International Journal of Ecology and Environmental Sciences 38 (2-3): 73-85, 2012

© NATIONAL INSTITUTE OF ECOLOGY, NEW DELHI

Impact of Agroforestry Systems on Carbon Sequestration in NorthernHaryana, India

ASHA GAUR AND S.R. GUPTA*Department of Botany, Kurukshetra University, Kurukshetra 136119, India* Corresponding Author; E-mail: sgupta2002@yahoo.com

ABSTRACT

Agroforestry can be a good option for sequestering carbon in agricultural and marginal lands for climate change mitigation. The

aim of this study was to analyze the impact of Populus deltoides based agroforestry systems on carbon storage in the soil – plant

system in relation to site conditions. The agroforestry systems selected for the study were located at Kurukshetra (Salimpur; 30E

10’ N, 76E 55’ E; 268 m above MSL) and Yamunangar (Kalesar 30E 21’ N, 77E 34’ E, 339 m above MSL) in northern India. The

basal area, plant biomass production, and litter fall increased with increase in age of trees from 3 to 7 years. The soil organic

carbon pool in the Populus deltoides agroforestry systems was greater in agroforestry systems at Kalesar (22.31 to 27.82 Mg C

ha ) than at Salimpur (19.63 to 30.11 Mg C ha ). The carbon storage in the tree component varied in the range of 18.92 to 71.02-1 -1

Mg C ha at Kalesar and 14.78 to 56.91 Mg C ha at Salimpur. Carbon pool in wheat crop under Populus deltoides agroforestry-1 -1

systems was 3.70-3.53 Mg C ha at Salimpur and 3.84-3.68 Mg C ha at Kalesar. The carbon storage in water stable soil-1 -1

aggregates was directly related to soil organic carbon. The macroaggregates (2 mm-250 µm) formed 3.38 to14.88% part of bulk

soil at Salimpur and 10.56 to 18.82% at Kalesar; soil aggregate carbon was 0.21 to1.08% at Salimpur and 0.23 to 1.15 % at

Kalesar in 0-45 cm soil depths. The silt and clay fractions of soil microaggregates (< 53 µm) at both the sites protected a large

fraction of soil carbon. Illite, Kaolinite and Montmorillonite, Dolomite and Muscovite were the dominant minerals. Agroforestry

enhanced carbon storage in soil and the woody biomass and can play an important role in carbon sequestration for soil improving

soil health together with climate change mitigation.

Key Words: Plant Biomass Carbon; Soil Organic Carbon Pool; Soil Aggregate Carbon; Soil Fractions; Clay Mineralogy; X-ray

Diffraction

INTRODUCTION

Soil is a vital component in the functioning of terrestrialecosystems, provides a habitat for diverse andinteracting populations of soil organisms, accounts fordecomposition processes, and is a critical link in carbonsequestration (Gupta et al. 2009). Soil carbon in itsvarious pools within the soil, provides structure andstability to soil. Agriculture has an important role to playin climate change mitigation and adaptation throughcarbon sequestration, optimizing biomass production,and reducing greenhouse gas emissions.There is need totake appropriate measures to link agriculture and relatedland use to deliver on increased productivity, environ-mental sustainability, better livelihoods and foodsecurity to the people. Agroforestry is a dynamic land-

use system in which woody perennials are grown alongwith crops for maintaining soil productivity and biolo-gical diversity (Young 1997) and has a role in providingfood and nutritional security, controlling land degra-dation, and providing ecosystem services across a rangeof landscapes and economies (Nair 2007). Agroforestrycan be a good option for sequestering carbon in the soil-plant system (Nair et al. 2009). The service functions ofagroforestry are in control of soil erosion, wind breaker,maintenance and improvement of soil fertility, control ofweeds and fencing, and carbon sequestration (ICAR2006). Agroforestry models need to be developed forsustainable land management (Nair 2007, Alam et al.2009).

