Spatial variation of soil organic carbon in damavand rangelands

Transcription

1 Joural of Biodiversity ad Evirometal Scieces (JBES) ISSN: (Prit) (Olie) Vol. 5, No. 3, p , RESEARCH PAPER OPEN ACCESS Spatial variatio of soil orgaic carbo i damavad ragelads M. Dadgar, E. Zadi Esfaha 2*, M.R. Sheykh Rabiee 3 Departmet of Soil Scieces, Roudehe Brach, Islamic Azad Uiversity, Tehra, Ira 2 Ragelad Research Divisio, Research Istitute of Forests ad Ragelads, Tehra, Ira 3 Departmet of Agriculture & Natural Resources, Uiversity of Applied Sciece ad Techology, Tehra, Ira Article published o September 03, 204 Key words: clay percet, soil orgaic carbo, spatial distributio. Abstract Sustaiable maagemet of ecosystems requires the uderstadig ad evaluatio of spatial ad temporal variatios of its characteristics for the optimal ad sustaiable utilizatio of resources. For this purpose, uderstadig the spatial distributio of soil properties is of utmost importace. Therefore, the preset research was aimed to ivestigate the spatial variatio of soil orgaic carbo i a part of Damavad Ragelads. I this regard, soil samplig was performed from 0-30 cm soil depth ad the amout of soil orgaic carbo, total itroge cotet, the percetage of clay, sad ad silt, ph, ad bulk desity was measured. To ivestigate the spatial variatios, geostatistical methods icludig Ordiary Krigig (OK), Cokrigig, ad Iverse Distace Weightig (IDW) were evaluated. Cross Validatio techique ad statistical parameters of RMSE, MAE ad MBE were also used. Accordig to the results, spherical model was selected as the best-fit model for the semivariogram of orgaic carbo with a effective radius of 500 meters, a ugget effect of 0.02% ad a sill of 0.025%. I the cokrigig method, clay cotet was used as a covariable for predictig SOC (P< 0.0, r= 0.838**(. Accordig to the variogram aalysis, a spherical model with a effective radius of 000 meters, a ugget effect of 0.085% ad a sill of 0.65 was selected. The correlatio coefficiet of the model was calculated to be The obtaied results showed that the cokrigig method had smaller errors (RMSE=0.020) as compared to the other two methods. Therefore, this method was used for mappig soil orgaic carbo. * Correspodig Author: Esfaha Zadi Esfaha zadiesfaha@gmail.com 72 Dadgar et al.

