Peatlands are among the most concentrated terrestrial carbon stores, containing about 644 GtC, or 21% of global soil organic carbon (SOC). This is nearly double the carbon stored in all forest biomass worldwide. Despite covering only 3% of Earth’s land surface, peatlands are critical carbon reservoirs, mainly located in boreal and temperate regions, with smaller areas in the tropics. When drained for agriculture or other land uses, peatlands release large amounts of CO₂ and N₂O due to microbial decomposition. Current degraded and cultivated peatlands are projected to cumulatively emit 80.8 Gt of carbon and 2.3 Gt of nitrogen over the coming centuries, equivalent to contemporary annual emissions of 1.91 (0.31–3.38) GtCO₂e. Protecting peatlands is therefore vital for climate mitigation.
Tag: Soil organic carbon
Mapping soil organic carbon as soil health indicator of cocoa landscapes in middle Côte d’Ivoire
The spatial distribution of soil organic carbon (SOC) in cocoa-growing landscapes is a vital indicator of soil health and essential for environmental management. However, documented work on the mapping of SOC is often unavailable for such landscape. At the same time, spatial information is required for specific soil fertility management and the implementation of knowledge-based policies that aim at increasing cocoa production. This study aimed to establish baseline SOC maps in cocoa-growing landscape for topsoil (0–20 cm) and subsoil (20–50 cm) and investigate underlying factors for its spatial distribution using a digital soil mapping approach. For that purpose, two variants of the Random Forest algorithm were used, considering the normal random cross-validation (random CV) and the Leave-Location-Out cross-validation (LLOCV), which accounts for spatial autocorrelation. Our findings revealed that SOC content was better predicted by considering LLOCV compared to random CV. The spatial variability of SOC content was primarily related to elevation at all depths, with areas with more natural vegetation located at high altitude having higher SOC content than lower regions. However, both methods indicate that SOC content in the studied cocoa-growing landscapes is less than 2 %, which is below the standard required for supporting a sustainable cocoa production. These results put forward the need to increase the awareness among all cocoa stakeholders and policymakers towards actions that promote the building up of soil organic matter as a cost-effective way to boost productivity.
Spectroscopic solutions for generating new global soil information
Soil spectroscopy offers a rapid, cost-effective method for analyzing soil properties critical to sustainable land management. This study, led by the FAO’s Global Soil Partnership through the Global Soil Laboratory Network’s spectroscopy initiative (GLOSOLAN-Spec), presents a global framework to advance soil spectroscopy adoption. It identifies seven key challenges and proposes collaborative solutions to harmonize methods, build spectral libraries, and integrate local knowledge. Using spectroscopy in the visible and mid-infrared ranges, the method enables accurate estimation of soil properties like organic carbon, pH, and texture. The study emphasizes the need for international cooperation and standardized protocols to unlock the full potential of digital soil information for evidence-based decision-making.
Effects of landscape attributes on the spatial distribution of soil organic carbon stocks in smallholder farming systems in Cameroon
Soil organic carbon (SOC) is important in maintaining soil quality, fertility, and the terrestrial carbon cycle. Advances in technology have heightened global interest in estimating soil carbon sequestration. Assessing SOC stocks at landscape scales faces significant challenges, particularly in mosaic landscape influenced by anthropogenic and environmental factors. These challenges include the limited availability of high-resolution soil data, the high cost and labor intensity of soil sampling, and the difficulty of accurately representing soil heterogeneity using conventional sampling methods. This study investigates the influence of key landscape attributes including soil depth, land use type, slope gradient, and topographic position on SOC stock distribution and associated soil properties at 0 – 20 cm (topsoil) and 20 – 50 cm (subsoil) in the highlands of Cameroon. A total of 320 soil samples collected from a 100 km2 site were analysed in the laboratory. Results reveal that soil depth, land use type, and topographic position influence the distribution of SOC, bulk density (BD), and SOC stocks. Land use and topographic positions interactions significantly impact SOC, coarse fraction (CF), and SOC stocks, reflecting varied human activities and environmental effects across topographic locations. Total SOC stocks for the site are estimated at 37,571 tons C/ha in topsoil and 57,341 tons C/ha in the subsoil, totalling 94,912 tons C/ha of carbon to a depth of 50 cm. Kriging maps demonstrate a decreasing trend in SOC stocks from west to east, with higher values in lowlands characterized by lower BD and CF, and lower values in mountainous areas. These findings advance SOC stocks evaluation in the highlands of Cameroon, providing a foundational reference for future assessments to guide landscape restoration initiatives in ecologically fragile ecosystems.
