Search

McGuirk, M.T.; Kennedy, D.M.; Konlechner, T., and Chiaradia, A., 2021. Quantifying changes in surface elevation in conjunction with growth characteristics of incipient and foredune vegetation. Journal of Coastal Research, 37(1), 216–224. Coconut Creek (Florida), ISSN 0749-0208. Vegetation is critical for the initiation and growth of incipient dunes and foredunes by providing structure to entrap and store sand. Vegetation characteristics (leaf length, width, height, and quantity) directly influence the rate and volume of sand deposition and therefore the final dune morphology. This paper describes a low-cost and highly portable method to quantify changes in sand surface elevation in relation to plant growth character. A sediment elevation platform was constructed from steel and Perspex, from which surface elevation and plant character can be measured with a movable wooden dowel. This was used in conjunction with a point intercept pin frame to quantify leaf height and number of touches, from which leaf density and frequency were calculated. The system is collapsible, lightweight, and costs AUD 360. It may be operated by a single person. It was tested in a pilot study conducted at Phillip Island, Australia. Plant attributes of two dominant coastal grasses (Spinifex sericeus and Thinopyrum junceiforme) were quantified in December 2018 and January 2019, and sand elevation changes were quantified in January and February 2019. Data collected during the measurement period displayed the influence of plant growth on sand accumulation on a monthly scale. Measurements showed an increase in sand surface elevation from January to February. The average vertical sand accretion for the quadrant with T. junceiforme in January was 29 mm and in February was 89 mm, whereas S. sericeus had an average vertical sand accretion for January of 95 mm and for February of 162 mm. The number of leaves of S. sericeus increased from December (48) to January (169). This new method enables tracking of changes in sand morphology, along with the specific plant growth characteristics. This knowledge may enable the planning of specific dune morphologies using specific plant species and assist in dune recovery after erosion. [ABSTRACT FROM AUTHOR]

The Elevation sensitive Oblique Incidence Sounder Experiment (ELOISE) was an extensive experiment undertaken by the Defence Science and Technology (DST) Group that focused on collecting ionospheric sensor data from multiple overlapping ionospheric paths in the Australian region in order to improve understanding of the characteristics of ionospheric variability and its effect on HF radio propagation. The experiment ran from July to October 2015 and included a period of three weeks of increased sample density and three days of dedicated over-the-horizon (OTH) radar operations. It was anticipated that ELOISE would sample a wide range of environmental conditions and present an opportunity to characterise periods of "normal variability" and periods of "exceptional variability" in the ionosphere. This report is a general description of the aims of this experiment and the types of data collected. Particular interest focused on observing and measuring variability in ionospheric electron density gradients and their effect on oblique HF propagation. To this end, ELOISE established a pair of two dimensional HF receiver arrays to directly measure the oblique angle of arrival (AoA) on many overlapping oblique paths. ELOISE also established a dense sub-network of spatially separated quasi-vertical incidence soundings in the vicinity of Alice Springs in central Australia. This enabled a comparison of gradients observed in a dense network of vertical sounders with gradient effects observed in oblique propagation passing overhead. Several additional ionospheric observing systems were also used to give complementary pictures of the fine scale characteristics of ionospheric variability in the region. This paper is an overview of the 2015 Elevation sensitive Oblique Incidence Sounder Experiment (ELOISE), an experiment designed to observe and characterise mid-latitude ionospheric disturbances in the Australian region and understand their impact on high frequency (HF) signal propagation. ELOISE involved the simultaneous operation of a large collection of ionospheric sounders enabling ionospheric variability to be characterised on a finely sampled large scale. Particular efforts were made to provide direct high fidelity measurements of the angle of arrival (AoA) on many oblique HF propagation paths. These direct AoA measurements imply horizontal electron density gradients that can be compared to ionospheric gradients estimated from conventional models of the ionosphere derived from the spatial network of sounder sites. The size and scope of the experiment are detailed in this paper and some preliminary results are presented. [ABSTRACT FROM AUTHOR]

The influence of the El Niño-Southern Oscillation (ENSO) on NSW coastal storm severity was investigated by comparing the yearly mean Southern Oscillation Index, SOI, with the yearly averaged storm severity Ω measured at the NSW coast. It was found that Ω correlates well with SOI, i.e., Ω generally increases with SOI. The probability distributions of storm peak wave height and yearly mean SOI were also studied and were found to follow a Gumbel distribution. A simple linear relationship between extreme wave height and yearly mean SOI was then derived. At the NSW coast or at other coasts with similar wave climates, coastal recession and increased coastal damage may be expected in La Niña years, while beach recovery and reduced coastal threat may be expected in El Niño years. [ABSTRACT FROM AUTHOR]

Simple Summary: Pre-grazing pasture height has significant impact on intake rate and intake in grazing dairy herds, and the ideal pre-grazing pasture height varies between pasture species. Defining the ideal pre-grazing pasture height of lucerne pasture has potential to significantly increase milk production of cows on sub-tropical partial mixed ration (PMR) dairies in Australia. Pasture intake of dairy cows was highest when the pre-grazing pasture height of lucerne was 39 cm and a proportion of the pasture remained un-grazed, irrespective of the amount of mixed ration offered. The effect of lucerne (Medicago sativa L.) pre-grazing pasture height on pasture intake and milk production was investigated in a sub-tropical partial mixed ration (PMR) dairy system in south-east Queensland, Australia. The experiment involved a 26-day adaptation period followed by an eight-day measurement period during April and May 2018. Twenty-four multiparous Holstein-Friesian dairy cows were offered a mixed ration at either 7 (low) or 14 (high) kg dry matter (DM)/cow/day and allocated pastures at pre-grazing heights ranging from 23 to 39 cm. The targeted pasture intake was 14 and 7 kg DM/cow/day for cows offered the low and high mixed ration allowances respectively, with a total intake target of 21 kg DM/cow/day. Pasture structure did not limit pasture intake as the all groups left at least 12% of the allocated area ungrazed, and therefore could selectively graze pasture. There was no significant difference in intake between mixed ration levels, however intake had a positive linear relationship with pre-grazing pasture height. For every one cm increase in pasture height, intake increased by 0.3 kg DM/cow/day. Using a grazing strategy that ensures the some pasture remains ungrazed and the pre-grazing height of lucerne is approximately 39 cm above ground level will maximise pasture intake in sub-tropical PMR dairy systems. [ABSTRACT FROM AUTHOR]