www.elsevier.com/locate/geoderma

Geoderma 120 (2004) 259–272

Podzol formation in sandy soils of Finland

D.L. Mokmaa,*, M. Yli-Hallab, K. Lindqvistc

aDepartment of Crop and Soil Sciences, Michigan State University, East Lansing, MI 48824-1325, USAbMTT Agrifood Research Finland, FIN-31600 Jokioinen, Finland

cGeological Survey of Finland, P.O. Box 96, FIN-02150 Espoo, Finland

Received 19 June 2002; received in revised form 23 July 2003; accepted 17 September 2003

Available online 1 December 2003

Abstract

Podzolization occurs quickly in acidic parent materials with addition of acidic litter from coniferous trees. This study

was conducted to evaluate Podzol formation and estimate lengths of time required to meet morphological and chemical

criteria of podzolic B horizon and spodic horizon in Finland. Soil color, organic C, ODOE, and extractable Al and Fe were

measured in a seven-pedon chronosequence (230–1800 years) and four older pedons (8300–11,300 years). The bulk

mineralogical composition of the BC and C horizons was uniform with quartz, plagioclase and K-feldspar as main

components and amphibole, illite and chlorite as minor components. The fine ( < 5 Am) fraction of selected samples was

primarily amorphous allophone-like material with some mixed-layered illite–vermiculite. All pedons in the study met the

criteria for albic horizons according to the FAO–Unesco, World Reference Base (WRB) and Soil Taxonomy systems.

According to the FAO–Unesco system, all pedons had spodic B horizons and were classified as Podzols. According to the

WRB system, none of pedons of the chronosequence had spodic horizons, whereas the older pedons met the criteria for a

spodic horizon. About 4780 years were required to form a spodic horizon according to the WRB system. The oldest pedon

of the chronosequence and the older pedons had spodic horizons according to Soil Taxonomy, but the younger pedons

failed to meet the spodic horizon criteria. About 1520 years were required to form a spodic horizon that met the color and

organic C criteria of Soil Taxonomy, whereas it took about 4780 years to meet the required accumulation of Fe and Al.

This study points out the discrepancy between the color criteria and the criteria reflecting the accumulation of Al, Fe and

organic matter in the B horizon.

D 2003 Elsevier B.V. All rights reserved.

Keywords: Podzolization; Spodic horizon; Morphology; Chemical criteria; Chronosequence; Mineralogical composition

1. Introduction

Podzol morphology traditionally consists of a

light-colored eluvial horizon (E), characterized by

0016-7061/$ - see front matter D 2003 Elsevier B.V. All rights reserved.

doi:10.1016/j.geoderma.2003.09.008

* Corresponding author. Fax: +1-517-353-5174.

E-mail address: mokma@msu.edu (D.L. Mokma).

bleached, uncoated sand grains, and a dark reddish-

colored illuvial horizon (Bhs or Bs), containing

accumulated organic matter and Al oxides with or

without Fe. Podzol soils are common in forests of

the Nordic countries and northern parts of Russia.

Acidic-parent materials and litter from the coniferous

trees are conducive to podzolization of these soils. In

D.L. Mokma et al. / Geoderma 120 (2004) 259–272260

the Soil Geographic Database of Europe at scale of

1:1,000,000 (European Soil Bureau, 2000), these

areas are dominated by Podzols.

Several studies from different parts of the world

report on the duration of time needed for the develop-

ment of a podzolic morphology. The minimum time

required for the development of a thin E horizon

immediately below the forest floor in Alaska, USA

was 75 years (Crocker and Dickson, 1957), whereas

Chandler (1942) reported that at least 500 years and

more likely 1000 years were required for a Podzol

profile to form in the same environment. About 370

years were required to form a Podzol profile in sandy

beach deposits in British Columbia, Canada (Singleton

and Lavkulich, 1987). Free iron oxides did not accu-

mulate until after 205 years of soil formation in

California, USA (Dickson and Crocker, 1954). Iron

translocation was evident after 300 years in New South

Wales, Australia (Burges and Drover, 1953) but about

1900 years were required before there was evidence of

eluviation and illuviation in calcareous materials in

Ontario, Canada (Protz et al., 1984). A distinct E

horizon was observed in a pedon on a 3000-year-old

beach deposit in Michigan, USA, but the pedon on a

2250-year-old surface did not have a distinct E horizon

(Franzmeier and Whiteside, 1963). More than 4000

years but less than 10,000 years were required for a

spodic horizon to form in Michigan (Barrett and

Schaetzl, 1992).

Most of the estimates required for the development

of a podzolic morphology in the Nordic countries range

between a few hundred and a thousand years. Jauhiai-

nen (1972) concluded that 100–350 years were re-

quired for a chemically differentiated iron Podzol to

form in Lapland, Finland. A chemical Podzol (mini-

mumAl and Fe in E horizon andmaximumAl and Fe in

B horizon) formed within 200–300 years, whereas a

visual Podzol (lighter colored eluvial horizon and

redder/darker colored illuvial horizon) required 400–

500 years in Finland (Jauhiainen, 1973). A visible E

horizon formed in about 120 years but a podzol profile

took 1000–1500 years in northern Sweden (Tamm,

1950). However, Starr (1991) reported that a pedon on

the 339-year-old beach in Central Ostrobothnia, Fin-

land, lacked a Podzol profile whereas pedons on

beaches 1019 years old and older were podzolized.

