakesinbroadsystemsoffiveindicators at the minimum set of selected data that had to be assessed(Sepehret al.,2007;LDD,2003;Bayramin,2003).Eachsystemhasa“qualityindex”whichincorporates severalparameters.Accordingtothedevelopedalgorithm, thegeometricmeanwasusedtocompilemapsofESAstoassessthedesertification(Sepehret al.,2007;EEA,2004). Throughout themodel, each individual indexwasappliedaquantitativeclassificationschemewithvaluesof1and2.Thevalue1wasassignedtoareas

S. Wijitkosum / EnvironmentAsia 7(2) (2014) 87-98

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Figure 1. Framework and study method

2.2.1. Assessment of desertification risk factors for desertification risk mapping Desertification occurs when the land became arid and barren because topsoil was completely

eroded. In Thailand, the two major causes of desertification are (a) climatic e.g. leaching and translocation of soil minerals and seasonal drought and (b) anthropogenic e.g. land use without soil improvement, over-exploitation of land, inappropriate use of steep-slope lands causing soil erosion and salinization. The investigation of the desertification risk indicators was taking into account the parameters suggested by previous research in the regional scale (LDD, 2004) as well as the actual possibility of having specific databases at national scale. The desertification risk assessment required an input of data of the three major factors and their indicators; climatic factor (AI), soil factors (soil composition, soil fertility and soil erosion) and human activity factor (land use), in order to be analyzed in 5 map units.

Aridity index Soil composition Soil fertility Soil erosion Land use

Map of desertification risks in the study area

Profiling the attribute data of the map and factors affecting the desertification using statistic approach

Analyzing data using GIS

Overlay Analysis

Identify critical factors that affect desertification risk in the study area

Reviewing literature and gathering data related to desertification

Analyzing data

Aridityfactor

Soilcomposition

Soilfertility

Soilerosion

Land use

Soil factors Human Activity Factor Climatic factor

AridityMap

Soilcomposition

Map

Soil fertility Map

ErosionMap

Land useMap

GIS & RS GIS & RS GIS & RS

Figure1.Frameworkandstudymethod

withtheleastsensitivityandthevalue2wasassignedtoareaswiththemostsensitivity.ThequalityindiceswerecomputedandemployedintheGIStechniqueforcomputing theDesertificationSensitivity Index andmappingthedesertificationsensitivityareas. Thefirstfactorconcernedoneindicator;theAIinwhichtheclimatedatahadbeencollectedovera30-year periodatNongPhlabAgrometeorogicalStation, the representativestation in thearea.Thereliabilityand stabilitywasanalyzedusingtheDoubleMassCurvemethod(Wilson,1983;HPTA,1999;Sharadet al.,2007). Since PaDeng is partially located in the national reservedforestandclosetotheThai-Myanmarborder,theNong PhlabAgrometeorogical Stationwas the

onlyrepresentativestationofPaDengareaduetoitsstrategiclocationandanavailableofcompleteclimatedata.Moreover,othercandidatemeteorogicalstationswere located in hill shade areas which might have affected the data.Therefore, since the station is theonlystationavailableinthearea(Wongpimool,2009),theNongPhlabAgrometeorogical Station could beused as a representativemeteorogical station.The Penman-MonteithEquationwasusedtocalculatethereferenceevapotranspiration(ET0)(FAO,2009).Thearidity indexwas calculated by, firstly,multiplyingthecropcoefficient(Kc)byET0tofindthepotentialevapotranspiration(PET)andthendividingtheannualrainfallbythePETforthearidityindexresult.


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The second factor consisted of three indicators; soilcomposition,soilfertilityandsoilerosion.Thesoilcompositionandthesoilfertilitywereinvestigatedbycollecting59soilsamplesfroma1x1kmgridsizeplotinthestudyarea.However,thesoilerosionindicatorwas investigatedbasedonsix factorsdefinedby theUniversalSoilLossEquation(USLE)whichevaluatedthe long-term average annual soil loss from sheet and rill erosion.Thisisconsideredasuitableempiricalmodelforestimatingsoilerosionbywater(Wijitkosum,2012). The last indicatorwasassociatedwith landuse. The classification of the use of land ismuchmoredifficulttoquantify(Verburget al.,2009).However,RSandGIStechnologycanbeintegratedtoclassifyandmapbothlanduseandlandcoverdatatoidentifypatterns and understand the processes that underlie theobservedpatterns(Lillesandet al.,2008). Inthisstudy,Landsat-5TMsatelliteimagerywasimported into theENVI image processing softwareand the image geo-referencing accuracy was initially checkedwithareferencemapforthearea.BoththeRStechniqueandthefieldsurveywereappliedtointerpretthesatelliteimagestakenbytheLandsat-5TMsatelliteinordertoinvestigatethelanduseofthestudyarea.Theidentifiedlandusecategorieswereclassifiedintofive typesaccording to thenationalcommonsystemoflanduseclassification:forestarea,degradedforest,communityandagriculturalarea,barelandandwaterbodies.

