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Anthropogenic disturbances (cultivation, harvesting of poles and firewood and protection) play a pivotal role in the recovery and growth of Baikiaea-Guibourtia-Pterocarpus woodland species. The aim of this study is to determine the reliability of tree growth rings in age determination and average radial growth of re-growing woodland stands. The relationship between stem diameter, number of growth rings, and age of selected stands was also investigated. The research assisted in understanding the growth patterns of the key commercial timber species (Baikiaea plurijuga, Guibourtia coleosperma and Pterocarpus angolensis) of the seasonally dry Baikiaea-Guibourtia-Pterocarpus woodlands around Gwaai and Tsholotsho in north-western Zimbabwe. Tree rings were physically counted on basal stem cross-sections collected from 20 trees of different age, for each species in each disturbance regime. STATISTICA statistical package version 7.0 (StaSoft inc, 1984 - 2006) was used for data analysis. The Simple Regression Model was used to test for relationships. The relationship between age and growth rings, showed a strong correlation (p

Seasonally dry woodlands are the dominant land cover across southern Africa. They are biodiverse, structurally complex, and important for ecosystem service provision. Species composition and structure vary across the region producing a diverse array of woodland types. The woodlands of the Hu&iacute, la plateau in southwest Angola represent the extreme southwestern extent of the miombo ecoregion and are markedly drier than other woodlands within this ecoregion. They remain understudied, however, compared to woodlands further east in the miombo ecoregion. We aimed to elucidate further the tree diversity found within southwestern Angolan woodlands by conducting a plot-based study in Bicuar National Park, comparing tree species composition and woodland structure with similar plots in Tanzania, Mozambique, and the Democratic Republic of Congo. We found Bicuar National Park had comparatively low tree species diversity, but contained 27 tree species not found in other plots. Plots in Bicuar had low basal area, excepting plots dominated by Baikiaea plurijuga. In a comparison of plots in intact vegetation with areas previously disturbed by shifting-cultivation agriculture, we found species diversity was marginally higher in disturbed plots. Bicuar National Park remains an important woodland refuge in Angola, with an uncommon mosaic of woodland types within a small area. While we highlight wide variation in species composition and woodland structure across the miombo ecoregion, plot-based studies with more dense sampling across the ecoregion are clearly needed to more broadly understand regional variation in vegetation diversity, composition and structure.

Foraging by African savanna elephant (Loxodonta africana) and other herbivores tends to result in a piosphere effect around water sources, with increasing pressure on vegetation as distance to water decreases. This study aimed to investigate the impacts of pumped waterholes on woody vegetation in the southern portion of Zimbabwe’s Zambezi National Park, a Baikiaea woodland ecosystem characterised by high elephant densities. The recent rehabilitation and addition of pumped waterholes has resulted in a dense waterhole network in the park, prompting concerns around potential negative impacts on vegetation. Sampling plots were located at different distances from four pumped waterholes in Baikiaea plurijuga and Terminalia sericea woodlands. Elephant browsing levels and vegetation structure were assessed across three plant height classes (0.2

Some imported guitars and others made in Zambia exhibit poor sound quality and properties. Zambia grown timbers were evaluated for their suitability as tonewoods. Pinus kesiya was suitable for soun...

Pterocarpus angolensis DC. (Kiaat) is one of the most preferred timber species that occurs in most southern African countries, including Namibia. In Namibia, the species mainly occurs across the five regions in the north-eastern part of the country where commercial timber harvesting has taken place since the 1940s. Information about the growth rates of the species is currently lacking, yet this information is required to determine a sustainable harvesting regime in Namibia. Therefore, more data about diameter increment is needed. This study aims to (1) determine annual diameter increment of P. angolensis in order to assist in planning for sustainable harvesting levels in the northern regions of Namibia, (2) compare growth of P. angolensis with other woodland species (Burkea africana, Baikiaea plurijuga, Terminalia sericea and Schinziophyton rautanenii) and (3) compare P. angolensis growth rates found in northern Namibia with those found in other countries within its distribution range. A total of 111 increment cores and 73 stem discs were collected for tree-ring analysis. The results showed that the average diameter increment of P. angolensis was higher in the Kavango regions (0.71–0.80 cm yr−1) than in neighbouring regions (0.35–0.41 cm yr−1). The northern Namibian growth rate is estimated as 0.50 cm yr−1 and lies within the growth range reported for southern Africa. Growth rates of P. angolensis were more than 0.10 cm yr−1 lower than rates of T. sericea and S. rautanenii, but 0.10 cm yr−1 higher than B. africana and B. plurijuga. Age–diameter relationships of P. angolensis may be a good indicator of tree age if a sufficient number of samples are obtained. Our results revealed a rotation cycle of 95–100 years to reach the minimum harvesting diameter of 45 cm in the Kavango regions. This rotation cycle should be a good guideline for sustainable management of this species. This study suggests that simple ring counting on increment cores and stem discs with additional diameter data can provide valuable information on growth rates and rotation cycles. Additional data and work on older trees (>100 years) is required to complete the age–diameter framework.

