land use changes and soil redistribution estimation using 137cs in the tropical bera lake catchment,...

Soil & Tillage Research 131 (2013) 1–10

Land use changes and soil redistribution estimation using 137Cs in thetropical Bera Lake catchment, Malaysia

Mohammadreza Gharibreza a,b,*, John Kuna Raj a, Ismail Yusoff a, Zainudin Othman c,Wan Zakaria Wan Muhamad Tahir d, Muhammad Aqeel Ashraf e

a Department of Geology, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysiab Soil Conservation and Watershed Management Research Institute, P.O. Box 13445-1136, Tehran, Iranc Department of Geography and Environment, Sultan Idris University of Education, Tanjung Malim, Perak 35900, Malaysiad Isotope & Tracer Application Group (e-TAG), Division of Environment and Waste Management, Malaysian Nuclear Agency (Nuclear Malaysia), Bangi, 43000 KAJANG, Malaysiae Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia

A R T I C L E I N F O

Article history:

Received 15 September 2012

Received in revised form 9 December 2012

Accepted 18 February 2013

Keywords:

Bera Lake catchment137Cs radionuclide

Land use changes

Proportional model

Soil redistribution

A B S T R A C T

The catchment of Bera Lake in Pahang State, Peninsular Malaysia has experienced severe land use

changes since 1972 with some 340 km2 (out of a total area of �600 km2) having been converted to oil

palm and rubber plantations and in some places, newly cleared for monoculture. The proportional model

using the 137Cs radionuclide was recognized as being the most suitable conversion model for estimating

soil redistribution in the catchment as the deforested land has been cultivated once in a medium-term

range of 30–40 years. Thirty-five bulk core soil samples were taken to a depth of 25 cm in areas of

different land use and known dates of tillage commencement in the catchment. Ten bulk core samples

were also collected in the bottom sediments of wetlands and open waters to estimate accumulation rates

in these sink areas. Individual land development districts with known elapsed times from start of tillage

allowed determination of soil redistribution rates and preparation of a soil redistribution map. A mean

soil erosion rate of 915 � 345 t h�1 y�1 was determined in areas of cleared land, whereas rates of 117 � 36,

and 70 � 35 t h�1 y�1, were determined in areas of developing, and developed, oil palm and rubber

plantations, respectively. The overall accumulation rate of eroded soils within the wetlands and open waters

was determined to be 1.025 cm y�1 since 1995. The Bera Lake catchment soil redistribution map is the first

attempt in Malaysia to map soil redistribution using the 137Cs technique on a catchment scale. The soil

redistribution map will provide good guidelines for future soil conservation practices and sustainable land

use programs.

� 2013 Elsevier B.V. All rights reserved.

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1. Introduction

Land use changes including deforestation and land clearing areplaying an important role in soil degradation and soil loss incatchment areas throughout the world. There is also a long historyon the application of on-ground erosion plot experiments andfallout 137Cs and 210Pb to estimate soil redistribution (Walling,1999). Cesium 137Cs is a fission product and atomic bomb-derivedradioisotope that has a half-life of 30.02 years and emits gammarays with an energy of 661.6 keV (Poreba, 2006). This radionuclide

* Corresponding author at: Soil Conservation and Watershed Management

Research Institute, P.O.Box: 13445-1136, Tehran, Iran. Tel.: +98 021 44901214;

fax: +98 021 44905709.

E-mail addresses: [email protected], [email protected]

(M. Gharibreza), [email protected] (J.K. Raj), [email protected] (I. Yusoff),

[email protected] (Z. Othman), [email protected]

(W.Z.W.M. Tahir), [email protected] (M.A. Ashraf).

0167-1987/$ – see front matter � 2013 Elsevier B.V. All rights reserved.

http://dx.doi.org/10.1016/j.still.2013.02.010

was first applied by Yamagata et al. (1963) and Rogowski andTamura (1970) to estimate rates of soil erosion. Analytical methodsand models for estimating soil erosion using 137Cs have remarkablyimproved over the last four decades. Ritchie (2005) has stated thatpublished papers on the 137Cs technique started in 1961 andreached a maximum number in 1999. New models for estimatingsoil erosion have also been introduced by IAEA (1995, 1998),Rogowski and Tamura (1970), Walling and Quine (1990), Wallingand He (1999), Walling et al. (1999), Zapata and Garcia (2000), andPoreba (2006). Mabit et al. (2008a) have evaluated the differentmodels and noted the advantages and limitations of using 137Csand 210Pb for assessing soil erosion. The 137Cs technique is the onlytechnique that can be applied both quickly and efficiently tomeasurements of soil loss and redeposition (Ritchie, 2005). A PC-compatible software package by Walling et al. (1999) contains animproved model that is based on a number of other models and isapplicable to both cultivated and non-cultivated areas and caninclude contributions from fallout radionuclides 210Pb and 7Be. The


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M. Gharibreza et al. / Soil & Tillage Research 131 (2013) 1–102

said software comprehensively runs the Proportional Model, theMass Balance I, II, and III Models, the Profile Distribution Model andthe Diffusion and Migration Model. Specific requirements are,however, needed in applying the models in terms of the underlyingassumptions, descriptions and representation of temporal varia-tion (Walling et al., 1999).

