Abstract
Anthropogenic activities have the potential to thwart efforts towards enhancing the full carbon (C) sink potential of savannas in the context of mitigating the effects of global warming. The understanding of the induced effects of human pressures on the carbon budget of forestË—savanna ecosystems is therefore a valuable tool to better evaluate and predict the current and future effects of human activities on the potential of these forests to sequester carbon in the context of the fight against the global warming. In line with this, the objective of this study was to compare the soil organic carbon stock changes between three well protected forests and three neighbouring unprotected forests which are prone to human pressures (except farming and settlements) in the natural forestË—savanna of Northern Ghana. Three study zones, namely Wungu, Serigu and Mognori were used for the study. For each forest type 30 m × 30 m random plots and 1 m × 1 m random subplots were used to generate data for the comparative analysis. A total of 160 random soil samples (0 to 50 cm depth), 96 random samples of aboveground live biomass, and the same number of litter and root biomass samples were collected in both forest types of each study zone to make composite samples for the determination of plant and soil organic carbon contents. The results of the study showed that total plant C (C in live biomass + litter + roots) was three times higher in the protected forest sites than the unprotected across the three study zones. Soil organic carbon stores were significantly (P< 0.01 and P< 0.05) higher in the protected forest sites than the unprotected. Across the three study zones, soil C store was in general twice greater in the protected sites than the unprotected. The present study indicates the need for employing ecologically and socio-economically sustainable management plans for savanna woodland resources in the region, in collaboration with local communities, so as to sustain communitiesá¾½ livelihoods, besides preserving the full potential of this forestË—savanna to sequester C in the context of the fight against the global climate change. Key words: Anthropogenic activities, climate change, forestË—savanna.  
Highlights
It is established that anthropogenic carbon dioxide ( emission into the atmosphere plays a vital role in driving the global climate change (Petit et al, 1999; Falkowski et al, 2000), which in turn affects the productivity of terrestrial ecosystems (Nemani, 2003)
The patterns and controls of soil organic carbon (SOC) storage are critical for our understanding of the biosphere, given the importance of SOC for ecosystem processes and the feedback of this pool to atmospheric composition and the rate of climate change (Raich and Potter, 1995)
It is established that more than three-quarters of the ecosystem organic carbon in woodlands and savannas is in the soil (Scholes and Hall, 1992), and that removal of trees leads to an overall decline in SOC over a period of years (Jones et al, 1990; Vitousek, 1981)
Summary
The global carbon cycle is being altered in response to human interference; for instance land-use changes in the tropics are estimated to contribute about 23% to human-induced CO2 emissions (Houghton, 2003). Because of the significant capacity for carbon storage, soil has been the focus of increasing efforts in assessing the carbon sequestration associated with land-use change and ecosystem succession (Post et al, 1982; Degryze et al, 2004). The patterns and controls of soil organic carbon (SOC) storage are critical for our understanding of the biosphere, given the importance of SOC for ecosystem processes and the feedback of this pool to atmospheric composition and the rate of climate change (Raich and Potter, 1995). Our capacity to predict and ameliorate the consequences of climate and land cover change depends, in part, on a clear description of SOC distributions and the controls of SOC inputs and outputs
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