There is increasing recognition that natural ecosystems and their constituent plants and animals have their own intrinsic value. Although the human race depends on highly modified agricultural ecosystems for the necessities of life, there is a worldwide political demand for the preservation of such remnants of natural ecosystems as remain. This demand is reflected in recent legislation limiting clearing of native vegetation (including grasslands) and in a popular trend towards using native species for revegetation in many situations such as following highway construction or following mining. Funds are also becoming available for the reconstruction of plant communities when they have been destroyed or where only tiny remnants remain. Native grasses are important components of many of these ecosystems and the inherent value of our native grasses is increasingly being recognised.
Native grasses are well adapted to the Australian environment with its generally infertile soils and variable climate. Both of these environmental attributes have moulded the characteristics of our native flora, including the grasses. As a result, most of our native grasses are well adapted to surviving intermittent droughts and fires, and establishing and surviving in soils of low fertility. This general adaptation to soils of low fertility does not mean that there are no species among our grass flora with the ability to respond to high soil nutrient levels. In general terms, native grasses can be described as 'stress tolerators' with low seedling vigour, and have developed a range of different characteristics that enable their populations to survive periods of stress.
Grazing sheep and cattle were the first successful industries in Australia and the early settlers brought with them both the pasture species and the management approaches of northern Europe. Consistent attempts to replace the native grasses with introduced European pasture species were finally successful in the first half of the 20th century and required the input of appropriate fertilisers and consistently high rainfall. The result was that for a period of about 25 years from the 1950s through to the 1970s, the native grassland species were completely ignored. This 'replacement philosophy' had been alive and kicking since first settlement and is still rife in some quarters. It assumes that the addition of these 'superior' exotic species to the landscape can permanently increase the productive capacity of the land. However, the bulk of Australia's beef and wool is still grown on native grasslands, and the grazing industries represent by far the most widespread potential use for Australian native grasses. It was our pastoral industry that recognised that, for lower rainfall areas, or in exceptionally long dry periods that exotic species tended not to persist. In other areas where land values are low (areas affected by salinity, and erosion), the use of exotic species with their higher maintenance costs has prohibited their use. These are ideal situations in which to use native grasses.
The value of native grasses in the horticultural industries both as ornamentals ('feature' species) and as turf grasses has recently been recognised. Many of them are extremely attractive either as individual plants or in providing different colours and textures with the added advantage of being able to survive periods of drought with no or little additional water.
Once native grasses are established in the landscape, and in the absence of additional nutrient inputs, they can be remarkably resistant to invasion by exotic species but still require management in the form of intermittent defoliation or burning, depending on the situation.
More recently, the usefulness of native grasses in the maintenance of biodiversity and ecological integrity has been established. Since the mid 1990s the research emphasis has moved away from production related restoration goals and re-focussed on ecological restoration goals. As such it is the intrinsic value of native grasses that is providing the motivation for the further use of this valuable collection of plants. They also provide the necessary habitat for many native Australian fauna species and so are essential in native ecosystem restoration.
Past comparisons of exotic and native grasses usually compared fertilised introduced grasses with unfertilised native counterparts. It is therefore not surprising that native grasses inevitably gained a reputation as 'poor performers' in terms of forage production.
The response of native grasses to fertiliser is variable but there are some species with the capacity for very high dry matter responses under ideal conditions. Information for individual species located at the back of the Guide provide information on fertiliser responses if they are known. Generally, native grasses respond to low rates of nitrogen (50 kg/ha); at higher rates responses tend to diminish for some species.
The nutritive value of native grasses is generally considered poor but again, there is tremendous variation among species. In general terms for leafy species, the nutritive value depends more on the age of the plant, the stage of growth and the soil fertility than on the species. For most native grasses the protein content varies between 10–20% if leaves are young and actively growing and 1–8% when the plant is mature and dry or frosted. Cultivars of Microlaena and Elymus have recorded values as high as 21% and 30% respectively on the Northern Tablelands under ideal conditions. Thus, native grasses cannot, as a group, be considered to be of low nutritive value. Grazing animals actively select better quality components of a pasture and are able to do well on native pastures.
Because of the capacity of native grasses to retain a generally high proportion of dead leaf in dry periods, a time when other feed sources are unavailable, they are able to support some production when exotic species have failed. This is their true value. In higher rainfall areas this high leaf retention tends to provide a competitive advantage over other germinating plants due to a shading effect.
As with other native vegetation, native grasses have been promoted as low maintenance, low input plants. Often, however, this is confused with zero maintenance and zero input. There is some maintenance requirement for native grasses. For example, there is probably a good case for using low rates of fertiliser to manage seed production areas, but there is currently no evidence to suggest that the addition of phosphorus benefits the establishment of native grasses. The response of different native grasses to fertiliser is discussed in the individual species information sheets at the back of this Guide.
There are some general management activities that need to be undertaken to manage areas for seed production, to assist establishment or to maintain the health of existing grasslands. In particular, perennial native grasses respond well (in terms of production) to intermittent grazing. Grazing of mature plants during their dormant period can be beneficial in terms of removing annual weeds, promoting tillering (Tiller - Aerial shoot usually lateral and basal and more or less erect) and opening up swards. Areas should be periodically rested from grazing until seed set, allowing soil seed banks to be maintained. Newly sown areas require complete resting from grazing until plants have set seed, assisting in the establishment phase.
