Initiating temperate grassland restoration by controlling the dominant weed species; a case study with Nassella trichotoma

Temperate grasslands are globally important biomes, in that they (i) provide habitat for a wide diversity of species, (ii) sequester large stocks of carbon, and (iii) provide forage for important pollinators (Chapter 1). These ecosystems often fall within highly fertile areas, and consequently humans have come to depend on them to provide high quality forage for grazing livestock and land for agricultural development. Temperate grasslands are considered to be critically endangered on a global scale. The grazing industry relies upon healthy and productive grasslands for the production of a substantial proportion of human food products, however, when these systems incorporate unsustainable land-management practises, such as over-grazing and continual fertilisation with inorganic matter, has resulted in a significant decline in important native grass species. This has resulted in encroachment of unpalatable, noxious plants, which decrease the quality of available forage. One such noxious weed species, Nassella trichotoma, known commonly as serrated tussock, is having a significance impact on the constitution of temperate grasslands and grazing systems, globally, due to its unpalatability and competitive growth form. In order to return temperate grasslands to a fully-functional and a high-quality forage state, human intervention in terms of ecosystem restoration is required. The control of noxious species, together with the reintroduction and establishment of native species, is a critical step for restoration efforts with the return of native plant diversity, and the re-establishment of ecosystem services, such as habitat for higher trophic levels. This thesis reviews and overlaps the scientific disciplines of ecosystem restoration (Chapter 2), weed science relating to N. trichotoma (Chapter 3), and environmental management in order to provide solutions for controlling N. trichotoma in non-native grassland communities (Chapter 4). The effect of direct herbicide application, soil tillage, grazing exclusion, fire, and broadcasting native seeds for the control of this dominant weeds in a total of 13 different combinations is investigated. The experimental plots were surveyed over a four-year period and soil cores were collected over a three-year period to survey the seedbank density. It was found that the inclusion of fire significantly increased the establishment of the native broadcast species. Also, without the integration of fire or tillage, N. trichotoma recovered, and consequently was observed to be the dominant species in the final sampling period. To support the findings of Chapter 4, research into the seed longevity and seedbank persistence of N. trichotoma was undertaken in Chapter 5. It was found that less than 10% of the seeds were observed to be viable after 12 months of burial in field. In addition to this, the longevity of the seeds was determined by rapidly ageing the seeds through exposure to high relative humidity and temperature. This process determined that N. trichotoma produces transient seedbanks, referring to those that persist for 12 months or less, and therefore the seedbank would be reliant on new seed input annually to remain a competitive threat. This implies that management control of new seed fall is essential to prevent the reestablishment of the seed bank. The seedbank persistence for N. trichotoma is complicated by disturbance events such as fire. To investigate this impact, four different collection years; 2016, 2017, 2018, and 2019 were subjected to increasing heat (80, 100, 120, or 140OC) and time of exposure (1, 3, 6 or 9 minutes) by placing them into a temperature-controlled oven for the given treatment. It was found that only the 140OC treatment was significant for killing N. trichotoma, as detailed in Chapter 6. High moisture content (95%) increased the seeds sensitivity to radiant heat, with all tested temperature effective for killing this species. The seedlings were not killed by the tested treatments. Management implications and recommendations for the control of N. trichotoma in temperate grasslands (Chapter 7) include; (i) the use of herbicide in Autumn to prevent seed set in the following summer, and (ii) in addition to initial herbicide, use, subsequent fire treatment and broadcasting native seeds appear to provide ongoing competition against N. trichotoma reestablishment in treated areas. Further, high fire intensities, where the soil is heated to 140OC or more, can kill N. trichotoma’s seedbank and prevent its recruitment. In all cases of treatment, monitoring recruitment from the seedbank is recommended for up to one year after treating a site. This thesis suggests that localised eradication of N. trichotoma is achievable in as little as three years if (i) above-ground plants are treated, (ii) seedling recruitment from the seedbank is managed intensely within the first year, (iii) high densities of native grass is established to provide competition, and (iv) the addition of new seed is prevented.Doctor of Philosoph

