The encroachment of woody species into grassland and savanna ecosystems has been well document since the early 1800s. Within the parkland ecoregion of western Canada, trembling aspen (Populus tremuloides Michx.) has been one of the key tree species increasing in dominance. Aspen encroachment is best explained not by single mechanism, but rather by a number of interacting ecological factors. In this study I examined the ecological consequences of the clonal biology in aspen as a means to explain persistence and observed tree-grass ratios within grassland savannas of western Canada. Results suggest that aspen stands cycle between a “stable” phase characterized by a dense mature canopy, and an “unstable” phase characterized by canopy breakup and increased regeneration from root suckers. It is during this unstable phase that clonal encroachment is likely to occur. Within these mature stands, different-aged ramets promote persistence by maximizing developmental variation. Such a mechanism overcomes the functional phenotypic uniformity of ramets within a single age-structured stand. Results from my study indicate that physiological integration is beneficial to the growth and survivorship of regenerating and encroaching aspen ramets. My results also suggest that the benefits of physiological integration are greatest in more stressful environments, and in recently established post-fire ramets. Finally, the consequences of variation in adaptive ecological relevant traits among individuals was examined by determining differences in vigor among aspen clones in relation to the production of secondary compounds (phenolic glycosides). My results demonstrate a high degree of variation in leaf phenolic glycosides production among clones. A significant amount of this variation was accounted for by differences in clone vigor (within population: individual susceptibility hypothesis), with a smaller amount related to environmental differences (among populations). In all instances, vigorous clones were significantly higher in levels of phenolic glycosides compared with dieback clones, suggesting that some individuals may be predisposed to undergo density-independent mortality. This has important ecological implications, because it implies that one of the key mechanisms regulating population dynamics, community interactions and biodiversity may be related to intrinsic adaptive differences in susceptibility among individuals.

Land degradation is a process that causes the reduction in resource potential of natural rangelands and occurs widespread throughout southern Africa. This process is mainly characterized by the loss in vegetation cover, which leads to the occurrence of bare and denuded patches, increased soil erosion, changes in species composition as well as bush encroachment by indigenous and alien invasive plant species in savannah areas. Degradation of rangelands has drastically extended at an alarming rate during the last few decades with the main causes being overstocking, extended periods of drought, global climate change, overgrazing and general mismanagement of the land. Many researchers, however, feel that rangeland degradation is mainly caused by a combination of changes in land use practices and climate variability. Land users have, however, been applying a variety of technologies over the years in order to restore affected rangelands and mitigate the effect of degradation. These technologies include passive and active intervention methods, aimed at restoring bare and denuded areas and controlling indigenous bush and alien plant species encroachment. Bush control can be carried out by applying different technologies, involving chemical, mechanical, manual or biological control. The focal point of this study is on bush encroachment, the factors causing the problem, the possible ways of controlling this phenomenon and lastly the incorporation of such information into a user-friendly Decision Support System (DSS). The Decision Support System comprises of two databases as well as a related expert system. Bush encroachment is a matter of great concern in most southern African countries. This study therefore mainly included data from Namibia and to a lesser extent, South Africa, as the main study areas, seeing that this form of degradation greatly influences the biodiversity of rangelands in both these countries. The Namibia Agricultural Union (NLU) identified the need for the development of a user-friendly Decision Support System, in which case studies concerning the different bush control technologies could be stored in a database. Restoration technologies, regarding the occurrence of bare and denuded areas, that have been applied by the land users over a period of time and in a specific environment in the past, have been captured in a computerized database and expert system, serving as a Decision Support System (DSS) and user-friendly consulting tool in a similar study, carried out by Mr. Van der Merwe (1997). This DSS was based on CBR (Case Based Reasoning) methodologies by which a number of case studies, that have previously been stored in the database, can be searched by means of an expert system approach to advise the land user concerning the most appropriate solution (action) to similar degradation problems. The DSS developed by Mr. Van der Merwe was never published or made accessible to the land user in a