Content uploaded by Bruce Morgan Campbell
Author content
All content in this area was uploaded by Bruce Morgan Campbell on Feb 22, 2022
Content may be subject to copyright.
A preview of the PDF is not available
The Miombo in transition: woodlands and welfare in Africa
... Southern African woodlands (SAW) are the dominant land cover in the dry tropics of southern Africa (Campbell, 1996) and form the world's largest savanna (Mistry, 2014;Ryan et al., 2016), covering much of Tanzania, Mozambique, Zambia, Zimbabwe, Malawi, Angola, and the southern Democratic Republic of Congo (DRC). The woodlands of this region are phylogenetically distinct from other tropical savannas (Dexter et al., 2015) and have biogeochemical and fire patterns (Alvarado et al., 2020) that are linked to unique functional traits (Osborne et al., 2018). ...
... For RQ1 we hypothesize that biogenic fluxes (GPP, R eco ) will be determined by a positive relationship with precipitation, the dominant control on biological metabolism in SAW (Campbell, 1996). We hypothesize that NBP across SAW will be determined by a negative relationship with burned area through E Fire . ...
Southern African woodlands (SAW) are the world's largest savanna, covering ∼ 3 M km², but their carbon balance and its interactions with climate and disturbance are poorly understood. Here we address three issues that hinder regional efforts to address international climate agreements: producing a state-of-the-art C budget of the SAW region; diagnosing C cycle functional variation and interactions with climate and fire across SAW; and evaluating SAW C cycle representation in land surface models (LSMs). Using 1506 independent 0.5° pixel model calibrations, each constrained with local Earth observation time series of woody carbon stocks (Cwood) and leaf area, we produce a regional SAW C analysis (2006–2017). The regional net biome production is neutral, i.e. -0.08 Mg C ha⁻¹ yr⁻¹ (95 % uncertainty interval -1.67/1.66), with fire emissions contributing ∼ 0.88 Mg C ha⁻¹ yr⁻¹ (95 % uncertainty interval 0.36–2.51). Fire-related mortality driving fluxes from the total Cwood to dead organic matter likely exceeds both fire-related emissions from Cwood into the atmosphere and non-fire Cwood mortality. The emergent spatial variation in biogenic fluxes and C pools is strongly correlated with mean annual precipitation and burned area. However, there are multiple, potentially confounding, causal pathways through which variation in environmental drivers impacts the spatial distribution of C stocks and fluxes, which is mediated by spatial variations in functional parameters like allocation, wood lifespan, and fire resilience. More Cwood in wetter areas is caused by positive precipitation effects on net primary production and on parameters for wood lifespan but is damped by a negative effect with rising precipitation increasing fire-related mortality. Compared to this analysis, LSMs showed marked differences in spatial distributions and magnitudes of C stocks and fire emissions. The current generation of LSMs represents savanna as a single plant functional type, missing important spatial functional variations identified here. Patterns of biomass and C cycling across the region are the outcome of climate controls on production and vegetation–fire interactions which determine residence times, which is linked to spatial variations in key ecosystem functional characteristics.
... Across the Miombo ecoregion, precipitation is a critical factor influencing ecosystem structure and function, resulting in highly heterogeneous vegetation patterns (Campbell, 1996;Godlee et al., 2021;Kuyah et al., 2016). Miombo woodlands sensu lato, found in regions with mean annual precipitation (MAP) between 600 and 1,400 mm, are characterised by an open tree canopy overstorey, a discontinuous understorey of shrubs and small trees, and a grass-dominated ground layer (Frost, 1996;Mayaux et al., 2004;Ryan et al., 2012). ...
... The woodlands of the DRC receive higher and more evenly distributed precipitation, resulting in higher water availability throughout the year. The vegetation is typical Miombo woodland, dominated by trees belonging to the legume genera of Brachystegia, Julbernardia, and Isoberlinia (Campbell, 1996). ...
