The rise of grasses and grasslands in Australia

It's been a while since I wrote. The perils of too many things on, a loooonnnngggg list, and not enough time.
 
Recently I've been thinking about my favourite biome - the grasslands - and when they came to prominence in Australia. Was it because of megafauna? Was it because of climate? Was it because of Aboriginal burning?  So, I started reviewing the literature and thought I'd share my findings here. It's a fascinating topic and one that I'm pretty sure most biologists / grassland aficionados  /ecologists aren't entirely familiar with.
 
 

Mitchell Grass grasslands - widespread in
north-eastern Australia, but when did they
come to prominence?

While tussock grasslands are a widespread vegetation type in Australia, grassland ecosystems per se were largely absent from Australia until fairly recently. It is also likely that the C₄ contingent of grasses that currently occur in Australia are recent arrivals to the continent. Jacobs et al. (1999) provide a comprehensive review of the topic.

Grasses originated in Gondwana during the Cretaceous (>65 million years ago (Ma)) with some speculation that graminoids possibly originated in East Gondwana, notably the area that later became Australia. In Australia, however, there are almost no early preserved grass macro-fossils, possibly due to the bias towards their preservation in wet environments. The earliest record of Australian grass pollen is from the mid Eocene (~45 Ma), but it has always been relatively sparse in the Australian fossil record, only becoming most abundant within the last 2 million years.

Grass pollen first occurs in north-western Australia, possibly forming savannah by the mid-Miocene (~15 Ma). The expansion of open vegetation types accelerated in the late Miocene due to increased climate seasonality. There were rapid evolutionary radiations in many large Australian groups such as the sclerophyll taxa Eucalyptus, Banksia and Allocasuarina at this time, as well as grasses. Austrostipa, for example, originated and began to diversify between 25 and 10 Ma, and a rapid radiation occurred, indicated by a high diversification rate at that time. Increasing taxonomic diversity may have resulted from adaptation to newly derived arid niches caused by climatic changes.

From north-west Australia, grasses expanded south-east through central Australia as aridity intensified through the Late Tertiary. Grasses were present in northern and central Australia, extending into the Murray Basin, in the early to mid Miocene. The entry of grasses into more southern and eastern areas of Australia occurred in the mid to late Miocene and early Pliocene (~5 Ma). Fires were part of the landscape in the Murray Darling throughout the Miocene, increasing with climate seasonality, potentially facilitating the spread of grasses and grasslands, particularly those dominated by C₄ grasses.



Themeda triandra - one of the most widespread
C4 grasses in Australia


Many grasses that are now common in Australia appear to have migrated from Asia during the Miocene when Sundaland (the Indonesian archipelago) collided with the Australian plate, including the C₄ genera Themeda, Dichantheum and Bothriochloa. A number of tropical south-east Asian genera have strong representation in Australia due to this early migration. All are tropical grasses which extend into the temperate zone of southern Australia. The Andropogoneae (which includes all the above genera) have major centres of distribution in south-eastern Indonesia and India, with a lesser centre in central eastern Africa. This infers that the taxa have entered Australia from the north since its collision with Asia (although Andropogoneae may have existed in Australia before this time). It is likely that Themeda migrated from south-east Asia into both South Africa and Australia in the late Tertiary; it is now widespread in both continents.

C₄ grasses extended into the temperate regions of the south of Australia, most notably, Themeda, the genera that subsequently became the dominant mesic grassland type in the south-east of the continent. In southern Australia, however, grasses did not achieve their current prominence until the Late Pleistocene. Explanations for the C₄ expansion across the landscape in the Miocene have invoked changes in the seasonality of climate, particularly climate drying, given the C₄ pathway appears to give grasses a competitive advantage in arid environments, and to changes in fire regimes. Increases in the abundance of the major C₄ clades Paniceae and Andropogoneae were thought most favoured by these changed conditions, although the reasons for the rise of C₄ grasslands per se are still debated. New research, for instance, suggests that the C₃ Pooideae (which include the Stipeae) expanded into cooler climates rather than being outcompeted by C₄ grasses, an event that is possibly as important as the global C₄ expansion.

