13
Raw Soils
Youngest of young, barely soil at all
where lavas flow or tephras fall,
mudflats, sand-dunes, or a landslide scar
That’s where you’ll find the Raw Soils are.
Abstract
Raw Soils have minimal evidence of soil development,
usually because of a short time since the parent materials
were deposited or exposed at the land surface. The Raw
Soils are associated with some of New Zealand’s most
spectacular scenic landscapes. Raw Soils are scattered
throughout New Zealand, particularly in association with
high mountains (eroding alpine rock areas and active
screes), braided rivers, beaches and tidal estuaries,
non-stabilised sand dunes, recently emplaced lavas or
tephras, and active geothermal areas. They cover about
3% of New Zealand (about 700,000 ha). Raw Soils lack a
distinct topsoil or the topsoil is very thin (<5 cm) and
they have no B horizon. The soil profile properties,
therefore, correspond largely with those of the parent
materials.
13.1 Important Features of Raw Soils
13.1.1 Concept and Key Features of the Soil
Order
Raw Soils are the youngest of soils with minimal evidence
of soil development, usually due to a short time since the
parent materials were deposited or exposed at the land surface. Raw Soils lack a distinct topsoil or the topsoil is very
thin (less than 5 cm) and there are no B horizons formed as
a result of pedogenic (soil forming) processes. Some Raw
Soils are fluid at a shallow depth (e.g. on tidal mudflats).
Raw Soils occur in environments where the development of
topsoils (and other horizons) is prevented by rockiness, active erosion, or active deposition including beach sands and
active sand dunes, actively eroding alpine rock areas, active
screes, lagoons, tidal estuaries, braided river beds, areas of
recently deposited tephra or alluvium (flood deposits),
landslide erosion scars or runout deposits, and active
hydrothermal areas.
Raw Soils were introduced as a soil order in New Zealand
in 1992 when the New Zealand Soil Classification was first
published, mainly because they are regarded as soil by
engineers. Some Raw Soils also have potential to be protected from flooding or erosion and undergo development
for agriculture and so it is important to recognise and
understand their limitations and potential (Fig. 13.1). However, the occurrence of Raw Soils indicates a dynamic
environment that is likely to present hazards to most land
uses.
The properties of Raw Soils generally coincide with those
of the soil parent material and so may vary widely from
loose unconsolidated sand to hard in-situ bedrock. Thus
there is no one ‘typical’ Raw Soil. While Raw Soils generally do host some life, and may have small amounts of
accumulated soil organic matter, many lack the soil organic
matter needed to store and supply nitrogen, phosphorus,
sulphur, and other nutrients required to support a substantial
plant and animal biomass. Due to short time frames and low
nutrient status of most Raw Soils, the natural vegetation
cover, if present, is generally sparse, consisting of colonising
species including ephemeral herbaceous plants, mosses, and
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
A. E. Hewitt et al., The Soils of Aotearoa New Zealand, World Soils Book Series,
https://doi.org/10.1007/978-3-030-64763-6_13
199
Raw Soils
Youngest of young, barely soil at all
where lavas flow or tephras fall,
mudflats, sand-dunes, or a landslide scar
That’s where you’ll find the Raw Soils are.
Abstract
Raw Soils have minimal evidence of soil development,
usually because of a short time since the parent materials
were deposited or exposed at the land surface. The Raw
Soils are associated with some of New Zealand’s most
spectacular scenic landscapes. Raw Soils are scattered
throughout New Zealand, particularly in association with
high mountains (eroding alpine rock areas and active
screes), braided rivers, beaches and tidal estuaries,
non-stabilised sand dunes, recently emplaced lavas or
tephras, and active geothermal areas. They cover about
3% of New Zealand (about 700,000 ha). Raw Soils lack a
distinct topsoil or the topsoil is very thin (<5 cm) and
they have no B horizon. The soil profile properties,
therefore, correspond largely with those of the parent
materials.
13.1 Important Features of Raw Soils
13.1.1 Concept and Key Features of the Soil
Order
Raw Soils are the youngest of soils with minimal evidence
of soil development, usually due to a short time since the
parent materials were deposited or exposed at the land surface. Raw Soils lack a distinct topsoil or the topsoil is very
thin (less than 5 cm) and there are no B horizons formed as
a result of pedogenic (soil forming) processes. Some Raw
Soils are fluid at a shallow depth (e.g. on tidal mudflats).
Raw Soils occur in environments where the development of
topsoils (and other horizons) is prevented by rockiness, active erosion, or active deposition including beach sands and
active sand dunes, actively eroding alpine rock areas, active
screes, lagoons, tidal estuaries, braided river beds, areas of
recently deposited tephra or alluvium (flood deposits),
landslide erosion scars or runout deposits, and active
hydrothermal areas.
Raw Soils were introduced as a soil order in New Zealand
in 1992 when the New Zealand Soil Classification was first
published, mainly because they are regarded as soil by
engineers. Some Raw Soils also have potential to be protected from flooding or erosion and undergo development
for agriculture and so it is important to recognise and
understand their limitations and potential (Fig. 13.1). However, the occurrence of Raw Soils indicates a dynamic
environment that is likely to present hazards to most land
uses.
The properties of Raw Soils generally coincide with those
of the soil parent material and so may vary widely from
loose unconsolidated sand to hard in-situ bedrock. Thus
there is no one ‘typical’ Raw Soil. While Raw Soils generally do host some life, and may have small amounts of
accumulated soil organic matter, many lack the soil organic
matter needed to store and supply nitrogen, phosphorus,
sulphur, and other nutrients required to support a substantial
plant and animal biomass. Due to short time frames and low
nutrient status of most Raw Soils, the natural vegetation
cover, if present, is generally sparse, consisting of colonising
species including ephemeral herbaceous plants, mosses, and
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
A. E. Hewitt et al., The Soils of Aotearoa New Zealand, World Soils Book Series,
https://doi.org/10.1007/978-3-030-64763-6_13
199