Studies on the Bera Lake catchment and its open water startedin 1961 due to its scientific, anthropological and agriculturalimportance. Biological features of the catchment have beenstudied by Merton (1962), Furtado and Mori, 1982, Ikusima andFurtado, 1982, and Giesen (1998), while its palynological historyand anthropological aspects have been investigated by Morley(1981), and Surut (1988), respectively. The geological setting andevolution of the Bera Lake basin has been presented in Hutchisonand Tan (2009), whilst peat accumulation and more recentpalynological aspects were studied by Phillips and Bustin(1998), Wust and Bustin (1999), Wust and Bustin (2001), andWust et al. (2002).

A literature review indicated that the 137Cs technique has neverbeen applied to estimating soil redistribution patterns in the BeraLake catchment even though there have been severe land usechanges over the past few decades. The objective of this researchwas therefore, determination of the soil redistribution pattern as aresult of land use changes within the Bera Lake catchment usingthe 137Cs fallout technique. The capability of application of the137Cs method toward soil redistribution mapping in a humidtropical catchment was also another objective of the research.

1.1. Study area

Bera Lake catchment (BLC) is located in the central part ofPeninsular Malaysia, between 28, 530, 0000–38, 100, 0000N and 1028,300, 3000–1028, 470, 0000E (Fig. 1). The catchment covers an area ofsome 600 km2 and was covered by primary rainforest, though fiveFederal Land Development Authority (FELDA) schemes from 1970to 1995, have led to 292.86 km2 of the original forest beingconverted to oil palm and rubber plantations (Henson, 1994;MPOC, 2007). The BLC was designated under the Convention of

Fig. 1. Geographic position of Bera Lake catchm

Wetlands as the first RAMSAR Site in Malaysia in 1994 with theFELDA districts being called Buffer Zones. Soil conservationmanagement practices, however, have never really been appliedwithin these Buffer Zones, both before, and after, establishment ofthe RAMSAR Site. A map showing recent land use in the Bera Lakecatchment, prepared using the geographical information system(GIS) technique and a satellite image (Spot 5, 2009) of spatialresolution 10 m furthermore, shows that there has been iscontinued agricultural development and encroachment into theRAMSAR Site with new oil palm and rubber plantations (Fig. 2).Cleared land has also increased some 47.14 km2 in area since 1994;reaching a maximum area of 340 km2 in 2009. The remaining areais covered by wetlands and pristine lowland rain forests (forest andreed swamps). The catchment is located between the eastern andwestern mountain ranges of the Peninsula with the highest hillsbeing up to 140 m above sea level (Wust and Bustin, 2004). Adigital elevation model (DEM), developed to prepare a slope map ofthe catchment, shows that up to 50% of the area comprises lowlands where the slope varies between 08 and 48.

The Bera Lake catchment was segregated into 12 hydrologicalsubcatchments with open water located in the northernmost partin subcatchment 3 (Fig. 1). The overall flow of streams isnorthwards with subcatchments 4–12 draining into the southend of Bera Lake. Two other streams from subcatchments 1(Kelangton stream), and 2, drain into the middle, and northernparts, of the Lake, respectively. Bera Lake drains through an outletstream in its northern most part into the Bera River which flowsnorthwards into the Pahang River.

The study area has a humid tropical climate with two monsoonperiods. Heavy rainfall is received during the Northeast (Novemberto March), and Southwest (June to August), Monsoons, whist there isless rain in April and May and in September and October. The meanannual temperature is about 30 8C and ranges from 25 8C to 38 8C(Chee and Abdulla, 1998). Rainfall records from 1970 to 2009 at theFort Iskandar Station, which is located at the mid-point of the BeraLake catchment, show that minimum, and maximum, annualrainfall are 1000, and 2602, mm respectively. Field observations andlaboratory analyses show the soils of the BLC to be Ferralsols; the

ent, subcatchments, and stream pattern.

Fig. 2. Land use scheme and soil sampling position.

M. Gharibreza et al. / Soil & Tillage Research 131 (2013) 1–10 3

soils with brownish yellow, yellow and red colors, having developedon Triassic and post Triassic continental sedimentary rocks. TheseFerrasols have maximum, and average, thickness of 1, and 0.2, m,respectively.

In the study area are found thick bedded to massive mudstone,tuffaceous sandstone and siltstone of the Permian Bera Formationthat are unconformably overlain by carbonaceous shale, siltstoneand rhyolitic tuff of the Triassic Semantan Formation. TheSemantan Formation is overlain by post Triassic conglomerate,pebbly sandstone and sandstone of the Redbed Formation(Hutchison and Tan, 2009). Outcrops show the rock strata atBLC to be located on the right flank of a wide NW-SE trendingsyncline; the beds dipping 45–608 toward SE. Organic-rich andpeat deposits have accumulated in the wetlands and open watersof Bera Lake since 4500 BP (Morley, 1981).

