Papers by Martin Yemefack
Australian Journal of Soil Research, 2008
Particulate organic matter (POM) status is a useful indicator to assess labile soil organic matte... more Particulate organic matter (POM) status is a useful indicator to assess labile soil organic matter (SOM) and to evaluate soil fertility under different agricultural systems, mainly in low-input agriculture as practiced in most of the sub-Saharan region of Africa. Total POM (53–4000 µm), different sized POM fraction characteristics (mass, C and N contents), and nutrient concentrations of soils were evaluated under 2 mixed food crop field types: a preceding forest fallow (forest) and a preceding fallow dominated by Chromolaena odorata (King & Robinson) (Chromolaena spp.) in the 0–0.10 m horizon of Rhodic Kandiudult, Typic Kandiudult, and Typic Kandiudox soils. The mass and C and N contents of total POM were higher in the Typic Kandiudox than in the Typic…
Depletion of soil fertility constitutes one of the most important constraints to sustainable agri... more Depletion of soil fertility constitutes one of the most important constraints to sustainable agricultural production, causing low per capita food production in Africa. Inappropriate soil fertility management, further increases loss of productivity of resource-poor farmers and affects their food security and livelihood. Large areas of most sub-Saharan African soils have low inherent fertility and do not receive adequate nutrient replenishment. Preserving soil fertility and enhancing productivity through appropriate soil management and conservation can play a major role in achieving farm household food security and agricultural development. This paper explores conceptual approaches to increasing food security and poverty alleviation in Africa through the replenishment of soil fertility as an investment in natural resource capital, and to outline the elements of strategies for its implementation. It highlights some successful experiences in the region, constraints and possible solution...
Although tree stems act as conduits for greenhouse gases (GHGs) produced in the soil, the magnitu... more Although tree stems act as conduits for greenhouse gases (GHGs) produced in the soil, the magnitudes of tree contributions to total (soil + stem) nitrous oxide (N 2 O) emissions from tropical rainforests on heavily weathered soils remain unknown. Moreover, soil GHG fluxes are largely understudied in African rainforests, and the effects of land-use change on these gases are identified as an important research gap in the global GHG budget. In this study, we quantified the changes in stem and soil N 2 O fluxes with forest conversion to cacao agroforestry. Stem and soil N 2 O fluxes were measured monthly for a year (2017-2018) in four replicate plots per land use at three sites across central and southern Cameroon. Tree stems consistently emitted N 2 O throughout the measurement period and were positively correlated with soil N 2 O fluxes. 15 N-isotope tracing from soil mineral N to stem-emitted 15 N 2 O and correlations between temporal patterns of stem N 2 O emissions, soil-air N 2 O concentration, soil N 2 O emissions and vapour pressure deficit suggest that N 2 O emitted by the stems originated predominantly from N 2 O produced in the soil. Forest conversion to extensively managed, mature (> 20 years old) cacao agroforestry had no effect on stem and soil N 2 O fluxes. The annual total N 2 O emissions were 1.55 ± 0.20 kg N ha −1 yr −1 from the forest and 1.15 ± 0.10 kg N ha −1 yr −1 from cacao agroforestry, with tree N 2 O emissions contributing 11 % to 38 % for forests and 8 % to 15 % for cacao agroforestry. These substantial contributions of tree stems to total N 2 O emissions highlight the importance of including tree-mediated fluxes in ecosystem GHG budgets. Taking into account that our study sites' biophysical characteristics represented two-thirds of the humid rainforests in the Congo Basin, we estimated a total N 2 O source strength for this region of 0.18 ± 0.05 Tg N 2 ON yr −1 .
Tropical Forests - The Challenges of Maintaining Ecosystem Services while Managing the Landscape, 2016
Council forests were officially enacted in Cameroon in 1994 as part of the forestry law reform. T... more Council forests were officially enacted in Cameroon in 1994 as part of the forestry law reform. The law provided rural councils with the legal right to create their own forests estate within the Permanent Forest Estate (PFE) of the State, following the preparation of a management plan approved by the forest administration. In this chapter, we analyze the socioeconomic and climate change mitigation potentials of these forests and propose possible options for improving their socioeconomic importance as well as their ability to mitigate climate change. Results indicate that Cameroon's council forests provide socioeconomic opportunities to communities in which they are located including employment and revenue from the sale of timber and nontimber forest products emanating from these forests. Additionally, given their diversity in terms of the various forest types (e.g., humid dense evergreen forests, humid dense semideciduous forests, and gallery forests), these forests have enormous carbon stocks which can provide huge opportunities for international climate initiatives such as the REDD+ mechanism to be initiated within them as a potential for mitigating global climate change. The chapter identifies and discusses possible options for improving the socioeconomic and climate change mitigation potential of these forests. Progress on the options the chapter opines, will help in improving the contributions of these forests to socioeconomic development and climate change mitigation.