Another study from the similar area agrees that more

than 330 years but less than 1200 years were necessary

for a recognizable Podzol profile to form in the district

of Oulu, Finland (Petaja-Ronkainen et al., 1992). A

general estimate of 500–1000 years has been given for

the formation of a typical Podzol profile in Finland

(Aaltonen, 1952) while a visible iron Podzol developed

in about 500 years in Sweden (Bergqvist and Lind-

strom, 1971).

One must distinguish between soils that exhibit

signs of podzolization but do not meet the criteria

to be classified as Podzols or Spodosols and soils in

which the processes have proceeded enough for the

soil to be classified as Podzols according to the

FAO–Unesco system (FAO, 1990), or World Ref-

erence Base for Soil Resources (WRB) (FAO, 1990)

or as Spodosols according to Soil Taxonomy (Soil

Survey Staff, 1999). It is impossible to analyze all

pedons observed when mapping soils, therefore soil

mappers depend on morphological properties or

chemical properties that can be measured in the

field to classify pedons. An underlying assumption

in soil classification is that criteria based on mor-

phological properties and those based on laboratory

analyses will give the same classification.

Although many authors have used chronosequences

to study podzolization and some have classified their

pedons (Franzmeier and Whiteside, 1963; Jauhiainen,

1972, 1973; Moore, 1976; Starr, 1991; Barrett and

Schaetzl, 1992), none have studied the length of time

necessary to meet individual Podzol or Spodosol clas-

sification criteria. The objective of this study was to

examine Podzol formation in relation to soil properties

used to classify Podzols or Spodosols in sandy soils of

Finland. Morphological and chemical properties of a

chronosequence of seven relatively young pedons and

four older pedons were measured to determine the

length of time required for B horizons to met the criteria

of Podzols or Spodosols of the FAO–Unesco, WRB

and Soil Taxonomy.

2. Materials and methods

The chronosequence of soils was located along the

southern coast of Finland near Siuntio Pickala (Fig. 1).

Continued isostatic uplift of land in Finland allows the

study of soil formation, especially of very young soils.

Ages of the pedons were estimated using the shoreline

displacement curve for the Tammisaari–Pernio area of

Table 2

Particle size distribution of selected lower B and C horizons

Age Horizon Sand Silt Clay

Fig. 1. Location of pedons studied. Siuntio is the location of the seven-pedon chronosequence.

D.L. Mokma et al. / Geoderma 120 (2004) 259–272 261

Finland (Eronen et al., 2001). Four older Podzol pedons

were described and sampled, one each near Jalasjarvi,

Mikkeli, Sotkamo and Toholampi, the ages of which

were estimated using the shoreline displacement data

of the respective areas. These pedons developed from

sandy parent materials under similar vegetation and

climate (Table 1). The vegetation at Jalasjarvi, Siunto

and Sotkamo were predominantly Scotch pine (Pinus

sylvestris) with some Silver birch (Betula pendula). At

Table 1

Native vegetation and mean annual soil temperature (MAST) of the

pedon locations

Location Vegetation MAST (jC)a

Siunto Scotch pine (P. sylvestris) 5

Toholampi Scotch pine Norway

spruce (P. abies)

5

Jalasjarvi Scotch pine 4

Mikkeli Scotch pine Norway spruce 6

Sotkamo Scotch pine 3

a Based of the information presented by Yli-Halla et al. (2001).

Mikkeli grass in rotation with small grains and at

Toholampi potato were grown the year of sampling

with Scotch pine and Norway spruce (Picea abies)

bordering the fields. The mean annual precipitation is

500–600 mm. All soils of the present study were well

(years BP) (%) (%) (%)

0 C 100 0 0

230 C 97 2 1

340 C 96 3 1

450 BC 100 0 0

560 C 100 0 0

670 C 100 0 0

900 BC 95 5 0

1800 BC 98 2 0

8300 Bhsm 98 1 1

9100 Bs 96 2 2

10,700 Bs3 99 1 0

11,300 BC2 82 16 2

D.L. Mokma et al. / Geoderma 120 (2004) 259–272262

drained. The sites consisted of beach deposits or glacial

outwash and were relatively homogenous in texture

(Table 2). The 11,300-year-old pedon had more silt

than the younger pedons.

A sample for time 0 of soil formation was taken at

the edge of the sea (0 m above sea level). The site was

not vegetated and was subject to water saturation from

wave action. Seven pedons further inland were de-

scribed and sampled: one each at 1, 1.5, 2, 2.5, 3, 4 and

8 m above sea level with ages of 230, 340, 450, 560,

670, 900 and 1800 years before present, respectively.

Four pedons were located and described at each eleva-

tion and a representative pedon was selected for sam-

pling and chemical analyses.

Organic C was determined using the Leco dry

combustion apparatus (Laboratory Equipment, St. Jo-

seph, MI). Soil pH was measured in water. Al and Fe

were extracted with ammonium oxalate (pH 3.0),

sodium citrate–dithionite and sodium pyrophosphate

(Soil Survey Staff, 1996). The optical density of the

oxalate extract (ODOE) was measured as an indicator

of organic C associated with amorphous materials.

Particle size distribution was determined using the

pipette method after digestion with hydrogen peroxide.

The pedons were classified according to Soil Taxono-

my (Soil Survey Staff, 1999), the FAO–Unesco system

(FAO, 1988) and the World Reference Base for Soil

Resources system (WRB) (FAO, 1998) assuming that

the pedons have a cryic soil temperature regime (Yli-

Halla and Mokma, 1998; Yli-Halla et al., 2001).

