You are here: Tussock Grasslands MIS Site Contents Blue wheat grass and Rytidosperma grassland Background management information
Select from: Identification Habitat Other spp. present Vegetation history Management options
Or return to communities indexes: || High altitude || Mid altitude || Low altitude || drylands ||

Information on Saline Soil Habitats

Developing management options
The majority of tussock grassland research has focussed on determining the vegetation history of the mountain lands, and how pastoral management practices have influenced vegetation succession patterns. Only recently has grassland research started to look at the issue of progressive successional changes occurring on retired land (i.e. what vegetation changes will take place when tussock grasslands are retired from grazing and burning). The majority of studies have focussed on determining the impacts of pastoral use on induced montane fescue tussock grasslands (Festuca novae-zealandiae), the most widespread short tussock grassland found to the east of the Main Divide.

An inventory of remaining saline soil areas has been made, which provides baseline information on the distribution and characteristics of the soils, plants and animals present at each known site. While recomendations have been made to establish grazing trials so that a better understanding of how different stock or pests affect saline soil areas, no such studies have been documented. There are therefore still many information gaps to be filled.

In the meantime, the suggested management options have to draw on broad principles and "best guesses" by ecologists, or observations made by people who live and work in the tussock grasslands. Such "best guesses" may be appropriate in some situations, but not others. They will be updated as and when more information becomes available.

More about...

What are saline soil habitats?

Within New Zealand, salty soils developed inland under dry climates. They contain plants which are otherwise restricted to coastal sites, and are unique to the broad Central Otago basins (i.e. Ida valley. Manuherikia valley, Strath Taieri and Maniototo) and upper Waitaki valley in North Otago.

Saline soils are classified as Semiarid soils in the N.Z. Soil Classification (Hewitt 1992). They have a high base status in which a soil water deficit prevails over most of the growing season. In their natural state, moisture fails to penetrate deeper than the base of the soil, resulting in an accumulation of lime and soluble salts, or water rising from a saline groundwater brings salts within the rooting zone of some plants. Saline soils are characterised by having a salty (i.e. electrical conductivity of 0.8mS/cm or more) soil horizon within 60cm of the soil surface at some time of the year. Saline soils occupy small areas, and are often associated with dryland grasslands such as short tussock grasslands and dwarf grasslands, which occupy non-saline semiarid soils.

Why are saline soil habitats important?

  • They are found only in the driest parts of New Zealand.
  • While once more widespread (perhaps 40,000ha), most saline soil areas have been highly modified or eliminated by agricultural development. Those that remain are small, and have a very limited and fragmented distribution (30 known sites, none of which are larger than 100ha).
  • They provide a habitat for rare and unique plants and animals, particularly insects
  • They are reference sites for judging the influence of climate, geology, parent material and soil water on soil development.
  • They may show the influence of past climates on soil development.
(Patrick 1989; McIntosh et al 1990).

Conservation and Management of Saline Soil Habitats

Saline soil sites are of immence historical and biological importance, therefore it is imperative that the best remaining examples are actively conserved.

Current threats to the survival of the remaining saline areas are irrigation, planting of salt-bush, weed invasion, cultivation, mining and other earthworks, feral animals and increased stock pressure.

Grazing
There is general agreement that extensive sheep grazing appears to do little damage to saline soil habitats (Allen & McIntosh 1993; Johnson 1976, Patrick 1989), and that without grazing, it is possible that taller grasses could oust out the low-growing salt tolerant plants. At Flat Top Hill, Walker et al (1995) suggest that the removal of grazing disturbance may result in the invasion of palatable perennial plants at the expense of the rare native annual plants.

Johnson (1976) noted that heavier animals, such as cattle, damage the vegetation when it is wet. Allen and McIntosh (1993) recommend that cattle, deer and goats be excluded from saline soil habitats at the Patearoa saline site.

Irrigation
Irrigation border-dyking of saline soil habitats is catastrophic for the flora and fauna. Saline soils themselves may remain, and even increase but observations show that the diversity of plants and animals is severely reduced (Patrick, 1989). Where the level of salinity is affected, a change in species composition favouring the establishment and growth of exotic pasture species is likely (Allen & McIntosh 1993). Saline soil habitats therefore require protection from irrigation both in situ, and from the effects of upslope irrigation.

Fertiliser and Seed Application
The application of fertiliser and seed (whether by drilling or over-sowing and top dressing) will alter the vegetation composition in favour of pasture species (Allen & McIntosh 1993).

