Finally: My Research Results

Treeline

The aim of my research was to investigate the Victorian treeline physiognomy (i.e. the general position, form and appearance of the treeline) after a major disturbance, building on a previous data set collected shortly after wildfire. This research investigated the key questions that might indicate permanent change over the medium to long term. It was assessed by evaluating seedling elevation, density and key factors driving seedling establishment at treeline ecotones burned during the 2003 wildfires, and then re-examining the specific locations initially measured.

Locations

Seedlings found in the Victorian Alps after fire are establishing themselves in the alpine zone at higher elevations than the current treeline, and in greater numbers in the subalpine zone in locations where competition is constrained, litter is minimised, and there are adequate amounts of original trees with girths of approximately 50cm. Subsequently, the models suggest that the Victorian treeline physiognomy has slightly changed due to the 2003 alpine fires.

Model1

The analysis of increase in treeline elevation after fire was limited by few seedlings establishing above the current treeline. Despite this, a comparison of the burnt and unburnt transect models indicates that seedling establishment probabilities above the treeline are greater after fire compared to locations long absent of fire. This implies an increase in seedlings at elevations higher than the treeline after fire. The model calculates that there is a 31% chance of seedling establishment two metres above the treeline, and an 18% chance five metres above the treeline. Even higher elevations estimate much smaller probabilities. Subsequently, it is likely that only single trees will sparingly establish within the tree species zone, and consequently become outpost trees.

Model 2

An increase in treeline density after fire is supported by modelling, as seedling numbers are predicted to reach a maximum when fire is a recent occurrence. However, the Time Since Fire predictor variable was found to have 25% less influence than Litter, and 20% less influence than Evenness in maximising seedling numbers as calculated during sensitivity analysis. This suggests that fire may initially facilitate additional seedling numbers, however the magnitude of the density change is more dependent on the amount of competition in the area coupled with the quantity of litter cover. Locations that exhibit evenness across quadrat features are much more likely to support multiple seedlings, most likely due to a reduction in competition, and where a niche space can be realised. Secondly, a reduction in the amount of litter coverage within a location increases the number of seedlings. This is probably because litter acts as a barrier to seedling germination and emergence. In contrast, a decrease in litter allows greater seedling numbers to establish.

Model 3

Modelling of factors that influence seedling establishment after fire determined that apart from competition and litter, the amount of trees and their age are significant macro level factors influencing subalpine seedling establishment. Seedling counts were highest due to significant influences of competition and litter, and this was verified by models which determined a 91% probability of seedling establishment when competition and litter was minimised.
Tree characteristics were found to be imperative to seedling establishment. Tree girths between 20cm and 50cm are the only circumferences that can result in seedling probabilities above 90%, with substantial probability decreases above and below these girths. By relating girth to the age of the tree, this outcome ultimately defines the optimal reproductive age of the stand to facilitate seedling establishment after fire. Using previously created models that evaluate the relationship of Eucalyptus pauciflora subsp. Niphophila, tree girths of 20cm to 50cm correspond to tree ages of approximately 24 years to 42 years.
Finally, the quadrat must have a sufficient amount of trees to facilitate seedling success. A seedling establishment probability of above 90% was modelled to occur in locations where tree coverage ranges between 45% and 50% of the total area of the quadrat.

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CSIRAC – World’s oldest computer

At the heart of Melbourne Museum, there’s an exhibit that looks like a set of old metal gym lockers, stuffed with racks of valves, wires and other old electronic equipment. It’s actually a computer, Australia’s first and only the fourth built in the world. Despite its humble appearance, in the minds of many, it’s the most significant computer around today. Because it’s the only machine of its era left on the planet.

“Of the handful of computers operating before 1950 it’s the only one still intact,” says Peter Thorne, of the sprawling behemoth. “Also, we’re pretty confident now that it was the first computer in the world to play computer music, which is essentially the birth of multimedia. That happened in 1951, exactly 50 years ago.”

