African Mahogany Research Articles

Beyond density: Mesostructural features of impact resistant wood

Wood is a neglected impact-resistant biological material: despite its use in tools and weapons for millennia the dynamic properties and common features between species such as maple, live oak, and others are poorly understood. In this study, the impact resistance in the radial loading direction of nine tree species was studied using drop-tower testing, micro-computed tomography, and scanning electron microscopy. It was found that unlike in quasi-static conditions, density alone is a poor predictor of mechanical behavior in wood and that specific mesostructural features (interlocking grain, diffuse porous vessel distribution and intermittent rays) improved impact strength. A new, hierarchical failure of individual tracheids and the bulk fibers resembling progressive delamination of fiber-composites was observed in African mahogany, the most impact resistant tree species tested.

Nitrogen Fertilization in the Initial Growth of Khaya senegalensis A. Juss Plants Under Greenhouse Conditions

African mahogany is an exotic specie and its cultivation has increased in Brazil due to the high value of its timber on the international market. Nutrition with nitrogen is an important factor for species with high biomass production and specific studies on this species are essential. The present study aimed to assess the initial growth of African mahogany plants submitted to nitrogen fertilization. The experiment was set up and carried out in a greenhouse, with 7 dm3 plastic pots using a oxisoil sampled from the surface layer. A completely randomized experimental design was used with five treatments and six replications. The treatments consisted of five N levels: 0, 40, 80, 120 and 160 mg dm-3, using urea as the source. The following were assessed at 180 days: height, stem diameter, leaf, stem, root and total dry matter, N content in the leaves in the African mahogany leaves. The African mahogany seedlings had high N demand and responded positively to the N used and the growth variables was positive with increase in N level. However, as it presented increasing linear effect, the N level can not be estimated, that would provide the maximum initial development for this plant species.

Wastewater from swine farming in the growth and nutrition of Khaya senegalensis (DESR.) A Juss seedlings

This study evaluated the use of wastewater from swine farming in the growth and nutritional balance of Khaya senegalensis (Desr.) A. Juss. (African mahogany) seedlings. The experiment was setup in a shade house on the Professor Cinobelina Elvas Campus of the Federal University of Piauí, in Bom Jesus, in the State of Piauí, Brazil. The experimental design was completely randomised, with five concentrations of swine farm wastewater (SFW) (0, 25, 50, 75 and 100%) added to the irrigation water. The growth and nutritional balance of the seedlings were evaluated 100 days after sowing, by measuring shoot height (H), stem diameter (SD), number of leaves (NL), total chlorophyll (TC), leaf area (LA), shoot dry weight (SDW) and root dry weight (RDW), and by calculating the total dry weight (TDW), leaf (LBA), stem (SBA), and root (RBA) biomass allocation, Dickson Quality Index (DQI) and average Nutritional Balance Index (NBIm). It was found that K. senegalensis seedlings responded to the SFW, showing the best results for growth and nutritional balance at concentrations of around 50%.

Transpiration and growth of young African mahogany plants subject to different water regimes.

Timber production has been prominent in the Brazil scenario to minimize deforestation. Thus, technical information is necessary to define the productive process of the African mahogany in the Midwest region of Brazil, especially with regard to its hydric parameters. Recent studies, reported in the literature, have shown that irrigation improves the performance of young African mahogany plants in the field. Sap flow measurement can be used to estimate transpiration of perennial plants and to determine their water demand. This study evaluated the influence of two water regimes on the transpiration and growth of an African mahogany forest after irrigation has ceased. Moreover, this study also characterizes the seasonal patterns of transpiration and growth of African mahogany under these conditions. African mahogany plants with 2.5years of age were cultivated in Bonfinopolis-GO and evaluated for 2years. Treatments were IT-irrigated until 2years of age-and NIT-non-irrigated. Plant height (PH), breast height diameter (DBH), trunk volume (TRV), leaf area (LA), leaf dry matter (LDM), and transpiration (T) were monitored by heat dissipation probe (HDP) between Oct/2014 and Oct/2015. Higher growth in LA, DBH, and LDM were observed in IT. However, increase in PH and TRV was similar in both treatments. The mean annual T was similar between treatments (15.0Lm-2month-1). The highest T was recorded in October/2014 (IT = 33.0Lm-2month-1) and July/2015 (NIT = 20.5Lm-2month-1). The greater LA and water deficit blades DEF > 30mm promoted lower transpiration in the irrigated plants. Irrigation maintained plant growth in PH, DBH, and LA in the third year, even after irrigation has ceased. However, non-irrigated plants were similar in TRV (0.065m3) and transpiration rates (≈ 15Lm-2month-1). Winter transpiration (11.3Lm-2month-1) was lower than in summer (18.8Lm-2month-1) for irrigated plants and similar for non-irrigated plants (≈ 14Lm-2month-1). Based on that, in order to maintain the homogeneity of the plants, the irrigation in the first 2years of cultivation is recommended, and also, the sap flow measures presented satisfactory results regarding the determinations of the water needs of African mahogany.

