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Complementarity between two metrics which use invertebrates to assess riparian conditions of rivers.Smith, Jenny. January 2005 (has links)
Conservation of streams involves an understanding of their physical , chemical and
biological entities. SASS5 is a biomonitoring method developed to monitor the habitat
quality of a water body. It is based on differential scores attributed to various
macroinvertebrate families with varying degrees of sensitivity to anthropogenic impact.
This method , however, does not assess impacts on particular species.
Odonata are good candidates for study at the species level as they are well researched and
males are easily identified . As adults, they are known to be sensitive indicators of both
riparian and river conditions. Yet Odonata cannot be an umbrella taxon for all other taxa .
Therefore, the main aim of this study is to determine the complementarity of the two
metrics (Odonata assemblages and SASS5), establishing whether Odonata assemblages
offer additional information on, or insight into, riverine habitat quality as portrayed by
SASS5.
To accomplish this, certain objectives were addressed . 1) The variation of SASS5 scores
and 2) Odonata assemblages between river systems, structural habitat types (open or
closed canopies) and compositional habitat types (indigenous or alien vegetation). 3)
Whether SASS5 scores vary to the same extent, and, 4) on the same spatial scale (river
system and point localities) as Odonata abundance and species richness .
The relationship between these two metrics was determined along three rivers in the
Pietermaritzburg basin. Sampling units (SUs) with extremes in vegetation structure
(sunlight and shaded SUs) and vegetation composition (alien or indigenous) were
selected. Using this range of environmental conditions placed environmental extremes
on the macroinvertebrate populations at point localities and having three different river
systems added the dimension of variation over a broader scale, thus stretching the two
metrics to investigate whether both responded similarly or in different ways.
Results indicated that both metrics provide a similar portrait of overall river conditions.
At the smaller spatial scale, the Odonata assemblage, unlike SASS, was highly sensitive
to the riparian vegetation. Odonata species were less sensitive to vegetation composition
but differentially sensitive to vegetation structure. However, landscape context is also
important, with point localities being affected by the neighboring dominant habitat type.
Larval Odonata alone did not provide this information. Overall, aquatic
macroinvertebrates and adult Odonata provide a highly complementary pair of metrics
that together provide large spatial scale (river system) and small spatial scale (point
localities) information on the level of impact of stressors such as riparian invasive alien
trees. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
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A framework for effective urban stream corridor management : a case study of Pietermaritzburg. Component A.De Lange, Marthinus Arnoldus. January 2003 (has links)
Not only does urbanisation have a negative impact on the establishment of natural open
space areas but also has serious implications for urban stream corridors (USCs), the focus of
this study. For the purpose of this study USCs are defined as the aquatic, the riparian and the
terrestrial zone. The principle objective of this study is to develop a set of policies, based on
international and local experiences (Pietermaritzburg Metropolitan Open Space System) to
guide municipalities in implementing effective USC management practices.
The literature review lead to the identification of both the value of USCs and the threats
thereto. The value of USCs includes habitat and biodiversity, purification, amenity, cultural,
recreational and eductional valueas well as flood attenuation value. Conversely, threats to
USCs include the impacts of urbanisation on stream hydrology, erosion, decline in water
quality, loss of natural open space (NOS), alien infestation, littering and unnatural fence
barriers. Urban stream corridor management is subject to specific legislation, municipal
capacity and importantly, public involvement, which were also evaluated.
This process lee;td to the establishment of a conceptual framework containing the critical
considerations associated with USC management such as the value of USCs for nature and
man, the need for public involvement, effective implementation structures supported by
implementation policies and the integration of use management in urban planning. Key to
the success of USC management is public involvement.
As a consequence, the methodology included a survey to be undertaken with 40 urban
riparian households along two streams in Pietermaritzburg to establish their opinion regarding
natural open spaces (NOSs) and USC management. A reconnaissance survey of two
streams was undertaken to inform the questionnaire and later debate on the issue. The
results from this exercise together with the findings of the interviews with stakeholders in the
USC management process will form the basis for the establishment of an USC management
policy, which will be contained in a separate report (Component B). / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.