Soil organic carbon storage is the most acceptedmethod for long term carbon sequestration in terrestrial

Gaur and Gupta: Carbon Sequestration in Agroforestry System Int. J. Ecol. Environ. Sci.74

ecosystems. Therefore, it is of interest to pay moreattention to soil carbon sequestration potential in soils atdiffering spatial and temporal scales. Carbon seques-tration potential of agroforestry systems could bederived by combined information of aboveground carbonstorage, time averaged carbon stock in plant biomass andsoil carbon accumulation (Jose 2009). The potential ofcarbon sequestration in agroforestry systems depend onthe type of system, species composition, age of compo-nent species, land use type, environmental factors andmanagement practices (Kaur et al. 2002). Populus andEucalyptus based agroforestry systems on agriculturallands have been widely adopted by farmers in northernIndia (ICAR 2006). Agroforestry systems have beenreported to bring about changes in soil organic carbonthrough humification (conversion of biomass intohumus), aggregation (formation of organic mineralcomplexes as secondary particles), addition of carboninto sub soil by deep roots and leaching of carbon intoground water as bicarbonates (Nair et al. 2009). The aimof this study was to analyze the impact of Populusdeltoides based agroforestry systems on carbon storagein the plant-soil components in relation to site conditionsin northern Haryana.

MATERIALS AND METHODS

Study Site

In Haryana, Populus and Eucalyptus are two populartree species for agroforestry. The agroforestry systemsselected for this study are located at Kurukshetra(Salimpur; 30E 10’ N, 76E 55’ E; 268 m above mean sealevel (MSL)), and Yamunangar (Kalesar; 30E 21’ N, 77E34’ E, 339 m above MSL) in north-east Haryana innorthern India. The agroforestry systems are charac-terized by Populus deltoides on managed agriculturefarms (varying in size from 40 ha to 85ha) with a densityof 540 to 630 trees ha . The farm is fully mechanized-1

and irrigated. Sugarcane (Saccharum officinarum) wasgrown during first and second year of agroforestry onboth the sites. The wheat crop was grown in the inter-spaces between the rows of planted trees in 3-yr to 5-yrold agroforestry systems during the Kharif season, i.e.,November to April. Agronomic cultural practices for thewheat crop were applied as recommended in the packageand practice by the Haryana Agricultural University,Hisar. During the growing season of wheat 50 kg N ha-1

in the form of urea was applied in two split doses with

basal doze of double ammonium phosphate equivalent to50 kg N ha . Pre-irrigation before sowing of the crop-1

was done to ensure sufficient moisture availability insoil for good seed germination. The wheat crop receivedfour irrigations, i.e., during the tillering, heading,flowering, and grain filling stages

The climate of study area is tropical monsoonal.The soil of the study area is old alluvium which is sandyloam in texture. The annual rainfall was 605.5 mm atSalimpur and 1001.5 mm at Kalesar during the studyperiod from September 2008 to October 2009; more than80% is received during the rainy season. The meanmaximum and minimum temperatures in the two studysites were 41.3 EC and 8.4 EC (Salimpur), and 42.03 ECand 10.9 EC (Kalesar), respectively.

The soil is old alluvium, slightly alkaline (pH 7.25-8.32) with bulk density of 1.09 -1.49 g cm (Table 1).-3

The soil organic carbon varied from 7.7 to 1.2 g kg soil-1

at Salimpur and 8.1 to 1.7 g kg at Kalesar and inorganic-1

carbon 2.0 to 3.2 g kg at Salimpur and 0.8 to1.57 g kg-1 -1

soils at Kalesar in 0-45cm layer (Table 1).

Analysis of Plant Biomass

Trees (CBH >31.5 cm) were marked and their circum-ference measured at 1.37 m height from the ground infour sampling plots, each of 0.1ha established in 3, 5 and7-year-old Populus deltoides agroforestry systems. Thestand characteristics of the agroforestry systems selectedfor the study are given in Table 2. Biomass of trees wasestimated by dimension analysis of sample trees usingallometric regression equation between the circum-ference at breast height (cbh) and weight of various treecomponents including bole, branches, twigs, leaves, androots (Lodhiyal and Lodhiyal 1997, Lodhiyal et al.1995). Litter was collected at monthly intervals fromwithin 1 m × 1 m litter traps set out within the experi-mental plots at the study sites.

Analysis of Soil Aggregates and Clay Fractions

The surface (0-15 cm) and subsurface (15-30 cm, and30-45 cm) soil samples were collected with help of soilcorer from each sampling plot and a composite samplewas obtained for each agroforestry system type. The soilsamples were air-dried and sieved through 2 mm sievefor analysis of soil organic and soil inorganic carbon.