Evaluation of Shear Strength and Wood Failure of Two African Mahogany Species Planted in Brazil

Abstract Interest in the wood industry of African mahogany (Khaya spp.) has increased in Brazil because of the quality of the wood and the similarity to the highly demanded Brazilian mahogany (Swie...

Genetic diversity and differentiation among the species of African mahogany (Khaya spp.) based on a large SNP array

The genus Khaya includes some of the highest-value timber species in natural forests in Africa, which are under heavy exploitation pressure. Genetic identification of Khaya species is important to confirm the taxonomic classification for biodiversity conservation purposes and as a forensic tool aiding law enforcement in the fight against illegal logging. We collected samples from a total of 2222 trees belonging to five or six (depending on classification) different Khaya species (K. ivorensis, K. anthotheca/K. nyasica, K. grandifoliola, K. senegalensis, K. madagascariensis). Representative sampling was conducted over the natural ranges of all sampled Khaya species, in humid tropical forest and savanna zones. We genotyped individuals based on 101 molecular markers (67 nuclear, 11 chloroplast and 22 mitochondrial SNPs, 1 chloroplast indel). Bayesian clustering produced three main genetic groups assigning all K. ivorensis and all K. senegalensis trees, respectively, in two different clusters and all remaining individuals in a third cluster. Genetic self-assignment tests with all 101 SNPs had success rates of 97–100% for all species except for K. nyasica and K. madagascariensis, which could not be clearly distinguished from each other. A success rate for species identification nearly as high was observed using a subset of 15 highly differentiated SNPs. There was only very little evidence for hybridization among species and the vast majority (> 97%) of individuals were assigned to the same species group as identified based on morphological characters.

Des confusions entre espèces préjudiciables à la gestion durable des essences forestières : l’exemple des acajous d’Afrique (Khaya, Meliaceae)

Les espèces du genre Khaya procurent l’un des bois les plus prisés du continent africain. Elles sont commercialisées sous l’appellation « acajou d’Afrique » depuis environ deux siècles. En Afrique continentale, on reconnaît actuellement quatre espèces morphologiquement proches : Khaya anthotheca, K. grandifoliola, K. ivorensis et K. senegalensis. Le nombre de taxons du genre Khaya a varié au cours du temps et la délimitation de ces taxons n’est pas sans avoir des implications sur les stratégies de conservation et de gestion durable des espèces. L’objectif du travail présenté ici est de s’assurer de la délimitation de ces espèces sur la base d’un bilan des connaissances actuelles en taxonomie, génétique, écologie et chimiotaxonomie. Les données disponibles ne permettent pas toujours de séparer sans ambiguïté les quatre acajous d’Afrique continentale. Elles permettent toutefois d’avancer que K. ivorensis, K. grandifoliola et K. senegalensis seraient des espèces à part entière mais dont les limites taxonomiques doivent encore être précisées. Khaya nyasica serait également une espèce qui devrait être séparée de K. anthotheca. Au sein de cette dernière, plusieurs chémotypes ont été identifiés, ce qui suggère que ce taxon pourrait recouvrir un ensemble plus complexe d’au moins deux autres taxons dont le rang spécifique ou sous-spécifique reste à préciser. Des recherches morphométriques, génétiques et écologiques doivent être développées afin de clarifier le statut systématique et l’histoire évolutive de ces divers taxons, en vue de formuler des recommandations appropriées pour la gestion durable des acajous d’Afrique.