ContextAn understanding of large herbivore habitat choices in heterogeneous African protected areas is important for the better management of these key ecosystems. AimsTo determine habitat use of African buffalo (Syncerus caffer) and plains zebra (Equus quagga) in a heterogeneous protected area. MethodsZambezi National Park (ZNP), Zimbabwe, was divided into five vegetation types using an unsupervised classification on a Landsat satellite image that was classified into five land cover classes, using the K-means classification algorithm. African buffalo and plains zebra densities were then determined in each vegetation type using road transect surveys monthly between January 2013 and December 2015. Normalised difference vegetation index (NDVI), grass biomass, grass height and grass quality (nitrogen, calcium, phosphorus and acid detergent fibre content) were determined in each vegetation type during the wet (November to April) and dry (August to October) seasons to establish their quality as habitats for African buffalo and plains zebra. Key resultsBoth African buffalo and plains zebra mostly foraged in mixed and grassland areas, and avoided Zambezi teak vegetation type. Zambezi teak vegetation type had high NDVI due to the dense tree cover. Both African buffalo and plains zebra preferred vegetation types with intermediate grass biomass (approximately 300gm−2) and grass height (approximately 16cm). Grass nutritive value (in terms of nitrogen, phosphorus and acid detergent fibre) declined from wet to dry season in all vegetation types. ConclusionsAfrican buffalo and plains zebra in the ZNP confined their habitat use mostly to two vegetation types (mixed and grassland), which together covered 25% of the protected area. ImplicationsTeak (Baikiaea plurijuga) vegetation, which accounted for about 60% of the ZNP, was avoided by both African buffalo and plains zebra, suggesting that a significant part of the protected area was not used by the two herbivores.

This study classified the vegetation of the Savuti-Mababe-Linyanti ecosystem (SMLE), northern Botswana and developed a detailed map that provides a reliable habitat template of the SMLE for future wildlife habitat use studies. The major vegetation units of the SMLE were determined from satellite imagery and field visits and then mapped using Landsat 8 and RapidEye imagery and maximum likelihood classifier. These units were sampled using 40 m x 20 m (800 m²) plots in which the coverage of all plant species was estimated. Non-metric multidimensional scaling (NMS) demonstrated that plant communities were determined by gradients in soil texture or fertility and wetness. NMS 1 represented a gradient of soil texture with seven woodland communities on sandy soils (sandveld communities and Baikiaea forest) dominated by Baikiaea plurijuga in Baikiaea forest and Terminalia sericea and Philenoptera nelsii in sandveld, with various indicator species differentiating the various sandveld community types. Mopane woodland further from and riparian woodland adjacent to permanent water was common on less sandy alluvial soils. Mineral-rich, heavy clay soils in the sump of a large paleolake system support open grassland and mixed Senegalia/Vachellia (Acacia) savanna, with the mineral-rich soils supporting grasses high in minerals such as phosphorus, calcium, sodium and potassium, and thus this region is a critical wet season range for migratory zebra. Taller, high-quality grasses in the mosaic of sandveld and mopane woodland communities provide critical grazing for taller grass grazers such as buffalo, roan and sable antelope, whereas wetland communities provide reliable green forage during the dry season for a variety of herbivores, including elephant. This study has demonstrated how large-scale environmental gradients determine functional habitat heterogeneity for wildlife.Conservation implications: Our study demonstrated that the functionality of protected areas is determined by large-scale environmental gradients. Thus conservation science must aim to ensure that protected areas cover the full range of key environmental gradients in a region (soil texture and wetness in our study). Our habitat map provides a data base for wildlife habitat use studies in the region.

