Spinifex Grass Research Articles

Proximate causes and possible adaptive functions of mast seeding and barren flower shows in spinifex grasses (Triodia spp.) in arid regions of Australia

Mast seeding, the intermittent production of large synchronised seed crops among plant populations, is a phenomenon that occurs at exceptionally long intervals in spinifex grasses (Triodia spp.) from arid regions of Australia. This is despite the reliance of these fire-sensitive plants on seeds for post-fire regeneration, and that spinifex grasslands rate among Australia’s most flammable ecosystems. The proximate causes and possible adaptive functions of masting in seven species of spinifex from arid regions within the 350-mm rainfall isohyet were investigated. Specifically, the seed set percentages of 79 specimens collected between 1947 and 2012 were related to the following environmental covariates: antecedent rainfall over 6, 12 and 36 months, relative humidity, and the number of days above 40°C and below 0°C during anthesis. Given the potential importance of seeding events for post-fire regeneration, it was also investigated whether masting in Triodia could represent a fire-related form of environmentally predictive masting, by testing whether high-yield years corresponded to years of increased fire occurrence. Examination of the dataset showed that 43% of specimens contained completely aborted inflorescences (0% seed fill), while seed set ranged from 2 to 69% in the remaining specimens. High levels of insect activity were also found, with 42% of specimens showing evidence of insect occupation. Statistical analyses showed that the main environmental driver of seed set was high precipitation over the previous 12 months, and that high-yield years were strongly related to years of increased fire likelihood. The number of days over 40°C was a weakly significant driver of yield, while the remaining covariates were not significant. It is hypothesised that intermittent reproduction by Triodia is a fire-related form of environmentally predictive masting, which maximises chances of post-fire regeneration by satiating seed predators during flammable periods (i.e. after heavy rain years). Furthermore, it is suggested that non-viable flower crops after initial low rainfalls may have an adaptive function, by diluting pre-dispersal seed predator densities with ‘decoy’ ovules that do not mature and lead to the starvation of developing larvae.

Introduced and native grass-derived smoke effects on Cymbopogon obtectus germination

Introduced grasses, such as buffel, alter the dynamics of grassy ecosystems by replacing native species and influencing recruitment. Several different smoke-derived chemicals are separately responsible for the promotion and inhibition of germination of various plant species. We tested whether smoke derived from the introduced buffel grass (Cenchrus ciliaris) produced the same density of germination as provided by smoke derived from a native spinifex grass (Triodia brizoides). Smoke from both spinifex and buffel grass significantly enhanced the germination of a native lemon grass (Cymbopogon obtectus) in comparison to untreated seed, reflecting the significant role of fire in woodlands across northern Australia. This is the first record of smoke-promoted germination in a species of Cymbopogon. However, smoke from the exotic buffel grass provided the same level of germination as that from the native spinifex, suggesting similarity in smoke chemicals involved. Further research is required to test the effect of buffel smoke on the germination of other species and whether exotics such as buffel grass provide the same temperature profile in the topsoil as does spinifex, and therefore equivalent germination cues to heat-shock responsive native plants.

Preparation and characterization of green bio-composites based on modified spinifex resin and spinifex grass fibres

Many researchers are now working on composites systems where the fibers and polymers are either totally or predominantly based on renewable materials. The aim of this study is to develop renewable resource-based composites based on spinifex fibers and a polyurethane matrix prepared primarily from spinifex resin. Chemically cleaned and cryo-ground spinifex grass fibres have been used as a reinforcing phase in thermoplastic polyurethane prepared from spinifex resin biopolymer. The morphology, thermal and mechanical properties of the prepared composites were characterized using attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis and tensile tests. The results obtained by various characterization techniques indicate that interfacial interaction between the spinifex grass fillers and the polyurethane matrix occurs and that the ground spinifex cellulose fillers act as promising reinforcement for the relatively weak polyurethane matrix synthesized from renewable spinifex plant resin products.