format that could be consulted by either CD-ROM or the internet. Seeing that the NLU identified the need for a similar DSS containing bush control technologies, it was decided to incorporate both these databases into a single DSS, concerning bush control as well as the restoration of bare and denuded patches. The newly converted DSS is currently known as EcoRestore and consists on two databases: Grass Expert, which focuses on technologies to reclaim degraded rangelands, and Bush Expert, which is more focused on the control of bush encroachment and combating of alien invasives. As mentioned, this study focussed on the development of the Bush Expert database and will therefore only include results, discussions and conclusions of these case studies. The case studies in the Bush Expert database consist of results obtained by means of a questionnaire completed by the land user, in collaboration with the agricultural extension officer, as well as a quantitative vegetation assessment, to determine the success rate of the applied technology. The Bush Expert questionnaire, comprises of questions concerning personal information of the land user (e.g. location of the farm), the situation on the farm before bush control was applied (e.g. information on the environmental factors, such as density of problem trees), as well as the type of control technology applied and the situation of the rangeland after control (e.g. establishment of the herbaceous species). The quantitative vegetation assessments involved the sampling of the woody and herbaceous components in the area where a specific control technology was applied. The density and height classes of the woody component were determined by means of the belt-transect method. By using the descending-point method, the herbaceous component was surveyed to determine the abundance/frequency of the annual and perennial grass species. In order to increase the success of any restoration project, it is important to take the existing indigenous knowledge of local land users, concerning the problem of degradation and mitigation thereof, into consideration. By doing so, the local people and communities have greater control and responsibility over their resources and are able to command a greater range and level of resourcefulness. Taking indigenous knowledge into consideration finally enables the local land users to actively participate in and influence higher-level decision-making processes by which they are affected. A total of 175 case studies in Namibia and nine case studies in South Africa were surveyed. The Namibian case studies were surveyed in the central and northern arid and semi-arid regions, and South African case studies in a limited location within the Limpopo Province. Only 100 of the Namibian case studies have thus far been incorporated into the Bush Expert database. Multivariate data analyses techniques, analysis of variance and correlation analyses were used to analyse the data obtained from the questionnaires and quantitative vegetation surveys. Results were represented in the form of histogrammes, tables and multivariate analysis ordinations. From the results obtained for the Bush Expert database, it was clear that chemical control technologies were most often applied in Namibian and South African case studies (61%). The herbicides most commonly applied as chemical control technology in Namibia included Grazer (20%) and Savana (15%), whilst in South Africa these included Access (33.3%) and Tordon Super (33.3%). Herbicides were mostly applied by means of aerial application (46%) methods in Namibia and as cut-stump treatment (55.5%) by means of knapsack spraying or with a brush in South Africa. The dominant woody species causing bush encroachment problems in Namibia were found to be Acacia mellifera, Acacia reficiens and Dichrostachys cinerea, whereas in South Africa these species included Dichrostachys cinerea, Acacia erubescens and Acacia karroo. The wood of the controlled problem species (dead woody material) is mostly not utilized after control, but rather left on the land to disintegrate and thus contribute to the organic material content in the soil. Dead branches are also used for brush packing, which forms and ideal micro-climate for the germination and establishment of grass seeds, which serves as an erosion control medium and protects grass seedlings against grazing impacts. Some land users do however produce charcoal from certain controlled woody species, in order to recover some of the input costs of bush control. The majority of the case study sites (68%) in Namibia occurred within the 300-450 mm short- and long-term rainfall zones and in South Africa the majority of case study sites occurred within the short-term rainfall zone of 550-600 mm (66.6%) and 400- 500 mm long-term rainfall zone (55.5%). Case studies where chemical and manual bush control technologies were applied indicated the highest success rates after control (81.7% and 75.2% respectively). Success rate as an entity was greatly influenced by the type of control technology applied, the density of the problem woody species after bush control as well as environmental variables such as rainfall and soil clay percentage. No definite trend could be determined concerning the application of a specific bush control technology and a certain problem species. Land users tend to apply a chosen