Climate has been demonstrated to change at different scales for as far back as we have been able to reconstruct it. However, anthropogenic factors have accelerated and are predicted to cause significant changes in temperature and precipitation around the globe. As a consequence, vegetation is being affected. To understand the historical behaviour of individual tree species and have insight on the potential effects of climate change, tree-ring studies have been applied. In this study, we examined a genus new to dendrochronology, namely Baikiaea plurijuga (Spreng.) Harm that dominates the Zambezi teak forests in Zambia with the objective of determining whether B. plurijuga forms annual rings and if so, whether these rings are cross-datable. We further determined the relationship between ring- width of B. plurijuga and climatic variables with the aim of understanding the potential climate change effects on the growth of these species in Zambia. We collected tree-ring samples from three Zambezi Teak forest reserves: Zambezi, Ila, and Masese located in Kabompo, Namwala, and Sesheke study sites respectively. Our examination of wood anatomical structures reviewed that the wood of B. plurijuga is diffuse porous and forms annual rings which were confirmed with samples of known age. The analysis resulted in three strong tree-ring chronologies of B. plurijuga. These chronologies were correlated with climate data from local weather stations which correlated negatively with evaporation and temperature and positively with rainfall. Our regression analysis indicated that evaporation has the highest influence on tree growth at all the study sites compared to temperature and rainfall alone. Evaporation in November and March, for example, explained almost a third of the radii's variance at the Namwala and Sesheke sites. The likely future temperature increase and rainfall decrease that are projected by IPCC for Southern Africa are likely to adversely affect B. plurijuga in Zambia.

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.

Background: Tropical dry forests cover less than 13 % of the world’s tropical forests and their area and biodiversity are declining. In southern Africa, the major threat is increasing population pressure, while drought caused by climate change is a potential threat in the drier transition zones to shrub land. Monitoring climate change impacts in these transition zones is difficult as there is inadequate information on forest composition to allow disentanglement from other environmental drivers. Methods: This study combined historical and modern forest inventories covering an area of 21,000 km2 in a transition zone in Namibia and Angola to distinguish late succession tree communities, to understand their dependence on site factors, and to detect trends in the forest composition over the last 40 years. Results: The woodlands were dominated by six tree species that represented 84 % of the total basal area and can be referred to as Baikiaea - Pterocarpus woodlands. A boosted regression tree analysis revealed that late succession tree communities are primarily determined by climate and topography. The Schinziophyton rautanenii and Baikiaea plurijuga communities are common on slightly inclined dune or valley slopes and had the highest basal area (5.5 – 6.2 m2 ha−1). The Burkea africana - Guibourtia coleosperma and Pterocarpus angolensis – Dialium englerianum communities are typical for the sandy plateaux and have a higher proportion of smaller stems caused by a higher fire frequency. A decrease in overall basal area or a trend of increasing domination by the more drought and cold resilient B. africana community was not confirmed by the historical data, but there were significant decreases in basal area for Ochna pulchra and the valuable fruit tree D. englerianum. Conclusions: The slope communities are more sheltered from fire, frost and drought but are more susceptible to human expansion. The community with the important timber tree P. angolensis can best withstand high fire frequency but shows signs of a higher vulnerability to climate change. Conservation and climate adaptation strategies should include protection of the slope communities through refuges. Follow-up studies are needed on short term dynamics, especially near the edges of the transition zone towards shrub land. ispartof: Forest Ecosystems vol:3 issue:1 status: published