Phytotherapy and Polycyclic Logging: Implication on Genetic Multiplicity and Diversity of African Mahogany in Tropical Rainforest

There are over 8,000 globally threatened tree species. For each species, there is a different story behind why they are threatened and what values we stand to lose if we do not find the means to save them. Mahogany, a member of Meliaceae, is a small genus with six species. Its straight, fine and even grain, consistency in density and hardness makes it a high valued wood for construction purposes. The bitter bark is widely used in traditional medicine in Africa. The high demand for bark has also led to the total stripping of some trees, complete felling of larger trees to get the bark from the entire length of the tree and bark removal from juvenile trees. These species are now threatened with extinction due to selective and polycyclic logging, and also excessive bark removal. The natural regeneration of mahogany is poor, and mahogany shoot borer Hypsipyla robusta (Moore) attacks prevent the success of plantations within the native area in West Africa. In developing countries, most of the Khaya species exists in the wild state; therefore, the regeneration and long-term conservation are at the mercy of the vagaries of nature and the profit driven herb collectors and timber merchants. It becomes urgently necessary by government of developing countries to place ban on further harvesting of mahogany species to allow the remaining few trees of mahogany in the forest to recuperate and produce substantial seeds for regeneration.

SOBREVIVÊNCIA E CRESCIMENTO INICIAL DE ESPÉCIES FLORESTAIS EM SISTEMA DE INTEGRAÇÃO LAVOURA-PECUÁRIA-FLORESTA NO LESTE DA AMAZÔNIA

O desflorestamento para o estabelecimento de projetos agrícolas na Amazônia brasileira tem resultado em vastas áreas degradadas. Desta forma, sistemas de interação lavoura-pecuária-floresta (iLPF) tornam-se uma alternativa essencial para conciliar a produção agrícola com a sustentabilidade. Assim, objetivou-se com este trabalho avaliar o crescimento inicial de três espécies florestais: mogno africano (Khaya ivorensis), eucalipto urophylla (Eucalyptus urophylla) e paricá (Schizolobium parahyba var. amazonicum) para sua adaptação em sistemas de iLPF sobre áreas degradadas, no Leste da Amazônia. As avaliações de performance das espécies estudadas foram feitas por meio de um experimento conduzido na Fazenda Vitória, município de Paragominas, Estado do Pará, Brasil. No experimento foram comparadas as performances das espécies em sistema de iLPF e em monocultivo. As três espécies florestais mostraram crescimento satisfatório em altura e diâmetro em ambos os tratamentos. O mogno apresentou maior crescimento em altura e DAP no sistema iLPF enquanto que o eucalipto e o paricá tiveram maior crescimento somente em altura no sistema de monocultivo e nenhuma diferença em DAP. O paricá apresentou a maior percentagem de sobrevivência, seguido por mogno e eucalipto.

Vulnerability of African mahogany to cattle predation in a silvipastural system

Abstract: The objective of this work was to evaluate the incidence and intensity of damages caused by cattle to African mahogany (Khaya grandifoliola) and this species vulnerability in the silvipastural system. The trees were planted in single lines, in a 20x2 m arrangement. In the third year, cattle were introduced in the area. Three classes of damage intensity were established: low, medium, and high. Damages to tree barks showed the highest incidence, followed by damages to wood. The species is vulnerable to bark chewing by cattle, with damages of medium and high intensities.

First Report of Parasaissetia nigra in Khaya ivorensis Seedlings in Brazil

ABSTRACT The objective of this research is to report the occurrence of the nigra scale Parasaissetia nigra (Nietner, 1861) (Hemiptera: Coccidae) in mahogany (Khaya ivorensis) seedlings in a forest nursery in Mato Grosso state. In September 2017, the infestation was detected on the leaves and branches of the plants, causing injury and the death of the apical meristem and leaf curling symptoms. It was verified the symbiosis of P. nigra with ants, due to the sugary exudate. The chemical control was performed with insecticidal syrup and the proposed method was effective. This was the first reported occurrence of P. nigra on African mahogany in Brazil.

