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In the current debate on the role of increase soil carbon in addressing both climate change and food security, there is consensus that farmed lands have the higher potential provided the best management practices are implemented. In the Sahel where farms usually have few sparse old trees with declining soil fertility, there is an ongoing re-greening process with increases in tree cover for which there is still a dearth of quantified information on its impacts on soil properties. This research aimed at filling that gap. We sampled soil using a concentric zone design around individual trees of dominant species and at different soil depths (0–10, 10–30, 30–50 and 50–70 cm) in four Sahelian countries: Burkina Faso, Mali, Niger and Senegal. The results showed increase total carbon content of the top 0–10 cm soil, generally with high sand content (> 70%), ranged from 0.16 to 0.44% (mean 0.23%). Under trees it was a factor 1.04–1.47 higher than away from trees. Different tree species thrived in different ecological niches and had different impacts on soil properties, highlighting the need for site and species matching in restoration activities. These results suggest that increase vegetation cover in the Sahel is associated with an increase in soil total carbon and this trend is more pronounced on sandy soils.

Manglietia conifera Dandy is a fast-growing tree species that has been introduced to China from Vietnam, which has great potential for commercial planting. However, plantation development is hindered by a lack of seed material, due to low natural seed-set in locally grown trees. Thus, we investigated the morphological characteristics of male and female flower organs, and conducted controlled pollination to understand the breeding systems of the species. The individual flower of M. conifera is bisexual, and the stamen group is polymerized at the base of the receptacle. Pollen is symmetrically distributed on both sides. Controlled pollination suggests that apomixis does not occur in M. conifera. Results from the flower structure, pollen&ndash, ovule ratio, outcrossing index, and controlled pollination indicated that the breeding system in M. conifera was outcrossing (partially self-compatible, pollinators required), and self-incompatibility occurred in a later stage of embryonic development. Moreover, the self-incompatibility phenomenon was revealed by the abnormal germination of pollen on the stigma. This paper provides a basis for controlled pollination programs of M. conifera.

The success of terrestrial carbon sequestration projects for rural development in sub-Saharan Africa lies in the (i) involvement of local populations in the selection of woody species, which represent the biological assets they use to meet their daily needs, and (ii) information about the potential of these species to store carbon. Although the latter is a key prerequisite, there is very little information available. To help fill this gap, the present study was undertaken in four pilot villages (Kou, Dao, Vrassan and Cassou) in Ziro Province, south-central Burkina Faso. The objective was to determine carbon storage potential for top-priority woody species preferred by local smallholders. We used (i) participatory rural appraisal consisting of group discussions and key informant interviews to identify priority species and functions, and (ii) landscape assessment of carbon stocks in the preferred woody species. Results revealed over 79 priority tree and shrub species grouped into six functions, of which medicine, food and income emerge as the most important ones for the communities. For these functions, smallholders overwhelmingly listed Vitellaria paradoxa, Parkia biglobosa, Afzelia africana, Adansonia digitata, Detarium microcarpum, and Lannea microcarpa among the most important tree species. Among the preferred woody species in Cassou and Kou, the highest quantity of carbon was stored by V. paradoxa (1,460.6 ±271.0 kg C ha−1 to 2,798.1±521.0 kg C ha−1) and the lowest by Grewia bicolor (1.6±1.3 kg C ha−1). The potential carbon stored by the preferred tree communities was estimated at 5,766.2 Mg C ha−1 (95% CI: 5,258.2; 6,274.2 Mg C ha−1) in Kou and 6,664.0 Mg C ha−1 (95% CI: 5,810.2; 7,517.8 Mg C ha−1) in Cassou. The findings of this study will help design data-based development of biocarbon projects, which are rare in the West African Sahel despite being considered as one of the most impactful climate change resilient strategies.

