Fire is generally used as a management tool for different vegetation types such as savannas and grasslands in southern Africa. In the False Thornveld of the Eastern Cape, fire is commonly used to control bush encroachment and to increase grass production, as grasses are important source of forage for domestic livestock. At the University of Fort Hare farm in the Eastern Cape, a trial was set up in 1980 to investigate the effect of burning frequency on vegetation. There are six treatments replicated twice in a completely randomized design on a 100 m x 50 m plots. The treatments comprise no burn, annual, biennial, triennial, quadrennial and sexennial burns. From this trial a study was conducted to investigate long term effect of burning frequency on species and soil seed bank diversity. Two 100 m line transects located 25 m apart were laid within each plot, and the herbaceous and woody species were identified and recorded along the line transects. Relative abundances (%) for each species were calculated for each treatment. Soil samples were collected at an interval of 13.3 m along the line transects. The samples were placed in paper bags and kept for use in a germination experiment. The seedling emergence germination method was used in the glasshouse to determine emerging seedlings, pots were filled with Hygromix growth medium and the soils from the fire trials 12 X 6 = 72 were spread on top. Soil from the control plots were also pre-treated with heat, smoke and the combination of heat and smoke. The experiment started in January 2010 and was terminated in April 2010. The Shannon-Weaver Diversity Index was used to determine species diversity for standing vegetation and germinated seedlings. Data were tested for normality and species abundances were transformed. Analysis of Variance (ANOVA) was applied to test treatment effects on geminated seedlings, species abundance and diversity at α = 0.05 significance level. Significant differences between treatment means were determined by post v hoc tests using Fischer‟s Least Significant Difference test at α = 0.05. The Pearson Moment Correlation test was used to test the relationship between vegetation and soil seed banks. Treatments had significant effects on herbaceous, woody species abundance and diversity (P < 0.05), but there was no significant treatment effect on soil seed bank diversity and on pre-germination treatments (P > 0.05). The annual, biennial and triennial burns were dominated by Themeda triandra while the quadrennial, sexennial and the control treatments were dominated by Sporobolus fimbriatus and Melica decumbens. A. karroo dominated the woody component across all treatments, but it did not change in abundance. S. fimbriatus was the most abundant in the soil seed bank across all the treatments and also in all pre-germination treatments. Species diversity was high in standing vegetation in the quadrennial, sexennial and the control treatments. There was no significant correlation between the standing vegetation and soil seed bank diversities (P > 0.05). Based on these findings it is apparent that fire can change vegetation in an area to be dominated by fire tolerant or fire intolerant species. Fire frequency, heat and smoke affects soil seed banks to a lesser extent in the False Thornveld. For the management of the False Thornveld of the Eastern Cape, less frequent burning is recommended as it increases aboveground species diversity.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-09-19T12:29:54Z No. of bitstreams: 2 Dissertação - Giovanna Silva Bianchi - 2018.pdf: 1667419 bytes, checksum: 6af00ab2fce1eda6fda0f5a76970fde3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-09-19T13:02:47Z (GMT) No. of bitstreams: 2 Dissertação - Giovanna Silva Bianchi - 2018.pdf: 1667419 bytes, checksum: 6af00ab2fce1eda6fda0f5a76970fde3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-09-19T13:02:47Z (GMT). No. of bitstreams: 2 Dissertação - Giovanna Silva Bianchi - 2018.pdf: 1667419 bytes, checksum: 6af00ab2fce1eda6fda0f5a76970fde3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-04-03 / This study analyzes the process of commodification of the seed, which goes from a regenerative resource, surrounded by traditional knowledge and part of sustainable ecosystems, to the central commodity of agribusiness. This process involves the technological models of agriculture, the process of neoliberal globalization, reductionist science, and legal systems that legitimize only this kind of knowledge as valid. The core of this dissertation is analyzing whether the process of commodification of the seed generates risks to socioenvironmental and agrifood rights and, if