The sites of Elandsfontein (EFT) and Duinefontein (DFT) preserve important records of mid-Pleistocene human occupation along South Africa's southwestern coast. In addition to human fossils in the case of EFT, both sites have produced extensive collections of artefacts and faunal remains. Analyses of the latter have provided the broad environmental contexts for mid-Pleistocene human occupation along this coast. Recently, research into landscape use by mid-Pleistocene human populations at EFT and DFT has highlighted the need for more precise palaeoenvironmental data for the region. In response to this need, I analysed plant phytoliths extracted from sediments sampled at EFT and DFT. The results of this analysis are reported and interpreted in this thesis. To assist with the interpretation of the EFT and DFT phytolith assemblages, I established a modern phytolith reference collection. In addition, pre-existing phytolith collections were examined and literature was consulted. Phytoliths extracted from modern and mid-Pleistocene aged sediments sampled at different localities at EFT and DFT were identified and tallied to determine vegetation composition during the middle Pleistocene. Distinctions were made between "grassier" and "more woody" samples. Analyses of modern plant samples confirmed that grass species produced abundant phytoliths, whereas the majority of dicotyledons did not produce diagnostic morphotypes. Phytoliths belonging to grass species currently growing in the region were identified in the modern sediment samples, as were non-grass phytoliths that included those from woody dicotyledonous and monocotyledon plants. The majority of the mid-Pleistocene sediment samples from EFT produced varying proportions of grass, woody dicotyledon, monocotyledon, sedge and palm type phytoliths which are characteristic of cool-season growing landscapes. In comparison to EFT, the late mid- Pleistocene sediment samples from DFT contained fewer phytoliths. These results suggest that the conditions at DFT were either not conducive to the preservation of phytoliths or that the vegetation was sparse and/or did not produce abundant phytoliths. Where sufficient phytoliths were preserved, assemblages suggested landscapes similar to that of EFT. In summary, analyses suggest that during the middle to late Pleistocene, a heterogeneous vegetation community, consisting primarily of C₃ grasses, woody dicotyledons and other monocotyledonous plants existed along South Africa's southwest coast. Furthermore, results support the longterm presence of the winter rainfall zone in the region. This study demonstrates the potential of phytolith analysis as an important proxy in determining the composition of palaeo-vegetation communities in South Africa. Although there were limitations that necessitated the broad classification of phytolith groups, the study nevertheless provided more precise information, particularly about mid-Pleistocene vegetation structure, that was not previously available.

To meet the requirements of the Clean Water Act (1972), natural resource managers need to be able to detect biological degradation in wetland ecosystems. Biological indices are commonly used by managers to assess wetland biological condition. The accuracy and precision of wetland condition assessments are directly related to the performance of these indices, and biological index performance is thought to be related to how well an index controls for the effects of environmental attributes on biological assemblages. Many plant-based biological indices control for environmental and biological variation through the use of classification schemes that are based on geographic location and dominant vegetation type. However, the use of classification schemes tends to produce indices with limited applicability and may not adequately control for natural variation. The goal of my research was to use modeling techniques, as an alternative to classification, to account for biological variation associated with natural environmental gradients and to improve the performance of previously developed indices. I developed two types of model-based biological indices to quantify the biological condition of Ohio wetlands: a vegetation-based index of biological integrity (MVIBI) based on several attributes of wetland plant assemblages, and several indices of plant assemblage taxonomic completeness. I evaluated the accuracy and precision of the MVIBI relative to previously developed indices, and determined that the use of modeling techniques can significantly improve the performance of plant-based indices of biological integrity. Due to increases in accuracy and precision, use of the MVIBI should improve manager’s confidence in wetland biological condition assessments. The indices of taxonomic completeness exhibited poor performance relative to similar indices developed for other types of biological assemblages (i.e. aquatic insects, fish). I attribute poor index performance to my inability to accurately predict individual species occurrence, which is likely a result of plant communities being heavily structured by random disturbance events and biotic interactions that are difficult to account for. My results should help inform index developers of ways to potentially improve wetland condition assessment indices.

