Neoboutonia Macrocalyx Research Articles

Caractérisations Structurale, Floristique Et Biomasse Ligneuse Du Peuplement À Hagenia abyssinica Du Parc National De Kahuzi-Biega (Rift Albertin, RDC)

Hagenia abyssinica is a characteristic species of mountain forests in the Albertine Rift. In Kahuzi Biega National Park, the species is found between 2000 and 2600 m altitude. This study intended to characterize Hagenia monospecific forest by providing an account for its floristic composition, structure and biomass. Data were collected from 9 different plots of 1 hectare each located in 3 different sites (Tshivanga 2000-2250m asl; Mugabe and Kasirusiru 2400-2600m asl). Parameters including tree diameter ≥ 10cm, height, dead individuals and young shoots of Hagenia abyssinica were wetting the plot. The results showed that species richness was significantly low, varying between 8-24 species (p < 0.05, Df = 35); while the specific density was 565 ± 121 individuals. The Richness decreased with the increment of the species density of Hagenia. The similarity analysis revealed the influence/impact of the site/altitude on the species composition. The diametric structure showed a regressive dynamism within the population found between 2000 and 2200 m altitude, in which Hagenia specimens were replaced by the specimens of secondary forest species such as Sapium ellipticum, Macaranga neomilbraediana, Neoboutonia macrocalyx. Whereas, between 2400-2600 m altitude, there was a progressive dynamism with several Hagenia young shoots, with no mortality (χ2 = 487, p < 0.001). The average woody biomass was estimated at 108t / ha. This increased as Hagenia density decreased and vegetation became heterogeneous. Human disturbance and climate change effects in the region, could be the causes of variability observed in this population in the Kahuzi-Biega National Park.

Natural establishment of indigenous trees under planted nuclei: A study from a clear-felled pine plantation in an afrotropical rain forest

Applied nucleation has been proposed as a cost-effective reforestation alternative to large-scale re-planting or establishing plantations with exotic tree species. We tested applied nucleation in a regenerating clear-cut pine plantation in Kibale National Park, Uganda, where natural succession had been slow. We planted Neoboutonia macrocalyx, a relatively common indigenous pioneer tree species with animal dispersed seeds and a wide crown, in the pine plantation clear-cuts as seeds and transplanted seedlings. After six years of monitoring the growth of the nucleus trees we identified all naturally recruited seedlings under the nuclei and adjacent control sites without planted nuclei. We monitored the growth and turnover of the recruited seedlings for one year and examined the ground vegetation structure under the nuclei and control sites. We found that the N. macrocalyx nucleus trees had survived equally well if planted as seeds or transplanted seedlings and had attained heights up to ten meters tall. Understory vegetation structure under the established nuclei was less dense (P=0.001) and shorter (P=0.039) compared to control sites. We also found that natural recruitment of indigenous tree species under the nuclei was higher compared to control sites. The seedling density under the nuclei was significantly higher (P=0.035), and there was a significant difference in the composition of seedling communities (P=0.0001) with a larger number of different tree species found under the nuclei. We found that a viable seedling community had been established with a good potential to take over when planted nucleus trees eventually die. Our results show that planting nucleus trees can increase recruitment of indigenous tree species in locations where natural succession is otherwise slow.

