Fruit polymorphism in ephemeral species of Namaqualand. VI. Intermorphic competition among plants cultivated from dimorphic diaspores

Plants raised from disc and ray diaspores of Dimorphotheca sinuata, a polymorphic annual species from Namaqualand, were grown in replacement series. There were four plants per pot with disc to ray ratios of 4:0, 2:2 and 0:4. The plants were grown under different moisture and nutrient regimes. Disc plants were more aggressive than ray plants and thus the stronger competitors. Disc plants had a higher total dry matter in mixture than in monoculture under high moisture conditions. There was no difference in production between mixtures and monocultures of the ray plants. Ray plants were influenced more by disc plants than disc plants by ray plants. Both disc and ray plants were more successful when water and nutrients were freely available. Moisture was the main factor influencing intermorphic competition

Life form and species diversity on abandoned croplands, Roggeveld, South Africa

The Roggeveld consists of an island of Mountain Renosterveld (Fynbos biome) surrounded by Succulent Karoo biome vegetation. Since management of abandoned croplands depends on a better understanding of their succession sequences, vegetation recovery on abandoned croplands in the Roggeveld was studied using species and life form diversity parameters. Abandoned croplands of different ages were compared with each other and to the natural vegetation. Therophytes and chamaephytes were the most abundant life forms. Chamaephytes made an overwhelming contribution to the relative cover. Species-area curves (exponential function) differed significantly between the abandoned croplands and natural vegetation. Species richness increased with time since abandonment but no similar increase in species evenness, Shannon or Simpson indices were found. A regression of species richness against age of abandoned cropland predicted that an abandoned cropland of approximately 33 years should be as species rich as the natural vegetation, but a principal cooordinate analysis of floristic data indicated that all the plots were floristically still extremely different from the natural vegetation. Across all nine survey plots only 15 species contributed to a high cover on the plots. Vegetation recovery on abandoned croplands in the Roggeveld occurs naturally, yet the rate of recovery varies among the life forms.The National Research Foundation under grant number 61277.http://www.tandfonline.com/loi/tarf20nf201

Species-area relationships in the Hantam-Tanqua-Roggeveld, Succulent Karoo, South Africa

The Hantam-Tanqua-Roggeveld subregion is part of the Succulent Karoo hotspot of biodiversity which stretches along the southwestern side of South Africa and Namibia. Forty Whittaker plots were surveyed in the spring of 2005, in eight vegetation associations, to gather diversity data for the Hantam, Tanqua Karoo and Roggeveld areas. Seven plot sizes were used to construct species–area curves using three different models namely: the untransformed linear function, the power function and the exponential function. In general, the power and exponential functions produced a more significant fit to the data than the untransformed linear function. Linear regressions using environmental parameters indicated that altitude, mean annual precipitation and mean annual temperature were significant predictors of species richness at the 1, 10, 100 and 1000 m2 scales. To illustrate the variation in species–area curves and species richness across the landscape, a transect through the study area is discussed. The transect stretches eastwards from the Tanqua Karoo across the escarpment into the Roggeveld and crosses five different vegetation associations. Differences between associations were found in species richness in the 1000 m2 plots. Each association also produced species–area curves with their own characteristics. Slope values for the samples within an association did not differ significantly, although the intercept value often did. Comparisons between associations along the transect revealed significant differences in the slope value between the associations, except for the Dicerothamnus rhinocerotis Mountain Renosterveld which did not differ significantly from the associations bordering it on either side.The Critical Ecosystem Partnership Fund (CEPF) through the Succulent Karoo Ecosystem Plan/Program (SKEP) initiative and the National Research Foundation under grant number 61277.http://www.springerlink.com/content/0960-3115/nf201

Guiding conservation efforts in the Hantam–Tanqua–Roggeveld (South Africa) using diversity parameters