2 Itroductio Ragelads are cosidered as oe of the most importat lad ecosystems for carbo sequestratio. Although the amout of carbo sequestratio per uit area is egligible, ragelads have high potetial for carbo sequestratio due to their large area (Schuma et al.,2002). Sustaiable maagemet of ecosystems requires the uderstadig ad evaluatio of spatial ad temporal variatios of its characteristics for the optimal ad sustaiable utilizatio of resources. Maitaiig soil quality is amog the most importat factors cotributig to the sustaiable maagemet of ecosystems. For this purpose, uderstadig the spatial distributio of soil properties is of utmost importace (Sarmadia ad Taghizadeh, 200). To ivestigate the spatial variatios of carbo sequestratio, geostatistics ca be used. From a geostatistical stadpoit, each sample ca have spatial relatioship with its surroudig samples to a maximum distace (spa). This maximum distace, called effective radius, is of great importace. Actually, it idicates the distace i which geostatistical estimators could be used (Hasaipak, 2008) ad the factors affectig effective radius should be determied. Zhag ad McGrath, 2004 ivestigated ad aalyzed the spatial variatio of soil orgaic carbo i a ragelad regio at South-East Irelad usig geostatistical methods icludig Krigig, classical statistics ad GIS. Samplig was performed o a grid of 0 0 km ad the outliers were detected ad removed with Mora I idex. Results showed that geostatistics had a good ability to iterpret spatial ad temporal chages i soil orgaic carbo ad the effect of geology ad topography was more tha ay other factors explaiig the distributio of soil orgaic carbo. Simbaha et al., 2006 prepared the carbo distributio map usig multivariate sources ad secodary data. I this regard, Ordiary Krigig (OK), Cokrigig (COK), ad Regressio Krigig (RK) were used. The electrical coductivity of each soil series ad elevatio maps were used i preparatio of spatial distributio patter of carbo. I additio, electrical coductivity was detected as a very helpful factor for carbo mappig. To reduce the ucertaity, it was suggested to perform idepedet measuremets ad multivariate secodary data i the regressio krigig (RK) be used for soil orgaic carbo mappig. I a study, Liu et al., 2006 ivestigated the distributio of soil orgaic carbo ad the effect of lad use, soil ad topography o farmlads usig GIS ad classical geostatistics. Data were fitted with logormal distributio ad the expoetial variogram model was used. Classificatio method was used to ivestigate the effect of lad use, soil type, elevatio ad slope. I additio, ANOVA ad mea compariso were performed to compare the meas of differet classes. Lufafa et al., 2008 reported that geostatistics could be accurately used to estimate the amout of carbo storage. I this study, samples were take from a depth of 20 cm ad geostatistics was used to quatify the scale ad degree of spatial depedece of soil carbo. Soil carbo variogram, represetig a moderate spatial depedece, had a correlatio of less tha i tree platig areas ad showed a closer relatioship with soil carbo levels as compared to shrub platig areas. I aother study, Vasques et al., 200 measured the total carbo cotet of four depths icludig 0-30, 30-60, ad cm ad preseted a model of spatial distributio of carbo. I this research, ANOVA was used ad regressio block Krigig was compared with logormal block Krigig. Soil depth, lad use, soil type, soil draiage class ad geological uit affect the total carbo cotet of soil. 73 Dadgar et al.

3 The majority of evirometal factors have spatial correlatio with the spatial distributio of total carbo. I three soil surface depths, regressio Krigig performed better tha block Krigig, idicatig that i most cases, evirometal factors were determiats for spatial distributio of carbo. As a result, a spatial distributio patter was geerated i the study area (Florida), which provided iformatio for soil coservatio i Florida ad similar coditios i Southeast America ad other regios. I a research coducted by Amirejad et al., 20, soil properties icludig bulk desity, saturated hydraulic capacity, available water holdig capacity, ad orgaic carbo percetage were measured i rice ad wheat cultivated lads. The obtaied results were differet betwee the two cultures ad ordiary Krigig was used to estimate the soil properties due to lower error. Meawhile, Gaussia was determied as the best model for estimatig orgaic carbo. The use of appropriate techiques for spatial evaluatio ad determiig the role of physical ad maagemet factors i spatial distributio of soil quality properties ad i particular soil orgaic matter as well as its destructio or sequestratio is ecessary. However, very little research has bee doe o spatial modelig as a basic tool, required for soil maagemet. Therefore, this research was aimed to ivestigate the amout of soil orgaic carbo accumulatio i the regio ad produce distributio map. Materials ad methods Study Area Characteristics The study area is located i ortheast of Tehra. It lies betwee logitudes 5 59' ''E ad 52 2' 37''E ad latitudes 35 38' ''N ad 35 40' 33''N. The altitude of the study area varies betwee 800 to 2200 m a.s.l. The total area is 40 hectares. At this stage, iitially maps ad other iformatio of the study area were prepared by library studies ad or referrig to relevat istitutios. I this regard, all existig maps icludig topography, soil, climate, geology, lad use, together with aerial photos ad satellite images of ETM+ 2002, IRS 2007, ad MODIS 200 were collected, Some of copied iformatio was digitized. Some maps or secodary data icludig DEM map, slope, aspect, ad lad use were also prepared from the metioed maps o a scale of : Samplig poit selectio The, accordig to the iformatio, lad uit map was produced for samplig ad field studies. After determiig the poits ad coveyig the trasferrig to GPS, surface samplig was performed from a depth of 0-30 cm (plowig depth). After dryig the samples i air, they were groud ad passed through a two-millimeter sieve. Laboratory aalysis Soil physical ad chemical characteristics were measured icludig soil texture by hydrometer method as well as by soil texture triagle (the percetage of sad, silt ad clay), orgaic matter by the Walkley ad Black method, soil acidity usig a ph meter, lime with eutralizatio method usig hydrochloric acid ad titratio method, ad bulk desity by the clod method (liquid paraffi).( Ali Ehyaei ad Behbehai Zade, 993). Statistical ad geostatistic aalysis To estimate the spatial variatio of soil orgaic carbo at ot samplig poits, geostatistical iterpolatio techiques, icludig Krigig, weighted movig average, ad cokrigig were used usig ARCGIS software ad the layer was prepared after geostatistical calculatios. To evaluate the iterpolatio methods, cross validatio techique ad statistical parameters, MBE ad MAE were calculated. Whe MAE ad MBE are equal or close to zero, this idicates that, the used method simulates the fact well while takig distace 74 Dadgar et al.

