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.

Monday, 24 October 2011

Science and land management

I'm a plant ecologist partly because it allows me to understand the natural world. But I'm also an ecologist because I want to see the management of that natural world done with the best possible scientific knowledge. This not only promotes the wise and sustainable use of natural resources, but ensures that appropriate management occurs in those areas where nature conservation is the primary aim.

Some of the best understanding of natural ecosystems in Australia can be found in the alpine grasslands, wetlands and heathlands of the Eastern Highlands. Scientific research has a long history in alpine Australia (dating back almost a century) so you'd think land management decisions would be informed by this research, i.e. the level of uncertainity about management actions is much lower there than elsewhere in the landscape where much less scientific research has been conducted.

The high mountain grasslands and wetlands of Victoria are most
extensive on the Bogong High Plains. This is where most of the scientific research
on impacts of disturbance have been conducted.
(Photo: John Morgan)
Cattle grazing impacts on range condition of high mountain ecosystems is one research area that has been particularly prominent. 

Maisie's Plots - started in 1946 by Maisie Fawcett from the School of Botany at Melbourne University - has been a pioneering study examining the effects of cattle grazing on alpine ecosystems. It shows clearly that bare ground is highest in grazed areas, which is not good news for erosion, and that bare ground favours regeneration of shrubs > forbs. The plots continue to be monitored till today, giving new insights on vegetation change in reponse to infrequent fire and climate change.

Maisie's Plots in 2005.
On the left, the area grazed by cattle for 100 ys.
On the right, the area unavailable to cattle since the 1940s.
Note the contrast in vegetation - composition and abundance is
very different inside the fence
(Photo: John Morgan)

More recently, Dick Williams and others tested the hypothesis that "alpine grazing reduces blazing" - in response to the idea that cattle are necessary to reduce fuel loads in alpine areas and prevent mega-fires. There wasn't much evidence that cattle grazing impacted on the extent and severity of landscape fires in 2003. Rather, the patterns of burning were mostly a consequence of fuel type. These studies (and many others), give managers, policy makers, and society a very solid basis on which to make informed decisions about the management of alpine lands. And it was such science that swayed governments to phase out cattle grazing from high mountain catchments over the last 30+ yrs - because of their detrimental effects of wetlands, vegetation cover, soil erosion potential and biodiversity values. Such rigorous assessment should be the standard for all land management activities.

But just last week, the Mountain Cattlemen's Association of Victoria trotted out their oft-stated claim that ''arguably suspect science'' surrounded the decision to remove cattle from the high mountains of Victoria. This is a baseless accusation given the science that has occurred there over six decades has followed normal scientific practices (development of hypotheses, replication, controls, rigorous measurements, etc), as well as being peer-reviewed before publication. Such statements need to be held to account - because without challenge, they can gain some level of credibility and undermine / erode confidence in the scientific process.

 What's often not understood is that scientists are inherently conservative beasts - before proclaiming "effects" of X on Y, they have tested their ideas through replicated observation and experiment, considered alternative hypotheses, and  used statistical inference to interpret their findings. They do this because they want to make sure that they don't proclaim significant effects when none occur - a false positive. This is called a Type 1 error in statistical terms.

Statements like those of the MCAV highlights a mis-understanding of how science works and, more generally, its role in society. Science is an evidence-based discipline, and allows degrees of 'certainty' to be proclaimed - e.g. we are 95% sure that adding nitrogen to native grasslands in Australia promotes invasion by exotic species. Hence, it's generally not a good idea to spread nitrogen around if you want to conserve diverse native grasslands. There will be exceptions to this (in our field, we talk about how effects may be 'contingent' on site factors), but this should not undermine the general confidence we have in making these predictions.

However, in society, people are often inclined to believe what they want, with or without evidence. This is because religion, politics and upbringing all affect the way that people view their world. It makes the likelihood of a fruitful scientific debate on sustainable land management difficult. And how might we argue the case for acting on climate change in such an environment? Discussing the environmental impacts of an increasing population size in Australia (predicted to hit 35 million by 2050) is another topic that springs to mind where science should have an integral input into the debate.

More than 300 years after the Enlightenment ushered in the Age of Reason, superstition and belief still vie with rationality; the scientific method remains ill understood and we are as likely to believe what our peers say as our scientists. In debates we pick sides and become entrenched in positions, rather than weighing up the evidence. So how do we change this idea that our science is peripheral to good management when (I'd argue) it should be front & centre?