Antiplasmodial compounds from the stem bark of Neoboutonia macrocalyx pax

Ethnopharmacological relevanceThe plant Neoboutonia macrocalyx has been reported in traditional medicine to be used in the treatment of malaria. Aim of the studyTo study the in vitro antiplasmodial activity of compounds from the stem bark of Neoboutonia macrocalyx. Materials and methodsCompounds were extracted and purified from stem bark of Neoboutonia macrocalyx and their structure identified and confirmed by spectroscopic methods.The crude ethyl acetate extract, aqueous extract and the isolated compounds were evaluated for antiplasmodial activity against the chloroquine sensitive Sierra Leone I (D6) and chloroquine-resistant Indochina I (W2) strains of Plasmodium falciparum. ResultsChemical investigation of the ethyl acetate extract of Neoboutonia macrocalyx bark resulted in the identification of one new diterpenoid; neoboutomacroin (1) in addition to the four known compounds which included, a phenanthrene; 3,6-dihyroxy-1,7-dimethyl-9-methoxyphenanthrene (2), a sterol; 3-O-Acetyloleuritolic acid (3) and two diterpenoids; simplexin (4) and montanin (5). Compounds 1 and 5 displayed good antiplasmodial activity of IC50 values less than 10μg/mL against both strains. However, all the compounds tested displayed high cytotoxic activity against MRC5 cell line with IC50 less than 10μM. ConclusionsDespite an indirect in vitro antiplasmodial activity of some compounds isolated from the stem bark of Neoboutonia macrocalyx, the identification of these bioactive compounds indicates that they may play a role in the pharmacological properties of this plant.

Communities of Galling Insects onNeoboutonia macrocalyxTrees in Continuous Forests and Remnants of Forest Fragments in Kibale, Uganda

The responses of Afrotropical galling insects to habitat fragmentation are poorly understood. We studied the influence of fragmentation and fragment characteristics on communities of galling insects on Neoboutonia macrocalyx trees, in six forest fragments around Kibale National Park, Uganda. Insect galls were collected from six randomly cut tips of branches from each of 10 randomly selected trees in every forest five times over a 10-month period.Atotal of 6090 individuals representing five galler species were recorded. The species richness, density and community composition of gallers were significantly different among the forests. Continuous forest areas showed similar community characteristics but some fragments were similar to continuous forests and others differed from them. None of the fragment characteristics measured (size, host-tree density, distance from continuous forest boundary and from nearest neighbour) explained differences in community measures (species richness and density) of gallers. Our results indicate that habitat fragmentation can lead to a decline in the galler species richness and to changes in the density and composition of galling insects, emphasizing the need to maintain large continuous forested areas as a long-termstrategy for their conservation. However, the similarity of community measures of gallers of some fragments and continuous forests suggest that the preservation of fragments might provide an important complement to the conservation of galling insects, highlighting the need to include also these habitats in management and conservation priorities. However, our study did not identify habitat characteristics to predict which fragments have a high value for gallers, indicating that processes that produced high-value fragments might have been stochastic. Our results caution against making generalizations on the use of easily measureable fragment characteristics (e.g. size and distance of isolation) when designing and planning conservation areas.

Bottom-up impact on the cecidomyiid leaf galler and its parasitism in a tropical rainforest.

The relative importance of host-plant resources, natural enemies or their interactions in controlling the population of galling insects and their parasitism is poorly known for tropical gallers. In this study, we assessed the impacts of plant quality and density of host trees in regulating the densities of a galler species, the cecidomyiid leaf galler (Cecidomyiini sp. 1EJV) and its parasitoids and inquilines on Neoboutonia macrocalyx trees in Uganda. We manipulated the nutritional quality (or vigour)and the resource concentration with four levels each of fertilization and the group size of host tree. We then recorded the effects of these treatments on the growth rate and total leaf area of host plants, the density of gallers and their mortality by parasitoids and inquilines. Higher levels of fertilization and host density resulted in significantly higher total leaf area than did ambient nutrient levels, and lowest tree densities, respectively. Fertilization also caused significant change in the growth rate of leaf area. Both higher fertilization and host density caused higher density of gallers. Total leaf area was positively associated with galler density, but within galled replicates, the galled leaves were larger than the ungalled leaves. Although highest levels of fertilization and density of host trees caused significant change in the densities of parasitoids, the rate of parasitism did not change. However, tree-density manipulations increased the rate of inquilinism, but on a very low level. Our results demonstrate a trophic cascade in the tropical galler and its parasitoids as a response to bottom-up effects.