2. Materials and methods

2.1. Sampling

Sampling procedures for estimating soil erosion using the 137Cstechnique is a privileged sampling method among other samplingmethods (Mabit et al., 2008a). In the other words, the samplingmethod is relatively simple and cost-effective and can becompleted in a short time, depending on the sampling densityand size of investigated area. Site disturbance during sampling isalso minimal and will not interfere with seeding and cultivationactivities. There is furthermore, no disturbance of natural runoffand erosional processes, such as might occur with bounded erosionplots (Mabit et al., 2008a). Soil redistribution estimation isachieved by comparing the 137Cs inventory at individual samplingpoints with a reference inventory from a site representing the localfallout input and where there has been neither erosion nordeposition. A measured inventory value at an individual samplingpoint that is less than the reference value is thus indicative oferosion, whereas an inventory value greater than the referencevalue would indicate deposition.

Obviously the successful soil erosion estimation of a catchmentwill depend on the setting-up of a proper sampling strategy. This

strategy furthermore, depends on deforestation and tillagecommencement dates, the lithology of parent rocks, and theintrinsic 137Cs inventory and site accessibility in any area. In otherwords, each sample is an indicator of a certain land use with aspecific tillage date is area of different deforestation phases.Thirty-five bulk samples were taken to a depth of 25 cm with acore sampler of 11 cm diameter at sites of different land use(Fig. 2). Ten bulk core samples of 5 cm diameter were also takenfrom bottom sediments in the wetlands and open waters toidentify the fate of eroded soil and sedimentation rate in sinkareas. At each sampling site, six cores of 95.4 cm2 in cross-sectional area were collected because of the low 137Cs activity intropical areas, including Malaysia. Nine sites in the original andprotected rain forest (RAMSAR Site) area served as locations areasfor reference samples. The chosen reference sites were open areaswith slope gradients of 0 to 2 degrees and did not show anyevidence of erosion or sedimentation. Incremental depth sam-pling to measure 137Cs activity with depth at the reference siteswas carried out at 2 cm intervals using a scrapper plate with acutting edge and having a rectangular metal frame of 875 cm2 inarea. The sampling was carried out to a depth of 25 cm where rockfragments were the main soil component and there was only asmall clay fraction.

2.2. Sample preparation and analytical method

The bulk and dry densities of the cylindrical core samples weredetermined after they had been dried at 105 8C and weighed. Thesamples were then finely ground and packed in special containersof 1 L capacity. The 137Cs specific activities were then measuredusing a well calibrated gamma-spectrometry based on hyper puregermanium (HpGe) detectors in the laboratories of NuclearMalaysia. The gamma-spectrometer model GCW2523, (Canberra)detector at Nuclear Malaysia had a relative efficiency of 27% andfull width at half maximum (FWHM) of 2.04 keV for 60Co gamma-energy line at 1332 keV. The gamma-spectrometer was calibratedusing multinuclides standard (NIST) solutions in the same sample– detector geometry (1 L Marinelli beaker). The lower limit ofdetection, with 95% confidence, is 0.3 Bq kg�1 for 24 h measuring


time. IAEA reference sample IAEA = QA2-326 was used for qualitycontrol of the gamma-spectrometer and its calibration.

2.3. Conversion Models

Assumptions for applying conversion models were firstidentified according to the land use pattern in the Bera Lakecatchment. It is important to recognize that individual modelshave differences in their underlying assumptions, processesdescriptions and representations of temporal variation. A briefdescription of the mass balance I, II, and III models as well as theproportional model are here discussed as these models have beenused to estimate soil erosion and deposition in cultivated landswith different lands use (Walling et al., 1999).

2.4. Mass balance model I

This simplified mass balance model takes into account theprogressive reduction in the 137Cs concentration of soil within theplough layer due to the incorporation of soil with negligible 137Csfrom below the original plough depth. This model is easy to applyand only requires information on the ploughing depth. This model,however, does not take into account the possible removal of freshlydeposited 137Cs fallout by erosion before its incorporation into theplough layer by cultivation. The assumption that the total 137Csfallout input occurs in 1963 is also an over-simplification (Wallinget al., 1999).

2.5. Mass balance model II

The mass balance model (II) takes into account both thetemporal variation in 137Cs fallout input and the initial distributionof fresh fallout on the surface soil. Results from this model arelikely to be more realistic than those provided by the simplifiedmass balance model I. However, information on the plough depth,the relaxation mass depth H and parameter g is required in order touse this model (Walling et al., 1999).

2.6. Mass balance model III

The mass balance models I and II do not take account soilredistribution introduced by tillage. As tillage results in theredistribution of soil in a field, the 137Cs contained in the soil willalso be redistributed and needs to be taken into account whenusing 137Cs measurements to estimate rates of soil erosion bywater. If the effects of tillage redistribution on 137Cs inventoriescan be quantified and taken into account, the remainingcomponent of redistribution will reflect the impact of watererosion. The results from this model are likely to be closer to realityfor cultivated soils than those from the other two mass balancemodels. However, to employ this model, additional information isneeded (Walling et al., 1999).