Certainly not by giving up! One of the best things we can do, as scientists, is to point out errors of fact and logic that may be promoted in the mainstream media cycle. And, crucially, to accept that conservation biology is not purely a scientific endeavour. [Read John Lawton's excellent article on "The science and non-science of conservation biology" in Oikos 79: 3-5 for an interesting take on this]. It involves society and we need to much better engage with that society (i.e. the users and decision-makers of the land) if we are to convince them of the methods (and merits) of informed land use. It won't be as simple as that, but I've found that if you take the time to explain your science to the average man on the street (or land manager), he's usually really quite receptive. In many cases, it's about making science (and nature more generally) relevant to people who might not really understand how and why we do what we do.

Thursday, 20 October 2011

Open-source Ecology takes Root

A nice little commentary piece on the Nutrient Network Project I am involved in has just been published in Science. You can find it here. It highlights how collaboration, using very simple experiments, can help answer some of the most important questions in ecology. Hopefully, it also highlights that collaboration is exciting, and can allow ecologists (both junior and senior) to contribute to really important science, even if they haven't pulled in huge research grants.

Alpine grasslands at Falls Creek: one of the NutNet sites exaiming
top-down versus bottom-up controls on species diversity in grasslands across the globe.
(Photo: John Morgan)

Tuesday, 18 October 2011

Ecological divides

Fencelines provide excellent opportunities to do comparative ecology.

Across southern Australia, livestock grazing has been so widespread and intense that it's transformed the natural grassy ecosystems, sometimes beyond recognition. Early settlers were drawn to the vast grassy plains of the lowlands, as well as the drought relief that the alpine high plains provided. For ecosystems that evolved in the absence of large, hooved, congregating animals, it's no wonder that changes in the native vegetation were recorded within five or so years of occupation by europeans. In many cases, we can only dream of what the original ecosystems might have looked like. Early paintings provide some insights, particularly about the structure of the vegetation and perhaps some of the dominant tree species. For example, the image below shows that the Yanakie Isthmus at Wilsons Promontory in the 1870s was undoubtedly a grassy woodland at the time of settlement, and extensive at that. Today, the Isthmus is covered in shrubs and hardly a blade of grass can be found, a consequence of 100 yrs of stock grazing and fire exclusion.

From Lookout Hill, towards Mt Latrobe.The trees here are probably She Oaks (Allocasuarina verticillata).
Painted by John Black Henderson, about 1870. (Image provided by Jim Whelan)
Fenceline comparisons, however, provide much more detailed information about the effects of historical and current regimes on the composition of native vegetation. In some cases, the fences went up in the very early days of settlement (around cemeteries, along railway lines, and to demarcate travelling stock routes), preventing the ecological transformation that occurred throughout the remainder of the landscape that was to be grazed. It's no wonder they have been used extensively in ecology as "natural experiments".

To illustrate the importance of fenceline comparisons, I've been just looking at the distribution of C4 grasses on the riverine plains of northern Victoria with a view to thinking about how to restore and manage these endangered ecosystems. Currently, grasslands here are dominated by C3 grasses such as Wallaby Grass and Spear Grass, with a wide variety of annual and perennial intertussock herbs. C4 grasses are very rare (despite their implied importance in the pre-european flora). The current structural and compositional values are being managed by status quo management - using sheep grazing - based on the idea that the vegetation we see today is a product of its recent grazing history and hence, this is the best way to manage it to maintain those values. But what elements might be negatively affected by such a regime?

At Terrick Terrick National Park, there's a little gem of an unused laneway that runs for perhaps 1.5 km. It's no more than 20 m wide and it adjoins large paddocks with native grasslands that have been grazed for a century, as well as cropped at some stage (as evidenced by the cultivation lines). Such a laneway offers an amazing insight into what grasslands might have looked like in the absence of grazing.

Land use on the Northern Plains of Victoria. This native grassland shows the typical
signs of having been 'used' before it was conserved. There are cropping lines, obvious effects
 of water points on sheep movements. And, at the top of the picture, a laneway - different
in colour from much of the vegetation. Is this because it supports a different flora?
(Photo: Google Earth image)

Two things strike me about the fenceline comparison here:
1) in the ungrazed area (left), C4 grasses that are incredibly uncommon in the grazed grasslands - such as Enteropogon (Spider Grass) - are super abundant (and co-dominate with other C4 grasses). Strikingly, C3 grasses are almost absent from the ungrazed area (yet are ubiquitous in the grazed area). Hence, functionally, the laneway grassland is a summer-active one, not a winter-active grassland as now dominates most of the landscape. This is a profound change.
2) unsurprisingly, in the ungrazed laneway, there are lots of sub-shrubs and herbs which are absent from the grazed areas. Maireana and Atriplex, in particular, only exist at high abundance where grazing has been minimal.

These are not new insights. Changes in species composition due to grazing have been recorded many times before in Australia. This is often due to differences in palatability. But, it does point to some key questions.

