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Australasian Plant Conservation

Originally published in Australasian Plant Conservation 15(4), March - May 2007

Abstracts of papers presented to the ANPC National Forum:
What lies beneath?
The role of soil biota in the health and rehabilitation of native vegetation
Canberra, 17-19 April 2007

Abstracts from day one of the ANPC National Forum are presented in the order of presentation of papers.

 

What lies beneath: diversity, function and interactions, focusing on cryptic flora and fungi
Tom W. May

Royal Botanic Gardens, Melbourne. Email: tom.may@rbg.vic.gov.au

This talk introduces the organisms and themes of the ANPC Forum on What lies beneath? The role of soil biota in the health and rehabilitation of native vegetation. The focus of the Forum is the soil biota traditionally classified as plants, among which are cyanobacteria, fungi, lichens, algae, mosses, liverworts and hornworts. These share usually small to microscopic size and often reproduce by spores. Most have been lumped together as 'lower plants', but many are not plants, rather they belong to quite different taxonomic groups, across a number of the kingdoms of living things. Recognition of the relationships of soil biota is important because different groups have quite different life cycles and ways of gaining nutrients. In particular, the fungi cannot photosynthesise, but must gain nutrients from the breakdown of organic matter or by partnerships with other organisms, such as in mycorrhizas. The many interconnections between soil biota and the more obvious plants and animals are much overlooked both in ecological research and in practical efforts at revegetation and rehabilitation. This Forum aims to draw attention to the organisms and their vital roles, and facilitate links among researchers and practitioners with an interest in cryptic soil biota.

 

Biological soil crusts: critical components of soil ecosystems
David Eldridge

Department of Natural Resources, c/- School of Biological, Earth and Environmental Sciences, University of NSW, Sydney

Soil crusts play an important role in maintaining healthy soils in arid and semi arid grazing areas. They are formed by groups of small organisms, technically known as cryptogams, growing on or in the top layers of soil. Lichens, mosses and liverworts and cyanobacteria (blue-green algae), green algae and fungi are involved. The association with the soil is an intimate one. Crusts perform a number of services; most importantly stabilising the soil and preventing erosion, fixing nitrogen, providing habitat and food for invertebrates, assisting with water infiltration, and providing niches for plants to germinate in. Crusts are vulnerable to excessive trampling, and are killed by fire. Once disturbed, they recover very slowly. Biological soil crusts are good indicators of soil health in rangelands. The disappearance of these types can be used as early indicators of soil damage.

 

Biological soil crusts and disturbance: implications for vegetation recruitment
Cassia Read, Jane Elith and Peter Vesk

The University of Melbourne. Email: c.read3@pgrad.unimelb.edu.au

Biological soil crusts are a diverse community of cryptogams that exist at the soil surface in ecosystems of low canopy cover. Disturbances such as fire, stock trampling and vehicle traffic can cause profound changes in the cover and composition of biological soil crusts, with severe and repeated disturbances resulting in complete removal of crusts. Effects of disturbance and the recovery of crusts depend on the type, severity and timing of disturbance, site characteristics and

type of crust affected. The effect of crust disturbance has important implications for management and restoration of native vegetation. Crusts modify the soil environment in ways that affect the germination and survival of vascular plants. Although our understanding of the role of crusts in vegetation recruitment is limited, some generalisations can still be made. Whether biological soil crusts inhibit or facilitate vegetation recruitment has important implications for succession following disturbance events and the long-term health of arid and semi-arid ecosystems.

