Weeds are relentlessly marching into the Australian Alps!

This is the conclusion I have to draw based on lots of new evidence we have been accumulating these last two summers. Alpine areas are currently amongst the least invaded ecosystems in Australia and this has generally been thought to be because the environment is too harsh for many introduced species to survive, hence limiting their establishment. I'm coming to the conclusion that the current low number of species is more a reflection of the fact that many exotic species have yet to arrive there.



MIREN features 11 core mountain regions that
 participate in standardized baseline screening and monitoring.

Our research has shown that the flora and fauna of the Australian Alps is rapidly changing. My Lab is part of the Mountain Invasion Research Network (MIREN), an international collaborative effort to document patterns and processes of invasion into mountain ecosystems. Using standardised survey protocols (mostly using quadrats placed from lowlands to mountain tops), we have now shown that many species have made the jump from the lowlands to the alpine regions. In some cases, this has occurred because they have been deliberately introduced into ski resorts. The introduction and spread of Orange Hawkweed is a good example of this.

Many new arrivals, however, have moved into the mountains by using roadsides as corridors for dispersal. Some, such as Chilean Needle Grass, have never been seen before in the alps until their detection on roadsides near Falls Creek in 2013. Others, such as Sweet Vernal Grass and St John’s Wort, are rapidly expanding their range, using roadsides and walking trails as initial points of introduction into native vegetation.

In general, the number of weeds on roadsides does decline as you move up mountains. You can see  this pattern here - a summary of all plots sampled in the Victorian Alps in 2013.

But don't be fooled. My collaborator Keith McDougall, working in the Kosciuszko National Park, found 25 new species on roadsides when he sampled the same plots five years apart, hinting that the ongoing propagule pressure from vectors such as cars, combined with changes in regional climate, is transforming mountain road verges at incredible rates. Sure, many of these species have not yet moved into the adjoining native vegetation. But it just may be a matter of time.

This figure, using MIREN data from the Victorian transects, shows how far some weeds have moved off roadsides. It's not an insubstantial encroachment of exotic species.

 

It's not all bad news though.

Red-led Grass is a native grass found on roadsides leading into
high mountain ecosystems. All of its 'natural' distribution
in Victoria is low elevation plains grassland and woodland.

Some native species also seem to be using roadsides to hitch a ride up mountains. Red-leg Grass (Bothriochloa macra), a native C4 grass of the surrounding lowland plains, for example, has been recorded at several mountain roadside sites well above any known location in state databases (i.e., growing up to 800 m above known populations). Is this a 'new' weed, albeit native? It certainly looks like its dispersal is linked to vehicles but it is also likely that recent changes in low temperatures (and perhaps precipitation) play a role.

The movement of natives up mountains is interesting and entirely inevitable; after all, our basic understanding of climate change impacts is that species will migrate pole-wards and up mountains. This example, however, showcases how humans are likely to have facilitated the process and how (mostly) it'll go on undetected.  And, in the bigger scheme of things, it illustrates that native ecosystems will re-assemble in the coming century whether we like it or not.


Further reading about MIREN and mountain invasions:

Kueffer et al. (2014) The Mountain Invasion Research Network (MIREN) - linking local and global scales for addressing an ecological consequence of global change. GAIA 23/3: 263-265.

Pauchard et al. (2009) Ain't no mountain high enough: plant invasions reaching new elevations. Frontiers in Ecology and the Environment 7: 479-486.

This work is supported by funding from the Long-term Ecological Research Network (LTERN) and was conducted by members of the La Trobe University Research Centre for Applied Alpine Ecology.

Hyper-emergence in eucalypts

Tropical savanna in the Northern Territory
(Photo: John Morgan)
 

Sub-tropical rainforest, Dorrigo National Park
(Photo: John Morgan)

Q: What's the most obvious difference between a rainforest you'd find in the tropics and a eucalypt forest you might find in temperate areas?

The difference between these two is so obvious, most of us don't even notice it.

And it struck me recently that the explanations for it are also poorly understood.




Mountain Ash - Eucalyptus regnans
The tallest flowering tree on the planet.
(Photo: John Morgan, Wallaby Creek, 2006)

One of the most obvious differences is that Eucalyptus (and this would include some closely related genera such as Corymbia), are characteristically emergent trees of many vegetation types in Australia. Typically, they are considerably taller than all other species in these communities, often by an order of magnitude or two. As such, the trees tower over all the other plants. Rainforests, by contrast, tend not to have such obvious tiering or separation of the canopy and the mid-under storey, with lots of different species comprising the canopy. Emergent trees, when they do occur, do not tower over the rest of the plant community. This seems a really obvious distinction, but have you ever stopped and asked "why"?

A recent review sheds some light on why eucalypts grow so tall.

Tng et al. (2012) New Phytologist 196: 1001-1014, while focusing on the reasons for the evolution and occurrence of gigantic eucalypts (i.e. those species that grow >70 m tall, a fascinating topic for another post),  highlight that 'hyper-emergence' of eucalypts is a trait that extends across climates and clades and can be found in many Australian vegetation types such as heath, mallee, dry sclerophyll, subalpine and savannah communities. In some cases, some giant eucalypt trees are >60 m taller than the underlying canopy. The nearly ubiquitous nature of hyper-emergence in eucalypts suggests that this trait is an ancestral feature of the eucalypt lineages, and if this is true, would have arisen >60 million years ago!

In some respects, growing really tall above your competitors seems like a dumb idea. There's the risk of wind damage (or worse still, lightning strike!), tall trees need to sustain their own weight once bent, there's a lot of investment into woody structures that are diverted away from reproduction, and of course there is the not insubstantial problem of getting water up to great heights. So, why would trees - and eucalypts in particular - bother growing so tall? What are the benefits of far exceeding the heights of competitors?

Alpine Ash (E. delegatensis) are hyper-emergent
trees at high altitudes in the Australian Alps
(Photo: John Morgan, near Mt Hotham)

Tng et al. suggest a couple of reasons, but clearly this is an area where more research is needed.