so, whether it is possible to minimize them. In this sense, a hypothesis is verified that an agricultural modernization, using the commodified seed, is inserted in the world society and, therefore, produces risks for the biodiversity, the balanced environment, the adequate food, the food security and life of family farmers. Furthermore, the application of the precautionary principle, materialized in the implementation, as legal and development of databases, as a way of minimizing such risks is concluded. The present dissertation has as a theoretical framework the thought of Ulrich Beck, which discusses that the late modernization in which we live, in this work specifically focused on the agricultural field and the seed is situated in a world risk society whose risks represent the anticipations of potential catastrophes that lead to precautionary and preventive actions. The methodology employed is logical-deductive, keeping within itself the necessary cohesion and coherence with the fulcrum to the final objective: reflective answers and inquiries to deepen the study, thus seeking the contribution not only for the legal-academic community, but also a study that overflows to the existing agricultural practice in the country, because it still does not have a lot of specific doctrine on the subject. / Este estudo analisa o processo de mercantilização da semente, que passa de recurso regenerativo, envolto de saberes tradicionais e parte de ecossistemas sustentáveis, a mercadoria central do agronegócio. Esse processo envolve os modelos tecnológicos da agricultura, o processo de globalização neoliberal, a ciência reducionista e os sistemas de legais que legitimam apenas esse tipo de conhecimento como válido. O cerne desta dissertação cinge-se em analisar se o processo de mercantilização da semente gera riscos aos direitos socioambientais e agroalimentares e, caso positivo, se é possível minimizá-los. Nesse sentido, comprova-se a hipótese de que a modernização agrícola, com a utilização da semente mercantilizada, está inserida na sociedade de risco mundial e, por isso, produz riscos aos direitos à biodiversidade, ao meio ambiente equilibrado, à alimentação adequada, à segurança alimentar e à vida digna dos agricultores familiares. Ainda, conclui-se pela aplicação do princípio da precaução, materializado na implementação, regulamentação legal e desenvolvimento de bancos de sementes, como forma de minimização de tais riscos. A presente dissertação possui como marco teórico o pensamento de Ulrich Beck, que aborda que a modernização tardia em que vivemos, neste trabalho especificamente voltada ao campo agrícola e à semente, está situada em uma sociedade de risco mundial, cujos riscos representam antecipações de potenciais catástrofes que obrigam a tomada de ações precaucionistas e preventivas. A metodologia empregada é a lógico-dedutiva, guardando em si a necessária coesão e coerência com fulcro ao objetivo final: respostas e indagações reflexivas para o aprofundamento do estudo, pretendendo, assim, a contribuição não somente para a comunidade jurídico-acadêmica, mas também um estudo que transborde para a prática agrícola existente no país, porquanto ainda prescinde de farta doutrina específica sobre o tema.

Organised community seed banks (OCBSs) are one of the main tools to preserve crop diversity at a local level and therefore constitute an important driver for local resilience, as well as an important tool to move society towards sustainability. Agriculture is a fundamental leverage point for society: it fulfils a basic survival need as well as being one of the causes of humans’ unsustainable impact on the environment. It also holds the key to the preservation of biodiversity, which is increasingly important in the face of climate change and extreme weather conditions, and the reduction in use of chemical fertilisers and pesticides, which is necessary to move towards sustainability. Organised community seed banks have the potential to be a tool for this preservation of biodiversity, however, there is currently a lack of literature, resources and guidelines to position them as such. This research set out to identify the challenges that OCSBs face that could affect their success in contributing to a sustainable society, and the gaps between what management resources are available to them and their current management practices. With the aid of organised seed bank representatives and experts from around the world, the result was the design of a strategic approach to help OCSBs address their challenges and allow them to better contribute to the provision of food sovereignty, food security and socio-ecological sustainability.