Saltbush Establishment
Planting of saltbush on several sites near Chatto Creek, Springvale and Galloway is equally disastrous as they grow to 3 metres and shade out the native plants and insects (Patrick 1989).

for further information on management procedures for long-term protection of salt pans (Allen & McIntosh 1995):

for recommendations relating to Central Otago salt pan sites (Allen & McIntosh 1995):

Farming and Management of Saline Soil Habitats

Irrigation schemes have allowed farmers to develop the majority of the lowland basins where saline soil habitats were once extensive, for animal grazing, and crops such as lucerne. Where saline soil habitats still exist, they tend to be only extensively sheep grazed, as the vegetation cover is minimal, less palatable and of poorer productivity than the surrounding ground cover.

    If farmers wish to intensify land use at these sites, the following points are of note:

  • Much care is required when attempting to irrigate saline soils to avoid bringing to the surface toxic levels of soluble chloride and sulphate salts of sodium and magnesium.

  • The claypan in saline soils is only slowly permeable, creating management problems

  • Salt-free soils can be polluted if saline soils are included in any "wild flooding" irrigation scheme, thereby reducing their productive capacity. Elsewhere in the world, such practices have rendered salt-free soils unproductive.

  • The productive gains of developing these sites are not likely to be great. Infact, only the deeper finer-textured salt-free soils with higher water holding capacities are likely to give a sufficiently high economic return from increased production of pastoral products where the growing season is limited by severe climate.

  • Development of remnant saline soil habitats will result in the loss of a very special habitat, which supports a unique and often rare array of native plants and animals which are adapted to these extreme conditions
(Soils info from: Molloy, L. 1988. Soils in the New Zealand landscape- the living mantle. Mallinson Rendel Publishers.)

If farmers wish to maintain a saline soil habitat, they are probably best to extensively graze sheep there. They should also avoid irrigating, cultiviating, fertilising, introducing pasture species or conducting earthworks in the area.

Buffering

The relationship an area managed for conservation purposes has with it's surrounding landscape is important. Ideally, the area should be surrounded by land which will buffer it from external influences which may compromise the conservation values.

In terms of saline soil habitats, it is imperative that the buffer zone protects it from the impacts of irrigation occuring on neighbouring land. In addition, the buffer zone may protect the area from inadvertent AOSTD drift from neighbouring land.

Weed control

Saline soil habitats occupy lowland sites, surrounded by pastorally developed land with little or now native plant component. Most of the known saline soil habitats therefore already have a significant exotic plant component. Active management will be required to ensure that weeds do not oust out the low-growing salt-tolerant native plants. Extensive grazing is likely to be the most suitable tool to acheive this (see Grazing section). However, monitoring of the area will be necessary to assess the success of any weed management programme.

Animal Pests

Some native plants appear to thrive in the open disturbed ground induced by grazing. At Flat Top Hill, Alexandra, Walker et al. (1995) noted that the rare native annual salt-tolerant herbs- Myosurus minimus subsp. novae-zelandiae, andCeratocephalus pungens were present despite a history of high stocking rates and high rabbit numbers. Rabbit grazing here is likely to be beneficial to the conservation of these species by suppressing the spread of exotic grasses and herbs which might otherwise colonise the bare ground that these native annuals require.

Rabbit grazing appears to beneficial in controlling some woody weeds, including thyme in Central Otago (Wilkinson et al. 1979; Fraser 1985; Walker 1994), sweet briar (Moore 1976; Ogle 1990) and broom (Moore 1976).

Monitoring

The management guidelines suggested are based on the best available information, and are often only "best guesses". To ensure that the management practices are achieving the desired management goal, it is crucial that the vegetation condition and composition, weed status, and animal pests are monitored. Management may have to be changed in response to the findings of such on-going monitoring.

Allen and McIntosh (1995) noted that monitoring of changes is at present ad hoc and unsystematic, depending on occasional observations made by DoC staff and scientists. GIS technology offers a means of recording changes in a systematic way which can be used for site management. They recommend that a trial monitoring site be established using GIS to record sols and vegetation data and future changes at the Pisa Flats site inititally, where the terrain is highly suitable for grid survey and systematic recording.

Management may have to be changed in response to the findings of such on-going monitoring.

Botanical information

for more information on:
  • Identification of tussock species in the field
  • Habitat information
  • Other species present
  • Overview of vegetation history of this grassland

Source of information

Choose which selection of references you want to view:

Page last updated on Wednesday, February 14, 2001