Carbon stock in planted woodlots at Kongowe, Kibaha, Tanzania

Forest degradation due to extraction of wood for fuelwood and charcoal production or agricultural expansion is one of the main sources of carbon dioxide (CO2) emissions in Africa. Woodlots can offset CO2 emissions while sustainably meeting the wood demand of local communities. However, the amount and dynamics of carbon (C) stored in soils in coastal area woodlots and the contribution of this practice to climate change mitigation is largely unexplored. This study evaluated wood biomass and C stocks in woodlots, forest reserves and farmland with Acacia crassicarpa Benth., Acacia mangium Wild., and Acacia auriculiformis Benth. to determine their ability to sequester soil C and offsetting CO2 emissions. Woodlots of fast-growing Acacia spp. produced wood (30 to 62 Mg C/ha), which may meet the household fuelwood demand for up to 10 to 20 years and offset up to 31 Mg C/ha of C emissions. Moreover, these species stored soil organic carbon (SOC) (58 Mg C/ha), which was similar to levels in the native forests; demonstrating climate change mitigation capacity. The effects of tree species on SOC was confined to the top 40 cm with native forest consistently recording the highest values. This improvement was attributed to litter and root turnover, C leaching and mixing of SOC by microorganisms, and increased recalcitrant form of SOC with depth. Because of the sandy soil texture in the study site, most of SOC stocks (up to 70% in the bulk soil and 50% in fractionated soils) were in the labile fractions and prone to degradation. Of the tested woodlot species, A. auriculiformis showed the highest promise to produce wood and improve SOC because of higher survival. Our results showed that woodlots systems utilizing the fast growing tree species hold high promise to mitigate atmospheric CO2 increase through on-farm wood supply to alleviate harvesting pressure and accumulation of SOC in the soil

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DOI:

https://doi.org/10.3920/978-90-8686-788-2_4

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