Slow carbon and nutrient accumulation in trees established following fire exclusion in the southwestern United States.

Increasing tree density that followed fire exclusion after the 1880s in the southwestern United States may have also altered nutrient cycles and led to a carbon (C) sink that constitutes a significant component of the U.S. C budget. Yet, empirical data quantifying century-scale changes in C or nutrients due to fire exclusion are rare. We used tree-ring reconstructions of stand structure from five ponderosa pine-dominated sites from across northern Arizona to compare live tree C, nitrogen (N), and phosphorus (P) storage between the 1880s and 1990s. Live tree biomass in the 1990s contained up to three times more C, N, and P than in 1880s. However, the increase in C storage was smaller than values used in recent U.S. C budgets. Furthermore, trees that had established prior to the 1880s accounted for a large fraction (28-66%) of the C, N, and P stored in contemporary stands. Overall, our century-scale analysis revealed that forests of the 1880s were on a trajectory to accumulate C and nutrients in trees even in the absence of fire exclusion, either because growing conditions became more favorable after the 1880s or because forests in the 1880s included age or size cohorts poised for accelerated growth. These results may lead to a reduction in the C sink attributed to fire exclusion, and they refine our understanding of reference conditions for restoration management of fire-prone forests

Effective models of employment-based training

Evolving models of employment-based training (EBT) are responding to skill shortages and the need to develop technical skills at a level higher than a certificate III—the benchmark qualification level considered by many as the minimum for ensuring sustainable job outcomes (Stanwick 2004). This research explored a variety of current employment-based training models and proposed five enhancements for higher-level qualifications. These changes concentrate on maintaining a balance of learning experiences between educational institutions and the workplace. The project was based around case studies in process manufacturing and child care. Thirty-three individuals, representing employers, employees/apprentices, vocational education and training (VET) providers, industry bodies and training package developers were interviewed. The issues and views expressed by those interviewed from both industries were consistent with what was found in the literature review. Current models of employment-based training can usefully be grouped as: two forms of 'fast-tracking' options in a formal apprenticeship model, especially at certificate III level, to address immediate skills shortages. These are accelerated progression models (shorter durations linked to a truly competency-based approach) and intensive up-front training, followed by work-based learning to ensure immediate productivity of the learner in the workplace higher-level VET qualifications gained either through an apprenticeship or by undertaking a vocational course the design of new skill sets/qualifications at various levels of the Australian Qualifications Framework (AQF) alternative provisions for young people. Although these models continue to make a significant contribution to the skilling of the Australian workforce, their full potential is limited by certain persistent issues. These include inconsistent regulatory arrangements, non-compliance by employers and registered training organisations, poor audit processes, variations in the interpretation and practice of competency-based training, and wages and awards. These various factors mean poor completion rates and losses for individuals, employers, governments and other stakeholders. Recent changes in policy direction are attempting to address some of these issues and simultaneously increase interest and growth in the uptake of employment-based training. Any new models of employment-based training should address existing problems, as well as take into account the emerging needs of industry for skilled labour. The design of the models must also address an ageing workforce and allow flexible entry points for all age groups. Furthermore, future employment-based training models also need to keep pace with how work is organised in an environment characterised by increased competition, outsourcing, casualisation and an emphasis on specialisation and innovation. What is becoming apparent is the need for a compendium of models, rather than a 'one size fits all' approach

CCD speed-noise optimization at 1 MHz

The Zwicky Transient Facility (ZTF)[1] is a CCD mosaic requiring 64 differential output channels to be transmitted to electronics located over 2 m from the CCDs and digitized with less than 10 e- read noise at 1 MHz pixel rate. To minimize pixel overhead, the Reset Gate pulse is generated inside the dewar by a pin driver controlled by a very short pulse using an LVDS interface. Overlapping serial clocks spanning the entire pixel are made entirely triangular with slopes tuned to cancel substrate return current and minimize high frequency content to improve common rejection by the fully differential signal path. We document the trade between settling time after charge dump and linearity and illustrate the desirability of generating both Summing Well and Reset Gate edge close to the CCD. The parallel clocking overhead is exacerbated in ZTF by ganging multiple CCDs but is hidden by overlapping the parallel shift with pixel readout. To suppress fixed pattern due to the concurrent parallel clocks, slow overlapped triangular waveforms panning the entire line time are employed to null the substrate current, in the same manner as the serials. Both noise and speed requirements are exceeded on all 64 channels, with margin. At all pixel rates the median noise is as good as can be expected for differential transmission being √2 times the single sided noise published in the data sheet for the CCD231- C6 CCDs. Linearity is preserved even at 840 ns pixel time, and crosstalk is less than 10 ppm

Ecological restoration alters nitrogen transformations in a ponderosa pine-bunchgrass ecosystem