 

Ectomycorrhizal fungi - vital components of Australia's natural and restored biodiversity
Neale L. Bougher

Department of Environment and Conservation, Western Australia

Ectomycorrhizal fungi interlink with flora and fauna to help sustain the health of much of Australia's natural vegetation. Their extensive fungal networks recycle nutrients, enhance plant uptake of soil nutrients, buffer plants against stresses such as disease, and provide food and/or habitat for many animals>. Many hundreds of species of ectomycorrhizal fungi form symbiotic associations with many trees and shrubs such as eucalypts, wattles, sheoaks and poison peas. Ectomycorrhizal fungi include a range of macrofungi with visible spore-bearing structures such as mushrooms, toadstools, and truffles. In woodland regions of Australia fungal fruiting may be briefer and less consistent than in wetter regions. However this does not necessarily indicate that fewer fungi are present. In both regions a diverse range of fungal networks may be active below ground. In some regions of Australia with extremely diminished natural vegetation very few of the native ectomycorrhizal fungi found in remnant bushland have returned to revegetated areas such as on wheatbelt farmland.  The fungi may need to be assisted back in order to help re-establish the natural processes that have contributed to the sustainability of natural vegetation. Using local plants is a well-established premise for bush restoration, and this applies to fungi too. 

 

Arbuscular mycorrhizas: their function in soil and application to restoration
Peter McGee

University of Sydney

A hugely diverse group of fungi live in association with plants.

Around 75% of all plants and plant species form internal mycorrhizas with arbuscular mycorrhizal (AM) fungi. The fungi have a root phase and they grow out into the soil. In natural ecosystems, AM fungi contribute to the productivity of the plant community, enhancing plant diversity and biomass, and improving structure of the soil. The mechanisms include exploration of the soil, and transport of minerals, especially phosphate from the soluble pool in soil to the plant.

Mycorrhizas are extremely important for plants in Australia's mineral poor soils. AM fungi are found in nearly all soils, including coral islands, and agricultural soils. However, AM fungi disperse very slowly, thus they need to be included in restoration projects where the soil has been severely disturbed, or comes from below the original surface. In native vegetation, species that form complex fruit bodies in soil are the most common type and they are extremely sensitive to soil disturbance; in arable systems, species that form single spores are more common. The species from arable systems are relatively easy to manage, but they are nor entirely suitable for restoration of native ecosystems.

 

The application of orchid mycorrhizal fungi in the reintroduction of Diuris fragrantissima
ZoŽ F. Smith1*, Elizabeth A. James2 and Cassandra B. McLean1

1School of Resource Management, The University of Melbourne. Email: z.smith@pgrad.unimelb.edu.au
2Royal Botanic Gardens Melbourne

Australian terrestrial orchids are dependent on association with a suitable mycorrhizal fungus for germination of seed and development and persistence of adult plants. Understanding orchid mycorrhizal associations is therefore important for developing effective conservation strategies, including the re-establishment of orchids in natural conditions.

Successful reintroductions involve developing self-sustainable populations, which relies on natural in situ establishment of seedlings because of natural mortality rates. Therefore, inoculation of habitat soil with mycorrhizal fungi may be an important prerequisite for the survival of translocated orchids, especially considering the patchy nature of fungi in situ. Further, site conditions must remain conducive to the maintenance of the mycorrhizal association post-reintroduction, but little is known about the ecological requirements of such associations. Reintroductions have been planned to conserve the terrestrial orchid Diuris fragrantissima, which is listed as Critically Endangered in Victoria and Australia, having been reduced to less than 25 plants at a single site.  As the natural habitat of Australian terrestrial orchids declines, reintroductions are becoming more important as a conservation strategy, but current research is limited.

This study investigated the use of supplementary orchid mycorrhiza in the reintroduction of Diuris fragrantissima, and the ongoing survival of fungi and maintenance of mycorrhizal relationships in situ. Addition of mycorrhizal fungi to habitat soils only improved survival of reintroduced plants when combined with soil aeration and when planting occurred in spring, rather than summer or autumn. Source plants for reintroduction were propagated asymbiotically in vitro and became associated with fungi in potting media.

