Waitakere Ranges – Elements And Interactions, Spatial VariationsPresentation Transcript
Waitakere Ranges – Elements and Interactions Spatial Variations
Element / Interaction Model GEOLOGICAL / GEOMORPHOLOGICAL SYSTEMS = RELIEF PEDOLOGICAL SYSTEM = SOILS CLIMATIC SYSTEM BIOTIC SYSTEM = VEGETATION / ANIMALS
Climate data shows the Waitakere Ranges are slightly cooler and rather wetter than the Auckland urban area
Waitakere Ranges: Albert Park in Auckland City: 17 16 15 14 11 10 12 13 15 16 17 17 Temp ( C) 160 145 190 170 200 260 240 230 175 130 160 140 Rainfall (mm) Dec Nov Oct Sep Aug Jul Jun May Apr Mar Feb Jan Month 18 17 15 14 12 11 12 14 17 19 20 20 Temp ( C) 91 95 102 120 135 142 146 103 105 94 65 75 Rainfall (mm) Dec Nov Oct Sep Aug Jul Jun May Apr Mar Feb Jan Month
Effect of Altitude: roughly 6 0 temp decrease every 1000m increase in altitude.
Waitakere’s max altitude is just over 400m ►about 3 0 decrease with altitude
Exposure to prevailing westerly winds:
Cooling effect of wind
Moist air forced to rise Rain shadow on leeward side Air warms as it descends Air cools as it rises Condensation / Precipitation Leeward side: Warmer, Drier conditions Windward side: Cooler, Wetter conditions Evaporation
The climate of the Waitakeres is sub-tropical . It lies in the path of prevailing westerly winds which are moist from passing over the Tasman Sea.
The Block Mountain of the Ranges is prone to predominately westerly winds that are strong. These winds can dry out the western flank (side) of the ranges and cause erosion (aeolian) on the cliffs and ridges.
Relief – Geology / Geomorphology
Refer back to notes about the formation / evolution of the Ranges
The Waitakere Ranges are located between Auckland City and the Tasman Sea. It was once a plateau and today rises over 400 metres above sea level. Its features include streams, valleys and gorges and it’s covered in sub-tropical rainforest.
Prominent ridgelines (e.g. Scenic Drive Scarp)
Incised stream catchments and streams eg Piha Stream
Elevated hills and plateaus
Scarps and coastal cliffs
Dune systems and sandy beaches
Formation of landforms
The topography (shape) of a landscape is determined by 2 major processes
Tectonic processes (mountain building)
Erosion processes (removal of material from one area to another)
These are caused by movement in the earths crust and cause
Block Mountains eg Waitakeres
Volcanic mountains – some Waitakere examples eg Lion Rock. Also the whole range is formed from volcanic products ie Manukau Breccia (conglomerate)
These erode (break down) the mountain landscapes, remove the rock and soil through wind, rain, river and glacial movements. River movements carry the eroded material to lowland areas and deposit it – either on a floodplain (flat lowland area) or in the sea.
Fluvial – erosion by rivers
Aeolian – erosion by wind
Weathering (chemical, biological and physical)
Erosion / Transportation / Deposition
SOIL = the transition zone between rocks and vegetation.
Soils are in a constant state of change and contains:
The soil of the Waitakeres is generally red-yellow podzolic. This is highly fertile and formed from andesitic rocks (that are high in minerals) and has a high clay content. However, soil types vary, depending on where it is located.
Parent material = Manukau Breccia (volcanic rock – a fragmented andesite)
Soil type = podzol (reddish-brown in colour)
Reasons / Patterns
High rainfall (2000mm per year) AND mild-warm temperatures
= Rapid forest growth
= decomposers (e.g. fungi)
= increased weathering
= fluvial erosion and mass-movement
= poor horizon development
Kauri / Rimu Forest soils
These trees are inefficient at cycling nutrients back to the soil. The litter they drop is acidic and makes the soil infertile
The litter remains for a long time (slower decomposition) so the soil below is leached
Grey, structureless topsoil with Yellow – brown podsol subsoil (infertile)
Silica – rich “pan” (layer) below the topsoil makes drainage difficult (poor for farming)
“ Gley” soils = Waterlogged soils around stream floodplains where the soil has a very high water content and is largely anaerobic
Sandy coastal soils where forest has grown over dunes or sand has blown over existing soil layers
Thin azonal soils on coastal cliffs / headlands
Vegetation in the Waitakere Ranges is known as “sub-tropical Rainforest”. However, there are variation within the Ranges. There are
Variations in sub-tropical forest depending on elevation and flank (west, east, north facing etc).
The forest is made up of several “layers”. The process by which this structure emerges over time is known as stratification
Epiphytes (grow in the canopy)
Lianas (grow up the tree trunks)
Ground layer (ferns, grasses. mosses etc)
Dominated by Kauri, Rimu and Northern Rata
The Emergent layer is (or was) the Kauri
Other Canopy species include:
Podocarps – Totara, Miro, Kahikatea
Broadleafs – Tawa, Rewarewa
Middle canopy (sub-canopy). These include:
Coprosma species, Mahoe, Ponga - Tree Ferns,
Nikau Palm, Lancewood,
Lower shrub and ground level has small ferns, grasses, mosses and lichens.
Clinging to these species are climbers and epiphytes . These include:
Climbers - Supplejack, Kiekie, climbing ferns,
Epiphytes – Kahakaha, Puka
Due to the high rainfall and mild temperatures The Waitakere Ranges contain:
¼ of our flowering plants
2/3 of our ferns
500 developed species
Vegetation distribution mostly influenced by micro-climates largely influenced by relief
Canopy trees (esp. Kauri and Rata), and lots of lower canopy trees – manuka, rata and rewarewa.
Ground cover consists of some ferns, grasses, and hebes.
The Humus layer is very thin, as is the A + B soil horizons. Areas of rock exposed with mosses and ferns
Larger percentage of ferns (ponga’s, grass skirt ponga’s, and nikau palms, some tall canopy trees. It is shadier and the
humus layer is thicker with a more developed soil horizon
Western flank (Tasman coast)
hardy low lying trees such as manuka / kanuka / cabbage tree / flax / etc – due to strong predominant westerly winds ,
often funnelled through gaps in the sand dunes or up over cliffs / headlands
Animals are an important feature living in our native bush. They re-distribute seeds and help the forest to grow and spread. One of the most important birds is Kereru (Native Wood Pigeon). It swallows seeds whole (really big ones too!) and poops them all over the forest. Other species include: Tui, Kaka, Silver Eye, Tomtit etc.