Carbon sequestration in sub-tropical soils under rubber plantations in north-east India potx

C arbon sequestration in sub-tropical soils under rubber plantations in north-east India Debasis Mandal and K.. Islam Indian Rubber Research Institute, Tripura, and University South Cent

C arbon sequestration in sub-tropical

soils under rubber plantations in

north-east India

Debasis Mandal and K R Islam

Indian Rubber Research Institute, Tripura, and

University South Centers, USA

Widespread deforestation for fuelwood,

timber and forage is an on-going process

in the south-east Asian countries

(Islam et al 1999)

Rubber plantations were raised as a secondary

forest in the Indian state of Tripura since 1975 to improve degraded lands, generate income for

locals, and meet increasing demand for rubber

I t is expected that reforestation of degraded

(Wallace 1994, Islam et al 1999)

T his study was conducted to evaluate the

stocks, and sequestration in reforested

degraded sub-tropical forest lands in

Tripura, India

Materials and methods

Site: 10,412 ha of rubber plantations

of different ages at

Kunjaban, Agartala, NE India

Sample plots from 5, 10, 15, 20, 25, and 30 yrs old rubber plantations with a control (initial).

Standing biomass and annual C flow as litter-fall Soil sampled at 0 - 15 and 15 - 30 cm depths

Oxidizable organic C (COX)Non-oxidizable C (CNOX)Total C (CT)

Bulk density

C concentration and stocks

Data analysis by SAS as 7 (age) x 2 (soil depth) factorial combination at p<0.05.

Results and Discussion

Table 1: Standing biomass of

different ages of rubber plantations

_

Plantation Shoot Root Total

age (year) biomass (Mg ha -1 )

_

0 (initial) 16.8c 4.2d 21.0c

10 121.3b 26.6b 145.9b

15 156.0ab 29.4ab 185.5ab

20 160.4ab 32.4a 193.4a

25 160.7ab 31.9a 192.9a

30 161.7a 29.9ab 191.6a

Table 2: Biomass C of different ages

of rubber plantations

_

Plantation Shoot Root Total

Age (year) _ biomass C (Mg ha -1 )

_

_

Years after plantation

Years after plantation

15-30-cm depth: y = 1.61- 0.002*X r2=0.37ns

Years after plantation

Years after plantation

r 2 =0.57*

Years after plantation

Years after plantation

Years after plantation

y = 30.32 + 15.13*(1-exp(-0.088*X)

r 2 = 0.55*

Years after plantation

Years after plantation

Years after plantation

Years after plantation

Years after plantation

Table 4: Profile-wise C sequestration rates in soils under different ages of rubber plantations

-5 1.9+0.2a 1.7+0.6a 3.5+0.4a

10 1.7+0.1ab 1.1+0.4ab 2.8+0.3ab

Standing biomass, biomass C content, and annual litter-fall of rubber plants quadratically and significantly increased

Greater accumulation litter-fall on the surface linearly and significantly decreased soil

compaction The beneficial effects of litter-fall

on decreasing compaction was greatest on surface soil.

soil compared to a non-linear increase in

stocks increased quadratically over time

Summing the C content over soil depth, the profile-wise accumulation of various C

fractions increased non-linearly over time

Thanks