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The suitability of water hyacinth in biogas production was evaluated as a means of waste management in the interests of sustainable energy production. Batch anaerobic digestion (AD) of water hyacinth was conducted to determine the optimal pre-treatment method for maximum methane production. Physical pre-treatment methods produced a highest cumulative methane of 2.3 L during batch AD. The selected pre-treatment method, hand-cutting, was further evaluated in a semi-continuous AD using both mono- and co-digestion. The emphasis was on identifying microbial communities involved and their response to organic loading rates (OLRs). The Illumina Miseq results proved that bacterial communities were more sensitive to disturbances caused by irregular OLRs as compared to archaeal communities. In addition, the variation in substrate nutrients as a result of mono- and co-digestion of water hyacinth, contributed to variations in the bacterial diversity. For example, Bacteroides and Petrimonas diversity varied between mono- and co-digestion. Overall, the study verified that water hyacinth is a suitable feedstock for biogas production and the simple pre-treatment methods are recommended. Furthermore, OLRs influenced the microbial community structure and associated biogas yield. / National Research Foundation (South Africa) / Environmental Science / M. Sc. (Environmental Science)

South Africa is one of the world's most biologically invaded countries and has spent billions of rands on efforts to eradicate alien invasive plants. Chemical and mechanical control methods have varied in success and the need for integrated management strategies has been realised. This requires a better understanding of all aspects of the invasion process. Some of the most invasive plant species rely on vertebrate dispersers which facilitate long-distance seed dispersal. Frugivory is based on a mutualism in which the frugivores gain a resource and the plants benefit from seed dispersal away from the parent plant. Seed germination itself may either be enhanced, reduced or not affected at all after gut passage. The first aim of this study was to determine if generalist avian frugivores and a fruit bat species (Epomophorus wahlbergi) enhance or decrease seed germination of invasive alien plants in South Africa, by either pulp removal or seed coat abrasion, or if they serve as dispersers only. The second aim was to determine if avian frugivores are able to meet their energetic demands by feeding on a specific alien fruit diet. Finally, we also quantified the nutritional content and morphological characteristics of fleshy fruits of various invasive alien and exotic plant species. Avian frugivores: Red-winged Starlings (Onychognathus morio), Speckled Mousebirds (Colius striatus), and Dark-capped Bulbuls (Pycnonotus tricolor), varied in their effects on the germination success of seeds of four invasive alien species, namely: Lantana camara, Solanum mauritianum, Cinnamomum camphora, and Psidium guajava. However, this was not associated with differences in seed retention times. Similar germination success was observed for avian ingested and de-pulped seeds. This was also observed for fruit bat spat and depulped seeds of Psidium guajava, Melia azedarach, Eriobotrya japonica, and Morus alba. Therefore seed coat abrasion was not important for the germination of these fleshy-fruited invasive alien plants. Pulp removal resulted in significantly earlier seed germination as well as higher seed germination percentages than in the case of whole fruit controls for some of these invasive species. Gut passage is thus important for long-distance dispersal, and in some cases, for enhanced germination of seeds. The invasive Solanum mauritianum and indigenous congener S. giganteum showed similar germination responses, with both ingested and depulped seeds germinating profusely. However, S. giganteum benefited from pulp removal as seeds from whole fruits had less germination. Avian frugivores varied significantly in most energetic parameters calculated when given diets of invasive alien fruit. Speckled Mousebirds and Dark-capped Bulbuls were able to maintain body mass and efficiently process fruits of all four alien invasive plants, while Red-winged Starlings were only able to do so on lipid-rich C. camphora and sugar-rich S. mauritianum. Furthermore, frugivores also adjusted their feeding behavior by eating more nutritionally poor fruit and less energetically rewarding fruit. Fruit bats consumed more fruit per gram body mass than avian frugivores did. They therefore process proportionately more seeds than avian dispersers and thus their role in invasive seed dispersal, which has previously been underestimated particularly in South Africa, is highlighted. Fruits of invasive plant species were similar in morphology, but greater in nutritional content, than fruits of indigenous species. These fruits also contained small, light seeds with approximately only 30% having more than 10 seeds per fruit. The ability of frugivores to efficiently process these fruits and the greater nutritional rewards offered by these provide new insights into why these invasive fruits are preferred by frugivores. In addition, invasive alien plants may have a competitive edge over indigenous species because of their larger reproductive outputs and not necessarily because of greater germination success. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Invasiva främmande arter utgör idag ett av de största hoten mot biologisk mångfald, både nationellt och globalt. Sveriges geografiska läge har medfört en relativt begränsad utbredning av invasiva främmande arter men problematiken förväntas öka med framtida klimatförändringar. SLU ArtDatabanken har därför riskklassificerat arter i Sverige utifrån deras potentiella ekologiska effekt på ekosystem samt deras invasionspotential. ArtDatabankens rapport ska ligga till grund för en framtida nationell förteckning där de invasiva främmande arterna med störst skadeverkan nationellt kommer att omfattas av svensk lagstiftning. I vår rapport undersöks vilka invasiva främmande landbaserade växter som utgör de största hoten mot ekskogar i Västra Götalands län. Resultatet kan ge ett underlag för att prioritera vilka invasiva främmande växtarter som Länsstyrelsen, i ett tidigt skede, bör rikta åtgärder mot för att bevara och skydda ekskogar i länet. Ek är särskilt skyddsvärt då släktet är ett av Europas viktigaste trädslag och utgör habitat för en stor mängd arter. Invasiva främmande växter kan utgöra ett hot mot ekskogar genom exempelvis beskuggning och konkurrens vilket kan påverka träden negativt.  