Miombo Tree Species Research Articles

Mapping dominant tree species of miombo woodlands in Western Tanzania using PlanetScope imagery

Mapping dominant tree species in miombo woodlands is essential for enhancing their monitoring and management. We evaluated PlanetScope imagery to map Julbernardia globiflora, Brachystegia spiciformis, and Pterocarpus tinctorius in Tongwe Forest Reserve, Tanzania. The study assessed the effectiveness of PlanetScope bands in discriminating tree species and investigated how different months/seasons influenced tree species classification. Optimal months (seasons) and spectral bands were selected using Principal Component loading, temporal pattern analysis, mean decrease in accuracy, and mean decrease Gini techniques. Random forest classification was employed for tree species classification, and accuracy was assessed using an error matrix. The study identified March, July, and September as optimal months for acquiring imagery, with effective bands including blue, green-1, green, yellow, red, and red-edge. July and September imagery in the dry season achieved higher overall accuracies of 65% and 69%, respectively, while March imagery in the wet season reached 55%. The highest overall accuracy of 72% was achieved using images from different seasons. Producer’s accuracy was highest for Brachystegia spiciformis (79%) and Julbernardia globiflora (95%), whereas Pterocarpus tinctorius had lower accuracy (25%). User’s accuracy varied with 74% for Brachystegia spiciformis, 70% for Julbernardia globiflora, and 67% for Pterocarpus tinctorius. Mapping accuracy was notably high for Brachystegia spiciformis and Julbernardia globiflora, reflecting their high sample size (dominance) and distinct phenology. The yellow and red bands were particularly effective in distinguishing miombo tree species demonstrating PlanetScope’s capability. Future research should focus on scaling up PlanetScope’s application for broad miombo tree species mapping.

Evaluation of field survival and growth to support the restoration of four valuable Miombo tree species

Understanding of right nursery practices is important for the production of high quality seedlings and successful restoration of trees with limited natural regeneration and/or on-farm tree planting. We evaluated the effects of nursery practices on field tree survival and growth in two trials in Morogoro, Tanzania: 1) shading regime, polythene tube size with four Miombo tree species i.e. Albizia harveyi, A. versicolor, Diplorhynchus condylocarpon and Pterocarpus angolensis; and 2) soil mixture and mycorrhizae/rhizobia inoculation with three Miombo tree species i.e. A. versicolor, D. condylocarpon and P. angolensis. There were no significant effects of the shading regime and polythene tube size on the survival, root collar diameter and height for all studied tree species. Almost all P. angolensis trees died after one year but the overall tree survival was good (>80 %) for the other tree species. Tree survival was always higher in nursery soil mixture S5 (0: 0: 1 sand: cow manure: soil) for D. condycarpon and at the early stages for P. angolensis. Mycorrhizae/rhizobia inoculation reduced tree survival of D. condylocarpon but not for other tree species. Interactions of soil mixture and mycorrhizae/rhizobia were only significant for D. condylocarpon and only with soil mixture S6 (1: 2: 3 sand: cow manure: soil). The advantages of medium and large polythene tubes on tree survival and growth in the field are dismissed in favour of small polythene tubes (10 x 10 cm). Nursery forest top soil alone is recommended for P. angolensis and D. condylocarpon. Albizia harveyi and A. versicolor can be grown in any of the soil mixtures tested. Testing the effect of nursery techniques on the field performance of these tree species in dry areas or poor soils, and for enrichment planting is recommended to enhance restoration of Miombo woodland.