Does grazing promote C3 grasses that have a regeneration niche dependent on disturbance? It is thought that the C4 grasses regenerate better where the ground is covered in plant litter, but this is removed in grazed areas, potentially favouring Spear Grasses. Perhaps this is why there are no Spear Grasses in the laneway. This needs to be experimentally tested.

Can status quo management ever allow the system to recover poorly represented components of the original flora? The laneway is so different that it is clear that ongoing grazing by sheep maintains different vegetation states across a fenceline. It does this because it prevents the C4 components (and other subshrubs & herbs) from transitioning back into the system. If every grassland is managed in the same way on the northertn plains, then we are conserving a subset of the original flora. And a subset of the ecosystem services and functions performed by such a flora.

It would be incredibly useful to assess the plant trait distributions of species found in the laneway and adjoining grazed grasslands. Does grazing maintain species richness, but at the expense of functional diversity? Are we causing a functional homogenization of the grasslands in our pursuit of conserving exisiting values?

I've highlighted just how important fencing experiments can be to show that vegetation patterns are affected by management history. Providing a mechanistic understanding of the changes that occur, however, has been less well demonstrated. I hope to fill in these gaps soon. Till next time....

Sunday, 2 October 2011

Colder plants in a warmer world?

I'm keen on cross-country skiing. I guess it's an extension of one of my other great loves: bushwalking. I can think of almost nothing better than strapping on some skis, packing the tent and shuffling out across the high plains of the Australian alps to camp in the snow on some distant peak.

I particlarly love spring skiing - it's warm (so I get to ski in shorts!), the days are long, the snow is hard in the morning - which makes for some fast downhill runs, and there usually aren't as many people around. I was hoping to get one final ski in this season, but like many years (perhaps seven out of the last ten), it's been another disappointing year for snow in Australia. That doesn't stop the ski resorts here from charging top dollar, but that's another story.......

The SnowCams at Mt Buller don't lie! Even at one of Victoria's highest
peaks (>1800m), there ain't much white stuff and hasn't been all winter

What we are seeing now is probably a window into the future.

About a decade ago, Kevin Hennessey and collegues at the CSIRO modelled the potential distribution of snowcover at 2050 and showed that,  under 'high warming' scenarios, very few mountains in Australia would sustain snowcover for >90 days. I think we won't have to wait till 2050 for that to become a reality. This will likely have lots of consequences in the Australian Alps such as (a) there being less water released slowly in the spring thaw (with resultant greater stream surges with potential for downslope flooding) and (b) lower albido.

One of the biological consequences that hasn't really got much attention yet is how less snowcover will affect those plants (and animals) that rely on snow for protection from the cold. Generally speaking, snow is a magnificent insulator against the cold. In the sub-nivean space (the interface between snow and vegetation), it rarely drops below zero degrees. Hence, plants there are not exposed to extreme cold (frost) and can even continue to grow over winter in some cases. But with less snow, there will be less of an insulating blanket, and this will invariably melt earlier each year, exposing plants to extremes of cold they perhaps are incapable of resisting. Might alpine plants in a warmer world actually be more susceptible to the cold?

Susanna Venn, Janice Lord and I have been investigating the frost sensitivity of alpine plants with this question in mind. We've been assessing the early spring frost tolerance of a range of alpine plants to determine just how they might react to earlier snowmelt.

For those (mostly woody) species that occur on wind-exposed ridges where the snow rarely settles, it is clear they are very cold tolerant early in the season. This is because they are rarely insulated from winter cold. The Alpine Star Bush (Asterolasia trymaloides), for instance, has an LD50 of -17.6 deg C in the weeks after the spring thaw. Lethal temperatures were considered those at which 50% damage occurred to the photosynthetic apparatus in leaf samples. Pimelea axiflora is even more cold tolerant - it's LD50 is -18.7 deg C.

Brachyscome nivalis - less cold tolerant than many alpine shrubs
(Phto: John Morgan)
By contrast, species (mostly herbs) that are normally deep under snow for the entire winter and hence protected from the extremes of cold, and which don't melt out till mid-summer, exhibit much less cold tolerance early in the season. Brachyscome nivalis, for instance, has an LD50 of just -7.0 deg C when it was removed from snow early in the spring. This hints that it might be sensitive to early melting if that meltout coincides with very cold spring temperatures. To avoid frost damage, the species would likely need to remain in areas of late melting snow (as it currently does), areas which are predicted to decline in extent over the coming decades.

So, while there will be opportunities for extended growing seasons in the high mountains of Australia, it is likely that frost sensitivity may constrain some species. This needs to be ascertained for a far larger number of species than we have examined so far.