The response of Nassella trichotoma (serrated tussock) seeds and seedlings to different levels of fire intensity

Context Fire is an important disturbance regime in grassland communities, since it is responsible for stimulating the regeneration of many species and for maintaining levels of biodiversity. When invasive plants, such as Nassella trichotoma, establish and become widespread in a grassland community, these important fire events can be altered in intensity and frequency, which means that they are able to facilitate the establishment of the exotic species. Therefore, before fire can be recommended as a suitable control technique for invasive species, or alternatively to be integrated into grassland restoration programs, understanding the response of the seeds of exotic species to high temperatures, such as those experienced during a fire, should be well understood. Aims Our aim was to identify their response to a gradient of temperatures associated with different levels of fire intensity. We examined how increased duration of exposure affects their response, and whether seed age or seed moisture content affect the germination response of this species. Methods To gain a fuller understanding of the fire response of N. trichotoma’s seedbank, seeds were collected in 2016, 2017, 2018 and 2019 and then stored until the commencement of the experiments in 2020. Selected seeds were first subjected to an increasing temperature gradient (80°C, 100°C, 120°C, 140°C, and a control), and an increasing duration of exposure (of 1, 3, 6, and 9 min). In the second experiment, one population was selected to test these same temperatures and duration of exposure after the seeds were hydrated to 15%, 50%, or 95%. Last, seedlings were grown for 3 months under glasshouse conditions and then exposed to increasing temperatures (20°C, 60°C, 80°C, 100°C, and 120°C), and an increasing duration of exposure (3, 6, and 9 min). The seedlings were assessed 2 weeks after the heat exposure for signs of damage. Key results It was found that increased temperatures and duration of exposure had a subtle negative effect on germination parameters, including reduced total germination and increased time to 50% germination. The 140°C treatment was seen to be a significant threshold because it killed all the seeds at any duration of exposure. A significant difference among the ages of each seed lot was observed to be a factor on the tested germination metrics, with the oldest tested population (2016) demonstrating the highest germination percentage, uniformity, and rate. Seed germination percentage was significantly reduced for seeds hydrated to 95% compared with the control treatment, whereas no significant difference was observed for the seeds hydrated to 15% and 50%. For the heat treatment of the seedlings, damage to the leaves was observed in the 80°C, 100°C, and 120°C treatments, with some plants in the 120°C treatment experiencing extensive damage prior to resprouting. No seedlings were killed at the tested temperatures. Conclusions Results of this study indicated that fire may be a useful tool for reducing seedbank density by killing a high proportion of the seeds on the soil surface, or located within the top 1 cm of the soil profile, but not for seeds buried more deeply. Efficacy of fire on surface and shallow-buried seeds is improved with high seed moisture content however, these seeds buried below this depth are still protected by the soil from the lethal effects of temperature. Implications Fire implemented before seed set could be used to effectively kill a large proportion of N. trichotoma seeds. However, for more comprehensive control, it is recommended that chemical treatment is integrated with the fire treatment to improve the overall control efficiency

Assessing seedbank longevity and seed persistence of the invasive tussock grass nassella trichotoma using in-field burial and laboratory-controlled ageing

The ability to produce highly dense and persistent seedbanks is a major contributor to the successful widespread establishment of invasive plants. This study seeks to identify seed persistence and seedbank longevity for the invasive tussock grass Nassella trichotoma (Nees.) Hack. ex Arechav in order to recommend management strategies for preventing re-emergence from the seedbank. To determine the seedbank longevity and persistence, two experiments were conducted: (i) seeds were buried at four depths (0, 1, 2, and 4 cm) and collected and assessed for viability, seed decay, and in-field germination after 6, 9, 12, 15, and 18 months of field burial; and (ii) seeds were exposed to artificial ageing conditions (60% RH and 45 °C) for 1, 2, 5, 9, 20, 30, 50, 75, 100, and 120 days, and viability was determined through germination tests and tetrazolium tests. Less than 10% of the seeds collected after 12 months of in-field burial were viable. The artificial ageing treatment found germination declined to 50% after 5.8 days, further suggesting that N. trichotoma seeds are short lived. The results from both experiments indicate that N. trichotoma has a transient seedbank, with less than 10% of the seeds demonstrating short-term persistence. It is likely the persistent seeds beyond 12 months were exhibiting secondary dormancy as viable seeds did not germinate under optimal germination conditions. The “Best Practice Guidelines” recommend monitoring for seedbank recruitment for at least three years after treating N. trichotoma infestations. The results of this study support this recommendation as a small proportion of the seeds demonstrated short-term persistence. © 2022 by the authors