The bulk mineralogical composition of samples

from BC and C horizons was determined with the X-

ray diffraction technique using a Philips X’Pert MPD

instrument equipped with a vertical goniometer, sam-

ple spinner and reflected beam monochromator. A

semi-quantitative estimation of the minerals identified

was calculated using the Chung method (Snyder and

Bish, 1989) applying experimentally determined refer-

ence intensity ratios. For the purpose of closer obser-

vation of possible clay phases, fine ( < 5 Am) fractions

were prepared from six samples by sedimentation in

deionized water according to Stokes’ law. The < 5 Amfraction, rather than the < 2 Am fraction, was selected

because of the small amount of fine material. Two

oriented X-ray preparations were made of each fine

fraction using the Millipore Filter Transfer Method

(Moore and Reynolds, 1997) and scanned over the

low angle region (2–30j 2h). After scanning the air-

dried preparations, the preparations were heated to 550

jC for 1 h, treated with ethylene glycol for 24 h and

scanned. Clay minerals were identified according to

Brown and Brindley (1984).

3. Results and discussion

The texture and color of the C horizons of the

chronosequence pedons were similar (Tables 2 and

3), therefore differences in the sola were the result of

pedogenic processes rather than parent material differ-

ences. The C horizons had 95–100% sand, 0–5% silt

(except the 11,300-year-old pedon), and < 3% clay.

All seven pedons of the chronosequence showed

evidence of translocation of C, Al and Fe; lighter

colored E horizon with redder and darker colored B

horizon (Table 3). The four older pedons (8300,

9100, 10700 and 11300 years BP) had very distinct

zones of eluviation and illuviation (Table 4). The

230-year-old pedon of the chronosequence had

visual evidence of translocation (Table 3). Chemical

evidence for translocation was not clear in the 670-

year-old pedon but was clear in the 900-year-old

pedon (Table 5). This finding is contrary to that of

Jauhiainen (1973) who was able to distinguish a

podzol chemically before visually. The time for

evidence of translocation in this chronosequence

was much less than that (3000–4000 years) in

Michigan, USA (Franzmeier and Whiteside, 1963;

Barrett and Schaetzl, 1992) and Ontario, Canada

(Protz et al., 1984).

Thickness of E horizons tended to increase with

time but there was not a uniform increase. Thick-

ness of Bs horizons increased from 23 cm (230

years) to 75 cm (1800 years). Solum thickness

increased with time from 46 cm in the 230-year-

old pedon to 107 cm in the 1800-year-old pedon.

The Toholampi pedon (about 8300 years), Sotkamo

pedon (about 10,700 years) and Jalasjarvi pedon

(about 9100 years) had E horizons that ranged from

11 to 28 cm thick (Tables 4 and 6) and B horizons

that ranged from 25 to 65 cm thick. The Mikkeli

pedon (about 11,300 years) had a Bs horizon 16 cm

thick. Some or all of the E horizons in the Toho-

lampi and Mikkeli pedons had been mixed into the

Ap horizon. The Toholampi and Sotkamo pedons

had ortstein, cemented spodic materials. The Jalas-

Table 3

Morphological properties of the pedons in the chronosequence near Siuntio Pickalaa

Time (years BP) Horizon Depth (cm) Texture Color Structure Boundary

0 C 0–15 s 10YR 5/2 0sg

230 O 0–2 As

A 2–10 s As

E 10–23 s 10YR 4/1 0sg As

10YR 6/1, dry

Bs 23–46 s 7.5YR 3/4 1msbk Aw

C 46–72 s 10YR 5/2 0sg

340 O 0–2 As

A 2–9 s As

E 9–20 s 10YR 4/1 0sg As

10YR 6/2, dry

Bs 20–57 s 7.5YR 3/4 1msbk aw

C 57–75 s 10YR 5/2 0sg

450 O 0–5 7.5YR 2.5/2 1mpl as

A 5–9 s 10YR 2/1 1msbk as

E 9–13 s 10YR 5/2 0sg as

10YR 6/3, dry

Bs 13–61 s 7.5YR 4/4 1msbk aw

C 61–80 s 10YR 5/3 0sg

560 O 0–3 as

A 3–10 s 1msbk as

E 10–20 s 10YR 5/2 0sg as

10YR 7/2, dry

Bs 20–63 s 7.5YR 4/3 1msbk aw

C 63–80 s 10YR 5/2 0sg

670 O 0–2 as

A 2–8 s 1msbk as

E 8–18 s 10YR 5/2 0sg as

10YR 6/2, dry

Bs 18–67 s 7.5YR 4/3 1msbk aw

C 67–84 s 10YR 5/2 0sg

900 O 0–4 5YR 3/2 1mpl as

A 4–7 s 10YR 3/1 1msbk as

E 7–14 s 10YR 6/3 0sg as

10YR 7/3, dry

Bs 14–66 s 7.5YR 4/4 1csbk aw

C 66–87 s 10YR 5/3 0sg

1800 O 0–11 7.5YR 2.5/3 1mpl as

A 11–14 s 10YR 3/1 1fsbk as

E 14–32 s 10YR 5/2 1msbk aw

10YR 6/3, dry

Bs1 32–71 s 7.5YR 3/4 (70%) 1msbk cw

7.5YR 4/4 (20%)

7.5YR 2.5/3 (10%)

Bs2 71–107 s 7.5YR 4/4 (80%) 1msbk cw

7.5YR 2.5/3 (20%)

C 107–117 s 10YR 5/3 1msbk

a Symbols used are given in Soil Survey Manual (Soil Survey Division Staff, 1993).

D.L. Mokma et al. / Geoderma 120 (2004) 259–272 263

jarvi pedon had banded ortstein, probably formed at

the level of previous ground water. The E horizons

in these older pedons were light gray. The boundary

between the E and B horizons in the Mikkeli,

Sotkamo, and Jalasjarvi pedons was wavy, likely

the result of preferential flow of soil water.