The fungi present in plant roots at the time of reintroduction were sufficient to support the transition from nursery to field. The persistence of actively growing symbiotic seedlings in reintroductions shows that D. fragrantissima can be inoculated post-germination for successful reintroduction, and symbiotic germination was not essential. Mycorrhizal relationships were maintained for over a year, and new associations were formed between reintroduced plants and fungal inoculum. These associations were restricted to individual experimental plots, showing that the fungus did not spread more than 1.5m (distance between inoculum points) over a year. Additional results determined optimum planting season and monitoring dates, which will aid efficient use of future resources. These results may also have implications for the management of wild in situ orchid populations, particularly where disturbance has altered the landscape.

This study involved the largest experimental orchid reintroduction yet to be conducted in Australia, proving successful in the short term with at least 50% of the reintroduced plants surviving into their third season.Extended monitoring of the reintroduced population is required to determine the long term success, including optimising requirements for recruitment of seedlings in situ, by means of pollination and seed germination.

 

Fungi in agricultural landscapes: implications for eucalypt woodland revegetation
Jacqui Stol1 and James M. Trappe2

1 Agricultural Landscapes Program, CSIRO Sustainable Ecosystems, Canberra.   Email: Jacqui.Stol@csiro.au.
2 CSIRO Visiting Fellow / Department of Forest Science, Oregon State University, USA.

Mycorrhizal fungi are a major component of the soil microbiota in many ecosystems. Eucalypts and many other members of the Myrtaceae are highly dependent on mycorrhiza formation for survival and growth. Healthy eucalypt woodland sites generally have abundant propagules of EM fungi, however sites cleared for grazing or degraded may be depleted of these fungi. Such sites are often where revegetation projects are undertaken. In such cases, acceptable revegetation or plantation performance can be enhanced by the planting of seedlings with existing good EM formation.

We undertook a one year pilot project to investigate i) the distribution of EM inoculum along a gradient from remnant vegetation into a paddock, ii) whether inoculation of nursery stock with woodland soil and/or spores is effective, and iii) the effect of different inoculation treatments on eucalypt seedling survival, growth and drought response when seedling are planted out in paddocks.

The results to date indicate that areas of paddock more than 20 m from a woodland edge are likely to have low EM inoculum potential both in terms of numbers of propagules and EM fungus species richness. Woodland soil can be an effective inoculum, but P. albus spores are not, at least under our experimental conditions. Inoculated tubestock planted into paddocks has not yet demonstrated a significant treatment difference in terms of planting success. Effective inoculation of tubestock may need careful management of glasshouse conditions to enhance EM formation.

 

Bryophyte conservation in Australia: facts and fictions
David Meagher

University of Melbourne. IUCN Species Survival Commission, Bryophyte Specialist Group.

Like all native plants, bryophytes have been eligible for listing as 'threatened', 'protected' or an equivalent category under federal, state and territory legislation for many years. In 1997 a list of 150 nationally rare and threatened bryophytes was published by the Australian Government through its Endangered Species Program, but 10 years later only two bryophytes have been listed as threatened nationally under the Environment Conservation and Biodiversity Protection Act 1997. At the state and territory level, only Victoria, Tasmania and to some extent Western Australia have assessed the conservation status of bryophytes, and they are the only states or territories

to have given specific legal protection to any bryophyte species - 15 in Victoria, two in Tasmania and one in Western Australia. Furthermore, the types of protection available in various states and territories differ greatly, as do the mechanisms in place for nominating, listing and subsequently managing species. This talk examines the legal basis for bryophyte conservation and questions whether listing really does offer the legal protection that one might expect.

 

Mammals, ectomycorrhizal fungi and ecosystem processes
Karl Vernes

Ecosystem Management, The University Of New England, Armidale, NSW. Email: kvernes@une.edu.au

Mycophagy ('fungus-eating') by mammals is an important ecosystem process in Australian forests and woodlands, because the hypogeous ectomycorrhizal fungi ('truffles') that are dispersed by mycophagous mammals are symbiotic with trees, aiding them in healthy growth. Studies of mammal mycophagy have generally focused on just one or a few species in a community.

