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Contribution of forest-derived C (FDC) and savanna-derived C (SDC) to the total SOC stock in each layer of the colonising forest (CF), Marantaceae forest (MF) and mixed Marantaceae forest (MMF) stages
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In this study, we quantified the contribution of forest-derived carbon (FDC) to the soil organic C (SOC) pool along a natural succession from savanna (S) to mixed Marantaceae forest (MMF) in the Lopè National Park, Gabon. Four 1-ha plots, corresponding to different stages along the natural succession, were used to determine the SOC stock and soil C...
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Citations
... Forest succession after disturbance is a naturally occurring process of plant community replacement, which has highly important implications for ecological restoration, plant diversity, and ecosystem functioning as well as climate change mitigation [23][24][25]. Natural succession usually facilitates an increase in SOC, especially in tropical regions [26,27]. Accumulation rates of SOC are known to vary across the stages of forest succession [28][29][30]. ...
Plants and microbes are the primary drivers in affecting the formation and accrual of soil organic carbon (SOC) for natural ecosystems. However, experimental evidence elucidating their underlying mechanisms for SOC accumulation remains elusive. Here, we quantified plant and microbial contributions to SOC accrual in successional subtropical forests by measuring leaf-, root-, and microbial biomarkers, root and leaf litter inputs, and microbial C decomposition. The long-term monitoring results showed that SOC accumulated rapidly at the early-successional stage, but changed little at the mid- and late-successional stages. SOC accrual rate was positively correlated with fine-root production and microbial C turnover, but negatively with annual litterfall. Biomarker data exhibited that the rapid SOC accumulation was jointly driven by root- and microbe-derived C inputs from the early- to mid-successional stages. In contrast, aboveground litterfall considerably contributed to soil C accrual from the mid- to late-successional stages compared to belowground processes, although SOC accumulation is low. Our study revealed the importance of root production and microbial anabolism in SOC accrual at the early stages of forest succession. Incorporating these effects of belowground C inputs on SOC formation and accumulation into earth system models might improve model performance and projection of long-term soil C dynamics.
... Local factors including fire management, soil fertility or hydromorphy and herbivory pressure are expected to mediate this general prediction. Although carbon mitigation programs such as REDD + scheme tend to encourage forest expansion, the loss of savanna ecosystems in the area will drastically modify landscape-level diversity (Bond, 2016;Veldman, 2016) and ecosystem services, including hydrology (Acharya et al., 2018) and soil nutrient cycles (Berthrong et al., 2009), including soil carbon storage (Chiti et al., 2018;Cuni-Sanchez et al., 2016), and it would markedly alter community assemblages (Abreu et al., 2017;Bremer and Farley, 2010) especially those of savanna plant and animal specialists, including iconic large mammals and big cats. That is the reason why park authorities should aim at maintaining the mosaic of forest and humid savannas that pre-existed gazetting of the protected areas they are in charge of (Jeffery et al., 2014). ...
Woody encroachment and forest progression are widespread in forest-savanna transitional areas in Central Africa. Quantifying these dynamics and understanding their drivers at relevant spatial scales has long been a challenge. Recent progress in open access imagery sources with improved spatial, spectral and temporal resolution combined with cloud computing resources, and the advent of relatively cheap solutions to deploy laser sensors in the field, have transformed this domain of study. We present a study case in the Mpem & Djim National Park (MDNP), a 1,000 km² protected area in the Centre region of Cameroon. Using open source algorithms in Google Earth Engine (GEE), we characterized vegetation dynamics and the fire regime based on Landsat multispectral imagery archive (1975–2020). Current species assemblages were estimated from Sentinel 2 imagery and the open source biodivMapR package, using spectral dissimilarity. Vegetation structure (aboveground biomass; AGB) was characterized using Unmanned Aerial vehicle (UAV) LiDAR scanning data sampled over the study area. Savanna vegetation, which was initially dominant in the MDNP, lost about 50% of its initial cover in <50 years in favor of forest at an average rate of ca. 0.63%.year⁻¹ (6 km².year⁻¹). Species assemblage computed from spectral dissimilarity in forest vegetation followed a successional gradient consistent with forest age. AGB accumulation rate was 3.2 Mg.ha⁻¹.year⁻¹ after 42 years of forest encroachment. In savannas, two modes could be identified along the gradient of spectral species assemblage, corresponding to distinct AGB levels, where woody savannas with low fire frequency store 40% more AGB than open grassy savannas with high fire frequency. A fire occurrence every five year was found to be the fire regime threshold below which woody savannas start to dominate over grassy ones. A fire frequency below that threshold opens the way to young forest transitions. These results have implications for carbon sequestration and biodiversity conservation policies. Maintaining savanna ecosystems in the region would require active management actions to limit woody encroachment and forest progression, in contradiction with global reforestation goals.
