Effet de la mise en culture des forêts secondaires sur les peuplements de macroinvertébrés du sol dans la zone de contact forêt-savane de Côte d'Ivoire

L'impact de la mise en culture des forêts sur les peuplements de macroinvertébrés du sol a été étudié en moyenne Côte d'Ivoire avec pour objectif d'identifier les plus sensibles à la perturbation des forêts. Les macroinvertébrés du sol de parcelles de forêt secondaire et de cultures vivrières ont été échantillonnés en utilisant la méthode TSBF. A l'exception de la jachère, la mise en culture de la forêt secondaire a entraîné une réduction de la densité de 76,2 %, 22,1%, 22,1 %, 0,92 %, respectivement dans les champs de maïs, d'arachide, de riz et de bananiers plantain. Une Analyse en Composantes Principales (ACP) a montré que le «type de culture» et «l'effet du feu» sont susceptibles d'être les principaux facteurs qui déterminent l'abondance et la distribution des macroinvertébrés. Par ailleurs, les Fourmis, les Diplopodes, les Vers de terre, et les Coléoptères, se sont avérés comme les macroinvertébrés les plus sensibles à la dégradation des forêts.The impact of cropping systems in the secondary forest area on soil macro-invertebrates was investigated in middle Côte d'Ivoire with the aim of identifying the most sensitive organisms to forest perturbation. Soil macro-invertebrates from different cropping systems were sampled using TSBF methodology and their abundance were compared to the secondary forest referred as control. Except fallow, the conversion of secondary forest has reduced the density of macro-invertebrates at 76.2 %, 22.1 %, 22.1 %, 0.92 %, under maize, groundnut, rice and plantain banana fields respectively. A Principal Component Analysis (PCA) showed that the type of land-use and fire are factors controlling abundance and distribution of soil macro-invertebrates. In addition, ants, diplopoda, earthworms and coleoptera are likely to be the most sensitive organisms to forest perturbation. Keywords: Macroinvertébrés du sol, forêts, cultures vivrières, bio-indicateurs/Soil macro-invertebrates, forests, food crops, bio-indicatorsSciences & Nature Vol. 4 (2) 2007: pp. 197-20

Réponse des nématodes à la perturbation des forêts dans la région d\'Oumé, Côte d\'Ivoire.

La sensibilité des nématodes aux perturbations des forêts a été étudiée à l\'échelle du paysage dans la région d\'Oumé. L\'échantillonnage a été réalisé le long d\'un gradient de perturbations du milieu, partant des forêts vers le domaine rural, en raison de six répétitions par habitat. Les résultats ont montré que les nématodes libres représentent 68 % du peuplement de nématodes. Neuf genres de nématodes phytoparasites (Criconemella, Helicotylenchus, Heterodera, Hoplolaimus, Meloidogyne, Pratylenchus, Radopholus, Rotylenchulus et Xiphinema) ont été identifiés. Parmi ces nématodes, Rotylenchulus sp et Xiphinema sp peuvent être considérés comme bioindicateurs à cause de la tendance à la réduction de leurs populations le long du gradient d\'utilisation de sol. (r = -0,74 ; P = 0,03 et r = -0,77 ; P = 0,03).The sensitivity of nematode communities to forest perturbations has been studied in the region of Oumé at the landscape level. Six samples were collected along a gradient of perturbations from forests to lands crops areas. The results showed that the free-living nematodes accounted for 68 % of the nematode community. The plant-parasitic nematode community was composed by nine genera (Criconemella, Helicotylenchus, Heterodera, Hoplolaimus, Meloidogyne, Pratylenchus, Radopholus, Rotylenchulus and Xiphinema). Rotylenchulus sp and Xiphinema sp are likely to be considered as bio-indicators of forest degradation as their populations are significantly reduced along the gradient of land use change (r = -0.74, P = 0.03 and r = -0.77, P = 0.03). Keywords: bioindicateur, diversité, indice d'utilisation de sol, nématodes, paysage./bio-indicator, diversity, land use index, landscape, nematodes.Sciences & Nature Vol. 4 (2) 2007: pp. 189-19

Modeling the contribution of ecological agriculture for climate change mitigation in cote d'Ivoire

