Acacia Karroo Research Articles

Functional and species composition of understory plants varies with mistletoe-infection on Vachellia karroo trees in a semi-arid African savanna

In savanna ecosystems, tree canopy patches differ in plant species composition compared to adjacent intercanopy spaces due to different levels of resource availabilities. Mistletoes further augment nutrients underneath tree canopies whilst reducing their hosts’ competitive edge, thus providing more resources and creating patches that support higher understory species richness. However, little is known on how understory species and functional trait assemblages, in both canopy and intercanopy spaces, are affected by varying overstory mistletoe infection intensities. This study investigated how functional and species diversity/composition varied within and between canopy patches and intercanopy spaces of high- and low mistletoe-infected Vachellia karroo trees. The affinity of individual species to the different canopy patches and intercanopy spaces was also assessed. Microhabitats had significantly different species compositions. A higher proportion of species (34%) showed a strong positive affinity towards canopy patches whilst intercanopy spaces were strongly associated with only 9% of recorded species, indicating greater dominance of some species there. Generally, subcanopy patches had significantly higher species richness and diversity, and functional diversity, compared to adjacent intercanopy spaces. These variables increased with increasing mistletoe infection, thus grass, forb and tree species diversity were 17–43% higher, and functional diversity indices were 0.5–28% greater in high- compared to low mistletoe-infection canopy patches. Furthermore, species richness and diversity of C 3 , C 4 , annual and perennial plants were 1.27–3.13-fold higher within canopy patches compared to intercanopy spaces and 1.28–1.74-fold greater within high- compared to low mistletoe-infection microhabitats. Consequently, high mistletoe-infection canopy patches had between 1.08 and 3.76-fold greater species richness and diversity of C 3 , C 4 , annual and perennial plants compared to the other three microhabitats. Our findings suggest that by enhancing spatial heterogeneity, variations in mistletoe infection facilitate biodiversity and to a lesser extent vegetation structural diversity in these semi-arid savannas. • Mistletoes provide additional resources to understory plants. • Species and functional diversity are greater within subcanopies than intercanopies. • Increased mistletoe infection, proliferates species and functional diversity. • Many species have a strong affinity to high mistletoe-infection subcanopies. • Mistletoes increase plant diversity in semi-arid savannas.

Seasonal dynamics on nutritive value, chemical estimates and in vitro dry matter degradability of some woody species found in rangelands of South Africa

Unlocking browse species in semi-arid regions can be a key to improving the livestock productivity. The research was conducted to assess the browse species variation in chemical composition and in vitro dry matter degradability as influenced by seasonal (summer and winter) changes. Leaves from ten randomly selected browsable trees from sixteen species (Vachellia karroo, Senegalia nigrescens, Vachellia nilotica, Balanites maughamii, Berchemia discolor, Berchemia zeyheri, Bridelia mollis, Combretum collinum, Combretum imberbe, Dalbergia melanoxylon, Dichrostachys cinerea, Grewia monticola, Grewia occidentalis, Melia azedarach, Ormocarpum kirkii and Ziziphus mucronata) were harvested before defoliation from the site in two seasons (summer and winter) and dried at room temperature and then ground for analysis. Two-way analysis was used to analyse chemical composition and in vitro ruminal dry matter degradability. Melia azedarach (343.7 g/kg DM) had the highest (p < 0.0001) CP content in summer. In winter, B. maughamii (210.3 g/kg DM) had the highest (p < 0.05) crude protein content. Combretum collinum (2.90 Mcal/kg) had a highest (p < 0.0001) metabolizable energy value in summer. Bridelia mollis, B. maughamii, B. discolor, C. collinum, C. imberbe, O. kirkii, S. nigrescens, V. nilotica, G. occidentalis and B. zeyheri had the same (p > 0.0001) dry matter degradability (DMD) 48 values across two seasons. In both seasons, most of these browse species have the potential to supplement low quality natural grasses because they go beyond the minimum requirement of protein and have coherent amounts of fibre concentration. There is a need to assess the bioactive compounds found in these browse species for the amelioration and also to maximize browsing of these species.