2.7. Proportional model

The need for several assumptions in applying the conversionmodels indicated that the proportional model was the best modelfor the present study in view of the land use pattern in the BeraLake catchment. FELDA districts in the Bera Lake catchment hadfirst been cleared of natural forest and exposed before beingplanted with, and subsequently covered once by, oil palms orrubber trees for a medium-term length of 30–40 years. Otherconversion models could be not applied under these conditions asthe models assume annual cultivation or cultivation in most yearswith the result that the soil is well-mixed with 137Cs uniformlydistributed within the plough layer. The proportional model

calculates the amount of soil loss from the ratio of the 137Csmeasured at a sampling point and that measured at a localreference inventory; the proportion of the original 137Cs (repre-sented by the reference inventory) indicating what has been lost(Walling and He, 1999).

It is, however, necessary to assume that little or no erosion hasoccurred under the original forest cover. This is a reasonableassumption for the BLC area as it was covered by dense rainforestprior to deforestation and development. Activities associated withforest clearing furthermore, can be assumed to have mixed theexisting 137Cs into the disturbance layer or tillage depth reasonablywell. The equation for this model can be written as follows(Walling et al., 1999):

Y ¼ 10BdX

100TP(1)

where Y = mean annual soil loss (t ha�1 y�1); d = depth of theplough or cultivation layer (m); B = bulk density of soil (kg m�3);X = percentage reduction in total 137Cs inventory (defined as(Aref � A)/Aref � 100); T = Time elapsed since the initiation of 137Csaccumulation or commencement of cultivation, whichever is later(y); Aref = local 137Cs reference inventory (Bq m�2); A = measuredtotal 137Cs inventory at the sampling point (Bq m�2); P = particlesize correction factor for erosion.

According to Turner and Gillbanks (2003), the mean tillage ordisturbance depth for cultivated oil palm and rubber estates is0.25–0.3 m. A tillage depth of 0.25 m has thus been assumed forthe soil redistribution estimation. A particle size correction factorfor erosion of P = 1 was used in the proportional model in thisstudy. A minor difference, however, is found between the grain size(D50) of the original soils (0–2 cm) and the mobilized sedimentswhen they are compared in order to validate the P value. Details ofthe other parameters required for running the proportional modelare shown in Table 1.

2.8. Soil redistribution mapping

The soil redistribution mapping technique based on 137Cs wasapplied by Mabit and Bernard (2007), Mabit et al. (2008b), usinggeostatistics together with a geographic information system (GIS).This method is applicable to small catchments with similar landuse and topographic conditions. In the present research, soilredistribution mapping was carried out based on land use anddates of tillage commencement as well as similarities in eachsubcatchment. FELDA land development districts with definitedates of tillage commencement and elapsed time were the basicunits for mapping. Soil erosion values determined for cleared landwith similar elapsed times were extended to other areas of clearedland within the same subcatchment. Mean values of soil loss inother areas of undisturbed Malaysian rain forest were obtainedfrom previous studies and extended to natural forest in the BeraLake catchment. Mean accretion rates for sink areas in BLC werebased on ten bulk core samples in the wetlands and open waters.

3. Results and discussion

3.1. 137Cs inventory in soil samples

Atomic bomb-derived nuclides are difficult to detect in the soilprofiles of equatorial areas. Previous studies in Malaysia (Neer-gaard et al., 2008; Othman et al., 2003), Indonesia (Barokah et al.,2007; Suhartini, 2006), Vietnam (Hien et al., 2002; Hai et al., 2008),the Philippines and Sri Lanka IAEA (2003), and Taiwan (Chiu et al.,1999) that have highlighted the applicability of 137Cs in measuringrates of soil redistribution in tropical areas have also pointed outthe low activity of 137Cs (<400 Bq m�2), similar to that in tropical

Table 1137Cs inventory, grain size distribution, and classification.

Sample ID Land use Bulk density kg m�3 Cs-137 Bq m�2 Clay % Silt % Sand % Classification

1 OilPalm 1405 103.7 � 14 3.6 30.7 65.7 Sandy loam

2 OilPalm 1472 79.4 � 11 7.2 34.9 57.9 Sandy loam

3 OilPalm 1275 70 � 9 7.3 48.3 44.4 Loam

4 OilPalm 1137 97.5 � 9 10.5 54.1 35.4 Silt loam

5 OilPalm 1130 45 � 6 4.8 24.2 71.0 Sandy loam


7 OilPalm 1178 68 � 7 3.1 20.0 76.8 Loamy sand


9 OilPalm 1230 79.5 � 11 3.5 26.1 70.5 Loamy sand

10 OilPalm 1200 2.2 � 0.1 5.1 28.5 66.4 Loamy sand

11 OilPalm 1573 36 � 6 7.4 60.1 32.6 Silt loam

12 OilPalm 935 246 � 24a 6.8 39.5 53.7 Sandy loam

13 Rubber farm 1258 168 � 18a 6.7 51.8 41.5 Silt loam

14 OilPalm Developing 1623 31 � 6 18.2 59.0 22.8 Silt loam

15 OilPalm Developing 1231 59 � 11 8.4 11.0 80.6 Loamy sand

16 OilPalm Developing 1300 41 � 7 7.6 47.3 45.1 Loam




20 OilPalm Developing 1580 45 � 8 5.0 32.5 62.4 Sandy loam

21 OilPlam Developing 1478 52 � 7 7.4 53.3 39.3 Silt loam

22 Cleared Land 1791 21 � 2 11.0 40.9 48.1 Sandy loam

23 Cleared Land 1407 1.7 � 0.1 11.7 60.5 27.9 Silt loam


25 Cleared Land 1409 72 � 9 8.5 48.8 42.7 Loam


27 Reference 1290 85 � 7 4.5 35.8 59.7 Sandy loam

28 Reference 1359 96.4 � 11 6.4 45.9 47.7 Sandy loam


30 Reference 941 137 � 16 8.0 52.5 39.4 Silt loam






a Refers to samples that received Cs-137 excess due to deposition instead of erosion.