Table 4

Morphological properties of the older pedonsa

Time (years BP) Horizon Depth (cm) Texture Color Structure Boundary

Toholampi

8300 Ap 0–32 fs 10YR 3/2 1msbk as

E 32–45 fs 10YR 6/3, dry 0sg as

Bhsm 45–58 fs 7.5YR 3/4 and 0m cs

2.5YR 2.5/1

Bs 58–65 fs 7.5YR 4/4 1msbk cs

BC 65–75 fs 10YR 5/4 0sg as

C 75–90 fs 2.5YR 6/3 0sg

Jalasjarvi

9100 O 0–25 sapric 5YR 2.5/2 pl as

E 25–36 s 10YR 7/2 0sg aw

Bhs 36–67 s 7.5YR 2.5/2 2fsbk cw

Bs 67–93 s 7.5YR 3/4 1msbk cw

BC 93–115 s 10YR 5/4 1fsbk cw

C1 115–142 sb 10YR 4/4 1mpl as

C2 142–170 s 10YR 5/3 1mpl

Sotkamo

10,700 Oe 0–3 hemic 7.5YR 3/2

Oa 3–8 sapric 5YR 2.5/2 as

E 8–36 fs 10YR 7/1 0sg aw

10YR 8/1, dry

Bhsm 36–57 fs 2.5YR 2.5/1 and 0m cs

7.5YR 4/4

Bs1 57–63 ls 10YR 5/6 1msbk cs

Bs2 63–70 fsl 10YR 4/3 1msbk as

Bs3 70–101 s 7.5YR 5/6 1csbk as

2Cg1 101–146 fslc 2.5YR 5/2 1mpl as

c3p 5YR 4/6

2Cg2 146–153 fslc 2.5YR 6/2 1mpl

f2p 10YR 4/4

Mikkeli

11,300 A1 0–10 s 10YR 5/4 1fsbk cs

A2 10–14 s 10YR 3/2 1fsbk as

E 14–18 s 2.5YR 5/2 1fsbk as

Bs 18–25 s 7.5YR 4/4 1fsbk cw

BC1 25–71 s 10YR 4/4 1msbk cs

BC2 71–111 ls 10YR 4/1 1cpl cs

Cg 111–150 ls 10YR 5/2 1cpl

a Symbols used are given in Soil Survey Manual (Soil Survey Division Staff, 1993).b Stratified with loamy fine sand and coarse sand.c Stratified with silt loam.

D.L. Mokma et al. / Geoderma 120 (2004) 259–272264

The cool, humid climate and the acidic liter

produced by Scotch pine favors podzolization of

the acidic parent materials prevailing in Finland. In

a greater than 7000-year-old pedon near Helsinki

(pedon 1 in Mokma et al., 2000) and in a 9000-year-

old pedon near Jokioinen (pedon 1 in Yli-Halla and

Mokma, 2001), both under Scotch pine, were mor-

phologically only slightly more developed than the

1800-year-old pedon at Siuntio. These pedons mar-

ginally met the chemical criteria. The Helsinki and

Jokioinen pedons developed from glacial till and had

a few percent of clay and silt. Another forested

Table 5

Selected chemical properties of the pedons in the chronosequence

Time Horizon pHa Org. Oxalate Citrate–dithionite Pyrophosphate

(years BP) C (%)ODOE Al

(%)

Fe

(%)

Al + 1/2Fe

(%)

Al

(%)

Fe

(%)

Al + Fe

(%)

Al

(%)

Fe

(%)

Al + Fe

(%)