Cultivation of low tetrahydrocannabinol (THC) Cannabis sativa L. cultivation in Victoria, Australia: Do we know enough?

Late 2017, the ban on the cultivation and consumption of low tetrahydrocannabinol (THC) Cannabis sativa L. in Victoria, was lifted by the Federal Government of Australia. Its legalization presents the opportunity for Victoria to become a leading producer and distributer of these economically valuable hemp products. However, as a novel crop to Victoria, there is little information available for obtaining economically viable yields. Therefore, the objectives of this review were to firstly, develop an understanding of the environmental requirements shared by C. sativa cultivars, and what conditions promote fibre and grain yields. Secondly, it seeks to identify what farming practices have been conducted throughout Europe, Canada and China, and to explore whether these practices could be adapted to Victoria. Thirdly, the review will assist in making recommendations regarding which cultivars would be 'potential' candidates for commencing trials under Victorian climates so to find out the varieties that can provide high yields for fibre, grain and dual-purpose production. This review notes that Victoria shares a similar climate to central Europe, and has an ideal climate for the development of a successful hemp industry, as it has suitable lengths of daylight throughout spring and summer months and meets the precipitation requirements. This review has thus strongly suggested that the properties and attributes of European varieties of C. sativa should be further researched for site-specific cultivation in Victoria for fibre, grain and dual-purpose production in order to maximise harvest yields. © 2007-2019 Southern Cross Publishing-Australia

An integrated approach for the restoration of Australian temperate grasslands invaded by Nassella trichotoma

Invasive plants are considered to be one of the biggest threats to environmental assets, and once established, they can be immensely difficult to control. Nassella trichotoma is an aggressive, perennial grass species, and is considered to be one of the most economically damaging weeds to grazing systems due to its unpalatability, as well as being one of the leading causes of biodiversity loss in grassland communities. This species produces high density seedbanks that rapidly respond to disturbance events. Despite control programs being developing in Australia since the 1930s, this species is still widespread throughout south-east Australia, indicating that a new management approach is critical to control this Weed of National Significance at the landscape scale. The present study explored the effect of 12 different combinations of herbicide, fire, a second application of herbicide, grazing exclusion, tillage and broadcasting seeds in order to reduce the above and below-ground density of N. trichotoma. A control treatment was also included. The results were assessed using a Hierarchy analysis, whereby treatments of increasing complexity were compared for their efficacy in reducing N. trichotoma cover and seedbank density, while simultaneously increasing the establishment of the broadcast species. Whilst all integrated treatments effectively reduced N. trichotoma’s seedbank, the treatments that included fire performed significantly better at simultaneously reducing N. trichotoma and increasing the establishment of broadcasted seeds. Overall, the integration of herbicide, fire and broadcasting native seeds was observed to provide the most economically feasible management strategy for the landscape scale restoration of a degraded temperate grassland dominated by N. trichotoma. © 2022, The Author(s)

Challenges Inherent in Controlling Prickly Pear Species; a Global Review of the Properties of <i>Opuntia stricta, Opuntia ficus-indica</i> and <i>Opuntia monacantha</i>