Australia (Hancock et al., 2000). The low activity of 137Cs inMalaysia was thus anticipated in this study and affected thesampling strategy.

Reported mean 137Cs reference inventories in Indonesia varybetween 261 � 37 and 286 � 47 Bq m�2 (Barokah et al., 2007;Suhartini, 2006) but between 450 � 280 and 170 � 160 Bq m�2 in thePhilippines (IAEA, 2003). In Vietnam, the 137Cs inventory at thereference sites has varied between 237 and 1097 Bq m�2 (Hien et al.,2002; Hai et al., 2008), while in Taiwan, it ranges between 154 and317 Bq m�2 in Taiwan (Chiu, 1999) and in tropical Australia, between129 and 209 Bq m�2 (Hancock et al., 2000).

Within the Bera Lake catchment, the 137Cs reference inventoryhas been calculated to have a mean value of 125.39 � 36 Bq m�2;the coefficient of variation (CV) being 0.29 and ranging from 85 to193 Bq m�2. The 137Cs reference inventory in the study area istherefore, in the range of the 137Cs inventory in tropical Australia andthe Philippines, but much lower than that in neighboring countries.Mabit et al. (2008b) has stated that the CV of reference samples inforested sites is large (0.19–0.47), but low in pasture and grasslandsites (0.051–0.41). As the CV of the reference samples in the studyarea is low, the results can be considered to be reliable information forassessment of the base level of 137Cs with moderate spatial variabilityin fallout inputs. Reference samples in the study area furthermore,have an average clay content of 7.3%, whilst the average silt and sandcontents are 46.4, and 46.3, %, respectively. When the 137Cs inventoryin all samples was compared with the soil particle sizes, there was amoderate correlation with the silt sized particles (r = 0.4; p < 0.05),but a weak correlation (r = 0.2; p < 0.05) with the sand sized particles.A strong positive correlation (r = 0.74; p < 0.05) was also foundbetween the 137Cs inventory and the fine grain size (clay fraction)of reference samples. The data thus highlights the important role of

parent rocks and rate of soil disturbance in the study area in terms of137Cs adsorption in the soil profile. Strong negative correlationsbetween the 137Cs inventory (r = �0.7; p < 0.05) and TOC (r = �0.92;p < 0.05) and depth were also found in the reference sample (Fig. 3).For the depth range of 0–4 cm, the forest soils mainly consist oforganic material with little inorganic compounds and thus show low137Cs activity.

The scattered plan of sampling as well as variations in slopegradient, parent rocks and rate of soil mixing during the planting ofoil palm and rubber has resulted in variation of 137Cs activity andparticle size distributions of samples (Table 1). It is to be noted thatsoils in the developed lands covered by oil palm and rubberplantations have a sandy loam texture, while soils in areas stillbeing developed or covered by young oil palm and rubberplantations have a loamy texture. Young oil palm plantationstherefore, appear to have a short duration of exposure and erosioncompared with developed lands.

3.2. Soil redistribution in Bera Lake catchment

3.2.1. Soil loss estimation

Individual analyzed samples of each FELDA district show clearlythe effects of the dates of start of deforestation on soil loss anderosion rates in the BLC (Table 2). The results also show thatdifferent land use in areas of similar topographic and parent rocksgive rise to different rates of soil loss. The results show the meanpercentage soil loss for developed oil or rubber plantations in thedifferent subcatchments is 55 � 22% with a CV of 0.41.

The mean value of erosion is therefore, 70 � 35 t h�1 y�1 with aCV of 0.5. As the tillage depth is 250 kg m�2 (ca. 25 cm), the resultsindicate that 137.5 kg m�2 (or ca. 10.32 cm) has been lost by erosion

Fig. 3. Variation of 137Cs inventory with depth at the reference site.


since the start of land clearing and deforestation. The mean erosionrate during the first, second, third, and fourth FELDA land develop-ment projects based on their tillage commencement dates is thus0.58 � 0.15, 0.47 � 0.17, 0.71 � 0.41, and 1.13 � 0.13 cm y�1, respec-tively. The maximum amount of soil redistribution of 119 t h�1 y�1

was obtained in the north-east of catchment Bera-Selatan (4) oil palmdistrict where the bedrock comprises red colored, continental faciesrocks, mainly areno-argillaceous strata with rudaceous and carbona-

Table 2Soil loss percentage, erosion magnitude, and erosion rate.