0 C 5.4 0.1 0.09 0.01 0.02 0.02 0.01 0.05 0.06 0.01 0.02 0.03

230 E 4.8 0.5 0.04 0.02 0.03 0.04 0.03 0.06 0.09 0.02 0.03 0.05

Bs 5.5 (5.3) 0.2 0.02 0.03 0.04 0.05 0.03 0.07 0.10 0.04 0.03 0.07

BC 5.3 0.3

340 E 4.5 0.4 0.03 0.02 0.04 0.04 0.02 0.07 0.09 0.02 0.03 0.05

Bs 5.6 (5.5) 0.3 0.03 0.04 0.05 0.06 0.03 0.07 0.10 0.04 0.03 0.07

C 5.2 0.2 0.04 0.03 0.02 0.04 0.03 0.03 0.06 0.03 0.01 0.04

450 E 5.0 0.3 0.03 0.02 0.04 0.04 0.02 0.07 0.09 0.03 0.04 0.07

Bs1 5.4 (5.3) 0.3 0.04 0.04 0.03 0.06 0.04 0.06 0.10 0.06 0.03 0.09

Bs2 5.3 (5.1) 0.3 0.03 0.05 0.03 0.07 0.05 0.06 0.11 0.05 0.02 0.07

Bs3 5.4 (5.2) 0.2 0.02 0.03 0.04 0.05 0.04 0.09 0.13 0.04 0.03 0.07

BC 5.3 0.2 0.03 0.03 0.04

560 E 4.9 0.4 0.03 0.01 0.03 0.02 0.02 0.07 0.09 0.01 0.02 0.03

Bs 5.1 (5.8) 0.4 0.05 0.05 0.05 0.08 0.06 0.10 0.16 0.07 0.07 0.14

C 5.3 0.1 0.01 0.02 0.02 0.03 0.02 0.04 0.06 0.02 0.01 0.03

670 E 5.0 0.7 0.02 0.03 0.04 0.05 0.03 0.08 0.11 0.03 0.02 0.05

Bs 5.4 (5.2) 0.2 0.04 0.03 0.05 0.06 0.03 0.08 0.11 0.04 0.05 0.09

C 5.4 0.1 0.01 0.02 0.03 0.04 0.02 0.07 0.09 0.02 0.01 0.03

900 E 4.9 0.3 0.03 0.03 0.03 0.04 0.03 0.08 0.11 0.03 0.04 0.07

Bs1 5.7 (5.5) 0.2 0.03 0.08 0.05 0.10 0.08 0.08 0.16 0.09 0.04 0.13

Bs2 5.7 (5.4) 0.2 0.02 0.07 0.05 0.10 0.08 0.08 0.16 0.09 0.05 0.14

Bs3 5.5 (5.3) 0.1 0.02 0.06 0.04 0.08 0.07 0.07 0.14 0.07 0.03 0.10

1800 E 4.7 0.3 0.01 0.02 0.01 0.02 0.02 0.03 0.05 0.02 0.01 0.03

Bs1 5.0 (4.8) 0.7 0.15 0.12 0.02 0.13 0.13 0.03 0.16 0.15 0.02 0.17

Bs2 4.8 (4.8) 0.6 0.15 0.11 0.01 0.12 0.11 0.01 0.12 0.14 0.01 0.15

BC 4.8 0.5 0.10 0.01 0.10 0.09 0.01 0.10 0.11 0.01 0.12

a pH in 1:2.5 soil/water ratio; pH in parenthesis is in 1:1 soil/water ratio.

D.L. Mokma et al. / Geoderma 120 (2004) 259–272 265

pedon near Jokioinen (pedon 2 in Yli-Halla and

Mokma, 2001), approximately 8000 years old,

lacked an albic horizon but developed under spruce

and pine. This pedon had a fine-loamy texture rather

than the sandy texture of the soils in this study.

Parent material played a role in the podzolization of

these pedons.

3.1. Mineralogical composition

The bulk mineralogical composition of all 12 sam-

ples studied was very similar (Table 7). Quartz, pla-

gioclase and K-feldspar were the dominant minerals

with less than 2% each of mica, chlorite and amphibole.

The small amount of mica precluded a more exact

identification of the mica; however, the occasional

appearance of the 002-reflection suggested a dioctahe-

dral nature (Wilson, 1987). Trace amounts of hemitate

were observed inmost samples. No clay minerals of the

smectite or kaolinite groups were identified in these

lower B and C horizon samples. The observed compo-

sition is similar to that found in Fennoscandia by

Melkerud et al. (2000). The uniform mineralogical

composition of the selected samples indicates a similar

origin in terms of minerals present, either granitic or

gneissose (Makite et al., 1999). Jauhiainen (1973)

proposed a similar parent material for sandy soils on

the coastal plain of northwest Finland.

The fine ( < 5 Am) of six selected B or BC horizon

samples showed only minor amounts of clay minerals.

The main minerals present were quartz and plagio-

clase with lesser amounts of K-feldspar (Table 8),

similar to those in the bulk samples. Poorly crystal-

line, allophone-like material was abundant in three

samples. The clay minerals identified included chlo-

rite, illite and mixed-layered illite–vermiculite. The

Table 6

Selected chemical properties of the older pedons

Time Horizon pHa Org. Oxalate Citrate–dithionite Pyrophosphate

(years BP) C (%)ODOE Al

(%)

Fe

(%)

Al + 1/2Fe

(%)

Al

(%)

Fe

(%)

Al + Fe

(%)

Al

(%)

Fe

(%)

Al + Fe

(%)

Toholampi

8300 E 6.3 (6.0) 0.1 0.01 0.01 0.02 0.02 0.02 0.05 0.07 0.02 0.01 0.03

Bhsm 5.7 (5.5) 1.6 0.62 0.35 0.70 0.70 0.34 0.76 1.10 0.38 0.59 0.97

Bs 5.9 (5.4) 1.4 0.35 0.43 0.75 0.80 0.36 0.78 1.14 0.42 0.54 0.96

BC 5.9 (5.6) 0.15 0.22 0.38 0.41 0.21 0.47 0.68 0.23 0.30 0.53

Jalasjarvi

9100 E 4.2 0.8 0.05 0.03 0.12 0.09 0.02 0.12 0.14 0.02 0.08 0.10

Bhs 4.9 2.8 0.39 1.59 0.28 1.73 0.54 0.49 1.02 0.59 0.19 0.78

Bs 4.8 3.2 0.56 1.50 0.33 1.66 0.75 0.52 1.27 0.62 0.18 0.80

Sotkamo

10,700 E 4.3 0.2 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.01 0.01 0.02

Bhsm 5.1 (5.2) 2.7 0.55 0.95 0.93 1.41 0.95 1.13 2.08 1.09 0.80 1.89

Bs1 5.4 1.5 0.26 0.59 0.31 0.74 0.52 0.39 0.91 0.55 0.24 0.79

Bs2 5.3 0.7 0.09 0.36 0.09 0.40 0.33 0.14 0.47 0.28 0.08 0.36

Bs3 5.3 (5.4) 0.8 0.14 0.28 0.40 0.48 0.31 0.48 0.79 0.32 0.28 0.60

Mikkeli

11,300 A1 5.3 6.8 0.47 0.44 0.68

A2 4.7 4.5 0.41 0.48 0.65 0.38 0.76 1.14 0.35 0.30 0.65

E 5.0 (4.8) 0.4 0.05 0.01 0.01 0.01 0.06 0.18 0.24 0.06 0.05 0.11

Bs 5.2 (5.2) 1.4 0.16 1.37 0.97 1.85 0.61 1.25 1.86 0.27 0.07 0.34

a pH is 1:2.5 soil/water ratio; pH in parenthesis is 1:1 soil:water ratio.