Short duration overnight cattle kraaling in natural rangelands leads to increased tree damage by elephants

AbstractElephants are attracted to nutrient hotspots created through short duration overnight cattle corralling (hereafter kraaling) in natural rangelands at Debshan, a mixed cattle-wildlife private ranch in central Zimbabwe, causing severe tree damage. We determined the effect of age of nutrient hotspot (i.e., time after kraal use) on elephant use and the extent of tree damage. Elephant use and tree damage were assessed in nutrient hotspots of varying ages (6, 12, 24, 36 and 48 months after kraal use) and in surrounding landscape. We also compared Acacia karroo bark nutrient and soil nutrient concentration between nutrient hotspots (24 months after kraal use) and the surrounding landscape. Elephant use of nutrient hotspots was highest at 12 and 24 months after kraaling. The most severely damaged trees were in the 12-, 24- and 36-month-old nutrient hotspots. Acacia karroo bark nutrient concentrations (nitrogen, potassium, calcium, magnesium and iron) were higher in nutrient hotspots than surrounding vegetation, while soil nutrients (nitrogen, phosphorus, calcium and potassium) were higher in nutrient hotspots than surrounding landscape. We concluded that elephants mostly used nutrient hotspots 12 and 24 months after kraaling, while severe tree damage occurred 12, 24 and 36 months after kraal use.

A Review of Ethnoveterinary Knowledge, Biological Activities and Secondary Metabolites of Medicinal Woody Plants Used for Managing Animal Health in South Africa.

Globally, the use of ethnoveterinary medicine as remedies for animal health among different ethnic groups justify the need for a systematic exploration to enhance their potential. In addition, the increasing popularity and utilisation of woody plants remain common in traditional medicine, which may be attributed to their inherent benefits. The current review was aimed at analysing ethnoveterinary surveys, biological activities, and secondary metabolites/phytochemical profiles of the woody plants of South Africa. Eligible literature (period: 2000 to 2020) were retrieved from different databases such as Google Scholar, PubMed, Sabinet, and Science Direct. Based on the inclusion and exclusion criteria, 20 ethnoveterinary surveys were eligible and were subjected to further analysis. We identified 104 woody plant species from 44 plant families that are used in the treatment of different diseases in animals, particularly cattle (70%) and goats (20%). The most mentioned (with six citations) woody plants were Terminalia sericea Burch. ex DC and Ziziphus mucronata Willd., which were followed by plants with five (Cussonia spicata Thunb., Pterocarpus angolensis DC and Vachellia karroo (Hayne) Banfi & Galasso) or four (Acokanthera oppositifolia (Lam.) Codd, Cassia abbreviata Oliv., and Strychnos henningsii Gilg) individual mentions. The most dominant families were Fabaceae (19%), Apocynaceae (5.8%), Rubiaceae (5.8%), Anacardiaceae (4.8%), Combretaceae (4.8%), Euphorbiaceae (4.8%), Malvaceae (4.8%), Rhamnaceae (4.8%), and Celastraceae (3.8%). Bark (33%), leaves (29%), and roots (19%) were the plant parts dominantly used to prepare remedies for ethnoveterinary medicine. An estimated 20% of woody plants have been screened for antimicrobial, anthelmintic, antioxidant, and cytotoxicity effects. Phytochemical profiles established a rich pool of valuable secondary metabolites (phenolic, flavonoids and condensed tannins) that may be responsible for the exerted biological activities. Overall, the significant portion of woody plants lacking empirical evidence on their biological effects indicates a major knowledge gap that requires more research efforts.

Does a reciprocal transplant experiment of neighboring Vachellia karroo populations demonstrate local adaptation?

