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.
Tag: Carbon sequestration
N cycling increase after savanna afforestation with Eucalyptus or Acacia is reflected in the growth of soil ammonia-oxidizing archaea and nematode bacterial-feeders
In tropical humid Africa, sandy soils in herbaceous savannas—often exposed to periodic burning—typically exhibit low carbon (C) content and nitrogen (N) availability. Savanna afforestation has the potential to improve soil functionality, but its effects remain underexplored. This study examines whether changes in soil micro-food web composition contribute to increased C and N cycling following afforestation. A 7-year experiment in Congo assessed Eucalyptus monocultures, N₂-fixing Acacia monocultures, and mixed Eucalyptus-Acacia plantations on former savanna landscapes. Soil attributes analyzed included organic C and N levels, pHH₂O, nitrate, ammonium, mineralization and nitrification rates, as well as bacteria, fungi, nematodes, and ammonia-oxidizing archaea (AOA) and bacteria (AOB) abundances in the top 10 cm of soil. Afforestation with Eucalyptus monocultures increased soil carbon by 1.7 times, net nitrogen mineralization rates by 1.9 times, and soil inorganic nitrogen levels by 2.5 times. Mixed Eucalyptus-Acacia and Acacia monocultures further enhanced nitrogen mineralization by 1.4 times and inorganic nitrogen by 2.3 times compared to Eucalyptus monocultures. These changes correlated with a progressive increase in AOA abundance, peaking in Acacia monocultures. Additionally, afforestation significantly boosted bacterial-feeding nematode abundance by 678%, while fungal-feeders, omnivores, and predators declined. Enhanced nitrogen cycling was positively linked to AOA and bacterial-feeding nematode abundances, emphasizing the necessity of monitoring micro-food web structures to better understand how land use changes shape soil biogeochemical cycles in tropical afforestation contexts.
Conversion of degraded forests to oil palm plantations in the Peruvian Amazonia: Shifts in soil and ecosystem-level greenhouse gas fluxes
The expansion of oil palm (OP) plantations and associated forest clearance can significantly impact greenhouse gas (GHG) fluxes. This study examined carbon stocks and soil GHG emissions (N₂O, CO₂, CH₄) in a degraded forest and a neighboring 17-year-old OP plantation in Peruvian Amazonia, where three nitrogen (N) fertilizer treatments were applied: 0 kg (OPN0), 84 kg (OPN1), and 168 kg (OPN2) per hectare per year. Carbon stocks were measured across different pools, and GHG fluxes and environmental parameters were monitored monthly over 11 months and (bi)daily during fertilizer application, with measurements taken near and far from trees/palms. Ecosystem-scale CO₂ equivalent losses were calculated by balancing carbon stock losses against N₂O emission changes. Findings showed that: (1) N₂O emissions (kg N ha⁻¹ y⁻¹) were highest in the degraded forest (6.7 ± 1.2), where litterfall N inputs were substantial (213 kg N ha⁻¹ y⁻¹). Emissions in OP plantations were significantly lower: OPN0 (0.6 ± 0.2), OPN1 (1.4 ± 0.2), OPN2 (2.3 ± 0.3). (2) Soil respiration (Mg C ha⁻¹ y⁻¹) was 1.4 times higher in the forest (9.1 ± 0.6) compared to OP plantation treatments (OPN0: 7.3 ± 1, OPN1: 5.5 ± 0.5, OPN2: 6.5 ± 0.3). (3) The forest acted as a CH₄ sink (-1.5 ± 0.3 kg C ha⁻¹ y⁻¹), whereas all OP treatments were sources (OPN0: 0.2 ± 0.3, OPN1: 0.7 ± 0.5, OPN2: 0.2 ± 0.4). (4) Carbon stock losses from forest-to-OP conversion were significant (196.8 ± 44.0 Mg CO₂ ha⁻¹ over 15 years) but were partially offset (14–20%) by reduced N₂O emissions. These findings highlight the complex GHG trade-offs associated with OP expansion, reinforcing the need for complementary studies to enhance global GHG assessments.
Nutritional Diversity in Native Germplasm of Maize Collected From Three Different Fragile Ecosystems of India
Native maize germplasm is uniquely adapted to specific ecological niches, having been preserved over generations due to local communities’ preference for their distinct taste, culinary utility, and low cultivation costs. These varieties hold promise for addressing malnutrition and serve as valuable genetic resources for trait-linked improvements. This study examines thirty-three native maize germplasm collected from Rajasthan, Himachal Pradesh, and Andhra Pradesh, spanning altitudes from 386 to 2,028 meters. Their nutritional profiles—including moisture (7.16–10.9%), ash (0.73–1.93%), crude protein (8.68–12.0%), crude fat (3.72–8.03%), dietary fiber (5.21–11.2%), and available carbohydrates (60.6–69.8%)—were compared against the Indian Food Composition Table 2017 (IFCT2017). Notably, three accessions—Malan 11 (7.06%), Malan 24 (7.20%), and Yellow Chamba Local 02 (8.03%)—exhibited nearly double the crude fat content reported in IFCT2017 (3.77%). Additionally, all germplasm except Yellow Chamba Local demonstrated higher protein levels than IFCT2017 values, with Sathi, Safed Chamba Local, and Ragal Makka reaching nearly 12%. Iron deficiency remains a global concern, and this study found that several germplasm contained iron levels nearly three times higher than IFCT2017 values. A negative correlation was observed between altitude and available carbohydrate content, while dietary fiber, protein, and fat showed inverse relationships with carbohydrate availability. These findings underscore the potential of native maize germplasm for nutritional enhancement, food labeling, and crop improvement initiatives.
