Agroforestry for soil and water conservation in the westernHimalayan Valley Region of India

2. Crop and tree production

PRATAP NARAIN, R. K. SINGH, N. S. SINDHWAL and P. JOSHIECentral Soil and Water Conservation Research and Training Institute, 218, Kaulagarh Road,Dehradun – 248 195, India; E-mail: cswcrti@icar.delhi.nic.in

Key words: alley cropping, biomass production, contour tree rows, leucaena hedgerows, landequivalent ratio

Abstract. A ten-year-study (1983 to 1992) conducted on nine 15

× 90 m runoff plots at 4%slope compared production efficiency of Leucaena leucocephala and Eucalyptus hybrid basedagroforestry as well as monocropping landuse systems in the warm, subhumid climate of thewestern Himalayan region of India. Treatments for the first sequence were: monocroppingsystems of leucaena, eucalyptus, Chrysopogon fulvus grass and maize – wheat rotation, and alleycropping systems of grass and crops at 4.5 and 10.5 m alley widths with paired contour treerows of leucaena and eucalyptus. In the second sequence, alley width increased to 22.5 m in1989, grass was replaced by turmeric Curcuma longa and paired contour rows of leucaena hedgeswere introduced in monocropping systems of grain crops and turmeric. Integration of leucaenaand eucalyptus trees with crops caused severe reduction of crop yields ranging from 21 to 92%for wheat grain, 59 to 69% for maize grain, 60 to 67% for dry grass and about 50% for turmericrhizome depending upon the age of trees and alley width. The grain yield of crops stabilized atabout 50% reduction with 22.5 m alley width. Total crop biomass (grain + straw) also revealeda similar trend; however, its magnitude of reduction was less severe than for grain. Productionof biomass was much lower near the tree rows than in mid alleys. Managing leucaena as contourhedgerows eliminated crop yield reduction in alleys. Performance of grass and turmeric in alleyswas not found to be satisfactory. Biomass produced from trees adequately compensated thecrop yield reduction. Land equivalent ratios of agroforestry landuses were comparable or evenbetter than monocropping systems indicating suitability of these systems for the westernHimalayan valley region.

Introduction

Agroforestry has shown encouraging results in the Himalayan foothills andvalley regions for enhancing productivity and arresting the process of landdegradation. It might offer affordable alternatives to poor farmers in place ofexpensive conventional conservation measures (Mittal and Singh, 1989;Khybri et al., 1992 and Grewal et al., 1994). Conservation is the primaryobjective in fragile ecosystems of the western Himalayas, but it may not beadoptable unless reasonable production is also ensured.

Traditional agroforestry practices involve the use of trees in various spatialpatterns to meet the wood, fuel and fodder requirements of the farmers. Borderrow tree planting is a common practice in India, while alley farming with trees

Agroforestry Systems 39: 191–203, 1998. 1998 Kluwer Academic Publishers. Printed in the Netherlands.

or hedgerows have yet to make inroads at a farm level. A major area of agro-forestry research in previous years has been on hedgerow intercropping. Inspite of experimental evidence of the soil conservation value of hedgerowintercropping, its adoption by farmers has not been encouraging, mainly dueto extra labour requirement, nonavailability of commercial wood, limitedchoice of tree species and unattractive long-term benefits in lieu of short-termrisks of crop-yield reduction (David, 1995). Jama et al. (1995) recommendgrowing sole blocks of Leucaena leucocephala and crops instead of alleycropping in semiarid high lands of Kenya, where competition for water ismore severe compared to subhumid regions.

This study compares maize-wheat rotation, a traditional landuse, popularin the foothills and valley region of the western Himalayas in India, withChrysopogon fulvus, a climax fodder grass, turmeric, a shade tolerant crop,and block plantation of leucaena and eucalyptus trees for their productionand conservation efficiency. Agroforestry combinations of crops, grass andturmeric with Leucaena leucocephala and Eucalyptus hybrid grown as contourbarrier rows of trees or hedgerows are also compared. The warm subhumidclimate of the region favours growth of these tree spp. While leucaena fulfillsthe fuel and fodder needs of the farmers, eucalyptus enjoys the farmer’s accep-tance for its commercial value. The conservation perspective of these landuseshas been addressed by Narain et al. (submitted).