Ring data provide management clues and pinpoint climate drivers of growth in two species of miombo trees (Brachystegia spiciformis, Julbernardia paniculata)

Tree-ring studies are still lacking in tropical African forests. This is the case in the seasonally dry miombo forests located in Southern Africa. In the Angolan miombo, subject to intense charcoal exploitation, tree-ring data is urgently needed to estimate the age at which the minimum permitted cutting diameter is reached. Further, climate-growth relationships must be also investigated to understand how major miombo tree species respond to climate constraints and teleconnections such as the El Niño Southern Oscillation (ENSO). To achieve both aims, we studied radial growth data of two miombo tree legume species (Brachystegia spiciformis, Julbernardia paniculata) in wet (Bailundo) and dry (Caála) Angolan sites using dendrochronological methods. Both species have diffuse porous wood and conspicuous ring boundaries delimited by terminal parenchyma in latewood. Sampled individuals had ages (at 1.3 m) between 28 and 34 years with ring widths ranging 3.8–4.3 and 5.5–6.0 mm in dry and wet sites, respectively. In the wet (dry) site, Brachystegia and Julbernardia reached maximum diameter increment rates of 1.05–1.32 (0.74–0.91) cm yr−1 at an age of 12 (14−20) years. Both species took 12–15 years to reach a minimum cutting diameter of 15 cm. The growth variability among conspecific individuals was lower in the dry (mean standard error, 1.4 cm) than in the wet site (mean standard error, 2.7 cm). We also found that wet conditions from November to February, often linked to El Niño events, enhanced growth for both species, with greater growth consistency among individuals and higher sensitivity to climate found in the dry site. This information may help to estimate the optimal age for minimum cutting diameter that guarantees the sustainable use of charcoal and fuelwood.

Use of Multi-Date and Multi-Spectral UAS Imagery to Classify Dominant Tree Species in the Wet Miombo Woodlands of Zambia.

Accurate maps of tree species distributions are necessary for the sustainable management of forests with desired ecological functions. However, image classification methods to produce species distribution maps for supporting sustainable forest management are still lacking in the Miombo woodland ecoregion. This study used multi-date multispectral Unmanned Aerial Systems (UAS) imagery collected at key phenological stages (leaf maturity, transition to senescence, and leaf flushing) to classify five dominant canopy species of the wet Miombo woodlands in the Copperbelt Province of Zambia. Object-based image analysis (OBIA) with a random forest algorithm was used on single date, multi-date, and multi-feature UAS imagery for classifying the dominant canopy tree species of the wet Miombo woodlands. It was found that classification accuracy varies both with dates and features used. For example, the August image yielded the best single date overall accuracy (OA, 80.12%, 0.68 kappa), compared to October (73.25% OA, 0.59 kappa) and May (76.64% OA, 0.63 kappa). The use of a three-date image combination improved the classification accuracy to 84.25% OA and 0.72 kappa. After adding spectral indices to multi-date image combination, the accuracy was further improved to 87.07% and 0.83 kappa. The results highlight the potential of using multispectral UAS imagery and phenology in mapping individual tree species in the Miombo ecoregion. It also provides guidance for future studies using multispectral UAS for sustainable management of Miombo tree species.

Effect of fibre and vessel biometry on wood combustibility of native Miombo tree species

Fibres and vessels represent the largest proportion of anatomical elements in hardwood tree species. They exert significant effects on various properties of the wood, which, consequently, have several implications for the use of the wood. However, the effect of these elements on wood combustion behaviour is still poorly analysed in the literature. The present study aimed to evaluate the effect of fibre and vessel biometry on wood combustibility. The length, width and cell wall thickness of fibre, diameter of the lumen, and length and width of vessels were measured from five native Miombo tree species in Mozambique, namely Brachystegia boehmii Taub., Brachystegia spiciformis Benth., Julbernardia globiflora (Benth.) Troupin, Parinari curatellifolia Planch. ex Benth. and Uapaca kirkiana Müll. Arg. The fibre quality index and cell wall thickness were determined based on fibre biometry. The flexibility coefficient and the wall fraction are inversely proportional indices and individually affected most of the combustion parameters. Wood ignition is driven by large lumen diameter and flexibility in fibres. In addition, cell wall thickness and a larger wall fraction increase wood combustion.