Afin d’appréhender l’impact des dépôts d’azote atmosphérique sur les écosystèmes,nous nous sommes intéressés à un écosystème d’intérêt patrimonial : les prairies acides duViolion caninae. Au sein de ces prairies, les objectifs étaient de (i) quantifier les variationsfloristiques temporelles et spatiales le long du domaine atlantique français et de déterminer siles variables de dépôts d’azote et du climat expliquaient ces patrons, (ii) comprendre lesprocessus mis en jeu lors de l’enrichissement en azote au niveau de la végétation et du sol, et(iii) examiner les moyens potentiels de conservation et de restauration.L’étude temporelle et spatiale des prairies acides a permis de mettre en évidence deschangements de composition à l’échelle locale du type de communautés mais également àl’échelle nationale du domaine atlantique français. A l’échelle locale et nationale, ceschangements ont pu être reliés à des changements climatiques d’augmentation de latempérature annuelle moyenne et de diminution de la disponibilité en eau du sol. Toutefois àl’échelle locale, les plus forts changements de végétation ont été perçus pour les sites soumiségalement aux plus forts dépôts chroniques d’azote depuis les 25 dernières années. Ceschangements de composition se sont produits au détriment des espèces de petites tailles, tellesque des dicotylédones, alors que les Poacées généralistes se sont maintenues en dominant lecouvert végétal. Ces changements sont visibles dès 10-15 kg N ha-1 an-1, déterminé comme lacharge critique d’azote pour les prairies acides.L’approche expérimentale a permis de souligner les processus mis en jeu dans ceshabitats acides lors d’un apport d’azote. Notamment, l’enrichissement en azote n’entraineraitpas de compétition pour la lumière au sein de la végétation. Ce type de milieu, principalementdéfini par son caractère oligotrophe et sa faible capacité à neutraliser l’acidité du sol,semblerait donc essentiellement affecté par des mécanismes de toxicité de l’ammonium voired’acidification du milieu à long terme.Enfin, les moyens de restauration étudiés ont montré la difficulté de conserver et derestaurer de tels habitats potentiellement affectés par les dépôts d’azote. En effet, l’utilisationde fauches répétées avec exportation de la biomasse a montré son inutilité dans un systèmequi n’est pas influencé par la compétition pour la lumière. De même, l’étude des banques degraines a montré que ce pool d’espèces ne pouvait pas représenter le seul moyen deconservation des espèces caractéristiques. Ces résultats révèlent l’importance de conserver lesprairies acides existantes, principalement dans des sites soumis à de faibles dépôts ambiants. / To assess the impact of atmospheric nitrogen deposition on ecosystems, we werefocused on a patrimonial interest ecosystem: acid grasslands of Violion caninae. Within thesegrasslands, we aimed to (i) characterise temporal and spatial variation in plant speciescomposition along the French Atlantic domain and determine if nitrogen deposition andclimate variables could explain these patterns, (ii) understand processes underlined bynitrogen addition on vegetation and soil, and (iii) examine the potential conservation andrestoration ways.Temporal and spatial approach of acid grasslands brought to light changes in speciescomposition at local scale of community type but also at the national French Atlantic domainscale. At both local and national scale, these changes were linked to climate change withincrease of mean annual temperature and decrease of soil water availability. However at localscale, the most changes in species composition were experienced on sites with climate changeand also the highest chronic nitrogen deposition since the last 25 years. These changes inspecies composition occurred at the expense of short stature species like forbs whereasgrasses species were persistent and dominated vegetation. These changes are visible from 10-15 kg N ha-1 an-1, determined as the critical load for nitrogen in acid grasslands.The experiment allowed to highlight processes underlined in acid grasslands afternitrogen addition. In particular, nitrogen enrichment did not lead to light competition invegetation. These grasslands, mainly defined by poor-nutrient and low capacity to bufferacidity in soil, were essentially affected by ammonium toxicity or even acidification on thelong range.Finally, the study of conservation ways showed the difficulty to conserve and restorethe grasslands affected by nitrogen deposition. Indeed, more frequent cuttings with biomassremoval were useless in a system not influenced by light competition within vegetation. Thestudy of seed banks showed also that conservation ways could not be based just on seed banksto maintain characteristic species. These results highlight the importance to conserve theexisting acid grasslands, mostly in region with low ambient nitrogen deposition.

No description available.