Called CSIRAC – after the Council for Scientific and Industrial Research (later CSIRO) which built the machine in 1949 – it weighed a couple of tonnes and sucked enough electricity to power an entire suburban street.

“It used vacuum tubes or valves which lit up,” says Thorne, recently retired from Melbourne University’s computer science department and an expert on computer history.

“These were the electronics of the time and they weren’t terribly reliable”. Indeed, compared to computers available today, CSIRAC’s grunt seems laughable. It ran at 0.001 megahertz, with 2000 bytes of memory and a mere 2500 bytes of storage. By comparison, a typical desktop PC today has a processing speed of 500 megahertz, with 64 megabytes of memory and a hard disk containing 10 gigabytes (10,000 million bytes) of storage.

Nonetheless, to the people who used it, CSIRAC was magic.

“Before CSIRAC, if you wanted to do mathematical calculations in Australia, you hired a person, usually a woman, who used a calculating machine – either mechanical or hand-cranked,” says Thorne.

“He or she could do about one operation a second, whereas CSIRAC could do 1000 operations a second. You only used CSIRAC for an hour at a time but you could do the amount of work that would otherwise have taken 20 people a week.”

The newfound computational power was initially used by scientists researching everything from the thermal properties of buildings to the mysteries of the cosmos. It had a hand in the design of several early Australian skyscrapers and was instrumental in performing the river flow analysis needed to build the Snowy Mountains hydro-electric scheme. And it substantially increased the reliability of weather forecasting.

Later there were commercial applications, such as loan repayment calculations – the kind of thing a bank can do for you now as you stand at the counter, but which in those days was considered quite remarkable.

But it was CSIRAC’s ability to play music that has helped ensure its place in computing history. It seems the first tunes were played between 1951 and 1953, and these are now believed to be the earliest played anywhere in the world.

By 1954, however, things were changing. A new generation of faster computers was on the horizon. The transistor had been invented and it was clear any move to build a transistorised version of CSIRAC would be a very substantial project. Despite its impressive record, CSIRO subsequently terminated the project.

After the computer project in Sydney was terminated, CSIRAC was transferred to Melbourne University where it was used by university and CSIRO staff for another nine years. It was here that its circle of influence widened, with the first computing courses run for people outside the university.
Word got out to the ordinary citizens too, although early expectations were not always realistic. Staff were often besieged by calls from the public wanting answers to questions in the television quiz shows that were popular at the time, for example.

While other early computers were cannibalised so their parts could be used for later models, CSIRAC’s use as a computing workhorse actually helped ensure its survival. By the time it was turned off in 1964, it was the oldest working computer in the world.

Sadly, it’s not an option to make CSIRAC operational again today. Time has taken a toll on this fragile dinosaur.

So what exactly would happen if anyone tried to relive the magic by switching it on?

“A lot of its components would not stand having voltages applied to them again,” says Thorne. “I think it would probably catch fire.”

http://www.abc.net.au/science/slab/csirac/

Graduate seminar at the half way point

As part of the Graduate Seminar subject, all students take a turn in running a class. You also get to choose what topic you are going to present. That means there is a widely varying range of topics that we are being exposed to. So far we have looked at: The role for nuclear energy in biodiversity conservation, safety assessment of GM plants, next generation monitoring using environmental dna, human population reduction and environmental problems, antibiotic resistance and environmental contaminants and restoration and ecosystem services and biodiversity. Wow – what an eclectic bunch of environmental issues to cover. Then last week, we had my favorite two topics to date: Bias in the media, and Uncertainty in science.

The first paper we looked at demonstrated that US prestige-press coverage of global warming from 1988 to 2002 contributed to a significant divergence of popular discourse from scientific discourse. This failed discursive translation resulted from an accumulation of tactical media responses and practices guided by widely accepted journalistic norms. Through content analysis of US prestige press (New York Times, the Washington Post, the Los Angeles Times, and the Wall Street Journal) the paper focused on the norm of balanced reporting, and showed that the prestige press’s adherence to balance actually leads to biased coverage of both anthropogenic contributions to global warming and resultant action.