Dispatches

Dispatches

The Point of Spinifex: Aboriginal uses of spinifex grasses in Australia

For thousands of years spinifex grasses were utilized by Indigenous Australians, most commonly for the production of resin that was then used as a hafting adhesive. While varying levels of knowledge about this particular use are retained in Indigenous communities, museum collections serve as a valuable repository of little known information about a multitude of other uses of spinifex including ornamental, medicinal, structural and ceremonial functions. In this paper we describe the range of uses of spinifex, based on examinations of objects and photographs held in various museum collections, coupled with reviews of the ethnographic and ethnohistoric literature. This study (1) brings together disparate sources of knowledge about Indigenous uses of spinifex that are not well known among the scientific community and (2) demonstrates the value of museum collections for Indigenous communities seeking to ‘reconnect’ with aspects of so-called ‘lost traditional culture’. 

Disjunct populations of spinifex-obligate reptiles revealed in a newly described vegetation community near Broken Hill, far-western New South Wales

Recent biodiversity surveys of the Barrier Ranges in far western New South Wales resulted in the discovery of an undescribed vegetation community dominated by spinifex grass growing on rocky ranges. Reptile surveys within this vegetation community revealed the presence of three reptile species not known to, or predicted to occur in the Broken Hill Complex Bioregion. These were the Spinifex Snake-lizard Delma butleri, Marble-headed Snake-lizard Delma australis and Southern Spinifex Slender Blue-tongue Cyclodomorphus melanops elongatus. The conservation value of these populations is regarded as regionally significant. All three species were detected by hand-searches of the spinifex grass highlighting the need to use experienced herpetologists when conducting reptile surveys in complex microhabitats. Their presence in the study area on a rocky substrate provides additional information on their habitat requirements in New South Wales.

Habitat or fuel? Implications of long‐term, post‐fire dynamics for the development of key resources for fauna and fire

Summary1. Managing fire to achieve hazard reduction while providing for biodiversity conservation is complex in fire‐prone regions. This challenge is exacerbated by limited understanding of post‐fire changes in habitat and fuel attributes over time‐scales commensurate with their development, and a paucity of empirical research integrating the effects of fire on these attributes.2. We used a 110‐year post‐fire chronosequence to investigate temporal development in habitat resources used by fauna, and fuels for fire in semi‐arid Mallee vegetation, south‐eastern Australia. Fire‐history mapping previously limited investigation to 35 years post‐fire. The patterns of temporal change over 110 years for 13 variables, representing key attributes of habitat and fuel, were explored using nonlinear mixed models and data from 549 sites.3. Most habitat and fuel attributes exhibited changes in abundance and rate of development over extended periods, emphasizing the importance of documenting post‐fire dynamics over long time‐frames. Further, developmental patterns were mostly nonlinear, indicating that a shorter temporal perspective (e.g. 20–30 years post‐fire) may obscure, or provide an inaccurate understanding of, long‐term changes.4. There were striking differences in the post‐fire dynamics of some habitat and fuel attributes. Leaf litter and spinifex grass Triodia scariosa, which function as both habitat and fuel, increased rapidly after fire followed by a plateau or slow decline after 20–30 years. In contrast, live tree stems were not predicted to develop hollows until 40 years, after which time the density of live hollow‐bearing stems, an important habitat feature, increased steadily.5. Synthesis and applications. Fire affects the development and abundance of resources over substantially longer periods than can be examined using fire‐mapping based on satellite imagery. Our results demonstrate that post‐fire changes in mallee vegetation influence fire hazard and faunal habitat in different ways. Critically, the cover/abundance of most primary fuel sources did not increase substantially beyond around 30 years post‐fire; whereas important habitat attributes changed in ways that affect faunal occurrence for over a century. Fire management must explicitly acknowledge the potential for fire to affect fauna and fuel differently, and for these effects to operate over time‐frames that may extend well beyond current understanding.

Biomimetic Theory and Building Technology: Use of Aboriginal and Scientific Knowledge of Spinifex Grass

There is currently much interest in designing new materials that mimic particular properties of plants. For example, self-cleaning materials have been developed from structures on the leaf surface of sacred lotus, and new composite fibres are being designed from plants to replace metal structures. Biomimetic theory and its application, bio-inspired design, derive concepts from natural systems and appear to have potential to create new types of sustainable materials. The benefits of this approach seem to come from the linking of ethnographic and ecological research with building science to create and test new building technologies. Using spinifex as an example, it has been possible to develop some underlying principles to this approach to advance the methodology.