Vachellia karroo (Hayne) Banfi & Galasso (formerly Acacia karroo) is the most widespread tree in southern Africa, and exhibits wide morphological variation such that the phenotypes have been considered as separate species. We sought to determine whether local adaptation was occurring in two neighboring Vachellia karroo populations (ca. 15 km apart) in South Africa that show tremendous size variation as adults. We examined seedling and sapling performance of genotypes grown in reciprocal environments that differ in climatic and edaphic conditions. We used a field reciprocal transplant experiment at Richards Bay and Empangeni, and complemented this with a common garden study. We measured total height, stem diameter, thorn length, leaf area, leaf weight, plant aboveground dry weight and specific leaf area after 4 months and 16 months for common garden and field-grown plants, respectively. For greenhouse-grown plants, root dry weight was also measured. Phenotypes of seedlings and saplings from the two populations maintained their differences in the greenhouse and in the field. Greenhouse-grown plants showed lower proportional root allocation for Richards Bay than Empangeni (i.e. root mass fraction: 0.20 ± 0.01 vs 0.60 ± 0.02). In the field, there were significant genotype-by-environment interactions for two of the seven performance traits for reciprocally-transplanted populations. We found limited evidence for local adaptation that is attributed to variation in edaphic conditions. Local adaptation was evident in two leaf traits (leaf area and leaf dry weight) that showed a genotype-by-environment interaction. These two traits clearly have important fitness consequences for photosynthesis. However, plants from one population grew taller and had longer thorns at both sites. We conclude that the magnitude of divergent selection in the two populations is relatively low and may be accompanied by processes such as genetic drift, leading to limited local adaptation and genetic differentiation.

Characterization and evaluation of mountain sweet thorn (Flacourtia montana J. Grah) collections

Mountain sweet thorn (Flacourtia montana J. Grah) is an indigenous underutilized fruit of the Western Ghats and other regions of peninsular India. It is a close relative of Governor’s plum. It is a bushy shrub or small tree with spiny trunks and branches which may grow up to 2.5 m in height. The fruits are bright dark red 1-2 cm in diameter, sweet edible, and have the potential for processing into jams and jellies. The presence of thorn is one of the major hurdles for the commercialization of this crop. Thus, seeds of the thorny plants of the Mountain sweet thorn were collected from different locations, and seedlings were planted to identify the suitable line. The plant height ranged from 425 cm (accession 0208) to 710 cm (accession​ ​0202). The plant girth ranged from 34.5 cm to 82 cm. The growth data revealed that all​ ​the accessions are vigorous, fast-growing, and have various levels of thorniness. All the​ ​accessions were found to be spreading type. Significant variability was recorded for leaf​ ​characteristics among the accessions studied. Three major clusters were observed in​ ​cluster analysis for morphological and fruiting characters consisting of 1, 8, and 9 accessions,​ ​respectively. The number of fruits ranged from 0 to 4008. The highest yield (9.46 kg/plant)​ ​was obtained in accession - 0106 followed by accession- 0201 (7.83 kg). The average​ ​fruit weight ranged from 1.51 g to 3.94 g. The highest fruit weight (3.94g) was also recorded​ ​in 0106 followed by 2.84 (0102). The total soluble solids ranged from 10 0 Brix to 15.1 0​ ​Brix. Overall, accession 0201 was found better than others with respect to yield, regular​ ​bearing, and less thorniness.

Characterization and evaluation of mountain sweet thorn (Flacourtia montana J. Grah) collections

Mountain sweet thorn (Flacourtia montana J. Grah) is an indigenous underutilized fruit of the Western Ghats and other regions of peninsular India. It is a close relative of Governor’s plum. It is a bushy shrub or small tree with spiny trunks and branches which may grow up to 2.5 m in height. The fruits are bright dark red 1-2 cm in diameter, sweet edible, and have the potential for processing into jams and jellies. The presence of thorn is one of the major hurdles for the commercialization of this crop. Thus, seeds of the thorny plants of the Mountain sweet thorn were collected from different locations, and seedlings were planted to identify the suitable line. The plant height ranged from 425 cm (accession 0208) to 710 cm (accession​ ​0202). The plant girth ranged from 34.5 cm to 82 cm. The growth data revealed that all​ ​the accessions are vigorous, fast-growing, and have various levels of thorniness. All the​ ​accessions were found to be spreading type. Significant variability was recorded for leaf​ ​characteristics among the accessions studied. Three major clusters were observed in​ ​cluster analysis for morphological and fruiting characters consisting of 1, 8, and 9 accessions,​ ​respectively. The number of fruits ranged from 0 to 4008. The highest yield (9.46 kg/plant)​ ​was obtained in accession - 0106 followed by accession- 0201 (7.83 kg). The average​ ​fruit weight ranged from 1.51 g to 3.94 g. The highest fruit weight (3.94g) was also recorded​ ​in 0106 followed by 2.84 (0102). The total soluble solids ranged from 10 0 Brix to 15.1 0​ ​Brix. Overall, accession 0201 was found better than others with respect to yield, regular​ ​bearing, and less thorniness.