Further Reading
Jacobs, B.F., Kingston, J.D. & Jacobs, L.L. (1999) The origin of grass-dominated ecosystems. Annals of the Missouri Botanical Garden 86, 590-643.

Do we need a moritorium on seed collection of rare plants in small remnants??

I've just visited one of my favourite temperate grassland remnants near Melbourne, Australia - Truganina Cemetery. It's long been a favourite of mine because I started my grassland journey there. It was at Truganina that I studied the seedling recruitment dynamics of a very threatened grassland daisy, the Button Wrinklewort (Rutidosis leptorrnhychoides), with the aim of enhancing conservation management for its persistence.

I've long since taken an interest in this remnant which is very species-rich and managed sympathetically by burning at 4-5 yr intervals. It's an excellent place to see the original plains grasslands that once covered 22,000 km2 of western Victoria. Indeed, as Neville Scarlett impressed upon me, if you want to save ecosystems like temperate grasslands, you need to save all the parts. And Truganina Cemetery is one of those places where we are trying to save the parts.



Truganina Cemetery is a 2 ha jewel in the crown of temperate grassland conservation near Melbourne. It was created in the 1850s and hence, avoided the plough and grazing by sheep. Currently the landscape matrix is one of cropping but urbanisation is rapidly encroaching. The graves are restricted to the eastern boundary. Trees are non-indigenous species planted decades ago in the native grassland. Curiously, their impacts have been positive: many Button Wrinkleworts survive in the halo of the trees where soils are drier and productivity low.

Saving the parts then means those parts get re-distributed elsewhere to reconstruct the ecosystem. Because Trugnina Cemetery contains such a high quality grassland remnant, it supports some very threatened plant species such as the Button Wrinklewort and Spiny Rice-flower (Pimelea spinescens). As a consequence, it is used heavily as a seed collection resource.

Seed collection might be by seed banking organisations, or indigenous nurseries, who follow guidelines for seed collection from remnant populations (e.g. taking no more than 10% of seed available at the time of collection from XX% of the population). To collect seed of indigenous species in the State of Victoria, a permit is required from the State agency responsible for public land, as well as permission from the land manager (in this case, a Cemetery Trust). My big concern is that over the last 10 yrs or so, when I've visited Truganina in summer as part of my ongoing ecological studies, it is clear that seed collection is having an impact on the Button Wrinklewort. Anecdotally I hear that many collectors come to this site to source seed of the Button Wrinklewort (one of only two populations in the Melbourne region, the other having on 20 plants or so).

It may be a coincidence, but in my population counts of this species over the last 20 years (currently sitting at 660 plants, down from 1100 a decade ago), there has been no effective seedling recruitment at this site in the last 5-6 yrs. Why? And might seed collection be contributing to this?



The Button Wrinklewort is a little prettier than the name would suggest!
(Photo: Jamie Pittock, Sterling Park, Canberra)

Climate clearly has a role to play here, so it is not suprising there was little recruitment during the decade long drought (2000-2009). My own research shows that recruitment is best when autumn rains come early in the season (April) as opposed to late in the season (June). Because Rutidosis has a transient seed bank, it requires annual seed input to ensure some probability of autumn germination. The plant itself lives for about 12-15 yrs in natural populations. Hence, seed production is critical to ensure population turnover at decadal timescales. Without seed, population decline in inevitable.

I think I'm starting to see the consequence of very rare plants in small remnants being over-harvested for their seed resource. I have no evidence for this. But I think it might be time we acknowledge this possibility, and over-harvesting as a threat to some populations of endangered plants. Such a threat is not intentional. No one seed collector is intending to imperil these populations. But my worry is that the cumulative effect of seed collection is effectively making populations like that of Rutidosis at Truganina unsustainable.

Perhaps we need a moratorium on seed collection of some species at some sites in some years to ensure that those populations continue to persist into the future. I don't know where most of the seed of Rutidosis is going - into revegetation projects, seed orchards? But what I do know is that the wild population seems to be struggling under current conditions. Certainly none of the seed is being used to propagate plants to be replanted into Truganina to bulk up the numbers.