In the Sahelian countries, gathering of agroforestry tree products is one of the few livelihood activities that hold great potential for income generation and poverty reduction among resource-poor households. This study explores the determinants of market participation and selling decisions, which are key prerequisites for sustainable intensification and commercialization of the rural economy. A commercialized economy provides invaluable opportunities for smallholder farmers to increase their income and escape from poverty traps that are faced by most rural households in the Sahel. The results from a cross-sectional sample of 1080 households drawn from four Sahelian countries, namely Mali, Niger, Burkina Faso and Senegal, lend support to the relevance of three sets of variables in explaining agroforestry farmers’ participation in markets and selling decisions. Market participation and selling decisions are affected by predisposing, facilitating and reinforcing factors. In areas where markets for tree products are functioning well, long distances from the main markets do not deter agroforestry farmers from participating in markets and selling decisions. This demonstrates that other interventions to strengthen value chains and market integration can be successful even where transportation is more costly.

Combination of poor soil fertility and climate change and variability is the biggest obstacle to agricultural productivity in Sub-Saharan Africa. While each of these factors requires different promising adaptive and climate-resilient options, it is important to be able to disaggregate their effects. This can be accomplished with ordinary agronomic trials for soil fertility and climate year-to-year variability, but not for long-term climate change effects. In turn, by using climate historical records and scenario outputs from climate models to run dynamic models for crop growth and yield, it is possible to test the performance of crop management options in the past but also anticipate their performance under future climate change or variability. Nowadays, the overwhelming importance given to the use of crop models is motivated by the need of predicting crop production under future climate change, and outputs from running crop models may serve for devising climate risk adaptation strategies. In this study we predicted yield of one maize variety named Massongo for the time periods 1980–2010 (historical) and 2021–2050 (2030s, near future) across agronomic practices including the fertilizer input rates recommended by the national extension services (28 kg N, 20 kg P, and 13 kg K ha−1). The performance of the crop model DSSAT 4.6 for maize was first evaluated using on-farm experimental data that encompassed two seasons in the Sudano-Sahelian zone in six contrasting sites of Central West Burkina Faso. The efficiency of the crop model was evidenced by reliable simulations of total aboveground biomass and yields after calibration and validation. The root-mean-square error (RMSE) of the entire dataset for grain yield was 643 kg ha−1 and 2010 kg ha−1 for total aboveground biomass. Three regional climate change projections for Central West Burkina Faso indicate a decrease in rainfall during the growing period of maize. All the three scenarios project that the decrease in rainfall is to the tune of 3–9% in the 2030s under RCP4.5 in contrast to climate scenarios produced by the regional climate model GCM ICHEC-EC-Earth which predicted an increase of rainfall of 25% under RCP8.5. Simulations using the CERES-DSSAT model reveal that maize yields without fertilizer show the same trend as with fertilizer in response to climate change projections across RCPs. Under RCP4.5 with output from the climate model ICHEC-EC-Earth, yield can slightly increase compared to the historical baseline on average by less than 5%. In contrast, under RCP8.5, yield is increased by 13–22% with the two other climate models in fertilized and non-fertilized plots, respectively. Nevertheless, the average maize yield will stay below 2000 kg ha−1 under non-fertilized plots in RCP4.5 and with recommended mineral fertilizer rates regardless of the RCP scenarios produced by ICHEC-EC-Earth. Giving the fact that soil fertility improvement alone cannot compensate for the adverse impact of future climate on agricultural production particularly in case of high rainfall predicted by ICHEC-EC-Earth, it is recommended to combine various agricultural techniques and practices to improve uptake of nitrogen and to reduce nitrogen leaching such as the splitting of fertilizer applications, low-release nitrogen fertilizers, agroforestry, and any other soil and water conservation practices.