Effect of encroaching woody plant species on soil nutrients and selected soil chemical properties in communally managed semiarid savanna grazing lands in the North West province, South Africa

Woody plant encroachment is recognised as one of the major threats to biodiversity in ecosystems. In many arid and semiarid areas of South Africa, indigenous encroacher species are proliferating, but the factors that favor their abundance are poorly understood. This study investigated the effect of encroaching woody species on soil properties. The effects of two encroaching species, Senegalia mellifera and Dichrostachys cinerea, on soil nutrients and chemical properties were investigated in 8 communally managed grazing sites and compared to the effects of the non-encroacher, Vachellia karroo, in two non-encroached benchmark sites. Three belt transects were laid out to determine woody plant density. Three soil samples (0-20 cm deep) per belt were sampled to determine soil properties. Senegalia mellifera was the most abundant with a mean density of 5907 TE ha−1. Soil properties in the benchmark sites had no significant differences (p > 0.05) than soil under encroaching D. cinerea regarding organic C, total N, C:N, exchangeable Na, CEC, EC, ESP, SAR and soil texture. Plant influence on soil differed among encroaching species and between encroaching and non-encroaching species. Plant diversity explain the variation of soil properties and prove the important specific role of each species in the ecosystem.

Effect of leaf type on browse selection by free-ranging goats in a southern African savanna.

Broad- and fine-leaved woody species respond to seasonal changes from wet to dry season differently. For example, broad-leaved species shed their leaves earlier, while fine-leaved species, especially acacias retain green foliage well into the dry season. These differences are expected to result in variation in selection of broad- and fine-leaved woody species as browse by free-ranging goats. We tested the hypothesis that free-ranging goats select broad-leaved woody species more than fine-leaved species during wet (growth) season and fine-leaved woody species more than broad-leaved species during dry season. In addition, we tested if broad- and fine-leaved woody species had different foliar dry matter digestibility and chemical composition (crude protein, neutral detergent fibre, acid detergent fibre, total phenolics and condensed tannins concentration). Free-ranging goats were observed foraging on broad- and fine-leaved woody species over a two-year period (2014 and 2015) during three seasons: early wet (October/November), late wet (February/March) and dry (May/June). Ivlev’s selectivity or Jacob’s index (Ei) was calculated for five woody species (two broad-leaved and three fine-leaved) browsed by goats during wet and dry season. Jacob’s selectivity index was higher for broad–leaved (Ziziphus mucronata and Searsia (Rhus) tenuinervis) than fine-leaved woody species (Acacia nilotica, Acacia karroo and Dichrostachys cinerea) during wet season. However, the trend was reversed during dry season with fine-leaved species having higher Jacob’s selectivity index than broad-leaved species. Leaf dry matter digestibility and chemical composition was similar between broad- and fine-leaved woody species throughout the year. We conclude that goats selected broad-leaved woody species during wet season when browse was plentiful and then switched to fine-leaved species which retained leaves during dry season.

Characterisation of Chamaecytisus tagasaste, Moringa oleifera and Vachellia karroo Vermicomposts and Their Potential to Improve Soil Fertility