D.L. Mokma et al. / Geoderma 120 (2004) 259–272266

similarity in mineralogy, bulk and fine fraction per-

mits comparison of the older pedons with the younger

pedons of the chronosequence.

Table 7

Semi-quantitative mineralogical composition of selected samples,

wt.% (+ indicates trace amount)

Time

(years BP)

Horizon Qu Kfs Plg Mica Chlorite Amph Hem

0 C 44 19 33 2 2 +

230 C 48 16 33 2 1

340 C 46 16 36 1 1 +

450 BC 46 22 28 2 1 1 +

560 C 47 17 32 2 1 1

670 C 44 19 34 1 1 1 +

900 BC 42 19 36 2 1 1 +

1800 BC 45 20 31 2 1 1

8300 C 45 20 32 1 1 1 +

9100 Bs 57 13 28 1 1 +

10,700 Bs3 47 18 32 2 1 +

11,300 BC2 45 11 36 6 1 1 +

Qu = quartz; Kfs =K-feldspar; Plg = plagioclase; Amph = amphi-

bole; Hem= hematite.

3.2. Diagnostic horizons

3.2.1. FAO–Unesco (FAO, 1990)

Albic horizons were present in all chronosequence

and older pedons. Criteria for the spodic B horizon are

chemical and do not include any morphological cri-

teria. Because the clay content of the Bs horizons was

zero, the seven chronosequence pedons met the

C + Alp H clay>0.2% criterion. If the Bs horizons

contained 1% clay, they would also meet the criterion.

The Alp + Fep HAld + Fed was greater than 0.5 in all

Bs horizons of the chronosequence. Even the 0C

horizon had Alp + Fep HAld + Fed of 0.5. The B hori-

zons of the older pedons met the chemical criteria.

Therefore, all pedons included in this study had

spodic B horizons according to the FAO–Unesco

system.

3.2.2. WRB (FAO, 1998)

All chronosequence and older pedons had albic

horizons. The Bs horizons of chronosequence pedons

Table 8

Mineralogical composition (++ + =most abundant, + = least abun-

dant) of the fine ( < 5 Am) fraction of selected samples

Time (years BP) 340 900 8300 9100 10,700 11,300

Horizon C BC C Bs Bs3 BC2

Quartz + + + + + + + + + + + + ++ +

Plagioclase + + + + + + + ++

K-feldspar + + + + + +

Amphibole + + +

Chlorite + + +

Illite + + +

Illite–vermiculite + + +

Allophane + ++ + + + + +

D.L. Mokma et al. / Geoderma 120 (2004) 259–272 267

and the B horizons of the older pedons met the color

criteria for a spodic horizon. Therefore, it took about

230 years to form a morphological spodic horizon in

Finland. This is similar to that reported by Tamm

(1950), but less time than that (>300 years) reported

by Jauhiainen (1973), Starr (1991) and Petaja-Ron-

kainen et al. (1992).

However, none of the Bs horizons had at least

0.50% Al + 1/2Fe in oxalate extracts. Only the 1800-

year-old pedon had two times more Alo + 1/2Feo in the

Bs horizon compared to the respective albic horizon.

Fulfillment of both the morphological and chemical

criteria are required for the spodic horizon in the

WRB system, thus none of the Bs horizons in the

2

1.5

1

0.5

0

-0.5

y = 0.0001x - 0.025

R2 = 0.9415

Al +

1/2

Fe (

%)

TIM

Fig. 2. Alo + 1/2Feo as a

chronosequence pedons were spodic horizons. The B

horizons of the four older pedons met all of the criteria

for a spodic horizon.

Simple linear regression was used to estimate the

length of time for Bhs and Bs horizons to meet the

various spodic horizon chemical criteria (n = 11).

When the B horizon had more than one subhorizon,

the upper subhorizon was used. The regression equa-

tion for Alo + 1/2Feo (Fig. 2) was:

Alo þ 1=2Feo ¼ 0:00015 time� 0:0279 ðr2 ¼ 0:91Þð1Þ

Using Eq. (1), the time at which 0.5% Al + 1/2Fe

would be reached was about 5280 years and at which

0.45%, which rounds up to 0.5%, would be reached

was about 4780 years. The regression for Alo + 1/2Feoof the B horizon was at least twice that of the E

horizon was:

ðAlo þ 1=2FeoÞBHðAlo þ 1=2FeoÞE¼ 0:0114 time� 9:085 ðr2 ¼ 0:69Þ ð2Þ

Using Eq. (2), the time at which (Alo + 1/2Feo)B H(Alo + 1/2Feo)E exceeded 2 was about 970 years. The

2

E

function of time.

y = 0.003x + 2.0532

R2 = 0.3803

OD

OE

(B)

/ O

DO

E(E

)

TIME

70

60

50

40

30

20

10

00 2000 4000 6000 8000 10000 12000

Fig. 3. ODOE of B horizon HODOE of E horizon as a function of time.