Rural communities in West Africa value Prosopis africana for its wood and other essential products and environmental services. The climate is becoming hotter and drier with more variable rainfall, so it is important to identify provenances that are better adapted to a hotter, drier climate. Some tree improvement research programs use nursery tests to identify better adapted provenances, but are conclusions comparable to those from field tests? We analyzed data (height, root dry weight, shoot dry weight, root/shoot ratio, survival) from a provenance/progeny nursery test of P. africana at 8 months, and compared the results with a field test at 11 and 13 years. The tests included 275 families from 28 provenances in the Sahelian and Sudanian ecozones of Burkina Faso and Niger, and were established at one relatively dry site in Niger. The proportion of total variance due to provenances and families within provenances was greatest for root/shoot ratio, and root/shoot ratio had the highest heritability of growth variables in the nursery. Provenances with smaller seedlings and larger root/shoot ratios in the nursery had better growth and survival in the field, and were from drier locations. Mean annual rainfall of provenances was the best predictor of provenance growth and survival in the field, followed by provenance height and root/shoot ratio in the nursery. We recommend that tree improvement research programs in the Sahelian and Sudanian ecozones of West Africa identify P. africana provenances that are from drier locations and have smaller seedlings and larger root/shoot ratios in the nursery for planting in agroforestry projects in rural communities.

This paper used a multivalued treatment framework to assess the effects of farmer managed natural regeneration (FMNR) on selected outcomes among 1080 rural household farmers in the Sahelian and Sudano-Sahelian ecozone of West Africa Sahel. The results indicate that keeping, protecting and managing trees in the farmland have significant effects on the livelihoods of the rural poor in the Sahelian countries. If 1000 households in a community decide to practice the FMNR continuously, it results in an increase in the gross income by US$ 72,000 per year. Noticeable changes are also observed on the value of tree products, with an observed significant increase in the value of the products harvested from tree by about 34–38 % among those actively practicing FMNR as compared to their counterparts. The results also lend support to the household resilience hypothesis of FMNR in that it leads to a significant increase of the dietary diversity by about 12–14 %. However, it also appeared that several factors impeded the regeneration of trees on farms. To foster the widespread dissemination and enhance the capacity of farmers to increase, diversify and sustain tree-based production systems, an enabling institutional, technical and policy environment needs to be promoted.

Traditional agroforestry parkland systems in Burkina Faso are under threat due to human pressure and climate variability and change, requiring a better understanding for planning of adaptation. Field experiments were conducted in three climatic zones to assess Sorghum bicolor (L.) Moench (Sorghum) biomass, grain yield and harvest index in parklands under different rainfall pattern and compared to simulations of sorghum biomass and grain yield with the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model for calibration and parametrisation. For planning adaptation, the model was then used to evaluate the effects of different management options under current and future climates on sorghum biomass and grain yield. Management options studied included tree densities, tree leaf pruning, mulching and changes in tree root patterns affecting hydraulic redistribution. The results revealed that sorghum biomass and grain yield was more negatively affected by Parkia biglobosa (Jacq.) Benth. (nere) compared to Vitellaria paradoxa C. F Gaertn (karite) and Adansonia digitata L. (baobab), the three main tree species of the agroforestry parkland system. Sorghum biomass and grain yield in different influence zones (sub-canopy, outside edge of canopy, open field) was affected by the amount of precipitation but also by tree canopy density, the latter depending itself on the ecological zone. The harvest index (grain as part of total biomass) was highest under the tree canopy and in the zone furthest from the tree, an effect that according to the model reflects relative absence of stress factors in the later part of the growing season. While simulating the effects of different management options under current and future climates still requires further empirical corroboration and model improvement, the options of tree canopy pruning to reduce shading while maintaining tree root functions probably is key to parkland adaptation to a changing climate.

The present study aims at (1) assessing how the existing local formal and informal institutions affect farmer managed natural regeneration (FMNR) practices and, (2) evaluating the benefits of such practices on livelihoods. The propensity score with continuous treatments was used to assess the effects of a set of covariates on FMNR as well as the impacts of that practice on income, cereal production and caloric intake using data collected from 1,080 rural households in Burkina Faso, Mali, Niger, and Senegal. This study demonstrated that regeneration of trees on farms, whereby farmers play an active role in the types of trees and their densities, is important as a practice and safety-net by providing cash income, caloric intake and diet, and crops supplements throughout dryland areas of West Africa. Overall, FMNR cannot be excluded as a recommendation in any geographical region. In addition, the study concludes that the effects of institutions in fostering FMNR practices in the Sahel are mixed. In areas with well-structured formal and informal institutions, populations seem to have adopted a better collaboration attitude with the local government by developing plans for a good management and protection of natural resource including FMNR practices. However, in areas where these commissions are being assimilated to governmental institutions, the willingness to raise incentives towards a better management of natural resources is less perceived. While recognizing the benefits of trees and tree products on caloric intake and diet, there is a need to explore in much more details, the FMNR-food nexus in future researches by going beyond what was covered from this study.

