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Tree-scale estimation of clove (Syzygium aromaticum) production in Madagascar: A first step toward the performance evaluation of clove-based agroforestry systems
No full textThe clove tree (Syzygium aromaticum) is a major cash crop in Madagascar, cultivated for its dried clove bud and essential oil, and is a crucial source of income for smallholder farmers in a country that is a leading global producer of both products. Clove trees are grown in both monospecific and agroforestry systems, which vary in structural and botanical complexity: in monospecific plots, clove trees dominate, whereas in agroforestry systems, they coexist with various species. Agroforestry systems are recognized for improving resilience to climatic and economic fluctuations. Clove production shows strong tree-to-tree variability at the plot scale, driven by factors such as genotype, age, and crown dimensions, which define tree potential production. Planting practices—including replanting frequency and spatial arrangement—are dynamic and evolve over time, and farmers manage plots individually, creating variabilities in tree age and crown dimension, inducing yield spatial variability. In agroforestry systems, this variability is further increased by species diversity and competition, and the perennial nature of clove trees, combined with irregular bearing patterns shaped by environmental factors and previous reproductive cycles, results in significant interannual yield variations. Despite its economic importance, the techno-economic performance of clove-based systems is poorly documented, largely because of a lack of accurate yield data and challenges in accounting for production variabilitys, and currently no quantitative data on individual clove tree production is available for Madagascar. This study addresses this gap by assessing clove production at the tree level in the village of Ansirakoraka (Analanjirofo region). We aim to (i) quantify production in relation to endogenous traits (crown dimensions, height) and (ii) evaluate cropping system effects (monospecific vs. agroforestry). In 2024, we sampled 126 trees across 11 plots (6 monospecific, 5 agroforestry), with 63 trees per system. Crown dimensions (height, trunk circumference, crown volume) and bud load were assessed on the field prior harvest. Trees were classified by crown volume—small (37 m³)—and by bud load—low (67%)—corresponding to the lower, middle, and upper thirds of the respective distributions. Each crown volume × bud load × system combination was represented by 7 trees. Production was measured as fresh and dry weight. The results showed no significant effect of the cropping system on clove tree production (p > 0.05). However, a significant relationship (R² = 0.61) was found between clove dry weight, crown volume, and bud load. Figure 1 shows a clear increase in clove weight with both crown volume and bud load. Trees with small crowns produced 0.26 kg, 0.49 kg, and 1.10 kg of dry cloves under low, intermediate, and high bud loads, respectively. Medium-crowned trees produced 0.64 kg, 1.10 kg, and 2.50 kg, while large-crowned trees reached 0.92 kg, 2.70 kg, and 5.20 kg for low, intermediate, and high bud loads, respectively. These findings provide a quantitative basis for modeling clove production based on tree features, and offer a first step for improving the assessment of clove-based agroforestry systems, particularly in Madagascar's diverse landscapes
Light-driven genotype-environment interactions in coffee: Comparing hybrids and parental lines under a controlled shade gradient
Get PDFLow light is a characteristic of coffee agroforestry systems, yet the optimal shade level for establishing such systems remains unclear. Furthermore, the effects of reduced light on the growth and physiology of juvenile Coffea arabica F1 hybrids have not been fully explored. This study examined gene-by-environment interactions among coffee hybrids and their parental lines across a controlled shade gradient in a greenhouse. The tested C. arabica included landrace accessions (i.e. 'ET531', 'MS', 'T4905', and 'Rume Sudan'), pure lines (i.e. 'Caturra','T5296', 'Marsellesa' and 'IAPAR59'), and F1 hybrids (i.e. 'H1', 'H3', 'Mariana', and 'Starmaya'). Plants were grown under five shade treatments intercepting 0, 35, 58, 73, and 88% of ambient light (ranging from ~10 to 800 μmol m−2 s−1) to simulate agroforestry light environments. Shade significantly influenced all measured traits, including photosynthetic parameters, chlorophyll a fluorescence, aboveground biomass, specific leaf area, total leaf area, growth rate and leaf count. Notably, the line varieties 'Caturra' and 'Marsellesa' and hybrid 'Starmaya' demonstrated comparatively enhanced vegetative performance when grown under shade (i.e, shade level of 35 – 88%), particularly in leaf count (ca. 75 % more), plant height (ca. 75 % taller), and stem dry mass (50 % greater). Wild Ethiopian accessions 'ET531' and 'Rume Sudan' exhibited distinctive plant height responses, reflecting their unique genetic adaptation patterns to shade, with plant height and apical dominance increasing, as a photomorphogenetic response to avoid the shade. These findings offer preliminary insights to inform the selection of C. arabica genotypes suitable for coffee agroforestry systems based on juvenile plants
Impact des loranthacées sur la prolifération des agents vecteurs de zoonoses dans les plantations d'hévéa de la région du Sud Cameroun
Get PDFAu Cameroun, la culture de l'hévéa est considérée comme étant la seule source de caoutchouc naturel commercialement exploitée. Elle revêt un fort impact socio-économique car elle structure la base de l'économie pour certaines régions et permet le maintien des populations en milieu rural en leurs assurent un accès à la formation, la scolarité et la santé. Cependant, cette culture constitue un des principaux foyers de développement des parasites tels que les loranthacées qui sont responsables de nombreux dégâts liés notamment sa contribution à la prolifération des vecteurs responsables des maladies tropicales négligées telles que la dengue, le chikungunya, la fièvre jaune et la fièvre de zika donc la surveillance n'est pas encore implémenté dans le système de surveillance national. Une bonne connaissance de l'écologie des vecteurs de ces maladies, est un préalable à une meilleure planification des interventions de lutte. La présente thèse propose d'évaluer l'impact des loranthaceae parasites des hévéas dans la prolifération des agents vecteurs de zoonoses dans le Sud Cameroun. Pour ce faire une caractérisation du parasitisme des Loranthaceae dans ces plantations, ensuite une détermination de la prévalence ces maladies, suivi d'un inventaire la faune culcidienne, et enfin une évaluation la densité de ces vecteurs en fonction de la présence des Loranthaceae sur les hévéas ont été fait. Cela en conduisant des missions exploratoires auprès des structures sanitaires des zones d'étude. Les résultats préliminaires documentent comment caractériser le taux de parasitisme, l'intensité parasitaire, le taux de prévalence et d'infection des plantations, la diversité de la faune culcidienne et leur taux d'agressivité. Cela dans la perspective de renseigner des actions collectives de prévention dans le contrôle des vecteurs de zoonoses en lien avec l'hévéaculture
