oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 16 )

2018 ( 181 )

2017 ( 156 )

2016 ( 198 )

Custom range...

Search Results: 1 - 10 of 113457 matches for " Margaretha W. van Rooyen "
All listed articles are free for downloading (OA Articles)
Page 1 /113457
Display every page Item
Floristic Composition, Diversity and Structure of the Rainforest in the Mayoko District, Republic of Congo  [PDF]
Margaretha W. van Rooyen, Noel van Rooyen, Edmond S. Miabangana, Gilbert Nsongola, Caroline Vasicek Gaugris, Jér?me Y. Gaugris
Open Journal of Forestry (OJF) , 2019, DOI: 10.4236/ojf.2019.91002
Abstract: Botanically, the Mayoko district is known only through anecdotal descriptions made in the colonial era. The present study was undertaken as part of the prerequisite for a mining feasibility study where a benchmark of the floristic composition, diversity and structure of the vegetation was needed to evaluate potential biodiversity offset areas and to guide species selection for post-mining re-vegetation. The study area comprised approximately 160,000 ha and 235 sample sites were surveyed using the Braun-Blanquet method of phytosociology. Diversity of each plant association was expressed in terms of various diversity parameters. Twelve associations were described and mapped. The associations ranged from highly disturbed and degraded to fairly intact forest associations. A wet to dry gradient and permanently inundated to temporary inundated gradient could also be distinguished. The approach followed here proved remarkably robust in illustrating the complexity in a topographically complex region of the Chaillu Massif. The data provided a high level of insight into the possible dynamics of the rainforest and indications as to possible successional pathways. This information provides a better level of understanding of forest structure and evolution potential than studies limited to trees, remote sensing carbon assessments, or time change series.
Guiding conservation efforts in the Hantam–Tanqua–Roggeveld (South Africa) using diversity parameters
Helga van der Merwe,Margaretha W. van Rooyen
Koedoe : African Protected Area Conservation and Science , 2011, DOI: 10.4102/koedoe.v53i1.1018
Abstract: 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. How to cite this article: Van der Merwe, H. & Van Rooyen, M.W., 2011, ‘Guiding conservation efforts in the Hantam–Tanqua–Roggeveld (South Africa) using diversity parameters’, Koedoe 53(1), Art. #1018, 9 pages. d
Vegetation of the Hantam-Tanqua-Roggeveld subregion, South Africa. Part 1: Fynbos Biome related vegetation
Helga van der Merwe,Margaretha W. van Rooyen,Noel van Rooyen
Koedoe : African Protected Area Conservation and Science , 2008, DOI: 10.4102/koedoe.v50i1.130
Abstract: The Succulent Karoo Hotspot stretches along the western side of the Republic of South Africa and Namibia. A lack of botanical information on the Hantam-Tanqua-Roggeveld area of the Succulent Karoo Hotspot was identified during the SKEP (Succulent Karoo Ecosystem Plan) process. A grant from CEPF (Critical Ecosystem Partnership Fund) funded a study to produce a vegetation map of the area to serve as baseline for ecosystem management. Vegetation surveys were conducted over an area of more than three million hectares from August to October 2004. Two major floristic units were identified, namely the Fynbos Biome related (Mountain Renosterveld) and Succulent Karoo Biome related units. An analysis of the floristic data of the predominantly Mountain Renosterveld vegetation unit is presented in this paper. Three associations were identified, which were subdivided into nine subassociations, one of which contains four variants. The vegetation units are described in terms of their species composition and their relationships with the physical environment. A vegetation map is provided depicting the geographical distribution of the different vegetation types. The main threat to the vegetation of the region identified by the farming community was a lack of infrastructure.
Landscapes in the Kalahari Gemsbok National Park, South Africa
Margaretha W. van Rooyen,Noel van Rooyen,Jacobus du P. Bothma,Hendrik M. van den Berg
Koedoe : African Protected Area Conservation and Science , 2008, DOI: 10.4102/koedoe.v50i1.154
Abstract: A landscape map of the Kalahari Gemsbok National Park is presented. Mapping is at a finer scale than previous vegetation and habitat maps for the same area. The landscapes were grouped into seven large classes and a total of 20 landscapes were mapped. A description of the terrain morphology, soil and vegetation of each landscape is provided. Landscapes that are focal points for the large animals of the region include the calcrete outcrops, riverbeds and pans. These landscapes cover only about 10% of the total area of the region. This map can be used as basis for park planning, management, research and other applications.
Plant diversity and flowering displays on old fields in the arid Namaqua National Park, South Africa