Regeneration capacities of woody species biodiversity and soil properties in Miombo woodland after slash-and-burn agriculture in Mozambique

Miombo woodland is the dominant tropical dry forest formation in Africa. Its importance for local populations’ livelihoods and increased pressure has turned the spotlight on this ecosystem, now considered one of the five global wilderness areas prioritized for conservation and restoration. Forest regeneration is a key to restoring ecosystem services, but the characteristics, conditions and dynamics of this specific biome remain largely understudied. The aim of this study was to analyze the current status and evolution of woody species biodiversity, stand structure and soil properties of regrowth plots after slash-and-burn farming in Mozambique. Our survey focused on the area surrounding Gilé National Park in Mozambique, which is dominated by a mosaic of vegetation including mature Miombo woodland, grassland, cropland, and land abandoned after slash-and-burn cycles. We sampled 20 plots in mature woodland and 36 plots in a chronosequence of Miombo regrowth from 1 to 35 years old, grouped in four age classes: 4–6, 8–12; 20–25 and 30–35 years. We observed that woody species richness and diversity increased with time after abandonment until similar values to those in mature woodlands were reached between 20 and 25 years later. Despite the presence of the dominant Miombo tree species belonging to the genera Julbernardia and Brachystegia, after 20–35 years of regeneration species composition remained different from that of mature woodlands. Mean DBH, tree height, and carbon stock increased while tree density decreased along the chronosequence. Tree density and tree carbon stocks in 30–35-year-old Miombo regrowth exceeded those of mature woodland. Soil C stock increased during vegetation regeneration after abandonment. Results suggest that two or three decades are necessary to reach values similar to those of mature woodland. Overall, these findings show that the region has a high regeneration capacity in terms of woody species diversity and soil properties but that disturbances have a long term effect on species composition and stand structure, underlining the importance of integrated landscape management to enhance the provision of ecosystem goods and services.

Dry and wet miombo woodlands of south-central Africa respond differently to climate change.

It is important to understand how species distributions will shift under climate change. While much focus has been on species tracking temperature changes in the northern hemisphere, changing precipitation patterns in tropical regions have received less attention. The aim of the study was to estimate the current distribution of wet and dry miombo woodlands of sub-Saharan Africa and to predict their distributions under different climate change scenarios. A maximum entropy method (Maxent) was used to estimate the distributions and for projections. Occurrence records of dominant tree species in each woodland were used for modeling, together with altitude, soil characteristics, and climate variables as the environmental variables. Modeling was done under all four representative concentration pathways (RCPs) and three general circulation models. Three dominant tree species were used in models of dry miombo while seven were used for wet miombo. Models estimated dry miombo to cover almost the entire known distribution of miombo woodlands while wet miombo were estimated to predominate in parts of Angola, southern Democratic Republic of Congo, Malawi, Tanzania, Zambia, and Zimbabwe. Future climate scenarios predict a drier climate in sub-Saharan Africa, and as a result, the range of dry miombo will expand. Dry miombo were predicted to expand by up to 17.3% in 2050 and 22.7% in 2070. In contrast, wet miombo were predicted to contract by up to - 28.6% in 2050 and - 41.6% in 2070. A warming climate is conducive for the proliferation of dry miombo tree species but unfavorable for wet miombo tree species.

Inter-annual growth response of three Miombo tree species to climatic effects

Miombo woodlands cover a large part of Southern Africa and contribute an important wood source for the local wood industry. The already observed and further predicted changes in climatic patterns can be expected to affect the wood properties of Miombo tree species. The diameter growth response to climatic variables related to water availability and temperature of three Miombo woodland tree species (Brachystegia spiciformis, Burkea africana and Isoberlinia angolensis) was analysed using 245 trees samples in three climatic zones in Zambia. Sites were chosen to represent the range of site conditions under which these species grow in the Miombo woodlands of Zambia. The study sites differed in moisture availability and average temperature, as indicated by De Martonne’s aridity index. Tree-ring width correlated with site conditions and differed significantly between sites. A positive correlation was found between mean annual precipitation and annual ring width, as well as growth variation, while growth was almost non-responsive to temperature variations. For all three species, trees growing on the outer limits of the species’ range were found to be more responsive and sensitive to variability in annual rainfall than those growing under optimal conditions. All three species showed significant variation in inter-annual ring width with environmental conditions. Water availability was found to have a much larger effect than temperature, especially on drier sites.