Sample ID Subcatchment Land use Soil lost %

1.00 1.00 OilPalm 27.70

2.00 2.00 OilPalm 44.70

3.00 3.00 OilPalm 27.50

4.00 4.00 OilPalm 29.20

5.00 4.00 OilPalm 67.30

6.00 8.00 OilPalm 56.30

7.00 10.00 OilPalm 64.90

8.00 11.00 OilPalm 49.50

9.00 12.00 OilPalm 58.70

10.00 12.00 OilPalm 97.80

11.00 12.00 OilPalm 81.09

12.00 12.00 OilPalm 27.8a

13.00 9.00 Rubber farm 14.5a

14.00 4.00 OilPalm Developing 71.48







21.00 9.00 OilPlam Developing 63.82

22.00 8.00 Cleared Land 84.85

23.00 1.00 Cleared Land 98.79

24.00 6.00 Cleared Land 56.05

25.00 8.00 Cleared Land 47.40

26.00 7.00 Cleared Land 82.90

a Remark of soil accumulation and deposition rate.

ceous bands. As a result, the maximum erosion rate of 1.56 cm y�1 isfound here (Fig. 4). On the other hand, the lowest soil loss, erosionmagnitude and medium-term erosion rate was determined at 27.7%,30.42 t h�1 y�1, and 0.35 cm y�1, respectively, in the Triang-Selatan(1) oil palm district which was developed in 1979 in the north west ofthe catchment.

A literature review shows that most previous studies inneighboring countries have applied the 137Cs technique in differentland use schemes or using the conversion models in contrast to thepresent study at BLC. The Proportional model, used in Seri Lankaand the Philippines (IAEA, 2003) to estimate soil redistribution in arainforest area converted to monoculture (tea and coffee farms)yielded an erosion rate of 43, and 33 t h�1 y�1, respectively. Thesevalues were calculated from rather small farms with non-machinery deforestation and different dates of tillage commence-ment. These values are comparable with those of least magnitudeof erosion in the developed lands of the Bera Lake catchment,although the overall situation is quite different.

Soil erosion rates in planted oil palm/rubber estates in previousstudies (Leigh and Low, 1973; Malmer, 1990; Shallow, 1956;Douglas et al., 1992; Paramananthan and Eswaran, 1984) havebeen reported at 56 � 20 t h�1 y�1. This value, which has beencalculated using the Universal Soil Loss Equation (USLE), appears tounder-estimate soil erosion when compared with the results of theProportional model and 137Cs fallout radionuclide inventory. It is to benoted that although different assumptions and parameters areapplied in the 137Cs inventory technique and the USLE method; theoil palm plantations have been prepared using similar procedures inall parts of Malaysia. Further work, therefore, is needed to calibratethe results of the empirical USLE method with those of the 137Cstechnique to estimate soil erosion in the Bera Lake catchment.

Another form of land use which is shown in Fig. 5 is developingoil palm/rubber plantations. This land use has influenced soilredistribution in the BLC involving areas partly covered by veryyoung planted trees and areas of re-planted oil palm and rubbertrees. Field observations and a report by Henson (1994) indicatesthat these areas of developing oil palm/rubber tree plantationswith partially exposed land surfaces were mainly cleared by local

Erosion t ha�1 y�1 Elapsed time (y) Erosion rate cm y�1

�30.43 32.00 0.35

�54.79 30.00 0.60

�33.69 26.00 0.42

�29.61 28.00 0.42

�103.79 27.00 1.00

�72.01 39.00 0.58

�48.91 25.00 1.04

�72.99 25.00 0.79

�75.33 25.00 0.94

�118.63 25.00 1.56

�128.21 25.00 1.30

30.5a 25a 0.44a

40.00 16a 0.29a

�120.80 16.00 1.79

�114.84 16.00 1.43

�142.20 16.00 1.75

�46.54 16.00 1.14

�129.60 16.00 1.40

�156.43 16.00 1.71

�84.20 16.00 1.72

�143.79 16.00 1.60

�1266.44 4.00 8.49

�1158.26 4.00 9.88

�532.46 4.00 5.60

�556.58 4.00 4.74

�1061.12 4.00 8.29

Fig. 4. Soil erosion rate map of Bera Lake catchment.

Fig. 5. Land use features in the study area and their soil loss magnitudes.



residents after nomination of the Bera Lake catchment as aRAMSAR site and after prohibition of FELDA development projectsin 1994. Tillage commencement dates of these areas of developingplantations are thus assumed to be 1995 with a total elapsedperiod of 16 years. The results clearly confirm the erosionmagnitude of developing lands with a mean soil erosion rate of117 � 31 t h�1 y�1 and a CV of 0.3. The mean soil loss percentage inthese developing areas was calculated to be 63 � 9 with a CV of 0.14.This indicates that values of soil loss in the developing lands havebeen similar for the past two decades with the lowest variance.According to the tillage depth (250 kg m�2) and tillage commence-ment date, soil loss and the mean medium-term soil erosion rate inthese developing lands is 156.5 kg m�2 (or ca. 11.32 cm) and1.57 � 0.24 cm y�1, respectively. The maximum rate of erosiondetermined for developing lands is 1.79 cm y�1 in the RAMSAR sitewhere there has been encroachment by local residents.