Opuntia species (prickly pear) were deliberately introduced to many countries around the world for fruit, cochineal dye production, living fencing or as ornamentals. They are now some of the world’s most significant weeds, particularly in regions with warm and or dry climates, as they pose threats to economic and environmental assets. In addition, they can cause considerable health issues for humans and animals. Opuntia spp. have prolific reproduction abilities, being able to reproduce both vegetatively and by seed. They have generalist pollination and dispersal requirements, which promotes their establishment and spread. Opuntia stricta, O. monacantha and O. ficus-indica are the most globally widespread of the Opuntia spp. In many countries, biological control agents, particularly the cactus moth (Cactoblastis cactorum) and various cochineal insects from the Dactylopius genus, have successfully reduced land-scape scale populations. On a smaller scale, controlling these weeds by either injecting or spraying the cladodes with herbicides can provide effective control. Care must be taken during herbicide treatments as any untreated areas will regenerate. While biological control is the most cost and time effective control method for landscape-scale infestations, further research into the combined efficacy of herbicides, fire, grubbing and pre-burial techniques would be beneficial for land managers to control small-scale and establishing populations. It would also be useful to have greater knowledge of the potential seedbank longevity and seed ecology of these species so that integrated management strategies can be developed to not only deal with initial populations but also the subsequent seedling regrowth

Stochastic Training of Future Economists in the Educational Establishments in Germany

У статті проведено аналіз підходів до стохастичної підготовки майбутніх економістів у Федеративній Республіці Німеччина. Змістове наповнення стохастичної підготовки в початковій школі розкрито через поєднання змістових (дані, частота та ймовірність) та загальних (представлення інформації; аргументація; вирішення проблем; моделювання; автоматизація) компетенцій. У середній школі зміст навчання стохастики сформовано як результат взаємодії змістових (дані та визначення шансів), процесуальних математичних (здатність до математичного обґрунтування; розв’язування математичних задач; математичне моделювання; використання математичних понять; застосування символічних, формальних та технічних елементів математики; здатність використання математики в комунікації) та загальних (відтворювання; встановлення залежності; узагальнення та рефлексія) компетенцій. Зміст курсу стохастики в навчанні майбутніх економістів у вищих навчальних закладах Німеччини представлено на прикладі модулів Статистика І (Описова статистика та теорія ймовірностей) та Статистика ІІ (Узагальнююча статистика).This paper analyzes approaches to stochastic training of future economists in the Federal Republic of Germany. The content of stochastic training in the elementary school is revealed through a combination of content (data, frequency and probability) and general (information representation; reasoning; problem solving; modeling; automation) competencies. In the secondary school learning stochastics content is formed as a result of the interaction of content (data and identifying chances), procedural mathematical (ability to mathematical reasoning; solving mathematical problems; mathematical modeling; the use of mathematical concepts; the use of symbolic, formal and technical elements of mathematics; the ability to use mathematics in communication) and total (reproduction; depending on the installation; synthesis and reflection) competencies. The course content of stochastics in training future economists in higher education in Germany is presented as an example of modules Statistics I (Descriptive statistics and probability theory) and Statistics II (Generalizing statistics). Analysis of programs on stochastic training of future economists in Germany showed that in addition to the usual Ukrainian higher educational establishments’ topics covered throughout the course «Probability Theory and Mathematical Statistics», considerable attention is paid to the study of the theory of indexed data, regression, and time series analysis. It is also highlighted the fact that a large amount of instructional time allotted for practical stochastic training both in school and in higher education institutions. Educational material is given at a high level of visualization, designed to illustrate the theoretical material, to facilitate its perception, to identify the submission of experimental data and so on. Considerable attention is paid to the use of computer software packages that can be used during the analysis of stochastic processes and phenomena. In our opinion, this methodological approach contributes to a higher level of formation of competences aimed at the ability to deal with the significant influence of the random factors effectively and professionally. Therefore, native scientists need to pay attention to the achievements of the approaches that will be aimed at strengthening the practical component of the stochastic training of future economists