D.L. Mokma et al. / Geoderma 120 (2004) 259–272268

regression equation for ODOE of the B horizon to be

at least 0.25 was:

ODOE ¼ 0:000038 timeþ 0:0356 ðr2 ¼ 0:64Þð3Þ

Using Eq. (3), the time at which ODOE was at

least 0.25 was about 5640 years and about 5540 if one

uses 0.246. The following regression equation for

ODOE of the B horizon to be twice that of the E

horizon (Fig. 3) was obtained:

ODOEBHODOEE ¼ 0:003 timeþ 2:0532

ðr2 ¼ 0:38Þ ð4Þ

Using Eq. (4), the time at which the ODOE of the

B horizon was twice that of the E horizon was about 0

years or as soon as a B horizon formed. If only the

seven pedons of the chronosequence are used, the

following regression equation for ODOE of the B

horizon to be twice that of the E horizon was:

ODOEBHODOEE ¼ 0:0043 time� 0:9186

ðr2 ¼ 0:87Þ ð5Þ

Using Eq. (5), the time for which the ODOE was

twice that of the E horizon was about 680 years. These

equations and data suggest it took at least 4780 years

to form a spodic horizon (chemical criteria) in sandy

soils of Finland according to the WRB system (FAO,

1998).

3.2.3. Soil taxonomy (Soil Survey Staff, 1999)

The E horizons of all seven pedons of the chro-

nosequence met the color criteria of an albic horizon.

Thus, an albic horizon formed in only 230 years from

these acid parent materials in Finland. The E horizons

of 3000-year-old pedons in Michigan (Franzmeier and

Whiteside, 1963; Barrett and Schaetzl, 1992), but not

that of the 2250-year-old pedon (Franzmeier and

Whiteside, 1963), met the moist color criteria of an

albic horizon; dry colors were not given. An E horizon

that had formed in the 70-year-old pedon of a chro-

nosequence in Alaska (Alexander and Burt, 1996).

This E horizon met the color criteria for an albic

horizon.

All B horizons had a pH of less than 5.9 in water

(1:1) (Tables 5 and 6). Therefore, they met the pH

requirement for spodic materials (Soil Survey Staff,

1999). The pH of the C horizons, including that of the

chronosequence pedon 0, was 5.4 or less, thus it is not

surprising that the Bs horizons met this criterion.

In the chronosequence, only the Bs horizons of the

1800-year-old pedon met the organic C requirement

(>0.6%). The Bs horizons of all pedons met the color

criterion (hue of 7.5YR, value of 5 or less, and

chroma of 4 or less) for spodic materials. Of the four

y = 0.0002x + 0.1963

R2 = 0.7734

OR

GA

NIC

C (

%)

3.5

3

2.5

2

1.5

1

0.5

0

TIME

0 2000 4000 6000 8000 10000 12000

Fig. 4. Organic C as a function of time.

D.L. Mokma et al. / Geoderma 120 (2004) 259–272 269

pedons observed on the 230-year-old surface, one

lacked the colors for spodic materials. Therefore, it

took about 230 years to form a spodic horizon based

on morphology (color). This was similar to that found

by Alexander and Burt (1996) in Alaska, USA.

Cracked coatings were not observed in the Bs hori-

zons of the chronosequence pedons but were ob-

served in the B horizons of the older pedons.

Coatings were observed on sand grains in all Bs

horizons and materials similar to the coatings but free

of sand grains in all Bs horizons except that of the

230-year-old pedon. The older pedons had albic and

spodic horizons. The B horizons of 10,000-year-old

pedons in Michigan met the criteria for spodic

horizon (Franzmeier and Whiteside, 1963; Barrett

and Schaetzl, 1992), but not that of the 8000-year-

old pedon (Franzmeier and Whiteside, 1963) and the

4000-year-old pedon (Barrett and Schaetzl, 1992).

None of the B horizons in the chronosequence had

materials that were cemented together by organic C

and Al with or without Fe. The Toholampi and

Sotkamo pedons had ortstein at least 13 cm thick.

None of the B horizons in the chronosequence met the

Alo + 1/2Feo criterion nor the ODOE criterion. This is

not surprising as Mokma (1992) found that only about

half of the sandy Spodosols he studied in Michigan,

USA, met the Alo + 1/2Feo criterion and less than 10%

of them met the ODOE criterion. The Michigan

Spodosols were at least 6000 years old. The B

horizons of all older pedons in Finland had more than

0.50% Alo + 1/2Feo.

The following regression equation for organic C

versus time of surface (Fig. 4) was obtained:

organic C ¼ 0:0002 timeþ 0:1963 ðr2 ¼ 0:77Þð6Þ

Using Eq. (5), the time to reach 0.6% organic C

was about 2020 years and to reach 0.55% is about

1770 years. Based on data from this study and the

regression equations, it took about 1520 years to form

a spodic horizon that meets the color criteria (horizon

must meet the organic C criterion but not the Alo + 1/

2Feo criterion), or about 4780 years to form one that

did not meet the color criteria (horizon must meet the

Alo + 1/2Feo criterion) of Soil Taxonomy (Soil Survey

Staff, 1999). This fits in the lower part of the range,

‘‘more than 4000 years but less than 10,000 years,’’

for a spodic horizon to form in sandy beach deposits

with mixed deciduous and coniferous trees in Mich-

igan, USA (Barrett and Schaetzl, 1992). Using only

the color criteria, not including the organic C criteri-

on, a spodic horizon formed in about 230 years in

Finland (Fig. 4).