4 from zero shows the low accuracy or large deviatios. MAE ad MBE were calculated by Equatios ad 2, respectively: MAE Z * Z () MBE Z * Z (2) Root mea square error (RMSE) was also calculated by Equatio 3. RMSE i ( Z Z*) 2 (3) Methods used i estimatig the amout of soil orgaic carbo icluded ordiary krigig, Iverse distace weightig ad cokrigig. For geostatistical iterpolatio (krigig ad cokrigig), data were ormalized by logarithmic trasformatio ad the iterpolatio was performed o them. To select the most appropriate fitted model to the experimetal semi-variogram ad other features of semi-variogram, differet models were evaluated usig cross validatio. Differet models with varyig parameters were selected ad after the implemetatio of krigig or cokrigig, the models with lower estimated error were selected. To ivestigate the spatial structure, semi-variogram, represetig the average spatial variatio of soil orgaic carbo, was used. Results ad discussio The characteristics of descriptive statistics for the collected samples are discussed here.values of miimum, maximum, mea, variace, stadard deviatio, coefficiet of variatio, SD, skewess ad kurtosis for the etire basi are preseted i Table. Table. Descriptive aalysis of soil orgaic carbo. coefficiet variatio 0.50 Std. Deviatio 0.22 Max 0.92 Mi 0.8 Kurtosis 2.4 Skewess 0.07 Media 0.40 Mea 0.44 Normal distributio of data is essetial for the iterpolatio of some geostatistics methods. I this study, ormality was cosidered i order to map the spatial variability of data ad i particular, determiig the spatial distributio of soil orgaic carbo. If the values of skewess ad kurtosis are closer to zero, the data distributio will be closer to ormal. Accordig to the variography aalysis, effective radius, ugget effect ad sill were calculated to be 500 meters, 0.02% ad 0.025%, respectively (Fig. ). A correlatio coefficiet of 0.94 was calculated for the fitted expoetial model. Fig.. Soil orgaic carbo variogram. Several factors may affect the distributio of soil orgaic carbo, amog which the percetage of itroge ad clay could be metioed. Accordig to the results, the highest sigificat correlatio was foud betwee soil carbo ad clay (P<0.0, r=0.838 ** ). The expoetial model was fitted to the semivarogram of clay with a effective radius of 000 m, a ugget effect of 0.085% ad a sill of 0.65% (Fig. 75 Dadgar et al.

