New analyses (thankfully) confirm a long-held notion in grassland ecology

Kangaroo Grass grassland at Evans St
in Sunbury, Victoria,  with lots of
native forbs. This type of grassland
has always been thought to be associated
with areas that have a long history of
frequent burning and little stock grazing.

One of the most important papers on the ecology and management of temperate native grasslands in southern Australia was published by John Stuwe and Bob Parsons in 1977. It's a great paper for two main reasons.

First, it has a very simple objective. To answer the question: how do long-term management regimes affect the floristics of grasslands. This was a paper way ahead of its times in some respects because it recognised that grassland 'condition' (or 'state' to used the modern jargon) was likely a function of its disturbance regime. In this case, frequently burned areas versus grazed versus 'unmanaged'.




Bob Parsons

Second, despite 35 yrs of research since then, the overarching premise of the paper still stands. There hasn't been a magic new understanding of grasslands, just better resolution of the mechanisms that underpin the reponses observed by Stuwe & Parsons (S&P). For example, my own research has shown that grassland canopy gap size positively affects recruitment success  and survival of many grassland herbs because it allows high light penetration to the soil surface. Gaps can be maintained by frequent burning, hence maintaining species coexistence through ramet survival and maximising infrequent (but potentially very successful) recruitment opportunities.

Much of the important insight that was gained from the S&P paper was based on collecting floristic data from areas with different management history (lists of species and their abundance using 4 x 5 m quadrats) and then using a technique called 'hand sorting' to create a Two-Way Table. From this, they identified 'character species' that typify each management area, as well as community metrics such as species richness. They found that frequently burned areas contained more native species than unmanaged areas, and that daisies were more common in burned areas compared to grazed areas. But, when you eyeball the data, there appears to be a lot of overlap in the species composition of grasslands with different management (both in native and exotic species). When I gave the dataset to my Honours student to look at, they were not convinced that S&P had such clear-cut outcomes as appear in their paper. Could S&P have 'over-emphasised' their data, rendering one of the great papers in Australian grassland ecology misleading????

With modern analytical methods like classification and ordination, there is an opportunity to check whether the basic results of the original study were correctly manipulated and interpreted. We can add rigour to the data analysis rather than relying on subjective sorting as was originally done.

With this in mind, I transcribed the original data (which is both found in the original thesis and in the published paper, and shows the value of archiving ecological data in accessible locations that can be retrieved despite changes in technology). I then used a common data analysis package to examine floristic data (Primer) and undertook both a non-metric multidimensional scaling ordination (NMDS) and a cluster analysis. If S&P were correct - that management history affects the floristic composition of grasslands - then we should see "groupings/clusters" in the resultant outputs that are reflective of the a priori identified management regimes. And, using analyses such as ANOSIM and SIMPER (I won't go into the details), we can see if management causes significant differences in composition, and which species are responsible for the differences.



Lightly grazed grasslands have fewer
native daisies than frequently burned
grasslands 

With a little trepidation, I ran the analysis. Either way, the outcome was always going to be interesting. But I didn't really want to 'prove' S&P got it wrong.

Much to my relief, the ordination and cluster analysis confirm that management history in native grasslands DOES affect grassland composition, and that the differences are due to those identified by S&P - more daisies in frequently burned grasslands, and more weeds in unmanaged and grazed grasslands. Phew! That was somewhat of a relief given the importance this paper has had for a generation of grassland ecologists, many of whom have trained under Bob Parsons.


Here is the main figure I generated showing the outcomes of this analysis.

In this ordination, based on abundance data (so species are weighted according to how much cover they project), we can see that RA (frequently burned railway remnants) are floristically distinct from both RO (unmanaged roadside remnants) and PG (remnants partially grazed by stock). RO and PG remnants do not differ significantly from one another in composition (indicating there is a lot of overlap in the species that occur in these remnant types). The way to read the figure is such: coloured symbols indicate quadrats that were sampled in areas with different management histories. How far apart each symbol is from other symbols indicates how similar the composition of any two quadrats is. Hence, if two symbols are near each other, they are similar in composition while the most dissimilar quadrats will be further apart from each other.

Clearly the analysis lends support to the idea that the composition of grasslands (both species present, and the abundance of those species) is affected by management history.

You can see also which species mostly give rise to these stark differences. The lines you see on the ordination that radiate from the centre of the image, with species names at their end, tell us which species have a high contribution in quadrats. We can see that most of the lines point towards the green symbols (the frequently burned railway remnants); this can be equally read as they are pointing away from the RO and PG remnants. These species are mostly native forbs (including the daisies Leptorhynchos and Helichrysum (now Chrysocephalum)) and we interpret this as suggesting that RA sites are characterised by a suite of native (and some exotic) species that tend not to be found as much in PG and RO sites (i.e. they contribute little there). By contrast, the unmanaged RO sites tend to be characterised more by exotic species such as Holcus and Hypochoeris.