control technology, according to the resources available, such as labour, mechanical implements and finances. The only positive correlation between control technologies and the type of problem species could be found regarding Dichrostachys cinerea. This species was mainly chemically controlled by means of the application of certain herbicides. The most important lesson to be learnt from the surveys completed in the two countries is that it is an absolute necessity to apply a proper after-care programme as a management practice following the initial control of problem woody species. The implementation of after-care determines the final success rate of any applied bush control technology as a restoration practice within a rangeland. Only 11% of the case studies surveyed for Namibia and South Africa indicated the implementation of an after-care programme, which usually involved biological control (e.g. browsing by boer goats or the use of controlled or accidental natural veld fires). The EcoRestore Decision Support System is currently available as an online webversion (www.puk.ac.za/EcoRestore), as well as a CD-ROM version. The CD-ROM version is available in a package containing the CD and user's manual. An example of the package is included in this dissertation. In consulting the databases through question-and-answer procedures, the best action will be proposed to the land user for future rangeland restoration, either the reclamation of denuded areas or the control of bush encroachment. Since the case studies are based on past and existing experiences and research, the land user will have an indication of the expected outcome, should the same advised technology be applied. The EcoRestore DSS does not only offer a consulting tool for extension workers and technicians, but also creates networking and participation between land users and researchers, both locally and between neighbouring countries. The DSS is linked to other national and international websites and databases, to offer users a wider range of information and technologies with regard to agricultural and conservation practices. Better awareness is created amongst land users concerning the problem of rangeland degradation, which might encourage closer monitoring of the degradation and mitigation processes. The EcoRestore DSS was developed in such a way for it to be as user-friendly as possible, in order to reach as many parties involved in current or future restoration programmes. This study involved the development of the first version of the DSS (Version 1.0) and is thus only the prototype system. It is proposed that the Bush Expert database of the EcoRestore DSS, will be expanded in future and additional bush control case studies from other southern African countries will be included. The addition of such case studies will ultimately increase the effectivity of this DSS. / Thesis (M.Sc. (Botany))--North-West University, Potchefstroom Campus, 2004.

The encroachment of woody species into grassland and savanna ecosystems has been well document since the early 1800s. Within the parkland ecoregion of western Canada, trembling aspen (Populus tremuloides Michx.) has been one of the key tree species increasing in dominance. Aspen encroachment is best explained not by single mechanism, but rather by a number of interacting ecological factors. In this study I examined the ecological consequences of the clonal biology in aspen as a means to explain persistence and observed tree-grass ratios within grassland savannas of western Canada. Results suggest that aspen stands cycle between a “stable” phase characterized by a dense mature canopy, and an “unstable” phase characterized by canopy breakup and increased regeneration from root suckers. It is during this unstable phase that clonal encroachment is likely to occur. Within these mature stands, different-aged ramets promote persistence by maximizing developmental variation. Such a mechanism overcomes the functional phenotypic uniformity of ramets within a single age-structured stand. Results from my study indicate that physiological integration is beneficial to the growth and survivorship of regenerating and encroaching aspen ramets. My results also suggest that the benefits of physiological integration are greatest in more stressful environments, and in recently established post-fire ramets. Finally, the consequences of variation in adaptive ecological relevant traits among individuals was examined by determining differences in vigor among aspen clones in relation to the production of secondary compounds (phenolic glycosides). My results demonstrate a high degree of variation in leaf phenolic glycosides production among clones. A significant amount of this variation was accounted for by differences in clone vigor (within population: individual susceptibility hypothesis), with a smaller amount related to environmental differences (among populations). In all instances, vigorous clones were significantly higher in levels of phenolic glycosides compared with dieback clones, suggesting that some individuals may be predisposed to undergo density-independent mortality. This has important ecological implications, because it implies that one of the key mechanisms regulating population dynamics, community interactions and biodiversity may be related to intrinsic adaptive differences in susceptibility among individuals.