2.2.2. Analysis of the characteristic of factor identifying the critical factors that affect the desertification Data gathered from themapof areas at risk ofdesertificationinPaDenghasbeenusedtoanalyzethecharacteristicsofdesertificationfactors.Theattributedatawas used to asses and construct the frequencydistributionofdifferentlevelsofdesertificationcausedby various factors.The results presented different percentagesintheformofbarcharts.Thesecharacteristics were used to analyze critical factors that affect desertification.Then,theattributedatagatheredfromthemapwasanalyzed inorder toprofile the factorsaffectingthedesertificationusingdescriptivestatisticsmethods(Ferrara,2005).

3. Results and Discussion

3.1. Factors affecting the desertification of the Pa Deng Area

TheAIrangedfrom0.58to1.73whichindicatedthatithadaloworzeroimpactonthedesertificationriskinthestudyarea.TheresultbackedupthestudyconductedbytheLandDevelopmentDepartmentthat

anAIhigher than0.65 typically identifiesacountrylocatedinthetropicalzonebutarenotundertheriskof desertification (LDD, 2002) or drought (Chomtha,2007).Moreover,thestudyofWanget al.,(2003)alsoindicatedthatitisdifficulttoconcludethattherainfallandthearidityindexarekeysfactorsfordesertification.Eventhoughthepotentialevaporationwasincreased,itcouldnotbeimpliedasaprimarycauseofdesertification. Most of the study area (85%of the total area)wasslopecomplexwithslopesexceeding35%.Thedominant soil textures in theplain areawere loamysand. Soil samplingswere collected from the studyareaandexaminedinalaboratory.Theresultsindicatedthat the soil had a moderate level of fertility and a low levelofavailablephosphorus(1.0to1,240.0mg/kg),buthadahighlevelofexchangeablepotassium(20.0to740.0mg/kg),magnesium(7.0to400.0mg/kg)andcalcium(40.0to4,400.0mg/kg)andamoderateleveloforganicmatters(0.52to4.57mg/kg).TheresultswerecomparedwithasoillaboratoryanalysisstandardsetbytheLandDevelopmentDepartmentandDepartmentofEnvironmentalQualityPromotion.Thesoilorganicmatterandthesoiltextureinfluencethewaterholdingcapacityofthesoil.Theeffectpronounceditselfwhenthefinetexturewascoupledwithanappreciableamountoforganicsoilmatter(Adamuet al.,2012).Therefore,the soil texture and soil fertility carried a low level impactonthedesertificationrisk. Thelandwasclassifiedintofivecategories:forest(84.65%oftotalarea),agriculture(14.91%),community area(0.23%),bareland(0.11%)andwaterbodies(0.11%)accordingly (Wijitkosum, 2012).The agricultural andcommunityareaswerelocatedonthecentralplainwhich was found to be at a very high risk of soil erosion (>12,500,000 kg/km2/yr) (Wijitkosum, 2012).ThefactorsthataffectedthedesertificationintheareaareshowninFig.2. Takingallfactorsinconsideration,theassessmentshowed thatmajority of the plain area of PaDengwas at amoderate risk of desertification.However,duetothehighriskofsoilerosionfrominappropriate agriculturalpracticesandthelackofimplementation of soil conservation measures in the area, the desertificationinPaDenghasapotentialtobemoresevere (Wijitkosumet al.,2013).Thedesertificationofanareabeginswhencertainlandcomponentshavebeen brought beyond their specific thresholds andthesechangesmaybeirreversible(Tuckeret al.,1991; Nicholsonet al.,1995).Manymethodologiesdeveloped forcombatingdesertificationweredesignedatregional and global scales.Methods such asmathematicalmodels,parametricequations, remotesensing,direct observation and measurements were invented to combat desertification. Recently, models for assessing


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Table1.Riskleveloffactorsaffectingdesertification

