A field experiment from 2003 to 2005 at two sites examined the impacts of forage species and legume proportion on forage sward production. Grasses generally established rapidly and out-yielded swards high in legume content, although legumes did improve forage quality. Alfalfa was retained at greater relative biomass in mixed swards than swards containing clover. Legume persistence also varied depending on neighbouring grass species. A greenhouse study examined competitive interactions between Canada thistle (a common pasture weed), white clover and Kentucky bluegrass during establishment. Although thistle was most susceptible to intra-specific competition, and strongly affected forage yield, the latter also influenced weed biomass. Competitiveness of forages depended directly on soil medium, emphasizing the importance of abiotic factors on vegetation dynamics in mixed swards. / Rangeland and Wildlife Resources

No description available.

Las proteasas aspárticas típicas de plantas (o tipo pepsina) han sido escasamente estudiadas en comparación con sus contrapartes de origen no vegetal. Una excepción a esta afirmación, lo constituyen las cardosinas (Cynara cardunculus) usadas en la manufactura de quesos y la fitepsina (Hordeum vulgare), que al día de hoy continúa siendo una de las pocas proteasas de esta clase caracterizada estructuralmente y por tanto, el modelo utilizado en esta área. Una de las principales razones por las cuales las PAs de plantas no han sido objeto de mayor cantidad de estudios es su escasa abundancia natural. Ésto resulta especialmente cierto en el caso de sus precursores, los cuales contienen el llamativo dominio PSI (inserto específico de plantas), único entre las PAs. En un intento por identificar nuevas fuentes vegetales de PAs típicas, extractos de flores de varias especies pertenecientes a la familia Asteraceae que crecen en Argentina fueron probados en ensayos de coagulación de leche. Una de las especies que mostró esta capacidad coagulante sugiriendo por tanto la presencia de PAs, fue Cirsium vulgare -comúnmente conocido como cardo negro y considerada una maleza en los campos de nuestra región. Fundamentalmente debido a su amplia disponibilidad y a la ausencia de estudios reportados sobre sus PAs, se decidió emplear esta especie de la familia Asteraceae como material vegetal. En este contexto, el presente trabajo intenta generar un aporte al conocimiento de las PAs de origen vegetal mediante el estudio de procirsina, una proenzima de C. vulgare perteneciente a la familia A1, y del dominio PSI contenido en su secuencia.

The aim of this diploma thesis "The determination of the production of seeds and their germination for selected species from the weedy family Asteraceae" is to find out the production of seeds and their germination of two selected weedy species from the family Asteraceae, depending on the location. The following were selected: Creeping Thistle (Cirsium arvense) and Wormwood (Artemisia vulgaris). Seed collection was done at seven locations with different habitat conditions (unmaintained hayfield, recultivated rubbish, garden, grass vegetation with grazing breeding of cattle, permanent grass vegetation, grasslands on arable land, forest land, other road, other area). After reviewing the available literature is discussed the biology and control of weeds and their significance. Furthermore is also characterized the family Asteraceae and selected representatives of this family . Subsequently is characterized the territory of interest. In addition is discussed the problematics of germination and seed production for Creeping Thistle (Cirsium arvense) and Wormwood (Artemisia vulgaris) depending on their habitats. The overall average HTS of Wormwood was 0.08 g, the average germination was 79%. The total average seed production of Creeping Thistle was 1 299 seeds, one plant had an average of 23 flowers and one flower had 51 seeds. Due to the very low number of sprouted seeds of this weed the germination parameter cannot be statistically evaluated.

Invasive plants can alter pollination dynamics in invaded communities by disrupting patterns of pollinator visitation, pollen transfer dynamics (conspecific [CP] and heterospecific [HP]), and reproductive success. The direction of invasive effects (competitive, neutral, and facilitative) may be partially determined by spatial scale and species’ floral traits. Here, we investigated pollinator visitation, CP and HP receipt, and pollen tube growth for species in a C. arvense present community and non-present community at two scales. At the community-level, the effect of C. arvense on pollinator visitation varied among species. Floral symmetry seemed to explain this variation. At the floral neighborhood-level, we found competitive effects for pollinator visits and mixed effects on CP deposition. The overall structure of plant-plant HP deposition networks was slightly altered. We observed lower average centrality across shared species in the C. arvense present community suggesting C. arvense had subverted their roles as pollen donors.

No description available.

Classical biocontrol systems are sometimes treated as an exercise in community assembly. As such, they include multiple species interactions. This thesis explores multi-species aspects in classical weed biocontrol, using thistles as a case study. The abundance, phenology and impact of three biocontrol agents were followed on their target host, Carduus nutans L. and are described, for the first time in New Zealand for two of them (Urophora solstitialis L. and Trichosirocalus horridus sensu (Panzer)). Composition in New Zealand of the recently revised Trichosirocalus weevil species complex was surveyed nation-wide. One species only was found, albeit exhibiting a wider host range than anticipated from the published revision. Interspecific interactions and individual and combined effect of multiple biocontrol agents on C. nutans were tested in cage setups; the effect on the weed population was then estimated by manipulations of an existing matrix population model for this weed in New Zealand. The potentially better seed predator (U. solstitialis) was outcompeted by the worse seed predator (Rhinocyllus conicus (Froehlich)) which has similar niche preference. Urophora solstitialis was also adversely impacted by the crown-root feeder (T. horridus). Trichosirocalus horridus affected C. nutans survival, even at the medium density used, and significantly reduced potential seed production by 33%; in field densities, T. horridus is likely to affect C. nutans even more. Urophora solstitialis was estimated to destroy about 28% of the remaining seed in the absence of the other agents, and about 17% in the presence of T. horridus. The estimated combined effect of T. horridus and U. solstitalis on C. nutans population growth rate was greater than the effect of either agent alone. In the face of growing weed invasions, multiple thistle species were used to test ‘multi-targeting’ as a novel approach to target groups of ‘sleeper weeds’. Both in a field experiment and in a field survey, the seed predator R. conicus was found to attack and damage some ‘non-target’ thistle species more in the presence of the target species (C. nutans) than in its absence; however, levels of attack on non-target species were always modest. The ultimate goal of biocontrol is to reduce weed populations. A field survey revealed that current population densities of multiple thistle species in Canterbury are not obviously lower than in the mid 1980s, when only R. conicus was present. This may be because successful biocontrol has reduced the management input required to maintain the same thistle density.

