105 research outputs found
Long-term surveillance of Phytophthora cinnamomi reveals no evidence of increased detections and new insights for monitoring and management
No full textContext
Phytophthora cinnamomi Rands is an introduced soil-borne pathogen that causes population decline in susceptible species and changes native vegetation compositions. Land managers require information about changing disease incidence, predisposing site factors and potential efficiencies in field identification of the disease. Previous sampling for P. cinnamomi in southern Sydney conservation reserves has provided a framework to monitor pathogen incidence.
Aims
We specifically asked: (1) Is the incidence of P. cinnamomi disease intensifying, decreasing or stable? (2) Is visual assessment of disease symptoms at the community or sentinel species level a good predictor of positive P. cinnamomi laboratory assays? (3) Is the incidence of P. cinnamomi related to access, vegetation type, human visitation or landscape position?
Methods
We assembled data from historic surveys in Dharawal Reserves in 2008 (n = 26) and 2014 (n = 110), and undertook additional surveys in 2022 (n = 110). We supplemented detections in 2008 with 2006–2008 records from other southern Sydney conservation reserves (n = 147). We used laboratory detection results, field observations of plant symptoms and environmental data to assess trends.
Key results
We did not find evidence of increased pathogen incidence over time; however, detection was spatially and temporally variable among sites. Proximity to waterways appeared to increase the likelihood of P. cinnamomi presence. We found differences between visual field assessment of disease expression and laboratory assay of pathogen detection. We observed marginal improvement in detection agreement when we subsetted the data to sites that explicitly identified Xanthorrhoea sp. as potential host species. A sample size analysis indicated that considerable increase in sampling effort would be required to detect consequential changes in the long-term P. cinnamomi status.
Conclusions
Landscape-scale monitoring of P. cinnamomi incidence requires greater sampling intensity and duration to support reliable inferences about trends. Locally focused management and monitoring efforts that consider susceptible sentinel species dynamics may inform the protection of specific assets at risk from infection by P. cinnamomi
Invasive shrub re-establishment following management has contrasting effects on biodiversity
No full textEffective control of an invasive species is frequently used to infer positive outcomes for the broader ecosystem. In many situations, whether the removal of an invasive plant is of net benefit to biodiversity is poorly assessed. We undertook a 10-year study on the effects of invasive shrub management (bitou bush, Chrysanthemoides monilifera ssp. rotundata) on native flora and fauna in a eucalypt forest in south-eastern Australia. Bitou bush eradication is a management priority, yet the optimal control regime (combination of herbicide spray and fire) is difficult to implement, meaning managed sites have complex management histories that vary in effectiveness of control. Here we test the long-term response of common biodiversity indicators (species richness, abundance and diversity of native plants, birds, herpetofauna and small mammals) to both the management, and the post-management status of bitou bush (% cover). While average bitou bush cover decreased with management, bitou bush consistently occurred at around half of our managed sites despite control efforts. The relationship between biodiversity and bitou bush cover following management differed from positive, neutral or negative among species groups and indicators. Native plant cover was lower under higher levels of bitou bush cover, but the abundance of birds and small mammals were positively related to bitou bush cover. Evidence suggests that the successful control of an invader may not necessarily result in beneficial outcomes for all components of biodiversity.</p
Race and Social Equity
No full textIn this compelling book the author contends that social equity--specifically racial equity--is a nervous area of government. Over the course of history, this nervousness has stifled many individuals and organizations, thus leading to an inability to seriously advance the reduction of racial inequities in government. The author asserts that until this nervousness is effectively managed, public administration social equity efforts designed to reduce racial inequities cannot realize their full potential
A study of the causes of daily non-attendance in the Negro schools of three Mississippi counties, 1939
No full text
The development of the spacesuit
No full textAn Author event presented by the Friends of the University of Adelaide Library. Held 30 October 2014, Barr Smith Library, University of Adelaide
Native community responses to alien grass invasion: role of landscape and native plant functional traits in mediating invader impacts
No full textIt is well-known that alien plant invaders significantly threaten the diversity and ecological function of native plant communities. Recent research has shown that impacts of invasion are dependent upon invader attributes, yet it is poorly known whether landscape context and functional attributes of resident native plants also mediate invader impacts on the recipient community. I used the model system of invasion by the alien, stoloniferous grass Stenotaphrum secundatum (Walter) Kuntze into an endangered and highly-fragmented coastal swamp forest community along the southern coastline of New South Wales, Australia, to determine whether impacts of invasion are dependent upon extrinsic landscape processes, such as anthropogenic habitat modification and nutrient enrichment, and/or functional attributes of the resident native plants. Knowledge of this will improve our capacity to predict the types of landscapes and community contexts most likely to be impacted by alien plant invasion. I first used a spatially-extensive field survey of S. secundatum-invaded and noninvaded forest sites to examine native plant community response to invasion across a gradient of anthropogenic landscape modification. I also extracted soil and used a seedling emergence experiment to examine impacts of invasion on the seed bank community. At each site I measured local disturbance and environmental attributes of both the community (e.g. fire severity, litter abundance, canopy openness, vegetation structure) and adjacent landscape matrix (e.g. cover of forest, urban and agricultural land). I predicted that invasion and landscape modification would synergistically impact the forest community and its seed bank, such that the rate of native plant species loss in response to invasion would increase with the extent of urbanisation in the matrix. Invasion by S. secundatum was associated with substantial reductions (~85%) in native species richness, density of recruits and altered community compositions within the standing vegetation. Invasion caused only moderate reductions (~35%), however, in