Research@Lincoln
Research@Lincoln is an open access institutional repository collecting the research produced by Lincoln University staff and students. You may also be interested in Data@Lincoln or Lincoln University Living Heritage.
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Item Restricted High maintenance of rhizosphere soil C and N equilibrium regardless of plant species or species traits(Frontiers Media S.A., 2021-10)Factors affecting the deposition of carbon and nitrogen into the rhizosphere soil have important implications for natural and managed ecosystems. These include the invasiveness of plants, extent to which ecosystems sequester soil carbon, through to regulation of N flow within and from agricultural ecosystems. This study determined if the close elemental ratios often measured in soils are evident within the highly active rhizosphere compartment, or rather potentially emerge to a conserved ratio (over time) from different initial rhizosphere states. Toward this, we assessed the rhizosphere C and N content (and C:N ratio) of 37 plant species; these were further grouped into the categories provenance (native or exotic to New Zealand), form (forb, grass, shrub, or tree), root-based nitrogen fixation symbiosis (+/– N-fixation), or mycorrhization type. Furthermore, the potential nitrification rate (PNR) among the plant rhizosphere soils was quantified to explore relationships between nitrate formation and the total C and C:N ratio. Mycorrhization status, provenance, and form had no significant influence on nutrient status nor PNR in rhizosphere soil samples (p > 0.05). However, total C and total N were significantly increased in the rhizosphere of N-fixing species (p < 0.02). These increased in proportion, with the C:N remaining constant for both groups (∼12.24; p = 0.79). Rhizosphere PNR did not vary with categories of plants tested and had no correlation to rhizosphere total C, total N, nor C:N ratio (p > 0.3 for all). Overall, this study showed that conservation of nutrient ratios often measured in soils are present within the rhizosphere, where initial inputs of C and N enter the soil ecosystems. With the exception of N-fixing plant species, rhizosphere soils retain remarkably high conservation in C, N, C:P, and PNR among key groupings.Item Restricted What happens in Europe stays in Europe: Apparent evolution by an invader does not help at home(Wiley-Blackwell, 2020-08)Some invasive plant species rapidly evolve greater size and/or competitive ability in their nonnative ranges. However, it is not well known whether these traits transfer back to the native range, or instead represent genotype-by-environment interactions where traits are context specific to communities in the new range where the evolution occurred. Insight into transferability vs. context specificity can be tested using experiments performed with individuals from populations from the native and nonnative ranges of exotic invasive species. Using a widespread invasive plant species in Europe, Solidago gigantea, we established reciprocal common garden experiments in the native range (Montana, North America; n = 4) and the nonnative range (Hungary, Europe; n = 4) to assess differences in size, vegetative shoot number, and herbivory between populations from the native and nonnative ranges. In a greenhouse experiment, we also tested whether the inherent competitive ability of genotypes from 15 native and 15 invasive populations differed when pitted against 11 common native North American competitors. In common gardens, plants from both ranges considered together produced five times more biomass, grew four times taller, and developed five times more rhizomes in the nonnative range garden compared to the native range garden. The interaction between plant origin and the common garden location was highly significant, with plants from Hungary performing better than plants from Montana when grown in Hungary, and plants from Montana performing better than plants from Hungary when grown in Montana. In the greenhouse, there were no differences in the competitive effects and responses of S. gigantea plants from the two ranges when grown with North American natives. Our results suggest that S. gigantea might have undergone rapid evolution for greater performance abroad, but if so, this response does not translate to greater performance at home.Publication Embargo Can the presence of a fungal volatile organic compound improve plant resilience to abiotic stress? : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University(Lincoln University, 2023)Climate change is a matter of increasing concern, as the severity, duration, and area affected by drought have steadily risen since the 1970s. These changes have severely affected the agricultural industry, as drought stress is a major contributor to crop loss. Therefore, it is crucial to develop new strategies to address this problem. Seed coating shows the potential to mitigate the challenges faced by the agricultural industry, as it provides physical and physiological properties to seeds, helping alleviate both biotic and abiotic stress. This research aims to evaluate the protective effect of the fungal volatile (FVOC) organic compound when applied via polymer seed coating. The FVOC seed coating treatment's effects were assessed regarding plant emergence, resilience to drought stress, and transgenerational stress adaptations. By conducting a comprehensive transcriptomic analysis, it was possible to identify the transcriptional changes induced by the presence of the FVOC molecule. The application of the FVOC led to significant changes in gene expression in plants under drought-stress conditions, enabling them to cope more effectively with stress. Moreover, when plants grown from FVOC-treated seeds were exposed to a second round of drought stress, they exhibited a more specific and refined response to this stress. Moreover, when the second-generation plants derived from FVOC-treated seeds were exposed to drought, they exhibited improved resilience to environmental stress. This observation strongly suggests the occurrence of transgenerational changes. The drought stress initially triggered these changes in the first-generation plants and was further enhanced by the presence of the FVOC molecule. Subsequently, these changes were transmitted to the second generation, resulting in enhanced resilience plants.Item Restricted Impact of biocrust on soil nitrogen maintenance and microbial composition in citrus orchards under varying urea application rates(Elsevier B.V., 2024-09)Biocrust communities and their effects on soil nitrogen (N) content in natural drylands have been extensively studied. However, their significance in citrus orchards, which are typically managed with N fertilizer, remains unclear. To address this, an investigation was conducted in a citrus orchard subjected to varying levels of urea application (0 %, 70 %, and 100 % of the local N fertilizer application) over three years. The study focused on biocrust communities dominated by bryophytes, examining their community and individual characteristics, and comparing the properties and microbial communities of soils with and without biocrust cover. The results showed that biocrust had the highest percent coverage (56.1 %) in the plot with 70 % local N fertilizer application. Dicranella heteromalla was the dominant biocrust species across all treatments, exhibiting greener and longer leaves with 70 % local N fertilizer application. Biocrust cover significantly (P < 0.01) influenced soil total nitrogen content, soil water content, soil total carbon content, and soil dissolved organic carbon content. In contrast, fertilizer application had non-significant effects on the physicochemical properties of soils, regardless of biocrust cover. A notable difference in bacterial phyla composition was observed between soils with and without biocrust cover (PERMANOVA, P = 0.001), although fertilization did not significantly affect the bacterial diversity index. Additionally, biocrust cover significantly (P < 0.01) influenced predicted soil bacterial functional groups, including ureolysis and nitrogen fixation, while fertilizer application had a weaker impact on these bacterial functional groups. In conclusion, nitrogen application altered the community and dominant species characteristics of biocrust but did not overshadow the effects of biocrust on soil N dynamics. In the citrus orchard with varying levels of urea application, biocrust played a crucial role in soil water retention, N maintenance, and predicted microbial ecological functions related to N cycling.Item Restricted Introduction: indigenous self-governance in the Arctic States(Taylor & Francis, 2024-01-01)The theme of this special issue is indigenous self-governance in Arctic states. A common characteristic of the states that are partly located in the Arctic – Canada, Denmark, Finland, Norway, Russia, Sweden, USA – is that they all have indigenous peoples, and all have some form of self-government. There has been relatively little research on the similarities and differences between the sub-state autonomy structures within the Arctic states from a political science perspective (although with important exceptions, see below). This is somewhat surprising given the growing interest in the Arctic region during the last 15 years, where some of these autonomous units play an increasingly important role. This special issue asks how different are these self-governing units? How did they evolve into their current form? Do they have a distinct Arctic indigenous character?
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