Field observations show that most of the recent land beingdeveloped in the Bera Lake catchment is being cultivated withrubber trees. Rubber trees are preferred to oil-palm by the localresidents in view of easier land preparation, maintenance, andharvesting (Henson, 1994). The erosion magnitude in BLC iscomparable with that at the Seberang Perai Selatan area in Penang,Malaysia, where the highest contribution of soil loss amongcultivated lands was recorded for rubber plantations at122 t h�1 y�1. This value is much higher than that of oil palmplantations with a soil loss of 34 t h�1 y�1 (Shamshad et al., 2008).

Serious erosion is found in the cleared areas in the Bera Lakecatchment. Recent encroachments into the RAMSAR site by localresidents have been detected at 187 locations where the groundsurface has been completely cleared and exposed to weatheringprocess. It can therefore, be assumed that tillage of cleared landsstarted in 2008 as normal land clearing and preparation takes some12–14 months for a 2000 ha land development project (Tan et al.,2009). Such a situation, has led to a mean soil loss percentage of74 � 21 with a CV of 0.29 from cleared lands. Maximum, minimum,and mean soil loss magnitudes of 1266, 532, and 915 � 345 t h�1 y�1

respectively, with CV of 0.4 were calculated for newly open land. As aresult, the medium-term mean erosion rate is currently7.4 � 2.1 cm y�1 with a CV of 0.29 in cleared lands at the Bera Lakecatchment. Field observations clearly show that exposed landsurfaces experience serious soil erosion during individual tropicalrainstorms in the study area. The maximum rate of erosionfurthermore, occurs in cleared land in subcatchment 1 at the northof the BLC with a value of 9.88 cm y�1 (Fig. 4). The results show thatthe erosion rate in cleared lands in the RAMSAR site is about half thatwas calculated for areas that were previously covered by oil palm andrecently cleared for replanting of oil palm/rubber. Field observationsalso show that there is a relatively short ‘vegetation cover’ recoveryperiod in the study area with exposed land being covered by covercrops and shrubs within 2–3 years. The soil erosion rate thusdecreases with time. Soil loss in cleared land at two small catchmentsat Sipitang (Midmore et al., 1996), and at Ulu Segama (Malmer, 1990),

Table 3137Cs inventory and accumulation rate in samples from t.

Sample ID Layer thickness m Porosity % Weight kg Submerged bulk d

1 0.22 81.0 0.06 445

2 0.19 79.3 0.09 171

3 0.23 79.7 0.09 148

4 0.16 89.8 0.06 148

5 0.21 79.1 0.09 143

6 0.20 79.4 0.09 169

7 0.15 74.0 0.06 134

8 0.20 80.0 0.09 167

9 0.25 86.0 0.10 248

10 0.16 70.0 0.09 169

in Sabah calculated with the USLE equation was 6.60, and16 t ha�1 y�1, respectively. In these cases, the calculated soil erosionmagnitude is under-estimated in comparison with the 137Cstechnique. It is, however, evident that the size of catchment areaalso plays an important role in determination of soil loss by anytechnique. Walling (1982) for instance, estimated soil erosion in theCikeruh and Cigulung catchments in tropical Java with areas of 250,and 43 km2 area, at 112, and 10.85 t ha�1 y�1, respectively. Sitepreparation by burning as one of the land development phases hasalso caused a significant increase in soil erosion in the Bera Lakecatchment (Henson, 1994). The importance of forest burning in termsof increased rates of soil loss has also been reported by Field andCarter (2000). Further studies are need to evaluate the role of forestburning in the catchment, though evidence of forest burning in landpreparation for planting is clearly manifested in the Bera Lakesediment column in a charcoal horizon, especially at the lowercontact of white sandy mud deposits. Soil loss in cleared land at twosmall catchments at Sipitang (Midmore et al., 1996), and at UluSegama (Malmer, 1990), in Sabah calculated with the USLE equationwas 6.60, and 16 t ha�1 y�1, respectively. In these cases, thecalculated soil erosion magnitude is under-estimated in comparisonwith the 137Cs technique. It is, however, evident that the size ofcatchment area also plays an important role in determination of soilloss by any technique. For instance, Walling (1982), estimated soilerosion in the Cikeruh and Cigulung catchments in tropical Javawith areas of 250, and 43 km2 area, at 112, and 10.85 t ha�1 y�1,respectively.

Models calibrated for cultivated lands have usually assumedvery low soil loss from natural forest (Walling, 1999). Ling et al.(1979), Wiersum (1985), Malmer (1990), and Shamshad et al.(2008) have estimated soil loss from Malaysian natural rainforestto be 10, 6.2, 5.1, and 0 t ha�1 y�1, respectively; these values beingdetermined with the USLE equation. Although it can be assumedthat soil erosion in the natural rainforest at the Bera Lakecatchment is very low, field observations show that recentencroachments into the forest area for timber and other naturalproducts have led to erosion features in the form of gullies andlandslips. A mean soil erosion value of 7 t ha�1 y�1 from the justmentioned studies has thus been used to illustrate soil loss fromthe original forest at Bera Lake catchment.