Hence, S&P seem to have got it right; frequently burned roadsides have a composition that is different from other native grasslands, and this is due to management history promoting some species over others. In essence, daisies are promoted in frequently burned areas, but tend to disappear in grazed and unmanaged areas. The concept of 'habitat segregation', first coined by S&P, has been at the heart of conservation management of native grasslands for 35 years and continues to resonate even today. I wonder what other ecological and conservation ideas will stand the test of time.

Here's to S&P.


Further Reading

Stuwe, J. & Parsons, R.F. (1977) Themeda australis grasslands on the Basalt Plains, Victoria: floristics and management effects. Australian Journal of Ecology 2, 467-476.

Morgan, J.W. (1998) Importance of canopy gaps for recruitment of some forbs in Themeda triandra-dominated grasslands in south-eastern Australia. Australian Journal of Botany 46, 609-627.

Are alpine ecosystems being transformed by climate change and fire?

I'll let you be the judge!

Below is a series of paired photos that I'm using to look for obvious changes in the 'woodiness' of alpine ecosystems in the Victorian Alps over the last few decades that might help us understand how alpine vegetation is responding to global change drivers such as climate change and fire.

Theory predicts that with climate warming - and there has already been a 0.8 deg C increase in Australian mountains over the last century - that alpine treelines should migrate upslope to higher elevations, while grassy communities might become shrubbier. Where low temperatures might have limited woody growth in the past, warming eases or relaxes those environmental filters.

First, I searched the Trove website to find historical photos that show mountain landscapes - this is the archive of the National Library of Australia. Mountains are good places to look for vegetation change over time using old photos because it is often easy to relocate the approximate location where the original photo was taken. You can match up ridgelines, rock outcrops, mountain summits etc and get a pretty good approximation of the original location. This is important if you want to re-photograph that same view from which to then make comparisons over time.

While it sounds easy, many of the original shots are too grainy to use, or there is a horse / cow / cattleman obscuring the really important bit of the landscape you want to see. Eventually, however, I found about 40 photos across eight mountain regions that looked promising for comparative purposes. I went up to the mountains last summer and tried my hardest to line up the old shot so I could take something as close as possible to the original. Surprisingly it is really difficult to get the exact same shot, although I think I succeeded some of the time!

While the interpretations are qualitative rather than quantitative at this stage, it is clear that there has been very little obvious change in the woody component of the landscape over a 60-100 year period. This was somewhat surprising given the substantial regional warming that has occurred over the last few decades. There have also been several fires in the alps over the last 80 years and these are generally expected to favour shrub establishment and hence, an increase in heathy vegetation in grasslands. My overriding impression is that treelines have not moved much. Total tree cover is higher in some photos, but this is mainly due to resprouting after fire rather new plants 'infilling' the landscape. Shrub cover is higher in some places but not others. Hence, structural transformation is not apparent.

I hope you enjoy these comparisons. If you think you have photos that might be useful to examine structural changes in alpine areas of Australia, I'd be really keen to hear from you (J.Morgan@latrobe.edu.au). Even better, how about you go up and take a shot of the same view and let me know whether you think the alpine is transforming!

Mt Hotham, looking towards Mt Loch (1929 and 2012).
Note substantial growth of trees in most recent photo (after 2003 fires).
These trees can be seen in the original photo - reshooting after
the 1926 fires.

Looking west towards The Bluff (in 1953 and 2012) from
Mt Eadley Stoney. Snow Gums appear more common now.
Low heathland still dominates much of the area. 

On the ridgeline towards Mt Loch (from Mt Hotham): 1946 and 2012
Note: trees seem more prominent in both the foreground and mid-ground where
grassy patches were previously more prominent



Mt Feathertop 1913 and 2013. Note very little difference in
position of upper treeline

Ngadju kala: fire management in woodlands

A new fire management report, lead by CSIRO scientist Dr Suzanne Prober, challenges common beliefs about Aboriginal burning practices in Australia.

Contrary to the common assumption that Aboriginal burning was widespread and frequent (e.g. Bill Gammage's book The Biggest Estate on Earth - see this YouTube video of Bill's view of the role of aboriginal burning), the report shows that the Ngadju community from south-western Australia were highly selective in where they burnt their country. Ngadju country covers a significant part of the region known as the Great Western Woodlands in south-western Australia. This region is nationally and internationally significant for its large, relatively intact expanses of eucalypt woodlands, shrublands, salt lake systems and mallee. When I was there a few years ago, I was blown away by the shear scale of the woodlands, and the beauty of the landscape. It's well-worth putting it on your itinerary when you're in Western Australia.

