Belowground carbon stocks of 21 year old Grevillea robusta stand in the humid tropics of Kerala

College of Forestry, Kerala Agricultural UniversityThrissur, Kerala- India*thakur.samritika@gmail.com

Samritika*, T. K. Kunhamu, B. Mohankumar and K. Sudhakara

2MPTsC sequestration potentialLack of quantitative information!!CDM PROJECTSEarly returnsProduct diversificationClimate change mitigationChoice of speciesBelowground biomassDemandIndirect benefitsBiomassINTRODUCTIONWhy Silver oak??3Shade treeHomesteadsSupport tree for pepperWood productsGood quality litterFavourable physical and mechanical propertiesFast growthLess branching crown and needle like leaf

Belowground biomassSite enrichment C sequestrationBelowground CarbonBGB CSoil CWe focus on!!!Estimation of biomass accumulation of roots.

Determination of belowground carbon stocks of Grevillea robusta plantation.

4MATERIALS AND METHODSLocation: 21-yr-old Grevillea robusta stand Vellanikkara, Thrissur, Kerala , India

Establishment year: 1991

Study period: Dec 2011 to Dec 2012

Climate: warm humid

Mean annual rainfall: 239.08 mm

Soil : Ultisol with pH 5.4

SPSS 17

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A) DESTRUCTIVE SAMPLING7

Small tree (5-15 cm dbh)Medium tree (15-25 cm dbh)Large tree(>25 cm dbh)8

Oven drying

Weighing balanceDry matter Moisture % =Fresh weight (g)-Dry weight (g) X 100 Fresh weight (g) Dry matter (kg) = Dry weight of sample (g) X Fresh weight of entire root system (kg) Fresh weight of sample (g)

Biomass estimation9

Analysis

ChoppingGrindingFine powderWeighing balance

CHNS analyzerBelowground biomass C determination B) SOIL SAMPLINGFive profile pits were cut randomly and soil samples were collected, horizon-wise up to 1 m depth.

Soil sampling for bulk density (BD) measurement was done using a steel cylinder (Jackson, 1958).

Soil organic carbon : Walkley and Black method.

Soil C sequestration: Anderson and Ingram, 1989

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Table 1. Mean tree root dry matter production for various root girth classes among different diameter class for 21-yr-old Grevillea robusta stand at Vellanikkara, Thrissur.

Diameter class (cm)Mean tree root dry matter production (kg tree-1)Root girth class (cm)Tap rootTotal0-1011-2021-3031-405-153.89b(0.85)2.29(1.18)______6.76b(1.22)12.94c(2.23)15-255.81ab(0.59)6.55(1.66)4.75(2.10)___28.51a(4.18)45.62b(4.23)>258.02a(1.56)8.70(2.40)5.26(2.27)0.90(0.00)36.93a(4.89)59.81a(6.55)Total17.7217.5410.010.9072.2118.37Sig 0.05%signsnsnssigsig11ns- non significantValues in parenthesis are standard errorRESULTFig. 1. Mean annual increment in dry matter in different root girth classes of 21-yr-old Grevillea robusta stand at Vellanikkara, Thrissur.

12Table 2. Comparison of tree root MAI (Mg ha-1 yr-1) of 21-yr-old Grevillea robusta tree with other speciesSpeciesMAI (Mg ha-1 yr-1)

ReferenceAilanthus triphysa0.60-1.10Shujauddin and Kumar, 2003Ailanthus triphysa0.84Jamaludheen, 1994Casuarina equisetifolia0.63Jamaludheen, 1994

Leucaena leucocephala0.36Jamaludheen, 1994

Pterocarpus marsupium0.83Jamaludheen, 1994

Grevillea robusta0.88Present study13Table 3. Mean carbon content in different root girth classes belonging to different diameter classes of 21-yr-old Grevillea robusta stand at Vellanikkara, Thrissur.14Diameter class(cm)Mean carbon content (kg tree-1)Root girth class (cm)Tap rootTotal0-10 11-20 21-3031-405-151.71b(0.13)1.07c(0.03)______2.80b(0.21)5.5815-252.64a(0.00)2.87b(0.04)2.07b(0.01)___12.90a(1.09)20.48>253.54a(0.32)3.75a(0.06)2.41a(0.00)0.38a(0.00)13.77a(0.98)23.58Mean2.632.562.240.389.8217.63MAI0.130.120.110.020.470.84Sig 0.05%sigsigsigsigsigns- non significantValues in parenthesis are standard errorTable 4. Stand level belowground biomass C stocks for 21-yr-old Grevillea robusta stand at Vellanikkara, Thrissur.

15Diameter class (cm)Belowground C (Mg ha-1)Root girth class (cm)Tap rootTotal0-1011-2021-3031-405-150.19c(0.01)0.12c(0.00)_________0.31b(0.02)0.6215-250.73a(0.00)0.79a(0.01)0.57a(0.00)____3.56a(0.30)5.65>250.26b(0.02)0.28b(0.00)0.18b(0.00)0.03a(0.00)1.02b(0.07)1.77Total1.181.190.750.034.898.04Mean0.390.400.380.031.632.83MAI0.060.060.040.0010.230.38Sig 0.05%sigsigsigsigsigFig. 2. Variation in soil bulk density between tree field and treeless control as function of soil depth for 21-yr-old Grevillea robusta stand at Vellanikkara, Thrissur.

16Soil AnalysisFig. 3. Variation of soil carbon stocks of field and control plots with depth in 21-yr-old Grevillea robusta stand at Vellanikkara, Thrissur.

17Field= 77.45 Mg ha-1 Control=66.01 Mg ha-1Fig. 4. Variation in rate of soil carbon sequestration between tree field and treeless control as function of soil depth for 21-yr-old Grevillea robusta stand at Vellanikkara, Thrissur.

18Fig. 5. Variation in total belowground carbon stocks between stand and treeless control site for 21-yr-old Grevillea robusta stand at Vellanikkara, Thrissur.

19IMPLICATIONSGrevillea robusta higher biomass and higher carbon sequestration potential suggesting better understorey productivity in polyculture systems involving Grevillea. Improvement in soil under tree stand.C content in soil varies with depth and management practices.C partitioning follows biomass production patterns.AG dimensions strongly influence the BGB production.Roots potential contributor to total biomass and C pools.Tree plantations-efficient tool to mitigate climate change. Need for in depth screening of MPTs.Lack of such information about commercially important species.

20THANK YOU21