The Miombo ecoregion covers eastern and southern Africa, with variations in plant species composition, structure, and biomass across a broad precipitation gradient. Most studies of woody plant communities focus exclusively on larger overstorey trees (�5or�10 cm stem diameter), overlooking the contribution of small trees and shrubs in the understorey, which can comprise a significant portion of total biomass and diversity. Here, we evaluate the contribution of both large overstorey and small understorey woody plants to species diversity and above-ground biomass (AGB), with 17 plots (0.5–1 ha) across five sites representing both extremes of rainfall gradient spanning the Miombo ecoregion, in northeast Namibia (500–700 mm mean annual precipitation, MAP) and southern Democratic Republic of Congo (DRC) (>1,200 mm MAP). Mean AGB per site ranged from 21 to 119 Mg⋅ha⁻1, increasing with rainfall, while the proportional AGB contribution of small trees, saplings, and shrubs decreased. In dry Namibia, small trees, saplings, and shrubs (<5 cm DBH) contributed up to 28.2% of total AGB (mean � standard deviation: 18.3% � 3.4%), whereas in wet DRC, they contributed only up to 2.5% (2.3% � 1.4%). Namibian sites, on average, contained a large proportion of woody species diversity exclusively in small trees and shrubs (<5 cm DBH), with 55 species representing 59.4% of the total diversity. In contrast, DRC sites had higher overall small woody plant diversity (66 species) but fewer species found exclusively as small individuals (25.2%), with many saplings that grow to larger trees. Understorey composition also differed, with saplings of overstorey trees dominating in DRC, while shrubs dominated in Namibia. Our findings show that woody biomass and diversity in dry woodlands are substantially underestimated when studies focus only on larger trees. This highlights the need to consider all woody vegetation to better understand woody plant diversity and biomass variation.
... The significant relationships observed between FWI system indices and BA vary by vegetation type, in a manner consistent with the variable constraints hypothesis proposed by Krawchuk and Moritz (2011) and the fire-productivity relationships described by Pausas and Ribeiro (2013). In the miombo woodlands and forest-savanna mosaic, where net primary productivity (NPP) ranges from 900 to 1600 g C/m 2 year (Campbell 1996), plant fuels are consistently available for burning during the dry season, making fuel moisture the key constraint on area burned. In contrast, in the drier Zambezian Baikiaea woodlands of southern Angola, where NPP ranges from 200 to 300 g C/m 2 year (Atlas of the Biosphere, based on Kucharik et al. 2000), fuel moisture during the dry season does not inhibit fire occurrence, which may instead be constrained by fuel availability, particularly in drier years. ...
Background
In African savannas, the most intense fires occur during the late dry season, when fuel availability is high and atmospheric relative humidity low. The Fire Weather Index (FWI) system has been used to measure the effort required for fire suppression and explore the impact of climate on fires.
Aims
This study assesses trends in FWI system indices from 1979 to 2022 and their influence on burned area (BA).
Methods
We employed the Theil–Sen slope estimator and contextual Mann–Kendall test to evaluate the presence of significant trends in FWI system indices during the early dry season (EDS) and late dry season (LDS), and assessed how trends in BA depend on fire weather.
Key results
We found distinct patterns in fire weather trends between the EDS and LDS, the LDS showing more widespread areas of increasing trends. However, only 28% of the regression analyses showed significant relationships with BA, suggesting a moderate influence of the FWI system on BA interannual variance.
Conclusions
Fire weather severity is increasing faster and more extensively during the LDS than the EDS. Additional factors play a significant role in shaping BA trends. Proactively managing anthropogenic fires during the moister EDS can help mitigate fire intensity, reduce emissions and support biodiversity conservation efforts.
... In contrast, PET exhibited weak and negative relationships with SOC (Figure 7a), suggesting its indirect influence on SOC dynamics mediated through MAP. Indeed, vegetation dynamics and, hence, SOC dynamics are mainly controlled by MAP and MAT in these ecosystems (Campbell, 1996;Chen et al., 2003;Chidumayo, 2005). In savannas, a linear relationship has been reported between biomass production and precipitation (Scholes et al., 2002), similar to other grassland regions of the world (Sala et al., 1988). ...