Bottom‐up manipulations alter the community structures of galling insects and gall morphs on Neoboutonia macrocalyx trees in a moist tropical rainforest

Abstract The effects of bottom‐up forces on the community structure of tropical insect gallers and within species variation in gall morphotype assemblages are not well understood. We tested the roles of increased nutritional quality and density of host plants with respect to structuring the galling insect communities and gall morphotype assemblages on Neoboutonia macrocalyx trees in Uganda. Plant nutritional quality and resource concentration were manipulated with four levels of fertilization and the group size of trees, respectively. After applying these treatments in May 2011, gallers established naturally on experimental replicates. Five months later, we sampled gallers and recorded their numbers and the different morphotypes. We analyzed the effects of treatments on the structures of galler communities and gall morphotype assemblages. We recorded 5237 individuals, representing four galler species. One species, Cecidomyiid leaf galler, was represented by three morphologically distinct galls. Fertilization, host tree density and their interactions significantly changed the structures of galler species communities and gall morphotype assemblages. The results of the present study demonstrate the important role of bottom‐up factors in structuring galler communities and the gall morphotype assemblages. These changes are likely caused by differential responses of different galler species and gall morphs to plant quality or quantity changes.

Cycloartane triterpenes from the leaves of Neoboutonia macrocalyx L.

Neoboutonia macrocalyx is used by people in south western Uganda around Kibale National Park in the treatment of malaria. Phytochemical investigation on the leaves of this plant led to the isolation of nine cycloartane triterpenes (1–9) and one phenanthrene; 7-methoxy-2,8 dimethyl-9,10-dihydrophenantherene-3,6 diol (10) along with three known compounds which included 22-de-O-acetyl-26-deoxyneoboutomellerone (11), mellerin B (12) and 6-hydroxystigmast-4-en-3-one (13). The chemical structures of the compounds were established mainly through a combination of spectroscopic techniques. The isolated compounds were evaluated for antiplasmodial activity against the chloroquine-resistant FcB1/Colombia strain of Plasmodium falciparum and for cytotoxicity against the KB (nasopharyngeal epidermoid carcinoma) and MRC-5 (human diploid embryonic lung) cells. Seven out of 13 compounds exhibited good antiplasmodial activity with IC50 of ⩽5μg/ml with two compounds exhibiting low cytotoxicity and five compounds having significant cytotoxicity.

Spatial and temporal variation in community composition of herbivorous insects on Neoboutonia macrocalyx in a primary tropical rain forest

Abstract:Spatial and temporal variation of tropical insect communities has rarely been studied, although such variation influences estimates of global species richness. Therefore, we compared spatial and temporal variation of herbivorous insect communities on Neoboutonia macrocalyx trees among seven sites over 1 y in a primary tropical rain forest in Kibale National Park, Uganda. The distance between the study sites varied from 4.8 to 31.2 km and altitudinal differences ranged from 20 to 242 m. Permutational multivariate analysis of variance (PERMANOVA) revealed significant spatial changes in community composition of the herbivorous insects and study sites differed also in insect abundance (6.9–26.2 individuals m−2 of leaf area). This is likely to be caused by differences in vegetation, altitude and microclimate among the study sites. The similarity of insect species composition was negatively correlated with geographic and altitudinal distances among sites and positively correlated with the similarity of tree community composition. Species richness varied significantly between sampling dates, ranging from 33 to 41 species. Also community compositions changed between sampling dates, which likely follows from marked seasonal changes in climate and the phenology of other host plants used by the generalist insect species also living on Neoboutonia macrocalyx. In general our study supports the idea of high variability of herbivorous insect communities in primary rain forests even at a small spatial scale. This should be considered when estimations of insect biodiversity are made.