Ngadju used fire as a cultural tool for looking after rockholes and grassy areas, for protecting important cultural sites and special plants such as water trees, for access and hunting, and for encouraging grasses. The old growth woodlands were rarely burnt deliberately. Large-scale burning was not a common practice.

Some of the report’s key findings include:

• The extensive old growth woodlands were rarely burnt deliberately, because they take hundreds of years to recover.
• The extensive sandplain shrublands were only occasionally burnt with planned fire. Mostly they burnt naturally by wildfires that were allowed to take their course.
• Rather, Ngadju used fire as a cultural tool for keeping the country clear around rockholes, for encouraging grasses in open grasslands and mallee, and to smoke out animals when hunting. These fires were often small, around 1 ha.
• They also used fire to protect important cultural sites and special plants such as water trees; and to maintain access along walking tracks and in coastal shrublands.
• Other activities such as firewood collecting around the edges of woodlands and rockholes, and sweeping and scraping up litter around individual trees, were undertaken to help control wildfire.
• Ultimately these activities would have led to a fine-scale fire mosaic over the top of the natural vegetation mosaic.

The report, written to document Ngadju knowledge about fire in Ngadju country, can be

downloaded at http://www.csiro.au/Outcomes/Environment/Biodiversity/Ngadju-kala.  As a land management tool, fire obviously has a more select role in Ngadju country than in other regions of Australia such as the tropical savannah and spinifex country where large parts of the landscape are frequently burnt. It highlights the importance of interpreting anecdotal historical information about fire and landscape structure (e.g. settler's diaries, paintings, etc) through the lens of local (rather than regional) scale ecological processes.

 

Geographic distribution ecology

The Austral Grass Tree - what happens to it with climate
change won't be just about climate space. Grasstrees
tend to be found on impoverished soils, so
predicting response is not just about projecting
future suitability of the climate.
(Photo: Michele Kohout)

I've just come back from the annual meeting of the Ecological Society of Australia (held jointly with the New Zealand Ecological Society this year). I saw lots of talks with climate change as their key focus. Many of the talks were excellent, and included projecting/forecasting future species distributions using modelling approaches (SDMs). However, I also saw a glaring absence of field experiments in the general area of 'climate change biology'. I want to raise this apparent research gap here (and perhaps start a discussion amongst the scientific community about how (or if) we can change this).

Field transplant experiments are the most important missing information for understanding species movements under climate change. There is lots of modelling suggesting species ranges will shift, i.e.  observed climate envelopes (realized niches in environmental space) are being projected into the future on a large scale using SDMs but the problem is, we don't know what stops species from establishing populations beyond their range boundaries, i.e.  is climate the direct or indirect driver of species distributions?  I'd argue that field transplant experiments across geographical range boundaries are urgent to test this basic question. They are the reality-test for what sets range boundaries, and especially for when it is climate directly versus when it is a competitive milieu mediated by climate.

Why didn't I see much on this?

Well, such field experiments are difficult and time-consuming. It is crucial that such experiments involve transplanting species beyond the range, with and without amelioration of suspected limiting factors, both physical and biotic. Hence, they can get pretty complicated and pretty quickly! 

But such field experiments are also the essential reality test in relation to SDMs. The general point here is that we need to know not how plants grow where they do occur (this is ecophysiology), nor how much two species compete with each other where both occur (this is experimental community ecology) but rather, what happens when species move into new areas where they experience new species compliments, soils and pathogens (this is geographical distribution ecology).

Unfortunately, the experiments conducted in the 1970s-90s were the era of field experiments on competition and predation, with the overwhelming majority directed at measuring intensity of interactions within a geographical range, with very few at determining why range boundaries are where they are. Hence, we've lost a couple of decades already in trying to understand this crucial question.

I suspect that if we rely on chance decisions by individual research groups to undertake geographical distribution experiments, it's likely that several more decades will pass before a useful number will accumulate to inform the general question: what sets range boundaries? We really need to arrive at a situation within a decade or two where we have a moderately well-founded overview so we can far better understand the response of biota to massive shifts in climate.  Suppose optimistically that, say, 30 experiments a decade could be achieved worldwide. Can the research community collaborate to target them in such a way as to obtain generalization across species and boundary-types as efficiently as possible?

One way might be to assemble a global network with standardised protocols - much like has been done in the Nutrient Network (which tests top-down versus bottom-up controls on diversity in herbaceous ecosystems) or the International Tundra Experiment  (which tests the effect of warming on tundra and alpine vegetation). Both networks have simple protocols and clear questions and they encourage collaborative research across a large range of field sites. Hence, the power of the experiments lies in their spatial distribution with uniform methods.

