Australasian Plant Conservation
Originally published in Australasian Plant Conservation 19(1) June - August 2010, p 21-22
‘Regrowth’ within reconstructed species-rich grasslands – observations of opportunities taken up by a range of trophic levels
Project Head: Grassy Groundcover Research Project, Greening Australia/Melbourne University, Richmond, Vic.
These images of Plovers eggs and a Plains Froglet are a few among many different animal species we now find residing in our reconstructed grasslands. Photos: Paul Gibson-Roy
Regrowth and the subsequent benefits resulting from re-establishing vegetation (e.g. opportunities for re‑colonization by other species) come in many forms. Most readily identifiable might be that which is associated with natural or man-induced disturbance such as re-growth of woody or shrub canopy following fire or clearing. However, I have noted that similar opportunities for ‘regrowth’, if this is viewed in a more expansive manner, may also be created following the consolidation of re-seeded species-rich herbaceous communities. This general restoration approach was tested by the Grassy Groundcover Restoration Project (GGRP), a partnership between Greening Australia (Victoria) and the University of Melbourne. Initiated in 2004 as a multi-regional restoration initiative across southern and western Victoria, the fundamental objective of the project was to demonstrate the effectiveness of direct sowing multi-species seed mixtures (representative of locally occurring remnant communities) on agricultural sites. However, it was also posited that, if successful, the goal of creating diverse and resilient native plant communities would in turn offer a range of niches and opportunities for colonization by other organisms from various trophic levels.
Since 2004 the GGRP has reconstructed species-rich grassland at over twenty locations covering approximately 30 ha. Indeed, in partnership with Alcoa at their Point Henry site located near Geelong the GGRPs goal is to reconstruct 150 ha of grassland over the next 15 years. Already 10 ha has been established. The most stable and diverse of these reconstructed communities occur under conditions where soil nutrient loads have been reduced. Nutrient restriction limits the capacity of weeds to dominate, improving potential for sub-dominant native species to establish and persist. One measure of the success of the GGRPs approach of setting a goal of high diversity early in the restoration cycle has been that, where complex vegetation has been maintained, colonization from other trophic levels has been observed.
In the communities established under nutrient restricted conditions there have been increases and expansion of the seeded populations through natural recruitment (or clonal expansion). Over time the structure of these communities has typically become increasingly heterogeneous as successional processes reveal individual plant and species relations developing and altering. For example, the presence of pioneer species typically declines as slower developing stress-tolerators begin to consolidate spatially and temporally. This temporal aspect of vegetation development is obvious in the grass matrix as individuals develop as larger (dominating) tussocks or as mats of forb species spread and occupy large areas within sites.
As these processes unfold surveys have revealed the ingress of many non-introduced (i.e. through the seeding program) organisms, both plant and other, increasing the complexity of these systems. In regard to those plant species not included in the seed mixes, natural recruitment from native over-storey species has been noted at many sites. For example, where resident eucalypts adjoin seeded areas (e.g. as roadside remnants or paddock trees), tree seedlings have emerged within the swards (to be managed as desired). At other sites, where for example once endemic Blackwoods (Acacia melanoxylon) are absent, individuals have been recorded emerging from the soil seed bank. Particularly interesting are conversations with landholders that reveal, at some of these locations, Blackwoods have not been present in living memory.
Many other non-plant species now inhabit our reconstructed grasslands. Because the project was undertaken in farming systems (e.g. cropped or grazed), cryptogamic layers were absent in or near the seeded areas. However, now it is common to find moss and lichen layers forming at sites. Species-rich remnant grasslands are known to harbour a diverse range of native invertebrate species, including spiders, butterflies and moths. Encouragingly, insect surveys in these seeded grasslands have revealed many colonizing native invertebrate species. Conversely, they were not found to be a feature of the low diversity (primarily introduced) vegetation found in adjoining areas. Native spiders are now a feature in the spring, spinning webs between grass culms, while native butterflies congregate on the bare ground between plants and other ‘bugs’ occupy a range of niches therein.
As the plant communities have developed, vertebrate species have been observed utilizing or residing within our grasslands. For example, burrowing activity of small native mammals and reptiles in, under and around older grass tussocks and within clumps of forb biomass is regularly noted. I also routinely observe parrots grazing grass seed or am startled when birds (e.g. quails) scatter underfoot and look down to see nests and eggs. While not easy to locate, I have also found frogs and reptiles within our reconstructed swards. It is likely that the range of invertebrates offer both a reliable and attractive food source.
At the subterranean level ‘regrowth’ also seems to be occurring. Preliminary investigations of plant roots have shown the presence of structures that are associated with functioning arbuscular mycorrhizal. This mutualistic relationship between the plant and its fungal symbiont is thought to confer benefits not only to those parties, but indirectly to other organisms that rely on functional plant communities for food and/or shelter.
In conclusion, in the process of undertaking the GGRP it has been greatly encouraging to discover that not only is it possible to reconstruct species-rich grassland (or herbaceous communities), if properly managed, these then present a wonderful opportunity for ‘regrowth’ of another type. This ‘regrowth’ is typified by the influx of non-sown species representing a range of organisms and trophic levels. If persistent, this influx enhances the diversity and function of the reconstructed community. Such novel restoration approaches provide restorationists with another opportunity to increase the range and quality of plant and animal communities in highly modified areas of Australia.