OpenUCT :: Browsing by Author "Moll, EJ"

Browsing by Author "Moll, EJ"

Now showing 1 - 9 of 9

Open Access
Aspects of the structure and phenology of two fynbos communities
(1984) Le Maitre, D C; Moll, EJ
Data on the floristics, biomass, pattern, growth forms and regeneration modes of two tall, mid-dense, proteoid shrublands are analysed. The phenology of a number of species in different growth forms is examined in terms of current hypotheses about growth form related timing of shoot growth, and general patterns of periodicity in nutrient-poor mediterranean environments. Taxa typical of the fynbos flora are dominant in both communities, but the drier Cedarberg community has fewer species in these taxa and more annuals than the moister Kogelberg environment. These floristic changes are reflected also in the growth form spectra and the stratification of the communities. The biomass of the cedarberg community is higher at 1820 g/m2 against 1100 g/m2 for the Kogelberg community. This difference is discussed in terms of the greater effectiveness of the rainfall at the Cedarberg (664 mm/yr), than at the Kogelberg (1016 mm/yr), and the availability of soil nutrients. There are more sprouting plants, excluding annuals, in the flora of the Cedarberg site. This is in line with the prediction that, within limits, the drier the climate, the more reliable the investment in vegetative regrowth after fire. The similarity in community physiognomy is confirmed by the quantitative analyses which show that there are differences and also strong similarities between the communities. The overstorey Proteaceae grow from spring to mid-summer, as do the Restionaceae, but the other growth forms follow a variety of patterns, including opportunistic summer growth. The sequence of phenological events is partly related to morphological sequences in plant development and partly to resource partitioning. The current hypotheses concerning community structure and phenology in mediterranean environments cannot be refuted, but they do not account for the variations observed within and between growth forms and need to be critically examined.
Open Access
Conservation implications of the invasion of southern Africa by alien organisms
(1991) Macdonald, Ian Angus William; Siegfried, W R; Moll, EJ
Alien species known to be invading untransformed ecosystems in southern Africa, and, more particularly, those inside nature reserves, were identified. The extent and ecological impacts of these invasions were assessed. Their control within reserves was also evaluated. Research approaches used were; literature review (which included an international review), a detailed questionnaire survey of alien plant invasions in 307 reserves, rapid field surveys of 60 reserves, intensive case studies of four reserves (Cape of Good Hope Nature Reserve, Hluhluwe-Umfolozi Game Reserve, Kruger National Park, Pella Fynbos Research Site), international comparison with case-study reserves in other savanna and Mediterranean-type biomes, and field evaluation of control methods for alien plants in the two fynbos reserves. Ecological impacts of alien invasions throughout the subcontinent were determined from historical changes in vertebrate populations, including detailed studies of three native birds (Bostrychia hagedash, Lybius leucomelas, Ploceus velatus) expanding their ranges, partly in response to the spread of invasive alien trees. The results are presented in eight chapters, comprising 26 published (or submitted) papers, an introduction and a concluding summary. One chapter covers contributions to the theoretical understanding of invasion processes, including a prediction of their interaction with rapid global environmental change. The conclusion is reached that alien invasions pose a serious challenge to nature conservation in the region. Mostly this comes from alien woody plants but the importance of herbaceous plants has possibly been underestimated regionally. Introduced mammalian pathogens and predatory fishes have also had important effects. Alien invertebrates have been poorly studied (the ant lridomyrmex humilis poses a significant threat). Alien terrestrial vertebrates have generally had only localized effects. Alien plant invasions affect all biomes, with riparian ecosystems being regionally threatened. Mesic biomes and habitats are usually more invaded by alien plants than xeric equivalents. 