Native grasses are well adapted to fire but different species will respond differently depending on the time of burning, the fire intensity and the conditions before and after burning. In general terms, plants are more tolerant of fire when they are dormant, if they are burnt when the soil is wet and if they are not grazed following burning until they have set seed. For some species, e.g. Themeda triandra, fire may be used to promote growth and seed production. It is important however, that fire is used during the right conditions to ensure the desired result (refer to section 6.1).
Many attempts at establishing stands of native grasses have used technology devised for establishing introduced grasses of European origin. The results have often been failure. There is a need to devise methods of sowing that are specifically applicable to individual species of native grasses to reduce the number of failures so that specific species of native grasses can be sown with some confidence of satisfactory results. Until this confidence develops, the demand for native grass seeds will remain limited. There are a number of other problems associated with the development of a viable native grass seed industry but the notable lack of establishment success from many preliminary plantings is an important reason why it has been slow to develop.
The native grass seeds industry is very much in its infancy. With few commercially released varieties, the market relies heavily on opportunistic harvesting of seed from the wild. This reliance on seed collected from wild stands has led to a generally inadequate seed supply, a limited number of species available for use as well as seed quality problems, in particular genetic purity.
Wild stands of native grasses are rarely monospecific but consist of a number of different species, including weeds. The physical separation of mixed samples into pure samples of seed of the individual species presents formidable technical difficulties with many species. In addition, the size of the seed crop depends entirely on seasonal conditions. The result is a fickle supply of available seed.
The recent introduction of the Native Vegetation Conservation Act (1997) in New South Wales which, among other issues, aims to 'encourage the revegetation of land and the rehabilitation of land with appropriate native vegetation', has created a situation which will sustain a long-term demand for native seed. Similar Acts already exist in Victoria and South Australia each providing a high potential demand for native seed in eastern Australia. Within these southern and eastern states there appears to be an unwritten policy to access and use local provenance material. The supply of local provenance seed is almost impossible to meet or forecast. Experience over the past 30 years in North America has shown that there is also a place for cultivars of native grasses suitable for sowing across a wide geographical range.
Seed physical quality refers to physical purity, seed viability and germination. Because of the manner in which native grasses produce seed and the variable climatic conditions under which this is achieved, the physical quality of different seed lots is often variable. Before native grass seed is purchased or used in a revegetation or restoration program, germination percentage and purity is the minimum information required. There is no point in sowing seed that is incapable of producing seedlings. As a national survey showed, the quality of seed lots is frequently unknown, with only 37% of commercial seed suppliers providing seed with sufficient quality information. These commercial suppliers tend to focus on providing seed to the mining industry or to large roadside revegetation contracts and see limited opportunities for supplying locally harvested seed to meet the demands of the growing Landcare and community groups, despite the large scale of these revegetation projects. These groups are becoming increasingly cautious about using seed of unknown or distant origins, and have a strong demand for local plant material.
Seed can be given to a seed testing laboratory (Summary Table iv.) or tested using procedures outlined in the FloraBank guideline 8 - 'Basic germination and viability tests for native plant seed'. Here, germination and purity information can be derived from a germination test based on weight and 'other seed', respectively.
It is generally recommended that stored seed be re-tested before use if seed is greater than or equal to 5 years old.
Often it is necessary to compare different seed lots. Usually, this is done on a Pure Live Seed (PLS) or Pure Germinating Seed (PGS) basis. This is determined by multiplying pure seed by % viable seed and dividing the product by 100 for PLS, or multiplying pure seed by germination % and dividing the product by 100 for PGS.
The genetic composition of plant material used in revegetation programs is of great public concern. The use of seed of local origin, if available, is preferred according to a number of groups such as Greening Australia, Landcare and The Native Grass Resources Group. The rationale for this is based on a presumed superior adaptation of local seed material to local conditions but good experimental evidence to support this claim is generally lacking. However, the use of local provenance seed will, in practice, sometimes place undue restrictions on the revegetation process, because accessing large quantities of local provenance seed may be difficult.
Often the quality (both physical and genetic) of seed material is unknown. Seed buyers should demand this information before they purchase any seed. A minimum labelling requirement, proposed by the Australian Native Grass and Legume Seed Industry Association is given in Table 1.3.
It has been suggested that the slow seedling growth rates exhibited by Australian native grasses are among the characteristics that are associated with the survival of plants in stressful environments. However, it decreases their ability to cope with competition from weeds. In particular, annual grass weeds in situations of high disturbance (cultivation) or on newly formed mine rehabilitation sites, creates a difficult environment in which to successfully establish native grasses. There is some evidence that the increased nutrient mineralisation associated with soil cultivation and aeration swings the competitive advantage in the direction of weeds well adapted to disturbed sites. Therefore, procedures that limit the amount of cultivation will often result in better establishment of native grasses. In short, adequate weed control prior to and following seeding programs is essential.
1. Genus, species and line number
To identify the major component of the seed lot, to identify the particular line, allowing good lines of seed to be identified and to allow problems with performance to be traced back to their source
2. Collection location
GPS or direction from and distance to nearest town. This will allow the buyer to assess issues of provenance.
3. Date of collection
The age of the seed lot has a bearing on dormancy and useful life.
4. The number of normal germinating seeds
This is for the main species (per 10 g) and will take into account the chaffy impurities of the material, the presence of floral structures as well as a provision of some measure of dormancy.
This will provide the measure of seed dormancy and indicate if seed dormancy breaking treatments are necessary.
5. Other seeds, other species including native species
To be given on a percentage weight basis for each species if other seeds collectively native species contribute to > 5 % of the seed lot weight
6. Important weed seeds
Number of weed seeds per 10 g or as a %