Material and methods

The study was conducted during 1983 to 1992 on fine silty hyperthermic, udicHaplustalf under the subhumid, subtropical climate of the Himalayan foothillsof north-west India. The region receives bimodal rainfall distribution with twodistinct cropping seasons. During maize cultivation in the rainy season fromJune to September, the profile remains saturated. Wheat is grown fromDecember to April on residual moisture. The moisture is the major limitingfactor during the wheat season as only 200 mm winter rains are receivedduring this period.

Agroforestry landuses were compared on large-size-erosion-plot (90 ×15 m) at 4% slope equipped with guaging facilities. Description of site, exper-imental setting and landuse treatments are given in Narain et al. (submitted).Nine landuses compared in this study were: monocropping systems ofmaize-wheat rotation, Chrysopogon fulvus grass, Leucaena leucocephala andEucalyptus hybrid block plantations; alley cropping systems comprisingmaize-wheat rotation or grass with paired rows of eucalyptus or leucaenaspecies, and a clean weeded up-and-down-tilled cultivated fallow. In theseventh year (sequence II) grass was replaced by turmeric (Curcuma longa)and paired contour hedgerows of leucaena were introduced with crops. Withadvancing tree age, alley width was increased from 4.5 m to 10.5 m in thefourth year and to 22.5 m in the seventh year of the study.

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Tree and crop management

Four-month-old, nursery-raised seedlings of Eucalyptus hybrid and Leucaenaleucocephala (CV K-8) were planted in 30 × 30 × 45 cm pits filled with2 kg farm-yard manure + 16 g P and 50 g BHC per pit. Leucaena pits werealso applied with 60 g CaO per pit. Trees were planted in contour pairedrows (1.5 × 1.5 m) having north-south orientation. Maize composite (Var.Vijay) was sown in June with a basal dose of 60:60:40 kg ha–1, N:P:K and60 kg N ha–1 was top dressed in two equal splits. Weeds were controlled withpre-emergence application of atrazine and two hand weedings. Maize washarvested in September. Wheat (Var. HD 1981) was sown in November witha basal dose of 40:60:60 kg ha–1, N:P:K. The wheat was top dressed with20 kg ha–1 N. Turmeric was fertilised similar to maize. Grass and trees werenot fertilised.

Measurements and evaluation

Crop yield quadrates were harvested from upper, middle and lower parts ofeach plot. For maize, 3 × 4.5 m quadrates were harvested row-wise acrossthe alley width and grain and stover were separated. Wheat quadrates were15 × 1 m near the tree row, and 15 × 2 m thereafter. Yield data are presentedfrom the second year onwards after establishment of trees and grasses.

Alternate pairs of tree-rows were removed every third year. Above-groundbiomass was estimated from 20% sampled trees representing different diameterclasses. Fresh and oven-dry (80 °C) weight of wood was recorded for threediameter classes viz. pole wood (>5 cm), branch wood (2.5 to 5.0 cm), brushwood (<2.5 cm) and green foliage was weighed separately.

Up to 1985 (alley width 4.5 m), gravimetric measurements of soil watercontent were taken down to 120 cm depth in the middle of tree and crop strips.After 1986 (alley width 10.5 m), soil water content was measured withTroxler’s neutron moisture gauge down to a depth of 300 cm in the middleof tree strips and to 150 cm depth in cropped area at a distance of 1.25 m,3.25 m and 5.25 m in 10.5 m alleys (1986–1988), and 1.25 m, 5.25 m and11.25 m in 22.5 m alleys (1989–1992) from both sides of the tree-rows.Moisture measurements in the maize season were done at the sowing andtasseling stages (50 days after sowing). Because the profile remains nearlysaturated during the rainy season of maize, soil water measurements werediscontinued after two years. During the wheat season, soil water wasmeasured at the sowing and flowering stage (90 days after sowing) throughoutthe study.

Marketable produce under different landuse systems, were converted towheat grain equivalent considering the prevailing market rates in the year1995–1996. The production efficiency of different landuse systems wasassessed by calculating land equivalent ratios (LER) (Willey, 1979).