The water stable soil aggregates classified intothree size classes (2mm -250µm, 250 -53µm and <53µm) were analyzed using the wet-sieving method (Elliott

38: 73-85 Gaur and Gupta: Carbon Sequestration in Agroforestry System 75

Table1. Selected soil characteristics of Populus deltoides agroforestry systems at Salimpur (Kurukshetra) andKalesar (Yamunanagar) in northern Haryana. Values after ± are Standard Errors

Age Soil depth (cm) pH (1:2) Bulk density (g cm ) Organic carbon (g kg ) Inorganic carbon (g kg )-3 -1 -1

Salimpur

3-yr 0-15 7.59 ± 0.075 1.37 ± 0.037 5.7 ± 0.6 2.0 ± 0.02

15-30 8.15 ± 0.064 1.40 ± 0.032 2.5 ± 0.3 2.2 ± 0.01

30-45 8.32 ± 0.098 1.49 ± 0.051 1.2 ± 0.1 2.6 ± 0.04

LSD (P=0.05) 0.257 0.132 0.116 0.016

5-yr 0-15 7.52 ± 0.064 1.32 ± 0.021 6.6 ± 0.5 2.3 ± 0.03

15-30 8.11 ± 0.057 1.35 ± 0.013 3.4 ± 0.3 2.7 ± 0.05

30-45 8.24 ± 0.077 1.46 ± 0.052 2.1 ± 0.1 3.1 ± 0.06

LSD (P=0.05) 0.213 0.106 0.119 0.016

7-yr 0-15 7.49 ± 0.133 1.30 ± 0.033 7.7 ± 0.6 2.4 ± 0.07

15-30 7.72 ± 0.110 1.34 ± 0.035 4.5 ± 0.4 2.8 ± 0.12

30-45 8.05 ± 0.104 1.44 ± 0.019 2.8 ± 0.2 3.2 ± 0.15

LSD (P = 0.05) 0.372 0.097 0.13 0.036

Kalesar

3-yr 0-15 7.49 ± 0.030 1.18 ± 0.019 6.2 ± 0.39 0.8 ± 0.05

15-30 7.58 ± 0.060 1.43 ± 0.036 3.5 ± 0.25 1.0 ± 0.08

30-45 7.34 ± 0.054 1.45 ± 0.044 1.7 ± 0.29 1.3 ± 0.06

(P= 0.05) 0.159 0.111 0.101 0.023

5-yr 0-15 7.43 ± 0.080 1.12 ± 0.015 6.9 ± 0.6 0.91 ± 0.11

15-30 7.53 ± 0.078 1.39 ± 0.025 4.0 ± 0.32 1.12 ± 0.08

30-45 7.25 ± 0.068 1.42 ± 0.040 2.5 ± 0.25 1.44 ± 0.09

LSD (P=0.05) 0.241 0.092 0.135 0.032

7-yr 0-15 7.38 ± 0.079 1.09 ± 0.023 8.1 ± 0.76 1.13 ± 0.10

15-30 7.47 ± 0.098 1.32 ± 0.036 4.5 ± 0.39 1.24 ± 0.11

30-45 7.56 ± 0.057 1.40 ± 0.046 2.7 ± 0.25 1.57 ± 0.13

LSD (P = 0.05) 0.255 0.115 0.201 0.036

Table 2. Stand characteristics of Populus deltoides agroforestry systems at Salimpur and Kalesar.

Site Agroforestry systems Tree spacing (m) Average CBH (cm) Density (trees ha ) Basal area (m ha )-1 2 -1

Salimpur Populus deltoides + wheat (3 yr) 4.5 x 3.6 33.14 630 5.67

Populus deltoides + wheat (5 yr) 4.5 x 3.6 52.67 630 13.90

Populus deltoides (7 yr) 4.5 x 3.6 63.03 630 19.90

Kalesar Populus deltoides + wheat (3 yr) 4.2 x 4.4 46.66 540 9.78

Populus deltoides + wheat (5 yr) 4.2 x 4.4 68.24 540 20.09

Populus deltoides (7 yr) 4.2 x 4.4 85.75 540 32.01

1986). The bulk density was determined. Organic carbonconcentration in the plant samples of trees, crop plants,litterfall and roots was determined by the dichromateoxidation method. Soil inorganic carbon was determinedby rapid titration method. Sub samples of air-dried soil

and separated soil aggregates were analyzed for organiccarbon by dichromate oxidation method (Kalembasa andJenkinson 1973).