Risklevel DescriptionAridityIndex:AI None >1 Verylow 0.65-1.00 Low 0.50-0.65 Moderate 0.20-0.50 High 0.05-0.20 Veryhigh <0.05Soil texture None Watershed Verylow Buildingsandcommunityarea Low Clay and loam Moderate Shallow soils and organic soils High Sandy loam Veryhigh SandorsoilonslopecomplexSoil fertility None Lowfertilityat5-6points Verylow Lowfertilityat8-7points Low Moderatefertilityat9-10points Moderate Moderatefertilityat11-12points High Highfertilityat13-14points Veryhigh Highfertilityat15pointsLanduse None Watershed Verylow Evergreenforest>70%Ricefield>70% Low Mixedricepaddy50%Fruittreesandperennialplants

50% Moderate Naturalgrasslands High Fieldcropsandotherareas50% Veryhigh Fieldcrops>70%Deciduousforest>70%Soil erosion None Watershed Verylow Verylow(0-1,250,000kg/km2/yr.) Low Low(1,250,000-3,150,000kg/km2/yr) Moderate Moderate(3,150,000-9,400,000kg/km2/yr) High High(9,400,000-12,500,000kg/km2/yr) Veryhigh Veryhigh(>>12,500,000kg/km2/yr)Source:AdaptedfromLDD,2004andSepehretal.,2007

desertification and land degradation have been presented(Sepehret al.,2007).Amongthesemodels,theMEADALUSmodelwas themost suitable for assessingdesertificationriskinAsianregions.Itprovided clear results able to effectively analyze areas at risk of desertification (Gholamet al.,2006;Rangzanet al.,

2008; Farajzadeh et al., 2007). InThailand,most desertificationstudiesfocuson theoverallareasandtakes in specific data such as drought index, soil erosionandthelossofforest(LDD,2003),butspatialanalysiswasnotwidelyconducted.Sinceeachpartofthecountryhasitsownspatialcharacteristics,Thailand


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Figure2.FactorsthataffectthedesertificationinthePaDengarea

Taking all factors in consideration, the assessment showed that majority of the plain area of Pa Deng was at a moderate risk of desertification. However, due to the high risk of soil erosion from inappropriate agricultural practices and the lack of implementation of soil conservation measures in the area, the desertification in Pa Deng has a potential to be more severe (Wijitkosum et al., 2013). The desertification of an area begins when certain land components have been brought beyond their specific thresholds and these changes may be irreversible (Tucker et al., 1991; Nicholson et al.,1995). Many methodologies developed for combating desertification were designed at regional and global scales. Methods such as mathematical models, parametric equations, remote sensing, direct observation and measurements were invented to combat desertification. Recently, models for assessing desertification and land degradation have been presented (Sepehr et al., 2007). Among these models, the MEADALUS model was the most suitable for assessing desertification risk in Asian regions. It provided clear results able to effectively analyze areas at risk of desertification (Gholam et al., 2006; Rangzan et al., 2008; Farajzadeh et al., 2007). In Thailand, most desertification studies focus on the overall areas and takes in specific data such as drought index, soil erosion and the loss of forest (LDD, 2003), but spatial analysis was not widely conducted. Since each part of the country has its own spatial characteristics, Thailand should focus more on the development of research on spatial analysis. The spatial characteristics in Thailand ranges from environmental factors, soil quality to land use activities. These factors greatly affect the characteristics of the problems caused by desertification and should be thoroughly studied.

Figure 3. Desertification risk area in the Pa Deng central plain Figure3.DesertificationriskareainthePaDengcentralplain


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factorhadnoeffect(0.00).Boththesoiltexturefactorandthesoilfertilityfactorhadlowleveleffects(1.00)onthedesertificationinthePaDengarea. From the characteristics, the data showed thatsoil erosion from the changes in land use in the area was themain factor that affected thedesertification. Aprevious study showed that changes in size and patternofthelanduseinfluencedthesoilerosionriskintheareaduringthe1990-2010periods.Fromthestudy,the area with a smaller land cover clearly showed a higher risk of soil erosion than the area with larger land cover(Wijitkosum,2012).Fromthedesertificationrisk assessmentinthePaDengarea,theresultsshowedthatthestudyareacanbedividedintothreedesertificationzonesaccordingtothedesertificationrisklevels;lowriskzones,moderateriskzonesandhighriskzonesasshowninthefollowingbarcharts.Thedatagathered

shouldfocusmoreonthedevelopmentofresearchonspatialanalysis.ThespatialcharacteristicsinThailand ranges from environmental factors, soil quality toland use activities.These factors greatly affect the characteristicsoftheproblemscausedbydesertificationandshouldbethoroughlystudied.