Poor soil fertility and land degradation limit crop production among smallholder farmers. The practice of agroforestry with leguminous trees has proven to be sustainable as it bolsters nutrient supply through nitrogen fixation and nutrient cycling. The beneficiation of agroforestry species could add even more value by using tree based waste materials as mulch or vermicomposting. A study was conducted to investigate the impact of vermicomposting on chemical and biological characteristics of three agroforestry species; Chamaecytisus tagasaste, Vachellia karroo and Moringa oleifera. Eisenia fetida earthworms were added to the leaves and small twigs of the three trees in worm composting bins. The worms were allowed to feed on the feedstocks for six weeks under laboratory conditions. The results showed that vermicomposting significantly enhanced macronutrient nutrient content in all the three feedstocks. The findings also showed that the quality of the vermicompost depends on the feedstock type. M. oleifera had the best quality vermicomposts with a significantly higher composition of macronutrients which ranged between 50 and 170% higher for Ca, K, Mg and P. Vermicomposting increased Mo while other micronutrients such as Zn, Mn, Fe and B significantly decreased with vermicomposting time. In addition, vermicomposting increased E. fetida reproduction with more than a 450% increase in earthworm numbers in all three feedstocks. In conclusion, vermicompost have potential to be used to improve soil fertility and thus reduce the use of synthetic fertilisers in crop production.

Mistletoe litter accelerates the decomposition of recalcitrant host litter in a semi‐arid savanna, south‐west Zimbabwe

AbstractLitter mixing plays an important role in enhancing carbon and nutrient cycling, but little is known about the effects of nutrient‐rich mistletoe litter on the decomposition of slow‐decaying litter in nutrient‐poor environments. We investigated the effects of mistletoe litter on the decomposition and nutrient release of host Vachellia karroo litter in semi‐arid savanna, south‐west Zimbabwe. Mass loss and nutrient release was quantified in litter of each single species, two‐species, three‐species and four‐species mixtures of mistletoe, Erianthemum ngamicum, Plicosepalus kalachariensis and Viscum verrucosum, and the host V. karroo in 30 × 30 cm nylon‐mesh litterbags under field conditions at 2‐month intervals for one year. Repeated‐measures analysis of variance was used to test the effects of litter type, incubation time and their interaction on mass loss and nutrient release. The effects of initial litter quality, incubation time and litter mixture on decomposition rate were also tested. Litter mixtures of mistletoes and V. karroo decomposed three times faster than V. karroo decomposing alone, and decomposition of litter mixtures was influenced by initial litter quality and incubation time. Further, non‐additive effects are reported, with synergistic interactions being greater after 12 months and common regarding mass loss, phosphorus and carbon, whereas antagonistic interactions were common in nitrogen release. These effects varied both in magnitude and direction between litter‐mixing treatments and with incubation time (P &lt; 0.05). Our findings show that mistletoe litter enhance the decomposition of recalcitrant host litter consistent with findings in other ecosystems that contain hemiparasites, suggesting that hemiparasite litter plays an important role in carbon and nutrient flux in this system. Further, by enhancing the decomposition and nutrient release rate of recalcitrant host litter, mistletoes increase nutrient availability to other organisms within the ecosystem lending support to the premise that parasitic plants function as keystone species in environments where they occur.

Expanding the European distribution limits of &lt;em&gt;Bruchidius raddianae&lt;/em&gt;. First record in Portugal from Vachellia karroo’s infested seeds (Coleoptera: Bruchidae; Fabales: Fabaceae)

Several Australian and African Acacia shrubs and trees have been intentionally introduced into the Mediterranean basin for different purposes, but some species become invasive, such as Vachellia karroo (Hayne) Banfi and Galasso (syn. Acacia karroo) (Fabales: Fabaceae). The seed beetles, belonging to family Bruchidae, have a significant ecological and economic importance, either because they can be plant pests or, on the other hand, be used as biocontrol agents against invasive plant species. Bruchidius raddianae (Anton and Delobel, 2003) (Coleoptera: Bruchidae) is native to tropical and subtropical areas, but it has been recently reported from Cádiz and Málaga (southern Spain, 2007) and in the Lampedusa Island (Italy, 2015) from seeds of pods collected from V. karroo. This paper reports 104 specimens reared from seeds collected from V. karroo in Faro (southern Portugal) from August to October 2019, expanding the B. raddianae’ European distribution limits. This is also the first report of its presence in Portugal and the third in Europe.

