Domain A: severe salt belt

"Environments are not just containers, but are processes that change the content totally."

- Marshall McLuhan.

 
Map of Domain A: severe salt belt.
Domain A: severe salt belt.
See explanation of numbered inset below
 

Environmental character

A high energy zone experiencing strong salt-laden winds and spray. Humid year-round. Domain extends up to approximately 100m a.s.l. in most areas, reducing to lower levels in the lee of Mana Island.

Mostly very steep slopes of scree and rock outcrop that are excessively drained. Minimal soil due to high run-off. There are areas of more moderate slope southwest of Titahi Bay.

There are extremes of incident solar radiation depending on aspect, creating strong habitat preferences for wildlife. For example the Pukerua Bay escarpment has particularly high incident solar radiation year round.

Streambeds are generally undeveloped but dry creeks can flood after storms.

Shore characterised by rocky reefs and rock stacks, or steep shingle beaches.

'Natural' ecological character

Vegetation has salt and wind tolerance adaptations such as succulence, waxy cuticles, leathery leaves, tuberous roots, prostrate and scrambling habit. Mature vegetative character is of scrub and low forest of rounded crowns and even, windshorn canopy.

Important interface between land and sea for marine birds and mammals with a high number of species interdependencies.

Domain A subsections

 
Drawing of Domain A subsections.
Domain A subsections
 

1. Steep slopes and bluffs

Mobile scree, rock outcrops, pockets of loess.

Pioneer: shrubland; mingimingi (Coprosma propinqua), small-leaved pohuehue (Muehlenbekia complexa), tauhinu (Cassinia leptophylla), herbs.

Secondary: shrubland; taupata (Coprosma repens), coastal flax, mingimingi (C.propinqua), herbs, spaniard/speargrass (Aciphylla colensoi).

Mature: single-tier low forest; kaikomako (Pennatia corymbosa), akiraho (Olearia paniculata), mahoe (Melicytus ramiflorus), mapou (Myrsine australis), taupatu (C.repens), broadleaf/papauma (Grisilena littoralis), five-finger (Pseudopanax arboreus)

Recolonising shrubland is particularly vulnerable to exotic weeds because of its open nature. Fire induces dense coastal flax. Grazing reduces herbs.

2. Gullies

Erratic stream flows; mobile rubble.

Pioneer: shrubland; mingimingi (C.propinqua), small-leaved pohuehue (M.complexa), small white clematis (Clematis forsteri), herbs.

Secondary: shrubland; taupatu (C.repens), coastal flax, mingimingi (C.propinqua), herbs.

Mature: single-tier forest; karaka (Cornynocarpus laevigatus), kohekohe (Dysoxylum spectabile), titoki (Alectryon excelsus), kaikomako (P.corymbosa), mahoe (M.ramiflorus).

3. Toe slopes

Toe slopes with high incident solar radiation year-round are ideal lizard and penguin habitat. This unit is often relatively warm and sheltered from the strongest winds.

Mature: shrubland; mingimingi (C.propinqua), small-leaved pohuehue (M.complexa), clematis (Clematis sp.), herbs.

4. Rock stacks/rock pools/seepages

Roosting, feeding and nesting habitat for seabirds and kingfishers; areas of tidal reef are suitable for seals.

Herbs and rushes tolerant of salt encrustation and brackish water.

Wildlife is vulnerable to predation and human disturbance. Marine organisms are vulnerable to over-harvesting.

Continue to Domain B or return to Porirua's Ecological Sites Inventory.