There were no independent replications of the landuses imposed on large-

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size and homogenous erosion-plots. Each plot was sampled from three loca-tions (upper, middle and lower) which were considered as three replicatesfor statistical analysis. For testing the effect of distance from tree-rows andage of the trees on crop yield at tree-crop interface, grain yield data for nineyears were analysed using stepwise regression analysis with stratgraphicssoftware. Final models with highest adjusted R2 and minimum standard errorwere selected.

Results

Effect of trees on wheat production

Crop yields were significantly reduced by the presence of trees. Although nosignificance difference was observed between the two tree species, however,slightly lower yields were obtained with eucalyptus. A tree density of 2222plants per hectare with 4.5 m alley width reduced the wheat grain yield by25% in the second year and up to 70% in the third year (Table 1). Removalof alternate pair rows in 1985 increased alley width to 10.5 m and improvedwheat yield to a level of 21% reduction. The yield reduction again increasedto 78% in the 5th year and 92% in the 6th year. Further removal of alternatepaired rows in 1988 widened the alley width to 22.5 m and maintained grainyield of wheat at about 50% level of the sole cropping control during the

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Table 1. Effect of trees on wheat yields in Dehra Dun, India.

Sequence Year Wheat grain (kg ha–1) Wheat biomass (kg ha–1)

Controla Crop + Crop + Control Crop + Crop +leucaena eucalyptus leucaena eucalyptus

I 02 2098 1724 1416 5308 4389 368003 1487 0382 0242 4301 1209 115704b 1277 1123 0883 4023 3184 266205 2139 0538 0413 7889 1942 151506 0356 0036 0020 2611 0367 0247

LSD(0.05) Year × treatment 0331 0902

II 07b 2083 1072 1001 5633 2882 267408 1383 0757 0512 3334 1790 116009 0477 0346 0238 1303 1008 070410 1924 1169 0754 4854 2963 1951

LSD(0.05) Year × treatment 0213 0575

a Hedgerows were introduced in the 7th year.b Alternate paired rows were removed in the 4th and 7th years.

remaining four years of study. The total crop biomass (grain + straw) revealeda similar trend; however, the magnitude of reduction in biomass yield wasless severe than in grain yield (Table 1). The treatment and year interactionwas significant in wheat showing that treatment effect differed from year toyear.

The biomass yield of crops (Figure 1) was drastically reduced in the vicinityof trees. Wheat biomass production progressively declined towards tree-rowscompared to mid-alleys (Figures 2 and 3). This yield depression near the treesincreased with the age of trees. The moisture distribution across the alleys atsowing and 90 days after sowing of wheat also followed a similar pattern.Wheat biomass yield and soil water content were more or less uniformly dis-tributed across the leucaena hedge alleys (Figure 3). When the wheat grainyield (Gw in kg ha–1) was regressed with distance from tree rows (D in metres)and age of trees (Y in years), the following relationships were obtained:

Leucaena alleys: Gw = 284.19 D + 52.06 Y – 25.94 D*Y(Adj. R2 = 0.8, fitted values 156)

Eucalyptus alleys: Gw = 336.8 D + 4.63 Y2 – 34.53 D*Y(Adj. R2 = 0.64, fitted values 156)

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Figure 1. Soil water content and crop biomass (grain + straw) in alleys after three years oftree growth at Dehra Dun, India. W0 and W50 = Soil water at crop sowing and 50 days after;TCI = Tree-crop interface upto 1 m from tree-row; Alley biomass = crop yield beyond 1 mfrom tree-row.

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Figure 2. Distribution pattern of wheat and chrysopogon biomass (± SE) and soil waterat sowing and 50 days after sowing (DAS) in 10.5 m wide alleys (sequence 1) at Dehra Dun,India.

Figure 3. Distribution pattern of crop biomass and soil water at crop sowing and 90 days aftersowing (DAS) in 22.5 m wide alleys (sequence 2, averaged for three years) at Dehra Dun,India.

Effect of trees on maize production

The effect of trees on maize yields over the years had a pattern similar towheat yields. In the case of maize, treatment × year interaction was notsignificant showing consistency of treatment effect. The average reductionsin grain yield of maize in the alleys as compared to control were 59% and69% in the first and second sequences (Table 2). Biomass yield reductionof maize in the alleys was about 50% compared to control. In spite of thehigher soil water content, maize biomass yields were lower near the tree rows(Figure 1).