Early-stage impacts of conservation agriculture on soil health in a French Mediterranean irrigated system
Get PDFIn Mediterranean regions, climate change has intensified droughts and extreme weather events, accelerating soil degradation through organic matter loss, erosion, and nutrient depletion. Conservation agriculture (CA), involving practices like zero or reduced tillage, crop diversification, and soil cover maintenance, offers a resilient strategy for mitigating these challenges. This study examines the short-term effects of irrigated CA on soil health in Mediterranean conditions over 3 years (2021–2023). Using the Biofunctool® field kit (assessing carbon transformation, nutrient cycling, and structure maintenance) alongside functional indicators from the laboratory, the study compares CA with conventional tillage (CT) under different water supply methods: sprinkler, subsurface drip, and rainfed conditions. Results reveal that CA enhances soil health indicators from the first year, improving soil aggregation and carbon transformation compared to CT. By 18 months, Soil Health Index (SHI) scores were 38% higher in CA than in CT. Minimal soil disturbance in CA addressed compaction and maintained SHI 23% higher than CT. Neither the water supply mode nor temporality post-CA adoption significantly affected soil functions in the short term. The complementary use of field-based and laboratory indicators provided a holistic view of soil functionality, confirming the potential of CA to improve soil health under irrigated Mediterranean conditions
Using reflectance spectra and Pl@ntNet to identify herbarium specimens: A case study with Lithocarpus
Get PDFThe digitisation of plant collections is bringing large quantities of information into accessible electronic databases. However, in recent decades, traditional taxonomic work in collections has declined, meaning that more specimens are only determined to family or genus, particularly when lacking key identification structures. If unaddressed, large-scale digitisation risks widening the gap between well-studied species and those lacking data. Hyperspectral reflectance and computer vision are two emerging approaches for identifying species, but these have yet to be cross-compared for herbarium-based taxonomy. Using Lithocarpus species as a case study, we compared classification accuracy obtained from leaf reflectance spectra with computer vision (implemented via Pl@ntNet), a RGB (red, green, blue) image-based approach known to work well on specimens presenting reproductive structures. In the spectral approach, we assessed how much data are needed to optimise classification accuracy, how many species could be discriminated between, and whether close relatives were more frequently confounded. We found that Lithocarpus herbarium specimens were accurately identified to species from relatively small spectral datasets. Despite not incorporating reproductive structures, this was only 14% less accurate than Pl@ntNet. We suggest these rapid, nondestructive leaf reflectance measurements, paired with computer vision, could fill identification gaps in collections, particularly for specimens lacking reproductive features
Protocole expérimental de détermination de la teneur en cyanure des tubercules frais de manioc
Get PDFFood security, IMO midterm measures' impact on states and revenue distribution - Analysing synergies and risks
Get PDFAims and Objectives: The International Maritime Organization's (IMO) mid-term greenhouse gas (GHG) reduction will likely lead to an increase in transport cost, possibly affecting the imported food prices. The report identifies countries most at risk of food security deterioration due to increased import costs. - It further evaluates whether in-sector revenue distribution from a pricing mechanism can mitigate these food security risks, and whether out-of-sector distribution would be needed. Key Findings: Increased Transport Costs and Food Security: The transition to low-carbon shipping will likely raise transport costs, disproportionately impacting Least Developed Countries (LDCs) and Small Island Developing States (SIDS). This increase in transport costs could affect food security of vulnerable countries in the short term, although the effects in the long term are more uncertain. Most Vulnerable Countries Identified: Some countries such as Papua New Guinea, Haiti, Yemen, Solomon Islands, and Liberia face the greatest risks due to a combination of food import dependence, existing food insecurity, and poverty levels. Most of the highly vulnerable countries are either SIDS or LDCs. Some, although not all, are found to be more likely to see an increase in import prices in the short term than the world's average. Misalignment of Revenue Distribution and Food Security Needs: Many highly vulnerable countries which are also found more likely to see an increase in import food prices have limited capacity to absorb in-sector revenue (e.g., investments in shipping infrastructure), suggesting that restricting carbon levy revenues to the shipping sector may not effectively address food security risks. Implications: IMO's revenue distribution discussions should consider a broad range of options for distributing revenues to member states, as limiting revenues to in-sector will not be effective at addressing this food security risk negative impact on states. Given that the revenues are expected to reduce in the long term as the fleet decarbonises, it may be beneficial to vulnerable countries if revenues were used to foster a long term and structural improvement of food security in recipient countries. Methods: Developed a composite index to assess each country's vulnerability to food price increases, incorporating factors such as: - Dependence on food imports - Existing food insecurity - Poverty levels - Cross-referenced the vulnerability index with the IMO's Comprehensive Impact Assessment (CIA) to evaluate projected food price increases. Cross-referenced with the assessed countries' capacity to absorb in-sector revenue, based on factors like shipping infrastructure and existing fleet ownership