Bush encroachment is a major problem for the savannas supporting livestock in the Eastern Cape. Farmers employ chemical poisoning and mechanical clearing of woody vegetation to improve grass production. This thesis addressed the following questions. 1. Does soil fertility and hence, herbaceous production and/or quality increase beneath or between former bushclumps following woody clearing or poisoning? 2. Are chemical or mechanical control methods effective for all woody species? 3. Does bush density and height decline with increasing competition from the herbaceous layer? 4. Can fire and goats retard or revert woody re-establishment, thereby keeping these savannas open? A trial for assessing different methods of controlling bush was conducted near Kei Road. Initial treatments included chemical poisoning, mechanical clearing and a control, each replicated eight times in 0.36 hectare plots. Follow-up treatments were control, fire, goats, and the combination of fire and goats each replicated twice per primary treatment. Two additional mechanically cleared plots were oversown with Chloris gayana seeds. Herbaceous production, species composition, foliage quality and soil fertility, and mortality, recruitment, height increase and density of woody individuals were monitored for five seasons. Mechanical clearing of the woody vegetation increased soil fertility, except total nitrogen, and that explained the dramatic response in grass production that endured for the first four seasons since clearing. The periphery and ex-bushclump zones were characterised by increased colonization of Panicum maximum while there were no changes in frequencies of other key herbaceous species in all vegetation zones. Acacia karroo and woody "weeds" (Solanum incanum, Berkheya bipinnatifida) established from seed while all other woody species recruited mainly from coppicing. Seedling recruitment and resprouting resulted in high densities of woody stems and individuals by the second season after clearing when compared with the pre-clearing levels. Oversowing cleared areas with pasture grasses did not only increase grass production but also reduced the density of coppicing woody plants and "weeds". Chemical treatments mirrored the controls in terms of grass production, except during a very wet season, and species composition. Although encroaching woody species (e.g. Scutia myrtina, Maytenus heterophylla and Trimeria trinervus) were susceptible to poisoning, woody plant density was not reduced. Multi-stemmed woody individuals were resistant to poisoning. Fire and goats kept most coppicing woody plants short, less than half a metre, after three seasons of browsing and also improved grass production in the dense bushclumps suggesting that these clumps were being opened up. However, high browsing pressure forced goats to graze more hence this effect was masked. This study indicates that chemical and mechanical control of bush are economically unsustainable for beef and mutton production, at least in the medium term. Fire and goats are appropriate as a follow-up strategy for retarding woody regrowth, keeping bushclumps open, improving grass production and economic viability of mechanical clearing. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 115-120).

Thesis (doctoral)--Frei Universität Berlin, 2005. / "September 2005"--P. [2] of cover. Added thesis t.p. Includes bibliographical references (p. 93-99). Also available via the World Wide Web.

