Carbon stocks in the Guinea savanna of Ghana: estimates from three protected areas Ebenezer D. Djagbletey 1,2 , Vincent Logah 1,3 , Nana Ewusi-Mensah 1 , and Henry O. Tuffour 1 1 Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana 2 Forestry Commission, Cape Coast, Ghana ABSTRACT Savannas are widespread in sub-Saharan Africa (SSA) and play a major role in the global carbon balance. Extensive quantification of savanna carbon stocks in SSA will therefore contribute to better accounting of the global carbon budget in the era of climate change. In this study, we investigated the spatial distribution of carbon stocks of different soil fractions and aboveground biomass within three for- est reserves in the Guinea savanna zone of Ghana. Soil carbon stocks (SCSs) ranged from 4.80 to 12.61 Mg C/ha in surface soils (0– 10 cm depth). Higher SCSs were associated with the silt +clay fraction than microaggregates and small macroaggregates in all three reserves. Relative to the dominant tree species (Vitellaria paradoxa), the highest SCSs were recorded under the sub-canopy (SC), drip line (DL), and interspace (2 * SC + DL) zones for the Klupene, Sinsablegbinni, and Kenikeni forest reserves, respectively. The highest tree carbon stock was 60.01 Mg C/ha in Kenikeni. Sinsablegbinni had an average stock of 26.74 Mg C/ha and had the highest tree density. Average carbon capture by a single tree ranged from 0.04 to 0.34 Mg C. Aboveground grass carbon stock ranged from 0.08 to 0.47 Mg C/ha, while the belowground carbon stock ranged from 0.03 to 0.44 Mg C/ha. Accumulation of carbon in the aboveground grass biomass was greater at Klupene with low forest cover. Key words : aboveground biomass; belowground biomass; carbon stocks; forest reserves; Ghana; Guinea savanna; REDD+; soil fractions. SAVANNAS ARE WIDESPREAD IN SUB-SAHARAN AFRICA AND COVER AN APPRECIABLE AREA OF THE LANDMASS. Savannas span from the Sahel to the tropical rain forest, south and east of the Congo basin, and to the southwestern and western part of Madagascar (Loveland et al. 2001). The composition of savannas is often heterogeneous, being variously classified as woodlands, bushlands, and grasslands (Fisher et al. 2014). They come in a wide range of physiognomic types, which essentially reflect variations in tree cover and density (Sarmineto 1984). Due to their large extent and frequent burning, they influence water and carbon balances (Santos et al. 2004). According to Grace et al. (2006), savannas may be managed as sinks for carbon, primarily by protecting them from degradation and facilitating biomass accumulation over decades. This underscores the importance of maintaining forest reserves in the savannas (i.e., protected savannas). Studies on carbon stocks within forests and savannas in sub- Saharan Africa have tended to focus either on the soil or the aboveground carbon stocks, but rarely on both. For example, in the Congo basin, Chiti et al. (2017) evaluated the soil carbon stock of the Lope National Park in central Gabon with no emphasis on aboveground carbon stocks. Saiz et al. (2012) deter- mined soil carbon stocks along a precipitation gradient in West Africa (Ghana, Burkina Faso, Mali, etc.), but with no published information on the nature of aboveground stocks. The recent study by Qasim et al. (2016) in Burkina Faso on protected savanna was limited to only tree carbon stocks. Very few studies (e.g., Dintwe et al. 2014, Abaker et al. 2017) exist in SSA on both soil and tree carbon stocks. The semiarid and sub-humid regions of Africa have been suggested to have the largest potential for carbon sequestration in the world (Marks et al. 2009). However, there is a need for comprehensive datasets of soil carbon stocks and their distribu- tion, to allow for the development and validation of biogeochem- ical cycling models (Bird et al. 2001, Wynn et al. 2006). Although there is some knowledge of the soil carbon stocks in the SSA savanna, gaps still exist regarding the distribution of carbon within different pools (e.g., soil, tree, grass, and necromass) and the modulating effect of seasonality (climatic controls) on non- tree carbon stock dynamics. Such information is vital for the development of comprehensive national or regional carbon bud- gets to inform REDD + (Reducing Emissions from Deforestation and Forest Degradation) strategies, of which most countries in SSA are signatories. Financial mechanisms such as REDD + can provide an opportunity for SSA to alleviate poverty through con- servation of its forestry resources. However, carbon stock assess- ments are essential for this process (Qasim et al. 2016). Furthermore, the distribution of carbon in different soil fractions in savannas has been critically understudied in SSA. The objectives of this study were to (1) estimate carbon stocks among different ecosystem components within selected forest reserves in the Guinea savanna agro-ecological zone of Ghana; and (2) investigate the impact of climatic controls on grass carbon stock dynamics. We hypothesized that carbon stocks in forest reserves are mainly linked with tree density such that the reserve with the highest tree density would have the Received 19 June 2017; revision accepted 10 October 2017. 3 Corresponding author; e-mail: vlogah.canr@knust.edu.gh ª 2017 The Association for Tropical Biology and Conservation 1 BIOTROPICA 0(0): 1–9 2018 10.1111/btp.12529