Directory UMM :Data Elmu:jurnal:P:Postharvest Biology and Technology:Vol17.Issue3.Nov1999:

Forest Ecology and Management 126 (2000) 269±279

Effects of ash fertilization and prescribed burning on macronutrient,
heavy metal, sulphur and 137Cs concentrations in lingonberries
(Vaccinium vitis-idaea)
Teuvo Levula1,a, Anna Saarsalmib,*, Aino Rantavaara2,c
a

Finnish Forest Research Institute, Parkano Research Station, Kaironiementie 54, FIN-39700, Parkano, Finland
b
Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FIN-01301, Vantaa, Finland
c
Radiation and Nuclear Safety Authority (STUK), P.O. Box 14, FIN-00881, Helsinki, Finland
Received 2 October 1998; received in revised form 9 February 1999; accepted 16 February 1999

Abstract
The effects of ash fertilization and prescribed burning on the P, K, Ca, Mg, Mn, S, Fe, Al, Cu, Zn, Cd, Cr, Ni and 137Cs
concentrations in lingonberry (Vaccinium vitis-idaea L.) berries were investigated in a 100-year-old Scots pine (Pinus
sylvestris L.) stand growing on a dry site in central Finland. The treatments were control, prescribed burning and three ashfertilizer doses of 1000, 2500 and 5000 kg haÿ1. The size of the plots was 30  30 m, and there were four replications per
treatment. Lingonberries were collected two (1991) and seven (1996) growing seasons after the treatments. Ash fertilization
had no effect on the heavy metal concentrations in the berries. Potassium was the only macronutrient whose concentration in

the berries signi®cantly increased after ash fertilization (5000 kg haÿ1). Prescribed burning increased the berry Cd
concentrations, which, however, remained low even after prescribed burning. The berry 137Cs concentrations decreased as a
result of ash fertilization and prescribed burning. The reduction in 137Cs concentrations caused by ash fertilization may be an
important ®nding especially for areas where the picking and consumption of berries has to be restricted as a result of
radioactive fallout. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Radiocaesium; Potassium; Forest soil

1. Introduction
Nutrient cycling in forests in the cool, humid conditions of the boreal coniferous forest zone is slow, and
acidic humus material accumulates on the soil surface.
*Corresponding author. Tel.: +358-9-857051; fax: +358-98572575.
E-mail address: anna.saarsalmi@metla.fi (A. Saarsalmi).
1
Tel. +358-3-44351, e-mail: teuvo.levula@metla.fi
2
Tel.: +358-9-759881; e-mail: aino.rantavaara@stuk.fi

In addition to the slow, natural acidi®cation that occurs
during the development of such soils, they are also
sensitive to external inputs of acidifying compounds.

For this reason, the atmospheric deposition of acidifying compounds is expected to gradually increase
the leaching of base cations and soil acidi®cation.
Attempts have been made to slow down the anthropogenic acidi®cation of forest soils by silvicultural
means, e.g. by prescribed burning and ash fertilization.

0378-1127/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 8 - 1 1 2 7 ( 9 9 ) 0 0 1 1 0 - 3

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T. Levula et al. / Forest Ecology and Management 126 (2000) 269±279

In prescribed burning, logging residues, ground
vegetation and part of the organic layer are burnt
and the surface of the soil heats up (Viro, 1969).
The maximum temperature of the soil surface during
prescribed burning can momentarily be as high as
8008C (Vasander and Lindholm, 1985). Apart from the
extremely high temperatures reached during burning,
prescribed burning has a bene®cial effect on the longer

term temperature conditions in the soil of the boreal
forest. In addition to temperature, prescribed burning
also affects the nutrient status of the soil. The mineral
nutrients bound in the organic matter are converted
into oxides during burning, many of which have an
alkaline reaction. The hydroxyl ions formed after
dissolution of these oxides have an immediate reducing effect on soil acidity, and the released base
cations (Ca, Mg, K, Na) can increase the buffering
capacity of the soil for decades (Viro, 1969; MaÈlkoÈnen
and Levula, 1996).
Apart from N and S, wood ash contains mineral
nutrients in almost the same proportions as in the stand
biomass. Ash fertilization does not have the heating
effect of prescribed burning, but in other respects the
effects of ash fertilization are similar to those of
prescribed burning. Wood ash has increased stand
growth on N-rich peatlands (Silfverberg and Huikari,
1985; Silfverberg and Hotanen, 1989), but not on
mineral soils (MaÈlkoÈnen and Levula, 1996; SikstroÈm,
1992). In the case of mineral soil sites, however, the