281 alien vascular plant species were recorded invading vegetation within nature reserves (an average of 12 species per reserve) with an additional 200 species being possibly present but unrecorded (an average of 18 species per reserve). By 1984, the 54 plant taxa recorded invading reserves most frequently were estimated, on average, to be present in 30% of the 11cm x 11cm grid cells of the reserves they were invading. The average potential future extent of these invasions was estimated to be 51%. Control had, on average, been initiated for two plant species in each reserve and 18% of these operations had already resulted in complete eradication. Reported control costs were particularly high for the woody plants which pose a serious threat to the highly endemic flora of the fynbos biome, on average R48 284/reserve (R1,8/ha = US Dollar 1,2/ha) in 1983. These high costs were validated experimentally. A computerized optimization model, aimed at minimizing the costs of controlling the most intractable shrub invader of fynbos, Acacia saligna, was developed from the results of a field experiment at the Pella site. Practical field- scale control of these invasions was assessed to be feasible, using the results of repeated monitoring of permanent plots in the Cape of Good Hope Nature Reserve. Control strategies and regional priorities, based on the theoretical and practical insights gained from this study, are proposed. Even though the intensity of invasions is likely to increase in the foreseeable future, in part as a result of rapid man-induced changes in global climate, it is predicted that these invasions can be controlled if the correct approaches are adopted timeously. Failure to control them, will ensure that the extinction rate of native species will markedly increase and that ecosystem functioning will be altered significantly at a local scale and, conceivably also, at a regional scale.
Open Access
The development of a Geographic information system for environmental monitoring on the Cape Peninsula, and an assessment of the use of spot imagery for vegetation mapping
(1991) Webster, Michael S; Moll, EJ; Martin, C G C
This thesis concerns the establishment of a Geographic Information System for the Cape Peninsula and the use of SPOT satellite imagery to map land cover classes. The former is seen as a necessary tool to promote judicious conservation management decisions for the fragile "Fynbos" ecosystem, and the latter as a convenient means of acquiring up-to-date information concerning the environment, and to monitor change.
Open Access
Factors affecting the conservation of renosterveld by private landowners
(1988) McDowell, Clive Robert; Grindley, J R; Moll, EJ
West Coast Renosterveld, once prevalent on the south-western Cape lowlands of the floristically rich Cape Floral Kingdom, is now South Africa's scarcest vegetation type. Delimitation and measurement of the 55 "island-remnants", scattered amongst agricultural lands indicated that only 3% of the original vegetation remains. Measured soil quality, gradient and rainfall (critical agricultural criteria) were used to derive agricultural 'threat' indices (probability of agricultural clearance) for each remnant. The indices agreed well with observed trends in the recent clearance of remnants not deliberately conserved by landowners. This new approach has potential for determining which remaining natural sites most urgently need preservation. It was demonstrated that agro-technical innovation poses a long-term threat to even the low agricultural 'threat' rated renosterveld. Pasturage, invariably practised in renosterveld, was assessed by comparing "grazed" with "ungrazed" plant species covers. Within the test site, heavy grazing increased Asteraceae and Iridaceae, decreased Poaceae and Rutaceae, and eradicated Proteaceae. These changes may reflect local trends associated with modern grazing regimes. Total plant diversity and cover were not found to be affected. Therefore, controlled pasturage reflects a relatively minor threat to the extinction of floristic elements. Private landowners are found to control the destiny of 80% of West Coast Renosterveld. The conservation attitudes and behaviour of a random sample of these critical decision-makers were analysed. A new approach was devised to assess 32 subjective, bias-prone "intangible" variables. This required additional assessors to provide independent, non-parametric ratings of the author's tape-recorded interviews with the landowners. Results were pooled and "inter-assessor" measurement error was estimated. Altogether 52 variables, including a further 20 "tangible" variables, were rated under categories: 'Demographic', 'Psycho-Social, 'Land Use' and 'Conservation Strategy'. A correlation matrix portrays inter-relationships between variables and their correlations with landowner "Conservation Behaviour". Landowners' knowledge of biota, rapport with interviewer, education, affluence, bilingualism, and parents' education all correlated positively with conservation. Linear equation models were derived (using Best Subsets Statistical Programme) to predict 'Conservation Behaviour'. Although most conservation related variables are "fixed" (e.g. it is not possible to change parents' education), the understanding of these background factors (not previously applied to conservation of natural ecosystems) enables choice of the most appropriate strategy to persuade landowners to conserve. Different groupings of landowners having similar ratings of key variables have similar needs and constraints to be considered vis a vis improving their "Conservation Behaviour".
