Mopane Research Articles

Characteristics of roost cavities used by Lilian's Lovebird Agapornis lilianae in Liwonde National Park, Malawi

Lilian's Lovebird Agapornis lilianae is a non-excavating cavity user of mopane Colophospermum mopane woodlands. We investigated roost characteristics of Lilian's Lovebirds in Liwonde National Park, Malawi. We quantified tree and roost site variables for roost and non-roost trees. Sixty-six roosts were found. Roosts were in large tall mopane trees with a mean diameter at breast height (dbh) of 57.4 ± 1.64 cm, a mean height of 16.5 ± 0.42 m, and with a mean cavity entrance height of 10.0 ± 0.05 m. Non-roost areas had significantly smaller trees (mean dbh = 39.4 ± 1.72 cm). Human disturbance was low in both areas, but browsing of African elephant Loxodonta africana was evident by large areas of stunted mopane woodland recorded in non-roost areas. We recommend that the current Liwonde National Park vegetation map be updated to highlight areas of stunted mopane woodland unsuitable for Lilian's Lovebird roosts. The impact of elephant browsing on large mopane trees should be assessed to understand its impact on the availability of suitable cavities for lovebirds and other tree cavity reliant vertebrate species.

Evaluation of the antibacterial activity of some African medicinal plants

Aiming to find new antibacterial compounds from African medicinal plants, forty extracts of different polarity from eight plant species were screened against Gram positive and Gram negative bacteria. The selected plants, Cleistochlamys kirkii, Colophospermum mopane, Cladostemon kirkii, Chrysophyllum viridifolium, Gardenia ternifolia, Grewia hexamita, Xeroderris stuhlmannii and Albizia adianthifolia, are used in Mozambique traditional medicine to treat infectious diseases. The best results were obtained for both apolar and polar extracts of C. kirkii root bark (Annonaceae) with minimum inhibitory concentration (MIC) of 7.5 – 62 µg/mL against Gram positive strains. Bioassay-guided fractionation of the methanol extract of C. kirkii allowed the isolation of several known compounds with different scaffolds, namely three flavanones, two α,β-unsaturated lactones, one mono-tetrahydrofuran derivative, one triterpene and one alkaloid. Their structures were assigned based on spectroscopic methods namely 1D-NMR and 2D-NMR experiments.

Tragelaphus strepsiceros browse during the dry season in the mopani veld of Limpopo Province, South Africa

Colophospermum mopane, commonly known as mopane, provides essential browse to the greater kudu (Tragelaphus strepsiceros), especially during the dry season. This study uses analysis of rumen-contents to quantify the use of C. mopane and other plants browsed by the greater kudu in the dry season. The study was conducted at the Sandown Game Farm, Musina Local Municipality, Limpopo Province of South Africa. Rumen samples were collected from three male and two female greater kudu culled in June 2014 and statistically analysed using t-Test: Paired Two Sample for Means and Pearson Correlation Coefficient analysis. Findings show that C. mopane contributed the most (47%) to the diet of the greater kudu during the dry season. Other important browse plants were Dichrostachys cineria (30%), Commiphora edulis (12%), Grewia bicolor (6%) and Combretum apiculatum (5%), with the contribution of T. prunioides and G. flava to the diet being insignificant. The plant parts mostly browsed were leaves, which contributed 75% to the diet. The remaining 25% of the diet consisted of pods and seeds. Gender differences in diet selection were observed. The diet of the female greater kudu consisted mainly of C. mopane (71%) and D. cineria (22%). The diets of the male greater kudu contained less C. mopane (33%), similar proportions of D. cineria (31%) and other browse species. Implications for the management and conservation of the greater kudu in the mopani veld are discussed.

Labdane and Clerodane Diterpenoids from Colophospermum mopane.