First, tall trees tend to have very rapid early growth (relative to lots of other woody plants in the same community), allowing them to escape a 'fire trap' such that this growth would allow saplings (or resprouts) to reach heights that allow them to avoid the effects of high intensity ground fires. Such processes could apply to eucalypts in general (e.g. such as those of savannah and forest) but may be less applicable to eucalypts where fire return intervals are very long (decades to centuries). Indeed, in Mountain Ash forest, infrequent but high intensity canopy fires are actually necessary for stand replacement.

Second, most eucalypts are shade-intolerant. Intense intra- and inter-specific competition provides a strong selection pressure for tall growth, hence allowing them to overtop their neighbours. By overtopping slower growing, shade-tolerant trees, often quickly after disturbance, early reproductive maturity can be assured.

While both explanations undoubtedly play a role, they are not particularly satisfactory answers when asking the question "why grow so much taller than all the other plants in your community"? I think this is a fascinating topic that really needs a bit more thought. So next time you're in the bush, marvel at the eucalypts that undoubtedly overtop all else and ponder why this might be so.


Further reading
Tng et al. (2012) Giant eucalypts - globally unique fire-adapted rain-forest trees? New Phytologist 196: 1001-1014.
Larjavaara (2014) The world's tallest trees grow in thermally similar climates. New Phytologist 202: 344-349.





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Endemic plant species on restricted soil types: 'early victims' or 'hardy survivors' of climate change?

One of the greatest challenges that land managers face today is anticipating how climate change will affect the diversity and composition of ecological communities to develop effective strategies for adaptation and mitigation. The direct effects of climate change on species via changes in temperature and precipitation have been the focus of many studies. Many conclude that altitudinal and latitudinal shifts in distribution will be necessary to survive the impacts of predicted climate change. 

 

Little attention, however, has been given to how plant species on 'restricted' soil (i.e. very infertile) will respond to climate change. Here, suitable habitats for such species are patchily distributed, and the dispersal distances required to move to newly suitable habitat are large, making successful migration unlikely. Are species confined to low-nutrient soils, which may reflect their tolerance of such conditions and intolerance of other biotic factors such as competition, particularly vulnerable to climate change?  Some studies suggest that soil specialists may be at less risk than species on 'normal' soils due to their stress-tolerant functional traits, but there is also contrary evidence.

 



Conceptual model of how present and future climate changes will affect (a) soil generalist and (b) soil specialist species differentially. Blue represents the current range of a species, Green is the future range of a species and Red is the area of overlap between the current and future ranges. Patchy suitable habitat for the soil specialist creates fewer colonization opportunities among the current and future ranges than for the soil generalist with contiguous suitable habitat.

Image: Damschen et al. (2012) Journal of Ecology 100: 1122-1130.



Plant communities on low-nutrient soils have two distinctive attributes that may cause them to respond uniquely to climate change, and I don't think we've really thought about these factors as they pertain to climate change responses.

 

First, they are often found in discrete areas making them more spatially isolated from one another than species on ‘normal’ soils that tend to be more contiguous. Hence, this spatial isolation may make it much more difficult for soil-specialist species to successfully migrate under climate change because suitable soils are isolated (or embedded in a hostile matrix to borrow an analogy from landscape ecology).

 

Second, because these species are on unproductive substrates, they may differ from communities on ‘normal soils’ in terms of limiting resources, functional traits, and the relative importance of disturbance, competition and other ecological processes. Plants in these special soil habitats often have traits associated with tolerance of drought and nutrient-limitation [e.g. small stature, low-specific leaf area (SLA), high allocation to roots relative to shoots] because nutrient availability is limited, water can be scarce, and soils may have additional unusual chemistries (e.g. particularly acidic pH). Special soil communities are often more strongly water-limited than others; therefore, they may be especially responsive to changes in available precipitation. On the other hand, because plants on special soils already have adaptations for stress tolerance, they may be particularly well-suited to withstand climatic changes.



Prostanthera galbraithiae (Wellington Mint-bush) is an erect to

spreading small shrub and is restricted to sandy soils of the Holey Plains State Park, Victoria

Asking questions about the fate of soil specialists in response to climate change is important for plant species such as the Wellington Mint Bush (Prostanthera galbraithiae), a vulnerable species in Australia. The species is endemic to a very small area of the Gippsland region of Victoria, restricted to sandy podzol soils typically low in macronutrients (especially N, P and K) and subject to long periods of soil moisture stress. Importantly, the sandy, nutrient-poor soils where Wellington Mint-bush occurs are restricted and embedded in a matrix of clay-based, more fertile soil types.

What are the potential responses to climate change of endemic plant species like the Wellington Mint-bush when soil factors appear to limit their current distribution?



To understand the role of climate factors on the fitness of soil specialists, it is necessary to compare the plasticity to water and temperature stress of the endemic Mint-bush to that of more widepread species (such as Prostanthera lasianthos, P. rotundifolia) to test the hypothesis that soil specialists are already well-adapted to environmental stress and hence, they may be particularly well-adapted to withstand climatic changes. Such studies, and life history study more generally, allows us to understand how plants respond to stress, and provides a powerful tool for making informed decisions about which species may need active intervention to ensure their persistence.

For species found in highly variable environments (such as those areas with frequent but unpredictable drought) where soil factors accentuate the magnitude of drought, a history of climate variability might confer rather general plasticity or tolerance of  future climate variation. Coupled with having to persist on infertile soils, some species might show more resilience to change in climate than those species from much more stable/predictable climates (i.e. where factors such as rainfall are more evenly distributed through the year) because they already have to exhibit 'stress-tolerance' to survive their specialised soils. Hence, it would be useful to ask whether range-restricted, soil specialists like the Wellington Mint-bush are more plastic in their response to climate variability than widespread species (where local adaptation might have developed – i.e. the ‘provenance’ concept), or are they simply better adapted to environmental stress.  