3.2.2. Soil accumulation rate in wetland and open water

Wetlands and open waters covering some 57 km�2 in area arerecognized as natural soil traps and retention pounds within theBera Lake catchment. Large amounts of eroded soil haveaccumulated in the wetlands and open waters which show manydepositional features as in other sink areas, including sedimentdumping, the narrowing of water bodies by sand barriers, andserious depth reduction. Sediment samples in the wetlands andopen waters were analyzed for their 137Cs inventory to a depth of25 cm, similar to that of the soil samples analyzed for their 137Csinventory (Table 3). The samples in the wetlands and open waters

ensity kg m�3 Inventory Bq m�2 Accretion % Accretion rate t ha�1 y�1

367.7 61.0 21.3

1139.1 87.4 17.8

1097.7 86.9 16.4

361.5 60.3 5.7

1389.4 89.7 10.0

1153.4 87.6 22.8

367.4 60.9 11.1

1274.8 88.7 24.7

4386.8 96.7 33.2

2360.9 93.9 36.3


consist of dark organic-rich soils which are characterized by verylow submerged bulk densities (mean of 194 � 93 kg m�3), highporosities (mean of 87 � 7%) and very low inorganic contents ormatrix.

The reference sample for the wetlands and open waters (Fig. 1)indicates 137Cs activity of 143.5 Bq m�2 for the same bulk corediameter, though the mean 137Cs inventory in the submerged soilsamples was determined to be 1390 � 1216 Bq m�2 with a CV of0.87. The dendritic pattern of the wetlands and open waters withinthe Bera Lake area also appears to significantly control 137Csenrichment in the sediments with samples from the semi-closedareas at the north of Bera Lake having the highest inventory that wasup to 4 times the value in open water samples. The accretionmagnitude and rate also appears to be morphologically controlledwith a mean accretion rate of 20 � 9 t ha�1 y�1 with a CV of 0.49having been determined for the wetlands and open waters.Implementation of the five Federal Land Development Authority(FELDA) projects, especially that of the fifth one between 1990 and1995 (Henson, 1994), has also resulted in the oil palm/rubber estatesbecoming now established as mature forests. Land developmentprojects within the Bera Lake catchment were prohibited in 1995after designation of the Permanent Forest States (PFS) as the firstRAMSAR site in Peninsular Malaysia and nomination of the cultivatedlands as the Buffer Zone (Dorall and Sinniah, 1997). A Report of theMalaysian Palm Oil Council (MPOC, 2007) furthermore, states that theannual biomass productivity in an occupied area of rainforest ormature oil palm/rubber plantations is 1.5 million tones. This valuecould potentially cover the whole of the Bera Lake catchment with0.4 cm of organic-matter. The run-off loads and accumulated soils inthe sink areas are therefore, organic-rich due to the abundant biomassproduction. In view of this, the elapsed time for accumulation oforganic-rich sediments in the study area is assumed to be 16 yearsafter development of mature oil palm/rubber plantations. The meansoil accumulation rate in the wetlands and open waters wasdetermined to be 1.025 cm y�1 (Fig. 4).

4. Conclusion

This study has shown that although the Bera Lake catchment islocated in a tropical environment and far from 137Cs sources, thereis still present 137Cs fallout radionuclide (FRN). This has beenshown by samples at reference sites in the catchment where the137Cs inventories exhibited a strong positive affinity (r = 0.74;p < 0.05) with fine grained particles and also showed the idealdecrease of 137Cs inventory with depth. The proportional modelusing the 137Cs radionuclide was found to be a suitable model forevaluating soil redistribution in the Bera Lake catchment wheredeforestation was followed by a single cycle of medium-termlength of cultivation of 30–40 years. Land use changes by theFederal Land Development Authority since 1971 have played animportant role in influencing rates of soil erosion and depositionwithin the catchment. Maturing oil palm plantations with knownelapsed times from the start of clearing of the original rain forest,and calculated rates of erosion provided an opportunity to preparea soil redistribution map of the Bera Lake catchment. The meanrate of soil erosion in cleared lands, maturing oil palm and rubberplantations, and mature oil palm and rubber plantations wereestimated at 915 � 345, 117 � 36, and 70 � 39 t h�1 y�1, respective-ly. The eroded soils have accumulated in wetlands and open waterswithin the catchment at a rate of 1.025 cm y�1 since 1995. This studyrecommends the use of the proportional model to estimate soilredistribution in other areas of the world where the land has beendeforested and then cultivated once over a medium-term period of 30years. This study represents the first soil erosion and sedimentationmapping project in Malaysia that applies the 137Cs technique on thecatchment scale.

Acknowledgments

The senior author gratefully acknowledges Dr. D. Walling for hisadvice on choice of a suitable model for estimation of soil erosion.The senior author also gratefully acknowledges Dr. K.H. Lee and Dr.L. Mabit from IAEA for providing the soil erosion conversionmodels. The Institute of Research Management and Monitoring(IPPP), University Malaya funded this research project. The BeraLake Ramsar Site Management Unit (DWNP) and Mr. Ahmad FaridAbu Bakar are thanked for their assistance in field work, while theassistance for the technicians at the Gama-Spectrometer Labora-tory (Mr. Yii, M.W. and Mr. Ishak Kamarozaman) is gratefullyacknowledged.

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