Where have all the Yamfields gone?

When Europeans arrived in (what was to become) the State of Victoria in south-east Australia in the 1830s, Aboriginals had a diet that consisted of game - such as possums, birds, lizards, marsupials - and plants. We know the later was important because there are many early journal records, made by settlers, surveyors and those entrusted with the care of Aboriginals, that detail the use of plants as part of the diet. For example, Curr (1883) records that Aborigines were "living principally on wild roots and animals". Gott (1982) suggests that there are at least 218 Victorian plant species with edible roots that could have been incorporated into the Aboriginal diet. No wonder some estimates suggest plants comprised 50% of the diet of Aboriginals.

One of the most important food plants was Murnong - the Yam Daisy as we know it today, or Microseris lanceolata. Murnong is a perennial daisy characterised by radish-like, edible tuberous roots. The first record of the use of Murnong in Victoria is from the Geelong area, by the surveyor Wedge in 1835, who noted that it was "a root eaten by the native" and it was recorded as being in the 'millions' (Robertson 1840). Major Thomas Mitchell, in 1836, also recorded that, east of the Grampians, the "vast extent of open downs" was "quite yellow with Murnong", furthering the belief that it was a widespread, abundant species. William Buckley, the convict who escaped imprisonment and lived with Aborigines, suggested that a "man may live on the root for weeks". At Colbinabbin near Echuca, "yams were so abundant and so easily procured that one might have collected in an hour, with a pointed stick, as many as would have served a family for the day" (Curr 1886). Robinson (cited in Presland 1980) decribes how women were "spread over the plain as far as I could see them... each has a load as much as she could carry".

Murnong was so important - and a preferred food for Aborigines in central and western Victoria - that it was cultivated (in the broadest sense) as a staple food plant. Tubers, which form each year, were dug up and while there is no evidence of deliberate re-planting of Murnong in the process of digging by women for the root tubers, there is abundant evidence that fire was used to manage yams or, as Curr (1883) writes, Aborigines "cultivated his pastures with fire" in order to manage the root tuber resource. This interventionist management has largely been unrecognised, but is repeated throughout the literature. For example, "they burn the grass to better see the roots" (Robinson 1840).

Indeed, what seems to have occurred is that Yamfields were 'created' within forest clearings, grasslands and woodlands by the careful and deliberate use of fire. Yamfields are literally food gardens where the actions of Aboriginals helped maintain, and probably increase, the abundance of desirable food resources. Crucially, there is the potential that forested country was deliberately kept open by fire to maintain these important food plants. Lawrence Niewójt provides a tantalising suggestion to this effect for the Otway Ranges where forests dominate: "Burning maintained the open structure of the forest, allowing continued use of the movement corridor in addition to ensuring good yields of vegetable crops. Furthermore, this flexible system of land management could easily accommodate changes in population by altering fire frequency and physically enlarging yam fields. The tending of herbaceous plants in this manner ensured that foods could be harvested and consumed without the need for storage facilities". Bowman (1998) goes further: "fire was a powerful tool that Aborigines used systematically and purposefully over the landscape" and that "there is little doubt that Aboriginal burning was skilful and was central to the maintenance of the landscapes colonised by Europeans in the 19th century".

Today, Murnong is disappearing/ has disappeared from the plains grasslands and elsewhere. Sheep saw to that; within 15 yrs of European settlement, 20 million sheep swarmed across central and western Victoria. Five years after the founding of Melbourne, the Goulburn Aborigine called Moonin-Moonin had already observed that "too many jumbuck [sheep] and bulgana [cattle] plenty eat it myrnyong - all gone myrnyong" (Dredge 1839). Few populations now remain and certainly it is not in the millions as described by Robinson (1840) and others, such that the "the wheels of our dray used to turn them up by the bushel" (Curr 1886). It's even hard to visualise where these Yamfields once existed. Such is the loss of the natural vegetation, and the loss of the cultural connection with land across much of south-east Australia.

1. Were they confined to relatively small, intensively cultivated areas near water where food resources are highest?
2. Were they scattered across forests, a day's walking apart to sustain people on the move (as hinted at in Blay 2015)?
3. Were they common in areas that now seem somewhat anomalous - grassland clearings in otherwise wooded vegetation?

There is so much we don't know.

I think we need reverse the decline of the Yamfields. Wouldn't it be wonderful to Re-Yam the Plains (particularly the temperate grasslands of south-east Australia that have low diversity because of a century of grazing) and improve our understanding of the role of Aboriginal people in the landscape.  Ecological studies of fire and disturbance would be necessary to understand the conditions under which these beautiful daisies recruit and proliferate. And, by having Aboriginal people involved in the quest to Re-Yam the Plains, it's an important step to involve them to care for country in a way that has little been recognised as important in south-east Australia. The impact of colonisation on Aboriginal landscapes has rarely formed part of the story. This would be a small but important step in that recognition.

If you know of very large Murnong populations on the plains, or are already involved in the recovery of Yamfields, I'd love to hear your story (J.Morgan@latrobe.edu.au).

Selected reading
Blay J (2015) On Track- Searching out the Bundian Way. NewSouth Publishing.
Curr EM (1883) Recollections of squatting in Victoria 1841-1851. Robertson, Melbourne.
Gott B (1982) Ecology of root use by the Aborigines of southern Australia. Archeology in Oceania 17, 59-67.
Gott B (1983) Murnong - Microseris scapigera: a study of a staple food of Victorian Aborigines. Australian Aboriginal Studies 2, 2-18.
Gott B (2005) Aboriginal fire management in south-eastern Australia: aims and frequency. Journal of Biogeography 32, 1203-1208.
Prober SM, Spindler LH, Brown AHD (1998) Conservation of the Grassy White Box woodlands: effects of remnant population size on genetic diversity in the allotetraploid herb Microseris lanceolata. Conservation Biology 12, 1279-1290.