Climate change threatens some miombo tree species of sub-Saharan Africa

Climate change is affecting the distribution of species globally. Predicting the distribution of species under climate change is important for conservation of biodiversity. The aim of this research was to model the current distribution of miombo woodlands of sub-Saharan Africa using seventeen miombo tree species, and to project their distributions under different climate change scenarios. A maximum entropy method, Maxent, was used to model the distributions of the seventeen representative tree species, Albizia antunesiana, Afzelia quanzensis, Baikiaea plurijuga, Brachystegia bakeriana, Brachystegia boehmii, Brachystegia longifolia, Brachystegia microphylla, Brachystegia spiciformis, Brachystegia utilis, Cryptosepalum exfoliatum, Guibourtia coleosperma, Isoberlinia angolensis, Julbernadia globiflora, Julbernadia paniculata, Pericopsis angolensis Pterocarpus angolensis, and Pterocarpus rotundifolius. A total of 3 429 occurrence records, nineteen bioclimatic variables, monthly precipitation, minimum and maximum temperatures, soil characteristics and altitude were used in modeling. Distributions were hindcasted to the Mid-Holocene and forecasted to 2050 and 2070 under all four Representative Concentration Pathways (RCPs). Hindcasting showed that ranges for A. antunesiana, B. bakeriana, B. boehmii, C. exfoliatum, G. coleosperma and Pterocarpus angolensis were larger in the Mid-Holocene than they are currently, while the ranges of the other species were constricted during this period. When forecasted, range contraction was observed for nine species, A. quanzensis, A. antunesiana, B. microphylla, B. spiciformis, B utilis, C. exfoliatum, J. globiflora, Pericopsis angolensis and P. rotundifolius. Range expansion was observed in the other eight species. Range contraction was acute in 2070 under RCP8.5 for A. quanzensis (-13%), A. antunesiana (-15%) and B. microphylla (-14%). Species whose forecasted ranges contracted should be prioritized for mitigation against climate change. All species should be protected from anthropogenic threats since most are unsustainably harvested.

Dynamic Patterns of Trees Species in Miombo Forest and Management Perspectives for Sustainable Production—Case Study in Huambo Province, Angola

This paper aims to assess important forest parameters, including tree density, diameter at breast height (DBH), and age distribution, investigate the dynamic growth of miombo tree species, and employ this information to design a management framework in miombo forests. The delineation of the management zones was based on unsupervised land cover classification that began with three zones where ground data was collected and increased to five zones. Eighteen circular plots (25.2 m radius) were randomly distributed over the study areas to assess the current situation and potential growth patterns for each species. The patterns of the six most representative tree species of miombo in Angola were described and we used KORFiT 2.4 software to fit data and develop growth curves for at least three miombo species. Growth function fitness was evaluated by root mean squared error (RMSE), coefficient of determination (R2), significance of the parameters (p < 0.05), and Akaike’s information criterion (AIC). The diameter distribution of miombo tree species resembled a typical distribution of uneven-aged forest stands; higher DBH classes had lower abundances of tree species. Logistic and Gompertz growth functions were the best fits for miombo tree species. Brachystegia spiciformis Benth., is suggested as a potential species for timber management in the region because they displayed high growth potential to more quickly reach an assumed minimum DBH of 20 cm. This study concluded that miombo forest stands present an irregular structure in which DBH distribution illustrated only two patterns: many small stems and a bimodal forest structure.

English

Miombo woodlands cover about two thirds of Mozambique national territory. They provide a wide collection of goods and services to the formal and informal economies. A review on the traditional uses of 15 Miombo tree species in human and animal health, as well as the status of research towards the identification of bioactive compounds is presented. Among the 15 species selected, 12 have been screened for their biological activity and/or pharmacological properties and/or toxicity. The information gathered in this work is a key to further exploit potential new uses and future opportunities for research and valorization of the selected species. Key words: Ethnobotanical, medicinal plants, Miombo woodlands, non timber forest products.