It is increasingly becoming clear that reforms based on the claims of local forest communities regarding the right to natural resources will be needed to adequately address issues of sustainable development in Sub-Saharan Africa. The current institutional and policy frameworks of Cameroon and other SSA countries have bestowed exclusive land tenure rights to the State, while curtailing access of local farmers to forest and forest-based resources on which they depend for a living. It is therefore unlikely that successful forest conservation and implementation of REDD+ can be possible without recognition and enforcement of customary tenure. This paper aimed to sense smallholders' perceptions on rights and risks in the current forestry policy arena linked with the climate change debate in Cameroon. Using semistructured questionnaires and focus group discussions about 7 key informants and 66 community forest users were investigated about the current tenure systems and the risks of related conflicts. Findings from the field provide empirical evidence on the sources of conflict. Based on failures and positive elements of community forestry, the lessons learnt could enrich the on-going REDD safeguard debates and serve as guiding milestones towards the effectiveness of this initiative across the country and the continent.

In the West African drylands, SOC sequestration is seen as one of the prominent strategies to both enhance the resilience of agro-ecosystems and mitigate global greenhouse effects. However, there is a dearth of baseline data that impede the design of site-appropriate recommended management practices (RMPs) to improve and sustain SOC accrual. In this study, the Land Degradation Surveillance Framework (LDSF), a nested hierarchical sampling design was used to assess SOC and its spatial variability across the semi-arid zones of Ghana (Lambussie), Burkina Faso (Bondigui) and Mali (Finkolo). Soil samples were collected from three sites of 100 km2 stratified into 16 clusters and 160 plots and thereafter soil parameters were then analyzed using MIR spectroscopy. Regardless of soil strata, SOC storage with 95 % confidence level in semi-arid landscapes potentially ranged between 112 200 ± 14 000 and 253 000 ± 34 000 Mg C corresponding to 411 400 ± 51 333 Mg CO2-eq and 927 666.7 ± 124 666.7 Mg CO2-eq in the entire study area. On the other hand, investigation on the potential of climate change mitigation through SOC revealed contrasted figures as accumulation rates in cultivated lands ranged from 0.04 to 0.18 MgC ha−1 yr−1 and are balanced by higher depletion rates of −0.004 to −0.73 Mg ha−1 yr−1. This indicates the potential of semi-arid soils to store carbon through improved land management practices. Landscape study structured in cluster-level analysis revealed heterogeneity in the distribution of SOC stocks, a mandatory finer level analysis prior to effective decision-making about RMPs.