Five labdane (1-5), an isolabdane (6), and five clerodane diterpenoids (7-11), were isolated from seeds, husks, and leaves of Colophospermum mopane. Compounds 1-3 and 6-9 are new, and their structures were elucidated by means of physical data analysis (1D and 2D NMR, HRESIMS). The absolute configurations of 1, 7, and 10 were determined by single-crystal X-ray diffraction with Cu Kα radiation. For compounds 2 and 6, the absolute configurations were established by the modified Mosher's method and corroborated by comparison of experimental and calculated electronic circular dichroism spectra of their 3-p-bromobenzoate derivatives. The crude extracts and compounds were evaluated for antimicrobial activity. The leaf extract was the most active against Staphylococcus aureus (125 μg/mL). Compound 11 showed the best inhibitory activity, with minimum inhibitory values of 15.6 μg/mL against Escherichia coli and Staphylococcus aureus and 31.3 μg/mL against Enterococcus faecalis.

Evidence for facultative deciduousness in Colophospermum mopane in semi‐arid African savannas

AbstractLeaf phenology dictates the time available for carbon assimilation, transpiration and nutrient uptake in plants. Understanding the environmental cues that control phenology is therefore vital for predicting climate‐related changes to plant and ecosystem function. In contrast to temperate systems, and to a lesser degree, tropical forest systems, the cues initiating leaf drop in tropical savannas are poorly studied. We investigated the cues for leaf fall in a tropical monodominant arid savanna species, Colophospermum mopane, using an irrigation experiment. We tracked soil moisture, solar radiation, air temperature, leaf water status, leaf health and leaf carbon balance through the dry season in both irrigated and control plants. Water was the primary cue driving leaf loss of C. mopane rather than temperature or light. Trees watered throughout the dry season retained their canopies. These leaves remained functional and continued photosynthesis throughout the dry season. Leaf carbon acquisition rates did not decline with leaf age but were affected by soil moisture availability and temperature. Leaf loss did not occur when leaf carbon gain was zero, or when a particular leaf carbon threshold was reached. Colophospermum mopane is facultatively deciduous as water availability determines leaf drop in this widespread arid savanna species. Obligate deciduosity is not the only successful strategy in climates with a long dry season.

English

This study aimed to determine the suitability of ethnomedicinal plants as a suitable option for palliative care of cancer in Namibia. To achieve this, key informant interviews were conducted in central and northern parts of Namibia on the use of ethnomedicinal plant products for palliation of cancer. Information from surveys on the medicinal use of plants in Oshikoto and Zambezi regions of Namibia for ailments such as tumors were used to select plants for phytochemical analysis. Plants were collected and extracts were prepared for analysis for phytochemical detection using thin layer chromatography, anti-protease, antioxidant and phytochemical quantification of Colophospermum mopane and Shinziophyton rautanenii plants. Findings from key informant interviews revealed pain management for cancer patients was the primary form of disease management at health care facilities in contrast to an established holistic palliative care system. As a result, patients looked towards alternative treatment from ethnomedicinal plant sources in their bid to palliate cancer and seek hope. Phytochemical analysis of indigenous plants collected, revealed the presence of class compounds such as flavonoids, alkaloids, triterpenes, coumarins and anthraquinones as well as biological activities such as anti-protease, antioxidant properties. In conclusion, phytochemical properties of the six plants were consistent with their ethnomedicinal use, making them a suitable option for treatment of cancer in resource poor settings such as Namibia. Further studies are required to evaluate safety and mode of action. Key words: Palliative care, Namibia, medicinal plants, anti-cancer.

Tree foliar chemistry in an African savanna and its relation to life history strategies and environmental filters.

Understanding the relative importance of environment and life history strategies in determining leaf chemical traits remains a key objective of plant ecology. We assessed 20 foliar chemical properties among 12 African savanna woody plant species and their relation to environmental variables (hillslope position, precipitation, geology) and two functional traits (thorn type and seed dispersal mechanism). We found that combinations of six leaf chemical traits (lignin, hemi-cellulose, zinc, boron, magnesium, and manganese) predicted the species with 91% accuracy. Hillslope position, precipitation, and geology accounted for only 12% of the total variance in these six chemical traits. However, thorn type and seed dispersal mechanism accounted for 46% of variance in these chemical traits. The physically defended species had the highest concentrations of hemi-cellulose and boron. Species without physical defense had the highest lignin content if dispersed by vertebrates, but threefold lower lignin content if dispersed by wind. One of the most abundant woody species in southern Africa, Colophospermum mopane, was found to have the highest foliar concentrations of zinc, phosphorus, and δ13C, suggesting that zinc chelation may be used by this species to bind metallic toxins and increase uptake of soil phosphorus. Across all studied species, taxonomy and physical traits accounted for the majority of variability in leaf chemistry.