Nest sites selection by sympatric cavity-nesting birds in miombo woodlands

Deforestation and habitat fragmentation have long been known as drivers of wildlife depletion but information on their specific impacts on cavity-nesting birds in the miombo woodlands has been lacking. A comparative study of disturbed and undisturbed sites was conducted in miombo woodlands of Zambia to assess impacts of environmental stressors on birds. Foot patrols were employed to locate, identify and count host trees and cavities for cavity-nesting birds on twenty 200 m × 200 m sample plots. Undisturbed forests had three times more cavities (the nesting sites for birds), while there were 24.6% fewer abandoned cavities in undisturbed forests than in disturbed forests. The rate of cavity abandonment was about twice as high in human-dominated forests compared to undisturbed forests (61.3% c.f. 31.9%). Cavity-nesting birds preferred larger (> 36.0 cm diameter at breast height) and taller (> 5.0 m) trees for nest placement, especially in human-dominated forests. A number of cavity-nesting birds preferred Brachystegia spiciformis (zebrawood), Julbernadia paniculata (munsa), Parinari curatellifolia (mobola-plum) and Uapaca kirkiana (mahobohobo) as host trees to 14 other miombo tree species. Arnot’s Chat (Myrmecocichla arnoti) had a wider selection of host trees for cavity-nesting than the other 40 cavity-nesting birds in the study areas. Anthropogenic activities such as uncontrolled firewood collection, wild fires, logging, and land clearing for agriculture negatively influenced wood abundance and diversity, with potential implications for persistence of cavity-nesting birds. The negative impacts of anthropogenic activities could be counteracted by conservation strategies such as implementation of sound forest policies, integrative land use practices, sustainable livelihood security and stakeholders’ awareness of the need to safeguard forest-dependent avifauna.Conservation implications: This comparative study unravels specific anthropogenic impacts on the cavity-nesting birds in the miombo woodlands, which would be relevant for designing and implementing targeted biodiversity conservation interventions against negative local environmental values and attitudes that support rural development on the expense of conservation of biodiversity such as birds.

Does the abundance of dominant trees affect diversity of a widespread tropical woodland ecosystem in Tanzania?

Abstract:Dominant woody species can determine the structure and composition of a plant community by affecting environmental conditions experienced by other species. We explored how dominant tree species affect the tree species richness, diversity, evenness and vertical structural heterogeneity of non-dominant species in wet and dry miombo woodlands of Tanzania. We sampled 146 plots from eight districts with miombo woodlands, covering a wide range of topographic and climatic conditions. We recorded 217 woody plant species belonging to 48 families and 122 genera. Regression analysis showed significant negative linear associations between tree species richness, relative species profile index of the non-dominant and the relative abundance of the dominant tree species (Brachystegia spiciformisandBrachystegia microphyllain wet, andBrachystegia spiciformisandJulbernardia globiflorain dry miombo woodlands). Shannon diversity and evenness had strong non-linear negative relationships with relative abundance of dominant tree species. A large number of small individual stems from dominant and non-dominant tree species suggesting good regeneration conditions, and intensive competition affecting survival. We suggest that dominant miombo tree species are suppressing the non-dominant miombo tree species, especially in areas with high recruitments, perhaps because of their important adaptive features (extensive root systems and ectomycorrhizal associations), which enhance their ability to access limited nutrients.

Early growth and survival of three miombo woodland indigenous fruit tree species under fertilizer, manure and dry-season irrigation in southern Malawi