Introduction . Notre etude a porte sur l’identification des insectes nuisibles des fruits de jujubiers indiens introduits au Burkina Faso. Notre objectif a ete de faire l’inventaire de ces insectes ravageurs infeodes a ces nouveaux cultivars de jujubiers et de tester diverses techniques pour leur piegeage. Apres identification des insectes dont la plante hote est le jujubier, nous avons determine ceux qui accomplissent leur cycle de reproduction sur les jujubes. Materiel et methodes . Nous avons utilise des appâts alimentaires avec des pieges de fabrication industrielle renfermant du torula et du terpinyl acetate et teste l’efficacite de complexes [pieges artisanaux / attractifs naturels] par rapport aux pieges a torula. Ensuite, nous avons mis en incubation des fruits attaques afin d’identifier les insectes qui en emergeraient. La fluctuation des populations de Tephritidae a ete suivie a partir de releves hebdomadaires dans les pieges a torula. Simultanement l’evolution de la production fruitiere a ete etudiee. Resultats . L’inventaire effectue en verger de jujubiers indiens a revele la presence de plusieurs familles appartenant a l’ordre des dipteres parmi lesquelles figurent dix especes de mouches de fruits reparties dans quatre genres (Bactrocera , Dacus , Ceratitis et Carpomya ) ; une noctuelle de l’ordre des lepidopteres (genre Agrotis ) a egalement ete identifiee. Les especes les plus representees dans les collectes effectuees par pieges ont ete Carpomya incompleta (44,86 %), Bactrocera invadens (21,58 %) et Bactrocera cucurbitae (18,49 %). Le taux d’emergence apres incubation des jujubes attaques a ete de 50 %. Deux especes seulement ont emerge de ces fruits : C. incompleta (84 %) et Agrostis sp. (16 %). Parmi les appâts alimentaires naturels testes, seul le melange [biere locale + banane] a permis de pieger des Tephritidae (Bactrocera invadens ) et la noctuelle Agrotis sp. Cependant, deux autres appâts naturels (fruits en putrefaction et lait concentre) ont permis de capturer Agrotis sp. Discussion et conclusion . Nos resultats ont mis en evidence les deux ravageurs potentiels des jujubiers indiens au Burkina Faso. Des etudes complementaires sur l’identification de l’espece d’Agrotis , et sur la biologie, l’ecologie et le comportement des ravageurs incrimines seront necessaires pour la definition de methodes de lutte en plantations de jujubiers au Burkina.

To address the decline in crop productivity in the drylands of West Africa, many initiatives have focused on combating soil degradation. Various practices including (1) parkland trees associated with crops, (2) coppicing trees, (3) green manure, (4) mulching, (5) crop rotation and intercropping, and (6) traditional soil/water conservation have been tested. The present study attempts to provide a comprehensive, quantitative synthesis of existing reports on the effect of conservation agriculture (CA) practices on crop yield response in Burkina Faso, Mali, Niger and Senegal. Out of a total of 155 reports found, 63 fulfilled all the appropriate criteria to be included in the meta-analysis of the effect of various conservation agriculture practices on the yield response of maize, millet and sorghum. The study revealed significant variability in cereal yield response (and hence risk) with all the practices examined. Despite the variability, the mean effects of the six CA practices on crop yield were more positive than negative except with parkland trees. However, for this last practice, species like Faidherbia albida exerts more positive impact on crop yield. Yield increases relative to the control were higher with green manure and mulching than with coppicing trees and parklands. Increases in yield in the six CA practices were higher on low to medium productivity sites for maize, millet and sorghum. Coppicing trees and rotations improved yields when the rainfall is >800 mm whereas the opposite happens with parkland and soil–water conservation measures. Mulching performed better when the rainfall is

Producing more food for a growing population in the coming decades, while at the same time combating poverty and hunger, is a huge challenge facing African agriculture. The risks that come with climate change make this task more daunting. However, hundreds of thousands of rain fed smallholder farmers in Zambia, Malawi, Niger, and Burkina Faso have been shifting to farming systems that are restoring exhausted soils and are increasing food crop yields, household food security, and incomes. This article reviews these experiences, and their broader implications for African food security, as manifestations of Evergreen Agriculture, a fresh approach to achieving food security and environmental resilience. Evergreen Agriculture is defined as the integration of particular tree species into annual food crop systems. The intercropped trees sustain a green cover on the land throughout the year to maintain vegetative soil cover, bolster nutrient supply through nitrogen fixation and nutrient cycling, generate greater quantities of organic matter in soil surface residues, improve soil structure and water infiltration, increase greater direct production of food, fodder, fuel, fiber and income from products produced by the intercropped trees, enhance carbon storage both above-ground and below-ground, and induce more effective conservation of above- and below-ground biodiversity. Four national cases are reviewed where farmers are observed to be applying these principles on a major scale. The first case involves the experience of Zambia, where conservation farming programmes include the cultivation of food crops within an agroforest of the fertilizer tree Faidherbia albida. The second case is that of the Malawi Agroforestry Food Security Programme, which is integrating fertilizer, fodder, fruit, fuel wood, and timber tree production with food crops on small farms on a national scale. The third case is the dramatic expansion of Faidherbia albida agroforests in millet and sorghum production systems throughout Niger via assisted natural regeneration. The fourth case is the development of a unique type of planting pit technology (zai) along with farmer-managed natural regeneration of trees on a substantial scale in Burkina Faso. Lastly, we examine the current outlook for Evergreen Agriculture to be further adapted and scaled-up across the African continent.