Ponderosa pinebunchgrass ecosystems of the western United States were altered following Euro-American settlement as grazing and fire suppression facilitated pine invasion of grassy openings. Pine invasion changed stand structure and fire regimes, motivating restoration through forest thinning and prescribed burning. To determine effects of restoration on soil nitrogen (N) transformations, we replicated (0.25-ha plots) the following experimental restoration treatments within a ponderosa pinebunchgrass community near Flagstaff, Arizona: (1) partial restorationthinning to presettlement conditions, (2) complete restorationremoval of trees and forest floor to presettlement conditions, native grass litter addition, and a prescribed burn, and (3) control. Within treatments, we stratified sampling to assess effects of canopy cover on N transformations. Forest floor net N mineralization and nitrification were similar among treatments on an areal basis, but higher in restoration treatments on a mass basis. In the mineral soil (015 cm), restoration treatments had 23 times greater annual net N mineralization and 35 times greater annual net nitrification than the control. Gross N transformation measurements indicate that elevated net N mineralization may be due to increased gross N mineralization, while elevated net nitrification may be due to decreased microbial immobilization of nitrate. Net N transformation rates beneath relict grassy openings were twice those beneath postsettlement pines. These short-term (1 yr) results suggest that ecological restoration increases N transformation rates and that prescribed burning may not be necessary to restore N cycling processes

Pigmentation of the Cornea Secondary to Tinted Soft Contact Lens Wear

Purpose. To report a case of pigmented corneal iron lines following use of tinted soft contact lenses (CL). Methods. A retrospective case report. Results. A 16-year-old girl was referred with suspected CL-related keratopathy OU, having recently switched to tinted soft monthly disposable CLs (8.4/14.0 −3.00 OD, −3.25 OS Aquamarine SofLens Natural Colours, Bausch and Lomb, New York, USA). Both corneas exhibited symmetric superficial corneal pigmented iron lines, which gradually disappeared following discontinuation of CL wear. Conclusions. Pigmented corneal rings have been reported in normal ageing corneas, in certain pathological conditions, and in association with altered corneal topography following LASIK and orthokeratology. We suspect a poorly fitting CL resulted in localised tear pooling between the CL and cornea, and subsequent iron pigment deposition, similar to that seen with orthokeratology. Cosmetic CLs bought via the Internet can be used in an unsupervised manner, with possible impacts on visual function and potential complications

Stand-replacing wildfires increase nitrification for decades in southwestern ponderosa pine forests.

Stand-replacing wildfires are a novel disturbance within ponderosa pine (Pinus ponderosa) forests of the southwestern United States, and they can convert forests to grasslands or shrublands for decades. While most research shows that soil inorganic N pools and fluxes return to pre-fire levels within a few years, we wondered if vegetation conversion (ponderosa pine to bunchgrass) following stand-replacing fires might be accompanied by a long-term shift in N cycling processes. Using a 34-year stand-replacing wildfire chronosequence with paired, adjacent unburned patches, we examined the long-term dynamics of net and gross nitrogen (N) transformations. We hypothesized that N availability in burned patches would become more similar to those in unburned patches over time after fire as these areas become re-vegetated. Burned patches had higher net and gross nitrification rates than unburned patches (P < 0.01 for both), and nitrification accounted for a greater proportion of N mineralization in burned patches for both net (P < 0.01) and gross (P < 0.04) N transformation measurements. However, trends with time-after-fire were not observed for any other variables. Our findings contrast with previous work, which suggested that high nitrification rates are a short-term response to disturbance. Furthermore, high nitrification rates at our site were not simply correlated with the presence of herbaceous vegetation. Instead, we suggest that stand-replacing wildfire triggers a shift in N cycling that is maintained for at least three decades by various factors, including a shift from a woody to an herbaceous ecosystem and the presence of fire-deposited charcoal

Why Don’t Employers Hire and Retain Workers with Disabilities?

Introduction Despite persistently low employment rates among working-age adults with disabilities, prior research on employer practices and attitudes toward workers with disabilities paints a generally rosy picture of successfully accommodated workers in a welcoming environment. Findings from previous studies might have been biased because of either employer self-selection or social desirability, yielding non-representative or artificially positive conclusions. Methods In this study, a novel approach was used to survey human resource professionals and supervisors working for employers known or reputed to be resistant to complying with the ADA’s employment provisions. Attendees of employer-requested ADA training sessions were asked to assess various possible reasons that employers in general might not hire, retain, or accommodate workers with disabilities and to rate strategies and policy changes that might make it more likely for employers to do so. Results As cited by respondents, the principal barriers to employing workers with disabilities are lack of awareness of disability and accommodation issues, concern over costs, and fear of legal liability. With regard to strategies employers might use to increase hiring and retention, respondents identified increased training and centralized disability and accommodation expertise and mechanisms. Public policy approaches preferred by respondents include no-cost external problem-solving, subsidized accommodations, tax breaks, and mediation in lieu of formal complaints or lawsuits. Conclusions Findings suggest straightforward approaches that employers might use to facilitate hiring and retention of workers with disabilities, as well as new public programs or policy changes that could increase labor force participation among working-age adults who have disabilities