The use of crop models is motivated by the prediction of crop production under climate change and for the evaluation of climate risk adaptation strategies. Therefore, in the present study the performance of DSSAT 4.6 was evaluated in a cropping system involving integrated soil fertility management options that are being promoted as ways of adapting agricultural systems to improve both crop yield and carbon sequestration on highly degraded soils encountered throughout middle Côte d’Ivoire. Experimental data encompassed two seasons in the Guinea savanna zone. Residues from the preceding vegetation were left to dry on plots like mulch on an experimental design that comprised the following treatments: (i) herbaceous savanna-maize, (ii)10 year-old of the shrub Chromolaena odorata fallow-maize (iii) 1 or 2 year-old Lalab pupureus stand-rotation, (iv) the legume L. pupureus -maize rotation; (v) continuous maize crop fertilized with urea; (vi) continuous maize crop fertilized with triple superphosphate; (vii) continuous maize crop, fertilized with both urea and triple superphosphate (TSP); (viii) continuous maize cultivation. The model’s sensitivity analysis was run to figure out how uncertainty of stable organic carbon (SOM3) can generate variation in the prediction of soil organic carbon (SOC) dynamics during the monitoring period of two years, within the first soil layer and to estimate the most suitable value. The observed variations were of 0.05 % in total SOC within the short-term and acceptable dynamics of changes were obtained for 0.80% of SOM3. The DSSAT model was calibrated using data from the 2007-2008 season and validated against independent data sets of yield of 2008-2009 to 2011-2012 cropping seasons. After the default values for SOM3 used in the model was substituted by the estimated one from sensitivity analysis, the model predicted average maize yields of 1 454 kg ha-1 across the sites versus an observed average value of 1 736 kg ha-1, R2 of 0.72 and RMSE of 597 kg ha-1. The impact of fallow residues and cropping sequence on maize yield was simulated and compared to conventional fertilizer and control data using historical climate scenarios over 12 years. Improving soil fertility through conservation agriculture cannot maintain grain yield in the same way as conventional urea inputs, although there is better yield stability against high climate variability according to our results

Controls on timescales of soil organic carbon persistence across sub-Saharan Africa

Given the importance of soil for the global carbon cycle, it is essential to understand not only how much carbon soil stores but also how long this carbon persists. Previous studies have shown that the amount and age of soil carbon are strongly affected by the interaction of climate, vegetation, and mineralogy. However, these findings are primarily based on studies from temperate regions and from fine-scale studies, leaving large knowledge gaps for soils from understudied regions such as sub-Saharan Africa. In addition, there is a lack of data to validate modeled soil C dynamics at broad scales. Here, we present insights into organic carbon cycling, based on a new broad-scale radiocarbon and mineral dataset for sub-Saharan Africa. We found that in moderately weathered soils in seasonal climate zones with poorly crystalline and reactive clay minerals, organic carbon persists longer on average (topsoil: 201 ± 130 years; subsoil: 645 ± 385 years) than in highly weathered soils in humid regions (topsoil: 140 ± 46 years; subsoil: 454 ± 247 years) with less reactive minerals. Soils in arid climate zones (topsoil: 396 ± 339 years; subsoil: 963 ± 669 years) store organic carbon for periods more similar to those in seasonal climate zones, likely reflecting climatic constraints on weathering, carbon inputs and microbial decomposition. These insights into the timescales of organic carbon persistence in soils of sub-Saharan Africa suggest that a process-oriented grouping of soils based on pedo-climatic conditions may be useful to improve predictions of soil responses to climate change at broader scales

Earthworm management in tropical agroecosystems

Ecological and demographic parameters of 26 species of native and exotic earthworms species common in tropical agroecosystems, with large environmental tolerance and/or extended distribution were investigated. Principal component analysis (PCA) isolated four groups : (i) large native endogeic and anecic species (16-32 g individual fresh wt) with long generation time (2-4 years), low fecundity (0.5-3.1 cocoons/year/adult) and one hatchling per cocoon ; (ii) medium size species (1.2-6 g) endogeic mesohumic, with intermediate fecundity (1.3-45 cocoons/year/adult) ; (iii) small species (0.17-1.25 g f.w.) mainly endogeic polyhumic, with short generation time (3-7 months), intermediate fecundity (10-68 cocoons/year/adult) and one hatchling per cocoon ; and (iv) generally small (80-150 mg f.w.) species mainly exotic and epigeic, with short generation time (1-3 months), very high fecundity (50-350 cocoons/year/adult) and up to three hatchlings per cocoon. Casts may be either large globular or small granular. The selective investigations of large organic particles and small mineral particles (clays) concentrates total organic matter in the casts. There is an intense mineralization rate of nitrogen in the casts (6-29% of organic N), exotic worms seeming to be less efficient than natives at mineralizing N. The mineral phosphorus content of casts is always at least 30% higher than in the non-ingested soil. All these worms ingest daily, on average, three times their own weight of soil at the adult stage (1-9) and much more when juvenile ; up to 1000 Mg dry soil/ha may transit yearly through earthworm guts. (Résumé d'auteur