Effect of trees on grass and turmeric production

During the initial two years of the establishment period, Chrysopogon fulvusgrass yields were very low (Table 3). Grass production was less than 2 Mgha–1 dry grass in the control plot, which consistently improved up to the 6thyear. Similar to crops, grass yields were also severely reduced in the treealleys. Oven-dry weight of grass was only 9% in alleys compared to controlin the second year. Grass production improved to about 40% of control in

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Table 2. Effect of trees on maize yields in Dehra Dun, India.

Sequence Treatment Maize grain Maize biomass(kg ha–1) (kg ha–1)

I Control 1686 6104Crop + leucaena 0630 2657Crop + eucalyptus 0759 3219LSD(0.05) 0255 0830

Year 2 2542 8295Year 3 0516 1624Year 4 1162 5391Year 5 0386 2256Year 6 0521 2401LSD(0.05) 0329 1074

II Controla 1460 5980Crop + leucaena 0511 3005Crop + eucalyptus 0390 2908LSD(0.05) 0210 0774

Year 7 0499 4029Year 8 0969 4149Year 9 0611 4030Yea10 1069 3650LSD(0.05) 0242 N.S.

a Hedgerows were introduced in the 7th year.

the 3rd, 4th and 5th years but again declined to 33% in the 6th year. Althoughdifferences were not significant between the species during the two years ofthe establishment phase, they became significant thereafter and increased con-sistently with time. Eucalyptus alleys produced 15, 28 and 32% higher grassbiomass in the 4th, 5th and 6th years compared to leucaena alleys. After grassestablishment, the leucaena + grass system produced about 2 Mg ha–1 drygrass, whereas eucalyptus + grass produced up to 3 Mg ha–1 against about 6Mg ha–1 in the control without trees.

The distribution of profile moisture and grass yield in the alleys (Figure2) show only a marginal decline near the trees compared to mid-alleys. Overa period of 3 years, grass yield was relatively more stable across the alleysthan wheat yield.

Grass was replaced by a shade tolerant turmeric in 1989 which was har-vested biannually. The dry turmeric rhizome yield in tree alleys were signif-icantly reduced to about 50% as compared to hedge alleys (Table 3) in the1990 harvest. The differences between the tree species were, however, notsignificant. The yield reduction in tree alleys ranged from 21–25% in the 1992harvest as turmeric rhizome yields were very low due to mosaic attack.

A decline of rhizome yield and soil water content was observed towardstree rows compared to mid alleys (Figure 3). This pattern was not found withleucaena hedgerows.

Tree biomass production

Both the tree species were at par with respect to biomass production. Treebiomass harvested in sole plantation was about twice that of alley farmingsystems, while the number of trees harvested in sole plot were four timesthat of alley plots (Table 4). Biomass production per tree was highest in asso-ciation with crops, which was about 50% higher than tree + grass systems and

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Table 3. Effect of trees on yield of dry grass and turmeric rhizomes in Dehra Dun, India.

Sequence I Year Sequence II Year

1985 1986 1987 1988 1989 1990 1992

Grass Turmeric +(control) 1198 1866 5644 5889 6667 leucaena hedges 1404 627

Grass + Turmeric +leucaena 0105 0752 2097 2389 1877 leucaena 0634 500

Grass + Turmeric +eucalyptus 0115 0811 2417 3072 2481 eucalyptus 0774 472

LSD(0.05) Year × treatment 0085 114

Units are kg ha–1.

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Tab

le 4

. T

ree

biom

ass

unde

r al

ley

farm

ing

syst

ems

in D

ehra

Dun

, In

dia.

Tre

atm

ent

1985

1988

1992

Tot

alA

nnua

lM

g ha

–1M

g ha

–1

Mg

ha–1

kg t

ree–1

Mg

ha–1

kg t

ree–1

Mg

ha–1

kg t

ree–1

Cro

p +

leu

caen

a13

.49

12.1

27.9

450

.307

1.05

012.

811

2.48

11.2

5G

rass

+ l

euca

ena

11.2

010

.221

.42

38.6

047.