Excess nutrients entering aquatic systems cause negative effects downstream. Oxidation-reduction potential (Eh) is an inexpensive proxy which can be used to define the potential nutrient reducing capacity of a system, in particular denitrification. My thesis attempts to determine effects of hydrology and vegetation manipulations on Eh in an agricultural drainage ditch with weirs using continuous automated data loggers to monitor the system. Accuracy and precision of the continuous automated data loggers was confirmed through laboratory and field testing. Effects of hydrology and vegetation on Eh were quantified during testing from May-September 2012 in east-central Mississippi. Vegetation affected Eh (t=-1.75, P=0.08, df=9,754) whereas changes in hydrology also affected Eh (t=7.05, P<0.001, df=9,754). Modeling of these variables indicated the interaction of hydrology and vegetation was the most influential factor measured. Through management of hydrology and vegetation in ditches, Eh can be managed to create conditions conducive for denitrification.

Fertilizer N is one of the most costly inputs in corn (Zea mays L.) and cotton (Gossypium hirsutum L.) production and is a strong yield determining factor. Variable rate N fertilization has the potential to improve resource use efficiency, profitability, and help to minimize adverse environmental impacts. Vegetation indices (VIs) may be useful for in-season crop health monitoring to assist in fertilizer N management and yield prediction. This research determined the utility of aerial imagery in detecting corn and cotton response to varying N supply using five selected VIs. The VIs derived from aerial images, chlorophyll readings and tissue N for corn from V5 to V9 growth stages and cotton beginning the 1st week of flowering through to latelowering were used to relate to fertilizer N rates and plant N status and yield. The results showed that VIs derived from aerial imagery could be used to differentiate N supply and in-season grain yield of corn beginning at V5 to V6; however, models from later growth stages had greater r2 values than earlier growth stages. Single variable models that used VI, chlorophyll content, or plant N concentration as an independent variable were overall stronger than 2 variable Multiple Linear Regression models (MLRs). Three independent variables used in MLRs contained multicollinearity. For cotton, the use of VIs derived from aerial imagery to differentiate N supply may depend on environmental factors such as soil and weather. However, VIs may be useful for in-season lint yield prediction beginning the 1st week of flowering although later stages improved accuracy. The MLRs that were developed with 2 independent variables may be more suitable for in-season lint yield prediction than single independent variable models.

No description available.

River regulation cause unnatural water flow patterns which disrupt succession, survival and dispersal of riverine plant communities. Riparian zones in regulated rivers are generally more species poor and have a lower vegetation cover compared to free-flowing rivers. Tributary mouths within the impoundment however, are not only affected by processes in the main channel, but also affected by processes such as sediment dynamics and flooding regime from the tributary which may more reflect a natural regime and may therefore not be affected by hydropeaking to the same extent. Hence, tributary sites and the accompanied tributary mouths may represent hotspots for high diversity plant communities in regulated rivers. The riparian habitat is unique in its interaction with adjacent ecological systems and is therefore considered important for the riverine ecosystem’s ecological functioning. The aim of the study was to evaluate the significance of tributary sites and accompanied tributary mouths as a hotspot for diverse plant communities in regulated rivers. Additionally, geomorphological features were analyzed to access the impact of hydropeaking in sheltered and non-sheltered tributary sites. Data was acquired from sampling sites within the Umeå and Luleå rivers, representing both tributary mouths and non-tributary mouth reaches. Inventories included presence of riparian and aquatic vascular plant species, vegetation cover and soil composition. The results indicate a less extensive impact of hydropeaking in tributary mouths compared to non-tributary mouth reaches. The tributary mouths had a higher species richness, diversity and vegetation cover when compared to that of the non-tributary mouth reaches. This supports the concept of tributary mouths being hotspots for plant diversity. Moreover, the sheltered tributary mouths had a higher species richness than the non-sheltered tributary sites, suggesting tributary shelter as a contributing counter of hydropeaking effects.