bene®ts of using ash fertilization are associated with
its role as an ameliorative agent and stimulator of the
biological activity of the soil, rather than as a source of
nutrients.
In addition to base cations, wood ash also contains
heavy metals (e.g. Cu, Zn, Mn, Pb, Cd, Cr, Hg, Ni).
Some of these metals (Mn, Cu, Zn) are essential trace
elements for plants. It has been suspected that these
heavy metals may be harmful for soil microbial
activity and nutrient cycling, and represent a health
hazard for people collecting edible products from the
forest such as berries and fungi. The most harmful
heavy metals are Cd, Hg and Pb, of which Cd is the
only metal of any practical importance. However,
when moderate doses are applied, the normal range
of Cd concentrations in wood ash has no detrimental
effects on organic matter decomposition or on the rate
of nutrient mineralization (Fritze et al., 1994). In
laboratory experiments, the respiration of soil, treated

with ash fertilizer,was reduced only on a Cd addition
of 0.4 mg kgÿ1 of soil, as compared to that of the
controls (Fritze et al., 1995).
In nature, Cd concentrations are normally very low.
However, owing to its severe toxicity and relatively
high mobility and enrichment, it is considered to be
perhaps the most problematic of the heavy metals.
Normally the Cd concentrations in wood ash vary
from 4 to 20 mg kgÿ1 (Anonymous, 1993). In
Finland, the application to agricultural soil of ash
which contains >3 mg kgÿ1 Cd is prohibited (Anonymous, 1994), but this restriction does not hold for
forest soils.
Wood ash fertilization results in lush development
of the ground vegetation on N-rich, drained peatlands
(Silfverberg and Huikari, 1985; Silfverberg and
Hotanen, 1989), while on infertile drained peatlands
it has only slight effects on the ground vegetation,
apart from a reduction in the coverage of Sphagnum
spp. (Vasander et al., 1988). No signi®cant changes in
the ground vegetation have been observed on mineral

soils following ash fertilization (Gyllin and Kruuse,
1996; RuÈhling, 1996).
Following the Chernobyl nuclear accident (1986),
attention started to be paid in Finland to the levels of
radioactive Cs, primarily 137Cs, in forest ecosystems
(Dahlgaard et al., 1994). Caesium, which occurs
naturally in the bedrock, is not known to have any
signi®cance as a nutrient, but it may, to a small extent,
replace K in the metabolism of animals and plants, and
thus be transferred from the soil to living organisms
(Koljonen et al., 1992). The radioactive Cs which is
formed in nuclear reactions behaves, when it enters the
nutrient cycle, in the same way as the natural isotope
of Cs and expose, via the food chain, humans to
radiation.
The radiocaesium concentrations of forest berries
and fungi in Finland have been monitored regularly
since 1986 (Rantavaara, 1990). Plants take up Cs from
forest soil much more ef®ciently than from agricultural land. This has been demonstrated by the Finnish
studies on 137Cs concentrations in moose (Alces alces

L) meat carried out already during the nuclear test
period (Rantavaara, 1982). Moose, while eating natural plants, ingest considerably greater amounts of
radiocaesium than domestic animals, and this is
evident as differences in the 137Cs concentrations of
the meat.

T. Levula et al. / Forest Ecology and Management 126 (2000) 269±279

Fertilization has been found to reduce 137Cs concentrations in many crop plants (Fredriksson, 1963).
In Finland, the effects of fertilization on the radiocaesium transfer in forests has been emphasized in
radioecological research (Raitio and Rantavaara,
1994).
The aim of this study is to determine the effects of
ash fertilization and prescribed burning on the macronutrient, heavy metal, sulphur and 137Cs concentrations in the berries of lingonberry (Vaccinium vitisidaea L.) growing in a Scots pine stand on a dry site.

2. Material and methods
A ®eld experiment was established in a 100-yearold Scots pine (Pinus sylvestris L.) stand at Kuorevesi
(628 20 N, 248 500 E, 130 m asl), central Finland, in the
spring of 1990. At the time of establishment the stem
number of the stand was 300 stems haÿ1, mean height

21 m, and the volume including bark 180 m3 haÿ1.
The site was of the dry site type, the soil texture sorted
sand and the soil type iron podsol. The thickness of the
humus layer was 3 cm. The organic matter content of
the humus layer was 75%.
The experiment was laid out in a random block
design, with ®ve treatments in four blocks. The treatments within each block were performed on 30  30
plots with a control, three levels of ash fertilization
(1000, 2500 and 5000 kg haÿ1) and a prescribed
burning treatment. The ash used was derived from
the ignited bark (850±10008C for ca. 30 min)
mechanically stripped from the stems of Scots pine
and Norway spruce (Picea abies (L.) Karsten) during
processing for saw timber. According to current
knowledge, 5000 kg haÿ1 is a relatively high dose
of wood ash. The composition of the bark ash used
in the experiment was, on a dry weight basis, as
follows: P, 13; K, 36; Ca, 280; Mg, 21; and Mn,
16 g kgÿ1; and Fe, 4300; Al, 9400; Cu, 90; Zn,
630; Cd, 1.4; and Pb, 19 mg kgÿ1. The approximate

concentration of 137Cs in ash, ranging from 5000 to
10 000 Bq kgÿ1, was derived from the data on ash
origin, namely the regional 137Cs deposited in the
delivery area of timber (Arvela et al., 1990) and from
the data on radioactivity of Finnish timber, and particularly bark of pine and spruce (Rantavaara, 1996).
The original surface density of the 137Cs activity at the

