Carbon stock assessment for a forest to coffee conversion landscape in Sumber Jaya (Lampung, Indonesia) from allometric equations to land use change analysis

The change in stored carbon (C) stocks was assessed for a 700 km 2 area where forest cover decreased from 60% to 10% in the last 30 years. At the same time, the area under coffee increased from 7% to 70% with a gradual evolution from open "sun coffee" systems to multi-strata "shade coffee" systems that provide a partial compensation for C loss. The use of a generic tropi- cal forest rather than tree-specific allometric equation can lead to substantial (up to 100%) overes- timates of aboveground biomass depending on wood density and tree shape. The shoot:root ratio (biomass) of coffee shifted with age, from the 4:1 value often assumed for tropical trees to 2:1. Annual aboveground C stock accumulation rates during the establishment stage after slash-and- burn land clearing were 1, close to 2 or 3.5 Mg C ha1a1 for sun coffee, shade coffee and fallow regrowth, respectively. Forest remnants, shade coffee and sun coffee had soil C stocks in the up- per 30 cm of the soil that were 79%, 60% or 45%, respectively, of the values expected for primary forest in Sumatra. Total C stock (time averaged, above - 0.3 m in the soil) for forest, shade and sun coffee was 262, 82 and 52 Mg C ha1, respectively. In the 19701984 period, while forest cover was reduced from 59.5% to 19.7%, the landscape lost on average 6.8 Mg C ha 1 a 1 .I n the 19842000 period forest cover was further reduced to 12.6%, but the landscape lost only 0.39 Mg Ch a 1 a 1 , as forest loss was partially compensated by an increase in shade coffee systems. Conversion of all current sun coffee to shade coffee systems while protecting the remaining forest, could increase average landscape level C stocks by 10 Mg ha1 over a time frame of say 20 years, or 0.5 Mg C ha1 a1.

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