3.2. Critical factors that influence desertification

The characteristics showed that each factor influenced thedesertificationcausesdifferently(Fig.4).Thesoilerosionfactorhaddifferentlevelsofeffectfromaverylowlevel(Level1;1.00)toaseriouslevel(Level5;5.00),butmostareasinthePaDengareawereatmoderate(Level3;3.00)andseriouslevel(Level5).Moreover,thelandusefactoronlyhadamoderateeffect(Level3;3.00)onthedesertification,whiletheclimatic

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Figure4.CharacteristicsoffactorsthataffectthedesertificationinthePaDengarea


94

from these three zones were collected and analyzed to findthecharacteristicsofthecriticalfactorswhichsetthemapart(Fig.5to7) FromFig. 5, the characteristics of factors that affectedthelowriskzonewasthelandusefactor(Fig.5(e);3.00)whichhadamoderateriskeffectonthearea.Thus,thegraphshowedthattheclimaticfactorhadnoeffectonthedesertificationriskwhilethesoiltexture,soilfertilityandsoilerosionhadaloweffectontherisk. Fig.6showedthatcharacteristicsofcriticalfactorsthat affected the desertification in themoderate riskzone.Fig.6(e)showedthatthelandusefactorwasthecritical factor that affected thedesertification (Level3;3.00).Thus,theclimaticfactorhadnoeffectonthedesertification,whilethesoiltextureandsoilfertilityhadaloweffectandsoilerosionhadmoderateeffect. The characteristics of critical factors that affected thedesertification in thehigh riskzonewere shown inFig.7.Thesoilerosion(Fig.7(d))hadaveryhigheffect(Level5;5.00)onthedesertification.However, while the climatic factor had no effect on the

desertification,thesoiltexture,soilfertilityandlandusehadamoderateeffect. The cause of desertificationwas a combinationof factors that changed over time and vary by location (MEA,2005;Wanget al.,2006;Xue,2009).Thesoilerosion was a critical factor that had an effect on the desertificationriskofthePaDengarea.Thehighriskofsoilerosionisapossiblecauseforlanddegradationanddesertification(Dregne,1986;Abahussainet al., 2002;Wanget al., 2006;Cantónet al., 2009;Ravi et al.,2010;Kairiset al.,2013)becausesoilerosionisremovingtopsoil(Abahussainet al.,2002;Yanet al., 2008)anddecreasingnutrientandsoilfertility(Baueret al.,1994)aswellasporosity(Ebeidet al.,1995).Moreover,thechangingoflanduseaffectstheintensityofrunoffsoilerosion(Wanget al.,2005;Cebecauer et al.,2008;Garcia-Ruiz,2010).Thisisaresultoftheforestareasbeingconvertedintomonocroppingplotswhich have reduced and have destroyed both the land coverandthevegetationcover.Moreover,theagricul-turists in the areas did not follow the soil conservation shown i

analyzed

Figure 5.

factor (Fclimatic erosion h

the modaffecteddesertifmodera

in the followd to find the

. Characteristi

From Fig. 5Fig. 5(e); 3.0

factor had had a low efFig. 6 showderate risk d the desertfication, whate effect.

wing bar chacharacteristi

ics of factors a

5, the charac00) which hano effect on

ffect on the riwed that chazone. Fig. 6tification (L

hile the soil

arts. The daics of the crit

affecting the l

cteristics of fad a moderatn the desertifisk.aracteristics6(e) showedLevel 3; 3.texture and

ata gathered tical factors w

low desertifica

factors that te risk effect fication risk

s of critical d that the la00). Thus, d soil fertil

from these which set the

ation risk zon

affected the on the area.while the s

factors thatand use facthe climatiity had a lo

three zonesem apart (Fig

e

low risk zo Thus, the goil texture,

t affected thctor was theic factor haow effect an

s were colleg. 5 to 7)

one was the graph showedsoil fertility

he desertifice critical facad no effectnd soil eros

ected and

land use d that the

and soil

cation in ctor that t on the sion had

Figure5.Characteristicsoffactorsaffectingthelowdesertificationriskzone


95

measures closely which resulted in a high rate of soil erosion (Wijitkosum, 2012) thatmight have furtheraffectedthecausesofdesertification.