271

site was ca. 50 000 Bq mÿ2 (1 October, 1991). The ash
was spread on the plots on 21±22 May, 1990. The
prescribed burning treatment was prepared as follows.
Pine and spruce cutting residues (ca. 19 t haÿ1, dry
weight) from a neighbouring cutting area were spread
on the plots to carry a ®re and ensure burning of the
ground vegetation. With the cutting residues, roughly
1000 Bq 137Cs mÿ2 was added to the plots. Prescribed
burning was performed on 14 May, 1990. All the trees
on the experimental area were left standing.
Samples were taken from the humus layer in 1990,

one growing season after the treatments. Fifteen subsamples were taken systematically from each plot
using a cylinder (d ˆ 5.8 cm). The thickness of the
humus layer was measured at the same time. The
subsamples were combined to give one composite
sample per plot. The samples were air-dried and
milled to pass through a 2-mm sieve. Exchangeable
and extractable nutrients (P, K, Ca, Mn and Zn) were
determined by extraction with 1 M ammonium acetate
(pH 4.65) and analyzed by inductively coupled plasma
atomic emission spectrometry (ICP/AES), total N on a
CHN analyser (LECO), and pH from a water suspension (Halonen et al., 1983). The Al concentration was
determined by titration following extraction with 1 M
KCl.
Lingonberry samples were collected from each plot
in autumn 1991 and 1996. The berries were collected
when ripe using protective gloves. In 1991 there were
no berries on the burnt plots. The dried berries (608C,
5 days) were milled in an ultracentrifuge mill. The
element (P, K, Ca, Mg, Mn, S, Fe, Al, Cu, Zn, Cr, Cd,
Ni) concentrations were determined by wet digestion

(HNO3 ‡ H2O2) (Huang and Schulte, 1985). The Cd
concentration was determined by ¯ameless AAS, and
the other elements by ICP/AES.
The 137Cs concentration was determined from the
lingonberry samples using a low-background semiconductor spectrometer calibrated for the analysis of
environmental radioactivity. A standard sample geometry was used. The gamma spectra were analyzed
using the GAMMA-83 computer code developed at
STUK. The method has been tested in several international and Nordic comparison programmes for
gamma spectrometric radiocaesium determinations
(Rantavaara et al., 1994). For a realistic comparison
of the concentration of 137Cs in the two samplings
(1991 and 1996), the effect of radioactive decay on the

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T. Levula et al. / Forest Ecology and Management 126 (2000) 269±279

concentrations was eliminated by correcting all the
137
Cs concentrations to correspond to the activity in
October 1991.
The coverage of the ground vegetation was studied
in August 1995. Eight 1-m2 quadrats were systematically marked out on each plot, and the coverage of
®eld and bottom layer species estimated.

The effects of the treatments on the element
concentrations in the humus layer and berries and
on the coverage of species were tested using
analysis of variance. Tukey's paired t-test was used
to test the statistical signi®cance of differences
between the treatments (BMDP statistical software,
1985).

Fig. 1. Total N concentration (organic matter basis) and extractable P and exchangeable K, Ca, Mg, Mn, Zn and Al concentrations (dry matter
basis) and pH in the humus layer one growing season after prescribed burning or wood-ash fertilization. Mean values with the same letter do
not differ significantly from each other according to the F-test ( p < 0.05). Standard deviation is marked on the columns by bars.

