In recent decades, invasive willows and poplars (Salicaceae) have built dense floodplain forests along most of the rivers in Patagonia, Argentina. These invasion processes may affect Salix humboldtiana as the only native floodplain tree species in this region. It is assumed, that the property to reproduce vegetatively can play an important role in the establishment of invasive species in their new range. Thus, in order to contribute to a better understanding of willow and poplar invasions in riparian systems and to assess the potential impacts on S. humboldtiana the vegetative reproduction capacities of native and invasive Salicaceae were analysed. In a greenhouse experiment, we studied cutting survival and growth performance of the three most dominant invasive Salicaceae of the Patagonian Río Negro region (two Salix hybrids and Populus spec.), as well as S. humboldtiana, taking into account three different moisture and two different soil conditions. In a subsequent experiment, the shoot and root biomass of cuttings from the former experiment were removed and the bare cuttings were replanted to test their ability to re-sprout. The two invasive willow hybrids performed much better than S. humboldtiana and Populus spec. under all treatment combinations and tended to re-sprout more successfully after repeated biomass loss. Taking into account the ecology of vegetative and generative recruits of floodplain willows...
Magnetic resonance spectroscopy (MRS) is a non-invasive technique to detect metabolites within the normal and tumoral tissues. The ability of MRS to diagnose areas of high metabolic activity linked to tumor cell proliferation is particularly useful for radiotherapy treatment planning because of better gross tumor volume (GTV) delineation. The GTV may be targeted with higher radiation dose, potentially improving local control without excessive irradiation to the normal adjacent tissues. Prostate cancer and glioblastoma multiforme (GBM) are two tumor models that are associated with a heterogeneous tumor distribution. Preliminary studies suggest that the integration of MRS into radiotherapy planning for these tumors is feasible and safe. Image-guided radiotherapy (IGRT) by virtue of daily tumor imaging and steep dose gradient may allow for tumor dose escalation with the simultaneous integrated boost technique (SIB) and potentially decrease the complications rates in patients with GBM and prostate cancers.
Clonality is a common characteristic of successful invasive species, but general principles underpinning the success of clonal invaders are not established. A number of mechanisms could contribute to invasion success including clones with broad tolerances and preferences, specialist clones and adaptation in situ. The majority of studies to date have been of plants and some invertebrate parthenogens, particularly aphids, and have not necessarily caught invasion at very early stages. Here we describe the early stages of an invasion by a Northern Hemisphere Hymenopteran model in three different land masses in the Southern Hemisphere. Nematus oligospilus Förster (Hymenoptera: Tenthredinidae), a sawfly feeding on willows (Salix spp.), was recently introduced to the Southern Hemisphere where it has become invasive and is strictly parthenogenetic. In this study, the number of N. oligospilus clones, their distribution in the landscape and on different willow hosts in South Africa, New Zealand and Australia were assessed using 25 microsatellite markers. Evidence is presented for the presence of two very common and widespread multilocus genotypes (MLGs) or ‘superclones’ dominating in the three countries. Rarer MLGs were closely related to the most widespread superclone; it is plausible that all N. oligospilus individuals were derived from a single clone. A few initial introductions to Australia and New Zealand seemed to have occurred. Our results point towards a separate introduction in Western Australia...
The main purpose of this study was to determine typical concentrations of heavy metals (HM) in wood from willows and poplars, in order to test the feasibility of phytoscreening and phytoextraction of HM. Samples were taken from one strongly, one moderately, and one slightly polluted site and from three reference sites. Wood from both tree species had similar background concentrations at 0.5 mg kg−1 for cadmium (Cd), 1.6 mg kg−1 for copper (Cu), 0.3 mg kg−1 for nickel (Ni), and 25 mg kg−1 for zinc (Zn). Concentrations of chromium (Cr) and lead (Pb) were below or close to detection limit. Concentrations in wood from the highly polluted site were significantly elevated, compared to references, in particular for willow. The conclusion from these results is that tree coring could be used successfully to identify strongly heavy metal-polluted soil for Cd, Cu, Ni, Zn, and that willow trees were superior to poplars, except when screening for Ni. Phytoextraction of HMs was quantified from measured concentration in wood at the most polluted site. Extraction efficiencies were best for willows and Cd, but below 0.5 % over 10 years, and below 1 ‰ in 10 years for all other HMs.
This thesis explores the hydrological factors that may contribute to the observed distribution
patterns of invasive willows (Salix) and native trees (Eucalyptus camaldulensis, E. largiflorens and
Acacia stenophylla) along the Lower River Murray (LRM) in southern Australia. An initial survey,
establishing the diversity and flowering biology of Salix taxa was carried out to ascertain the extent
of invasion, and the likelihood of hybridisation, which may accelerate invasion. S. babylonica,
S. fragilis, S. × chrysochoma and S. × rubens occur in the study region, each represented by a single gender. None were present on floodplains, but the most dominant taxon, S. babylonica,
occurred along the entire length of the main channel. No seed or seedlings were observed; hence
reproduction is likely to be asexual.
More detailed survey work was then carried out to characterise the distribution patterns of the
dominant S. babylonica and co-occurring natives (Eucalyptus camaldulensis, E. largiflorens and
Acacia stenophylla) along a hydrologic gradient produced by the extensive weir system in the
LRM. In weir pools, variation in daily water levels of weir pools is low (± 0.1 m) immediately
upstream of the weir...
Two global issues are brought together in this thesis to address a facet of both water resource and weed management in Australia. Water resource security is of global concern as human need for water increases and uncertainty in future water availability associated with climate change continues to evolve, particularly in arid and semi-arid regions. Furthermore, invasive species modify landscapes around the globe in response to anthropogenic ecosystem alterations, with significant impacts within aquatic systems. Water savings projects are under investigation in Australia in response to resource over-allocation and impacts of a prolonged drought from 1997 to 2009 (‘The Millennium Drought’). An overarching aim of such investigations is to return water to the environment to meet future consumptive and environmental water requirements. In southeast Australia, invasive willows (Salicaceae: Salix spp.) have been identified as naturalized weeds which invade stream beds. In natural systems, stream beds are generally unoccupied and willow establishment increases total riparian leaf area and therefore total evaporative losses. Anecdotal evidence suggested water could be returned to creeks and streams if willows were removed, creating water saving. Strategies exist within State and Commonwealth agencies in Australia to monitor willow invasion...