Savanna ecosystems in sub‐Saharan Africa harbor substantial yet relatively unexplored reserves of soil organic carbon (SOC). Our study unravels for the first time the interplay between climate, reference soil groups, and anthropogenic disturbances in shaping SOC dynamics in these ecosystems. We analyzed SOC along climosequences in natural woodlands in Mozambique and Zambia, with mean annual temperature (MAT) of 20–24°C, and mean annual precipitation (MAP) of 365–1,227 mm. Anthropogenic disturbances were assessed through comprehensive field surveys and remote sensing of vegetation and indices change. MAT and evapotranspiration (PET) had no discernible effect on SOC. Bulk SOC, particulate organic matter, and mineral‐associated organic matter stocks in the topsoil (0–10 cm) increased with MAP, though this relationship was not significant for the subsoil. MAP explained only 35% of topsoil SOC variability, limited by anthropogenic disturbances, which raised SOC stocks in the dry savanna but resulted in SOC losses at >600 mm MAP, which even extended into subsoil. For sites with little disturbance in the past decades, there were soil group‐specific effects of MAP on SOC, explaining up to 85% of data variability. In disturbed sites, human presence altered the carbon (C) balance to an extent that, as rough estimate, could account for up to 2.6 Gt CO2‐C loss over 20 years in wetter sites, with another 2.4 Gt CO2‐C at risk as populations spread into these otherwise pristine environments. Accurate modeling of climate‐change effects on the C cycle must therefore include the transformative impacts of current human activities, such as wood harvesting and grazing.
... These forests cover almost 4.1 billion hectares, or 31% of the planet's land surface [4]. In Africa, forests represent around 675 million hectares [5,6], of which almost 12% is covered by miombo [7,8], a forest dominated-by woody species of the genera Brachystegia, Julbernardia and Isoberlinia [9,10]. This forest covers between 2.7 and 3.6 million km² of the Zambezi ecoregion [11], providing a livelihood for over 100 million people in both rural and urban areas [12,13]. ...
The sustainability of reforestation initiatives depends on the involvement of local communities, whose lack of ownership compromises efforts to combat deforestation in the Lubumbashi Charcoal Production Basin. This study assesses reforestation activities in two village areas (Milando and Mwawa), based on individual interviews (50 individuals/village area) and floristic inventories carried out in two types of habitats (reforested and unexploited) for each village area. The hypotheses test whether (i) reforested habitats and tree species were inclusively selected and sustained through community-based practices, (ii) reforested habitats exhibit comparable ecological metrics to unexploited miombo due to protected regrowth, and (iii) ethnobotanical and floristic lists show variations reflecting differing anthropogenic impacts and limited species diversity in reforestation efforts. Thus, the interviews gathered data on habitat and woody species selection for reforestation, and management practices, while the inventories assessed the condition of these reforested habitats in terms of density per hectare, basal area, mean square diameter, and floristic diversity. The results show that in both village areas, the selection of habitats for reforestation was carried out concertedly (22.0044.00% of citations). Woody species were chosen according to the needs of local communities (40-52%) and the availability of seeds (18.00-44.00%). Furthermore, management practices for these reforested habitats include planning/assessment meetings (26.00-38.00%) and maintenance activities, such as firebreaks (38.00-46.00%) and surveillance of reforested habitats (24.00%). Additionally, these practices are being increasingly neglected, jeopardizing reforestation efforts. However, density/ha, basal area, mean square diameter and floristic diversity did not show significant differences between reforested and unexploited habitats, particularly at Milando (p>0.05). Furthermore, floristic similarity is 55.56% for reforested habitats and 93.75% for unexploited habitats but remains low between reforested and unexploited habitats (40.00-47.62%). This similarity between ethnobotanical and floristic lists is also low (43.75-31.58%). Finally, a total of 442 woody individuals were recorded in reforested habitats and 630 in unexploited ones, with Fabaceae dominating both habitat types. Despite some cited reforestation species like Acacia polyacantha being absent, Brachystegia spiciformis emerged as the most prevalent species in both reforested and unexploited areas. The results of the present study suggest a sustainable and continuous management of these reforested habitats for an effective reconstitution of the forest cover. To reinforce the sustainable management of these reforested habitats, it is recommended that decision-makers conduct with awareness-raising campaigns and establish payment for environmental services mechanisms to motivate communities.