Thesis (M.Sc. Agriculture (Pasture Science)) -- University of Limpopo, 2021 / Savanna rangelands are ecosystems which are characterized by the co-existence of scattered trees and shrubs with a continuous grass layer. However, the grass and tree balance has been highly altered as a result of disturbances caused by bush encroachment. Encroaching woody species have been shown to decrease species richness and abundance of the seed bank and ground‐layer diversity. So far little is known on the effect of bush encroachment and soil depth on the soil seed bank diversity in savanna rangelands. The objectives of this mini-dissertation were to (1) determine the influence of soil depth on soil seed bank diversity in bush encroached savanna rangelands, and (2) determine the relationships between soil seed bank herbaceous vegetation and physicochemical properties in encroached rangeland. In order to address these objectives, a savanna rangeland was demarcated into two encroachment gradients spanning from open to encroached rangeland. Within each encroachment gradient, six plots of 10 m x 10 m were randomly selected, whereby soil sampling and herbaceous vegetation were carried out and determined. In each replicate plot per encroachment level, five soil samples were randomly collected at 0-10 and 10-20 cm depths. The number of seedlings of different species emerging from the soil samples was used as a measure of the number of viable seeds in the soil and the composition of the seed bank using the seedling emergence method. The total seed densities showed significant differences (P<0.05) in the 0-10 cm depth layer in the open rangeland and encroached rangeland. Bush encroachment significantly (P<0.05) decreased the seed density of perennial grasses, specifically in 0-10 cm depth layer. Further, species diversity increased with bush encroachment in the 10-20 cm depth layer. Menhinick’s richness index showed no significant difference in the open and encroached rangeland, while species evenness decreased in the 0-10 cm depth layer and increased at 10-20 cm depth.The study also revealed negative correlations between organic carbon, calcium, clay, silt and forbs while mean weight diameter (MWD), a measure of soil aggregate stability was positively correlated with forbs. The canonical correspondence analysis (CCA) showed that pH, phosphorus, potassium and calcium were positively correlated to Eragrostis curvula and magnesium was negatively correlated to Panicum maximum. In open rangeland, CCA revealed that clay content was negatively correlated with species evenness while xii magnesium was negatively correlated to the Shannon Weiner index. Further, silt content was positively correlated with species richness and evenness. In the encroached rangeland, the CCA showed a negative correlation between magnesium and the Shannon Weiner index. The Sørensen’s index between soil seed banks and aboveground vegetation was low with index values of 0.22 and 0.24 in open and encroached rangeland, respectively. / AgriSeta

Invasive plants can outcompete native plants, replacing diverse plant communities with monocultures, which can negatively impact the whole ecosystem. One invasive plant, Phragmites australis, has invaded wetlands across North America. In Utah’s Great Salt Lake, it has greatly reduced the area of native plants that are important habitat for migratory birds. Here we describe experiments that assess multiple treatments for Phragmites removal and evaluate the return of native plants after Phragmites management. The treatments were applied to Phragmites patches at two scales (small 1/4-acre plots and large 3-acre plots) and across multiple sites to evaluate how patch size and environmental differences can influence the plants that return after Phragmites removal. The treatments (applied over 3 years and monitored two more) compared two different herbicides (glyphosate and imazapyr) and different herbicide and mowing timings. The treatments evaluated in the large patch study were 1.) untreated control 2.) fall glyphosate, winter mow, 3.) summer imazapyr, winter mow, 4.) summer glyphosate, winter mow. The treatments evaluated in the small patch study included treatments 1-4 above plus 5.) summer mow, fall glyphosate, 6.) summer mow, then black plastic solarization. In the small patches, we also monitored the seeds in the soil to assess how Phragmites management treatments can change the densities of Phragmites and native seeds. Fall glyphosate treatments were superior for Phragmites cover reduction. After the initial treatment, summer herbicide and mow treatments reduced Phragmites seed production, while fall glyphosate did not. Phragmites seeds were plentiful in the soil but were reduced following three years of all herbicide treatments. Native plant recovery following Phragmites management was extremely variable across sites. Sites with high soil moisture had better Phragmites removal and more native plants. But when flooding was deep, native plants were rare. Native seed density in the soil did not change due to Phragmites management, but soil seed densities were different across sites, which influenced native plant recruitment. Phragmites was removed more effectively and native plants returned in greater numbers in small patches compared with large. This was because small patches were typically near established native plant communities, which likely provided more native plant seeds and had hydrology that was less disturbed by human activity. In sites where native plants do not return after Phragmites management, practitioners may need to try revegetation with native plant seeds to restore important native plant communities.