The silt, coarse clay and fine clay samples wereseparated from the soil by using International pipette

Gaur and Gupta: Carbon Sequestration in Agroforestry System Int. J. Ecol. Environ. Sci.76

method (Day 1965). The separated soil fractions wereanalyzed for organic carbon concentration. The fine clayfraction of the soil (<2µm) at Salimpur was used toexamine the clay mineralogical composition by the X-ray diffraction (XRD) method (Moore and Reynolds1989). The data on soil carbon and soil aggregatescarbon were analyzed using one way analysis ofvariance. Least significance difference (LSD) values at5% level of significance were calculated followingGomez and Gomez (1984).

RESULTS AND DISCUSSION

Biomass of Trees in the Agroforestry Systems

The total biomass of trees was (Mg ha ): 38.17 to-1

147.46 (Salimpur) and 46.19 to 173.29 (Kalesar). AtSalimpur, bole biomass of trees was 20.52, 50.49 and86.12 Mg ha in 3 yr, 5 yr and 7-yr-old agroforestry–1

systems, respectively. In agroforestry systems at Kalesar,the bole biomass was comparatively higher, the valuesbeing 24.76, 56.08, 100.76 Mg ha in 3 yr, 5 yr and 7-yr-–1

old, respectively. The total aboveground biomass wasestimated to be 31.41, 73.14 and 117.32 Mg ha for 3–1

yr, 5 yr and 7-yr-old agroforestry systems at Salimpur,respectively. At Kalesar, the aboveground biomass was

estimated to be 38.0, 80.97 and 137.64 Mg ha for the–1

for 3 yr, 5 yr and 7-yr-old agroforestry systems, respec-tively. Thus, total aboveground biomass was found to be12.26 to 17.35% greater for the agroforestry systems atKalesar as compared to that of the systems at Salimpur.The total biomass of trees increased with their age(Table 3).

The biomass of boles (bole wood+bole bark) wasfound to be maximum contributing 53.75 to 58.40 % oftotal biomass of trees at Salimpur, and 53.6% to 58.14%at Kalesar. The roots were found to contribute 16.52 to19.49 % of total tree biomass at both the study sites. Thebiomass of branches contributed about 10.76 % to13.23%; and foliage (leaves+twig) formed 10.40 to15.43 % of total biomass in different age agroforestrysystems (Table 3).

The biomass accumulation in different tree compo-nents of agroforestry systems was found to be in theorder: bole > roots > branches > foliage, a trendobserved by others also (Raizada and Shrivastava 1989,Lodhiyal and Lodhiyal 1997, Puri et al. 2002, Mishra etal. 2010). Aboveground biomass production by Populusdeltoides plantation (3-11-year-old) has been found tovary from 26.9 to 192 Mg ha (Tandon et al.1991). Puri-1

et al. (1992) reported that the biomass accumulation inPopulus deltoides agroforestry varied from 41 to 206 Mgha . Total biomass accumulation in different poplar-1

Table 3. Biomass (Mg ha ) in tree and crop components in the agroforestry systems at Salimpur and Kalesar -1

Agroforestry systems Biomass (Mg ha )-1

Salimpur Kalesar

3 yr 5 yr 7 yr 3 yr 5 yr 7 yr

Populus deltoides Trees

Bole wood 18.120 44.463 75.581 21.865 49.383 88.429

Bole bark 2.399 6.027 10.537 2.895 6.695 12.328

Branch 5.018 10.755 15.867 6.111 11.960 18.700

Twig 1.828 3.125 4.805 2.222 3.494 5.713

Foliage 4.041 8.768 10.526 4.906 9.435 12.467

Stump root 4.219 11.137 17.918 5.087 12.096 21.075

Lateral root 2.086 5.755 10.676 2.549 6.122 12.708

Fine root 0.461 1.043 1.548 0.558 1.187 1.871

Total 38.172 91.073 147.458 46.193 100.372 173.291

Wheat Crop

Shoot 4.674 4.450 - 4.753 4.508 -

Root 0.302 0.398 - 0.327 0.411 -

Grain 4.014 3.764 - 4.255 4.021 -

Total 8.990 8.612 - 9.335 8.940 -

38: 73-85 Gaur and Gupta: Carbon Sequestration in Agroforestry System 77

clones varied from 48.5 to 62.2 Mg ha in 6 year old-1

agroforestry systems (Puri et al. 1992) . In this study, thetotal biomass of the age old Populus deltoidesagroforestry systems varied in the range of 38.17 to173.29 Mg ha across sites and ages. -1