Water relations and mineral nutrition of Triodia grasses on desert dunes and interdunes

Desert dunes and interdunes provide habitat heterogeneity and profoundly influence the spatial and temporal distribution of water and nutrients throughout the landscape. These underlying physical processes shape the plant species composition and their ecophysiology. Spinifex grasses dominate the vegetation throughout much of Australia and are categorised into two groups; ‘soft’ species occur mostly in northern, subtropical to semiarid regions, whereas ‘hard’ species occur mostly throughout the dry centre and southern interior. This study examined the water and nutrient relations and leaf anatomy of dominant ‘soft’ and ‘hard’ spinifex in the Great Sandy Desert, where their distributions overlap. The ‘soft’ species, Triodia schinzii (Henrard) Lazarides, occurs only on sand dunes, whereas the ‘hard’ species, T. basedowii E.Pritz., is restricted to the flat interdunes. We proposed two hypotheses: 1) that the dune species, T. schinzii would display more favourable water status and 2) the interdune species, T. basedowii would display higher leaf nutrient concentrations. Triodia schinzii displayed significantly less negative leaf water potentials at predawn and at midday (–0.4 and –2.0 MPa, respectively) than T. basedowii (–0.9 and –3.0 MPa, respectively) throughout the middle of the dry season. Photosynthesis rates were also significantly higher in T. schinzii than T. basedowii in the wet season (140 v. 84 nmol g–1 s–1), but there were no significant differences between species in leaf conductance. Leaf δ13C composition confirmed anatomical observations that both species were C4 and supported the finding that T. schinzii displayed significantly greater photosynthetic water-use efficiency during the wet season than T. basedowii. In general, foliar nutrient concentrations were not significantly different between species; however, both species exhibited especially low leaf P and to a lesser extent N. We conclude that water is more readily available in the dune than the interdune as a result of greater soil depth and associated water storage capacity. These properties are considered the main factors influencing plant species distribution. Given the climatic and geographic distribution of these two Triodia species, it is suggested that sand dunes provide a mesic corridor for T. schinzii to extend its range from higher rainfall areas into the arid interior.

CAUSES OF HABITAT DIVERGENCE IN TWO SPECIES OF AGAMID LIZARDS IN ARID CENTRAL AUSTRALIA

The deserts of central Australia contain richer communities of lizards than any other arid regions, with the highest diversity occurring in sand dune habitats dominated by hummock-forming spinifex grasses. To investigate the mechanisms that permit coexistence, we studied two species of coexisting agamid lizards that exhibit striking divergence in their use of habitat in the Simpson Desert of central Australia. Here, the military dragon Ctenophorus isolepis is restricted primarily to sites providing > 30% cover of hard spinifex Triodia basedowii, whereas the central netted dragon C. nuchalis occurs in areas with much sparser (< 10%) cover. We constructed four mechanistic models to explain this pattern and then derived hypotheses to test them. One hypothesis, that competition restricts each species to its preferred habitat, was rejected after dyad encounters in field enclosures failed to elicit any habitat shift or any overt interactions between the species. Our next hypotheses were that each species exhibits preferences for different thermal environments or different prey types and that each selects the habitats that maximize access to them. Both were supported. C. isolepis preferred lower temperatures when active and specialized in eating ants < 5 mm long and selected spinifex-dominated areas where these requirements were met. In contrast, C. nuchalis preferred higher temperatures and a diversity of prey, both of which were available mostly in open areas. Finally, we used plasticine models to test the hypothesis that each species faced lower risk of predation in its selected habitat. This was partly supported, as models of both species were attacked more often in the open than under spinifex cover. The results show that habitat divergence occurs along several, probably covarying, niche axes. We suggest that different levels of spinifex cover provide the template for a broad range of ecological interactions, allowing lizard species to partition biotic and abiotic resources and achieve the extraordinarily high levels of local diversity that are observed.