4408

5.5

080.

1508

.02

Sol

e le

ucae

na00

–0–

52.4

823

.612

2.61

055.

217

5.09

17.5

9C

rop

+ e

ucal

yptu

s14

.98

13.5

27.7

950

.106

8.75

123.

911

1.52

11.1

5G

rass

+ e

ucal

yptu

s13

.26

11.9

23.4

242

.203

9.30

070.

807

5.98

07.6

0S

ole

euca

lypt

us00

–0–

46.7

521

.011

9.98

025.

316

6.73

16.6

7L

SD

(0.0

5)01

.90

06.6

201

0.38

130% higher than sole plantations. Tree + grass systems produced signifi-cantly lower biomass than tree + crop landuses at the first thinning in 1985.In the year 1988, mixed landuses produced significantly lower tree biomassyield than sole plantations. However, differences within mixed landuses werenot significant. At the time of final harvest total tree biomass with grass com-binations were significantly lower than with crops, while sole plantationscontinue to produce highest biomass.

Land equivalent ratio

Wheat grain equivalent of tree + crop systems were at par or marginally higherthan sole cropping or sole tree landuses. LER values wee little higher than 1in mixed landuses in both the sequences (Table 5). Grass or turmeric, eithersole or with trees, showed much lower grain equivalent values and LER < 1.

Discussion

The crop yield reduction observed in this study is due to tree-crop competi-tion, which started from the second season onwards. The magnitude of yield

200

Table 5. Wheat grain equivalent and land equivalent ratios of different landuse systems in DehraDun, India.

Sequence I Sequence II

Landuse treatment Wheat grain LER Landuse Wheat grain LERequivalent treatment equivalentkg ha–1 yr–1 kg ha–1 yr–1

Chrysopogon grass 1124 – Turmeric + –leucaena hedges 2354

Maize-wheat 4336 – Maize-wheat +leucaena hedges 4079 –

Maize-wheat + Mean-wheat +leucaena 4546 1.13 leucaena 4777 1.14

Maize-wheat + Mean-wheat +eucalyptus 4435 1.18 eucalyptus 4477 0.99

Chrysopogon + Turmeric +leucaena 2464 0.89 leucaena 2973 0.89

Leucaena 3823 1.0 Leucaena 4175 1.0

Chrysopogon + Turmeric +eucalyptus 2723 1.10 eucalyptus 2984 0.88

Eucalyptus 3404 1.0 Eucalyptus 4742 1.0

reductions would generally depend on age, species and management of treesand climatic conditions. It has been found that 7 to 9-year-old unpruned trees,leucaena or eucalyptus, at an alley width of 22.5 m, continue to reduce cropyields by about 50%. In an earlier study at a similar site, Khybri et al. (1992)also reported a reduction in wheat yield by 41 to 61% in a unilateral openalley system with 100 tree ha–1 of unpruned 7–9 year-old Eucalyptus hybrid.In dry subhumid to semiarid climate, Ong et al. (1992) recorded 46 to 55%reduction in maize yield with upper storey of unpruned leucaena trees. A shiftin the management of trees to hedgerows consistently produced good yieldsof wheat and maize. These findings suggest that management of canopy playsa more effective role than modifying alley width in minimizing tree-crop com-petition. Uniform distribution of crop yields across hedge alley show that tree-crop competition can be considerably minimized in subhumid conditions,whereas in a semiarid climate, even hedgerow management has shown severecrop yield reductions (Rao et al., 1991 and Singh et al., 1989). A yield reduc-tion of 18 to 20% is reported on plots with hedgerows in a transitionalsubhumid and semiarid climate by the ICRAF research station at Machakos,Kenya (Ong et al., 1992). Unprecedented drought in the year 1987–1988resulted in poor crop yields. Poor wheat yields in the year 1990–1991 weredue to lodging of crop caused by untimely rains at crop maturity.

Competition for soil moisture at the tree-crop interface seems to be theprimary cause of wheat yield reduction. Higher wheat grain yield in leucaenaalleys compared to eucalyptus alleys, which was statistically significant insome years, may perhaps be due to the nutritional effect of fast decomposingleucaena litter.

