11
Podzol Soils
The Podzol Soil’s one to feast your eyes on
with a leached and bleached E horizon
It ‘s large scale chromatography
caused by acids from a kauri tree
Abstract
Podzol Soils are formed in association with podocarp and
beech forests in areas with good drainage and rainfall
*1200 mm yr
−1 , which provides an environment of
acid leaching. Podzol Soils cover 13% of New Zealand
and are most widespread on the South Island West Coast,
the high country of the North Island, and in Northland.
Distinctive Perch-gley Podzol Soils occur under high
rainfall on the South Island West Coast. The Podzol’s
most distinctive feature is a pale grey, or white, E horizon
beneath the topsoil. The E horizon is pale because iron,
aluminium, and silicon-bearing materials, and organic
compounds, have been moved downwards and redeposited beneath the E horizon as dark-coloured
podzolic-B horizons. The podzolic-B horizons usually
comprise an organic-rich (Bh) horizon over a reddish
iron-mineral-rich (Bs) horizon. Podzol Soils are defined
by the podzolic-B horizon or a humus- or ortstein-pan.
Podzols are extremely acidic with pH often as low as 4.
The acidity, and E-Bh-Bs horizonation, are caused by
acidified rainwater seeping downwards, mobilising and
leaching or translocating organic materials, iron, aluminium, and silicon compounds, and other nutrients
down the profile. Enlerached materials subsequently
accumulate in lower horizons where increased pH, and
microbial activity, support adsorption, and precipitation.
11.1 Important Features of Podzol Soils
11.1.1 Concept and Key Features of the Soil
Order
Podzol Soils form under a regime of intense acid leaching,
associated with acid-forming vegetation and high rainfall
and typically good drainage. Under natural forest vegetation,
the uppermost part of a Podzol Soil normally comprises one
or more organic horizons: a thick litter (L) horizon accumulated from material discarded by trees including leaves,
twigs, bark, and needles, usually together with partly
decomposed (F), and well-decomposed (H), litter horizons
on top of the mineral soil surface. The total thickness of
organic horizons under kauri trees (Agathis australis) can
attain *1.5 m (a range of *0.3–1 m is common).
Within the underlying mineral soil, the acid leaching leads
to the formation of a distinct, pale-coloured E horizon below
the litter-derived organic horizons and the topsoil (Fig. 11.1).
Below the E horizon are dark, organic-matter-rich, Bh horizons and reddish to yellowish iron-aluminium-silicon
complex-rich Bs horizons where much of the leached material is redeposited. Thin iron, humus, or densipans may also
form, some of the fine humus potentially being translocated
in suspension. In some cases, the E horizon may have been
obliterated by tree overturn or activities such as ploughing.
Therefore, Podzol Soils are defined by the presence of
organic-matter-rich (Bh) and iron-aluminium-silicon complexes (Bs) horizons in the lower subsoils, sometimes
cemented as pans. The Bs horizons are typically reddish in
© 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_11
163
Podzol Soils
The Podzol Soil’s one to feast your eyes on
with a leached and bleached E horizon
It ‘s large scale chromatography
caused by acids from a kauri tree
Abstract
Podzol Soils are formed in association with podocarp and
beech forests in areas with good drainage and rainfall
*1200 mm yr
−1 , which provides an environment of
acid leaching. Podzol Soils cover 13% of New Zealand
and are most widespread on the South Island West Coast,
the high country of the North Island, and in Northland.
Distinctive Perch-gley Podzol Soils occur under high
rainfall on the South Island West Coast. The Podzol’s
most distinctive feature is a pale grey, or white, E horizon
beneath the topsoil. The E horizon is pale because iron,
aluminium, and silicon-bearing materials, and organic
compounds, have been moved downwards and redeposited beneath the E horizon as dark-coloured
podzolic-B horizons. The podzolic-B horizons usually
comprise an organic-rich (Bh) horizon over a reddish
iron-mineral-rich (Bs) horizon. Podzol Soils are defined
by the podzolic-B horizon or a humus- or ortstein-pan.
Podzols are extremely acidic with pH often as low as 4.
The acidity, and E-Bh-Bs horizonation, are caused by
acidified rainwater seeping downwards, mobilising and
leaching or translocating organic materials, iron, aluminium, and silicon compounds, and other nutrients
down the profile. Enlerached materials subsequently
accumulate in lower horizons where increased pH, and
microbial activity, support adsorption, and precipitation.
11.1 Important Features of Podzol Soils
11.1.1 Concept and Key Features of the Soil
Order
Podzol Soils form under a regime of intense acid leaching,
associated with acid-forming vegetation and high rainfall
and typically good drainage. Under natural forest vegetation,
the uppermost part of a Podzol Soil normally comprises one
or more organic horizons: a thick litter (L) horizon accumulated from material discarded by trees including leaves,
twigs, bark, and needles, usually together with partly
decomposed (F), and well-decomposed (H), litter horizons
on top of the mineral soil surface. The total thickness of
organic horizons under kauri trees (Agathis australis) can
attain *1.5 m (a range of *0.3–1 m is common).
Within the underlying mineral soil, the acid leaching leads
to the formation of a distinct, pale-coloured E horizon below
the litter-derived organic horizons and the topsoil (Fig. 11.1).
Below the E horizon are dark, organic-matter-rich, Bh horizons and reddish to yellowish iron-aluminium-silicon
complex-rich Bs horizons where much of the leached material is redeposited. Thin iron, humus, or densipans may also
form, some of the fine humus potentially being translocated
in suspension. In some cases, the E horizon may have been
obliterated by tree overturn or activities such as ploughing.
Therefore, Podzol Soils are defined by the presence of
organic-matter-rich (Bh) and iron-aluminium-silicon complexes (Bs) horizons in the lower subsoils, sometimes
cemented as pans. The Bs horizons are typically reddish in
© 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_11
163