Spinifex biogeochemical expressions of buried gold mineralisation: The great mineral exploration penetrator of transported regolith

A major challenge for mineral explorers is to efficiently detect mineralisation beneath the weathered cover that extends across the landscape. Determination of the elemental composition of plants (biogeochemical exploration) can aid in the detection of buried ore deposits due to their root penetration through the weathered cover. At the coyote prospect in Western Australia a range of plant species were sampled traversing a buried Au orebody. Here it is shown that the soft spinifex (Triodia pungens) accumulated important pathfinder elements related to the mineralisation, which produced a multi-element surficial expression of the underlying ore deposit. Spinifex grasses are one of the most widespread grasses over the Australian continent and have vertical root systems that can extend for many 10s of metres through sedimentary cover and interact with buried mineral deposits and alteration zones in the underlying substrate. Spinifex biogeochemistry therefore has potential to be a low cost, low environmental impact, sampling medium for mineral exploration programs across large parts of arid Australia. The examination of similar grasses from other semi-arid and arid regions from around the world therefore also warrants further investigation.

Mouthpart and digestive tract structure in four talitrid amphipods from a translittoral series in Tasmania

Structural adaptations of the mouthparts and digestive tract of four talitrid amphipods were examined in relation to diet, habitat and phylogeny. The species differed in their habitat relative to the shoreline and also in their diet: a 5-dentate ‘sandrunner’, Talorchestia species II (a mid to low shore intertidal diatom feeder), a 5-dentate sandhopper, Talorchestia marmorata (a strandline kelp feeder); a 4-dentate sandhopper, Talorchestia species I (extreme high shore, feeding on spinifex grasses), and a 4-dentate landhopper, Keratroides vulgaris (forest leaf litter, litter feeding). Gross structural characteristics of the mouthparts were similar among all three Talorchestia species reflecting their phylogenetic relatedness. Increased setation and minor structural differences among the Talorchestia species could be attributed to dietary differences, reflecting the zones across the shoreline that they inhabit. Mouthparts of K. vulgaris were elongate, with markedly different setation to the Talorchestia species, reflecting its more distant phylogenetic position and its diet of decaying leaf litter. Digestive tract structure was more conserved among all species due to their phylogenetic relatedness. The gross digestive structure conformed to the general plan exhibited by most gammaridean amphipods. However, an additional pair of lateral pyloric caeca was evident in all species, the function of which is uncertain.

A molecular approach to provenance delineation for the restoration of hummock grasslands (Triodia spp.) in arid‐tropical Australia

Summary Studies were undertaken to develop genetic principles for the restoration of spinifex grasses (Triodia spp.) at the Argyle Diamond Mines in northern Australia. The study used random amplified polymorphic DNA (RAPD) DNA markers to provide a molecular delineation of provenance boundaries for two species Curly Spinifex (Triodia bitextura) and Triodia bynoei and to provide measures which ensure replacement of local genetic diversity. Within‐population diversity measures (0.44 ± 0.03 T. bitextura and 0.32 ± 0.04 T. bynoei) and the proportion of diversity attributed to between‐population differences (≈ 12%) by analysis of molecular variance (AMOVA) indicate extensive out‐crossing in these seeder species. As such, both species should be restored using seed‐based methods to maintain natural diversity. Significant groups of populations (P &lt; 0.05) identified by AMOVA correspond directly to clustering of populations in a dendogram drawn using UPGMA, indicating significant provenances in both species. For T. bitextura, a significant genotypic variation identified at 60 km from mine populations was not evident at 30 km. Seed for restoration at the mine should, therefore, be harvested from within 30 km of the area to be restored to ensure maintenance of the local provenance. Two T. bynoei populations located 2 km apart were found to represent a single genotype, all other populations were identified as separate genotypes. The majority of the isolated T. bynoei populations, therefore, represent distinct provenances. For both species, in excess of 80% of the measured species diversity occurred in just 20 individuals. As restoration of these grasses will necessitate harvesting seed from thousands of plants the species capacity for evolutionary change should be maintained. With continuing improvements in the effectiveness of molecular genetics technology, the assessment of provenance boundaries through the use of genetic markers is becoming a realistic option for the development of more genetically representative sourcing of genotypes in plant restoration programmes.