Crop Biomass in the Agroforestry Systems

In 3-5- year-old Populus deltoides agroforestry systems,wheat crop was grown during the Kharif season(November to April). At time of crop harvest, thebiomass accumulation in the wheat crop was 8.99 and8.612 Mg ha at Salimpur; 9.335 and 8.940 Mg ha at-1 -1

Kalesar (Table 3). The grain production decreased from

6.23% at Salimpur and 5.51% at Kalesar in 5 yr oldagroforestry systems as compared to that in 3 yr oldplantation of both the sites.

Carbon Pool in Tree Components

The carbon concentration in different tree componentsof Populus deltoides was: bole (38.75%); branches(40.05%); coarse roots (36.94%); fine roots (37.15%)and leaves (39.15%) at Salimpur. In the agroforestrysystems at Kalesar carbon concentration in different treecomponents was: bole (42.76%); branches (39.75 %);coarse roots (36.94%); fine roots (37.80%) and leaves(40.46%) (Table 4). The total carbon pool in agro-forestry systems at Salimpur was 14.77, 35.18 and 56.91Mg C ha , where as the carbon pool in the trees was-1

18.92, 41.12 and 71.02 Mg C ha at 3, 5 and 7 years old-1

agroforestry systems in Kalesar, respectively (Table 5).

Table 4. Carbon concentration (%) in tree and cropcomponents in the agroforestry systems at Salimpurand Kalesar. Values after ± are Standard Errors

Agroforestry System Carbon Concentration

Salimpur Kalesar

Populus deltoides Trees

Bole 38.75 ± 0.84 42.76 ± 1.04

Branch 40.05 ± 0.66 39.75 ± 0.87

Leaves 39.15 ± 0.52 40.46 ± 0.78

Coarse roots 36.94 ± 0.41 36.94 ± 0.45

Fine roots 37.15 ± 0.38 37.80 ± 0.71

Wheat Crop

Shoots 38.03 ± 0.81 38.03 ± 0.81

Roots 37.34 ± 0.39 37.34 ± 0.39

Grains 45.00 ± 0.50 45.00 ± 0.50

The organic matter input in the form of litter fallwas 1.58, 3.43 and 4.12 Mg C ha at Salimpur and 1.98,-1

3.82 and 5.04 Mg C ha at Kalesar (Table 5). The-1

carbon accumulation in different tree components wasfound in the order: bole >roots >foliage >branch. Studieshave shown that carbon pool was high in stems followedby branches and roots (Swamy and Puri 2005, Singh andSingh 1997). Swamy et al. (2003) emphasized that thespecies diversity, site quality, nature of land use andmanagement practices are important for carbon seques-tration. In this study, it was found that there was markedeffect of soil and climate on carbon accumulation in theagroforestry systems, the values being higher for thesystems at Kalesar experiencing a subhumid climatewith an average annual rainfall of 1001.5mm. The soilorganic carbon was also greater for the agroforestrysystems at Kalesar. Razvi et al. (2011) estimated carbonstorage of 66-83 Mg ha by poplar in agrisilviculture-1

systems with 7-year rotation period.

Carbon Accumulation in Wheat Crop

The carbon percentage in wheat crop at time of harvestwas 38.03 % in wheat shoot and 37.34% in wheat rootunder Populus deltoides agroforestry systems. Carbonaccumulation in crop was found to be higher in shootsthan in roots and grains. The carbon accumulation incrop shoot varied from 1.778 to 1.692 Mg C ha in-1

agroforestry systems at Salimpur and 1.808 to 1.715 MgC ha for the agroforestry systems at Kalesar. Root-1

carbon accumulation was 0.113 to 0.149 Mg C ha-1

(Salimpur) and 0.122 to 0.154 Mg C ha (Kalesar) The-1 .

grains accumulated 1.806 to 1.694 Mg C ha (Salimpur)-1

and 1.914 to 1.809 Mg C ha (Kalesar) at the study sites-1

(Table 5).