 

Managing sites for biodiversity based on plot-level data

A simple, but powerful realisation hit me the other day while I was away on a field course with my 3rd Year Botany students. We went to Cape Conran in the east of Victoria to study fire and diversity relationships in sandplain heathlands. We set the students some questions for which they had to design a research project. They did a great job, so much so that it made me think about how we use scientific data to inform conservation management actions.

One of the questions we asked was: what is the relationship between species number and time-since-last-fire? This is a very 'old' question in ecology, with lots of evidence that species number initially increases after fire, then plateaus off, before declining with increasing time. As such, it is recommended that to maintain diversity in heathlands, they need to be burnt at frequent intervals. Reading the literature, it is evident that fire return intervals of 10-25 years are recommended.



Botanists often quantify the number of species in quadrats of fixed size.
This is SPECIES DENSITY. Often only one or two quadrats per 'site' are sampled. An individual site here is
a heathland with a known date of  Year-Since-Last-Fire

 

Land managers take advice about the ways in which to manage biodiversity from scientists, so it is important that the advice we give is based on solid data from well-executed studies.

At Cape Conran, we asked whether species number declines with long fire-free intervals to test the well-established understanding of heathland ecology. But we decided to take a different approach to that which is usually employed.

In many of the 'fire in heathland' papers I read, I see that botanists compare the number of species in a quadrat (this is known as Species Density) across sites with known fire histories. Importantly, in these studies it is usual that the same sized quadrat is employed across sites to generate Species Density estimates. But this might be a flawed approach. Imagine you set up a 4 x 4 m quadrat in recently-burnt heathland. The plants are very small and many of them can 'pack' into the quadrat. As plants age, they become bigger and hence, it is likely that fewer of them will fit into your 4 x 4 m quadrat. In long-unburnt heathland, heath species are as large as they can grow and even fewer will fit into your (what now seems small) quadrat.

So, while Species Density might inevitably decline with time-since-fire in your small quadrat, this is not the same as saying Species Richness declines across the site. Species Richness is the number of species you find in a defined site - in our case, a heathland - and it is this scale that a manager manages. Hence, is there a mismatch between the scale of evidence that botanists have used to assess fire impacts (the plot level) and what managers actually need to know - how do I manage heathland to maintain their diversity?

To answer this question, we set out to sample Species Richness across sites that contrasted in time-since-fire. We used lots of small 1 m2 quadrats (n = 25) at each of three sites (that differed in time-since-fire: recent to long-unburnt) rather than relying on one or two big quadrats as is usually done. These were spread out across each heathland and all species were recorded. The results were VERY surprising!




Here, students are also quantifying species density
in smaller quadrats, but doing lots
of them across a site

As expected, Species Density was highest in the most recently-burned areas compared to long-unburnt areas (15 vs. 8 species per m2). But then it got interesting. The total number of species observed in each site across our 25 quadrats was the same - 39 (all of them native). So, despite there being many more species in the small quadrats in the recently burned areas, unburnt areas supported the same number of species across the site. Yes, they were 'rarer' and some were different species, but if the aim was to maintain species richness at the Site Level, the level at which managers would be most interested, then the need for fire was not so clear.

And, when using some fancy statistical techniques to assess how much more biodiversity would be present if we had sampled more quadrats (the procedure is called 'rarefaction'), we actually expected more species in the long-unburnt heathland than the recently-burned heathland (60 vs. 41).

It became apparent that frequent fire might actually hold-up succession of sandplain heathland to more complex, diverse systems rather than maintain it. Frequent fire would likely knock out species that have long primary juvenile periods or that take time to colonise after fire. Far from allowing such species to be members of the community, frequent fire might reduce spatial heterogeneity and hence, reduce habitat complexity. Such thinking hasn't been applied to heathland ecology before in south-east Australia and while it is too early to suggest we change our current practices (of frequent fire), this student research hints that maybe a rethink is in order.

And, as I said at the start, it highlights that the relationship between Plot-level data and Site-level responses are not always as clear-cut as might be imagined. Stay tuned........

Thanks to Luke O'Loughlin, David Cameron and Botany students Holly Fiske, Nicole Baboucek, Tony Hampton, Jasmine Thum, Darragh O'Sullivan and Kate McWhinney for collecting and interpreting this interesting dataset from the annual Botany 3 undergraduate trip to Cape Conran.

New study points to the global significance of the Plains-wanderer

Can you spot Australia's most unique bird?
Terrick Terrick National Park
Photo: John Morgan

The Plains-wanderer has for some time been known to be a member of Australia’s ancient avifauna and its nearest, albeit distant, relatives are seedsnipe from South America.  It is the sole member of a Family of birds called the Pedionomidae. It's a species typically confined to native grassland habitats in eastern Australia and, unfortunately, one of the most endangered species of those grasslands. It should be a flagship for conservation and new research tells us why!

Recently, Jetz et al. (2014) published a major review of the world’s 9,993 recognised bird species to determine which species we can least afford to lose in the current extinction crisis if maximum global phylogenetic diversity is to be maintained.  Phylogenetic diversity is a measure of biodiversity which incorporates phylogenetic difference between species and phylogenetic analyses have become essential to research on the evolutionary tree of life. The concept of phylogenetic diversity has been rapidly adopted in conservation planning.

Jetz et al. (2014) developed a hierarchy based on how isolated a species is on the phylogenetic tree which they termed ‘evolutionary distinctness’.  They also included global geographic range, and global endangerment in their metrics.  The summary metric that Jetz et al. (2014) used to rank the world’s birds combines evolutionary distinctness and extinction risk. 

By their calculation, the Plains-wanderer is ranked:
 #1 among Australian birds and #4 in the world!!

As such, these analyses highlight we can ill-afford to lose the species, yet current data suggest that significant declines are being observed, and it's not entirely clear why.