4. Conclusions

Desertificationisamultifacetedissuecausedbyavariety of climatic factors and human activities which needs to be examined fromvarious aspects (UNEP,1992;FAO,1993;Wallace,1994;Gray,1999;Warren, 2002; Chen andTang, 2005).Many studies have identifiedhumanasakeyfactorofcausingdesertification inmanypartsofAsia (Zhuet al., 1981;Sun,2000;ChenandTang,2005;Wanget al.,2006)despitethefact that it may be triggered by both human activities andnaturalcauses.InPaDeng,themajorityoftheplainarea(9.14%ofthetotalarea)wasatamoderateriskofdesertificationduetothesoilerosionproblems.Using US andGIS techniques alongwith amathematicalmodelmay provide variations on the location and

Figure 6.

were shdesertifisoil ferti

locationeffect onfor landCantón(Abahus1994) asof runofof the foboth thethe soil 2012) th

. Characteristi

The characthown in Fig.ication. Howility and landThe cause o (MEA, 2005n the desertif

d degradationet al., 2009;

ssain et al.,s well as porff soil erosionorest areas be land cover

conservatiohat might hav

ics of factors a

teristics of c. 7. The soil

wever, while td use had a mf desertificat5; Wang et afication risk n and deserti; Ravi et al.2002; Yan eosity (Ebeid n (Wang et aeing convertand the vegen measures

ve further aff

affecting the m

critical factorl erosion (Fthe climatic f

moderate effetion was a coal., 2006; Xuof the Pa De

ification (Dr, 2010; Kairet al., 2008)et al., 1995)

al., 2005; Ceted into monetation coverclosely whi

fected the cau

moderate dese

rs that affecig. 7(d)) hadfactor had noect.ombination oue, 2009). Theng area. Th

regne, 1986; ris et al., 20) and decrea). Moreover,ebecauer et anocropping pr. Moreover,ich resulted uses of deser

ertification risk

cted the desed a very higo effect on th

of factors thahe soil erosiohe high risk o

Abahussain13) because

asing nutrien the changinal., 2008; Gaplots which h, the agricultin a high ra

rtification.

k zone

ertification ingh effect (Lhe desertifica

at changed oon was a critiof soil erosio

et al., 2002soil erosion

nt and soil feng of land usearcia-Ruiz, 2have reducedturists in theate of soil e

n the high revel 5; 5.00

ation, the soi

over time andical factor thon is a possib2; Wang et an is removinfertility (Baue affects the

2010). This id and have de areas did noerosion (Wij

risk zone 0) on the il texture,

d vary by at had an ble cause al., 2006; g topsoil

uer et al.,intensity s a result

destroyed ot follow jitkosum,

Figure6.Characteristicsoffactorsaffectingthemoderatedesertificationriskzone

theseverityofthedegradationwithinaregion,butitdoesnotrevealwhatcausedthedesertification(Ellis et al., 2002).Basedoneachindividualsituationandits severity, differentmethods should be employed toprevent and solve the problems. This proves the significance of spatial research on desertification. Analyzing critical factors that affect the risk of desertification, the results showed that soil erosionwasthecriticalfactorthataffectsthedesertificationinPaDengarea.InThailand,soilerosionbywaterhasbeenconsideredasoneoftheprimarycausesofland degradationduetolossofsurfacesoilandplantnutrients(LDD,2000).However,thisstudyrevealedthatthelanduse factor is another key factor that contributed to the soilerosionprobleminthearea(Wijitkosum,2012).The land use factor refers to changes in the ways men utilize the natural resources including overgrazing,landclearing,overcropping,cultivatingmarginallandsandusingalandinaninappropriatewayforitslocalconditions(Abahussainet al., 2002;Zhouet al.,2008;


96

MohammadandAdam,2010).Theresultsobtainedwillbeusedforplanningmitigationmeasuretocopewiththesoilerosionproblemsinthestudyarea.Moreover,themitigationmeasuresforthedesertificationinthePaDeng area should also include the monitoring of land use.Inordertopreventthesoilerosionbothmechani-cal measures and agronomic measures should be taken intoaccountincludingcontourcultivation,tiedriding,bedding and terracing, cover cropping,mulching, intercropping and vetiver grass growing. These mitigations are highly recommended for the agricultural area(Wijitkosum,2012). Theimplementationofsoilconservationmeasureshas not beenwidely applied inThailand due to the shortage ofwell-trainedman power and financial support.However, since the spatial studyof thePaDengareawasconductedunder theprojectofHuaySaiRoyalDevelopmentStudyCentre, the resultsof

this studywill be forwarded to theHuaySaiRoyal Development StudyCentre and relevant agencies as resources for the establishment and the implementation of soil conservationmeasures andmanagementoflanduse.

Acknowledgements

The financial support was provided by the RatchadaphiseksomphotEndowmentFundofChulalongkornUniversity(RES560530094-CC),ClusterClimateChange,ChulalongkornUniversity.

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Received 4 March 2014Accepted 7 April 2014

Correspondence toDr.SaowaneeWijitkosumEnvironmentalResearchInstitute,ChulalongkornUniversity,Bangkok10330,ThailandE-mail:[email protected]


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