Effect of different nitrogen fertilizer application rates on Dichrostachys cinerea and Acacia karroo sapling growth, foliar nutrient and antinutrient concentrations in a southern African savanna

AbstractNitrogen (N) fertilization influences woody plant growth, foliar nutrient and antinutrient concentrations. We conducted a nursery experiment to determine the effect of five N fertilization rates on Dichrostachys cinerea and Acacia karroo sapling height, basal diameter, growth of longest shoots and root length, crude protein (CP), acid and neutral detergent fiber (NDF), condensed tannins (CT) and total phenolic (TP) concentrations. Eight potted plants of each woody species were allocated to each of five N fertilization rates (0, 0.21, 0.42, 0.63 and 0.84 g N/kg of soil) in a completely randomized design. Different N fertilization rates did not result in varying plant growth in terms of height, stem diameter and root length in both D. cinerea and A. karroo. However, N fertilization rate of 0.63 g N per kg of soil resulted in an increase in length of the longest shoot in both D. cinerea and A. karroo. Foliar CP increased with an increase in N fertilization rate up to 0.63 g N per kg of soil, while acid and NDF, CT and TP were lowest at N fertilization rates of 0.63 g N per kg of soil in both D. cinerea and A. karroo. We conclude that N did not limit plant growth, and therefore N fertilization is unlikely to significantly improve sapling growth. However, N fertilization improved foliar CP and reduced CT and TP concentrations in both D. cinerea and A. karroo improving their nutritive value to browsers.

Evaluation of the Antimicrobial Properties of Vachellia karroo Hayne Banfi and Galasso Pods Used Traditionally for the Treatment of Venereal Diseases

Evaluation of the Antimicrobial Properties of Vachellia karroo Hayne Banfi and Galasso Pods Used Traditionally for the Treatment of Venereal Diseases

The Most Important Herbs Used in the Treatment of Sexually Transmitted Infections in Traditional Medicine

Sexually transmitted diseases (STDs) or venereal diseases are transmitted through various methods of sexual intercourse (oral, vaginal, and anal). The predisposition to this type of diseases and infections depends on the immunity system of the body, so the lower the immunity system’s strength, the greater the risk of Sexually transmitted infections (STIs). The most important pathogenic causes of STIs include bacteria, viruses, and parasites. Phytochemical investigations have shown that medicinal plants are a rich source of antioxidant compounds, biologically active compounds, phenols, etc. They can have an inhibitory effect on germs and infectious viruses and are very important for a variety of parasitic diseases, microbial infections, and STIs. Some of the most important medicinal plants that produce inhibitory effects on the growth and proliferation of pathogenic agents of the STIs were reported in the present article. Based on the results obtained from the review of numerous articles indexed in the databases the Institute for Scientific Information, Scopus, PubMed, Google Scholar, etc., a number of plants have been reported to be used in the treatment and prevention of genital tract diseases and STIs, and to produce antiviral and antimicrobial effects, including Taxillus, Aristolochia, Syzygium cumini, Albizia adianthifolia, Bidens pilosa, Carica papaya, Ranunculus, Peltophorum africanum, Vachellia karroo, Rhoicissus tridentate, Houttuynia cordata, Panax notoginseng, Nelumbo nucifera, Astragalus, Hypericum aethiopicum, Spondias mombin, Jatropha zeyheri, Ximenia caffra, Trichilia dregeana, Clematis brachiate, Tabernaemontana, Sarcophyton. Phytochemical investigations have examined the therapeutic and clinical effects of medicinal plants, and the use of their active ingredients to produce herbal drugs has been addressed. The results of phytochemical investigations have shown that the most important compounds of these plants include quercetin, isoquercitrin, Dammarane-type saponin, flavonoids, alkaloids, flavonoids, glycosides, terpenoids, steroids, astragalosides, flavonoids and polysaccharides, α-pinene, β-pinene, α-pinene, quercetin, myricetin and luteolin flavonoids, β-pinene, 1,3,8-p-menthatriene, ledene, m-menthane, linalyl acetate and 3-carene. β-sitosterol, lupeol, lupeol, sitosterol, spathulenol, β-sitostenone,

Transpiration dynamics and water sources for selected indigenous trees under varying soil water content