Strong relationships with distance from tree-rows and age of trees wereobserved for wheat grain yield, which may be useful for estimating wheat pro-duction in alleys with leucaena and eucalyptus trees. Such relationships couldnot be established for maize production due to inconsistency in yield patternacross the alleys.

Maize being a C4 plant is more light-sensitive. Also, prolonged soil wetnesshas an adverse effect on maize production. In spite of soil water sufficiencyin monsoon season, maize suffered more severely than wheat possibly due toexcessive wetness near the trees and light stress due to luxuriant growth ofthe tree canopy. Higher soil moisture near the trees might be due to a fun-neling effect (stem flow) of the tree canopy.

In the tree + grass system, trees have delayed establishment of Chrysopogonfulvus grass by at least one year. Highest moisture and grass yield in mid-alleys as compared to near the tree-rows, suggest tree grass competition pri-marily for moisture. Lower grass yield in leucaena than eucalyptus alleyswas possibly due to the spreading type leucaena canopy casting more shadethan an upright eucalyptus canopy. However grass, being perennial vegeta-tion, was a better competitor with trees as compared to seasonal maize andwheat crops showing a sharp decline in crop yields prior to each thinning(Tables 1, 2 and 3). This is perhaps because of disadvantage with seasonal

201

crops as they need to establish root systems after each sowing, which is notthe case with grasses.

Although turmeric is considered to be a shade tolerant crop the magnitudeof rhizome yield reduction in alleys was about 50% which is similar toChrysopogon grass and grain crops. Previous studies (Gupta et al., 1982)recognising turmeric as shade tolerant crop, were conducted with deciduouspeach species. Turmeric seems to have limited scope with trees like leucaenaor eucalyptus having canopy cover all year round.

Both the tree species performed better with crops compared to grass. Thiscould be attributed to nutritional benefit derived by trees through fertilizerapplication to crops. Also, perennial chrysopogon grass seems to be morecompetitive than annual field crops. Although biomass per tree in the blockplantation was less than half that in the alley system, total tree biomass har-vested in the block planting system was double that of the alley systembecause of higher planting density. Annual increments of tree biomass wasin the following order: block plantation > tree + crop > tree + grass system.

In spite of a severe reduction in crop yields in tree-crop combinations, thewheat grain equivalent (LER) was at par with or even better than in solecropping. Thus tree biomass adequately compensated the loss due to crop yieldreduction. The production efficiency of the tree + crop system was alsorelatively better than the tree + grass or tree + turmeric systems. This is dueto better tree growth with crops than with grass or turmeric. However, if grainproduction is the priority, growing trees and crops as separate blocks may bea better preposition.

Conclusion

Under the subhumid climate of the western Himalayan region, where erosionis a major land degradative process, integration of trees with crops can effec-tively curtail erosional losses. However, tree + crop combinations in an alleyfarming system with unpruned trees substantially reduce crop yields. Thereduction in crop yields increased with increasing age of tree and decreasingalley width. Fuel and pole wood production from trees adequately compen-sated for crop yield reduction showing slightly better overall production effi-ciency of the alley farming system compared to sole cropping. When erosioncontrol is the primary objective, alley farming with leucaena hedgerows ortree-row barriers of leucaena or eucalyptus at 22.5 m alley width seems to bea viable alternative compared to traditional maize-wheat rotation. If grain pro-duction is the priority, crops and trees should be grown separately in blocksfor wood, fuel and fodder etc. To minimize erosional losses, these blocks couldbe arranged as alternate strips across the slope. Block plantation of trees orgrasses completely prevented runoff and soil loss and may be recommendedfor steeper slopes. Silvipastoral systems were conservation effective, butshowed low productivity.

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Acknowledgements

The authors express their deep sense of gratitude to Drs. V. V. DhruvaNarayana and J. S. Samra, Directors, CSWCRTI, Dehradun for their keeninterest throughout the study. Thanks are due to Dr. Pradeep Dogra, scientist,Shri O. P. Gupta and Shri Fateh Singh, technical assistants, for their kindsupport in manuscript preparation, laboratory analysis and field work, respec-tively. The painstaking efforts of Ms. Mamta Negi, stenographer, for typingthe manuscript are appreciated.

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