5 2). The scatter plot of estimated ad observed values is preseted i Fig. 3. Fig. 2. Soil orgaic carbo ad clay covariogram. Fig. 4. Orgaic carbo zoig map by Cokrigig method i the study area. Fig. 3. Scatter plot of estimated ad measure values i cokrigig iterpolatio method for soil orgaic carbo data. To select the proper geostatistical methods to estimate the amout of soil orgaic carbo, the deviatio ad accuracy of these methods were evaluated ad results are preseted i Table 2. Accordig to Table 2, cokrigig method has less error ad deviatio as compared to krigig ad weighted movig average methods. Therefore, cokrigig method was selected as appropriate model for estimatig of soil orgaic carbo ad soil orgaic carbo map was draw (Fig. 4). Table 2. Evaluatio of used methods for estimatig soil orgaic carbo. Methods MBE MAE RMSE IDW Krigig Cokrigig Accordig to the map prepared based o average orgaic carbo, i geeral, the regio faces a shortage of soil orgaic carbo so that i most of the study area the percetage of orgaic carbo accumulatio is less tha 0.6% ad the amout of vegetatio i these areas is less. Wag et al., 2009 determied the distributio of soil orgaic carbo i the lads of North East Chia usig ordiary krigig. Samplig was systematic ad spherical was idetified as appropriate variogram model. Results showed that maximum carbo accumulatio was recorded for the regios havig lower altitude ad more vegetatio. These fidigs were i cosistece with the distributio of orgaic carbo i Damavad. Law et al., 2009 itroduced ordiary krigig as the best iterpolatio method. Expoetial ad or spherical were idetified as appropriate variogram model. Parvizi, 200 also used iterpolatio method for estimatig soil orgaic carbo i the etire Karkheh watershed. Results showed that ordiary krigig, cokrigig with covariable of lime percetage, ad iterpolatio usig RBF had the highest accuracy. 76 Dadgar et al.

6 Geostatistical methods, havig a high correlatio coefficiet ad low error, could be used i the estimatio of soil orgaic carbo. Cokrigig, with a effective radius of 000 m, ad expoetial variogram model showed the highest accuracy i the zoatio of soil orgaic carbo. Geostatistical methods are evaluated by cross validatio techique. However, it is recommeded to evaluate other geostatistics methods icludig fuzzy krigig. Refereces Ali Ehyaei M, Behbehai Zade AA Methods of Soil Chemical aalysis. Soil ad Water Research Istitute of Agricultural Extesio ad Educatio, Amiriejad AA, Kamble K, Aggarwal P, Chakraborty D, Pradha S, Mittal RB. 20. Assessmet ad Mappig of Spatial Variatio of Soil physical health i a Farm, Geoderma 60, Hasaipak AA Geostatistic.Tehra Uiversity publicatio Law M C, Balasudram SK, Husi M H A, Ahmed O H, Haru M H Spatial variability of soil orgaic carbo i oil palm, Ite. J. Soil. Sci Liu D, Wag Z, Zhag B, Sog K, Li X, Li J, Li F, Dua H Spatial distributio of soil orgaic carbo ad aalysis of related factors i croplads of the black soil regio, Northeast Chia, Agriculture, Ecosystems ad Eviromet 3, Lal R. 20. Sequesterig carbo i soils of agroecosystems. Food Policy, 36, S33 S39. Lufafa A, Diédhiou I, Samba S, Séé M, Khouma M, Kizito F, Dick R P, Dossa E, Noller JS Carbo stocks ad patters i ative shrub commuities of Seegal's Peaut Basi, Geoderma 46, Parvizi Y Zoig spatial variability of soil orgaic carbo ad the effect of physical ad maagerial factors that aalysts use multivariate ad artificial eural etworks. PhD Thesis, Depar Agr Egi Techo, Tehra U, Ira, Sarmadia F, Taghizadeh M Developmet of Pedotrasfer Fuctios to Predict Soil Hydraulic Properties i Golesta Provice, Ira, 9th World Cogress of Soil Sciece, Australia. Schuma GE, Jaze HH, Herrick J E Soil carbo Dyamics ad Potetial carbo Sequestratio by Ragelad, Evirometal Pollutio 6, Simbaha G, Doberma A, Goovaerts P, Pig J, Haddix M Fie-resolutio mappig of soil orgaic carbo based o multivariate secodary data, Geoderma 32, Vasques GM, Gruwald S, Comerford NB, Sickma JO Regioal modelig of soil carbo at multiple depths withi a subtropical watershed, Geoderma 56, Wag M, Zhag B, Sog KS,Liu DW, Re CY Spatial variability of soil orgaic carbo uder maize mooculture i the Sog-Ne Plai, Northeast Chia, Pedosphere 20, Zhag C, McGrath D Geostatistical ad GIS aalyses o soil orgaic carbo cocetratios i grasslad of southeaster Irelad from two differet periods, Geoderma 9, Dadgar et al.