Margaretha (Gretel) W. van Rooyen,Ronel Henstock,Noel van Rooyen,Helga van der Merwe
Koedoe : African Protected Area Conservation and Science , 2010, DOI: 10.4102/koedoe.v52i1.1004
Abstract: National Park and to investigate whether the time since abandonment has impacted on the diversity and mass flowering displays. Sixty-two old field sample sites were surveyed using the Braun-Blanquet method. Floristic data were analysed to produce a hierarchical classification, while a principal coordinates analysis was used to establish whether the ordination supported the classification. Species richness (total number of taxa), as well as the Shannon-Wiener diversity index, was calculated per vegetation unit for the different life forms. Four old field communities were identified, each containing a unique complement of species, which differed in their potential to produce a mass flowering display. On the Skilpad section of the park, Ursinia cakilefolia dominated the spectacular mass floral displays for which the park has become well known. Old fields in other parts of the park did not produce the same spectacular displays. Although total and perennial species richness did not differ significantly with time since abandonment, the richness of annual species, in particular of the showy annual species, decreased with time since abandonment. The relative contribution of the perennial species to vegetation cover increased with time since abandonment, whereas the relative contribution made by showy annual species to vegetation cover declined with time since abandonment. Although species composition and the potential to produce mass flowering displays of the four communities differed, diversity parameters were similar. However, to maintain a flower display for tourists on the Skilpad section, a degree of disturbance is essential. Conservation implication: Although deliberate disturbance is not desirable in a national park, we find that some disturbance is essential to maintain a spectacular flowering display. However, these intentionally disturbed old fields cover only a small proportion of the total area of the park. All other old fields in the park should not be disturbed, and should be allowed to recover naturally. How to cite this article: Van Rooyen, M.W., Henstock, R., Van Rooyen, N. & Van der Merwe, H., 2010, ‘Plant diversity and flowering displays on old fields in the arid Namaqua National Park, South Africa’, Koedoe 52(1), Art. #1004, 7 pages. DOI: 10.4102/koedoe.v52i1.1004
Vegetation of the Hantam-Tanqua-Roggeveld subregion, South Africa Part 2: Succulent Karoo Biome related vegetation
Helga van der Merwe,Margaretha W. van Rooyen,Noel van Rooyen
Koedoe : African Protected Area Conservation and Science , 2008, DOI: 10.4102/koedoe.v50i1.148
Abstract: The Hantam-Tanqua-Roggeveld subregion lies within the Succulent Karoo Hotspot that stretches along the western side of the Republic of South Africa and Namibia. This project, carried out to document the botanical diversity in the Hantam-Tanqua-Roggeveld subregion, was part of a project identified as a priority during the SKEP (Succulent Karoo Ecosystem Programme) initiative in this Hotspot. Botanical surveys were conducted in an area covering over three million hectares. Satellite images of the area and topocadastral, land type and geology maps were used to stratify the area into relatively homogeneous units. An analysis of the floristic data of 390 sample plots identified two major floristic units, i.e. the Fynbos Biome related vegetation and the Succulent Karoo Biome related vegetation. A description of the vegetation related to the Succulent Karoo Biome is presented in this article. Seven associations, 16 subassociations and several mosaic vegetation units, consisting of more than one vegetation unit, were identified and mapped. Various threats to the vegetation in the region were identified during the survey and are briefly discussed.
Springbok behaviour as affected by environmental conditions in the Kalahari
Hein Stapelberg,Margaretha W. van Rooyen,Jacobus du P. Bothma,Michael J. van der Linde
Koedoe : African Protected Area Conservation and Science , 2008, DOI: 10.4102/koedoe.v50i1.143
Abstract: Springbok behavioural ecology in the Kalahari was examined with the use of public questionnaires and field forms. Springbok favoured grass and forbs overall more than shrubs and trees, but diet selection was influenced by time of day and season. Feeding was the most common activity and the frequency of occurrence varied during the day and between seasons. Weather and microhabitat conditions were found to have a significant effect on the feeding behaviour. Springbok fed in direct sunlight in the mornings and moved into the shade during the afternoon. More time was spent feeding in the shade during the warmer months than during the colder months, especially under northerly to northeasterly wind directions. Natural licks were commonly utilised. Herd sizes were found to increase during the cold-dry season and decrease during the hot-wet season. Springbok and blue wildebeest appeared to avoid competition by niche separation. The study showed that springbok behaviour was significantly affected by environmental conditions. These results imply that changes in climatic conditions, such as those predicted by climate change, or changes in vegetation structure due to degradation, can negatively affect springbok behaviour.