Next we looked at how uncertainty is pervasive in ecology where the difficulties of dealing with sources of uncertainty are exacerbated by variation in the system itself. Attempts at classifying uncertainty in ecology have, for the most part, focused exclusively on epistemic uncertainty. In the paper, uncertainty was classified into two main categories: epistemic uncertainty (uncertainty in determinate facts) and linguistic uncertainty (uncertainty in language). In particular, the authors demonstrated the importance of recognizing the effect of linguistic uncertainty, by developing a clear understanding of the various types of uncertainty, how they arise and how they might best be dealt with.

Second Last Survey

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Transect McKay South 1 was very hard to find – the heath was tall, and the walk was steep and slow. The transect was distinguishable by having a ribbon finger of trees, however it was not as densely packed as other sites. There was pampa to the right hand side of the transect, a watercourse running down the middle of the transect, and tall heath on the left hand side of the transect.

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This was a degraded site with many invasive species and signs of deer. In the watercourse areas, there were many maturing willow trees seen, and they were starting to choke up some areas. In the pampa areas there were blackberries starting to sprout. Deer hoof marks and scat were seen throughout.

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The striking factor about this transect was the amount of dead trees present. All down the right hand side of the transect (next to the pampa) were dead trees. They were the original old trees that had been burnt in the fires, and not survived. What does that say about the fire and conditions on this side of the transect? The dead trees ran all the way down the transect. The trees at this transect were also very tall – some running as high as 15m. This tends to show that these treelines are not at the trees’ physical limit.

The fieldwork continues

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Two more days, two more transects. These ones were located past Nelse North – so quite a hike out from the Watchbed Creek gate – estimated at over 7km one way. Luckily the weather was fantastic as we walked out – high above the clouds in the valley below. The sites were quite simular in that they appeared quite xeric in nature, with low lying heath and grasslands dominating the intra-tree space. There was evidence that quite a few trees had burnt and died at these locations, and very few new saplings were counted. The really interesting feature of site Nelse North 1 was that a stand of trees ran down the left hand side of the transect, and the right hand side was clear with no new saplings evident. This was fascinating, because it demonstrated that there was no sideways movement of trees either, even below the treeline (apart from testing the usual upwards migration above the treeline). So it tends to reinforce the hypothesis that positive feedback dominates at short distances (at the tree edges) and negative feedback at larger distances (between the fingers).

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A Long Weekend of Fieldwork

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Luckily, I was able to get three other cheery volunteers to help me survey Mt Loch on the Labour Day long weekend. That was because transect Loch North 1 and 2 took almost 2 full days for four people to survey. The two transects are located side by side, with (for the first time) one of the original marker stakes used by Libby found at the base of one of the trees. Trees in these transects were situated in clumps of four or five trees with many short stems. There was a large amount of shale rock that was splintered into small pieces of rock.

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The site espoused a harsh climate with stunted vegetation and evidence of new seedlings continually dying and re-sprouting from the roots. There were many new saplings in quadrants 11 and 12, although they were very small. Some had quite thick stems which looked to be dying, whereas new shoots of regrowth was coming thru from the base. It was also the first site with multiple original tree deaths with no lignotuber re-sprout. Possibly this site experiencs harsh winds and a longer winter season. A couple of original trees (that were unburnt in the 2003 fires) were located in the transects above the treeline with some new seedlings noticed in the vicinity of these trees.

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As evidence by how different this site was, the average amount of trees found at the other transects was around 70, whereas, the trees surveyed at Loch North measured almost 250! The work was hard and long. But in the end most rewarding as we were lucky with most favorable weather conditions of light winds and blue skies by the last day.