Classical biocontrol systems are sometimes treated as an exercise in community assembly. As such, they include multiple species interactions. This thesis explores multi-species aspects in classical weed biocontrol, using thistles as a case study. The abundance, phenology and impact of three biocontrol agents were followed on their target host, Carduus nutans L. and are described, for the first time in New Zealand for two of them (Urophora solstitialis L. and Trichosirocalus horridus sensu (Panzer)). Composition in New Zealand of the recently revised Trichosirocalus weevil species complex was surveyed nation-wide. One species only was found, albeit exhibiting a wider host range than anticipated from the published revision. Interspecific interactions and individual and combined effect of multiple biocontrol agents on C. nutans were tested in cage setups; the effect on the weed population was then estimated by manipulations of an existing matrix population model for this weed in New Zealand. The potentially better seed predator (U. solstitialis) was outcompeted by the worse seed predator (Rhinocyllus conicus (Froehlich)) which has similar niche preference. Urophora solstitialis was also adversely impacted by the crown-root feeder (T. horridus). Trichosirocalus horridus affected C. nutans survival, even at the medium density used, and significantly reduced potential seed production by 33%; in field densities, T. horridus is likely to affect C. nutans even more. Urophora solstitialis was estimated to destroy about 28% of the remaining seed in the absence of the other agents, and about 17% in the presence of T. horridus. The estimated combined effect of T. horridus and U. solstitalis on C. nutans population growth rate was greater than the effect of either agent alone. In the face of growing weed invasions, multiple thistle species were used to test ‘multi-targeting’ as a novel approach to target groups of ‘sleeper weeds’. Both in a field experiment and in a field survey, the seed predator R. conicus was found to attack and damage some ‘non-target’ thistle species more in the presence of the target species (C. nutans) than in its absence; however, levels of attack on non-target species were always modest. The ultimate goal of biocontrol is to reduce weed populations. A field survey revealed that current population densities of multiple thistle species in Canterbury are not obviously lower than in the mid 1980s, when only R. conicus was present. This may be because successful biocontrol has reduced the management input required to maintain the same thistle density.

No description available.

<div>Grand Sable Dunes, as a perched dune field on the shore of Lake Superior, is a sensitive</div><div>ecosystem subject to continual disturbance. Repeated natural disturbances necessitate specialized</div><div>plant communities to develop. There were two objectives of my research in this system that are</div><div>treated in separate chapters. They include: 1) the quantification of successional changes in the</div><div>plant community over time, and the identification of population demography changes for rare</div><div>species within the dunes and 2) the evaluation of evaluate in pollinator species for two plants</div><div>Hieracium caespitosum (Yellow Hawkweed) and Lithospermum caroliniense (Carolina</div><div>Puccoon).</div><div>For the first objective, target plant community composition and structures (i.e. richness,</div><div>diversity) were quantified in 2011 and 2018 across Grand Sable Dunes in 1 m² quadrats.</div><div>Additionally, two relatively rare plant species (Cirsium pitcheri and Tanacetum bipinnatum)</div><div>were selected to quantify demographic (i.e. flowering, non-flowering) patterns and changes over</div><div>time. Samples for C. pitcheri and T. bipinnatum were acquired via circle-plots 2.5 m in diameter.</div><div>Population comparisons between 2011 and 2018 illustrate minimal change in community</div><div>structure (richness and diversity). Composition increased slightly with eight species occurring in</div><div>2018, but not 2011. Additionally, community similarity was high (~78%) between the two years.</div><div>C. pitcheri occurrence was inversely related to presence of other species. Plant community</div><div>composition in eastern and western survey zones within the dunes appear to be diverging. Minor</div><div>changes in the plant community composition and structures indicate successional changes have</div><div>occurred, but without major disturbance. This divergence in community composition may be</div><div>related to weather related incidents associated with Lake Superior disturbance potential.</div><div>The secondary objective concerns pollinator species on two similar plant species found in</div><div>the Grand Sable Dunes. Individuals of H. caespitosum and L. caroliniense were observed and all</div><div>floral visitors were identified to family. The majority of arthropod families were observed</div><div>10</div><div>visiting both H. caespitosum and L. caroliniense, with an absence of typically important families</div><div>(e.g. Apidae, Bombiliidae). Halictidae, Muscidae and Syrphidae were the most common visitors,</div><div>with L. caroliniense attracting far more Muscidae than their H. caespitosum competitors.</div><div>Overlap in visitors for both species was observed, which may lead to decreased reproduction in</div><div>L. caroliniense.</div>