The effect of shared enemies between invasive and native species has been argued to facilitate biological invasions (i.e., the apparent competition hypothesis or ACH). This study investigated a previously untested possibility: whether granivorous small mammals facilitate cheatgrass (Bromus tectorum) invasion by driving food-mediated apparent competition between cheatgrass and native grasses. Specifically, we tested three predictions that must be true if such apparent competition occurs. First, cheatgrass invasion augments total seeds available to granivorous small mammals. Second, density of granivorous small mammals increases in response to increased seed availability (simulated with experimental additions of cheatgrass seeds). Third, granivorous small mammals prefer seeds from native grasses over cheatgrass seeds. We tested these predictions in the Great Basin Desert of Utah, USA. Cheatgrass invasion augmented total yearly seed production. Granivorous small mammals preferred native seeds over cheatgrass seeds. However, neither abundance, richness, nor diversity of granivorous small mammals increased in response to experimental additions of cheatgrass seed. We therefore conclude that granivorous small mammals did not drive food-mediated apparent competition during the study period. The lack of support for the ACH in this study may suggest that the role of small mammal-driven apparent competition is either unimportant in the Great Basin, or that the appropriate indirect interactions between small mammals, cheatgrass, and native grasses have yet to be evaluated. Testing the third prediction required the separation of seeds from the soil matrix. We employed a chemical flotation methodology to recover target seeds from soil, and developed a novel method of decanting target material from the flotation solution. We compared the utility of the novel method to that of a traditional decantation method. Specifically, we compared effectiveness (the proportion of seeds recovered from a known sample), rapidity (the time required to decant that sample), efficiency (the number of seeds decanted per second), and recovery bias (the effect of relative density on seed recovery) between methods. Our proposed method was more effective, more rapid, more efficient, and less biased than the traditional method. Therefore, any future work relying on flotation to analyze seed banks should clearly describe how samples are decanted and should consider the proposed method as a potential means of enhancing the efficiency of chemical flotation.

The soil seed bank plays a dynamic role in the regeneration of plant communities after natural and anthropogenic disturbance. In this thesis, I addressed how disturbances influence the vegetation and seed bank of Florida rosemary scrub. In Chapter One I evaluated changes in species composition and spatiotemporal pattern of the vegetation and seed bank along a gradient of disturbance. During the summers and winters of 2007-2009 percent ground cover and seed bank species composition were assessed among replicates of three vegetation types subjected to minimal, moderate, and extreme anthropogenic disturbance (native rosemary scrub, degraded scrub, and agriculturally improved pasture, respectively). These vegetation types shared the same soil and topographic characteristics but differed in disturbance history. I found that species composition and spatial pattern varied with disturbance. In pastures the compositional and structural characteristics of rosemary scrub were lost and only native scrub species able to evade herbivory persisted in this community. Native and degraded scrub differed most from each other in species abundances and spatial pattern. Degraded scrub showed highest abundance of subshrubs and a spike moss species, while rosemary scrub was dominated by shrubs. The seed banks of scrub herbs in degraded scrub had a tendency towards a random spatial distribution that lacked association with aboveground cover. Conversely, rosemary scrub seed banks tended to have an aggregated distribution and were associated with occurrence of conspecific species aboveground, litter, and shrub cover. These results indicated a change in the spatial heterogeneity of the seed banks of scrub herbs in degraded scrub. In Chapter Two I evaluated changes in seed bank density with time-since-fire in native rosemary scrub. Due to large pulses of recruitment immediately after fire and population decline iii with time-since-fire, I predicted seed density with time-since-fire would follow a unimodal function with low density in early and late years post-fire, and highest density at intermediate time-since-fire. I compared seed density data among sites with different time-since-fire: two sites each of three, six, ten and 24 years time-since-fire and three long-unburned sites ( > 24 years). Variability in seed bank composition and density increased with time-since-fire and only recently burned stands were distinctly different from the other time-since-fire age classes. Some species and functional groups did exhibit a quadratic or cubic association to time-since-fire (ruderal herbs, subshrubs, Ceratiola ericoides, Lechea cernua, Paronychia chartacea, Phyllanthus tenellus); however, timing of the peak in seed density varied depending on life span and age of reproductive maturity. Scrub herbs were the most abundant functional group in the seed bank and showed highest density in the first ten years post-fire. This pattern corresponds to the pattern of aboveground species abundance and suggests abundances above- and belowground are closely linked. Understanding the dynamics of the seed bank in both naturally and anthropogenically disturbed communities in Florida rosemary scrub is important for the restoration of scrub habitat and management of existing populations of endangered and threatened scrub species endemic to the Lake Wales Ridge in central Florida.