Vi har i vår rapport baserat urvalet av invasiva främmande arter på ArtDatabankens risklista samt EU:s förteckning över invasiva främmande arter av unionsbetydelse. Arbetet utfördes som en GIS-analys och en fältstudie. GIS-analysen baserades på observationer i SLU Artportalen och i fältstudien inventerades 4 skyddade ekskogar i länet. De olika resultaten kan indikera på ett bristfälligt underlag i SLU Artportalen. Resultatet av GIS-analysen visade att det största hotet, både nutida och framtida, mot undersökta ekskogar var parkslide (Reynoutria japonica), medan fältstudien visade att druvfläder (Sambucus racemosa) utgjorde det största nutida hotet i inventerade ekskogar. Antalet observationer av invasiva främmande växter från vår artlista i tätortsnära ekskogar, med tillhörande buffertzoner om 2 kilometer, var fler än i ekskogar och dess buffertzoner som klassades som icke tätortsnära. Skillnaden i antal observationer var signifikant. Resultatet kan bekräfta att invasiva främmande växter är mer förekommande i och kring tätorter, varför hoten mot tätortsnära ekskogar kan vara större än mot icke tätortsnära. Detta överensstämmer med tidigare forskning som visar att spridning av invasiva främmande växter gynnas av mänskliga aktiviteter såsom trädgårdsodling samt hantering och transport av massor. / Invasive alien species pose one of the greatest threats against biodiversity, in Sweden and globally. The northern location of Sweden has limited the distribution of invasive alien species, however, issues concerning invasives are predicted to increase with future climate change. The Swedish University of Agricultural Sciences has compiled a report containing a list of more than 1000 invasive alien species which have been classified based on their ecological effect and invasion potential. The report will be the basis of the future national list of legislated species. In our report, we examine which invasive alien land-based plant species pose the greatest threats against oak tree forests in the county of Västra Götaland. Our results can be used to prioritize which invasive alien plant species the County Administrative Board, in an early stage, could direct measures against to protect oak tree forests in conservation management. The protection of oak is crucial since it is one of the most important genera in Europe, both economically and ecologically, entailing a national responsibility. Shading and competition are major threats, affecting oak trees negatively and prohibiting rejuvenation.   The species selected for analysis in our report was based on the list of invasive alien species compiled by the Swedish University of Agricultural Sciences in combination with the EU’s list of species of union concern. This report contains a GIS analysis and a field study. The GIS analysis was based on observational data in SLU Artportalen and in the field study, 4 protected oak tree forests were surveyed. The difference in results may indicate inadequate data in SLU Artportalen. Our GIS analysis showed that Japanese knotweed (Reynoutria japonica) posed the largest present and future threat against analyzed oak tree forests, while red-berried elder (Sambucus racemosa) posed the largest present threat against examined oak tree forest according to the survey in our field study. The number of observations of selected invasive alien plant species in oak tree forests, with associated surrounding buffer zones of 2 km, close to urban areas was higher than in oak tree forest, with associated buffer zones, not close to urban areas. The difference in number of observations was significant. Our result can confirm that invasive alien plant species are more numerous in urban areas than in non-urban areas, meaning the threat against oak tree forest close to urban areas may be greater. This corresponds with previous research showing that the dispersal of invasive alien plant species is promoted by human activities, such as gardening and the disposal and transportation of waste from excavations.

<p dir="ltr">To reduce the establishment and spread of invasive plant species, the Environmental Quality Incentive Program (EQIP) was created in 1996 to provide financial and technical assistance to private landowners to aid in conservation practices and address environmental concerns. From 2014-2022, approximately $90 million dollars was obligated to the EQIP for completed contracts of over 240,000 hectares in Indiana. However, to date, there has been no examination of whether participation in conversation cost sharing programs has resulted in the recovery of native tree diversity, growth, and reproduction following the treatment of invasive plants. Furthermore, there is a gap in our understanding of the effectiveness of EQIP and its success in achieving and maintaining management goals. This thesis quantifies the composition, diversity, regeneration density and growth of tree species in response to invasive plant treatments at sites that participated in the EQIP. In particular, I investigated how the species composition of woody seedlings (stems < 2 cm dbh) and woody saplings (2 – 5 cm dbh) differed across EQIP-treated and untreated reference plots. I then examined how native species richness and diversity values differed between EQIP-treated and untreated plots. Lastly, I used dendroecological methods to determine how treatment of invasive shrubs affected overstory tree growth. Across the state, I found that native species richness of seedlings and saplings was greater in EQIP-treated plots then within reference plots. Reference plots were associated with invasive species such as <i>Lonicera maackii</i> (Amur honeysuckle), <i>Rosa multiflora</i> (multiflora rose), <i>Elaeagnus umbellata</i> (autumn olive) and <i>L. japonica</i> (Japanese honeysuckle), while EQIP-treated plots were associated with native tree species, such as <i>Carya ovata</i> (shagbark hickory),<i> Ulmus americana </i>(American elm), <i>Fraxinus americana</i> (white ash), <i>Liriodendron tulipifera</i> (yellow-poplar), <i>Quercus alba</i> (white oak), <i>Q. velutina</i> (black oak), and shrubs, such as <i>Rubus allegheniensis</i> (Allegheny blackberry) and <i>Lindera benzoin</i> (spicebush). I observed that trees generally had greater basal area increment growth following invasive shrub treatments; therefore, the reduction of invasive shrub dominance on EQIP-enrolled lands has led to a small, but significant, increase in overstory tree growth. I observed high within-group variability in growth for EQIP-treated and reference plots, likely due to differing management strategies across privately owned forests. Overall, my results demonstrate that participation in the EQIP has positively benefited species richness, and native species composition, and tree growth.</p>