Biomass Carbon Pool in the Agroforestry Systems

Carbon pool in wheat crop under Populus deltoidesagroforestry systems was 3.70-3.53 Mg C ha at-1

Salimpur and 3.84-3.68 Mg C ha at Kalesar (Table 6). -1

The total aboveground carbon storage varied from 12.28to 45.77 at Salimpur and 15.88 to 57.83 Mg C ha at-1

Kalesar in 3- to 7-year-old agroforestry systems. Totalbelowground carbon accumulation increased from 2.5 to11.14 Mg C ha at Salimpur and 3.03 to 13.19 Mg C ha-1 -1

at Kalesar with increase in age of the system from 3years to 7 years (Table 6).

Gaur and Gupta: Carbon Sequestration in Agroforestry System Int. J. Ecol. Environ. Sci.78

Table 5. Carbon storage (Mg C ha ) in different tree and crop components of agroforestry systems at Salimpur and-1

Kalesar.

Agroforestry systems Plant Biomass Carbon (Mg C ha )-1

Salimpur Kalesar

3 yr 5 yr 7 yr 3 yr 5 yr 7 yr

Populus deltoides Trees

Bole wood 7.022 17.229 29.288 9.349 21.116 37.812

Bole bark 0.930 2.335 4.083 1.238 2.863 5.271

Branch 2.010 4.307 6.355 2.429 4.754 7.433

Twig 0.732 1.252 1.924 0.883 1.389 2.271

Foliage 1.582 3.433 4.121 1.985 3.817 5.044

Stump root 1.558 4.114 6.619 1.879 4.468 7.785

Lateral root 0.771 2.126 3.944 0.942 2.261 4.694

Fine root 0.171 0.387 0.575 0.211 0.449 0.707

Total 14.775 35.184 56.908 18.916 41.118 71.019

Wheat Crop

Shoot 1.778 1.692 - 1.808 1.7148 -

Root 0.113 0.149 - 0.122 0.154 -

Grain 1.806 1.694 - 1.914 1.809 -

Total 3.697 3.535 - 3.844 3.677 -

Table 6. Aboveground biomass (AGB) and belowground biomass (BGB) and total biomass carbon pool (Mg C ha )-1

in Populus deltoides agroforestry systems at Salimpur and Kalesar.

Site Age (yr) Biomass (Mg ha ) Biomass Carbon (Mg C ha )-1 -1

AGB BGB Total AGB BGB Total

Salimpur Trees 3-yr 31.406 6.766 38.172 12.276 2.5 14.775

5-yr 73.138 17.935 91.073 28.556 6.627 35.184

7-yr 117.316 30.142 147.458 45.771 11.138 56.908

Salimpur Crop 3-yr 8.688 0.302 8.990 3.584 0.113 3.697

5-yr 8.214 0.398 8.612 3.386 0.149 3.535

Kalesar Trees 3-yr 37.999 8.194 46.193 15.884 3.032 18.916

5-yr 80.967 19.405 100.372 33.939 7.178 41.118

7-yr 137.637 35.654 173.291 57.831 13.186 71.019

Kalesar Crop 3-yr 9.008 0.327 9.335 3.722 0.122 3.844

5-yr 8.529 0.411 8.940 3.523 0.154 3.677

Soil Carbon Pool

The soil organic carbon (SOC) concentration wassignificantly higher in surface (0.81%) as compare tosubsurface soils (0.12 %). The study showed that SOCalso increased significantly with tree age. Several studies

have shown improvement in soil fertility due to organicmatter inputs from litter fall and fine roots with age oftrees (Campbell et al. 1988, Browaldh 1995).

The total SOC pool varied from 19.63 to 30.11 MgC ha at Salimpur and 22.31-27.82 Mg C ha at Kalesar-1 -1

(Table 7). The soil inorganic carbon (SIC) varied from

38: 73-85 Gaur and Gupta: Carbon Sequestration in Agroforestry System 79

18.43 -17.22 Mg C ha at Salimpur and 6.49 -7.61 Mg-1

C ha at Kalesar in 0-45cm soil layer. The SOC was-1

higher in surface as compared to subsurface soilswhereas the SIC was lower in surface as compared tosubsurface soil. The total soil carbon pool varied in therange of 38.06-47.33 Mg C ha at Salimpur compared to-1

28.80-35.42 Mg C ha at Kalesar. Several workers have-1

reported that the carbon sequestered in soils underagroforestry from biomass turnover is greater than underconventional agriculture (Paul et al. 2002, Sharrow andIsmail 2004, Sauer et al. 2007). Nair et al. (2009)reported values for soil organic C stocks ranging from6.9 to 302 Mg ha from different climatic regions of the!1

world. The differences in soil carbon stocks have beenattributed to the variation between systems, ecologicalregions, and soil types. These workers showed a generaltrend of increasing soil C sequestration in agroforestryas compared to other land-use practices, excepting thenatural forests (Nair et al. 2009).