The decline of floodplain vegetation along the Lower River Murray, South Australia, has evoked recommendations for ‘environmental flows’ to restore and maintain the health of the ecosystem. To assist managers to maximize benefits from environmental flows, this thesis considers the significance of water for germination and recruitment in key floodplain plant species. Three dominant species are considered, including two trees, river red gum (Eucalyptus camaldulensis) and black box (E. largiflorens), and an understorey shrub, tangled lignum (Muehlenbeckia florulenta). The soil seed bank was dominated by terrestrial annual native plants. Among 1400 seedlings, a single river red gum was found, and no black box or lignum, suggesting that these species do not contribute to the persistent soil seed bank and rely instead on aerial seed banks (serotiny). Sampling of the soil seed bank was continued to determine when seed fall might coincide with appropriate soil moisture conditions. Responses of the soil seed bank to varied water regimes were compared to determine requirements for seedling survival. The results indicated that species richness, rapidity of response and survival time were all promoted by sustained soil moisture. Stands of eucalypts in various states of health (from very stressed to very healthy) were monitored to identify seasonal patterns in bud crops, flowering, fresh leaves and volumes of seed released from the aerial seed bank. Distinct seasonal phenological patterns were apparent, and suggested alternating flowering among individual trees (biennial for red gum, bi-annual for black box), producing an annual peak in summer. Peak seed rain occurred in summer (December–March) in healthy trees for both red gum and black box, with light seed rain continuing throughout the year. Seed fall from stressed trees was much reduced. Stressed trees responded after a second watering event, with much more varied and extended annual seed fall patterns. Lignum showed a spring peak in flowering and seed production. There was a prolific response of flowering and seeding to rainfall, but few seedlings survived. Vigorous vegetative growth occurred in existing plants in response to rainfall and watering but no new cloned plants were found during the study. An investigation of chromosomes as a potential tool to appraise the balance between sexual and asexual reproduction in lignum proved inconclusive, although a previous report of octoploidy in lignum was confirmed. Seeds from all three species and lignum cuttings were tested for their responses to varied watering regimes, based on combinations of simulated rain and flood conditions. The optimal soil moisture for continued growth and survival in all seeds and cuttings was 10 25%, with moisture values <10% causing wilting and death. The results also suggested that red gum and black box seeds which germinate in water under flooded conditions need to be stranded onto moist soil at the water’s edge within 10 days, for the seedling to continue to grow. It was also concluded that germination on rain-moistened soil is a key supplementary mechanism for recruitment, particularly between irregular flood events. For greatest benefit, the timing of environmental flows should complement any seasonal rainfall and irregular flooding that may occur. Extension of suitable soil moisture conditions (10-25%) for as long as possible after >5 mm rainfall, or after over-bank flows, would increase chances for survival of seedlings. December is the most likely month for maximal benefit from watering in the Lower Murray Valley, for germination and recruitment, based on regional rainfall and flooding patterns. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1344528 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008