... These forests cover almost 4.1 billion hectares, or 31% of the planet's land surface [4]. In Africa, forests represent around 675 million hectares [5,6], of which almost 12% is covered by miombo [7,8], a forest dominated-by woody species of the genera Brachystegia, Julbernardia and Isoberlinia [9,10]. This forest covers between 2.7 and 3.6 million km² of the Zambezi ecoregion [11], providing a livelihood for over 100 million people in both rural and urban areas [12,13]. ...
The sustainability of reforestation initiatives depends on the involvement of local communities, whose lack of ownership compromises efforts to combat deforestation in the Lubumbashi Charcoal Production Basin. This study assesses reforestation activities in two village areas (Milando and Mwawa), based on individual interviews (50 individuals/village area) and floristic inventories carried out in two types of habitats (reforested and unexploited) for each village area. The hypotheses test whether (i) reforested habitats and tree species were inclusively selected and sustained through community-based practices, (ii) reforested habitats exhibit comparable ecological metrics to unexploited miombo due to protected regrowth, and (iii) ethnobotanical and floristic lists show variations reflecting differing anthropogenic impacts and limited species diversity in reforestation efforts. Thus, the interviews gathered data on habitat and woody species selection for reforestation, and management practices, while the inventories assessed the condition of these reforested habitats in terms of density per hectare, basal area, mean square diameter, and floristic diversity. The results show that in both village areas, the selection of habitats for reforestation was carried out concertedly (22.0044.00% of citations). Woody species were chosen according to the needs of local communities (40-52%) and the availability of seeds (18.00-44.00%). Furthermore, management practices for these reforested habitats include planning/assessment meetings (26.00-38.00%) and maintenance activities, such as firebreaks (38.00-46.00%) and surveillance of reforested habitats (24.00%). Additionally, these practices are being increasingly neglected, jeopardizing reforestation efforts. However, density/ha, basal area, mean square diameter and floristic diversity did not show significant differences between reforested and unexploited habitats, particularly at Milando (p>0.05). Furthermore, floristic similarity is 55.56% for reforested habitats and 93.75% for unexploited habitats but remains low between reforested and unexploited habitats (40.00-47.62%). This similarity between ethnobotanical and floristic lists is also low (43.75-31.58%). The results of the present study suggest a sustainable and continuous management of these reforested habitats for an effective reconstitution of the forest cover. To reinforce the sustainable management of these reforested habitats, it is recommended that decisionmakers conduct with awareness-raising campaigns and establish payment for environmental services mechanisms to motivate communities.
Highlights
•Evaluated potential of seasonal SAR-optical remotely sensed data for AGB mapping.
•Extensive and high-quality National Forest Inventory data was used.
•SAR-Annual images gave greater accuracy than individual seasonal images.
•Optical-Dry season images gave greater accuracy than hot season and annual images.
•A multi-seasonal SAR-optical image combination is recommended for AGB estimation.