The two strongholds of the Plains-wanderer are the semi-arid (or xeric) native grasslands of the Riverina region of NSW and Victoria’s Northern Plains.  Monitoring in NSW during 2001-2012 has found that the population size has declined by 75% during droughts, then recovered slightly during benign years, and was then recorded at record low levels during the very wet years of 2011-12.  The population has remained at very low levels for over a decade, and this is cause for considerable concern. In Victoria there has been monitoring on Terrick Terrick NP and nearby private land over five years (2010-14).  Numbers declined by >90% during 2011-12 in the wet years (perhaps because breeding was negatively affected, while thickening of grasslands has reduced occupyable habitat) and the numbers have remained at historically low levels.

If ever there was a need to monitor the dynamics of a species of conservation concern, whilst also monitoring its habitat suitability and key determinants of mortality risk (e.g. predation),  then the Plains-wanderer would seem an essential candidate species. Good, basic scientific research is needed to answer simple questions: how long do birds live; are population dynamics cyclic; can suitable habitat be successfully created from scatch? In some respects, a metric of the success of grassland conservation and management will be that species like the Plains-wanderers can be maintained in their habitat, and that their numbers grow rather than decline.

Thanks to David Baker-Gabb for alerting me to the evolutionary distinctiveness of the Plains Wanderer, and for providing information on the population trends of this species.

Reference

Jetz, W, Thomas, G H, Joy, J B, Redding, D W, Haartmann, K and Mooers, A.  2014.  Global distribution and conservation of evolutionary distinctness in birds.  Current Biology (2014), http://dx.doi.org/10.1016/j.cub.2014.03.011.

A new population curve for prehistoric Australia

The arrival of Aboriginal people in Australia marked an important change in the continent's ecology. The loss of the mega-fauna and a rise in the use of fire are common themes that resonate when discussing the role of Aboriginal people in shaping the nature of Australia.

Up until now, most of the discussion has been about when aboriginal people arrived. The numbers fluctuate between 40,000 and 100,000 yrs ago, with a convergence of opinion in recent years (because of better carbon dating techniques) that it was probably about 52,000 yrs BP.

An interesting paper by Williams take this insight one step further.

Using radiocarbon dating techniques on >1700 sites from all over Australia, Williams has tried to reconstruct/assess population growth rates in Australia up until the time of European contact.

Using some modelling assumptions about the initial founder effect (that is, how many people first colonised), he interprets three key things:

1) Australia was settled by thousands, not just a handful, of humans, suggesting deliberate rather than accidental colonisation of the continent. The research suggests that it probably would have taken 1000 to 3000 people to reach the numbers of Aboriginal people observed at time of European contact.
2) the population size grew very slowly - constrained by glacial periods. It wasn't until the Holocene (from about 10,000 yrs BP) that the population grew substantially. The study shows during the glacial maximum 18,000 to 21,000 years ago, the population fell dramatically. The data suggests 60% of the population was lost during this time, a period of extreme dry and cold. It took 9000 years for the population to recover to the same levels.
3) the maximum population size before European settlement was approx. 1.2 M people (assuming a founder population of 1000-2000). This occurred only 500 years ago.



Distribution of archaeological sites contributing radiocarbon data to the study by Williams.
You can see there is a pretty good coverage across Australia.



You can see this population reconstruction clearly here in this figure from the paper. The effects of 'founder size' (how many people might have first colonised Australia) has a big effect on population size at the time of European contact, as does climate. The two graphs show the outcomes based on different model assumptions - they give pretty much the same results. They suggest that population growth really took off at about 12,000 yrs BP; this corresponds with increasing climate stability

This paper (along with others - see here) hints that the big changes in vegetation and mega-fauna extinctions observed in the last 50,000 yrs were probably driven by climate. Landscape burning by Aboriginal people has been linked to significant changes in the geographical range and demographic structure of many vegetation types but there is now an emerging lack of congruence between human activity and fire records during the period 20-40 kya. During a period of consistently low human populations, as posited by Williams, it is difficult to reconcile how Aboriginal people could have had the profound impacts that have been speculated by many.

I can't vouch for the veracity of the work reported by Williams, but it provides interesting food for thought when interpreting the recent history of Australia.


References
Williams (2013) A new population curve for prehistoric Australia. Proceedings of the Royal Society B 280, 20130486.

Sakaguchi et al. (2013) Climate, not Aboriginal landscape burning, controlled the historical demography and distribution of fire-sensitive conifer populations across Australia. Proceedings of the Royal Society B 280: 20132182

Ecological Rants

I just discovered Charley Krebs Blog page called "Ecological Rants". It's worth a look.

Krebs is an excellent ecologist who has written one of the best textbooks on ecology (Ecology: The Experimental Analysis of Distribution and Abundance) and, because of his age, has been around long-enough to have seen the field both stagnate, get bogged down and ultimately, make some massive gains about the understanding of the natural world. I've always thought his insights were interesting, even if I don't always agree with him.

There's excellent 'rants' about:
- answering unanswerable questions
- when academics should retire
- conservative politics and science
- biodiversity research
- science and money
- what bureaucrats need to do to let scientists get on with their job

I really like Charley's approach (elder statesman type of thing) and it's great to see (once again) how Blogs can get scientists to reach out to other scientists (and the public) beyond their academic publications.

Shrubs in woodlands - directional or cyclic?

One of the things that ecologists have noticed in (some) grassy woodlands in southern Australia over the last two decades is that woody cover has been on the rise. This can take the form of increases in shrubs (such as Leptospermum spp., Acacia spp.), or dense regeneration of trees.

My own work (and that of my students and other scientists) show this increase might be due to changes in management (such as the removal of stock grazing from long-grazed forests upon reservation for nature conservation), altered fire regimes (usually a decline or exclusion of fire), overgrazing by native and exotic herbivores (that reduce competition from the ground-layer vegetation, as well as encouraging unpalatable species at the expense of palatable ones), and potentially even changes in atmospheric CO2 levels that favour woody plants over grasses.

Increases in woody plants have been recorded at several locations in southern Australia. This increase has generally been thought to be a uni-directional change that requires management intervention to alter this trajectory. So, at Wilsons Promontory National Park for instance, dense thickets of native Tea Tree that have established in swale grasslands and woodlands over the last 40 years are now being actively managed by carefully timed fire to open up the closed shrublands to benefit biodiversity and amenity.