En plus des contraintes biophysiques, l'insuffisance des connaissances scientifiques sur l'ecologie de la regeneration naturelle seminale de nombreuses especes ligneuses des pays saheliens ne favorisent pas la mise au point de techniques sylvicoles adaptees aux stades juveniles de la regeneration. L'objectif de cette etude est de suivre le developpement des semis de cinq especes ligneuses des formations vegetales naturelles soudaniennes : Terminalia avicennioides Guill. et Perr., Piliostigma thonningii (Schumach. & Thonn.) Milne-Redh., Isoberlinia doka Caib et Stapf, Afzelia africana Sm. et Detarium microcarpum Guill. et Perr. L'etude a ete conduite sur des plantules elevees en rhizotron sur deux types de profils pedologiques. Les resultats montrent que toutes les especes, sauf A. africana, ont une germination cryptogee. Au stade juvenile, les plantules allouent preferentiellement les ressources aux organes souterrains. Cela se traduit par une tuberisation due a une accumulation de reserves et un enracinement precoce du pivot racinaire. La vitesse de croissance du pivot racinaire est variable selon les especes et le type de sol. La plus forte vitesse de croissance du pivot a ete observee chez D. microcarpum et la plus faible chez T. avicennioides. La croissance racinaire des plantules de T. avicennioides et de A. africana est sensible a la compacite du sol. La germination cryptogee et le developpement precoce du systeme racinaire permettent aux plantules, sauf les plantules non cryptogees d’A. africana, de mieux supporter la secheresse, le passage des feux et le broutage en rejetant de souche. Les plantules ont une croissance aerienne rythmique due a un fonctionnement rythmique du meristeme apical.

Phylogeographic studies of tropical and subtropical tree species provide an ideal method to study the role of forest refugia in the structuring of genetic diversity in contemporary populations. To date, most studies have examined rainforest-dependent trees, yet the influence of forest refugia on savannah forest and woodland trees remains poorly understood despite their potentially important role in forest assemblages during the last glacial maximum. Here, we examine the level and structuring of genetic diversity across the geographic range of the savannah woodland tree, Khaya senegalensis—African mahogany, from Senegal to Uganda (>5000 km) and from the steppes of the Sahara desert to the fringes of Africa’s equatorial rainforests (700 km). Three chloroplast (cpDNA) loci and 13 nuclear microsatellite (nSSR) loci were genotyped in 503 individuals. Individual-based clustering of nSSR genotypes identified that all samples formed two populations that showed no pattern of geographic structuring. Population level analysis of nSSR data revealed only very weak genetic structure (FST = 0.013) with most of the genetic diversity contained within populations. Geographical differentiation (GST = 0.096) was low for the 14 haplotypes identified. However, whereas all haplotypes occurred in the western populations (including Cameroon), only two cosmopolitan haplotypes were found in central-eastern populations. Geographically restricted low-frequency haplotypes were found in eight western populations. Higher genetic diversity in western populations was confirmed by patterns of allelic richness, which were lower in central-eastern populations. Taken together, these results indicate that K. senegalensis displays very little genetic differentiation across its geographic range and that previously identified barriers to dispersal across the northern savannah belt of tropical Africa (e.g. the Dahomey Gap, Mega Lake Chad and the Adamawa Highlands) have not impeded contemporary gene dispersal in this species. Nevertheless, clustering of rare haplotypes indicates that the Dahomey Gap has likely been an important historical barrier to genetic connectivity between western and eastern regions of the species and that it is likely that this savannah tree also experienced range contraction around major forest refugial fringes or riparian incursions during the last glacial maximum (LGM).