Microclimate and tree community linked to differences in lepidopteran larval communities between forest fragments and continuous forest

ABSTRACTAim We aim to assess the impact of forest fragmentation on lepidopteran larval community and study the associations of microclimate and tree community with lepidopteran assemblage.Location Kibale National Park, Uganda.Methods We investigated the effects of forest fragmentation on leaf herbivory, density of lepidopteran caterpillars, species richness and diversity as well as the composition of herbivorous lepidopteran larval community. Microclimate, size of the fragment, distance to the continuous forest, and tree diversity were studied as possible explanatory factors. We sampled 10 Neoboutonia macrocalyx Pax. (Euphorbiaceae) trees in each fragment during dry and rainy season, total of four times, in a year to cover the seasonal variation.Results The rates of herbivory, total larval density and species richness were significantly lower in the forest fragments than in the continuous forest but species diversity expressed as Fisher's alpha did not differ. The dominance structure and community composition of the larval communities in the fragments was different from that of the continuous forest. None of the differences we observed were related to the fragment area or distance to the continuous forest. Instead, we found an indication of association between the herbivore and the tree communities. The fragments had significantly lower humidity during most of the day and higher temperature during the afternoons (14–17 h), which might partially explain the differences in lepidopteran larval communities.Main conclusions Decreased larval density and species richness as well as differences in the community composition and structure all highlight the importance of large continuous forest areas for maintaining larval biodiversity.

Tigliane Diterpenoids from the Stem Bark of Neoboutonia macrocalyx

Neoboutonia macrocalyx is a plant used by traditional healers among the Meru community in Kenya. Chromatographic fractionation of the petroleum ether and dichloromethane extracts of this plant yielded one known (1) and three new tigliane-type diterpenoids (2-4). The chemical structures of the isolated compounds were established through spectroscopic data interpretation.

Anti-plasmodial activity and toxicity of extracts of plants used in traditional malaria therapy in Meru and Kilifi Districts of Kenya

The methanol and aqueous extracts of 10 plant species ( Acacia nilotica, Azadirachta indica, Carissa edulis, Fagaropsis angolensis, Harrissonia abyssinica, Myrica salicifolia, Neoboutonia macrocalyx, Strychnos heningsii, Withania somnifera and Zanthoxylum usambarensis) used to treat malaria in Meru and Kilifi Districts, Kenya, were tested for brine shrimp lethality and in vitro anti-plasmodial activity against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum (NF54 and ENT30). Of the plants tested, 40% of the methanol extracts were toxic to the brine shrimp (LD 50 < 100 μg/ml), while 50% showed in vitro anti-plasmodial activity (IC 50 < 100 μg/ml). The methanol extract of the stem bark of N. macrocalyx had the highest toxicity to brine shrimp nauplii (LD 50 21.04 ± 1.8 μg/ml). Methanol extracts of the rest of the plants exhibited mild or no brine shrimp toxicity (LD 50 > 50 μg/ml). The aqueous extracts of N. macrocalyx had mild brine shrimp toxicity (LD 50 41.69 ± 0.9 μg/ml), while the rest were lower (LD 50 > 100 μg/ml). The methanol extracts of F. angolensis and Zanthoxylum usambarense had IC 50 values <6 μg/ml while the aqueous ones had values between 6 and 15 μg/ml, against both chloroquine-sensitive and resistant P. falciparum strains. The results support the use of traditional herbs for anti-malarial therapy and demonstrate their potential as sources of drugs.