Assessing the aftermath of the fast track land reform programme in Zimbabwe on land-use and land-cover changes

An understanding of the role of land policies as major drivers behind tree species diversity reduction in southern Africa is still rudimentary. This study, therefore, sought to assess the aftermath of the fast track land reform programme in Zimbabwe on land-use and land-cover changes. Specifically, we characterised the spatio-temporal changes in land-cover between 2000 and 2010 as a result of the land reform policies in Quagga Pan Ranch, Masvingo Province, Zimbabwe. Secondly, we assessed the effects of the fast track land reform programme of 2000 on tree species diversity. Finally, we attempted to establish whether there was selective logging in newly resettled areas and also sought to understand the reasons behind selective tree logging. Land-cover changes were characterised after classifying Landsat satellite images of 2000 and 2010. Tree species data were collected using quadrats in newly resettled and unsettled areas for determining the state of selective logging. Questionnaires and observations were used to understand the patterns of diversity loss. Results show significant changes in land-use and land-cover between 2000 and 2010 with an increase in agricultural areas and a decrease in woodlands, specifically in newly resettled areas. Significant differences (α < 0.05) were noted between tree species diversity in areas that have been resettled and in areas that have not been resettled. Tree species diversity is relatively very high in areas that have not been resettled and very low in areas that have been resettled. Colophospermum mopane is the most used tree species because it's a cheap source of fuel and it's durable in domestic uses. It can be concluded that agricultural expansion is necessary for sustaining livelihoods as long as proper conservation methods of the tree species and the environment are maintained.

Microbial community structure and functional diversity of nitrogen-fixing bacteria associated with Colophospermum mopane

Colophospermum mopane is an indigenous legume tree that grows in Southern Africa and is one of the predominant trees of the woodland vegetation. In order to increase knowledge about its ecology, especially how C. mopane thrives in the nitrogen-poor soils of the region, we analyzed the root-associated bacteria to assess the active diazotrophic diversity and total microbial diversity by culture-dependent and independent techniques. Root nodules were not detected but in some samples the lateral roots showed an outgrowth-like protuberance, that were not likely to have functions related to legume root nodules. The bacterial isolates recovered were related to Actinobacteria, Firmicutes and Proteobacteria. The total microbial diversity was dominated by Actinobacteria-related phylotypes, while the active diazotrophic diversity showed that the majority of the sequences were related to the order Rhizobiales but also to Spirochaetes, Firmicutes, Bacteroidetes and Deltaproteobacteria. Several isolates showed characteristics of plant growth-promoting bacteria. These findings increase the spectrum of possible phylotypes that can be found in legume trees that are typically nodulated by Alpha- and Betaproteobacteria, and reveal for the first time a surprising diversity of nitrogen-fixing bacteria active in legume tree roots.

Assessment of plant biodiversity on and off mature stands of Androstachys johnsonii Prain and Colophospermum mopane (J.Kirk ex Benth.) J. Leonard

The species that were growing on the stands of C. mopane and on open space stands weighed more than those on the stands of A. johnsonii in both loam and sandy soil areas. This is probably an indication that there are some toxic chemicals that are excreted from various parts of A. johnsonii that caused the suffering and hence lesser weights of the understory species of A. johnsonii. The conditions were found to be unfavorable for the majority of the understory species to grow and flourish well under the canopies of A. johnsonii. This therefore, might imply that even though A. johnsonii possess allelochemical materials, some understory species may adapt to such conditions in the proximity of its vicinity. The decomposition of different parts of the plant on the ground surface under A. johnsonii canopies probably results in relatively highest concentration of allelochemical materials in the soil on A. johnsonii stands. Limiting factors like shading, temperature, water availability, and soil type may not necessarily be causes of the observed differences as the investigation was carried out from the same areas. The present investigation revealed that A. johnsonii in woodlands chokes its understory plants and such plants might eventually die out. Key words: Allelochemical materials, Androstachys johnsonii, Colophospermum mopane, biodiversity, impact.