Lab Publications in 2015

Here's a list of publications that the Morgan Plant Ecology Lab has been associated with in 2015. I'm happy to provide PDF copies if you can't access them (email me at J.Morgan@latrobe.edu.au).
 
 

NutNet papers (global studies on bottom-up vs. top-down regulation of diversity in grasslands)

 
Fay et al. (2015) Grassland productivity limited by multiple nutrients. Nature Plants 10.1038/nplants.2015.80
 

Seabloom et al. (2015) Plant species’ origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands. Nature CommunicationsVolume: 6, 7710, DOI:doi:10.1038/ncomms8710

Stevens et al. (2015) Anthropogenic nitrogen deposition predicts local grassland primary production worldwide. Ecology 96, 1459-1465.

 

Alpine ecology and conservation

Mark et al. (2015) Ecological responses to 52 years of experimental snow manipulation in high-alpine cushionfield, Old Man Range, south central New Zealand. Arctic, Antarctic, and Alpine Research 47, 751-772.

 

Williams et al. (2015) An International Union for the Conservation of Nature Red List ecosystems risk assessment for alpine snow patch herbfields, south-eastern Australia. Austral Ecology 40, 433–443.

Grassy ecosystems coexistence and change

Cross et al. (2015) A plant strategy approach to understand multidecadal change in community assembly processes in Australian grassy woodlands. Journal of Ecology, 103, 1300–1307.

 

O'Loughlin et al. (2015) The rise and fall of Leptospermum laevigatum: plant community change associated with the invasion and senescence of a range-expanding native species. Applied Vegetation Science 18, 323–331.

 

Wong et al. (2015) The incorporation of fungal to bacterial ratios and plant ecosystem effect traits into a state-and-transition model of land-use change in semi-arid grasslands. Agriculture, Ecosystems and Environment 210, 11-19.

 

Plant ecology

Meehan et al. (2015) Premature opening and dimorphism in Hakea decurrens (Proteaceae) follicles: a bet-hedging regeneration strategy? The Victorian Naturalist 132, 139-146.

 

And of course, there was the launch of the book Land of Sweeping Plains by Nick Williams, Adrian Marshall & John Morgan (CSIRO Publishing), a synthesis of 40 yrs of temperate grassland ecology, restoration and conservation.

 

 

The perils of wild seed harvesting - an update

I just had to share this post: The Promise and Peril of Wild Seed Harvesting

In a previous post, I raised some concern about the impact of harvesting seed for restoration from wild populations (in particular, from rare plants in small populations).

Justin Meissen and collaborators have just published an awesome paper called " Risks of overharvesting seed from native tallgrass prairies" in Restoration Ecology - see the abstract here.

They found evidence that some short-lived and non-clonal plants were negatively affected by seed harvesting for prairie restoration. They classified these species 'harvest-negative'. While the scales of wild harvesting for prairie restoration seems extraordinary, I'm sure that intensive harvesting of key species from small grassland remnants is just as damaging to their persistence here in southern Australia. All the more reason to move to seed production areas to produce the billions of propagules necessary for landscape-scale restoration.

Cracking open the relationship between biological diversity and ecosystem productivity solves a long-standing riddle

Biodiversity has been hypothesized to be of critical importance for the stability of natural ecosystems and their abilities to provide positive benefits such as oxygen production, soil genesis, and water detoxification to plant and animal communities, as well as to human society. Many of the efforts of conservation agencies around the world are driven by the assumption that this hypothesis is true. Elucidating this connection, and the processes that underpin it, is important on many levels such as anticipating how ecological communities may change (a) in response to anthropogenic perturbations (i.e. changes to the abiotic environment), (b) the introduction of new species or (c) the loss of established ones. While theoretical studies have supported this claim, scientists have struggled for the last half-century to clearly isolate such an effect in the real world. Indeed, a comprehensive, mechanistic understanding of the relationship between biodiversity and ecosystem productivity remains elusive. 



The fundamental mechanisms underlying global productivity-diversity patterns

have been debated by ecologists for decades. Methodological advances are now permitting a glimpse at the processes that lie behind surface patterns.

I was lucky enough to be part of a paper just published in Nature by Jim Grace et al. where we argue that the interplay between these factors is more fully understood when both are placed in a rich network of cause-and-effect pathways, as opposed to being regarded as entities engaged in an isolated back-and-forth.


We considered data generated by the Nutrient Network, a global scientific cooperative that examined 40+ grass-dominated plant communities from across the planet. Indeed, we used data from over a thousand grassland plots spanning five continents.

Location of the NutNet study sites across the world

Several interesting results emerged:

1.  the rate of biomass production increases with the number of species found at a site (its species richness). This effect holds steady across the observed variation in species richness, instead of saturating in communities with greater richness, as a generation of experimental and theoretical work has suggested that it may.

2. with increasing accumulated above-ground biomass (live plant tissue and dead litter)  species richness declines.  We think this provides evidence that competition between species — primarily for light — is an important force in determining why communities contain as many species as they do. Competition seemed to be influential regardless of how productive a community was, contrary to the historical suggestion that competition is a stronger structuring force in more-productive communities.

These results show that you cannot have sustainable, productive ecosystems without maintaining biodiversity in the landscape. Indeed, as Debra Willard, Coordinator for the USGS Climate Research & Development Program, put it: “These results suggest that if climate change leads to reduced species or genetic diversity, which is a real possibility, that then could lead to a reduced capacity for ecosystems to respond to additional stresses.”

One of the Australian NutNet sites, from Western Australia

Further information: Grace et al. (2016) Integrative modelling reveals mechanisms linking productivity and plant species richness. Nature doi:10.1038/nature16524

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.