... The Lopé National Park in Gabon, listed as a UNESCO World Heritage site in 2007 both for its environmental and cultural heritage, plays a major role in understanding western Central African prehistory as the long history of research in this area has established palaeoenvironmental, chronological and cultural sequences (e.g. Assoko Ndong, 2003;Chiti et al., 2018;de Bayle des Hermens et al., 1987;Henga-Botsikabobe et al., 2020;Jeffery et al., 2014;Moumaneix and Nkombe, 2017;Nfoumou et al., 2017;Obiang Mba, 2020;Oslisly, 2016;1998;Oslisly et al., 2013;Peyrot et al., 2003;Saulieu et al., 2018;Sebag et al., 2016;White, 2001). The park extends from the equator to the northern foothills of the Chaillu Mountains and covers the middle part of the Ogooué Basin, a river of 1080 km flowing east to west, from the Ntale Mountains in the Republic of Congo to near Port-Gentil in Gabon. ...
In Central Africa, Late Stone Age (LSA) seems to emerge before the Late Glacial Maximum (LGM) usually associated to a fluctuating savanna expansion and forest cover reduction. However, few sites with a reliable chrono-stratigraphic context allow us to deal with the emergence, the diffusion and the specificities of the regional lithic assemblages associated to the Late Stone Age. The site of Mabou´e 5, located in the Lop´e National
Park in Gabon provided useful lithic corpus to consider these questions. This paper provides a detailed technological analysis of the Layer 3 dated between 44 600 and 14 770 cal. BP. We consider both the production patterns of the entire assemblage and the morpho-structural characteristics of the tools. Our results exhibit a lithic assemblage associating both Middle and Late Stone Age technological patterns and argue for regional technological variability among early LSA quartz assemblages. Finally, we highlight the specificities of quartz lithic industry of a site in the poorly documented region of western Central Africa and we question the validity of the regional nomenclature, namely the Tshitolian and Lupemban facies, to classify this final Late Pleistocene lithic assemblage.
Elevating levels of atmospheric carbon dioxide (CO2), primarily driven by the burning of fossil fuels, combustion of organic matter, and unsustainable land practices, have amplified global concerns regarding climate change. The industrial revolution has propelled the rise in CO2 emissions, leading to anticipated increases in concentrations and alterations in CO2 sequestration within agricultural soils. Land use alterations, encompassing deforestation, biomass burning, changes in agricultural conditions, drainage of natural wetlands, and incorrect soil management practices, have further amplified these emissions. Moreover, the reduction of soil organic carbon (SOC), an outcome of soil degradation and mismanagement, has intensified atmospheric CO2 levels. However, by implementing state-of-the-art land application and contemporary management systems in agriculture, there’s potential to slow the rate of CO2 emissions. The restoration of depleted SOC is possible through various strategies, such as converting marginal lands into restorative uses, promoting reduced or zero-tillage practices combined with cover or residue crops, and implementing nutrient cycling via composting, manure application, and other sustainable soil and water management techniques. Long-term soil carbon sequestration is increasingly being viewed as a comprehensive strategy to combat climate change. By rejuvenating depleted soils, enhancing biomass production, purifying surface and groundwater, and offsetting CO2 emissions from fossil
fuels, soil carbon sequestration can serve as a holistic and effective approach for mitigating current climatic changes. Adoption of these innovative techniques is crucial in managing the challenges imposed by recent environmental changes, positioning soil carbon sequestration as a promising solution. This review aims to
explore the potential methods of mitigating climate change through the implementation of soil carbon sequestration strategies
Aim
The mosaic of savannas that persists in the forest‐dominant Congo Basin is thought to be palaeoclimatic relics, but past biogeographical processes that have formed and maintained these systems are poorly understood. Here, we explored the post‐Pleistocene biogeography of Gabon's savannas using termites as biological indicators to understand historical and mechanistic factors influencing present‐day termite communities in the country's extant savannas.
Location
Gabon, Central Africa.
Taxon
Blattodea: Termitoidae.
Methods
Using standardised transect methods, we sampled termite communities in four disjunct modern savanna areas of Gabon: the centre (Lopé), the southeast (Batéké) and the south (Mayombe North and South). Termites at Lopé were collected in three habitats (annually burned savannas, savannas with a depressed fire regime and forest). We used DNA barcoding of the COII region to identify termite species and compared abundance, species richness and community composition across areas and habitats.
Results
Community composition differed greatly between Lopé and both Batéké and Mayombe savannas with Lopé being exceptionally depauperate and lacking characteristic savanna species. Within Lopé, termite abundance and diversity was highest in forests and lowest in annually burned savannas, with a gradual change in species composition across the forest–savanna gradient associated with fire history.
Main Conclusions
The absence of savanna typical species in Lopé savannas challenges current assumptions that these savannas were linked to the south/southeastern savannas during the Pleistocene and suggests a different evolutionary history. Lopé savannas may instead have opened as an isolated grassland and never have been contiguous with neighbouring savannas, or were isolated soon after forest expansion began and have now lost savanna‐typical species. Furthermore, the patterns of termite community composition in fire suppressed savannas support a hypothesis of rapid change driven by fire frequency where either fire suppression or infrequent burning over 23 years has meant savannas have become ecologically much more forest‐like.