The Hantam–Tanqua–Roggeveld subregion falls within the Succulent Karoo and Fynbos Biomes, which are both recognised as global biodiversity hotspots that should be conserved. The objective of this study was to gather baseline biodiversity information that can be used to guide conservation efforts. A total of 40 Whittaker plots were surveyed in the subregion and the various diversity parameters calculated from the data were compared across the subregion and to available data for the Succulent Karoo and Fynbos Biomes. Species richness per 1000 m2 ranged from nine to 100 species across the subregion. Species richness for all plot sizes < 1000 m2 was significantly lower for the Tanqua Karoo than for both the Winter Rainfall Karoo and Mountain Renosterveld. The latter two areas did not differ significantly from each other with regard to species richness. Species richness was significantly higher only at the 1000 m2 scale in the Mountain Renosterveld compared to the Winter Rainfall Karoo. Evenness and Shannon and Simpson indices did not differ significantly between the Mountain Renosterveld and Winter Rainfall Karoo; however, these values were significantly higher than for the Tanqua Karoo. A principal coordinate analysis of species richness data at seven plot sizes produced three distinct clusters. One cluster represented the Tanqua Karoo, with low species richness, evenness, and Shannon and Simpson indices. Another cluster represented mostly Mountain Renosterveld vegetation, which was characterised by a high species richness, evenness, and Shannon and Simpson indices. The third cluster was formed by the remaining Mountain Renosterveld plots as well as the Winter Rainfall Karoo plots. The high species richness values found in the various vegetation units can add valuable information to the conservation planning arena by providing information on biodiversity parameters and their spatial distribution. This information can assist with conservation efforts in the Hantam, Tanqua and Roggeveld areas. CONSERVATION IMPLICATIONS: Conservation and development of the Hantam–Tanqua– Roggeveld subregion is hampered by a lack of information on floristic diversity. The results of the current study indicated areas of low diversity and contrasting areas of high diversity. These data can be used to guide effective conservation and management of the floristic diversity.The Critical Ecosystem Partnership Fund (CEPF) through the Succulent Karoo Ecosystem Plan/Programme (SKEP) initiative and the National Research Foundation under grant 61277.http://www.koedoe.co.za/nf201

Population biology of Elaeodendron transvaalense Jacq. in the presence of harvesting

Elaeodendron transvaalense Jacq. is one of the medicinal plant species commonly used by people in the Venda region. The species is known to treat a variety of diseases. It is widely used and important to traditional healers. Because of this, it found its way into the muthi markets, and it is among the seven most commonly traded plant species in the Venda region. This study investigated the impact of bark harvesting on the population structure of this species. The study revealed that although the level of bark harvesting is high, the species is able to resist that stress since it is a fine-grained species. The population also showed the ability to regenerate as it exhibited an inverse J-shaped curve. The crown health status was generally good although some individuals, contributing 9% of the sample, had dead crowns, which are a cause for concern. A linear relationship was noticed between areas harvested and stem circumference, which is understandable considering the large surface area of harvestable bark on bigger individuals.National Research Foundation of South Africahttp:// www.revistaphyton.fund-rumuloraggio.org.arhb201

Vachellia erioloba dynamics over 38 years in the Kalahari Gemsbok National Park, South Africa