English

Cancer is a major health problem, not only in developed countries, but also in developing countries where the number of cancer-related ailments is growing. Chemotherapy is the most commonly used treatment option but side effects associated with its use necessitates the search for alternatives. Over 80% of the population in developing countries relies on ethnomedicinal plants for primary healthcare including cancer. There are concerns about the safety and efficacy of such ethnomedicines but unfortunately, the prerequisite laboratory set up for such evaluation is usually lacking. An inexpensive, sensitive, field oriented assay would greatly facilitate and improve research into alternative anticancer plant based medicinal therapies. This study proposes to evaluate the suitability of Dugesia dorotocephala as an alternative laboratory method for antiproliferative properties of indigenous plant extracts. Brown planaria, D. dorotocephala maintained under laboratory settings were divided into three groups, each containing a minimum of three planaria. Each planaria was dissected into two using a sterile scalpel. The tail section was transferred into a 24 well plate, after measuring its length in mm. Root and bark extracts of Colophospermum mopane and Schinziophyton rautanenii were prepared at concentrations (5 and 20 µg/ml) and incubated with dissected planaria for 8 days, fresh extracts were replaced every two days and the planaria was observed for its length in addition to the development of eye spots. Planaria regeneration was observed in control wells receiving no treatment, however, a growth promoting effect was exhibited by S. rautanenii root extract in a time and concentration dependant manner at 5 µg/ml. An anti-proliferative effect was observed for S. rautanenii bark extracts and this was observed at both concentrations, with the higher extract of 20 µg/ml exhibiting more growth antiproliferative activity. The extract of C. mopane root had a cytotoxic effect at concentration 20 µg/ml, causing planaria death. The use of Planaria represents an inexpensive, quantifiable, field oriented method to evaluate the effect of indigenous plant extracts in the absence of cell culture. This method is capable of distinguishing between different treatments, extract concentrations as well as time points. Key words: Dugesia dorotocephala, plant extracts, anti-proliferative, alternative method.

An Assessment of Impacts of African Elephants (Loxodonta africana) on the Structure of Mopane (Colophospermum mopane) in the North Eastern Lake Kariba Shore, Zimbabwe

A study on impacts of African elephants (Loxodonta africana) on the structure of C. mopane was done on the north eastern Lake Kariba shore, Zimbabwe. The objectives of the study were to determine the structure and abundance of C. mopane, determine the levels of elephant induced damage on C. mopane along a distance gradient from the lake and to determine the relationship between elephant induced damage on C. mopane trees and distance from the north eastern Lake Kariba shore. C. mopane trees were sampled in May 2013. Four belt transects were demarcated extending from the lake towards the ZESA pylons. Eight plots measuring 20 m x 30 m were systematically placed at 100 m, 500 m, 1000 m and 2000 m distances from the lake shore within each belt. C. mopane variables, that is, tree height, basal area, tree density, shrub density, number of stems per plant, density of damaged plants and number of dead trees were recorded within each plot. Damage was also assessed and rated depending on the intensity of damage. A total of 479 C. mopane trees were sampled in 32 plots. Data was analysed using STATISTICA Version 7 Results from Kruskal-Wallis ANOVA test (KWH test), indicated that Height (P=0.5423), basal area (P=0.9463), tree density (P=0.2465), shrub density (P=0.3027), number of stems per plant (0.7503, density of damaged plants (P=0.1802) and density of dead trees (P=0.4603) were not significantly different across all distances from the lake. The results also indicated no significant difference in the level of damage (P=0.8050) across all distances from the lake. PCA indicated that trees were densely populated in areas close to the lakeshore (100 m and 500 m) and it is within this area where the highest number of damaged and dead trees was recorded. HCA showed that plots within 2000 m recorded the highest average sapling density, plots within 1000 m recorded the highest average tree height and shrub density and plots within 100 m recorded the highest of density of damaged trees and basal area. Findings from linear regression showed that distance from water create an herbivory gradient of C. mopane utilization though the herbivory gradient might not lead to overall degradation of C. mopane. Management should focus on maintaining herbivore populations within ranges that does not lead to C. mopane woodland degradation.

