b. Young soils—Raw Soils, Recent Soils, and Anthropic
Soils
Where time is limiting, on active parts of the landscape
where erosion or deposition of sediments is occurring, Raw
and Recent Soils form. Raw Soils occur on steep slopes and
rocky outcrops, sand dunes, river flood plains, new volcanic
deposits close to active volcanoes, and tidal estuaries, where
soils show very little evidence of development and topsoils
have not yet formed. Recent Soils form on relatively young
parent materials such as river flood plain deposits; however,
Recent Soils do have some incipient soil weathering and an
A-horizon (a distinct topsoil).
Anthropic Soils occur where humans have had a strong
impact, greatly altering or rebuilding a soil by truncating,
burying, or deep mixing. Minor human impacts, such as a
disturbed A-horizon, are insufficient for a soil to qualify in
the Anthropic order. Anthropic Soils occur, for example, in
areas within cities that were recontoured during subdivision,
areas that have been restored or rebuilt following activities
such as open cast mining, Māori midden or gardening sites,
and some forest harvest sites.
c. Climate-dominated soils—Semiarid Soils, Pallic Soils,
Brown Soils, and Podzol Soils
Where soils are formed predominantly from silicic (quartzofeldspathic) rocks such as greywacke, schist, and mudstone
(or on materials derived from them such as loess and colluvium), climate is a major determinant of the soil properties. Thus a soil-climate sequence is recognised,
commencing with the Semiarid Soils in Central Otago, and
small areas of the central Waitaki River catchment, where
mean annual rainfall is less than about 500 mm. In summer
drought-prone areas, particularly around the margins of
Central Otago and along the eastern lands of both the North
and South Islands, Pallic Soils form, many on loess deposits.
On the higher hill country and areas where the rainfall is
Table 1.2 Organisation of the soil orders of the New Zealand Soil Classification in relation to age, climate, soil wetness and geological material
Dominant influence
Soil order
Young soils
Soils on recently deposited or exposed materials with minimal, or no, horizon
development and usually low clay content
Raw Soils
Recent Soils
Anthropic Soils
Mature soils
Soils that have well developed
topsoil and subsoil horizons
Climate
Soils formed mainly in quartzofeldspathic-rich materials that
show the effects of climate and associated vegetation
Semiarid Soils
Pallic Soils
Brown Soils
Podzol Soils
Wetness
Soils with prolonged high water tables
Gley Soils
Organic Soils
Geological material
Soil parent materials formed from rocks or geological deposits
that dominate the soil character: limestone, mafic material,
and tephra (including pumice and other pyroclastic materials)
Melanic Soils
Pumice Soils
Allophanic Soils
Old soils
On land surfaces with materials that have attributes of advanced weathering including high clay content
Ultic Soils
Granular Soils
Oxidic Soils
Fig. 1.13 Areal distribution of soil orders in New Zealand
16
1 Introduction
Soils
Where time is limiting, on active parts of the landscape
where erosion or deposition of sediments is occurring, Raw
and Recent Soils form. Raw Soils occur on steep slopes and
rocky outcrops, sand dunes, river flood plains, new volcanic
deposits close to active volcanoes, and tidal estuaries, where
soils show very little evidence of development and topsoils
have not yet formed. Recent Soils form on relatively young
parent materials such as river flood plain deposits; however,
Recent Soils do have some incipient soil weathering and an
A-horizon (a distinct topsoil).
Anthropic Soils occur where humans have had a strong
impact, greatly altering or rebuilding a soil by truncating,
burying, or deep mixing. Minor human impacts, such as a
disturbed A-horizon, are insufficient for a soil to qualify in
the Anthropic order. Anthropic Soils occur, for example, in
areas within cities that were recontoured during subdivision,
areas that have been restored or rebuilt following activities
such as open cast mining, Māori midden or gardening sites,
and some forest harvest sites.
c. Climate-dominated soils—Semiarid Soils, Pallic Soils,
Brown Soils, and Podzol Soils
Where soils are formed predominantly from silicic (quartzofeldspathic) rocks such as greywacke, schist, and mudstone
(or on materials derived from them such as loess and colluvium), climate is a major determinant of the soil properties. Thus a soil-climate sequence is recognised,
commencing with the Semiarid Soils in Central Otago, and
small areas of the central Waitaki River catchment, where
mean annual rainfall is less than about 500 mm. In summer
drought-prone areas, particularly around the margins of
Central Otago and along the eastern lands of both the North
and South Islands, Pallic Soils form, many on loess deposits.
On the higher hill country and areas where the rainfall is
Table 1.2 Organisation of the soil orders of the New Zealand Soil Classification in relation to age, climate, soil wetness and geological material
Dominant influence
Soil order
Young soils
Soils on recently deposited or exposed materials with minimal, or no, horizon
development and usually low clay content
Raw Soils
Recent Soils
Anthropic Soils
Mature soils
Soils that have well developed
topsoil and subsoil horizons
Climate
Soils formed mainly in quartzofeldspathic-rich materials that
show the effects of climate and associated vegetation
Semiarid Soils
Pallic Soils
Brown Soils
Podzol Soils
Wetness
Soils with prolonged high water tables
Gley Soils
Organic Soils
Geological material
Soil parent materials formed from rocks or geological deposits
that dominate the soil character: limestone, mafic material,
and tephra (including pumice and other pyroclastic materials)
Melanic Soils
Pumice Soils
Allophanic Soils
Old soils
On land surfaces with materials that have attributes of advanced weathering including high clay content
Ultic Soils
Granular Soils
Oxidic Soils
Fig. 1.13 Areal distribution of soil orders in New Zealand
16
1 Introduction