Recovery of aboveground biomass, soil carbon stocks and species diversity in tropical montane secondary forests of East Africa
Tropical montane forests are fragile ecosystems that provide a wide range of ecosystem services including hydrological services, biodiversity protection and storing carbon in the above and belowground and soils contributing to climate change mitigation. The world’s tropical montane forests are increasingly exposed to degradation and their recovery after disturbance has not been adequately quantified. Here, using information from 47 plots in three blocks of the Mau Forest Complex of Kenya, we assessed the changes in aboveground biomass (AGB), tree species diversity, soil carbon and nitrogen stocks following forest clearance. AGB recovered at an annual rate of 6.42 Mg ha−1 yr−1 in the first 20 years, the rate then slowed down to 4.46–4.67 Mg ha−1 yr−1 at around 25–30 years. Around 25 years after disturbance, AGB in recovering forests was 70 % (198.32 ± 78.11 Mg ha−1) of the AGB in the old secondary forest (OSF) (282.86 ± 71.64 Mg ha−1) and was statistically indistinguishable. Stem density, species diversity and richness indices did not show significant differences across recovery classes. There was no significant difference in soil carbon and nitrogen stocks across classes with the soil carbon (184.1 ± 41 Mg ha−1) of the young secondary forest (<10 years) being 84.5 % of that of the OSF (217.9 ± 51.8 Mg ha−1). This study reports a rapid rate of AGB and carbon accumulation within 20 years of disturbance, and high levels of species richness in these previously disturbed fragments of tropical montane forests of East Africa.
Soil Organic Carbon and Nitrogen in Agroforestry Systems in Sub-Saharan Africa: A Review
Managing soil organic carbon in grazing lands in Africa
Grazing lands contain large amount of soil organic carbon (SOC) making them important to mitigate climate change, improve water infiltration and storage, improve nutrient cycling, increase land productivity and increase below and potentially above ground biodiversity, hence improving livelihoods. The key determinants of SOC sequestration potential in grazing lands in SSA are climate (rainfall amount and regime) and soil type. In general, it can be said that (i) mesic environments sustained grazing pressure is likely to lead to land degradation (and therefore may cause SOC to decrease) and 2) in dry areas with high rainfall variability, land degradation from sustained grazing may not be as apparent as grazing effects are overridden by rainfall effects. We found no significant differences in SOC following two decades of annual prescribed burning in Burkina Faso and three decades of avoiding livestock grazing management in Ethiopia. There may be instances in which there are large social costs to SOC sequestration and by making sequestration the primary goal, a situation could arise where the social or economic burdens of the project could be greater than the climate change mitigation benefits. Therefore, we recommend that SOC sequestration for climate change mitigation should be treated as a co-benefit rather than the target of a project/ activity. Projects also need to prioritize to avoid grazing land degradation and SOC losses in dry grazing lands which have less carbon sequestration potentials. Gaps in our understanding of the determinants of SOC sequestration potential were further discussed and general recommendations for future projects and other activities addressing SOC sequestration in grazing lands highlighted.
Enhancing tree tomato production for smallholder farmers’ income generation and improved nutrition in Bugesera and Gishwati in Rwanda
Early-spring soil warming partially offsets the enhancement of alpine grassland aboveground productivity induced by warmer growing seasons on the Qinghai-Tibetan Plateau
Agro-ecological options for fall armyworm (Spodoptera frugiperda JE Smith) management: Providing low-cost, smallholder friendly solutions to an invasive pest
Fall armyworm (FAW), a voracious agricultural pest native to North and South America, was first detected on the African continent in 2016 and has subsequently spread throughout the continent and across Asia. It has been predicted that FAW could cause up to $US13 billion per annum in crop losses throughout sub-Saharan Africa, thereby threatening the livelihoods of millions of poor farmers. In their haste to respond to FAW governments may promote indiscriminate use of chemical pesticides which, aside from human health and environmental risks, could undermine smallholder pest management strategies that depend to a large degree on natural enemies. Agro-ecological approaches offer culturally appropriate low-cost pest control strategies that can be readily integrated into existing efforts to improve smallholder incomes and resilience through sustainable intensification. Such approaches should therefore be promoted as a core component of integrated pest management (IPM) programmes for FAW in combination with crop breeding for pest resistance, classical biological control and selective use of safe pesticides. Nonetheless, the suitability of agro-ecological measures for reducing FAW densities and impact need to be carefully assessed across varied environmental and socio-economic conditions before they can be proposed for wide-scale implementation. To support this process, we review evidence for the efficacy of potential agro-ecological measures for controlling FAW and other pests, consider the associated risks, and draw attention to critical knowledge gaps. The evidence indicates that several measures can be adopted immediately. These include (i) sustainable soil fertility management, especially measures that maintain or restore soil organic carbon; (ii) intercropping with appropriately selected companion plants; and (iii) diversifying the farm environment through management of (semi)natural habitats at multiple spatial scales. Nevertheless, we recommend embedding trials into upscaling programmes so that the costs and benefits of these interventions may be determined across the diverse biophysical and socio-economic contexts that are found in the invaded range.