Stand Structure, Diversity and Regeneration Status of Woody Species in Open and Exclosed Dry Woodland Sites around &amp;lt;i&amp;gt;Molapo&amp;lt;/i&amp;gt; Farming Areas of the Okavango Delta, Northeastern Botswana

Stand structure, diversity and regeneration status of woody species were investigated in open and exclosed dry woodland sites in Island Safari, Shorobe and Xobe, northeastern Botswana. A total of 105, 111 and 130 quadrats, measuring 20 × 20 m each, were laid down along parallel line transects in the three sites, respectively, to collect data. A total of 47 species, representing 16 families and 24 genera, were recorded in the study sites. Of these, 33 species representing 13 families and 20 genera, 41 species representing 15 families and 23 genera and 27 species representing 10 families and 14 genera were encountered in Island Safari, Shorobe and Xobe, respectively. The most diverse family was Fabaceae followed by Combretaceae and Tiliaceae at all the three sites. The most diverse genus was Acacia, followed by Combretum and Grewia. The diversity of woody species in the study sites were 2.18, 2.15 and 1.5 in Shorobe, Island Safari and Xobe, respectively, while their corresponding evenness values were 0.6, 0.6 and 0.5, respectively. The mean densities of the woody species encountered in Island Safari, Shorobe and Xobe were 2629, 4271 and 2745 individuals ha&#451, respectively. The five densest species were Colophospermum mopane, Dichrostachys cinerea, Acacia tortilis, Philenoptera violacea and Terminalia prunioides in Island Safari, C. mopane, A. tortilis, A. erioloba, P. violacea and D. cinerea in Shorobe and Acacia mellifera, A. tortilis, P. nelsii, A. luederitzii and A. erubescens in Xobe. The highest important value index values were exhibited by C. mopane, D. cinerea, A. tortilis, P. violacea and T. prunioides in Island Safari, C. mopane, A. erioloba, A. tortilis, P. violacea and C. imberbe in Shorobe, and A. mellifera, A. tortilis, P. nelsii and A. luederitzii in Xobe. The alarming result was the fact that 71%, 80% and 85% of the woody species recorded in Island Safari, Shorobe and Xobe, respectively, exhibited hampered regeneration and, thus, unhealthy population structures. Therefore, there is an urgent need to address the observed unhealthy population structures of the woody species through investigation of the major causes of their hampered regeneration, and also designing measures that will facilitate natural and artificial regeneration of these species at the three study sites.

A comparative assessment of baobab density in northern Mana Pools National Park, Zimbabwe

Ecological effects of elephant (Loxodonta africana) have emerged a contentious issue considering their impact on woodlands in protected areas in sub-Saharan Africa (Kassa et al., 2013; Staub, Binford & Stevens, 2013). Hence, there is a need to establish how these impacts are distributed over space and time. Such spatial and temporal ecological studies could guide policy and decisions related to elephant and vegetation management in protected areas. Previous studies highlighted that the spatial distribution of baobabs in African savannah is site specific and influenced by a complex of establishment factors, such as herbivory (Mashapa et al., 2014), droughts (De Smedt et al., 2012), human activities (O’Connor & Campbell, 1986), climate change (Sanchez, Osborne & Haq, 2011) and/or soil type (Mashapa et al., 2013). Interestingly, a significant mortality of baobabs in northern Mana Pools National Park, Zimbabwe (hereafter, northern Mana Pools), was attributed to elephant damage between 1984 and 1988 (Swanepoel & Swanepoel, 1986; Swanepoel, 1993). Swanepoel (1993) recorded an annual baobab mortality rate of 7.3% and postulated that by the early 2000s, the baobab population would have halved in northern Mana Pools. Therefore, the aim of this study was to compare baobab density and the annual rate of baobab mortality in northern Mana Pools between 1984 and 2005, in relation to the baseline study by Swanepoel & Swanepoel (1986). Materials and methods Mana Pools National Park (2196 km) is located in midZambezi valley region, north of Zimbabwe, between latitudes 15°400 and 16°200S and longitudes 29°080 and 29°450 (ZPWMA, 2011). It was designated a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site in 1984 (ZPWMA, 2011). Colophospermum mopane woodland is the most extensive vegetation type in northern Mana Pools, and the climate is classified as semi-arid (ZPWMA, 2011). Data were collected following the baseline study method of Swanepoel & Swanepoel (1986) on the same belt transects to facilitate direct comparison with the previous baobab survey of 1984. In the 1984 survey, 124 baobabs were marked (Swanepoel & Swanepoel, 1986) and these were searched to reevaluate their status in April 2005. Variables that were recorded included: baobab density, basal circumference, level of elephant induced damage on baobabs and baobab plant status (dead/alive). Comparisons of baobab density (per km) between 1984 and 2005 in northern Mana Pools were carried out using Mann–Whitney U-tests in STATISTICA version 7 for Windows (StatSoft, 2004). Annual baobab mortality rate was calculated from a direct measurement in accordance to Krebs (1994); thus, direct measurement was achieved by observing how many previously marked baobab individuals had survived through time, from 1984 to 2005 in northern Mana Pools. Baobabs that were not found were assumed dead.