Stakeholder collaboration in climate-smart agricultural production innovations: insights from the Cocoa industry in Ghana

Although collaboration is vital in addressing global environmental sustainability challenges, research understanding on stakeholder engagement in climate-smart production innovation adoption and implementation, remains limited. In this paper, we advance knowledge about stakeholder collaboration by examining the roles played by stakeholders in scaling up ecological sustainability innovations. Using the illustrative context and case of green cocoa industry in Ghana, the analysis identified three distinctive phases of stakeholder engagement in ecological sustainability innovations implemented from 1960-2017. We highlight defining periods of ecological challenges encompassing the production recovery sustainability initiative phase solely driven by the Ghana Cocoa Board (COCOBOD)–a governmental body responsible for production, processing and marketing of cocoa, coffee and sheanut. During the period, major initiatives were driven by non-governmental organisations in collaboration with COCOBOD to implement the Climate-Smart agriculture scheme in the cocoa sector. The findings have implications for cocoa production research and stakeholder collaboration in environmental innovations adoption

Soil macroinvertebrate communities: A world-wide assessment

© 2022 The Authors. Global Ecology and Biogeography published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.[Aim] Macroinvertebrates comprise a highly diverse set of taxa with great potential as indicators of soil quality. Communities were sampled at 3,694 sites distributed world-wide. We aimed to analyse the patterns of abundance, composition and network characteristics and their relationships to latitude, mean annual temperature and rainfall, land cover, soil texture and agricultural practices.[Location] Sites are distributed in 41 countries, ranging from 55° S to 57° N latitude, from 0 to 4,000 m in elevation, with annual rainfall ranging from 500 to >3,000 mm and mean temperatures of 5–32°C.[Time period] 1980–2018.[Major taxa studied] All soil macroinvertebrates: Haplotaxida; Coleoptera; Formicidae; Arachnida; Chilopoda; Diplopoda; Diptera; Isoptera; Isopoda; Homoptera; Hemiptera; Gastropoda; Blattaria; Orthoptera; Lepidoptera; Dermaptera; and “others”.[Methods] Standard ISO 23611-5 sampling protocol was applied at all sites. Data treatment used a set of multivariate analyses, principal components analysis (PCA) on macrofauna data transformed by Hellinger’s method, multiple correspondence analysis for environmental data (latitude, elevation, temperature and average annual rainfall, type of vegetation cover) transformed into discrete classes, coinertia analysis to compare these two data sets, and bias-corrected and accelerated bootstrap tests to evaluate the part of the variance of the macrofauna data attributable to each of the environmental factors. Network analysis was performed. Each pairwise association of taxonomic units was tested against a null model considering local and regional scales, in order to avoid spurious correlations.[Results] Communities were separated into five clusters reflecting their densities and taxonomic richness. They were significantly influenced by climatic conditions, soil texture and vegetation cover. Abundance and diversity, highest in tropical forests (1,895 ± 234 individuals/m2) and savannahs (1,796 ± 72 individuals/m2), progressively decreased in tropical cropping systems (tree-associated crops, 1,358 ± 120 individuals/m2; pastures, 1,178 ± 154 individuals/m2; and annual crops, 867 ± 62 individuals/m2), temperate grasslands (529 ± 60 individuals/m2), forests (232 ± 20 individuals/m2) and annual crops (231 ± 24 individuals/m2) and temperate dry forests and shrubs (195 ± 11 individuals/m2). Agricultural management decreased overall abundance by ≤54% in tropical areas and 64% in temperate areas. Connectivity varied with taxa, with dominant positive connections in litter transformers and negative connections with ecosystem engineers and Arachnida. Connectivity and modularity were higher in communities with low abundance and taxonomic richness.[Main conclusions] Soil macroinvertebrate communities respond to climatic, soil and land-cover conditions. All taxa, except termites, are found everywhere, and communities from the five clusters cover a wide range of geographical and environmental conditions. Agricultural practices significantly decrease abundance, although the presence of tree components alleviates this effect.Peer reviewe