Scientific Reports
Soil property and class maps for the continent of Africa were so far only available at very gener... more Soil property and class maps for the continent of Africa were so far only available at very generalised scales, with many countries not mapped at all. Thanks to an increasing quantity and availability of soil samples collected at field point locations by various government and/or NGO funded projects, it is now possible to produce detailed pan-African maps of soil nutrients, including micro-nutrients at fine spatial resolutions. In this paper we describe production of a 30 m resolution Soil Information System of the African continent using, to date, the most comprehensive compilation of soil samples ($$N \approx 150,000$$ N ≈ 150 , 000 ) and Earth Observation data. We produced predictions for soil pH, organic carbon (C) and total nitrogen (N), total carbon, effective Cation Exchange Capacity (eCEC), extractable—phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), sodium (Na), iron (Fe), zinc (Zn)—silt, clay and sand, stone content, bulk density and depth to bedroc...
CATENA, 2016
Estimation of the mineral resources potential is an important issue for most of developing countr... more Estimation of the mineral resources potential is an important issue for most of developing countries. The spatial distribution of lateritic landsurfaces and bauxite on the Bamiléké plateau (West Cameroon) has been investigated with a Boolean modeling process into a GIS environment on the basis of geological constraints namely elevation, rock types, landscape morphology and soil types. Field observation and SRTM (Shuttle Radar Topographic Mission) data allowed the differentiation of two lateritic surfaces separated by a minimum altitude difference of about 60 m. These surfaces constrained by favorable rock types, slope steepness and soil types provided a potential lateritic bauxitic area of 381 km² (17.2% of the total study site), which matches the current bauxitic areas and evidences a large non-explored area in the north of the study site. Field validation and the integration of legacy spatial data resulted in an area of 60.1 km² for potential bauxitic ores, i.e. obviously duricrusted landsurfaces (with 47.8 km² in the upper surface and 12.3 km² in the lower surface). Geochemical data (mostly Al 2 O 3 wt.%) obtained from duricrust samples were treated by geostatistical methods and classical kriging interpolation to discriminate between bauxitic and ferruginous laterites. This highlighted a geochemical trend from higher alumina values on the upper surface (40-66 wt.%) to lower values on the lower surface (13-44 wt.%). Finally, our study documents two indurated lateritic surfaces arranged in a staircase manner and having different geochemical characteristics. The total bauxitic-rich surface is distributed in five different spots throughout the study area and covers 56.2 km², while ferruginous laterites occupy a spot of 3.9 km². GIS mapping approach of lateritic landsurfaces, accounting for reliable constraints, might be promising for larger scale investigations of mineral resources in developing Countries.
Landscape distribution, macroscopic, microscopic, mineral and geochemical characterizations were ... more Landscape distribution, macroscopic, microscopic, mineral and geochemical characterizations were conducted on the Doumbouo-Fokoué bauxite ore deposit in order to estimate bauxites potential and its implication to general lowering of the relief. Fourteen bauxitic plateaus covering a surface area of 5.7 km 2 were identified. Bauxitic pedons show deep weathered profiles (10.0-12.0 m) with thick bauxitic mantle (4.0-8.0 m). Saprolite and pisolith bauxitic facies own high aluminium (47.5%-49.5% Al 2 O 3), relatively low iron (20.0%-22.0% Fe 2 O 3) and low silica contents (1.8%-7.6% SiO 2). Gibbsite is the dominant mineral (49%-68% of minerals detected by X-ray); meanwhile hematite, goethite and kaolinite occur in small amounts. Bauxitization corresponds to intense allitization with abundant accumulation of gibbsite and development of lateritic iron bearing ortho-bauxites. Bauxite ores yielded bauxite reserves of 9.2 million tons. They occur as old and residual bauxitic mantles representing remnants of the Miocene residual lateritic deposits in West Cameroon referring to the African surface of Valeton [1]. Its mean altitude (1532-1590 m als) below the African surface reveals general lowering of the relief.