Parks Victoria staff undertaking a burn to manage Coast Tea Tree (Leptospermum laevigatum) at Wilson's Promontory NP
(Photo: Greg McCarthy)

Just the other day, however, I saw evidence that woody plant encroachment isn't always uni-directional.

Herb-rich woodlands at Langi Ghiran
in mid-winter, before flowering.

At Langi Ghiran, there are fabulous herb-rich woodlands. Spring is a sight to behold - indeed, some of the highest species richness levels in Australia have been recorded there. Shrubs appear to be localised and generally sparse.

Hedge Wattle (Acacia paradoxa), a shrub native to the system, began spreading about a decade ago at this site and forming thickets. I'm not sure why it did this - was it climatically stimulated, was there a change in grazing pressure form native herbivores, was this a response to rising CO2?

It established prolifically in the inter-tree gaps, which are common in this woodland (and support much of the plant diversity), and establishes in the absence of fire. It also seems pretty unpalatable to the resident kangaroos and wallabies. I began to think that the end game here would be dense stands of wattle, a decline in diversity, and a landscape transformed visually.

However, when I last visited, the scene had changed a little bit.

Hedge Wattle - the dead looking stuff in the centre of the image - at
Langi Ghiran, 22nd June 2014.

Across 10's of hectares, Hedge Wattle had died, or was senescing. I'm pretty sure this was not because of old age - most shrubs are (and this is just a guess) less than 15 yrs old. We know from work by my Honours student Julia Franco that Hedge Wattles can live for five decades.

Where plants were not quite dead, the phyllodes were brown and desiccated and clearly the individuals looked like they were on the way out.

I first noticed this browning off in summer after a hot and dry spell. Now, in mid-winter, there seems no signs of recovery. This hints (to me) that drought has probably played a key role in the population dynamics of Hedge Wattle at this site. It hints that the population might be cyclical - assuming that the rise and fall of Hedge Wattle has occurred before, but just gone un-noticed.

If this is the case, it suggests a few important lessons:
- long-term observations can help decipher directional versus cyclical patterns in nature.
- if drought is at play here, was this drought 'extreme' and hence, might we expect its frequency (and potential effects) to increase over time?
- drought plays a key role in the dynamics of many woody plant populations but its effects are sometimes under-appreciated.

What else might be going on?? It's probably important to survey Hedge Wattle at Langi Ghiran to see if mortality is linked to particular aspects, slopes or soil types. Perhaps it is exacerbated in close proximity to century old trees. Might smaller plants be more susceptible than older ones (because they have less extensive root systems)? What about density? Are dense populations more or less susceptible to desiccation as individuals compete strongly for water?

Whatever the cause, this site illustrates that woody plant encroachment doesn't always end in permanent site occupation. Trying to figure out where it does would improve our understanding of both the process, and the management response.

Building community-based monitoring

Latrobe students quantifying the effects of fire
in the Little Desert NP.
(Photo: John Morgan)

I teach undergrad Botany and Ecology at La Trobe University. My university has a really good reputation for training field-based biologists, and many of our graduates are now making great contributions to conservation through their work in ecological consultancies, local government, government research organisations, NGOs, environmental education and parks management. Many of the undergrads I teach, particularly the mature-aged students, have a real passion for the natural world and really know that they want to make a difference.

As part of my outreach activities, I also engage with local community groups - such as Friends Groups (like my local group called Holly Hill Revegetation Group), local plant groups (e.g. Australian Plant Society), Landcare Groups and naturalist societies. This is also really rewarding - here's a bunch of (mostly) amateur enthusiasts wanting to making their local environment better, and protect what little bits we have left by taking an active interest in their management. Unlike the university students I teach, many of these people don't know much about biology and ecological principles. I see my role here as one of educating to ensure better outcomes.

Engaging with the "community" is a crucial way to get them interested in natural systems and harness their desire to do positive things. We've done this well on many fronts. One thing that is really taking off amongst these community groups is the field of citizen science monitoring. Here, local people are keeping tabs of environmental change in their local area, often doing excellent work that universities and governments are unable to do. WaterWatch is a good example of a programme that relies on volunteers to assess water quality in local catchments.

This is a great way to engage with people. But is it useful as a scientific activity to improve management by changing land management practices, i.e. learning by doing and then adapting management? I don't want to get into semantics about the quality of data that is collected, or the motivations of people who collect data. I'm more interested in thinking about "what is useful monitoring" and how to we maximise the benefits we get from such monitoring.

I've been musing about this a little because I'm often asked to help design monitoring for community groups, knowing full well that such monitoring, to be useful, needs to be simple, long-term and consistent. Here's a couple of suggestions that might help us think about what useful monitoring might be.

1) Identify the 'problem' first! The best monitoring has a clear question(s) / objective in mind from the outset that really determines what the monitoring should be and how it should be undertaken. Importantly, the information gained from the monitoring should help establish better practices in the future rather than just documenting change.

Planting Buloke trees into ex-pasture
(Photo: John Morgan)

Here's a simple example. Your local Landcare Group is revegetating some upper slopes box ironbark woodlands and will plant tubestock to establish trees. Your main concern is the need for weed control in the initial establishment phase because you've observed that establishment success seems patchy in previous years. Hence, it would seem logical to (a) plant some trees into intact understorey and (b) plant some trees where you've sprayed the understorey out. You count the number of individuals in each area then return yearly to recount the trees to assess survival. A more nuanced monitoring would record tree height to see if plants are also growing faster where there are no competitors in the initial phases. This might seem an obvious "experiment" but it is worth monitoring because the outcomes would really help us better use our resources - should we spray weeds out  or if we don't need to spray, can we plant more trees. This monitoring might highlight where the real problem lies too. Trees might do really poorly in both areas because of herbivores, or low soil moisture per se, hence allowing us to design better plantings in future. While this monitoring may not be that "exciting" to do, it is very useful.