This study assessed the structure and composition of a Miombo woodland stand subjected to selective logging through a forest inventory, measuring all trees with DBH ≥ 10 cm across 34 plots (1 ha each) for diameter, height, stem quality, and health status. The stand had a mean stem density of 255 stems/ha, basal area of 15 m²/ha, above ground biomass of 110 Mg/ha, and total volume of 145 m³/ha. The Fabaceae family, particularly Brachystegia spiciformis, dominated the composition. Diversity indices revealed moderate diversity (Shannon = 2.3, Simpson = 0.8, Pielou = 0.6), with a few dominant species. The diameter distribution followed a reverse J-shaped pattern typical of Miombo woodlands. The study (LevasFlor. (2024). Plano De Maneio Da LevasFlor, LDA) highlighted common features of selectively logged woodlands, including a low occurrence of large-diameter individuals from high-value commercial species, prevalence of disturbance-tolerant species, and limited regeneration for some species. These findings underscore the need for management strategies that balance ecological and socio-economic factors, mitigate logging impacts, promote regeneration, and ensure long-term sustainability. Effective policies are crucial for maintaining the ecological integrity and economic value of Miombo woodlands while addressing climate resilience and biodiversity conservation.
The sustainability of reforestation initiatives depends on the involvement of local
communities, whose lack of ownership compromises efforts to combat deforestation in
the Lubumbashi Charcoal Production Basin. This study assesses reforestation activities
in two village areas (Milando and Mwawa), based on individual interviews (50 individuals/
village area) and floristic inventories carried out in two types of habitats (reforested and
unexploited) for each village area. The hypotheses tested were the following: (i) Reforested
habitats and tree species were selected collaboratively, ensuring an inclusive approach;
(ii) ecological parameters—density per hectare, quadratic mean diameter, basal area, and
floristic diversity—of reforested sites were comparable to those of unexploited miombo
due to protection allowing natural recovery; and (iii) ethnobotanical and floristic patterns
reflect varying levels of anthropogenic disturbance and the limited diversity of species
used in reforestation. Thus, the interviews gathered data on habitat and woody species
selection for reforestation and management practices, while the inventories assessed the
condition of these reforested habitats in terms of density per hectare, basal area, quadratic
mean diameter, and floristic diversity. The results show that in both village areas, the
selection of habitats for reforestation was carried out concertedly (22.00–44.00% of citations).
Woody species were chosen according to the needs of local communities (40–52%)
and the availability of seeds (18.00–44.00%). Furthermore, management practices for these
reforested habitats include planning/assessment meetings (26.00–38.00%) and maintenance
activities, such as firebreaks (38.00–46.00%) and surveillance of reforested habitats (24.00%).
Additionally, these practices are being increasingly neglected, jeopardizing reforestation
efforts. However, density/ha, basal area, quadratic mean diameter, and floristic diversity
did not show significant differences between reforested and unexploited habitats, particularly
at Milando (p > 0.05). Furthermore, floristic similarity is 55.56% for reforested habitats and 93.75% for unexploited habitats but remains low between reforested and unexploited
habitats (40.00–47.62%). This similarity between ethnobotanical and floristic lists is also
low (43.75–31.58%). Finally, a total of 442 woody individuals were recorded in reforested
habitats and 630 in unexploited ones, with Fabaceae dominating both habitat types. Despite
some cited reforestation species like Acacia polyacantha being absent, Brachystegia spiciformis
emerged as the most prevalent species in both reforested and unexploited areas. The results
of the present study suggest a sustainable and continuous management of these reforested
habitats for an effective reconstitution of the forest cover. To reinforce the sustainable
management of these reforested habitats, it is recommended that decision-makers conduct
awareness-raising campaigns and establish payment for environmental service mechanisms
to motivate communities.
Species-level phenology models are essential for predicting shifts in tree species under climate change. This study quantified phenological differences among dominant miombo tree species and modeled seasonal variability using climate variables. We used TIMESAT version 3.3 software and the Savitzky–Golay filter to derive phenology metrics from bi-monthly PlanetScope Normalized Difference Vegetation Index (NDVI) data from 2017 to 2024. A repeated measures Analysis of Variance (ANOVA) assessed differences in phenology metrics between species, while a regression analysis modeled the Start of Season (SOS) and End of Season (EOS). The results show significant seasonal and species-level variations in phenology. Brachystegia spiciformis differed from other species in EOS, Length of Season (LOS), base value, and peak value. Surface solar radiation and skin temperature one month before SOS were key predictors of SOS, with an adjusted R-squared of 0.90 and a Root Mean Square Error (RMSE) of 13.47 for Brachystegia spiciformis. SOS also strongly predicted EOS, with an adjusted R-squared of 1 and an RMSE of 3.01 for Brachystegia spiciformis, indicating a shift in the growth cycle of tree species due to seasonal variability. These models provide valuable insights into potential phenological shifts in miombo species due to climate change.