A moratorium might be quite simple to enact. What about caging individual plants to ensure that some of the individuals in the population set lots of seed and we can then follow whether there is effective recruitment in the following year, and compare that to areas where ongoing seed collection occurs. This might give us some insight into just big a problem seed collection is. It might mean having an agreement with the land manager, who controls access to the site, to limit the number of collectors onto their site per year.

This is sort of radical but it points to the need for getting some control over seed collection, and the need to move entirely to seed production areas to supply the revegetation industry.

Seed production area at Organ Pipes NP,
first established in the early 1990s.
(Photo: John Morgan, January 2012)

Grassland managers in the Melbourne area have done this really well already. At Organ Pipes National Park, the site of Australia's first large-scale grassland restoration, it was recognised in the 1980s that to re-construct the community, seed production needed to be scaled up to supply propagules well in excess of what was available from wild populations. Seed production facilities were developed, learning how to do this through trial and error. Since, Greening Australia has effectively demonstrated how to grow grassland species in cultivation for seed production. They've had superb success. There are even commercial growers now that are being very successful at this endeavour.

This is a serious issue. I think I am witnessing the decline of Rutidosis at Truganina, one of a long-list of species that have declined without us even noticing, nor us understanding the mechanism(s) of decline. Whether seed collection has contributed to this process, I'm not sure. But I am certain that it can't be helping.



Advice for new academics [or what I reckon I've got right, and wrong]

One unintended consequence of working with small plants
has been that my knees are now not so forgiving of a day's
work doing small quadrats!

In late 1998 I was lucky enough (looking back on it) to be appointed as Lecturer in Plant Ecology at La Trobe University. Really, I had  no idea what I was getting into. I'd spent the previous 6-7 years undertaking research, followed by a 6-month Lecturer appointment at Deakin University (filling in for someone on maternity leave). In many respects, I knew I wanted to be an academic but my training really had totally under-prepared me for the actual job. Much of it has been on-the-job learning.

Becoming an academic means you're doing research (and guiding student projects) and teaching (which includes marking, subject co-ordination, subject review, student interactions, etc).  You’re also expected to write grants, serve on a myriad of committees, advise students and review the work of others (manuscripts, proposals). Each of these can take up a lot of your time each day. And there is only so much time in the day to get everything done.  So, I thought it might be useful to list some things that I think I could/should have done better, and some things that I think I've done OK. This might help new academics transition a little easier than I did.

Fifteen years down the track, I'm pretty happy with where I'm at. But, there are definitely some things I could have done better (and if I had my time over again, probably would have). Here's a few things that come to mind:

1. Learn to say no, at least to some things. When you first start up, you feel like you have to impress your workplace, so you tend to end up saying 'yes' to everything. Either that, or like me, you didn't realise you could say 'no'. While busy people make time to do all the tasks they take on, in academia this actually comes at a cost. By agreeing to every committee you're asked to sit on, and doing all the admin jobs around the department, as well as lots of teaching, you actually cut into your quality time to do research, and to hang around with those who do your research (your Post-Grads). It is good to be busy, but not at the expense of the most important task on your Job Description. I have been poor at saying no and now have learnt to say "I'll get back to you on that" or "I need to check my diary first". I still say "yes" way too often. Saying no shouldn't be a reflection that you're not a 'team-player' but rather, you are trying to get a good balance between research, teaching and admin.
2. Team up with a senior academic. Life is pretty lonely in academia sometimes. You feel time-pressured, pulled from all sides, developing subjects with little help, and worry that your research is not going as well as it could. Indeed, you might even feel career success competition from other academics. I felt this way too, mainly because my University didn't really have a mentor programme in place to guide me through the complexity of academic life. So, for many years, I just put up with this. I assumed that you just got on with things. It wasn't till I teamed up with a senior academic (from another University), in what really was a chance interaction, that I started to get some mentoring that helped me figure out 'my job'. This mentoring, unofficial as it was, made a huge difference to how I felt about my place. How to think about priorities, how to see my role in academia, and how to interact in my research field - none of this was ever made explicit.
3. Unfinished projects. I've had lots of great students through the years and we've published lots of good papers. But invariably I've started new projects before wrapping up old ones. This comes at a cost. Some of that great work has yet to be published and, if I'm honest, probably won't ever be now. This is disappointing for everyone as our science, the reason for being in academia, won't ever be scrutinised nor made available to the wider community. I once waited for the student to take the lead on writing up their papers. This has rarely worked. They move on to new jobs, etc and don't necessarily have the same motivation for publishing that I do.  So I'm now much more explicit when it comes to writing. I tend to say that "you've got 6 months to prepare a manuscript. If you don't I will take over the paper and will be first author if I deem I have to re-write the data and general story". I think this is helping getting those unfinished manuscripts written.