Open Access
Feeding ecology and habitat of the Protea seedeater Serinus leucopterus
(1976) Milewski, Antoni Vincent; Siegfried, W R; Moll, EJ
The present study involved a description of the habitat and the feeding niche (sensu Whittaker et. al. 1973) of the protea seedeater, and an assessment of factors contributing to the ecological segregation between the protea seedeater and its congeners in the south-west Cape biotic zone. No similar study of an African bird has been attempted.
Open Access
Studies on Australian acacias in the South Western Cape, South Africa
(1980) Milton, Suzanne Jane; Hall, A V; Moll, EJ
The thesis comprises six papers dealing with aspects of the ecology of the exotic Acacias which are considered to be weeds in the South Western Cape. Topics covered are the origins and reasons for success of the Australian Acacias in the Cape, their phenology, reproductive biology, shade tolerance, litterfall and biomass. The implications of these findings for management are discussed in the general conclusion, and the raw data is tabulated in four appendices. The work is illustrated with 37 figures.
Open Access
Timber growth and succession in the mixed evergreen forests of the southern Cape
(1994) Van Daalen, Johan Cornelis; Moll, EJ; Bond, William J
A deterministic distance-independent individual tree model, called OUTENIQUA, was developed for a 44ha southern Cape mixed evergreen forest compartment where the DBH's of all trees have been measured over a 15 year period. The central growth equation from another model for mixed forest was used and parameters adjusted to cater for the southern Cape forests. The developed model was then used to highlight research needs. Some of these research questions were addressed in this study.
Open Access
Vegetation gradients in Southern Cape mountains
(1981) Bond, William J; Moll, EJ
Southern Cape Mountain fynbos has been little studied in the past so that management and planners have had to draw heavily on Western Cape experience. This study arose from the need to define local vegetation patterns and their interdependence with animal life, climate and soil as a necessary prerequisite to vegetation mapping and Fynbos is part of the diverse and complex Cape Floral Kingdom. Field taxonomy in fynbos is often problematic for trained botanists and is an overwhelming obstacle for mapping and monitoring of vegetation by untrained observers. Even the most unsophisticated observer, however, can recognize consistent variation in non-floristic characters such as vegetation height, density and the relative abundance of Proteaceae, small leaved shrubs and graminoid plants. A major aim of the study was thus to test the feasibility of deriving a non-floristic vegetation classification using easily learnt characters which had predictive value and was independent of the complication of high species turnover from one area to the next.
Open Access
The vegetation of Swartboschkloof, Jonkershoek, Cape Province, South Africa
(1983) McDonald, David Jury; Moll, EJ
Swartboschkloof forms part of the Jonkershoek catchment complex at the headwaters of the Eerste River, Cape Province, South Africa. It has been selected for multi-disciplinary studies of Mountain Fynbos vegetation. The study area has a mainly equatorial aspect (north-facing) and receives an average of 1600 mm rain per annum, mainly in winter. Temperatures do not reach extremes. Winds blow mainly from the south-east, increasing in strength in summer. North-west winds blow intermittently in winter, bringing rain. The altitude of Swartboschkloof ranges between 285 m and 1200 m and the soils are derived from quartzitic Table Mountain Sandstone and porphyritic Cape Granite. Using the Braun-Blanquet phytosociological method, vegetation and environmental data were collected at 201 relevés throughout the study area; 101 of these relev~s are correlated with a survey of soils of part of the same area. Sixteen fynbos communities, grouped into three groups and five forest communities, grouped into two groups, have been identified. The data of a previous study by Werger, Kruger and Taylor (1972) have been interpreted in the context of this study. A map of the plant communities has been drawn and an attempt has been made to explain the distribution of the communities in terms of environmental factors. There is a strong link between the vegetation and soil geology but application of a method such as principal components analysis would be necessary to explain the relationship clearly.

Browsing by Author "Moll, EJ"

Results Per Page

Sort Options