Wildfire is a major disturbance in Baikiaea plurijuga Harms woodland savannas. We tested the hypothesis that the timing and intensity of herbivory influence fuel loads. We used three stocking rates namely light (three cows and four goats ha)1), medium (six cows and eight goats ha)1) and heavy (eleven cows and sixteen goats ha)1) and three times of grazing namely early-, middle- and late-growing seasons. Season of grazing and stocking rate influenced herbaceous phytomass. Phytomass was generally the highest (53.5 g DM m)2) in paddocks grazed during the early growing season and the lowest (27.8 g DM m)2) in those grazed during the late growing season. Phytomass was also generally the highest (40.4 g DM m)2) in lightly stocked paddocks and the lowest (32.7 g DM m)2) in heavily stocked ones. Litter mass was the lowest (160.8 g DM m)2) in paddocks grazed during the early season whereas there were no differences in ungrazed paddocks and those grazed during either mid- or late growing seasons (205.4 g DM m)2). There was a negative relationship between litter mass and stocking rate. Baikiaea Benth. woodlands should be grazed during either the mid- or lategrowing season at stocking rates greater than 0.1 LU ha)1 to reduce grass fuel loads.

The pattern of coarse-root distribution was analysed in the woody plant community along a 200-m edaphic gradient on a Kalahari sand woodland catena in Zimbabwe. The root systems of 45 trees and shrubs were excavated, mapped, and digitized to analyse rooting depth and architecture. Patterns of change in the above-ground community were also identified along this transect. Rooting depth increased, and the centre of mass of the root profile shifted towards the maximum rooting depth as a function of distance up the catena. The data also suggest that interspecific variation in rooting depth may increase up the catena. The below-ground pattern was accompanied by above-ground changes: species richness and basal area also increased up the catena. It is hypothesized that increasing soil depth allows greater coexistence of alternative water-use strategies, resulting in the observed increase in species richness up the catena.

I documented photosynthetic rates and seasonal stem total nonstructural carbohydrates (TNC) in six leguminous tree species Burkea africana, Baikiaea plurijuga, Erythrophleum africanum, Guibourtia coleosperma, Julbernardia globiflora and Pterocarpus angolensis exhibiting a range of leaf phenological patterns. My goal was to (i) measure photosynthetic characteristics and levels of stored stem carbohydrates in species with varying patterns of leaf phenology and (ii) determine seasonal patterns of stem carbohydrate storage. Despite significant differences in the timing of bud break and leaf cover between the six species, there were no significant differences in maximum photosynthetic rate, quantum efficiency or light saturation point between species. Similarly, there was no significant difference in seasonal mean stem TNC levels despite significant differences in the timing of bud break and leaf cover both between species and within a single species. However, while the average amount of TNC does not seem to be related to leaf phenology, the patterns of carbohydrate use and storage do seem to be related to leaf phenology. Resume J’ai documente les taux photosynthetiques et les hydrates de carbone non structurels totaux (total nonstructural carbohydrates - TNC) des pousses saisonnieres chez six especes d’arbres de l’ordre des legumineuses : Burkea africana, Baikiaea plurijuga, Erythrophleum africanum, Guibourtia coleosperma, Julbernardia globiflora et Pterocarpus angolensis, qui presentent des patterns varies dans la phenologie des feuilles. Mon but etait de: 1) mesurer les caracteristiques photosynthetiques et le taux d’hydrates de carbone stockes dans les pousses de chaque espece selon le pattern de phenologie des feuilles et 2) determiner le schema saisonnier de stockage d’hydrates de carbone dans les pousses. Malgre des differences significatives entre les six especes dans le timing de l’eclatement des bourgeons et de la poussee des feuilles, il n’y avait pas de difference significative du taux maximal de photosynthese, du rendement quantique ou du point de saturation de lumiere entre les especes. De meme, il n’y avait pas de difference significative des taux saisonniers moyens de TNC dans les pousses, malgre la difference observee dans le timing de l’eclatement des bourgeons et de l’apparition des feuilles entre les especes et au sein d’une meme espece. Toutefois, si la quantite moyenne de TNC ne semble pas liee a la phenologie des feuilles, le schema de l’utilisation et du stockage des hydrates de carbone semble y etre lie.