Vachellia erioloba is a keystone tree species in the southern Kalahari. This long-term study over nearly four decades tracks two populations in different landscapes (the interior sandy duneveld versus the clayey Nossob riverbed) of a large conservation area and offers valuable data on this species under natural soil moisture conditions and with limited anthropogenic influences. In 1978, 18 trees were permanently marked in a 1 ha plot in the interior duneveld of the Kalahari Gemsbok National Park (Dankbaar site). In the Nossob riverbed all trees in a 1 ha plot were surveyed in 1979 (Grootkolk site). At both sites, tree height and stem circumference were subsequently measured at irregular intervals until 2016 in order to investigate growth rates and population structure. Of the 18 marked trees at Dankbaar, six died and three showed coppice regrowth following substantial dieback after a fire. A mean height increase of 60 mm/year was recorded and the mean height of the remaining uncoppiced trees was 6.8 m in 2016. Stem diameter growth rate per year varied widely between trees and between years with a mean value of 2.5 mm/year over the 38-year period. Growth rate calculated for three 10-year intervals varied. Using the mean growth rate derived in the current study and stem size of the dead trees, the mean age of the trees when they died was estimated. At the Grootkolk site, the position of the centroid in relation to the midpoint of the diameter class range suggests that this population is gradually becoming a mature to old population with limited recruitment. This was supported by the size class distribution curves. However, no differences between slopes or intercepts of the stem diameter size class distributions were found. Conservation implications: This study was conducted in a large conservation area, that is, a natural ecosystem excluding most of the anthropogenic threats that are present outside of the park. The study illustrated that in the duneveld the population studied was self-sustaining, with recruitment occurring and large individuals presumably dying of old age. Although fire caused a few individuals to coppice, no fire-related deaths were reported. In the Nossob riverbed, surveys started in a stand of predominantly young trees and the size class distribution at that stage already showed a lack of recruitment. This stand is ageing and will likely disappear at this site; however, new young stands are appearing at other sites in the Nossob riverbed. Under the current conditions with negligible anthropogenic influences, it therefore appears that some V. erioloba populations in the park are increasing in size while others are decreasing, but that overall the species will persist. The impact of global climate change on this species is, however, unknown

Evaluación de la magnitud y peligro de la cosecha de corteza de especies vegetales medicinales en la región de Venda, Provincia de Limpopo, Sudáfrica

The medicinal flora of the Venda region consists of a variety of species, which may potentially provide therapeutic agents to treat different diseases. Bark use for medicinal purposes has been reported for approximately 30% of the woody species (153 species) in the Venda region in southern Africa. However, only 58 plant species are commonly harvested for the medicinal properties in their bark and found in muthi shops in the region. These 58 species were scored for the possible threat of bark harvesting to the plant survival. Ethnobotanical studies indicate that the growing trade in indigenous medicinal plants in South Africa is posing a threat to the conservation and preservation of many plant species. Apart from pharmaceutical companies, trade in medicinal plants has become a way of making a living for some people. This study investigated the pattern of trade in medicinal plants by local markets in the Venda region, Limpopo Province, South Africa. Indications are that bark harvesting may threaten some of the plant species.La flora medicinal de la región de Venda consta de una variedad de especies, que potencialmente pueden proporcionar agentes terapéuticos para tratar diferentes enfermedades. El uso de la corteza con propósitos medicinales se ha informado para aproximadamente 30% de las especies leñosas (153 especies) en el sur de África, en la región de Venda. Sin embargo, sólo 58 especies vegetales son cosechadas por las propiedades medicinales en su corteza, y vendidas en tiendas muthi en la región. Estas 58 especies se clasificaron por la posible amenaza de cosecha de su corteza, relacionado con la supervivencia de las plantas. Estudios etnobotánicos indican que el creciente comercio de plantas medicinales indígenas en Sudáfrica está siendo una amenaza para la conservación y preservación de muchas especies vegetales. Además de las compañías farmacéuticas, el comercio de plantas medicinales se ha convertido en una forma de vida para algunas personas. Este estudio investigó el patrón de comercio de las plantas medicinales en los mercados locales en la región de Venda, Provincia de Limpopo, Sudáfrica. Los resultados indican que la cosecha de corteza puede amenazar algunas de las especies vegetales.Muthi is a term for traditional medicine in southern Africa. It has been derived from the Zulu language word for “tree” due to the fact that most traditional medicines are derived from trees.http://www.revistaphyton.fund-romuloraggio.org.aram201

Floristic composition, diversity and structure of the forest communities in the Kouilou Département, Republic of Congo