Factors influencing the adaptation and distribution of &lt;i&gt;Colophospermum mopane&lt;/i&gt; in southern Africa’s mopane savannas – A review

Colophospermum mopane is the dominant tree or shrub within mopane woodland in the subtropical areas of southern Africa’s savanna ecosystems. This article provided a review on the adaptation capabilities of mopane against fire, browsing activity and environmental stresses. It further reviewed and tested the extent to which rainfall, temperature, altitude and soil types had an effect on the distribution of mopane in southern Africa. Mopane is adapted to survive moisture stresses, low nutrient environments and even disturbances caused by fire and browsing by large herbivores through its physical, physiological and chemical responses. Adaptation of mopane to various stresses enables it to dominate the low-lying areas of southern Africa’s savannas. The distribution of mopane is best associated with low to moderate rainfall (R2 = 0.38), high temperature (R2 = 0.42), low altitudes (R2 = 0.44) and a variety of soil types. An increase in the annual rainfall ( 800 mm) and altitude ( 800 m.a.s.l.), coupled with a reduction in the minimum temperature and acidic soil, limits the distribution of mopane. Mopane in South Africa occurs under similar environmental conditions to those in Zimbabwe and Zambia, but quite different from those in Angola, Namibia, Mozambique, Malawi and Botswana where mopane occurs.

Simplification of the composition, diversity and structure of woody vegetation in a semi-arid African savanna reserve following the re-introduction of elephants

Elephant populations at high density commonly transform their habitat, but a low density population would not be expected to have a marked impact. Re-introduction of elephants into the Venetia-Limpopo Nature Reserve (320km2) in the early 1990s established a low density population for the period of survey (0.16–0.33 individuals km−2). Accordingly, their impact on the composition and structure of the woody vegetation of three riparian and nine dryland vegetation types was measured between 1997 and 2010 using 148 permanent transects. Riparian habitat showed a greater change in composition and diversity, and also a greater decline of species richness, density of tall trees or total basal area, than dryland habitat. Change of dryland Commiphora Woodland was comparable to changes of riparian types. These conspicuous changes were a consequence primarily of severe use by elephants. Some species within these vegetation types declined markedly in abundance. Vegetation types dominated by Colophospermum mopane showed an increase in total basal area and relatively minor change in composition or structure, resulting mainly from the impact of moisture stress. Vegetation types that were severely impacted by elephants constituted <10% of reserve area; lightly impacted dryland C. mopane types constituted >70% of area. Some uncommon, selected dryland species were heavily impacted by elephants. A number of species may therefore be trending toward local extirpation. It was concluded that the coexistence of elephants and some plant species in this medium-sized, contained reserve was not possible.