International Journal of Biological and Chemical Sciences
Soil quality results from combination of chemical, physical and biological characteristics; accor... more Soil quality results from combination of chemical, physical and biological characteristics; according to ecosystems, some of these aspects become dominant. This Study was carried out on soils under 08 land cover types in the southern Cameroon ((bare soil with burned vegetation (FR1), bare soil with unburned vegetation (FR), Chromolaena odorata fallow (JC), bush ligneous fallow (JR), secondary forest (FS), primary forest (FC), Gilbertiodendron dewevei forest (FG), and raffia forest (RA) to assess the contributions of soil chemical and physical indicators into global soil quality index (IQSg). Topsoil samples were analyzed for physico-chemical characterizations and IQSg computed. Multiples statistical tests were used to compare the contribution of soil quality indicators and to select those that contributed the most in IQSg. Thus, under FR1, FC, FG and RA, IQSg was relatively high and the main contributors were chemical, estimated at more than 70%. Under FR, IQSg remains high and chemical contribution predominant (65%) on physical (35%). On the contrary, under fallows, IQSg is relatively low; these two types of contributions are nearly equivalents. Thus, the main indicators helping to assess IQSg in lower cost, contributing significantly to global soil quality and representatives of indicators are: organic matter (MO), pHw, and C/N ratio. The difference in contribution is due to the types of cultural practices, quality and quantity of MO brought by land cover types and topographical position.
Frontiers in Environmental Science
In the tropical rain forest zone of Southern Cameroon, shifting cultivation and perennial plantat... more In the tropical rain forest zone of Southern Cameroon, shifting cultivation and perennial plantations of cocoa are the main farming systems practiced by small-scale farmers to ensure subsistence food crop production and a small income. This research used scientific modeling tools to produce quantitative information on the evolution of soils under this shifting agricultural system. An analysis of farming system led to the development of a conceptual model of the spatio-temporal dynamics of shifting agriculture, including transition matrices of rotational cycles that guided the sampling strategy for the study of soil evolution under the system. The study of soil variability showed that 30-35% of the total variance of some topsoil (0-20 cm) properties was due to the influence of land use practices. Five soil properties (pH, calcium, available phosphorus, bulk density and organic carbon) that are the most sensitive to these agricultural practices were empirically modeled and linear/quadratic fractional rational functions were successfully fitted to time series soil variables to derive quantitative measures on temporal changes in soil with land use. Data and methods produced are useful for soil quality assessment and spatio-temporal dynamic simulation in order to guide decision-making for sustainable land-use planning and soil resources management.
Physicochemical of Rains in Southern Forest Cameroon. This paper is a contribution to the physico... more Physicochemical of Rains in Southern Forest Cameroon. This paper is a contribution to the physicochemical knowledge of the rains of the humid tropical forest area of Southern Cameroon. Rain water were sampled at Nsimi area in 2001/2002. The chemistry of rain waters can detect important atmospheric inputs under soluble form. The contents of major cations are relatively high (TZ+= 140 μeq/l). The major anions are less represented (TZ-= 51 μeq/l). Total dissolved salt (TDS= 5.76 mg/l) is above average characteristic of TDS (3.60 mg/l) of tropical region rain waters. The dissolved organic matter (COD= 1.20 mg/l) is low, but relatively high for the region. The levels of sodium and chloride ions are decreasing, reflecting their marine origin, while those for potassium and calcium increase. This increase and a significant correlation between these factors underline other potential sources. The bush fires and deforestation would make part of these sources that cause the change in atmospheri...
Journal of Food Agriculture and Environment
Entada abyssinica (Steud. ex A. Rich) is abundant and well recognized in the Ngaoundéré area of n... more Entada abyssinica (Steud. ex A. Rich) is abundant and well recognized in the Ngaoundéré area of northeast Adamawa Province, Cameroon, where swidden systems are practiced. Maize yield and soil chemical properties were analyzed from a two-factor block trial. The purpose was to determine the effects of E. abyssinica leaves used as green manure. The two factors were the amount of plant leaves applied and the application technique. Other than the two factors, the trial used current local farming methods. Maize yield showed significant increase when 2.50 kg cuttings were mixed with the soil, attributable to faster leaf decomposition and nutrient availability in the maize root zone. There was no significant increase in total nitrogen, available phosphorus, calcium or sodium in the 0-20 cm layer of soil. Mixing resulted in significant increases in soil organic matter, potassium and other soil fertility indicators. Higher quantities of the plant biomass significantly increased soil organic m...
A conceptual model of the spatio-temporal dynamics of Shifting Agricultural Systems (SAS) in the ... more A conceptual model of the spatio-temporal dynamics of Shifting Agricultural Systems (SAS) in the rainforest region of Southern Cameroon made it possible to identify five different cultivation cycles, which enabled the quantification of soil dynamics and carbon stocks. Carbon stocks in each pool were evaluated using all chronosequences for land use types, including Virgin forest (PF), Secondary forest (SF), Forest fallow (FF), Chromolaena fallow (CF), Mixed crop field (MC) and Old cocoa plantations (OCP). Under each treatment, biomass measures were conducted on trees, undergrowth, litter and plant roots. Soil samples were analysed for physicochemical determinations. The total carbon (in TC/ha -1) varies in the following decreasing order: VF (305), SF (251), OCP (184), FF (180), CF (101), and MC (67). Although the average soil carbon stock represents 93% and 78% under the MC and CF systems, respectively, it represents only 26% of total carbon for the VF system. When a PF system is con...
