Aboveground carbon stock changes
Aboveground carbon content estimation of each land cover was calculated by multiplying the area of each land cover with carbon stock per unit area. Table 3 has showed the changes of aboveground carbon due to land cover changes. Total above ground carbon stock decrease from 6.16 x 10⁸ ton in 1986 to 5.66 x 10⁸ ton in 1992 or loss of about 0.50 x 10⁸ ton within 6 years equal to 8.3 millions ton per year. The loss of aboveground carbon was mainly came from primary forest conversion. IPCC have divided the loss of aboveground carbon content into on site and off-site release. These two categories were classified further into direct burning (fuel wood and slash and burn agricultural) and decomposition process release of unburned biomass (Houhton et.al., 1996). Thus the amount of carbon and GHG released to the atmosphere were depended on these processes. Estimation of the amount carbon and GHG release need yearly basis time series of spatial data and the information on commercial wood and fuel wood harvest, and burning efficiency data of each land cover type.

Soil Greenhouse gas emission changes
GHG flux of soil varies depend on type the site condition and season. The comparisons below were made based on flux measurement conducted in November 1997 in several sites of Jambi Province. The calculation results of total flux based on 1986 and 1992 land cover data for major land cover presented in Table 4. Comparison of the total GHG flux of the two periods of time studies could not be performed since there are still no information on GHG flux of soil surface under cash crops plantation and secondary forest. However, it seems that the conversion of natural forest will cause on the decrease of methane gas absorption and induce the increase of nitrous oxide and carbon dioxide flux emission.
Table 4 Greenhouse gases flux changes between 1986 and 1992

Land- use/Land cover class	Total flux of CO2 (mg/day)		Total flux of N2O (mg/day)		Total flux of CH4 (mg/day)
	1986	1992	1986	1992	1986	1992
Primary forest	1.69x1014	1.28x1014	3.2x109	2.43x109	-1.45x1010	-1.10x1010
Secondary forest	0.00	5.75x1012	0.00	7.03x108	0.00	-3.36x109
Logged forest	1.24x1014	1.54x1014	2.48 x109	3.08x109	-1.04x1010	-1.29x1010
Fallow land	1.31x1014	8.46x1013	4.51 x109	2.91x109	-1.00x1010	-6.47x109
Grassland	7.76x1012	7.58x1012	1.42 x108	1.38x108	0.00	0.00
Bare land	2.44x1010	2.44x1010	5.67x105	5.67x105	-6.25x105	-6.25x105
Cash crops plantation*	1.87x1013	6.75x1013	4.68x108	1.69x109	0.00	0.00
Paddy field	-	-	9.63x107	6.23x107	7.22x108	4.67x108
Upland field	0.00	2.41x1012	0.00	4.03x107	0.00	0.00
Cultivated land and Secondary vegetation	8.00x1013	9.02x1013	3.43 x109	3.87x109	-3.33x109	-3.75x109
Cultivated lands and Settlement	6.85x1012	8.33x1012	1.16 x108	1.41x108	0.00	0.00
Total flux	536.5x1012	548.3x1012	14.4 x109	15.1x109	-37.5x109	-37.0x109

Note : calculations were made based on field measurement in November 1997, conducted by IC-SEA

* : assumed flux of CH4 and CO2 of cash crops plantation are equal upland, while flux of N2O is equal to three times of upland field flux due to intensive fertilizer application.
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