2) Keep it simple! When thinking about monitoring, the best information tends to be that which addresses Primary Questions. I tend to think of ecological questions as exiting in a hierarchy that span from Primary, Secondary and Tertiary level questions. Here's an example, about mistletoes.

Mistletoes are really important in woodland and forest ecosystems in Australia because they are food and habitat for a whole heap of birds and animals, and have important roles to play in nutrient turnover. Hence, if I was an restoration practitioner who had been planting trees in agricultural landscapes for connectivity, habitat enhancement, etc, I'd be keen to ask the following (hierarchical) questions:

Dropping Mistletoe
(Photo: http://davesgarden.com/guides/pf/showimage/189316/)

Primary: Are mistletoes naturally colonising revegetation plantings?
Secondary: Does distance to nearest patch of remnant vegetation affect whether mistletoes are colonising reveg plantings?
Tertiary: Are mistletoes more numerous on some reveg tree species than others?

Hopefully you can see here that the Primary Question, about whether mistletoes are colonising plantings, is probably the most important question to ask first. It is probably also a pretty simple question to answer with monitoring: go out to XX planting sites and search for mistletoe colonisation on trees. Record which plantings have them. The information derived from this exercise informs us about their capability to recolonise reveg plantings, and from this we can start to understand the Secondary and Tertiary Questions. However, there is no need to ask the latter questions if the answer to the Primary Question is "No". You can see from this example, the monitoring could be very simple - there is not need to complicate things initially. Resurveying plantings 3-5 yrs later would then tell us about whether the situation is stable or changing.

3) Archive data somewhere!  Citizen science is a great concept, but for it to be useful, the data that is collected needs to be stored somewhere that is accessible into the future. Importantly, the data needs to be used periodically to inform understanding and leverage decision making processes.  Most ecologists who study long-term dynamics do so knowing that dynamics will span decades. In Australia, there are ecological experiments that have now been going for many years (in some cases 50-100), but they are only valuable because the data is archived and can be accessed for future comparison. Indeed, the new Terrestrial Ecological Research Network (TERN), a federal government initiative, is almost entirely about databasing old and new data. This will be a great resource for scientists over the coming century if it can be maintained. A similar approach is needed for citizen science.

This might span a range of scales. If your local bush group is into collecting information about birds and plants, perhaps by annual surveys, then this data is most useful if archived in national databases where such records already occur. The Atlas of Living Australia (ALA) is a superb repository for such data - species location records are a powerful way of observing changes over time. Because these databases are free to access, they really are an excellent place to put your data (which you can then always access) and they allow others to profit from your hard work. Imagine 25 years of bird count data, collected from across Melbourne, being in the ALA and accessible for all. It would give a great overview of the status of native birds in a rapidly growing city. Indeed, such databases are already contributing to this understanding. WaterWatch is an excellent example of collecting data and archiving it as an online resource - it's worth checking out.

Of course, there are much smaller scale ways of archiving data. In local Friends Groups, perhaps the group nominates a 'data manager' and their role is to report annually on what data was entered into their local database. If this was minuted each year, it would be pretty easy to know what was being monitored and where that data resided. I often think it would be great if I could access dates of burning of native grasslands where local groups have now been monitoring them for years. Sadly, such data is not being kept.

This returns me to my original thoughts - be clear about what it is you are monitoring, and why? If it is just to engage with local communities, let's not call it monitoring. Let's call it scientific outreach where we teach people how to monitor. But if we are to monitor, let's do it well and have a clear reason for doing it. And let's use the information being collected to make better environmental decisions.

Fire in native grasslands: getting to grips with some key unknowns (part 2)

In Part 1, I introduced the notion that we don't have a good idea of historical (post-European settlement) fire regimes in native grasslands (let alone pre-European), but by using the Minutes of rural fire brigades, it is clear that some of the best examples of grasslands in western Victoria have been burnt near annually for 70 years. This won't apply everywhere, but it tells a story of fire in the landscape that has previously gone un-noticed in some ways.

In this Blog, I return to one of the big unknowns about fire in grasslands. Despite it's importance, there is almost no data on fire behaviour in temperate grasslands.

Fire behaviour describes the fire event: the fire intensity, the thoroughness, the extent, the duration of heating. While there has been much research examining the effects of historic fire regimes (1 versus 3 versus 5 year burning frequencies), managers have almost no information about how individual fires vary and what the implication of these differences in fire events might mean for mortality processes and rates of regrowth.



Fire behaviour in grasslands will be a function of fuel amount, fuel type, fuel moisture  and conditions on the day
of burning. How grasslands are burnt (i.e. lighting patterns)  also has a profound affect on fire behaviour. Here, in a grassland near Dunkeld, we can see a patchy fire. But why?
(photo: John Morgan) 

To address this information gap, my Honours student Karina Salmon and I have been quantifying Fire Intensity and Residence Time for a number of grassland fires this summer. These two measures tell us something about (a) amount of energy released by a fire (I = fuel load * rate of fire spread * constant) and (b) duration of heating (above 200 deg C). Clearly, Intensity will vary with fuel and fire weather conditions on the day; faster moving fires are generally more intense. Fast moving fires probably also have lower residence times at a point, although this is not well-established in the literature for mesic grasslands.

Below is a link to a video that shows how grassland managers burn grasslands (in this case, a local Council near Sunbury). I want you to observe a couple of things here: rate of spread and flame height. While watching this, observe the lighting patterns and weather conditions. This has a tremendous effect on the way the grassland burns.

A couple of questions to ask yourself: Is this an "intense" fire? What is the ecological impact of this fire?

Let's answer the first question. Is this an intense fire?

How long is a piece of string?? Fire intensity is a relative measure in many respects. Forest fires can exceed 100,000 kW/m in intensity and hence, no grassland fire will ever be this intense as the fuel loads do not accumulate to the same degree. Hence, it is better to ask: is this an intense fire relative to other fires you get in grassy ecosystems. Even then, that answer is not straightforward. In tropical savannah, fire intensities up to 18,000 kW/m have been recorded, but fuel loads can be enormous - annual grasses take advantage of the wet season and put on several metres of growth each year. So we need to narrow this question even further. Is this an intense fire in the native grasslands in southern Australia?