Séquestration du carbone et provision d’autres services écosystémiques des parcs agroforestiers à karité au Burkina Faso [Carbon sequestration and other ecosystem services provided by shea-tree agroforestry parks in Burkina Faso]
Shea-tree agroforestry parks play a crucial role in climate mitigation and ecosystem services in West Africa, yet their carbon sequestration potential remains poorly documented. This study assesses the contribution of shea-tree (Vitellaria paradoxa) agroforestry parks in Burkina Faso, using household surveys and field inventories across three phytogeographical sectors. Findings indicate that over 89% of surveyed households have shea trees in their fields, which provide fuelwood, timber, improve soil fertility, and help control erosion. Tree density varies from 32 to 45 individuals per hectare, with an average height of 7.93 meters and a diameter at breast height (DBH) of 31.9 cm. Above-ground biomass estimates range from 15.5 to 42.8 Mg/ha, averaging 25.7 Mg/ha or 12.8 Mg of carbon per hectare. The study highlights the significant carbon sequestration potential of these agroforestry systems, though benefits vary based on tree DBH and regional factors. Notably, all surveyed trees had a DBH greater than 24 cm, indicating a lack of young trees and an urgent need for regeneration through assisted natural regeneration, planting, or a combination of both.
Assessing conditions to scale up private investment in forest restoration
Forest restoration (FR) in low- and middle-income countries (LMICs) requires private investment. We estimated the area of degraded forestland with investment conditions favoring private FR in 115 LMICs. We examined a base scenario, with FR driven by wood markets and influenced by seven investment conditions, and a “natural climate solutions” (NCS) scenario, with FR driven by carbon markets and influenced by six conditions. We have found that barely half of the restorable area in the base scenario, and barely a third in the NCS scenario, has at least four favorable investment conditions (i.e., at least half of the total number). In both scenarios, less than 1% of the restorable area has all conditions favorable. Locations with more favorable conditions tend to have greater potential to generate local livelihood benefits than global carbon or biodiversity benefits. Of the 59 LMICs that have made national commitments to restore forestland under the Bonn Challenge, which has a global goal to restore 350 million hectares by 2030, more than half have made a commitment whose area exceeds our estimate of the country’s restorable area with at least four favorable investment conditions. This discrepancy implies that those countries cannot rely solely on private investment to achieve their commitments. Scaling up private FR in LMICs requires coordinated public-sector investments and policy interventions to improve investment conditions and ensure that private FR generates both local and global environmental benefits.
Species-Poor Mangrove Forests also Provide Rich Ecosystem Goods and Services
Mangrove forests provide a wide range of services to coastal communities worldwide. These services include carbon sequestration and coastal protection, both of which are critical in the context of climate change. However, these wetlands are still experiencing destructive anthropogenic impacts in many areas. Senegal and Colombia, two countries in the Atlantic-East Pacific biogeographic region, both have abundant mangrove cover and share several mangrove species. This study assessed the use of mangrove resources (fuelwood, timber, and other non-timber forest products) by local communities in both countries. A total of 210 semi-structured ethnobotanical questionnaire-based interviews were conducted in Sokone and neighboring villages bordering the Sine-Saloum Delta in Senegal (110) and in the Cispata lagoon system in Colombia (100). The results for Senegal indicate that individuals residing near the Sine-Saloum Delta in neighboring villages rely more on mangroves compared to those living in Sokone. In Colombia, reliance on mangroves was associated with occupational activities. Despite lower species diversity compared to the Indo-West Pacific biogeographic region, mangroves provide various services in both areas, underscoring their significance to local communities and their livelihoods. Finally, the Indigenous and local knowledge emphasizes the need for alternatives to mangrove resources and the promotion of sustainable harvesting practices to ensure the conservation of mangroves and the continued provision of essential services.
Pulpwood plantations as carbon sinks in Indonesia: methodological challenge and impact on livelihoods
The Clean Development Mechanism (CDM) was created under the Kyoto Protocol, in order to help industrialized countries achieve their Greenhouse Gas (GHG) emission reduction targets at a lower cost. A second objective of the CDM is to help developing countries achieve sustainable development. To become eligible these projects have to demonstrate their additionality, and have a positive impact on local communities’ livelihoods. But the methodologies that have been proposed seem unsatisfactory, and the social impacts are often debated. This paper provides new insights on these methodologies, their weaknesses and potential improvements, and explores the social impacts of an afforestation/reforestation CDM activity with a high carbon sequestration potential. We studied a large-scale pulpwood plantation in Indonesia, which is perceived as a way to sequestrate great quantities of carbon in a short time, and as an alternative to natural forest supplies for the domestic pulp industry. We collected complete data on the establishment and production costs, and the carbon sequestration potential. We also took advantage of our ongoing research on the Indonesian Pulp & Paper (P&P) sector to interpret these results, and evaluate the relevance of widely used and proposed methodologies for additionality assessment. Finally, research on site allowed us to obtain data on the plantation’s impact on the people living nearby. According to our research, fast-growing tree plantations face production costs far higher than revenues gained from the sale of carbon credits, even with a relatively important carbon sequestration. But calculations made according to usual methodologies can be misleading. We show that context analysis is more relevant, and that profitability calculations lead to wrong conclusions. From a social point of view, pulpwood plantation projects could increase livelihoods in the short term, but this depends very much on the opportunities for locals to combine employment in the plantation with land uses generating higher incomes per hectare.
A review of organic inputs to inform soil health advice for African smallholder farmers: localization matters
African smallholder farming systems are complex, diverse and locally adapted, but guidance is lacking on how farmers can make informed choices of the type of organic inputs to suit their farm conditions. In this review we aimed to provide a synthesis of actionable information on ex situ and in situ organic resources and decision support tools to facilitate evidence-based choices by smallholders in cereal production systems in sub-Saharan Africa.