The major route through which water from the earth’s surface re-enters the hydrologic cycle in forested ecosystems is via tree transpiration (T). It is therefore important to have detailed understanding of the quantity and source of water transpired by different tree species. The aims of this study were to i) assess the trends of T for selected tree species (camel thorn, sweet thorn, shepherd’s tree and buffalo thorn) across a range of soil water content conditions and ii) partition the total T of the selected tree species growing in arid environments dominated by open cast mining activities into soil water and groundwater. Tree T was measured using the compensation heat pulse velocity (CHPV) method, while soil water content was monitored using DFM capacitance probes. The soil water content within the upper 50 cm soil profile ranged from 11 mm during the dry season to 20 mm during the wet season. The deeper soil layer (50–120 cm) was generally wetter compared to the top layer with water content was up to >30 mm during the wet season. The measured tree T ranged from 0.2 mm day−1 on buffalo thorn during the dry season to 1.9 mm day−1 on sheperd’s tree in summer. It was also revealed that T of large (diameter at breast height =46 cm) camel thorn trees is not responsive to seasonal variations of soil water availability and remained constant at approximately 1.2 mm day−1. Diurnal patterns of T did not effect changes on the soil water depletions within the top 120 cm soil profile, which indicated that the trees sourced water beyond this zone. Signs of daytime redistribution were observed within the canopy areas of the investigated trees during very limited soil water conditions of the dry season. It was concluded that the water use of trees is inclined to the seasonal variations, which however is not the case in old trees. Close to 100% of the water transpired by trees in the study area is sourced below 1.2 m (vadose zone and water table). We recommended investigation of daytime redistribution among the indigenous tree species of the study area. We also recommended extension of tree water use studies to other species for comprehensive catchment tree water use calculations to inform water budgets.

Exploration of Plant Species Used by Bapedi Ethnic Group for Ethnoveterinary Purposes: A Case Study of Ga-Mphahlele Region in the Limpopo Province, South Africa

The use of plant resources by the Bapedi people in the Limpopo province in South Africa is regarded as part of their tradition and culture. This study was aimed at documenting ethnoveterinary uses of plants in Ga-Mphahlele region in the Limpopo province, South Africa. Information was gathered through semi-structured questionnaires supplemented by field observations from 30 randomly selected Pedi speaking people in Ga-Mphahlele region of the Limpopo province. A total of 52 plant species from 32 plant families were used for 18 ethnoveterinary purposes. The majority of the species (21.2%) were used as fodder, followed by ethnoveterinary medicinal applications against wounds (19.2%), diarrhoea (17.3%), ticks (13.5%) and worms (11.5%) in domestic animals such as cattle, chickens, dogs, donkeys, doves, goats and sheep. The species with frequency of citation (RFC) higher than 0.70 included Citrullus lanatus (fodder), Vachellia karroo (ethnoveterinary medicine and fodder), Sclerocarya birrea subsp. caffra (fodder), Aloe ferox (ethnoveterinary medicine), Drimia sanguinea (ethnoveterinary medicine), Sarcostemma viminale subsp. viminale (ethnoveterinary medicine) and Sorghum bicolor (fodder). The traditional knowledge about forage and ethnoveterinary medicines demonstrated by the Bapedi people enable extension officers and policy makers to appreciate how local communities perceive and utilize plant resources around them.

Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa.

Vachellia karroo (formerly Acacia karroo) is a wide-spread legume species indigenous to southern Africa. Little is known regarding the identity or diversity of rhizobia that associate with this plant in its native range in South Africa. The aims of this study were therefore: (i) to gather a collection of rhizobia associated with V. karroo from a wide range of geographic locations and biomes; (ii) to identify the isolates and infer their evolutionary relationships with known rhizobia; (iii) to confirm their nodulation abilities by using them in inoculation assays to induce nodules under glasshouse conditions. To achieve these aims, soil samples were collected from 28 locations in seven biomes throughout South Africa, which were then used to grow V. karroo seedlings under nitrogen-free conditions. The resulting 88 bacterial isolates were identified to genus-level using 16S rRNA sequence analysis and to putative species-level using recA-based phylogenetic analyses. Our results showed that the rhizobial isolates represented members of several genera of Alphaproteobacteria (Bradyrhizobium, Ensifer, Mesorhizobium, and Rhizobium), as well as Paraburkholderia from the Betaproteobacteria. Our study therefore greatly increases the known number of Paraburkholderia isolates which can associate with this southern African mimosoid host. We also show for the first time that members of this genus can associate with legumes, not only in the Fynbos biome, but also in the Albany Thicket and Succulent Karoo biomes. Twenty-six putative species were delineated among the 88 isolates, many of which appeared to be new to Science with other likely being conspecific or closely related to E. alkalisoli, M. abyssinicae, M. shonense, and P. tropica. We encountered only a single isolate of Bradyrhizobium, which is in contrast to the dominant association of this genus with Australian Acacia. V. karroo also associates with diverse genera in the Grassland biome where it is quite invasive and involved in bush encroachment. Our findings therefore suggest that V. karroo is a promiscuous host capable of forming effective nodules with both alpha- and beta-rhizobia, which could be a driving force behind the ecological success of this tree species.