Although a large number of miombo tree species bear edible fruits which are important sources of vital nutrients and incomes to rural households, their conservation and cultivation remain challenging because of lack of information on their ecology and management. Therefore, the objective of this study was to evaluate the effects of fertilization, manure application and dry-season irrigation on the early growth and survival of the miombo fruit tree species, Uapaca kirkiana, Sclerocarya birrea and Vanguaria infausta with Mangifera indica as relative control. At 33 months after planting, growth and survival of U. kirkiana and S. birrea were lower in plots that received fertilizer, compost and irrigation compared with those that did not. The best growth and survival in U. kirkiana was obtained when irrigation was applied with neither fertilizer nor manure. The best growth in S. birrea was recorded where plants received irrigation without fertilizer and manure, while survival was highest when none of the treatments was applied. Growth and survival of V. infausta was not affected by manure application, but fertilizer and irrigation increased root collar diameter, leaf, shoot and branch numbers. At 33 months after planting, U. kirkiana and S. birrea had not reached reproductive maturity, while V. infausta and M. indica had started fruiting in the second year. It is concluded that fertilization, manure and irrigation do not increase early growth or survival of U. kirkiana and S. birrea contrary to the commonly held assumption about factors that affect growth and survival in this species. The poor response to fertilizer and dry-season irrigation could be attributed to either their adaptation to infertile soils and unimodal rainfall regimes in their natural stands or delayed response that could not have been observed in the short period of the study.

Effect of Nursery practices on seedling survival and growth of selected Miombo tree species, Morogoro, Tanzania

Effect of Nursery practices on seedling survival and growth of selected Miombo tree species, Morogoro, Tanzania

Participatory Planting and Management of Indigenous Trees: Lessons from Chivi District, Zimbabwe

This paper reports on action research that evaluated local perceptions and knowledge of indigenous tree planting and management in the Romwe catchment, Chivi District, southern Zimbabwe. The species tested were the overexploited Afzelia quanzensis, important for timber and carvings of sculptures and utensils; Sclerocarya birrea, the marula tree used for wood, bark, and fruit; and Brachystegia glaucescens, the dominant miombo tree species, used for firewood, fiber, and fodder. Participants volunteered to plant and manage the test seeds, while a research team monitored their activities and results for 26 months. For Afzelia quanzensis, the germination rate was 81%, and 69% of the seedlings were still alive after one year. In the case of Sclerocarya birrea, the germination rate was 69%, and the one-year survival rate was 50%. For Brachystegia glaucescens, the germination rate was only 30%, and the survival rate was 31%. The main reasons for planting were to provide shade, to serve as a windbreak, and to conserve and gain individual control over dwindling natural resources, particularly Afzelia quanzensis. Women were generally more active and innovative than men. For instance, they searched for their own seeds or seedlings in the bush when there weren’t sufficient plants. Some participants tried out various indigenous methods of pest and disease control, water conservation, and moisture retention. Group feedback sessions and informal interactions provided the opportunity to share experiences. The participants learned that indigenous trees can be purposefully planted and were not simply a gift from God. Despite the droughts and political instability of recent years, a growing number of people became involved in tree planting during 2002–2003. As a result, there is now greater awareness among the local population of dwindling resources and their future potential.

Traditional Regulation of Edible Caterpillar Exploitation in the Kopa Area of Mpika District in Northern Zambia

The Traditional Ecological Knowledge (TEK) of the Bisa people of northern Zambia on species, life cycles and host plants of the caterpillars they exploit for food and for household income generation, and the traditional control of caterpillar harvesting, were investigated through a household survey. The accessed indigenous knowledge on caterpillar biology was validated through a forest survey, caterpillar collections and identifications. Eight species of caterpillars were harvested from the surrounding miombo woodlands. Their life systems and host plants were well understood by members of local communities and this knoweldge was communicated amongst them orally. Popular commercial species were Gynanisa maya Strand and Gonimbrasia zambesina Walker. Over 20 miombo tree species hosted the two species but the mean numbers of the caterpillars on Julbernadia paniculata Troupin were significantly larger than those on other host plants (p < 0.05), indicating that J. paniculata was probably the main host plant of the two species. Traditional regulation of caterpillar harvesting involved: (i) monitoring for edible caterpillar development and abundance and for changes in caterpillar habitats, (ii) protection of host plants and moth eggs against late bush fires, through use of traditional fire technology, and (iii) temporal restriction of edible caterpillar harvesting. The possibility of the Zambian Government promoting caterpillar harvesting as an economic incentive to the Bisa people to conserve both this renewable edible caterpillar natural resource and their environment is discussed.