Shelf life and proximate composition of tomato (<i>Solanum</i> <i>lycopersicum</i> L.) fruits as influenced by storage methods

Tomato (Solanum lycopersicum L.) is a perishable fruit with a relatively short shelf life. The quality and nutritional value of fresh produce like tomato are affected by postharvest handling and storage conditions. This work aimed at evaluating the effects of storage methods on the shelf life and proximate composition of four varieties of local (Hausa and Yoruba Nigeran land races) and improved (Tropimech and Roma VF) tomato. The mature green fruits of each variety were manually harvested and stored. Three storage structures were employed viz., plastic crate, raffia basket and pot-in-pot refrigerator. Three botanical preservatives (plant byproducts) were used viz., wood ash from shea butter tree (Vitellaria paradoxa), sawdust from African mahogany (Khaya ivorensis) and rice (Oryza sativa) straw. Each preservative was mixed with each variety of tomatoes in 1:2 ratios (1.75 kg of preservative to 3.50 kg of fruits) in each storage device. Shelf life was determined when more than 50% of fruits showed symptoms of shrinkage or spoilage (fruit rot). Proximate analysis was carried out for the amounts of moisture, ash, crude fibre, crude protein, crude lipid and carbohydrate in the stored fruits. Shelf life of all the varieties was enhanced by pot-in-pot refrigerator. Proximate analysis revealed that moisture was highest, followed by carbohydrate in all varieties irrespective of storage structure and preservative. The improved varieties showed higher values of all the proximate parameters when compared to the two local varieties (Hausa and Yoruba).Out of the storage structures, pot-in-pot refrigerator seems to be more suitable to enhance shelf life of tomato fruits without compromising its quality.

Volume equations for Khaya ivorensis A. Chev. plantations in Brazil.

African mahogany (Khaya spp.) plantations are in expansion in Brazil and in the world. This fact justifies the need for studies related to its growth and yield. This paper aimed to evaluate the performance of single-entry and double-entry models for estimating merchantable and total volume for Khaya ivorensis plantations before the first thinning (7 years) and expected final cut (15 years). Volume data was from 100 and 46 trees in Minas Gerais and Pará states, respectively, by using an electronic dendrometer (Criterion RD 1000). Observed volumes were calculated by Smalian's formula. To validate the optical dendrometer, 10 trees were felled and had their volume measured, and compared with the volumes measured indirectly. The results showed that observed and estimated volumes were statistically equal, and that double-entry models were more precise than single-entry models. Schumacher and Hall model was the best equation to estimate merchantable volume for first thinning and for final cut in Minas Gerais stands. Spurr logarithmized model was the best equation to estimate total volume for first thinning and Spurr model for final cut in Pará stands. All chosen equations can be used to quantify merchantable and total volumes of Khaya ivorensis grown under similar conditions.

Aggregation, carbon, and total soil nitrogen in crop-livestock-forest integration in the Eastern Amazon

ABSTRACT Sustainable agricultural production systems can improve physical attributes of soil as well as increase carbon and nitrogen stocks in soils. The objective of this study was to evaluate changes in the stability of soil aggregates and contents and stocks of carbon and nitrogen after the conversion of native forest to crop-livestock-forest integration systems in the region of Western Pará. Soil samples from five management systems (including a control) were collected at three depths in a randomized block design, with five replications. The stability of the aggregates, soil density, particle density, and total soil porosity, as well as total carbon and nitrogen and their respective stocks were evaluated. The native forest had the highest percentages of macroaggregates, followed by the integration system with African mahogany. At a depth of 0-0.10 m, the contents and stocks of carbon were higher in the agricultural area and in the integration system with cumaru, whereas nitrogen contents and stocks were higher in the native forest, followed by the integration systems with mahogany and cumaru. Compared to the other systems, the pasture area stored more carbon at depths of 0-0.10 and 0.10-0.20 m.