Response of photosynthesis, growth and water relations of a savannah-adapted tree and grass grown across high to low CO2.

By the year 2100, atmospheric CO2 concentration ([CO2]a) could reach 800 ppm, having risen from ~200 ppm since the Neogene, beginning ~24 Myr ago. Changing [CO2]a affects plant carbon-water balance, with implications for growth, drought tolerance and vegetation shifts. The evolution of C4 photosynthesis improved plant hydraulic function under low [CO2]a and preluded the establishment of savannahs, characterized by rapid transitions between open C4-dominated grassland with scattered trees and closed forest. Understanding directional vegetation trends in response to environmental change will require modelling. But models are often parameterized with characteristics observed in plants under current climatic conditions, necessitating experimental quantification of the mechanistic underpinnings of plant acclimation to [CO2]a. We measured growth, photosynthesis and plant-water relations, within wetting-drying cycles, of a C3 tree (Vachellia karroo, an acacia) and a C4 grass (Eragrostis curvula) grown at 200, 400 or 800 ppm [CO2]a. We investigated the mechanistic linkages between trait responses to [CO2]a under moderate soil drying, and photosynthetic characteristics. For V. karroo, higher [CO2]a increased assimilation, foliar carbon:nitrogen, biomass and leaf starch, but decreased stomatal conductance and root starch. For Eragrostis, higher [CO2]a decreased C:N, did not affect assimilation, biomass or starch, and markedly decreased stomatal conductance. Together, this meant that C4 advantages in efficient water-use over the tree were maintained with rising [CO2]a. Acacia and Eragrostis acclimated differently to [CO2]a, with implications for their respective responses to water limitation and environmental change. Our findings question the carbon-centric focus on factors limiting assimilation with changing [CO2]a, how they are predicted and their role in determining productivity. We emphasize the continuing importance of water-conserving strategies in the assimilation response of savannah plants to rising [CO2]a.

Generalist trophic ecology in a changing habitat: The case of the four‐striped mouse in a woody‐encroached savannah

AbstractTrophic generalists tolerate greater habitat change than specialists; however, few studies explore how generalist trophic ecology is affected. We established how the trophic ecology of an extreme generalist, Rhabdomys pumilio, changed in relation to a directionally changing woody‐encroached savannah in Eastern Cape, South Africa by investigating (a) foraging behaviour, (b) trophic niche and (c) feedback effects. (a) Giving‐up densities showed that R. pumilio preferred foraging in subcanopy microhabitat during the night as a result of lower thermoregulatory costs, but had similar preferences for sub‐ and intercanopy microhabitats during the day. (b) An isotope analysis revealed that the dietary composition and trophic niche occupied by R. pumilio differed among tree canopy cover levels (0%, 30% and 80%), which appeared to be related to changes in C4 grass material and invertebrate availability. (c) Artificial seed patches suggested that R. pumilio was a potentially important postdispersal seed predator of the woody‐encroaching species, Vachellia karroo. Thus, an increase in tree canopy cover altered the trophic niche of R. pumilio by reducing foraging costs at night and providing alternative food resources in terms of availability and source. These findings demonstrate how an extreme generalist adapted to human‐induced habitat change through changes in its trophic ecology.