British Journal of Mathematics & Computer Science, 2014
Food industry is currently focusing on fast and unsupervised quality inspection techniques. This ... more Food industry is currently focusing on fast and unsupervised quality inspection techniques. This paper deals with the development of new method for fast quality control of bag packaging red beans (Phaseolus vulgaris) using flatbed scanning. The proposed method combines fuzzy c means with spatial transformation (FCM_ST) to reduce FCM iteration. We used the labelled pixel, in the clustering image, for the evaluation of grain mixture in acquired image. The performance of the FCM_ST was compared to the standard FCM approach and it reveals itself very good for fast clustering and efficient detection of grain mixture. The detections accuracies of grain mixture in the bag packaging red beans (Phaseolus vulgaris) was 96% for acquired image with presence of other self-colour commercial beans type, 70% with presence of defected cotyledons beans, between 30% to 89% with presence of multi-coloured beans depending on their texture and between 10% to 15% with the presence of low discoloured red beans of same commercial type.
Résumé La ferme PROLEG de Foumbot, spécialisée dans la culture des légumes verts, est établie sur... more Résumé La ferme PROLEG de Foumbot, spécialisée dans la culture des légumes verts, est établie sur un Andosol Leptique. Malgré des pratiques culturales identiques sur toute son étendue, on note une disparité dans le rendement en maïs et en haricot vert des trois principales parties de celle-ci. Une étude de la variabilité spatiale de la fertilité du sol a été entreprise dans le but d'identifier les causes de la disparité du rendement parcellaire. L'objectif de cette étude était d'inventorier et d'évaluer les facteurs de la variabilité des caractéristiques des sols à l'intérieur de cette ferme, à travers une étude pédologique détaillée et une analyse spatiale de la distribution de certains facteurs de la productivité des sols. Il en résulte que bien que la fertilité chimique des sols sur roches volcaniques soit reconnue, d'autres caractéris-tiques des sols peuvent influencer de manière notable la fertilité globale de ces sols. Il s'agit pour le cas présent ...
In order to investigate the effect of short rotation Desmodium distortum planted fallow on maize ... more In order to investigate the effect of short rotation Desmodium distortum planted fallow on maize grain yield and soil properties, an experiment was conducted over four consecutive years (1995-1998) at two locations (Minkoameyos in the humid forest zone and Ntui in the forest-savannah transition zone) in Centre Cameroon. The experimental design for each year was made of four replications and three treatments: i) Natural Fallow used as control (NF), ii) Desmodium Fallow (DF) and iii) Soybean (Glycine max) Rotation (SR). Maize (Zea mays) was used as plant test and was planted each year in the first cropping season (March-June) followed by each treatment from July to February. The analysis of variance and mean separation (Tukey's HSD) were used to evaluate the effects of treatments on maize yield and soil chemical properties at the end of the experiment. No treatment could produce relatively more than the first year of the experiment where maize yields were based on 7-8 year-old nat...
Applying the current government strategy of cocoa farms extension for rural development in the Ef... more Applying the current government strategy of cocoa farms extension for rural development in the Efoulan Municipality with a population of 25000 people, 5000 ha of land that would consequently have been converted into cocoa farms by this population, can potentially increase the CO 2 emission between 2012 and 2016 by 4 million tons. • The current observed cocoa farm and crop field expansion (145 ha/yr and 45 ha/yr respectively) is happening at the expense of primary forest clearance (194 ha/yr). • However, opportunities for reducing or stabilizing emissions from land use conversions exist: 1) for cocoa farms, intensification using inputs and tree planting is considered vital; 2) for forested areas, sustainable forest management practices such as reduced impact logging and replanting of logged areas could help tremendously. • The long-term emission simulation showed that extension of cocoa farms will continue to be the major source of CO 2 emission in the landscape in the next two decad...
This report explores key elements required to support a whole landscape approach for carbon accou... more This report explores key elements required to support a whole landscape approach for carbon accounting in Cameroon – to Reduce Emissions from All Land Uses (REALU). A REALU approach requires integrating a cross-sectoral discourse into the debate about Reducing Emissions from Deforestation and forest Degradation (REDD+). Cross-sectoral issues in Cameroon include: the understanding of the main dynamics in the forest and agricultural sector; the direct and underlying causes and actors of deforestation and land use change in the humid forest zone; and the policy framework ruling the forest sector and the implementation of the 1994 Forest Code principles. Additional issues that cut across the land-use sector include the rights to resources, tenure and potential conflicts on land and forest resources concerning REDD+, and opportunities for on-farm timber production.
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Papers by Martin Yemefack