Our research focuses on the population dynamics of plants and how they are influenced by impacts of natural disturbances and global environmental change. We are particularly interested in the interactive effects of fire, grazing and drought in grasslands and woodlands in southern Australia, and how climate change, fragmentation and shrub encroachment affect ecosystems.

Thursday, 31 May 2012

Picking a thesis research topic

Late last year, the band REM disbanded after 30 years in the music industry. I don't actually care much for REM's music (sorry!), but I do admire them for their committment to do their own thing over what might be considered their 'working life'. Rather than write music to top the charts, they wrote and performed music that they were really interested in making. This is probably what enabled them to be productive over the long-term - all 20+ albums in REM's case! I like Tim Winton too - the Australian author famous for books such as Cloudstreet and Blueback - for exactly the same reason. He writes about things that interest him (the sea, blokes, curiousity), rather than what will necessarily sell books. And, in some ways, I think students contemplating doing a research thesis could learn a little from them.

No matter what people say, doing ecology is hard! Natural systems are, after all, complex. There are lots of factors that affect ecological processes, and teasing them out can be a challenge. Hence, trying to decide what to study can be a daunting task for any new grad student. Funnily enough, however, modern ecology is not data (or technique or computation) limited – it’s often ideas limited. If you are lucky (like I was), you get to study the "low-hanging fruit" - the questions that need to be answered first before you can move on to deeper understanding. Do grassland plants have soil stored seeds? Is germination stimulated by fire? How big does a gap in the grassland canopy need to be for recruitment of forbs? Once these questions have been picked off, you'll have to think more critically about the next round of obvious things to ask. And this is the challenge.

Hence, when choosing a research project, it's advisable to first read widely, see what’s going on in your field (and related fields), and identify some general question or idea that you can address in your own system? This means being inquisitive and wanting to know where the field is at and how you might contribute meaningfully.

So, how important should this question be?

That is a difficult question to answer. Publishing metrics (Impact Factors, H-scores, etc) and funding trends mean that you should have your eye "on the game" if you want to make ecological research your career. But this doesn't guarantee you'll do good science. Good science involves carefully thought out hypotheses, and well-designed tests of these hypotheses. And to succeed, I think it is critical that you passionately believe in the research you are doing - you own it!  Hence, jumping on the latest "hot topic" in ecology (think the productivity-richness debate) might make your research seem current, but it is just as likely to move quickly on. Good ecological science, however, will stand the test of time.

There are two general observations I'd make when it comes to developing research questions:

First, avoid testing poorly developed hypotheses / theories with data you really don't understand and which wasn’t collected for the purpose. Trying to make your data fit a question isn't good science. That said, the recent surge in meta-analyses shows that when such data do exist, they can provide powerful insights that site by site studies just can't achieve.

Second, selecting a topic based on the choice of tool, not because of the question, is a no-no in my opinion. I’ve seen papers that seem to imply their study is important simply because they used [insert latest fad or bandwagon here]. Bandwagons that depend heavily on technical proficiency might make your research look great, but from my perspective, it is much easier to learn a new skill than to do original, ground-breaking science.

Of course, this is my personal view on the matter and you may disagree. There is no one or right approach here. That said, I'm a question-driven person. Tools are just that: tools! Good luck navigating a research thesis - it really is one the best things you'll ever do - particularly if you find a topic that grabs you and acknowledges those who came before you!!

I'll leave you with a recent comment I saw from Steve Packard (in Ian Lunt's excellent blog) - I thought it was apt (he was talking about the early days of restoration ecology):

"restoration was in the early Wright Brothers stage of flight. We were barely getting off the ground, but we were tackling the most fun and fundamental questions...............in the Wright Brothers’ day, learned academics were also trying to explore flight, but the Wrights made the key discoveries because they had the hammers and wrenches in their own hands and did their own flying."

Friday, 11 May 2012

What have golf balls got to do with grasslands?

