Soil P availability limits legume persistence and distribution in the fynbos of the Cape Floristic Region

Includes abstract.Includes bibliographical references (leaves 64-83).Legumes are unable to persist through post-fire succession in fynbos vegetation of the CFR unlike species in families such as Proteaceae and Restionaceae. The majority of fynbos legumes are seeders which tend to be shorter-lived than co-occurring resprouters. Seeders are likely to have a higher nutrient requirement than resprouters as they tend to invest more biomass- above ground, grow faster and produce more seed. In the oligo-trophic soils occupied by fynbos, symbiotic N2-fixation enables legumes to overcome low N availability but not low P availability. I hypothesized that: legumes are less effective at acquiring P from sparingly soluble sources compared with members of Proteaceae and Restionaceae ; legume seeders occupy soils with a higher nutrient status than resprouters. P-acquisition strategies of legumes and non-legumes were assessed

Single-equation Errors-in-variables Estimation Of Rational Expectations Models

This thesis is concerned with the single-equation errors-in-variables estimation of rational expectations models. More specifically, we propose some new single-equation errors-in-variables estimators for a certain class of models which occur frequently in the macroeconomics literature. The asymptotic properties of these new estimators are derived and a Monte Carlo study is used to investigate the small sample performance of these new estimators relative to that of the existing errors-in-variables estimators and the single-equation substitution method estimator.;This Monte Carlo study is particularly useful in providing, as a by-product, the first small sample comparison of certain estimators used widely in the literature. An important finding is that, to the extent to which we can generalise on the basis of our limited experiments, there are many instances in which statistical inference associated with all of these estimation techniques can be highly misleading. In addition, we illustrate the use of some new non-parametric density estimation techniques in the summary of the Monte Carlo results.;The thesis also provides a useful survey of the literature on the solution of rational expectations models together with a reasonably comprehensive survey of estimation methods

Determinants of blackwaters in the South Western Cape

Blackwater rivers and lakelets are a common feature of the landscape in the South Western Cape. Contrastingly, white rivers can also be found in the region. Key to the colour of blackwaters is the increased presence of dissolved organic carbon. The vegetation of the regions is known to posses' large amounts of polyphenols and potentially low microbial decomposition. Therefore, are the plant-soil dynamics a possible answer to variation in river colour? To answer this, the chemical correlates of rivers in the region, along with the in vitro leaching of the fynbos vegetation compared to other types and the effects of nutrient fertilisation on microbial activity in soil were determined. The results revealed that organic carbon, Fe and pH are significantly correlated with blackwaters. The Fe in the water appears to be bound to humic compounds. Fynbos vegetation is able to produce greater concentrations of polyphenol leachates (315 mg/l humic acid) compared to savanna species (246 mg/ humic acid) over a four-day period. P fertilisations increased the concentrations of humic acids from 30 mg/1 to 200 mg/l in some soils through their affinity to bind with humic compounds. The N fertilisations moderately increased the humic acid concentrations and in some cases lowered the concentration by 10 mg/l, indicating that it provided a nutrient source to the microbes for carbon breakdown. The interactions between humic compounds, nutrients and Fe are key to the formation of blackwaters in the region. Attached to this is the limited decomposition that takes place due to nutrient limitations. Therefore, the interactions between the carbon leached from the vegetation and below ground activities are determinants of water colour in the South Western Cape

Land use in rural New Zealand: spatial land use, land-use change, and model validation

Abstract Land is an important social and economic resource. Knowing the spatial distribution of land use and the expected location of future land-use change is important to inform decision makers. This paper documents and validates the baseline land-use maps and the algorithm for spatial land-use change incorporated in the Land Use in Rural New Zealand model (LURNZ). At the time of writing, LURNZ is the only national-level land-use model of New Zealand. While developed for New Zealand, the model provides an intuitive algorithm that would be straightforward to apply to different locations and at different spatial resolutions. LURNZ is based on a heuristic model of dynamic land-use optimisation with conversion costs. It allocates land-use changes to each pixel using a combination of pixel probabilities in a deterministic algorithm and calibration to national-level changes. We simulate out of sample and compare to observed data. As a result of the model construction, we underestimate the “churn” in land use. We demonstrate that the algorithm assigns changes in land use to pixels that are similar in quality to the pixels where land-use changes are observed to occur. We also show that there is a strong positive relationship between observed territorial-authority-level dairy changes and simulated changes in dairy area

How to improve the risk cultures of financial institutions

Following the 2008 global financial crisis, official inquires, parliamentary reports, and the media frequently focused their attention on the flawed risk cultures of financial institutions. In their research, Michael Power, Simon Ashby, and Tommaso Palermo investigated how these risk cultures operate, evolve, and can be improved

Ovarian and cervical cancer awareness: development of two validated measurement tools.