The impact of grazing by macropods on coastal foredune vegetation in southeast Queensland

Abstract The extent of grazing by two macropodids, the agile wallaby (Macropus agilis) and the swamp wallaby (Wallabia bicolor) on coastal foredunes on South Stradbroke Island in southeast Queensland was investigated to determine potential impacts on the principal sand colonizing species, sand spinifex grass (Spinifex sericeus). Grazing on spinifex grass on the foredunes of South Stradbroke island can be attributed principally to agile wallabies. Foraging activity by wallabies was higher in areas of high spinifex abundance, however, grazing intensity and impact on spinifex was only important on foredunes with low spinifex abundance. Spinifex consumption by wallabies was also related to a number of factors, especially composition and structure of vegetation in adjacent habitats. Spinifex consumption increased when the abundance of ground cover components (grasses, sedges, forbs) in adjacent habitats was low and structural complexity was high. Grazing on foredunes by wallabies significantly affects the species composition of the foredune community by excluding the establishment of a number of perennial foredune plant species. This may have implications for community succession in coastal ecosystems.

Ecological Observations on the Spinifex Ant, Ochetellus flavipes (Kirby) (Hymenoptera: Formicidae), of Australia's Northern Arid Zone

ABSTRACT Ochetellus flavipes constructs covered runways across the surface of the ground by fastening grains of sand together with resin from spinifex grasses (Triodia and Plectrachne spp.), and travels inside the runways from its nests to the spinifex hummocks. the ants also build shelters from the same material enclosing mealybugs, Prorsococcus acanthodus, which are tended on spinifex by the ants. the ants occur patchily, and are known from less than 30 localities across a vast area of northern Australia. Topographic positions of these localities suggest that peculiarly favourable moisture conditions are necessary to support both mealybugs and attendant ants. Microclimatic conditions and thermal tolerances of the ants were assessed to investigate the possibility that the runways allow the ants to ameliorate their thermal environment, but the results do not support this notion. We suggest that the structures may serve as protection from predators and/or parasites.

Mycogeography of Fusarium: Fusarium Species in Soils From Palm Valley, Central Australia.

The identity and abundance of Fusarium species in soils from Palm Valley in the central arid ranges of Australia were assessed in two successive years. This location enabled a comparison of Fusarium species in soils from within the valley where soil moisture is more readily available and the dominant plants are shallow rooted palms, with Fusarium species in soils from the arid rim characterised by spinifex grasses and xeric shrubs. Sixteen sites were sampled. Of the sites within the valley, four were dominated by palms, three by cycads, and four by endemic grasses. The five arid habitats sampled from the rim were dominated by grasses. Twelve Fusarium species and one subspecies were isolated using the dilution plate technique and peptone-PCNB agar. Fusarium oxysporum was recovered from all sites in both years irrespective of vegetation or moisture availability. Fusarium compactum, F. solani and F. scirpi were recovered from most sites. The greatest range of species was recovered from grassed sites, with fewest species being recovered from cycad sites. Taxonomic characteristics of the isolates of F. polyphialidicum are described in detail because they expand the boundaries of the published description.

Granivory and microhabitat use in Australian desert rodents: are seeds important?

The diet and microhabitat use of two species of native Australian desert rodents, the spinifex hoppingmouseNotomys alexis and sandy inland mousePseudomys hermannsburgensis, were studied in the Simpson Desert, south-western Queensland. Contrary to expectation, both species were confirmed from analyses of their stomach contents to be omnivorous. The diets of both species varied through time in a similar manner; seeds were important in summer and especially in winter, but in autumn invertebrates constituted nearly 50% and 60% of the diet ofN. alexis andP. hermannsburgensis, respectively. Other plant material (root, leaf, floral part, stem) was found in appreciable amounts in the stomach contents of both species, and fungi were identified from a small number of individuals. Both species showed a high degree of overlap in the broad types of food they ingested (seed, plant material, invertebrates); however, there was considerably less overlap in the species of seeds eaten. Analysis of microhabitat use suggested that this difference was due to differential foraging between the species; the larger, bipedalN. alexis forages in the open more than the smaller, quadrupedalP. hermannsburgensis, which is found more commonly in or under hummocks of spinifex grass. Although our findings parallel patterns of morphological specialisation and differential foraging on seeds that have been described within communities of North American heteromyid rodents, we found little evidence that the foraging economics ofN. alexis orP. hermannsburgensis should depend solely or primarily on the distribution patterns of seeds. In the absence of dietary information, we suggest that ecological studies of desert rodents which focus solely on granivory, and neglect other important aspects of rodent foraging, can lead to a misinterpretation of species coexistence and community structure.