The floral visitors of silky oak, Grevillea robusta A. Cunn. ex R.Br., their foraging behaviour and their effects on fruit-set were studied at Malava, western Kenya. Grevillea robusta is a popular tree for farm plantings in the eastern and central African highlands. Yield of seed has been disappointingly low in some areas and a lack of appropriate pollinators has been suggested as a possible cause. Investigations involved the monitoring of visitors on active inflorescences, assessment of the rewards available to potential pollinators, and exclusion experiments to establish the effects of various visitors on fruit-set. The flowers are visited mainly by birds and insects. The likely pollinators of G. robusta are sunbirds (Nectarinia amethystina, N. cyanolaema, N. olivacea, N. superba and N. venusta) and white-eyes (Zosterops kikuyuensis and Z. senegalensis). Very little aggressive behaviour between birds was recorded. No nocturnal pollinators were observed. Nectar was the major floral reward for pollinators, but is likely depleted by ants and honey bees, the foraging behaviour of which confirmed them to be nectar-robbers. These insects hardly ever touched stigmas during their visits. Eighty-nine per cent of bird visits were in the morning (07.00-10.00 hours) when nectar volume was highest. Inflorescences bagged to exclude birds set no fruits, and unmanipulated flowers and flowers bagged with self-pollen set no fruits, indicating a self-incompatibility mechanism. Control cross-pollinated flowers displayed greatly increased fruit-set (25.1%) compared with natural open-pollination (0.9%). All these findings confirm the importance of cross-pollen transfer to flowers and the neces- sity of pollinators for fruit-set. Effective seed production requires activity of pollinators for self-pollen removal and cross-pollen deposition. Seed production stands for G. robusta should be established where flowering is prolific and bird pollinators are abundant.

The reproductive biology of Grevillea robusta growing under exotic conditions in Kenya and Australia is reported. The species showed both protandry and a self-incompatibility mechanism. The stigma was wet and papillate with a distinct groove in the middle. The anthers dehisced prior to anthesis, when the perianth opened. Stigmatic receptivity began 1 d after anthesis, with the greatest pollen germination rates and longest pollen tubes obtained 2 d after anthesis. Nectar secretion commenced with pollen dehiscence and was abundant at anthesis. Most stigmatic grooves opened widely 1–2 d after anthesis and stigmas showed taller papillae and abundant secretion. Controlled pollinations gave a greater fruit set from cross-pollination (5.9% in April and 17.5% in July) than open-pollination (0.1% in April and 3.3% in July). No fruit set from self-pollination was obtained in April, and very few fruit set for geitonogamous (two out of 1622; 0.1%) or for autogamous (one out of 2707 flowers; 0.04%) pollination treatments in July. Following self-pollination, growth of pollen tubes was poorer than in other treatments, and was generally arrested in the upper style. Cross-pollinated flowers produced normal and straight pollen tubes, while self-pollen tubes had growth abnormalities. Most of the open-pollinated flowers were found without pollen or with only self-pollen on their stigmas indicating that the amount of cross-pollen reaching the stigma under open-pollination may be a factor limiting seed production. Flowers shed soon after the fertilization phase were those with ungerminated pollen or no pollen. Although a very low rate of selfing may occur, G. robusta presents a self-incompatibility system and allogamy is its primary breeding behaviour.

Products and services provided by trees in forests and farmland support the needs and promote the wellbeing of hundreds of millions of people in the tropics. Value depends on managing both the diversity of tree species present in landscapes and the genetic variation within these species. The benefits from trees and their genetic resources are, however, often not well quantified because trade is frequently outside formal markets, there is a multiplicity of species and ways in which trees are used and managed, and genetic diversity within species is frequently not given proper consideration. We review here what is known about the value of trees to rural communities through considering three production categories: non-timber products harvested from trees in natural and managed forests and woodlands; the various products and services obtained from a wide range of trees planted and/or retained in smallholders' agroforestry systems; and the commercial products harvested from cultivated tree commodity crops. Where possible, we focus on the role of intra-specific genetic variation in providing support to livelihoods, and for each of the three production categories we also consider wider conservation and sustainability issues, including the linkages between categories in terms of management. Challenges to 'conventional wisdom' on tree resource use, value and management -such as in the posited links between commercialisation, cultivation and conservation -are highlighted, and constraints and opportunities to maintain and enhance value are described. © 2014 The Authors.