Fire, elephants, and frost are important disturbance factors in many African savannas, but the relative magnitude of their effects on vegetation and their interactions have not been quantified. Understanding how disturbance shapes savanna structure and composition is critical for predicting changes in tree cover and for formulating management and conservation policy. A simulation model was used to investigate how the disturbance regime determines vegetation structure and composition in a mixed Kalahari sand woodland savanna in western Zimbabwe. The model consisted of submodels for tree growth, tree damage caused by disturbance, mortality, and recruitment that were parameterized from field data collected over a two-year period. The model predicts that, under the current disturbance regime, tree basal area in the study area will decline by two-thirds over the next two decades and become dominated by species unpalatable to elephants. Changes in the disturbance regime are predicted to greatly modify vegetation structure and community composition. Elephants are the primary drivers of woodland change in this community at present-day population densities, and their impacts are exacerbated by the effects of fire and frost. Frost, in particular, does not play an important role when acting independently but appears to be a key secondary factor in the presence of elephants and/or fire. Unlike fire and frost, which cannot suppress the woodland phase on their own in this ecosystem, elephants can independently drive the vegetation to the scrub phase. The results suggest that elephant and fire management may be critical for the persistence of certain woodland communities within dry-season elephant habitats in the eastern Kalahari, particularly those dominated by Brachystegia spiciformis and other palatable species.

This study reviewed the distribution of ten common savanna trees in Namibia. Tree distributions were investigated in relation to bioclimatic, topographic and edaphic variables at a national scale. The factors of importance at these broad geographic scales appeared to be rainfall, substrate and, likely, the incidence of frost. Baikiaea plurijuga, Burkea africana, Guibourtia coleosperma and Pterocarpus angolensis seem to reach their bioclimatic limits in Namibia. At the local level, plant traits become important and contribute to explaining distribution patterns. High water and/or nitrogen use efficiency (Acacia erioloba, Colophospermum mopane), dual water obtaining strategies (Faidherbia albida), fire tolerance (e.g. Acacia species, Burkea africana and Pterocarpus angolensis) and drought tolerance (Boscia albitrunca) are some key attributes providing additional explanations for current distributions. Amongst the selected trees and at broad geographic scales, below-ground adaptations are governed by rainfall regime in combination with coarse-textured soils, whereby shallow-rooted trees prevail in the Kalahari sandveld. Deep-rooted species are found largely on non-sandy soils. Physiological performance of many trees appears to be directly linked to rainfall regime and trees may hence show varying performance throughout their distribution range. Insight into plant functional attributes of trees in Namibia is required to develop appropriate management strategies in the light of climate change. Modelling climate change impacts should consider the relative contribution of bioclimatic versus local environmental factors that explain the current distribution patterns of the selected trees.

Fire is a key factor affecting the survivorship and dynamics of woody plants in savannas, but few empirical studies in savanna vegetation have investigated correlates of mortality following fire at the level of individual stems. A study of stem mortality as a function of size, neighbourhood effects, and prior damage (mainly caused by elephants) was undertaken in an area of Kalahari sand vegetation in western Zimbabwe. Stem and whole-plant mortality were quantified for the dominant stems of 557 trees in 4 plots following dry season unplanned fires in 2001. Two plots were located in areas that had been affected by frost earlier in the season, and 2 in areas that had not. Mortality was also recorded for 1762 trees in 20 unburned reference plots, also classified according to the presence of frost damage. Mortality estimators were constructed with a maximum likelihood regression method. Whole-plant mortality was low (on the order of 1–2%) compared with stem mortality, which in burned plots approximated 100% for the smallest size classes and declined as a function of stem diameter. Fire-driven mortality was lower in stems protected by the crowns of larger trees than in stems that were in the open. There was also evidence to suggest that the effects of fire are exacerbated by the prior action of frost and elephant herbivory.

One of the main constraints hindering the increase of animal production in semi-arid regions of Africa is the inadequate supply of nutrients during the dry season. Incorporation of alternative feed resources in ruminant diets during this period could be a viable approach to overcome these limitations. The objective of this study was to evaluate the nutritive value of muiumba (Baikiaea plurijuga) tree seeds as an alternative nutrient source for ruminants. Muiumba seeds were compared to other eight feedstuffs including two cereal grains (corn and oat), two wheat by-products (wheat bran and distilled wheat) and four protein meals (coconut meal, sunflower meal, soybean meal and rapeseed meal) as to its chemical composition, in vitro organic matter digestibility (IVOMD) and in vitro gas production. The moderate crude protein concentrations (145 g/kg DM) of muiumba seeds indicate that this feedstuff could not be used as a protein supplement, contrarily to the majority of multipurpose tree seeds. Although the starch content was scarce (15 g/kg DM), the low neutral detergent fibre (235 g/kg DM), low molecular weight sugar (76.1 g/kg DM) and non-starch polysaccharide (510.5 g/kg DM) contents indicate that this feedstuff has potential feeding value. This was confirmed by the IVOMD (0.770) and by the data provided by the in vitro gas production showing that muiumba seeds had high (P