Succession and Regeneration Patterns of East African Mountain Forests. A Review

Regeneration and succession processes in montane forests of Kenya and parts of Ethiopia were investigated. The slowly growing camphor tree, Ocotea usambarensis, regenerates mainly by suckers from old root systems. Undamaged seeds were very rarely seen, and, apparently are viable only for a few days. After natural breakdown of an old tree, the gap is filled by fast growing species, mainly Macaranga kilimandscharica and Neoboutonia macrocalyx, in the shade of which the young Ocotea suckers can establish. After the death of the secondary species, whose germination requires full sunlight and is inhibited in the shade, the Ocotea forest recovers. Large scale logging of Camphor trees predominantly destroys the regeneration of Ocotea and leads to secondary forest types, which regenerate in own cycles. The high number of big game was found to be without impact on the natural regeneration of Ocotea. The Cassipourea malosana dominated forest regenerates as a mosaic-climax without a single species becoming dominant. Cedar forests dominated by Juniperus procera regenerate most efficiently after fire. Without recurrent burning, the forests of the lower and middle part of the montane zone, regenerate to climax associations dominated by broad-leaved trees as Olea capensis ssp. hochstetteri, Olea europaea ssp. cuspidata and Podocarpus latifolius. On higher altitudes Juniperus procera always remains dominant even if fire does not occur for a longer time period. The high population density especially of buffaloes seems to inhibit successful regeneration in many parts of the Juniperion, due to intensive browsing and in particular trampling. The African Bamboo, Sinarun- dinaria alpina, shows a distinct growth cycle and can grow for extremely long periods in the vegetative state before flowering, especially so at the borders of its area. After flowering and dying of the bamboo, in most areas a dense Sambucus africana shrub is formed into which bamboo is invading from old rhizomes again. In Ethiopia, regeneration occurs directly, without an interspersed Sambucus stage. The uniform age of the Hagenia stands suggests that regeneration in these forests occurs suddenly after a disturbing event. Germination tests yielded, that Hagenia seeds are not germinating unless the competing undergrowth is removed. As fire is the only natural factor able to clear the grass layer of larger areas, it is assumed, that the reproduction of the subalpine forests depends on occasional burning.

Seasonality of insect herbivory on the leaves of Neoboutonia macrocalyx in the Kibale National Park, Uganda

SummaryThe seasonality of herbivory on the leaves of Neoboutonia macrocalyx Pax. in Kibale Forest National Park, Uganda, was studied. A total of 2929 fallen leaves was collected during 15 months under randomly‐selected trees in three different habitats; natural forest and two selectively cut forest sites. The percentage of leaf area eaten and leaf size were estimated. Leaf herbivory was highly seasonal and correlated with rainfall in the previous 2 months, but less than 100 mm monthly rainfall had no effect. There was no correlation between leaf size and rainfall. Although Kibale Forest has two wet seasons, insect feeding on leaves had only one peak during the major rainy season from September to December. Three to four months after peak herbivory, leaves had very low rates of insect damage. Habitat had only a small effect on the amount of insect feeding. The sampling time accounted for 71% of variation in leaf herbivory. New leaves were formed continuously year‐round. The constant leaf production by Neoboutonia trees may be an adaptation to escape generalist herbivorous insects which might be synchronized with the major wet season when the leaf flush of the most other deciduous species occurs. Thus, the availability of fresh leaves is not acting as a regulating factor in seasonality of Neoboutonia herbivory.

Growth Rates of Important East African Montane Forest Trees, With Particular Reference to Those of Mount Kenya

The length increments of seedlings and branches, and the extension growth of specimens of different age classes of 12 forest tree species were measured on Mt Kenya between May 1992 and July 1995.Of all examined species, the camphor tree, Ocotea usambarensis showed the lowest growth rates. The growth rates of other species of the primary forests, namely Zanthoxyllum gillettii and Vitex keniensis were between 30 and 200 % higher. The seedlings of Vitex outgrew even pioneer species such as Macaranga kilimandscharica Pax and Neoboutonia macrocalyx. These trees showed growth rates at least twice as high as those of the primary species.Juniperus procera was found to be the fastest growing species in the cedar forest, underlining its success in forming dense stands after a fire. Only young Podocarpus latifolius showed a similar fast growth. Olea europaea ssp. cuspidata, Olea capensis ssp. hochstetteri and Cassipourea malosana had nearly equal growth rates, however, considerably lower than those of Juniperus procera and Podocarpus latifolius.Hagenia abyssinica fell within the range of the fast growing species, illustrating the ability of this species to regenerate very fast under suitable conditions.