There is little information about inter- and intra-specific variation in fuelwood properties of trees/shrubs in West Africa. We studied variation in fuelwood properties of Balanites aegyptiaca, Combretum glutinosum, Guiera senegalensis, Piliostigma reticulatum, and Zizyphus mauritiana in the Sahelian and Sudanian ecozones of Mali. Trees were sampled on different soil (sandy, sandy/loam, or rocky), land use (parkland agroforest or woodland), and terrain (flat, temporarily flooded, or hill slope) types in five regions extending from the drier eastern to the more humid western parts of Mali. Basic density, volatile matter, fixed carbon, ash content, moisture content, gross calorific value, and fuel value index were measured for each tree and adjusted for tree age. All fuelwood properties differed significantly among species, but there were significant species by region interactions. Most fuelwood properties of four species differed significantly among regions. Soil and/or land use type had significant effects on a few fuelwood properties of four species. In general, fuelwood production is recommended in all regions for G. senegalensis, in drier regions for B. aegyptiaca and C. glutinosum, in more humid regions for Z. mauritiana, and on rocky soils for all species. Fuelwood production of P. reticulatum is not recommended.

Le baobab, Adansonia digitata L., est classé parmi les cinq espèces ligneuses prioritaires au Burkina Faso dont le paysage agraire montre une distribution irrégulière de cette espèce. Les principaux déterminants socioculturels de cette distribution demeurent cependant peu ou mal connus. Le but de cette étude est de caractériser la structure et les facteurs socioculturels qui déterminent la distribution du baobab dans le Centre-Nord et le Centre-Ouest du Burkina Faso. Les travaux ont été menés à travers des inventaires forestiers, des enquêtes socio-éco-nomiques et des observations de terrain sur les pratiques paysannes. Les résultats montrent qu'à l'intérieur d'un même terroir la structure du baobab varie en fonction du type de champ (case, village, brousse). La structure des diamètres épouse une forme en «L» dans les champs de case, une forme en «j» dans les champs de brousse et irrégulière dans les champs de village. Le baobab est considéré dans toute la zone d'étude comme une espèce maléfique abritant des génies, mais aussi en tant que plante alimentaire et médicinale de premier plan. Contrairement au Centre-Ouest, les produits du baobab sont largement utilisés dans l'alimentation et l'artisanat dans le Centre-Nord, où les populations l'entretiennent dans les champs de case et de village par la pratique de la régénération naturelle assistée. La faible présence du baobab dans le Centre-Ouest est en partie liée aux habitudes, au développement du maraîchage qui favorise la disponibilité de condiments alternatifs et aux perceptions que les populations ont vis-à-vis de cet arbre. (Résumé d'auteur)

In the Sahelian zone of West Africa, crops grown under a discontinuous cover of scattered trees dominate many landscapes and constitute the so-called parklands. These systems reflect the ecological knowledge of the farmers of such risk prone environments. Agroforestry parklands are playing an important role, through trees and shrubs providing soil cover that reduces erosion and buffers the impacts of climate change. They also provide green fodder that complements crop residues for livestock feeds, and fruits and leaves for human consumption and for income generation. The interactions between various components of the system influence the ecosystem service functions of trees of parklands (provisioning, regulating and supporting services) in several ways. These ecosystem functions have been at the center of the local ecological knowledge guiding the management options of the farmers and have also attracted the attention of scientists. Findings revealed new challenges that call for production options ensuring increased and diversified productivity of the systems while preserving the environment. Research on such challenges must adopt an inclusive approach based on local knowledge supported by science-based analyses of the socio-ecological systems in the face of high population pressure and climate change.