Here, I present data on the occurrence of fungi in the diets of a community of mammals in north-eastern New South Wales that includes rodents, dasyurids, bandicoots, possums, and a range of wallaby species. Many of the ground-dwelling mammals Iexamined consume fungus (18 of 28 mammal species, or 64% of the community), and my work extends fungal consumption to species previous not thought of as mycophagous. Diversity of spore types in the diet ranging from just a few fungal taxa that were detected occasionally to more that 30 taxa that were detected frequently. Mammals differed significantly in the types of fungi they consumed, and these diets changed seasonally, and sometimes, across sharp habitat boundaries.

The ecological implications of fungal consumption and dispersal by such a diversity of mammals, some of which are commonly occurring and widely distributed in eastern Australia, are discussed.

 

Using Fire to Manage for Invertebrate/Fungal Interactions and Diversity
Alan York & Tina Bell

School of Forest and Ecosystem Science, University of Melbourne, Creswick Victoria. Emails: alan.york@unimelb.edu.au  /tlbell@unimelb.edu.au

Community attitudes towards the role of fire in the landscape are slowly changing.  Wildfire is increasingly accepted as both a destructive force and a natural part of ecosystems, and prescribed fire is widely used in many parts of the world as a management tool, modifying environments to achieve specific outcomes.  Is fire a tool that could be useful in ecological restoration?  Scientific literature in this area is currently limited in extent.  Most journal articles in recent years concerning fire and restoration focus on using fire as a tool for landscape "re-creation"; reinstating some historical forest tree community that has thought to

have been lost through fire exclusion.  Similarly, many studies have looked at the use of fire to actively alter the composition of understorey vegetation, usually to remove weeds or other undesired species.  In Australia a small number of studies have used fire to create conditions conducive to the survival of particular plant or mammal species (usually those listed as rare or endangered) or as part of post-mining landscape rehabilitation.

As well as shifting species composition towards some desired state, ecosystem restoration needs to effectively maintain or re-establish essential ecological processes, including the cycling of nutrients.  Fungi and invertebrates co-occur and interact within the soil and litter; playing an essential role in litter decomposition, carbon and nutrient mineralisation and uptake, and the

maintenance of soil structure.  Invertebrates influence fungal communities directly through selective grazing and spore dispersal, and indirectly via litter breakdown and soil mixing. In this paper we use several case studies to demonstrate how invertebrates and fungi respond to, and recover from, fire.  Response to such a disturbance sheds light on the some essential environmental characteristics that influence their distribution and abundance, and in doing so, provides some broader guidelines that may assist land managers achieve important restoration goals.

 

Soil Invertebrates and Ecosystem Function in Native Vegetation
Matthew Colloff

CSIRO Entomology, ACT.  Email: Matt.Colloff@csiro.au

Management practices for re-establishment of native vegetation often do not address the restoration of ecosystem functions and services to ensure the long-term viability of revegetation sites. This is because certain functions may be delivered by organisms that colonise revegetation months or years after it has been planted, yet it is at the planting stage that the bulk of management activity and practice is focused.

We experimentally investigated the provision of a key ecosystem function, the facilitation of water infiltration to the rhizosphere, as delivered by invertebrate ecosystem engineers via the creation of soil macropores (small but visible holes). We measured invertebrate macropore density and water infiltration rates in revegetation sites of different ages, tree species composition and locality, compared with adjacent pastures.

We found a positive linear correlation between macropore density with age of the revegetation sites but not with geographical location or tree species composition. Water infiltration rates in revegetation sites aged 11-20 years were double those of the adjacent paddocks and of sites aged 3-5 years. and 6-10 years. Tree species composition and geography had no effect.

Using our data, combined with observations on accumulation of leaf litter layers and changes in soil surface texture with time, we have constructed a dynamic model of the effects of invertebrates on soil hydraulic properties that are likely to benefit tree growth and survival. This synthesis represents the first step in defining and testing management actions aimed at enhancing delivery of the ecosystem function of water infiltration.

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