<p> </p><p>This study is an analysis of the traffic situation for pedestrians and bicyclist, unprotected road users, in Accra’s Central Business District. A Swedish method, Calm streets, is used to identify conflicts in the mixed traffic situation. The findings reveal a large amount of conflicts between unprotected road users and motor vehicles. These conflicts cause congestions which have negative implications on the environment, health and economy.</p><p>In addition an assessment of the quality of and access to pedestrian and bicycle facilities were conducted. This assessment indicates that the quality and access to the facilities are in general low, especially for the disabled, elderly and children. A larger Traffic Network Analysis and a Cost Benefit Analysis are needed to address these problems for stakeholders and decision makers.</p><p> </p>

Several reports of widespread establishment of mesophytic vegetation within oak-hickory upland forests have been documented throughout the Central Hardwoods Region. Previous studies suggest deviations from historic disturbance regimes may be a primary driver of vegetation change, necessitating the use of Fire Regime Condition Class (FRCC) guidelines to measure changes in forest structure. Current parameters of forest structure and fuel loading were assessed within mature oak-hickory uplands throughout the ecological subsections of the Shawnee National Forest, including the Greater Shawnee Hills, Lesser Shawnee Hills, Cretaceous Hills, and the Illinois Ozarks. Present species importance values and forest structure were compared with reference conditions developed from General Land Office records(Fralish et al. 2002). Current uplands contained an average 214.72 ± 16.52 SE trees/ac and 103.37 ± 2.16 SE ft2 BA/ac, while reference stands harbored less than 90 trees/ac with a range of 16 and 120 ft2 BA/ac. Due to the high levels of fragmentation and a lack of large contiguous upland stands within the Shawnee National Forest, stand level criteria for FRCC values were developed as opposed to landscape level FRCC values which are commonly used. FRCC values determined during initial surveys were compared with plot level ratios of forest structure parameters regarding oaks:mesophytes and xerophytes:mesophytes, yielding clear relationships between species composition and FRCC values. Fuel loading (tons/ac) was assessed as a determinant of FRCC values, however a significant relationship between FRCC values and fuel loading was not discovered. Since widespread deviations from the historic fire regime have taken place since the early 20th century, Fire Regime Condition Class values were found to fall into the FRCC 2 and 3 categories without any stands representing FRCC 1. This determination requires future management practices to follow Fire Regime Condition Class guidelines. The study proved that mesophytic species have become established within all canopy strata, with a strong probability of gaining future dominance without active forest management. Although it is clear that forest structure has deviated from reference conditions, a strong oak-hickory overstory component found throughout the study area provides a potential resource to sustain future oak-hickory upland ecosystems.

As disturbance frequencies, intensities, and types have changed and continue to change in response to changing climate and land-use patterns, coastal communities undergo shifts in both species composition and dominant vegetation type. Over the past 100 years, fire suppression throughout the Northern Gulf of Mexico coast has resulted in shifts towards woody species dominance at the expense of marsh cover. Over the next 100 years, sea levels will rise and tropical storm activity is projected to increase; resultant changes in salinity could reduce cover of salt-intolerant fresh marsh species. Together, the effects of fire suppression upslope and rising salinities downslope could "squeeze" fresh marsh species, reducing cover and potentially threatening persistence. To mitigate the effects of fire suppression, the use of prescribed fire as a management tool to mimic historic conditions is becoming increasingly widespread and will likely gain further popularity during the 21st century. Ecological shifts that will result from changing disturbance regimes are unknown. It was hypothesized that two recent hurricanes, Ivan and Katrina in 2004 and 2005, respectively, and a prescribed fire, in 2010, differentially affected species along the estuarine gradient and drove overall shifts away from woody dominance. Overall community composition did not change significantly in the intermediate and fresh marsh zones. However, significant changes occurred in the salt and brackish marshes and in the woody-dominated fresh marsh-scrub ecotone zones. Relative to 2004, woody species abundance decreased significantly in all zones in 2006, following Hurricanes Ivan and Katrina, and 2012, following the hurricanes and fire, though woody species regeneration in the marsh-scrub ecotone had begun to occur by 2012. It is hypothesized that interacting changes in fire and tropical storm regimes could release upslope areas from coastal squeezing.

abstract: ABSTRACT In this work, I provide two novel pieces of evidence in favor of the view that there is pragmatic encroachment on knowledge. First, I present an empirical case via the results of a series of recent experiments to show that folk-knowledge attributions may be sensitive to time constraints even when the latter are construed in a non-truth relevant manner. Along the way, I consider some comments made by Jonathan Schaffer (2006) as it pertains to interpreting time constraints-sensitivity in a manner that supports contextualism, before offering reasons to resist such a treatment. I proceed by applying interest relative invariantism to adjudicate a conflict in the epistemology of testimony namely, the positive reasons requirement a la, reductionism vs. non-reductionism. In particular, I highlight how whether an epistemic subject H needs positive non-testimonial reasons to be justified in accepting S's testimony that p, depends on what is at stake for H in believing that p and how much time H has in deliberating about p. / Dissertation/Thesis / M.A. Philosophy 2013