Cooper Street grassland, dominated by the C4 grass Themeda triandra
One of the fundamental challenges to grassland management in Victoria is the role of biomass accumulation and the perceived necessity for disturbance regimes that reduce this biomass. In the absence of disturbance (to the vegetation, not the soil), biomass accumulates and smothers intertussock flora, preventing seedling recruitment by native species. In extreme cases, biomass accumulation smothers dominant tussock grasses, leading to their decline and replacement with annual exotic species. For some fauna, dense litter reduces favoured habitat states.

The rate of biomass accumulation, however, varies across the geographic range of native grasslands in southern Australia. Undisturbed Themeda grasslands in mesic regions have relatively high productivity and accumulate large quantities of dead grass, which decomposes very slowly and accounts for the majority of accumulated litter. By contrast, dead grass does not appear to accumulate over long periods in drier grasslands (dominated mainly by Rytidosperma spp., Austrostipa spp.), but instead appears to decay (or blow away) relatively quickly. Thus, low levels of accumulated biomass in xeric grasslands reflect high decomposition rates as well as low productivity rates.

The differences that occur in litter build-up underpin the notion that different types of native grassland need disturbance regimes that differ in their frequency. The frequency of disturbance might be timed to coincide with increasing litter levels that compromise native plant and animal diversity but developing ‘absolute’ disturbance regimes for native grasslands has proved difficult, chiefly because grasslands vary in their rate of litter accumulation. What is needed is a simple, effective assessment tool to quantify levels of biomass accumulation at individual sites upon which management actions can then be implemented.

Since 2006, La Trobe University, in conjunction with Parks Victoria, have been developing a grassy ecosystem biomass monitoring protocol to enable rapid field assessment. The basis premise of this assessment was to use a surrogate measure that would (a) indicate something about absolute levels of biomass in a grassland and (b) the assessment outcomes could be linked to management actions necessary to maintain diversity. This idea builds upon the habitat condition assessment method that identifies the optimum range of grassland structures necessary to maintain the Plains Wanderer, an endangered bird that prefers open-structured grasslands on the riverine plain.

Nick Shultz developed a pilot project to examine the potential value of using surrogates to estimate grassland 'condition'. Briefly, a 1 x 1 m quadrat is located in uniform grassland vegetation and 18 golf balls are dropped into the vegetation (one at a time) from a height of approximately 1.3 m. A photograph is taken of the plot and ‘golf ball visibility’ assessed either from the photo or in the field, and a biomass sample (0.25 m2) is harvested from the plot. The aim of the study was to determine whether the biomass of a grassland could be estimated using the surrogate of ‘golf ball visibility’. The rationale is simple: the fewer golf balls that are observed, the denser the vegetation and the higher its biomass. If the surrogate measure was found to be robust, managers could use the golf ball visibility method to estimate their grassland’s current condition, and plan management interventions based on this information. Essentially, if grassland biomass drives species interactions (negative interactions occur between grassland biomass and plant species diversity, as well as being poor habitat for some grassland fauna), giving managers a tool to estimate biomass is an important step to managing for biodiversity conservation.
Grazed grassland on the Northern Plains. 
How many of the 18 golf balls can you see?
What does this tell us about biomass and the need  for biomass reduction? 
(Photo: John Morgan)

The initial work was promising  but several issues were identified for further study before it could be adopted, including the quantification of the variability in the scoring of the number of golf balls between observers to determine whether this is significant. 

Using Post-Grads as observers, we found that they tended to under-estimate the ball score at low scores, but all observers correctly identified the differences between low biomass (high ball score: 15-18) and high biomass (low ball score: 0-5) .  Hence, it was concluded that despite observer variation, the methodology was repeatable and reliable when trying to identify grassland condition that varies from sparse to dense.

While it is an imprecise method of estimaing biomass in grasslands, the golf ball visibility method does seem useful to inform grassland managers about the existence of grassland 'states' (i.e. low biomass, moderate biomass, high biomass) and the dynamic nature of these states (i.e. how quickly they change from year to year), particularly in response to rainfall. When linked to biodiversity values (such as the existence of Plains Wanderers), the surrogate measure does seem to help managers make decisions about their grassland 'state' and when management actions might be desirable.

The Plains Wanderer
(Photo: http://www.birdway.com.au/pedionomidae/plains_wanderer/index.htm)