One would assume that rate of formation of mor-

phological properties of spodic horizons and that of

chemical properties would be similar. This assumption

is necessary if soil mappers are going to use morpho-

Table 9

Classification of the pedons according to the FAO, WRB and Soil

Taxonomy systems

Time

(years BP)

FAO–Unesco WRB Soil Taxonomy

230 Cambic

Podzol

Albic

Arenosol

Typic Cryopsamment

340 Cambic

Podzol

Albic

Arenosol

Typic Cryopsamment

450 Cambic

Podzol

Albic

Arenosol

Typic Cryopsamment

560 Cambic

Podzol

Albic

Arenosol

Typic Cryopsamment

670 Cambic

Podzol

Albic

Arenosol

Typic Cryopsamment

900 Cambic

Podzol

Albic

Arenosol

Typic Cryopsamment

1800 Cambic

Podzol

Albic

Arenosol

Entic Haplocryod

8300 Haplic

Podzol

Duric

Podzol

Typic Duricryod

9100 Haplic

Podzol

Haplic

Podzol

Typic Haplocryod

10,700 Haplic

Podzol

Duric

Podzol

Typic Duricryod

11,300 Cambic

Podzol

Umbric

Podzol

Typic Haplocryod

D.L. Mokma et al. / Geoderma 120 (2004) 259–272270

logical properties and field measured chemical prop-

erties to identify spodic horizons in the field. If

there is a question as to whether or not a pedon has

a spodic horizon, chemical analyses may be used to

answer that question. The FAO–Unesco system

(FAO, 1990) does not include morphological crite-

ria, therefore there is no apparent discrepancy. It is

apparent from this study that there is a major

discrepancy in both the WRB (FAO, 1998) and Soil

Taxonomy (Soil Survey Staff, 1999). Mokma (1992)

also found many sandy soils with Spodosol mor-

phology that did not meet the chemical criteria. All

pedons in this study met the color criteria for spodic

horizons of the two systems. Therefore, soil mappers

would have determined that these pedons had spodic

horizon and would have classified them as Podzol

or Spodosols. If soil mappers were to sample any of

the chronosequence pedons to verify their field

identification of spodic horizons, they would be

frustrated as no pedon would meet the WRB criteria

and only the 1800-year-old pedon would meet the

criteria of Soil Taxonomy. Chemical analyses would

only serve to frustrate soil mappers, not to increase

their confidence.

The time for soils in this study to reach the critical

value in the criteria varies greatly, 680–5540 years.

With this large range, it is not possible to make minor

adjustments to the critical values for the various

criteria to solve the discrepancies between morpho-

logical and chemical properties. A larger group of

soils is needed to solve this problem.

3.3. Classifications

All seven pedons in the chronosequence were

classified in the Cambic Podzol soil subunit (FAO,

1990) (Table 9). The Toholampi, Sotkamo and Jalas-

jarvi pedons were classified in the Haplic Podzol soil

subunit. The Mikkeli pedon was classified in the

Cambic Podzol soil subunit.

Using chemical data, the seven pedons in the

chronosequence were classified in the Albic Arenosol

soil unit (FAO, 1998). The Mikkeli pedon was clas-

sified in the Umbric Podzol soil unit, the Jalasjarvi

pedon in the Haplic Podzol soil unit, and the Toho-

lampi and Sotkamo pedons in the Duric Podzol soil

unit. Using only the color criteria, the chronosequence

pedons would classify in the Haplic Podzol soil unit.

The chronosequence pedons had ochric epipedons

and albic horizons, but only the 1800-year-old pedon

had a spodic horizon based on chemical criteria (Soil

Survey Staff, 1999; Mokma and Yli-Halla, 2000).

Therefore, the younger pedons were classified in the

Typic Cryopsamment subgroup. The 1800-year-old

pedon was classified in the Entic Haplocryod sub-

group. The Mikkeli and Jalasjarvi pedons were clas-

sified in the Typic Haplocryod subgroup. The

Toholampi and Sotkamo pedons were classified as

Typic Duricryod. Using only morphological proper-

ties, all chronosequence pedons would classify in the

Entic Haplocryod subgroup, not just the 1800-year-

old pedon.

4. Conclusions

Translocation of C, Al and Fe was visually

evident in the 230-year-old pedon. Chemical evi-

dence was clear in the 900-year-old pedon. Albic

horizons were present in all uncultivated pedons.

Owing to the absence of clay in the Bs horizons

D.L. Mokma et al. / Geoderma 120 (2004) 259–272 271

and the high Alp + Fep HAld + Fed ratio of the C

horizon of pedon 0, all pedons of the chronose-

quence ( < 1800 years) had spodic B horizons

according to the FAO–Unesco system. Therefore,

all pedons were classified as Podzols. According to

the WRB system, none of the pedons of the chro-

nosequence had spodic horizons and therefore were

classified as Arenosols. The older pedons (8300–

11,300 years) all had spodic horizons and were

classified as Podzols. It took about 4780 years to

form a spodic horizon in a sandy soil in Finland.

According to Soil Taxonomy, it took about 1520

years to form spodic horizons that met the color

criteria and about 4780 years if the B horizons did

not meet the color criteria. Pedons less than 1800

years old were classified as Typic Cryopsamments.

Pedons at least 1800 years old were classified as

Cryods; Haplocryods if the B horizon was not

cemented and Duricryods if it was cemented. Addi-

tional revision of the chemical criteria and subse-

quent testing is required before satisfactory color and

chemical criteria for spodic horizons will be found.

The mineralogical composition of the selected sam-

ples was uniform and similar to that of podzols in

Fennocandia. Quartz, plagioclase and K-feldspar

were the dominant minerals in the bulk samples.

The fine fraction had minor amounts of illite, chlo-

rite, and mixed-layered illite–vermiculite.

Acknowledgements

The authors thank Professor Matti Saarnisto,

Geological Survey of Finland, for estimating the ages

of the Jalasjarvi, Mikkeli, Sotkamo and Toholampi

pedons.

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