The aim of the study was to develop and validate measures of awareness of symptoms and risk factors for ovarian and cervical cancer (Ovarian and Cervical Cancer Awareness Measures)

Metagenetic analysis of patterns of distribution and diversity of marine meiobenthic eukaryotes

AimMeiofaunal communities that inhabit the marine benthos offer unique opportunities to simultaneously study the macroecology of numerous phyla that exhibit different life-history strategies. Here, we ask: (1) if the macroecology of meiobenthic communities is explained mainly by dispersal constraints or by environmental conditions; and (2) if levels of meiofaunal diversity surpass existing estimates based on morphological taxonomy. LocationUK and mainland European coast. MethodsNext-generation sequencing techniques (NGS; Roche 454 FLX platform) using 18S nuclear small subunit ribosomal DNA (rDNA) gene. Pyrosequences were analysed using AmpliconNoise followed by chimera removal using Perseus. ResultsRarefaction curves revealed that sampling saturation was only reached at 15% of sites, highlighting that the bulk of meiofaunal diversity is yet to be discovered. Overall, 1353 OTUs were recovered and assigned to 23 different phyla. The majority of sampled sites had c. 60-70 unique operational taxonomic units (OTUs) per site, indicating high levels of beta diversity. The environmental parameters that best explained community structure were seawater temperature, geographical distance and sediment size, but most of the variability (R-2=70%-80%) remains unexplained. Main conclusionsHigh percentages of endemic OTUs suggest that meiobenthic community composition is partly niche-driven, as observed in larger organisms, but also shares macroecological features of microorganisms by showing high levels of cosmopolitanism (albeit on a much smaller scale). Meiobenthic communities exhibited patterns of isolation by distance as well as associations between niche, latitude and temperature, indicating that meiobenthic communities result from a combination of niche assembly and dispersal processes. Conversely, isolation-by-distance patterns were not identified in the featured protists, suggesting that animals and protists adhere to radically different macroecological processes, linked to life-history strategies.Natural Environment Research Council (NERC) [NE/E001505/1, NE/F001266/1, MGF-167]; Portuguese Foundation for Science and Technology (FCT) [SFRH/BD/27413/2006, SFRH/BPD/80447/2014]; EPSRC [EP/H003851/1]; BBSRC CASE studentship; Unilever; Biotechnology and Biological Sciences Research Council [987347]; Engineering and Physical Sciences Research Council [EP/H003851/1]; Natural Environment Research Council [NE/F001290/1, NE/F001266/1, NE/E001505/1, NBAF010002]info:eu-repo/semantics/publishedVersio

Self-consistent massive disks in triaxial dark matter halos

Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to calculate the equilibrium configuration of such a disk in the combined disk-halo potential, which is based on the method of Jog (2000) but accounts for the radial variation in both the halo potential and the disk ellipticity. This crucial ingredient results in qualitatively different behavior of the disk: the disk circularizes the potential at small radii, even for a reasonably low disk mass. This effect has important implications for proposals to reconcile cuspy halo density profiles with low surface brightness galaxy rotation curves using halo triaxiality. The disk ellipticities in our models are consistent with observational estimates based on two-dimensional velocity fields and isophotal axis ratios.Comment: ApJ, in pres

Assessing awareness of colorectal cancer symptoms: Measure development and results from a population survey in the UK

Background: This paper describes the development of a Cancer Awareness Measure for colorectal (CRC) cancer (Bowel/Colorectal CAM(a)) (study 1) and presents key results from a population-representative survey using the measure (study 2).MethodsStudy 1: Items were taken from the literature and reviewed by expert groups. A series of three validation studies assessed reliability and validity of the measure. To establish test-retest reliability, 49 people over 50 years of age completed the Bowel/Colorectal CAM on two occasions (range 9-14 days, mean 13.5 days). Construct validity was assessed by comparing responses from bowel cancer experts (n = 16) and the lay public (n = 35). Lastly, a brief intervention study tested sensitivity to change with participants (n = 70) randomly allocated to be given a control leaflet or an intervention leaflet and their responses were compared. Study 2: 1520 respondents completed the Bowel/Colorectal CAM in a population survey carried out by TNS-British Market Research Bureau International (TNS-BMRB) in March 2010.ResultsStudy 1: Internal reliability (Cronbach's alpha = 0.84) was high. Test-retest reliability was over r = 0.7 for warning signs, risk factors and age people are first invited for screening, but lower (between 0.6 and 0.7) for other items (lifetime risk, awareness of bowel cancer screening, age at risk). Bowel cancer experts achieved higher scores than equally educated controls (54.7 [4.3] vs. 42.9 [5.7]; P < 0.001) demonstrating the measure has construct validity and intervention participants showed higher knowledge than controls (51.4 [5.9] vs. 42.9 [5.7]; P < 0.001) suggesting the measure is sensitive to change. Study 2: Respondents recalled on average, one CRC sign and one risk factor. There was particularly low prompted awareness of the signs 'lump in the abdomen' (64%) and 'tiredness' (50%) and several lifestyle risk factors for CRC, e. g. exercise (37%). Respondents from more affluent groups had consistently higher knowledge of signs and risk factors compared to those from more deprived groups.Conclusions: The Bowel/Colorectal CAM meets accepted psychometric criteria for reliability and construct validity and should therefore provide a useful tool for assessment of CRC awareness. The population survey revealed low awareness of several CRC signs and risk factors and emphasises the importance of continuing public education, particularly about the link between lifestyle behaviours and CRC