I think this approach is one that could work to test range boundaries (once it is clear what sort of factors would need to be manipulated), and am in the process of writing a review paper on this idea with (hopefully) a rallying call for such experiments. Stay tuned....

Since when do elephants have trunks? Why climate science communication is failing us?

I had a really frustrating 'discussion' about the general topic of climate change today with a farmer from western Victoria. He was a great old bloke who has been on the land all his life. We got to talking about climate change and what evidence he saw for it. The fact that he can now grow wheat in an area once thought much too wet to do so made me think he'd recognise that things were changing. Surely there would be some reasonable explanation for this!!

Long droughts are pushing trees to the limit all over the world. Climate change
will affect rainfall patterns and intensify drought impacts in many areas.
(Photo: http://uanews.org/story/droughts-are-pushing-trees-limit)

Instead,  the general arguments for the changes he could acknowledge went along the lines of "climates have always changed, it's impossible for humans to influence complex systems like climate, scientists aren't even sure what is going on, why should we pay to reduce emissions because we (Australians) are a tiny contributor to global pollution, emission trading schemes will threaten jobs and wreck the economy, greens have an agenda that threatens the man on the land" etc, etc, etc.

His response is not unique. Far from it.

For me, it was frustrating because much of the discussion clearly related to belief systems. Sure, climate science is complex and not one that most people have a very good grasp on, but nor are other fields such as astrophysics, electrical engineering, dendrochronology, all topics the average Joe Blow doesn't necessarily have strong opinions on. Yet, in the case of climate change mitigation and adaptation, we've allowed non-informed/misinformed discussion to persist all the way from our political leaders through to the general public. This seems to be a failure of the science to adequately communicate why, how and where climate change is occurring. Regardless of what you believe, policy discussion and action should be based on evidence rather than self-interest, and it is then the job to tell people why you're acting the way you are.

I don't want to knock science communication per se. Indeed, in Australia, we are lucky enough to have the Climate Council, a superb means of disseminating scientific information about climate uncertainty, climate variability and climate extremes. However, I think there is a much greater problem and, after thinking about it for a while, I think it boils down to our general philosophy about learning and knowledge and its general role in society.




The Climate Council - a great source of independent
information about climate change in Australia.
see www.climatecouncil.org.au

Science communication is not just about communication of data and facts, although this certainly is immeasurably important. I think we should also view science communication as the task of teaching people enough scientific method and understanding to investigate and see the answer for themselves, and to understand the role of debate in that process. This clearly isn't happening very well in Australia.

Currently, much of the 'debate' I see is about the degree of persuasion that can be generated (by politicians, interest groups, etc) as opposed to informing a better scientific understanding of the problem and hence, the potential solutions. Hence, a genuine scientific understanding by the public, as well as informed decision-making by our politicians, almost appears an impossible dream at this stage.

What is currently missing in climate change discussions, like the one I had with the farmer, is anything on the specifics of the climate debate. This is probably the greatest failing of science communication but hints at a greater malaise about the role of science in society and how evidence-based decision making should be central to the debate. For instance, I use the following checklists in discussions with students and others when discussing climate change to see just what sort of understanding they have about the actual issue:

• Can people say what the debate is about, what the competing claims are, and what evidence they depend upon?

• What arguments do people come up with to support or criticise their positions?

• Can people outline the extent and limits of our knowledge, and comment in an informed way on what reasonably accessible further evidence could resolve some of those uncertainties?

By and large, the answers to the above are skeletal, non-existent, or just plain wrong. How could we have let this happen in a well-educated, secular society? I'm not sure, but in a culture where sport rules and the latest gossip can be newsworthy, clearly we have a problem of engagement with intelligence and ideas.

One thing puzzles me the most.

It seems odd to be discussing and debating climate change without ever discussing any of its contents. Sure, the information is complex, there is lots of it, and there is uncertainty (in model predictions, species-specific responses, temporal and spatial variation). But, an analogy might be drawn from another field of science - biology.

To me, the current public discourse about climate is like discussing the biology of elephants and never mentioning that they have a long trunk. Until this is recognised, I'm not sure we are going to make much progress on dealing with Australia's understanding of, and response to, climate change, at least in the short-term. And this is a pity.

Understanding how the climate is changing (including the consequences of this for weather extremes and hence, human health and wellbeing) should be one of the most important discussions to be had in every household across the country! And science (and scientists more generally) needs our society's support and encouragement (not contempt) so that it can meaningfully contribute to figuring out the best way forward.