seed bank species richness. Importantly, impacts of invasion on the seed bank were nonrandom and varied across functional groups. Native herb and graminoid species (which share similar growth forms and root morphologies with S. secundatum) as well as short distance and animal dispersed species had reduced species richness in invaded sites, whilst the number of woody and wind and water dispersed species were unaffected by invasion. Standing vegetation and seed bank species richness were unaffected by local disturbances and landscape context. Furthermore, anthropogenic landscape modification did not moderate the effects of invasion on the community, such that species losses in response to invasion were high regardless of the condition of the adjacent matrix. Invasion had no effect on soil nutrient concentrations but caused a two-fold increase in litter biomass, which may be the driver of native plant recruitment limitation. Next, in order to determine the likely mechanism by which S. secundatum invasion limits native plant recruitment, I intensively sampled the (1) abundance and frequency of occurrence, (2) reproductive effort (flowering) and output (fruit production) and (3) seed bank densities for three focal native plants from the invaded forest. Invasion reduced the biomass (but not likelihood of occurrence), flowering effort and reproductive output (~75%) of each species. However, invasion had no effect on the species’ seed bank densities, despite the substantial reduction in their reproductive output. Coupled with results from the community-scale seed bank study, this indicates that S. secundatum invasion disrupts native plant recruitment by limiting post-settlement emergence of propagules from the seed bank rather than their supply and storage at invaded sites. Finally, I contextualised these three correlative studies by performing a community-scale, invader-addition experiment. I tested wether impacts of invasion are dependent upon functional attributes of the resident native plants and/or anthropogenically-driven nutrient enrichment of the coastal forest. Experimental plots contained 18 species (drawn without replacement from a pool of 31 species) with either runner, tufted or woody growth forms. Species growth (% cover), reproductive output, soil temperature and light availability were monitored for two growing seasons in response to S. secundatum invasion and nutrient enrichment. Species richness, community composition, reproductive output, soil temperature and light penetration were unaffected by invasion and nutrient enrichment. Invasion reduced community productivity, but this effect was not moderated by nutrient availability. Furthermore, the impact of invasion on community productivity was non-random and driven only by reduced biomass of functionally-similar native runner species. My research has shown that impacts of invasive plants on native communities are non-random and strongly mediated by functional attributes of the resident native plants, rather than either landscape context or local community disturbances. My results support the hypothesis that native species functionally similar to invaders are more likely to be displaced from invaded communities than functionally dissimilar ones. The likely mechanism by which invasion disrupts native populations is post-settlement recruitment limitation from the seed bank. Management of invaded communities must consider differential impacts of invasion in the community and actively reintroduce native species, such as those with short distance modes of dispersal, which may be able to spontaneously regenerate following invader control
The optimum level of parent participation: A study of three intensity levels of parent involvement during three "Playtime is Science" units in three third-grade classes
No full textThe study describes the experience of introducing three intensity levels of parent participation in three third-grade classes for science instruction using Playtime is Science; an equity curriculum that utilizes parent participation. The study sought to determine the optimum level of participation by ascertaining the most influential aspect of involvement on proficiency scores and the most important aspect of involvement to participants.The levels of participation intensity were distinguished by: (1) the number of parents in the classroom; (2) the responsibilities of the parents; (3) the training received; and (4) the number of students with whom the parents worked. Involvement at each level would potentially manifest aspects of role modeling, lowered student-to-adult instructional ratio, and parent expertise to varying degrees. The three levels of participation were introduced during explorations in three Playtime is Science units following a rotation schedule.Student proficiency was assessed through scores on pre- and post-tests, journals, and discourse. ANCOVA was used to identify main and interaction effects of the independent variables (class, unit and level) on student proficiency taking into account existing differences in groups. Participant attitudes were assessed through journals and interviews. Observations of explorations triangulated findings and assessed participant interactions. Field notes, transcripts and photographs were coded according to the aspects of parent involvement.The results showed level of parent intensity of involvement had no affect on proficiency scores. Therefore, no aspect of parent involvement was determined to be the most influential. Participants felt that lowered instructional ratio and role modeling were the most important aspects of involvement. The level of involvement that utilized the lowest ratio and the most role modeling was level III, small group facilitators. Level III was recognized as the optimum level of participation in science instruction for this study.Although no level of involvement was significantly influential for student scores, there was a main effect for units, supporting the finding that teacher conceptions of science are more influential on student proficiency than parent participation at any level. The influence of teacher conceptions was unanticipated but is critical to consider when implementing any program or methodology to improve science instruction.Source: Dissertation Abstracts International, Volume: 61-11, Section: A, page: 4328.Advisors: Lynn Fox.Ph.D. American University 2000.Englis
Non‐interactive effects of plant invasion and landscape modification on native communities
No full textChapter 2 The Saturation of Racial Inequities in the United States
No full textIn this compelling book the author contends that social equity--specifically racial equity--is a nervous area of government. Over the course of history, this nervousness has stifled many individuals and organizations, thus leading to an inability to seriously advance the reduction of racial inequities in government. The author asserts that until this nervousness is effectively managed, public administration social equity efforts designed to reduce racial inequities cannot realize their full potential
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