SUMMARY Over-abundance of elephants could result in a decline of woodlands and tall canopied trees. Elephant carrying capacity of woodlands can be defined as the subsistence of a threshhold number of elephants in woodlands where the growth of tall trees is not impaired. The aim of this study was to assess elephant damage in three woodland types dominated by Acacia erioloba, Baikiaea plurijuga and Colophospermum mopane which were monitored in plots distributed throughout northern Botswana. Contemporary densities of woody plants of nine height classes were compared with the associated local elephant densities and fire occurrences. Woodland types differed with respect to structure, extent of elephant damage and the occurrence of fire. It seems that woodlands sustaining high elephant impact, such as C. mopane can carry more elephants because of a healthy age structure. Inherently low seedling recruitment rates and high occurrences of fire preclude the carrying capacity of A. erioloba and B. plurijuga for elep...

Sustained elephant browsing and intense burning could result in the loss of woodlands under conditions where elephant densities are high, such as in northern Botswana. Three woodland types dominated by Acacia erioloba, Baikiaea plurijuga and Colophospermum mopane were monitored in plots and contemporary recruitment rates of woody plants were compared with the associated local elephant densities and fire occurrences. Woodland types differed with respect to structure, extent of elephant damage and the occurrence of fire. Canonical correlations indicated that high extent of fire damage and high elephant densities did not covary within the woodland types investigated. Low tree densities in some woodland types were associated with high elephant densities and new elephant damage to plants increased with high elephant densities during the dry season. Plots with an apparent high fire frequency had lower tree densities and higher cover abundance of shrubs and seedlings.

The extent of African elephant ( Loxodonta africana ) induced damage on shrub and mature Baikiaea plurijuga trees was investigated around artificial and natural watering points in northern Hwange National Park, Zimbabwe. Damage was assessed in three zones of elephant occupancy during the dry season i.e. high elephant occupancy zone (≤ 1 km from water points), moderate elephant occupancy zone (> 1–2 km from water points) and low elephant occupancy zone (> 2 km from water points). A total of 48 plots along baseline transects were sampled among four artificial watering points and four natural watering points at increasing distance from the watering points. Damage to recruits, mature B. plurijuga and overall woody vegetation decreased with distance from artificial watering points. In addition, damage to mature B. plurijuga and overall woody vegetation decreased with distance from natural watering points, whereas damage to recruits did not change with distance from water points. Our results show that artificial watering points are associated with higher damage to B. plurijuga recruits and overall woody vegetation within ≤ 1 km radius from water points compared to natural watering points. Other changes associated with increasing distance from artificial watering points were increase in canopy cover and decrease in woody species diversity. In the natural watering points, we recorded an increase in canopy cover, mean basal area of B. plurijuga shrubs and height B. plurijuga shrubs, and a decrease in species diversity with distance from watering points. Overall, woody species diversity was higher around natural watering points than around artificial watering points. Our findings suggest that browsing by large herbivores near watering points leads to the degradation of vegetation.

Elephant damage to woody plant species in northern Botswana was distinguished from damage caused by fire, and other unknown factors. Elephant-induced damage to trees and shrubs that dominated the vegetation biomass in 33 sites suggested that elephants had a more or less random impact on the vegetation throughout their distribution range although the total biomass removal was low. Three principal patterns of vegetation utilization became apparent: (1) there was a hight variation in the proportion of woody plants damaged by elephants, particularly in the vicinity of permanent water sources; (2) the proportion of important food plants damaged by elephants increased significantly with the proximity of plants to temporary water sources; (3) there was a clear distinction between the effects of elephants and fire on different plants species. Ordination analyses suggested that the vegetation in northern Botswana could be classified into three zones containing (1) high fire impact and low elephant damage; (2) high elephant impact and low fire damage; and (3) minor damage by elephants and/or fire.