The objectives of the study were to classify, describe and map the forest communities in the study area and to investigate possible gradients in plant diversity. The study area comprised approximately 166 000 ha in the Kouilou Département, Republic of Congo, a section of land targeted for extensive future development. In total 156 forest sample sites were surveyed using the Braun-Blanquet method of phytosociology. Diversity of each plant community was expressed in terms of species richness; Shannon-Wiener index; exponent of Shannon-Wiener index; evenness; Fisher's alpha; Simpson’s index; and inverse Simpson index. Eleven plant communities were described and mapped at a much finer scale than has been done previously. The communities were arranged along two gradients: a degraded – relatively intact gradient and a wet – dry gradient. The least degraded communities, and consequently those with the highest conservation value, were the swamp forests and the okoumé forest. Overall, the values reported for the diversity parameters in the current study were within the range reported for other tropical forests in Central Africa. The study revealed a gradient between the coast (west) and the Mayombe mountain range (east) in plant diversity linked to topography and climate with plant diversity lowest at the coast. Furthermore, plant diversity was negatively related to the distance to human infrastructure. The forest communities appear to be fairly resilient to past anthropogenic disturbances, however, there is no historical analogue to the more severe types of forest destruction associated with some of the future developments anticipated, such as mechanized logging or mining.http://journals.cambridge.org/action/displayJournal?jid=TRO2017-06-30hb2017Centre for Wildlife ManagementPlant Scienc

Is the present Brackenridgea Nature Reserve large enough to ensure the survival of Brackenridgea zanguebarica Oliv.?

The Brackenridgea Nature Reserve is a 110 ha protected area established by the provincial Limpopo Department of Economic Development, Environment and Tourism as a way of protecting the population of Brackenridgea zanguebarica, a species classified as critically endangered in South Africa. In the whole of South Africa, the species is found in only one small area around Thengwe–Mafukani in Venda. It is threatened with extirpation due to high demand for its medicinal bark. This study investigated the adequacy of the reserve to conserve the species using a method established in 2001 by Burgman et al. This method involves 12 steps to quantify the risk of the decline or possible extinction of the species and takes current human activities, disturbances and the viability of the population into consideration for setting a conservation target. From the results, it was clear that more area is needed for the current population to survive beyond 50 years. Assuming the status quo, it will require 410 ha to maintain the population, whereas a 50% reduction in human-related activities, such as cultivation, harvesting and livestock grazing, will lower the required potential habitat to 203 ha and a conservation option, which allows for bark harvesting, will require 179 ha. CONSERVATION IMPLICATIONS: The results of this study will have conservation implication on management of viable species population within a nature reserve. It will require managers to take into consideration the reserve size in relation to potential habitats for the development of species under their management.http://www.koedoe.co.zaam201

Herbivore and human impacts on woody species dynamics in Maputaland, South Africa

Maputaland’s woodlands are under utilization pressure inside and outside conserved areas due to mounting densities of mammals in the former and increasing human utilization of vegetation in the latter. Conservation of this biodiversity hotspot requires a better understanding of vegetation dynamics. To this purpose, woodland vegetation structure was evaluated at three sites through size class distribution analysis and grain determination, a forestry concept here applied to woodlands. The three sites represented animal disturbance/utilization, human disturbance/utilization and no disturbance/utilization regimes for comparable periods. Common species occurrence patterns differed between sites. The woodlands of all three sites were mostly fine-grained forest-like vegetation units and followed fine-grained forest dynamics closely. The grain model performed successfully for the region’s woodlands and proved a good tool to improve vegetation dynamics understanding. In general, people and herbivores led to local extirpation of species and threatened both ecological structure and function of Maputaland’s woodlands. However, the fine grain status was considered positive, as it facilitated future management options by reducing time frames and scale of management actions to be applied.The South African National Research Foundation under Grant Number 2053522 and the University of Pretoria.http://forestry.oxfordjournals.org/hb201