Erigeron bonariensis, erigeron canadensis, and erigeron sumatrensis

The global human population is expected to reach 8-10 billion by 2050. According to the United Nations, this expansion in population is expected to increase food demands by double the current demand by 2050. Consequently, existing food production systems will come under significant strain. Exacerbating this food production problem is that agronomic weed species across the globe are already causing significant impacts on essential grain yields. Over the past decades, to address weed infestations, farmers have been using range of herbicides. However, overuse of these chemicals has resulted in many weed species mutating to a more resistant form. To implement a successful integrated weed management approach in the future, it will be essential to document the changes in ecology and biology of significant weed species. This chapter focuses on the three most globally significant weeds: Erigeron bonariensis, Erigeron canadensis, and Erigeron sumatrensis, summarizing their current global distribution, seed ecology, impacts, control strategies, as well as current herbicide resistance. These three species are causing significant impacts on important agricultural products including corn, soybean, cotton, wheat, chickpea, sorghum, orchards, and vineyards. Addressing the problem of high levels of herbicide resistance within the Erigeron species has been attempted through various solutions, including novel herbicide mixtures and application timing. Targeting these species in their earlier growth stage with herbicide combinations can greatly improve the success of integrated treatments, broadening the options for suitable approaches such as the use of zero or no-till systems. Given that, these species have innate traits including (1) high seed production, (2) low levels of seed dormancy, (3) high emergence rates, (4) efficient seed dispersal mechanisms, and (5) a highly competitive nature. These advantages, coupled with their ability to withstand a range of climatic conditions and their increasing herbicide-resistant biotypes, make them a serious agricultural weed species across the globe. In this chapter, we have synthesized the characteristic biological features and the effectiveness of various control options. Very limited information is available on the ecology and biology of E. sumatrensis. We have, nevertheless, harvested a significant amount of useful information which may assist farmers to effectively develop integrated agricultural management practices to reduce the impacts of these three species in their productive lands. © 2021 Elsevier Inc. All rights reserved

Factors effecting the germination and emergence of a rangeland weed European heliotrope (Heliotropium europaeum L.)

European heliotrope (Heliotropium europaeum L.) is an important weed in semiarid and arid Australia, due to its toxicity to livestock and its ability to out-compete crops for water and soil nutrients. It is an ephemeral species populations appear in high densities when conditions are favourable, but seeds remain dormant in the soil seedbank for extended periods of time. This study aimed to identify environmental factors that promoted the germination of this weed and factors that de-vitalise seeds. Seeds were collected from the Australian semiarid zone, at Nanya Research Station, New South Wales. The effects on seed germination and seedling emergence of H. europaeum of alternating temperature, photoperiod, drought, salinity, pH range, heat shock combined with smoke exposure, and burial depth were investigated. The highest germination rate was observed under the highest temperature regime, 30/20°C, under a photoperiod of 12 h light and 12 h dark. The weed germinated under moderate osmotic stress, but the highest germination occurred in the control treatment (no osmotic stress). The effect of salinity and pH on percentage germination was not significant. The effect of the heat shock and smoke treatment significantly reduced seed germination, with germination inhibited when seeds were exposed to 100°C for 3 min. Burial depth had a significant effect on seedling emergence, with a burial depth of 0.5 cm reducing the germination b

Factors affecting seed germination of feather fingergrass (Chloris virgata)

Laboratory experiments were carried out to determine the effect of several environmental factors on seed germination of feather fingergrass, one of the most significant emerging weeds in warm regions of the world. Seed germination occurred over a broad range of temperatures (17/7, 25/10, and 30/20 C), but germination being highest at alternating temperatures of 30/20 C under both 12 h light/12 h dark and 24 h dark conditions. Although seed germination was favored by light, some seeds were capable of germinating in the dark. Increasing salt stress decreased seed germination until complete inhibition was reached at 250-mM sodium chloride. Germination decreased from 64 to 0.7% as osmotic potential decreased from 0 to -0.4 MPa, and was completely inhibited at -0.6 MPa. Higher seed germination (>73%) was observed in the range of pH 6.4 to 8 than the other tested pH levels. Heat shock had a significant effect on seed germination. Germination of seeds placed at 130 C for 5 min was completely inhibited for both dry and presoaked seeds. The results of this study will help to develop protocols for managing feather fingergrass, and to thus avoid its establishment as a troublesome weed in economically important cropping regions