The importance of subterranean termites in semi-arid ecosystems in south-eastern Australia

In mulga, Acacia aneura, woodland in north-western New South Wales, Australia, subterranean termites constructed foraging galleries over organic debris, litter fragments, litter trains, dead wood, dead grass in perennial grass clumps and kangaroo and sheep dung. The larger quantities of litter, litter trains and dead wood in the mulga groves resulted in higher cover of termite gallery sheeting in this habitat, 6·56 ± 1·02%, than in the intergrove erosion slopes, 2·28 ± 0·32%. In the upper 20 cm of soil there were 51·1 storage galleries m−2. In mallee-spinifex habitats in south-western New South Wales, there was no evidence of subterranean termite feeding on dung or the dead stems of spinifex grass, Triodia iritans, but dead stems of malice, Eucalyptus spp. were galleried and etched by termites. The numbers of sub-surface termite storage galleries in this habitat averaged 137·5 m−2. These galleries ranged between 4·5 and 49·0 cm3. These data suggest that subterranean termites in these Australian ecosystems may be more important as detritivores and in their effects on hydrological properties of soil than has been documented for subterranean termites in the Chihuahuan Desert of North America.

Liquid sprays to assist stabilisation and revegetation of coastal sand dunes

These studies examined the use of a range of liquid sprays, compared with brush matting, as temporary means of assisting the surface stabilisation and revegetation of coastal sand dunes. Measurements were made of the effects of the stabilisers on sand stabilisation, soil moisture and spinifex grass establishment, using small plot trials at Grassy Head in eastern Australia. All treatments allowed spinifex grass to establish from seed, however there were significant differences in the ability of the liquid sprays to provide sand stabilisation and hence the long term survival of spinifex. Brush matting was superior to all sprays as a stabiliser for the establishment of spinifex. No treatments had any significant effect on soil moisture.

RESEARCH IN SOUTHERN QUEENSLAND INTO THE MANAGEMENT OF COASTAL SAND DUNES

Queensland's Beach Protection Act (1968-1974) resulted, inter alia in the formation of the Beach Protection Authority, which is responsible for investigating coastal erosion, planning remedial works, recording and evaluating results of investigations, and various other functions. Control of windblown sand and retention of vegetated and naturally stable coastal sand dunes are valuable means of decreasing coastal erosion and because of this the Authority implements a broad research program into the management of coastal dunes in Queensland. Field trials are carried out at the Authority's Dune Management Research Station on South Stradbroke Island to determine methods of repairing, stabilizing and managing coastal dunes. The research program conducted so far consists of fifteen separate field trials within four general areas of investigation:- (a) Dune Forming Fences Two trials were installed in blown-out sections of the frontal dune to compare different types of semi-permeable fences (eg. wooden slats) and brush matting (a surface mulch of tree branches) on the basis of their ability to accumulate windblown sand and initiate dune formation. (b) Dune Stabilization Techniques Three trials were installed on bare dunal areas to evaluate methods of temporary sand surface stabilization (organic mulches and spray-on materials) as an aid in establishing dune vegetation. (c) Dune Vegetation Two trials were conducted to produce and compile information on the performance of important or potentially useful dune plants. (d) Plant Nutrition Eight trials using different combinations and rates of fertilizer were used to study methods of improvement of establishment and early growth of dune stabilizing plants, particularly sand spinifex grass (Spinifex hirsutus). Good establishment and rapid early growth is required in order to accelerate, improve, and decrease the costs of, the stabilization process.