You are here: Tussock Grasslands MIS Site Contents Vegetation Succession

The vegetation at any given place also represents a point of time in the interactions among available plants, physical and biological disturbances that vary in severity, frequency and duration, changeable weather, and large scale climate changes.

Succession is the process of revegetation after disturbance. Complete successions begin on bare surfaces. Usually the pioneering plants form open communities that, except in the harshest of environments, are soon replaced by denser, taller communities, which are dominated by a different set of plant species. In the absence of further massive disturbances or environmental changes, steady-state or climax vegetation eventually establishes, which may change locally in time and space. However, it remains uniform overall.

Successions are primary if they begin on unweathered parent material, and secondary if they begin on soil developed under preceding vegetation. Succession in tussock grasslands is therefore secondary.

Regeneration is the process whereby species remain in a community- the death of individual plants is compensated by the establishment of seedlings or be vegetative reproduction.

At conservation workshops held in 1996, ecologists and land managers highlighted the factors influencing plant succession, which are presented in the table below.

Factors influencing plant succession in tussock grasslands
Animal disturbance	Feral animal grazing pressure depends on: - animal type and number - location - palatability of vegetation - accessibility of vegetation
	Domestic animal grazing pressure depends on: - stock type and numbers - frequency - time since last grazed - palatability of vegetation - stock can introduce weed seed
Fire	Impact of fire depends on: - frequency - timing - post burn management - intensity of fire; fire loading - presence of weeds
Weeds	Current weed status depends on: - weed species present - seed bank- composition and viability - mode of reproduction - dispersal mechanisms - stage of invasion - suitability of site - vegetation condition of grassland - whether it has been AOSTD (introduces exotic plant seed, and creates environment better suited to competitive exotic plants)
Change to watertable	e.g. drainage of red tussockland
Site fertility	Affects: - weed spread - species composition
Condition of tussock grassland	In terms of: - tussock type - tussock vigour (size; flowering; seeding; recruitment) - Intactness of tussock cover - Composition, diversity of intertussock species - Presence of weed species - Palatability and accessibility of plants

Below is a vegetation succession model developed by Colin Meurk. Assuming that a grassland is no longer disturbed by grazing or burning activities, the rate of vegetation change will be determined to a large extent by the degree of environmental stress present. Grassland sites which are cold or drought prone are likely to remain as grasslands. Those which occur in humid areas are more likely to revert to shrubland, woodland and eventually forest, given that a suitable seed source is available.