Schinziophton Muell. - Arg. has three tropical south, west African species (1) and S. rautanenii schinz (mungongo - Lozi) is confined to Africa South of the equator in the Democratic Republic of Congo, Angola, Namibia, Botswana, South Africa (Northern part), Mozambique, Zimbabwe and Zambia. In Zambia, it occurs almost in all provinces except the copper belt. It is a typical tree of the open Baikiaea plurijuga, Guibourtia coleosperma, Brachystergia spiciformis woodland on Kalahari sands in the southern and western provinces. It grows in woodlands near dambo heads on sandy alluvium in the eastern province. It appears occasionally in Acacia chipya, escarpment woodlands and secondary thickets.

The natural occurrence of the first profisetinidins associated with (−)-epicatechin is demonstrated in the heartwood of three legumes. 1 H NMR spectroscopy at 300 MHz permits assessment of the relative abundance of the predominant rotamers in each of the heptamethyl ether diacetates of the (−)-fisetinidol-(4α,8) and (4β,8)-(−)-epicatechins at ambient temperatures.

Fluctuations in densities of woody plant species were monitored in plots within three northern Botswana woodland types subjected to elephant damage and burning. Woodlands dominated by Baikiaea plurijuga and Colophospermum mopane sustained significant changes occurring on an annual basis, whereas Acacia erioloba plots maintained a typical structure. The structure of A. erioloba woodlands appeared to be influenced by factors other than elephants and the occurrence of fire. Woodlands dominated by C. mopane plants were subjected to obtrusive elephant damage, although the densities of tall trees remained largely unchanged. The effects of fire were most prominent in B. plurijuga woodlands. Tree densities declined consistently and plants of lower height classes, such as shrubs and seedlings increased in densities in areas subjected to a high occurrence of fire.

The woody vegetation on Kalahari sand deposits in Hwange (ex-Wankie) National Park, Zimbabwe was classified into nine types on the basis of species composition. Ordination of the data showed that the types which occupy the ends of the major (soil-type) gradient are easily distinguishable, viz. well developed, mature Baikiaea plurijuga woodlands on deep sands, and scrub Terminalia sericea and mixed woodland on soils with a higher clay content or compact layer. The central groups of stands, involving mixed woodlands and scrub, were less easy to interpret, and previous logging disturbance is involved. In the disturbed Baikiaea woodlands recruitment appears to be less than is required for long-term maintenance, even given that some of the measurements may have led to underestimates. Elephants were shown to have only a minor effect, and are relatively insignificant as agents of change in the woodlands. Depth of sand and soil moisture regime are the predominant factors determining overall vegetation structure. Fire is a dominant feature in scrub areas and interacts with frost, which has a periodic severe effect on developing saplings in scrub and in some disturbed woodlands. Although the relief is very flat there is a marked frost gradient from ‘ridge’ areas with mature woodland into the slightly lower-lying scrub areas. A conceptual model of the dynamics of the vegetation, based on the above features, is described.

The phenological patterns of 9 woody species that are common components of Kalahari Sand communities were observed over a period of 32 months. The observations were made on plants adjacent to the soil moisture study sites which have been described earlier (Childes & Walker 1987). A pre-rain flush was noted in the 2 shrub/small tree species Ochna pulchra and Terminalia sericea. Leaf fall in all species was related to a decrease in soil moisture and minimum temperature. The rooting habits and other adaptations of the species resulted in a sequential leaf fall in the communities. Open woodland and scrub species such as Pterocarpus angolensis showed a generally synchronised pre-rain flowering, while the closed woodland species e.g. Baikiaea plurijuga had protracted asynchronous flowering periods. Fruit ripening generally occurred in the dry season when conditions were ideal for fruit and seed dispersal.

An examination of the tannin from Rhodesian teak ( Baikiaea plurijuga ) heartwood suggests that it is principally an anhydropolyleucofisetinidin. The property of the timber of turning red when exposed to light is associated with this constituent. Hederagenin and pinitol were also isolated as heartwood constituents in addition to the already known baikiain.