Table 7. Soil organic carbon pool (Mg C ha ) at-1

different soil depths in different agroforestrysystems at Salimpur and Kalesar.

Site Age Soil Organic Carbon Pool (Mg C ha )-1

0-15 cm 15-30 cm 30-45 cm Total

Salimpur 3-yr 11.62 5.302 2.710 19.63

5-yr 13.07 6.88 4.60 24.55

7-yr 15.02 9.04 6.05 30.11

Kalesar 3-yr 10.98 7.48 3.85 22.31

5-yr 11.59 8.34 5.32 25.25

7-yr 13.21 8.93 5.68 27.82

Soil Aggregate Carbon

The proportions of macroaggregates (2mm-250 µm) wasfound to be greatest in the case of 7-yr old Populusdeltoides agroforestry systems at Kalesar (18.82%) andlowest in the age of 3-yr old Populus deltoides systemsat Salimpur (5.18%) (Figure 1). The proportion ofmicroaggregates (53-250 µm) ranged from 15.3 to33.71% at Salimpur and from 41.48 to 51.69% atKalesar; the differences across the two sites weresignificant (F= 4.08 to 19.43, d.f., 2, 9 P < 0.05). Theclay and silt (<53µm) associated soil fractions formed51.41 to 81.32 % in soils of the agroforestry systems at

Salimpur, and 29.49 to 46.78 % in soils of differentagroforestry systems at Kalesar ; the differences acrossthe two sites were not significant ( F= 1.55 to 3.78 , d.f.,2,9 P > 0.05) (Figure 1).

The organic carbon concentration up to 0-45 cmsoil depth in macroaggregates (2 mm-250 µm; 1.15 to0.65 %) was significantly higher than that of micro-aggregates (250 µm to 53 µm; 0.48 to 0.07 %) in all thesystems. The carbon concentration was found todecrease along the soil depth in the various size classesof soil aggregates; the differences were highly signi-ficant (F= 14.07 to 41.06, d.f. =2, 9; P < 0.05). Thecarbon concentration in macroaggregats was higher at 0-15 cm soil depth (0.65-1.15%) as compared to 15-30cm(0.34-0.62%) and 30-45cm soil depths (0.21-0.48%)(Figure 2).

The carbon percentage in soil aggregates wasgreater in agroforestry systems at Kalesar (0.19 to1.15%) as compared to that of soils at Salimpur (0.17 to1.08%). Soil organic carbon associated with aggregatesis an important reservoir of carbon, protected frommineralization because of physical, microbial andenzymatic degradation (Trujilo et al. 1998). The soilorganic carbon in microaggregates is stabilized and hasimportant role in soil carbon sequestration (Shrestha etal. 2007, Udawatta et al. 2008). With increase in soildepth, there was increase in silt and clay fraction anddecrease in macroaggregate and microaggregates indifferent agroforestry systems.

Carbon in Silt and Clay Fractions

In the agroforestry systems at Salimpur, carbon concen-tration in different soil fractions was: silt, 0.55 to 0.15%;coarse clay, 0.88 to 0.37%; fine clay 0.96 to 0.54 %(Figure 3). In the case of agroforestry systems at Kalesar,organic carbon concentration in different soil fractionwas: silt, 0.75 to 0.19%; coarse clay, 0.94 to 0.43%; fineclay carbon 1.06 to 0.58 % (Figure 3). The organiccarbon in different soil fraction was in the order: fineclay (%)> coarse clay (%)> silt (%) in different systems.The carbon concentration was found to decrease alongwith the soil depth in the various soil aggregatesfractions; the differences were highly significant (F=4.48 to 39.34, d.f. =2, 9; P < 0.05). The organic carboncontent is more in coarse clay and fine clay as compareto silt at Salimpur: coarse clay, 1.41 to 2.47%; fine clay1.55 to 3.60%. At Kalesar, the carbon concentration inthe soil fractions was: coarse clay, 1.25 to 2.23%; fineclay 1.41 to 3.01%. Gonzalez and Laird (2003) estimated

Gaur and Gupta: Carbon Sequestration in Agroforestry System Int. J. Ecol. Environ. Sci.80

Figure 1. Percentage soil weight in aggregate size classes in the Populus deltoides agroforestry systems at Salimpur (A) and Kalesar (B).