VARIÁVEIS MORFOMÉTRICAS DE TRÊS ESPÉCIES FLORESTAIS EM SISTEMA AGROFLORESTAL

Este trabalho teve como objetivo a análise morfométrica de três espécies florestais: Mogno Africano (Khaya ivorensis), Seringueira (Hevea brasiliensis) e Teca (Tectona grandis). O trabalho foi realizado no município de Monte Alegre – PA em junho de 2017 durante três dias, em uma área de 90 hectares, dividida em 6 Sistemas Agroflorestais (SAFs), onde foram amostrados 20 indivíduos por sistema. Para análise morfométrica, calculou-se a Projeção de Copa (A), Volume de Copa (VC), Proporção de Copa (PC), Grau de Esbeltez (GE), Índice de Saliência (IS), Índice de Abrangência (IA), Formal de Copa (FC), Incremento Médio Anual de Altura (IMA - HT) e Incremento Médio Anual de Diâmetro (IMA - DAP). Observou-se que o Mogno Africano possui maior valor de altura comercial (6,81 m) e diâmetro (0,33 m), e a Seringueira apresentou maiores valores de IMA – HT (2,41 m/ano), IMA – DAP (0,035 m/ano), IC (9,82 m), CC (12,05 m) e DC (8,85 m). As três espécies estudadas não apresentaram diferenças significativas nos valores de GE, FC, IS. A Teca obteve maior IA (0,56 m/m). Devido aos bons resultados de IMA, a Seringueira pode ser utilizada em reflorestamento em curto prazo. O Mogno Africano e a Teca demonstraram aptidão a plantios adensados, consorciados ou não.PALAVRAS-CHAVE: Agrossilvicultura, Morfometria, Sistema Agroflorestal.

Effects of the urban heat island and climate change on the growth of Khaya senegalensis in Hanoi, Vietnam

BackgroundRecent projections expect that Vietnam will be affected most severely by climate change with higher temperatures, more precipitation and rising sea levels. Especially increased temperatures will worsen the situations in cities, amplifying the urban heat island effect. Green infrastructures, i.e. urban trees are a common tool to improve the urban micro-climate for humans. Vital and well growing trees provide greatest benefits such as evaporative cooling, shading, air filtering and carbon storage. However, urban tree growth is often negatively affected by urban growing conditions such as high soil sealing with compacted tree pits providing small growing spaces with limited water, nutrient and oxygen supply, further warm temperatures and high pollution emissions. This study analyzed the growth of urban and rural African mahogany (Khaya senegalensis (Desr.) A. Juss.) trees in the city of Hanoi, Vietnam and the effects of the surrounding climate conditions on tree growth.ResultsThe results showed that rural African mahogany trees grew better than trees situated in the city center, which is contrary to other results on tree growth of temperate and subtropical cities worldwide. Moreover tree growth was similar regardless of the time of growth. Other results regarding stem growth of African mahogany located in different areas of Hanoi (east, west, north, city center) revealed a better growth in the northern and western outskirts of the city compared to the growth of trees in the city center.ConclusionAfrican mahogany trees in the urban centers of Hanoi showed a decreased growth compared to rural trees, which was likely induced by a low ground-water level and high pollution rates. In view of climate change and global warming, the decreased tree growth in the city center may also affect tree service provision such as shading and cooling. Those climate mitigation solutions are strongly needed in areas severely affected by climate change and global warming such as Vietnam.

Modeling the height–diameter relationship and volume of young African mahoganies established in successional agroforestry systems in northeastern Brazil

The aim of this study was to fit and select height–diameter and stem volume equations for two African mahogany species (Khaya ivorensis and Khaya anthotheca) in the initial development phase (between 2 and 5 years old), established in agroforestry systems in northeastern Brazil. We used linear and nonlinear models to predict the total height (h) and stem volume (v), based on data from forest inventories and stem measurements of standing trees. We tested the following hypotheses: (1) the simple linear model is the most accurate to estimate the total height of young African mahogany trees in relation to different types of height–diameter models (linearized, nonlinear and those with transformed variables); (2) simple and double-entry stem volume models have the same precision in estimating the individual volume of young African mahogany trees. The results showed that the simple linear height–diameter model was most accurate to estimate the height of both African mahogany species. The age’s effect (young trees) and probably the predominantly monopodial development of the Khaya spp. trees sampled were discussed as the causes of the linear nature of the models that best described the height–diameter relationship. The stem volume equations for Khaya ivorensis and Khaya anthotheca were well adjusted. However, the double-entry Spurr’s model was more accurate than the other models for both species. Furthermore, for the Khaya ivorensis, the one-entry (diameter) Husch’s model generated similar stem volume estimates to Spurr’s model.