We characterised this fire at about 500 kW/m, which isn't very high.

This is a one of the 'middle of the road' fire intensities that have been recorded in native grasslands. But it clearly 'looks' like a decent burn that you may have initially thought was 'high intensity'. It goes to show that just observing fires isn't very informative. All fires are hot, to some extent, so value judgements like 'low' intensity, or 'cool' burn aren't very helpful.

Of great interest to me is another (almost completely ignored) aspect of fire behaviour: Residence Time.

This fire had a temperature above 200 deg C for an average of 29 seconds (at the point of recording by a Type-K thermocouple). This heating, from a relatively low intensity fire, is what plants and animals actually have to put up with. Burning for half a minute is the real challenge here when thinking about probability of survival. Interestingly, at very low Fire Intensity, we found that Residence Time can be quite long, more than a minute in some cases. When fires are slow moving (as low fire intensity fires usually are), heating above 200 deg C is prolonged - the flames are not moving away from a point quickly. Hence, an (unintended) outcome of 'low fire intensity fires', by slow back burning of the grassland is that they heat for longer durations than higher intensity fires, and they burn very thoroughly. Almost no fuel goes unburnt in some cases.

Hence, it is clear we still have much to learn about ignition patterns, fire intensity and residence time, and how these interact to affect plant and animal population dynamics. I'm keen to explore these ideas next summer, so if you're planning on burning a grassland, I'd be keen to set up some dataloggers and quantify what's actually going on.

Fire in native grasslands: getting to grips with some key unknowns (part 1)

We've now had 35+ years of grassland research in the temperate regions of south-east Australia. Native grasslands, in many respects, are now amongst the best studied systems in Australia.

I reckon four key insights have been revealed by this work, with each insight critically interacting with the others to inform our understanding of vegetation dynamics:
1) land use history affects vegetation composition and species diversity. Importantly, by quantifying vegetation structure and composition using land use comparisons (i.e. grazed grasslands versus burned but ungrazed grasslands), it is apparent that native species richness and functional trait diversity is highest when disturbed by fire rather than by other agents such as slashing or stock grazing, and that frequent fire maintains higher alpha diversity than infrequent fire.
2) when frequent burning of grasslands is relaxed, species can go locally extinct. This has been well documented in recent times by Nick Williams & others as socio-economic drivers of burning change.
3) many intertussock species are poor competitors for light and space (and these species can be predicted by their traits). Just as there is a war going on in woodlands between trees and grasses, the war extends to grasslands where grasses often outcompete forbs because they are taller, accumulate more biomass (and hence, sequester more of the light and nutrient resources) and they grow faster.
4) many grassland forbs have transient soil seed banks (i.e. seed does not accumulate in large numbers in the soil). This has important consequences for regeneration. Once grassland plants are lost from grasslands (because of grazing or lack of fire), they are unlikely to re-populate from dormant seed stored in the soil.

The core findings all lead back to the key role that fire plays in the dynamics of the system.

This has long been recognised. But curiously, despite the importance of fire in the function of grasslands, we still know relatively little about (a) fire history (particularly as it relates to the high quality grasslands that sustain much of the species diversity of this ecosystem), nor (b) how fire behaviour varies in grasslands.

Recent research is shedding new light on both these questions. In this Blog, I'll tackle the first question - if frequently burned temperate grasslands are the "gold standard" for grasslands, just when did this regime start?

Sarah Dickson-Hoyle (University of Melbourne) recently completed a Master of Forest Ecosystem Science thesis with the core question being: when did Country Fire Authority (CFA) burning by rural brigades in western Victoria start, and why? She focused her attention on the 3-chain wide roads around Dunkeld-Cavendish where there has been settlement since the mid-1800s. Until now, I'm not aware of when this burning started nor why it started in the first place.

Sarah interviewed current CFA brigade captains in the area about why they burn, how often they burn, and whether they knew about the grasslands and their ecological values. She also examined brigade Minutes to try and pinpoint when this burning began.

In this district, she found that burning for fire protection began in the period 1941 to 1947. This is before much of the land was re-settled by soldiers returning from the Second World War. Burning was implemented on 2- and 3-chain wide roadsides as frequently as possible to maintain low fuel levels.

Interestingly, according to the Minutes of CFAs, burning began largely because of the introduction of exotic pasture grasses such as Phalaris (as superphosphate use increased) and the perception that they created an elevated fire risk due to their high fuel loads and early curing. Burning of roadsides started because local communities wanted risk reduction strategies implemented. It was thought that 1-2 year intervals between fires would provide the greatest protection to the community, with little regard for the ecological effects of such regimes.

I think the dating of the start of frequent fires in these systems in the 1940s is at least 10-20 years earlier than most grassland botanists had estimated.


The original survey of the Karabeal Plains from 1865 showing 2 and 3 chain wide roadsides that later became
 strategic fire breaks and, fortuitously, some of the best temperate grassland remnants in Australia.

It is likely that burning of native grasslands by Europeans probably started in earnest at this time not just around Dunkeld, but across the plains in many areas, just as the landscape was transforming due to sowing of improved pastures. It's hard to know what was happening before then of course. Perhaps travelling stock periodically reduced biomass. It is clear that the subsequent 70 yrs of very frequent burning in this district  has given us species-rich native grasslands with minimal invasion by exotics. Such practices have also shaped our ecological thinking about vegetation dynamics in productive grasslands. Without such burning, I suspect our understanding of the potential role of fire on diversity, productivity, recruitment and species-interactions would be very different. Paradoxically, an ageing rural population and increasing paperwork mean that frequent burning by the CFA is now in decline in some districts, and being replaced by slashing or inaction.  This change in regime will undoubtedly shape the future native grasslands as much as any impact of climate change.

In Part 2 on fire, I'll return to the question: what do we know about fire behaviour in grasslands? We've been quantifying fire this summer, and getting some surprising results.