Environmental evidence shows that 10,000 years ago North China was primarily a lush deciduous forest. Like many other regions of the planet, this landscape has been dramatically transformed by human activity, yet unusually this mostly occurred long ago under pre-industrial conditions. Fortunately China has a long recorded history of human activity. Complementary environmental evidence helps to extend this record into prehistory, for even prehistoric Chinese substantially altered their environment. The first half of this study examines historical and physical evidence in order to better explain how North China's forests disappeared. Only recently have there been regional scale activities focused on reversing this tragic trend. Despite many claims of successes in afforestation, there are serious shortcomings in the collection of government statistics and known limitations to area-based forest assessments, so it is difficult to say with much confidence what is happening with North China's forests today. Phenological measurements from space-based instruments have been effectively used to characterize vegetation trends. In the second half of this study, MODIS sensor observations for 2000-2009 are collected for five study sites and are used to characterize vegetation change over the past decade, independent of government statistics and area-based estimates. Forests provide tangible benefits to environmental and human well-being. Forest health and growth are critical to addressing global climate change. Much attention has been focused on China's efforts to combat deforestation. A better understanding of North China's forest trends — both past and present — may offer valuable lessons for our environmental future. / Master of Science

The complexity of urban areas within the mosaic of private and public vegetation has led communities to enact regulations to manage numerous benefits of urban vegetation. As urban populations continue to increase, regulations for governing vegetation becomes increasingly common. This study examined the variation in trends, structure, language, clauses, and provisions of vegetation ordinances within communities across the Southern United States. Qualitative content analysis using NVivo computer software was used for analyzing ordinances collected from Municode. Several discrepancies and similarities were explored in ordinance structure and content, along with problems such as lack of effective ordinance components (enforcement and severability provisions), unclear goals, unclear provisions, inadequate information, duplications, section contradictions, and misspellings. Findings will guide urban foresters, arborists, planners, and elected officials while developing new codes and suggest a need to draft better ordinances and revise problematic ones to increase positive impacts on the community green infrastructure.

No description available.

<p> An open Quercus-dominated vegetation association, known locally as the oak plains, was found at a number of locations in southern Ontario until disturbance by European settlers in the late 18th and early 19th centuries. Two contrasting theories have been suggested in the literature regarding the origin of the oak plains. One suggests they developed as the result of burning by pre-European natives, while the other considers them to be relics of a warmer, drier mid-Holocene climate. In this paper, the factors which led to the development of the oak plains are examined. The hypothesis that the oak plains resulted from native burning of the natural vegetation was tested by pollen analysis of a 5 m sediment core from Decoy Lake, a small kettle basin near Paris, Ontario located in an area mapped by early surveyors as oak plains. The Decoy Lake record was then compared to those of two nearby lakes supporting mesic forests. This palaeoecological analysis was supported by an investigation of physical factors controlling the historical distribution of the oak plains in a study area between Cambridge and Long Point on Lake Erie. </p> <p> The distribution of the oak plains and other vegetation associations in pre-settlement times, reconstructed from early survey records, correlated fairly well with the texture of soils and underlying Quaternary parent materials. Within the defined study area, the oak plains were restricted almost exclusively to well-drained soils overlying coarse-textured till and sandy outwash and deltaic deposits. Climatic factors and topography varied within the study area, but showed little correlation with the distribution of vegetation associations. <p> <p> The fossil pollen record at Decoy Lake indicates that a QuercusPinus- herb pollen assemblage, unique to southern Ontario, was found from 4000 yr BP until pre-settlement times. This suggests that the oak plains have existed in the area for at least 4000 years. The oak plains replaced an assemblage dominated by Pinus strobus. The warm, dry Hypsithermal appears to have allowed Pinus strobus to remain dominant on the well drained soils around Decoy Lake until after 5000 yr BP, 2000 to 3000 years longer than at other southern Ontario sites. The Picea zone (11,800 yr BP to 10,100 yr B P), Pin us banksiana/resinosa zone ( 10,100 yr BP to c. 9000 yr BP), and the replacement of Pinus banksiana/resinosa by Pinus strobus (c. 9000 yr BP) occurred contemporaneously with other records from southern Ontario. </p> <p> The hypothesis that anthropogenic factors resulted in the development of the oak plains was rejected since this association developed 2500 years before the onset of agricultural activity by natives in southern Ontario. Instead, it appears post-Hypsithermal increases in moisture, perhaps coupled with an amelioration of winter temperatures, led to the replacement of Pinus strobus by the oak plains in some areas of well-drained soils between 6300 yr BP and 4000 yr BP. The pollen record from Decoy Lake provides the first evidence from southern Ontario for substantial vegetation response to mid to late Holocene climatic change. </p> / Thesis / Master of Science (MSc)