CONDUCTIVITY TO RUST IN COFFEE UNDER DIFFERENT WOODEN AND FRUIT TREE INTERCROPPING SYSTEMS

The coffee intercropping with fruit and wooden species of economic value has been presented as a viable alternative for coffee cultivation in order to mitigate adverse environmental conditions for coffee trees, among other factors. Adapting the crop management to the new conditions stablished by the system is fundamental to obtain success on intercropping. One of the most serious diseases for the crop is the rust caused by Hemileia vastatrix ., which may have its severity increased in function of the microclimate conditions provided by the trees. In this sense, the disease behavior under different intercropping systems and consequent different need to adapt the control measures when compared to the cultivation in full sun should be investigated. The present study was conducted aimed to verify the impact of tree systems composed by three wooden species, Cedar ( Acrocarpos fraxinifolius ), African mahogany ( Khaya ivorensis ), Teak ( Tectona grandis ) and two species of fruit trees, avocado ( Persea Americana ) and macadamia ( Macadamia integrifolia ) planted in different spacing over the occurrence and evolution of rust.It was possible to observe that coffee rust began to progress in the coffee plants from the month of February reaching a peak in September in all the treatments. Differences were observed in the progress curves of the disease, especially in the species that presented larger canopy such as avocado. Further studies are suggested with the purpose of establishing the microclimatic changes provided by the cultivation of different wooden and fruit species in intercropping with coffee, according to the dynamics of the climate and their development.

Efeitos da fertilização potássica no crescimento inicial de <em> Khaya senegalensis </em> A. Juss no bioma Cerrado

No presente estudo, objetivou-se avaliar o crescimento inicial de mudas de mogno-africano (Khaya senegalensis A. Juss.) adubadas com diferentes doses de potássio. O experimento foi realizado em casa de vegetação, em recipiente de plástico com capacidade para 7 dm3 e utilizando como substrato o solo classificado como Latossolo Vermelho-Amarelo distrófico. O delineamento experimental utilizado foi inteiramente casualizado, com cinco tratamentos e cinco repetições, totalizando 25 unidades experimentais. Os tratamentos constituíram-se de cinco doses de K: 0; 40; 80; 120 e 160 mg dm-3, utilizando para aplicação o cloreto de potássio. Aos 150 dias, foram aferidos a altura da planta, o diâmetro do coleto e a massa de matéria seca de folhas, caule, raiz e massa de matéria seca total. Constatou-se que, as doses crescentes de potássio não promoveram aumento no crescimento das plantas. O mogno-africano apresentou baixa exigência em potássio nas fases iniciais de desenvolvimento para a condição edafoclimática no local do experimento.

A comparison of diameter distribution models for Khaya ivorensis A.Chev. plantations in Brazil

The purpose of this study was to compare Beta, Gamma, Johnson's SB and Weibull functions fitted by different methods for describing the horizontal structure of Khaya ivorensis (African mahogany) plantations in Brazil. The database comprised 128 plots from six plantations at varying ages. The function fits were compared using the Kolmogoroff–Smirnoff test, mean bias and mean absolute error for the number of trees and basal area per hectare per diameter class. Johnson's SB outperformed the other functions, although all functions provided an adequate fit. The best methods were method of moments and maximum likelihood fitted using 25% of the minimum observed diameter as the location parameter for the Johnson's SB function. The errors were greater in diameter classes with higher frequencies. Location and scale parameters were highly correlated with mean diameter and age for the Weibull and Johnson's SB functions, respectively, which is convenient for diameter prediction. Gamma's scale parameter had medium correlation with age. Beta's parameters had low correlation with stand attributes assessed.