Dickson-Hoyle, S. (2013) Risk, remnants and roadsides: understanding fire and conservation management along a rural road, western Victoria. Master of Forest Ecosystem Science thesis, University of Melbourne.

Free Public Symposium on Fire Management in the Australian Alps

WEDNESDAY 21^st MAY 2014, 530 to 700 PM

Hoogenraad Auditorium, La Trobe Institute for Molecular Sciences

LA TROBE UNIVERSITY, Bundoora Campus

Hosted by the Research Centre for Applied Alpine Ecology, La Trobe University

This Symposium will showcase how science answers questions about a current, highly topical management issue in the Australian Alps – the effects of livestock grazing on fire regimes of the Australian High Country.  The guest speakers will address globally important topics such as the evolution of Australia as a flammable continent, how weather and fuels determine fire regimes, fire-grazing interactions, and approaches to assessing the effectiveness of various fire management options, including alpine grazing. This is a public forum about an important land management issue, and there will be ample time for questions and discussion at the conclusion of the talks. The Symposium will be followed by drinks and nibbles.

This Symposium is a must for anyone with an interest in the ecology and management of the Australian Alps.

 

Enquiries and reservations: femaa2014@gmail.com    

Places are limited. RSVP: 15^th May 2014

Full details about venue location, parking & access to LTU will be forwarded after registration.

 

Beyond the 'extinction debt'

The best examples of temperate grasslands of SE Australia, like tallgrass prairies in the USA, now largely exist in small, isolated pockets, and are of variable quality due to a century of more of land use. They're the last bastions of these once great ecosystems.

Basic conservation biology theory tells us that long-term conservation of the ecosystem will be challenging - populations are small and isolated, habitats have been degraded by weed invasion to varying degrees, and interactions (such as plant : pollinator mutualisms) may have already been disrupted.

High quality native grassland on three-chain wide roadside at
Derrinallum. Mt Elephant looms large in the background.
(Photo: John Morgan)

Hence, conservation of the biota will be a challenge.

To illustrate the scale of the problem, thanks to generous funding from the The Myer Foundation, our research team has just recently completed a floristic survey of Melbourne's Urban Grasslands. Our fabulous botanist Ben Zeeman (and team) recently surveyed the floristic composition, structure and population size of selected plant species. In total, we surveyed 79 public grasslands for composition (totalling 1393 ha), did 904 transects defining structure, and made 45,200 species observations. Wow! What an effort. Of the 250 native species we observed, 80% were confined to 20% or fewer sites. Hence, while there is still lots of native plant biodiversity in urban Melbourne, much of it is perhaps on the brink of extinction.

Extinction debt is a concept in ecology that may have great relevance to Melbourne's grasslands.

Extinction debt occurs because of time delays between impacts on a species, such as destruction of habitat, and the species' ultimate disappearance. For instance, long-lived trees may survive for many years even after reproduction of new trees has become impossible, and thus they may be committed to extinction. Extinction debt is most likely to be found in long-lived species and species with very specific habitat requirements (specialists).

Extinction debt has important implications for conservation, as it implies that species may go extinct due to past habitat destruction, even if continued impacts cease, and that current reserves may not be sufficient to maintain the species that occupy them.

So what can be done to reverse the extinction debt in Melbourne grasslands? This is a conversation we need to have. Biologists are telling us there will be a continuing crisis (and they have been very good at documenting declines) but is there a way to slow / reverse the extinction debt?

There are probably several answers here. Using a basic understanding of the threats to remnant vegetation that apply anywhere where land use has transformed the native landscape, I can think of four key things we should be doing.

1) Supplement / enhance small populations: we know one of the main reasons that populations go extinct is that they become small and hence, vulnerable to loss of genetic diversity, environmental stochasicity, and regeneration failure due to the fact so few propagules being produced. Hence, having identified which species are in this category in Melbourne's grasslands, perhaps we should look at bulking up population numbers. This might be done with transplanting plants and sowing seeds. Importantly, such activities should not be restricted to just rare species. Our data tells us lots of species might be in trouble.

2) Promote population turnover: one of the reasons populations become small is because recruitment ceases to replace mature plants. If deaths > births, then it is inevitable that populations decline to local extinction. Hence, rather than just maintaining adults (the thing that we see in grasslands), it is imperative that the mechanisms that allow seedling recruitment are well-understood and, more importantly, the conditions for regeneration are maximised. A focus on seedling recruitment needs to occur. My own work suggests that seedlings of many species require lots of light to survive, and that recruitment is episodic and probably related to years of above-average rainfall. Maybe we can enhance recruitment success by removing canopy (by fire or slashing) and watering plots to see if seedling recruitment improves.

3) Maintain important ecosystem processes: one of the critical processes in grasslands is the effect that dominant grasses have on smaller intertussock species. Strong, asymetrical competition means that Kangaroo Grass tends to win the battle when left undisturbed. Hence, frequent implementation of fire (or some other mechanism such as slashing) needs to occur if you want to maintain intertussock species of the majority of the flora. This is well known, but needs to be implemented.

4) Empower people to care: if we are to avoid a massive loss of Melbourne's grassland biodiversity, we have to make people care about this. Many people already do. There are dozens of terrific Friends Groups, individuals and agency staff who are working tirelessly to improve grassland condition and recognition. This energy needs to be harnessed, and a broader audience cultivated. Those people who live near grasslands have to care about them, otherwise conservation of local diversity will always be a challenge.

Recently I saw some excellent signs that advertise the values of grasslands and their habitats. This was on one of the best rural roadsides for native grasslands there is, so the values are already well-known. But I applaud the local Shire for emphasizing the values of remnant grasslands, and why we should care. This needs to happen in Melbourne, least we lose lots of our grassland flora and no-one notices.

The fabulous signs on the Cressy-Shelford Rd promoting the values of the native grassland
as habitat for endangered species. The signs measures approx. 7 m x 2.5 m and are produced in high quality materials.
(Photo: John Morgan)