Distribution of Lilian's Lovebirds in Malawi

Lilian's Lovebird Agapornis lilianae is regarded as a mopane Colophospermum mopane woodland specialist. Its global population is sparse and is spread along the Zambezi valley with little known about its current distribution and status. We explored the current distribution of Lilian's Lovebird in Malawi, and in particular focused on the distribution and habitat associations of the largest resident population in Liwonde National Park (LNP). Local birders and tourist guides provided distribution information from across Malawi. Transect walks were conducted to collect data in LNP. Five new atlas records are reported; three were within 40–56 km of the LNP population and two were over 150 km south and north of LNP, respectively. One of the sites is about 66 km from the Lilian's Lovebird population in Luangwa Valley, Zambia. New national records were evidence of the importance of seasonal movements to the species. Lilian's Lovebirds occurred throughout LNP with the highest abundance in the central section. Seasonal movements to areas outside the park were also recorded. A variety of vegetation types were used by the lovebirds, but the strongest habitat associations were with seasonally wet grasslands and not mopane woodlands as would be expected. Thus, conservation efforts should also include these other habitats.

Increasing temperatures can improve seedling establishment in arid-adapted savanna trees.

Plant species are shifting their ranges in response to global climate change, thus intensifying the need to predict such changes accurately. As the environmental requirements controlling plant distribution act differently at each developmental stage, there is a need to acquire a demographic-specific understanding of the factors which determine these distributions. Here we investigated the germination niche of two common savanna species Acacia nigrescens and Colophospermum mopane, with the aims to disentangle the direct and indirect effects of temperature on seed germination and establishment and to explore the impact of higher temperatures on the establishment success of savanna trees. Under laboratory conditions, we used thermal gradient plates to determine the thermal germination niche of both species, and a water stress experiment was conducted on C. mopane to account for water-temperature interactions. Using these data we parameterised a soil-moisture model to determine germination and establishment success under field conditions at current and future temperatures (+4°C). Based on this model, higher future temperatures will not limit germination directly, but they will reduce the number of germination events by reducing the time window of suitable available soil water. Conversely, warmer conditions will accelerate the rate of radicle extension and increase the frequency of seedling establishment events. An additional advantage of higher temperatures is that fewer seeds will germinate, resulting in slower seed bank depletion when successful seedling establishment events do occur.

In the Shade of the Mopane:Ledebouriain Namibia

1. The Mopane (Colophospermum mopane) dominates vast areas of sub-saharan Africa, as here in the Kaokoveld. The shade it provides is used by animals and plants, including Ledebouria. Photo by T. Harvey. Namibia is a country with great diversity in both flora and fauna, and it is a land of friendly and welcoming people; a place where one can go to get away from the busyness of urban living and get back to nature. It is for these reasons that many people around the globe flock to Namibia every year, with some making it their permanent home and it is here that researchers continue to find new and exciting plant species, such as Aloe, Euphorbia and Commiphora. With an area of 318,695 sq miles (825,418 sq km) and a population of 2.3 million—compare that to Los Angeles, CA, USA with a population of 3.8 million and 503 sq miles (1,302 sq km)— it is no wonder that many wonderful plant species await discovery, especially ones of a small stature like Ledebouria.

Response of Colophospermum mopane to different intensities of tree thinning in the Mopane Bushveld of southern Africa

In the Mopane Bushveld, Colophospermum mopane is viewed as a threat due to its ability to suppress the herbaceous layer. The objective of this study was to investigate the re-establishment of C. mopane over a 19-year period on seven plots thinned to different tree densities. Thinning was completed during 1989 and measurements done annually from 1990 to 1995 and again during 2008. Absolute tree densities (plants ha−1) increased in the low tree density plots, whereas in the high tree density plots the tree densities declined. Changes in leaf phytomass of the C. mopane trees were more pronounced than changes in absolute tree densities and growth of the remaining trees mainly occurred as increases in canopy diameter, rather than increases in tree height. Growth of established trees displayed an exponential increase in growth with declining tree density demonstrating the suppressive effect of inter-tree competition on the growth of individual trees. A trend towards an equilibrium appears to exist where some self thinning occurred in the dense plots, opposed to increases in the number and size of trees in the thinned plots. Considering the benefits of trees (soil enrichment and food to browsing herbivores), tree thinning rather than tree clearing is recommended.