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The impacts of woody invasive alien plants on stream hydrogeomorphology in small headwater streams of KwaZulu-Natal.Bruton, Simon N. January 2010 (has links)
South Africa has a long history of problems with invasive alien species. In an assessment of alien invading plants and water resources in South Africa Versveld et al. (1998) estimated that Invasive Alien Plants (IAPs) in South Africa covered an area equivalent to the size of KwaZulu-Natal. However this area of invasion was primarily concentrated along the river courses of South Africa as alien invasions are arguably a riparian problem (Versveld et al., 1998). In a 1998 assessment of the distribution of IAPs in South Africa Versveld et al. (1998) found a total invasion extent of 8% for South Africa (including Lesotho), while KwaZulu-Natal had a higher total extent of invasion at 9.75%. However the authors noted the limitations of the IAP mapping assessment and stated that from personal observations and observers’ comments the area invaded by IAPs may be as much as 2-3 times greater than the 9.75% value obtained for KwaZulu-Natal. South Africa’s most widespread invasive alien tree (Dye and Jarmain, 2004), Acacia mearnsii (black wattle), is ubiquitous throughout KwaZulu-Natal, and invades most severely where water is plentiful, such as along watercourses and road verges. However following dispersal along rivers, A. mearnsii spreads into adjacent terrestrial habitats (Richardson and Kluge, 2008) including indigenous grassland and forest. A. mearnsii was introduced to South Africa in the middle 19th century to provide tanbark, woodchips, construction poles and firewood, and its introduction spread rapidly across KwaZulu-Natal through farmers and foresters (Henderson, 2001; WESSA, 2008). River and riparian zone rehabilitation is becoming accepted as having an essential role to play in the long term solution of water resource quality and supply problems and environmental health as a whole. As a result the impact of IAP invasions on water resources, ecological habitats and the delivery of ecosystem goods and services has undergone much scientific investigation (van Wilgen et al., 2008). Numerous studies have shown that, under most circumstances, removal of IAPs results in a general increase in streamflow and returns a stream to a more natural seasonal flow regime. However, scientific studies on the influences of woody IAPs on the hydrogeomorphology of riparian areas, and the resultant effects on stream hydrology and ecology, have undergone little scientific investigation in the South African context. Hydrogeomorphology studies the linkages of surface and subsurface water, and hydrological processes with landforms and geomorphic processes in temporal and spatial dimensions. As a result the discipline is well applied to the study of the interaction of, and interdisciplinary impacts of IAPs on riparian areas. Macdonald (2004:22) stated that there is a need to “investigate the interaction of IAPs with other aspects of water quality, for example soil erosion rates, including river channel and bank erosion.” In the early 1990s, after a study assessing the potential impact of IAPs on the geomorphology of river channels in South Africa, Rowntree (1991) stressed that further research on the influence of IAPs on stream geomorphology is required to guide truly effective riparian zone management. Since this study, little scientific work has been undertaken on this topic in the South African context. The literature review portion of this dissertation reviews the findings of various researchers as to how IAPs physically influence riparian habitats, specifically with reference to the role of IAPs in degrading riparian and streambank landscapes to an extent that streambank stability and stream channel form is adversely affected. This topic is introduced by illustrating the many functions that riparian zones can perform and some of the possible consequences of a loss of riparian habitat integrity. Worldwide awareness of the functions and values of riparian systems has led many countries to perform inventories of threatened and valuable riparian areas. A database of stream habitat integrity is useful for environmental impact assessments, development planning and resource inventories. Thus a multitude of stream survey and aquatic health sampling techniques and methodologies have been developed, some of which could be applied to assessing the influence of IAPs on riparian zones. 1.1 Research Aims and Objectives This dissertation forms a research study based on field research centred around field methods and tools developed after a review of relevant literature. The key aims of this research study are to; · refine an international river habitat survey method for application within South Africa, and · develop a test case to implement the developed method in analysing the impacts of IAPs on stream hydrogeomorphology in small headwater streams of KwaZulu-Natal, South Africa. These aims are achieved through the following objectives; · investigate the current body of knowledge covering the impact of woody IAP invasions on streambank stability and channel form, · review available stream survey methods and develop a stream survey methodology which can be applied to investigate the relationships between woody IAP invasions and streambank stability and form within headwater streams of KwaZulu-Natal, · investigate the relationships illustrated by the data after applying the developed stream survey tools and fieldwork methodology, and · discuss any shortfalls of the developed tools and methods, and suggest future needs. The hypothesis of the study contends that, within the focus of this study, invasion of headwater streams by woody IAPs can result in; · increased channel incision and bank steepening, and · an increase in streambank instability. 1.2 Document Structure Chapters 2 to 4 form a review of current literature to establish a base of understanding of the implications, processes and components involved in the invasion of riparian zones by Invasive Alien Plants. In Chapter 5 the approaches to stream surveying are assessed and selected methods of stream survey seen as applicable to this study are reviewed. Based on these findings, a method of stream survey for application in this study is developed and described in Chapter 6 following a description of the fieldwork sites and methodology. Chapter 7 provides an extensive analysis and exploration of the results of the various components of the fieldwork, which are then discussed in Chapter 8. Chapter 9 outlines final conclusions, analysis of the applicability of the findings, and suggestions with regards to future research needs. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.
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