The things I think I got right are quite personal, and possibly won't resonate with everyone. But in my case, they have allowed me to stay positive, productive, happy, and to feel like I'm making a contribution to academia and my field of ecology more generally.

Field experiments have been at the centre of my
research world for two decades.

1. My research is diverse, sort of. I tend to work on vegetation dynamics, mainly the role of recruitment processes and how they affect local abundance, species coexistence, range limits, recovery after disturbance, invasions, restoration. I've tended to focus on herbaceous ecosystems. I've branched out into interesting related areas - the role of plant traits in predicting responses to perturbations, or the reversibility of ecosystem states,  for instance - and it is this variety of general questions that continues to drive my curiosity. This is crucial. It means I might have forsaken answering one 'big' ecological question, but being a generalist means I still get really excited about plants every day of the week!
2. Read! I try and read one scientific paper every working day of the year. It's hard, and doesn't always happen. Indeed, it's closer to 3-4 per week. But I find it helps me to keep abreast of the literature, and I feel like I'm up with current ecological discussions. That makes my job as a reviewer, grant applicant, advisor, lecturer easier - because I know where my discipline is at. But I like making lists too! So maybe it just says something about my personality type.
3. My Lab is a small lab.  I take research mentoring seriously. For me, research quality over quantity is paramount. I've never had more than six PhD students at any one time and I like this - it gives me time to be involved in their work at a meaningful level. That way, I can spend lots of time discussing their data, musing over experimental design, and getting to know them as individuals. I think the best thing I can do is invest my time in people and a small lab suits my hands-on style. It also allows to do some of my own research too, and this keeps me sane.

A recent botanical expedition to the Snowy River led us to some
surprising findings!

4. I go into the field. I'm a field biologist afterall. I got into plant ecology because I like nature and being in the field observing patterns and processes. So, I make time (frequently) to go into the field to continue to hone my craft. I find observing plants, away from the distraction of the office admin, is where I have my best ideas. It's where I can mentor students, engage with managers, and see how the research we do in the Lab impacts. I get excited by ideas in the field and probably wouldn't be in academia if my main source of inspiration was removed.
5. Find time to write. I really like writing (hence, the Blog) but almost feel like it is a luxury in my job. Time doesn't permit me to sit at my desk and just write. So, you need to find a way to write, and on a regular basis. I do that two ways. I try and write (or edit) for at least one hour of every second morning (first thing). I also try and work at home one day a fortnight. This mightn't seem much, but you'd be amazed how quickly a month flies by without having worked on a paper when you've got teaching on, grading, theses examinations to do, grants to prepare, etc etc.
6. Make time for family and friends. At the end of the day, they get us through the lows in life, and share our highs. Don't neglect them because you have 'urgent' work to do. That should be done in work time. I've found that working 70 hrs a week isn't actually very productive. I reckon I work 50 hrs a week and even this is probably too much. Weekends are 'me time' as best I can manage. I haven't always done this but I'm seeing the benefit of getting away from academia and enjoying life. For me, that's wooden boats (I have a plan to build one soon), sailing and bushwalking. Surprisingly, I usually come to work on Mondays all invigorated and happy, and that can only be a good thing for my health, sanity and productivity.