Prolonged seasonal drought affects most of the tropics, including vast areas presently or recently dominated by 'dry forests'. These forests have received scant attention, despite the fact that humans have used and changed them more than rain forests. This volume reviews the available information, often making contrasts with wetter forests. The world's dry forest heterogeneity of structure and function is shown regionally. In the neotropics, biogeographic patterns differ from those of wet forests, as does the spectrum of plant life-forms in terms of structure, physiology, phenology and reproduction. Biomass distribution, nutrient cycling, below-ground dynamics and nitrogen gas emission are also reviewed. Exploitation schemes are surveyed, and examples are given of non-timber product economies. It is hoped that this review will stimulate research leading to more conservative and productive management of dry forests.
Although beekeeping is often classified as a branch of agriculture, beekeeping is a forest industry in regions which are not intensively cultivated and in forest areas, whether the beekeepers use primitive hives or modern commercial beekeeping techniques.
Some of the most valuable yielders of nectar and pollen are the forest trees, and the various shrubs and herbs of the forest and uncultivated areas. Thus the forests are of great importance as sources of food for bees, and through the industry of the bees, for mankind.
Most of the modern beekeeping equipment is made of timber, and the modern beekeeper is dependent upon the forests for his supplies, through the agency of the sawmiller and the bee appliance manufacturer. The primitive hive beekeeper obtains all his materials direct from the forest, and it costs him nothing but the labour of collecting the materials and converting them into hives. In the miombo woodland the trees killed by the beekeepers when collecting bark for hive making are large Julbernardia and Brachystegia. In view of the fact that the sawmillers in most of the miombo take mainly Pterocarpus the beekeepers may, in fact, be practising a useful form of silviculture by removing competitive trees of low timber value. The older trees which he kills may in any case have a lower nectar yield than the smaller ones he leaves.
Beekeeping can be combined with forestry or agriculture without requiring valuable land for its use. The nectar and pollen are produced by the trees, shrubs and herbs in any case, and the bees are used to collect these products from the flowers and convert them into honey and beeswax. Further, by pollination, the bees ensure the maximum production of fruit and seed, and materially increase the production of agricultural crops as well as the production of seed for the regeneration of the forest and the reclamation of eroded land. Thus beekeeping can play a valuable part in the multiple use of land.
The forests can be the source of greatly increased production of honey and beeswax if modern migratory beekeeping is practised. It is important that the forester should be familiar with the problems and needs of the modern apiarist whenever he appears, and should know the factors which have to be considered in selecting apiary sites, namely what is reasonable in the stocking of apiaries with hives, the distance the apiaries should be apart to prevent overstocking and restrict the spread of disease, and the techniques of apiary registration and the licensing of beekeepers in forest reserves. Finally, it is important for the forester to realize, in his concern to protect the forest from fire, that he has a valuable ally in the beekeeper.
The semi-arid regions of Tanzania have been plagued by problems of soil erosion, at least since 1900. This paper outlines the various approaches to these problems in the dry areas of the country in the period 1900–1970.
The causes of erosion given by the colonial administration are presented together with an examination of the agents of conservation.
Some of the more important conservation schemes and techniques are reviewed and the reasons for their comparative success or failure are discussed.
The area of Africa where woodland is dominant covers 12.1 percent, or 3.8 × 106 km2, of the land area (Malaisse et al., 1972). The main part of this area corresponds closely to the Zambezian Domain (White, 1965). In the vicinity of Lubumbashi miombo woodland comprises over 90 percent of the country; Brachystegia spp. and Julbemardia paniculata (Benth.) Troupin are the most dominant trees.