Technique to study the impact of large herbivores on woody vegetation within piospheres
J. Brits,M.W. van Rooyen,N. van Rooyen
Koedoe : African Protected Area Conservation and Science , 2000, DOI: 10.4102/koedoe.v43i2.198
Abstract: A continuously sampled transect away from a watering point provides good results in situations where geology and soil type remain constant, but is unsuitable to apply where regular changes in soil type occur. A comparison was made between a continuously sampled transect and sampling taken at intervals along the transect. An analysis of variance indicated no significant differences in any of the variables obtained by means of the two sampling methods. The advantage of interval sampling is that, within each zone, areas with the same soil type can be selected in order to avoid environmental heterogeneity. A comparison between transects made in different directions from the watering point yielded no significant differences in any of the structural variables of the woody vegetation at the same distance from the watering point. Therefore, combining transects from different directions to attain a representative sample away from the watering point was an acceptable practice. It is recommended that the original data be smoothed and the logistic function used to model the impact of large herbivores on the structure of the woody vegetation around watering points.
Dignity, religion and freedom of expression in South Africa
Jacobus C.W. van Rooyen
HTS Theological Studies/Teologiese Studies , 2011, DOI: 10.4102/hts.v67i1.1030
Abstract: The issue that this article dealt with is whether, in South African law, speech that infringes upon the religious feelings of an individual is protected by the dignity clause in the Constitution of the Republic of South Africa. The Constitution, as well as the Broadcasting Code, prohibits language that advocates hatred, inter alia, based on religion and that constitutes incitement to cause harm. Dignity, which is a central Constitutional right, relates to the sense of self worth which a person has. A Court has held that religious feelings, national pride and language do not form part of dignity, for purposes of protection in law. The Broadcasting Complaints Commission has, similarly, decided that a point of view seriously derogatory of ‘Calvinistic people’ blaming (some of) them as being hypocritical and even acting criminally is not protected by dignity. It would have to be accompanied by the advocacy of hatred as defined previously. The author, however, pointed out that on occasion different facts might found a finding in law that religion is so closely connected to dignity, that it will indeed be regarded as part thereof. How to cite this article: Van Rooyen, J.C.W., 2011,‘Dignity, religion and freedom of expression in South Africa’, HTS Teologiese Studies/Theological Studies 67(1), Art. #1030, 6 pages. DOI:10.4102/hts. v67i1.1030
Impact of harvesting and fire on Phragmites australis reed quality in Tembe Elephant Park, Maputaland
M.W. van Rooyen,C.A. Tosh,N. van Rooyen,W.S. Matthews
Koedoe : African Protected Area Conservation and Science , 2004, DOI: 10.4102/koedoe.v47i1.76
Abstract: In Maputaland, South Africa, the common reed (Phragmites australis) is used extensively for hut building, fencing, craftwork and thatching. As a result of over-harvesting most reed beds in communal areas have been degraded and are no longer producing reeds of the desired quality. At present the most productive reed beds are all found in conservation areas. The KwaMsomi area of the Muzi Swamp in the Tembe Elephant Park has been allocated to the Sibonisweni community for harvesting purposes. This community has recently requested Ezemvelo KwaZulu-Natal Wildlife for additional areas for harvesting on the grounds that the current site was no longer yielding reeds of suitable quality. The main objective of this study was therefore to determine whether there was a decline in reed quality in the KwaMsomi harvested area. The results of this study suggest that harvested areas contained more thin, short reeds than unharvested areas. Fire can be used to increase reed diameter in harvested areas, but will not significantly affect reed height. Ideally, reeds should only be harvested after the active growth period, when most of the nutrient reserves have been translocated to the rhizomes and the buds are still dormant. To improve reed quality a three-year rotational harvesting programme should be implemented to allow the reeds to recover fully before being harvested again.
Page 1 /113457
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.