38: 73-85 Gaur and Gupta: Carbon Sequestration in Agroforestry System 81

Figure 2. Soil organic carbon concentration in soil aggregates in the Populus deltoides agroforestry systems at Salimpur (A) and Kalesar (B).

Gaur and Gupta: Carbon Sequestration in Agroforestry System Int. J. Ecol. Environ. Sci.82

Figure 3. Organic carbon concentration in silt and clay fractions of soils in the Populus deltoides agroforestry systems at Salimpur (A) and

Kalesar (B).

38: 73-85 Gaur and Gupta: Carbon Sequestration in Agroforestry System 83

Figure 4. X-ray diffraction pattern of soil clay sample of 7-year old Populus deltoides agroforestry system at Salimpur, Kurukshetra

the organic carbon content in coarse clay and fine clayfractions to be 3.7 and 3.93%, respectively.

XRD Analysis of Clay Minerals

The mineralogy of the clay samples of Salimpur, asinterpreted by XRD pattern showed that Quartz, Illite,Kaolinite and Chlorite were the dominant minerals,while Montmorillonite, Calcite, Dolomite and Muscoviteare present in lesser amount (Figure 4). The two non-clay minerals such as Quartz and Calcite were alsoshowed their peaks. Montmorillonite and Kaolinite werepredominant in the soils of the agroforestry systems.XRD analysis is a valuable tool for gaining insight intothe interactions between clay minerals and organicmatter (Pereira et al. 2008). Clay contains differentminerals such as Illite, Montmorillonite, Smectite,Kaolinite and Chlorite (Gonzalez and Laird 2003). Soilorganic carbon is sequestered in form of Smectite(Montmorillonite) and Kaolinite form of clay (Gonzalezand Laird 2003).

In this study, the illite and montmorillonite (amember of the smectite family, 2:1 clay) were predomi-nant in the soil. Gonzalez and Laird (2003) whilestudying the distribution of newly formed humic

materials into mineralogically distinct clay size fractionson a silt loam soil showed that new humic materials arepreferentially accumulated on smectite surfaces. In thisstudy, the predominance of illite and montmorillonite inthe clay could play an important role in soil carbonstability. The association of organic matter in soil withminerals is a controlling factor of C storage in soil. Thetransfer of plant residues into stabilized clay humiccomplex is the main process which regulates soil qualityand determines soils as a net sink and source of carbon.

CONCLUSIONS

Poplar-based agroforestry systems in Kurukshetra andYamunanagar districts of northeast Haryana produceconsiderable amount of plant biomass, which play animportant role in carbon sequestration by increasing totalbiological productivity of the agroforestry systems aswell as in wood products of the processed raw materialsupplied to the plywood industry. The study showed thatthe agroforestry systems in Kalesar build up larger poolsof carbon in plant as well as soil than in Salimpur. Thiscould be attributed due to the fact that climate at Kalesar

Gaur and Gupta: Carbon Sequestration in Agroforestry System Int. J. Ecol. Environ. Sci.84

is sub-humid experiencing annual rainfall of 1001.5mmannually, whereas the systems at Salimpur experienceda semiarid climate(605.5mm annual rainfall). Theaverage litterfall from the trees in the agroforestrysystems at Kalesar (8.936 Mg dry matter ha ) was also-1

greater as compared to the agroforestry systems atSalimpur (7.778 Mg dry matter ha ). Thus, agroforestry-1

was found to be sustainable land-use system forincreasing biological productivity as well as providingenvironmental services for carbon sequestration. In thisstudy, the predominance of illite and montmorillonite inthe clay could play an important role in soil carbonstability. Thus, these agroforestrty systems makeimportant contribution towards carbon storage and couldplay a significant role in mitigation of climate change.

ACKNOWLEDGEMENTS

Thanks are due to Mr Ranjit Raina for extending help towork on the agroforestry systems at his agricultural farmat Salimpur. We are also thankful to the chair-person ofBotany department, Kurukshetra for providing us thenecessary facilities for this work.

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Received 1 October 2012;Accepted after Revision 26 October 2012