T. Levula et al. / Forest Ecology and Management 126 (2000) 269±279

273

3. Results
3.1. Acidity and nutrient content of the humus layer
The total N, extractable P and exchangeable Mg
concentrations on the control plots were slightly
lower, the K concentrations about the same, and the
Ca concentrations higher than the mean values for this
site type in Southern Finland (Fig. 1) (cf. Tamminen,
1991). Ash fertilization and burning decreased the
acidity of the humus layer and increased the base
cation concentrations. The Ca and Mg concentrations
were, after one growing season, somewhat higher on
the burned plots than on the plots given 1000 kg
ash haÿ1, but clearly lower than after the addition
of 5000 kg ash haÿ1. After the largest ash dose, the
exchangeable nutrient concentrations increased to a
level higher than the average for herb-rich sites in
southern Finland (cf. Tamminen, 1991). The
exchangeable Al concentration in the humus layer
decreased along with the increase in pH. There was
no exchangeable Al at all on the plots that were burnt
or given 5000 kg ash haÿ1.
3.2. Element composition of the lingonberries
Ash fertilization (5000 kg haÿ1) increased the K
concentrations of the lingonberries compared to the
controls in both the sampling years (Table 1). In
contrast, the Mn concentrations after seven growing
seasons were signi®cantly lower on both, the burnt and
ash-fertilized plots than on the controls. Burning
increased the Cd and Al concentrations in the berries.
The change in the Al concentration was statistically
only indicative ( p < 0.1). Neither burning nor
ash-fertilization had any signi®cant effect on the
concentrations of other macronutrients. The Ca concentration was higher, but the Al concentration was
lower, in the berries in all the treatments in 1996 as
compared to 1991. There were no statistical differences in other element concentrations between the
sampling years.
3.3. Cs concentrations of lingonberries
Prescribed burning and ash-fertilization reduced
the 137Cs concentrations in the berries (Fig. 2),
which were higher after seven growing seasons on

Fig. 2. 137Cs concentration (dry matter basis) in the lingonberries
in becquerels (Bq kgÿ1) two (in 1991) and seven (1996) growing
seasons after prescribed burning or wood ash-fertilization. Mean
values with the same letter do not differ significantly from each
other according to the F-test (p < 0.5). Standard deviation is
marked on the columns by bars.

the controls and ash-fertilized (1000 kg haÿ1) plots
than after two growing seasons. There were no
differences in the berry 137Cs concentrations in the
other ash-fertilizer treatments between the sampling
years. Seven growing seasons after the treatments, the
137
Cs concentrations were signi®cantly lower on the
burnt and ash-fertilized (2500 and 5000 kg haÿ1) plots
than on the control or ash-fertilized (1000 kg haÿ1)
plots.
The 137Cs concentrations in the berries clearly
correlated inversely with the pH of the humus layer
and the exchangeable macronutrient concentrations
(Fig. 3). The 137Cs concentration of the berries was
best explained by the exchangeable Mg concentration
in the humus layer (R2 ˆ 0.88).
3.4. Ground vegetation
The dominant ®eld layer species on the control and
ash-fertilized plots were lingonberry (Vaccinium vitisidaea) and crowberry (Empetrum nigrum), and the
bottom layer species red-stemmed feather moss
(Pleurozium schreberi) and wavy fork moss (Dicranum polysetum) (Table 2). The dominant species on
the burnt plots were lingonberry and purple-fruiting
heath moss (Ceratodon purpureus). Crowberry, red-

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T. Levula et al. / Forest Ecology and Management 126 (2000) 269±279

Table 1
Element concentrations in the lingonberries two (in 1991) and seven (in 1996) growing seasons after prescribed burning or wood-ash
fertilization.
Nutrient

Year

Control

Burnede

Ashe (kg haÿ1)
1000

ÿ1

d

F-value
2500

5000

P (g kg )

1991
1996

1.1
1.2

Ð
1.1

1.2
1.1

1.1
1.1

1.2
1.2

K (g kgÿ1)

1991
1996

6.0a
6.3a

Ðd
6.4ab

6.8ab
6.1a

6.6a
6.4ab

7.6b
7.2b

Ca (g kgÿ1)

1991
1996

1.3
1.6

Ðd
1.3

1.2
1.5

1.3
1.5

1.3
1.6

0.3
2.0

Mg (g kgÿ1)

1991
1996

0.5
0.6

Ðd
0.6

0.6
0.6

0.6
0.6

0.6
0.7

1.4
1.2

Mn (mg kgÿ1)

1991
1996

253
274b

Ðd
261a

241
249a

254
204a

261
178a

0.2
3.7*a

S (mg kgÿ1)

1991
1996

747
781

Ðd
711

758
735

720
714

755
752

1.0
0.9

Fe (mg kgÿ1)

1991
1996

15
14

Ðd
14

15
14

13
13

15
14

1.1
0.7

Al (mg kgÿ1)

1991
1996

32
24

Ðd
29

30
24

27
19

30
18

1.1
2.6

Cu (mg kgÿ1)

1991
1996

Zn (mg kgÿ1)

1991
1996

Cd (mg kgÿ1)

1991
1996

0.004
0.003a

Ðd
0.009b

0.004
0.003a

0.003
0.003a

0.005
0.003a

1.1
5.1**b

Cr (mg kgÿ1)

1991
1996

0.2
0.2

Ðd
0.2

0.2
0.2

0.2
0.2

0.2
0.2

0.2
0.7

Ni (mg kgÿ1)

1991
1996

0.3
0.4

Ðd
0.3

0.3
0.3

0.3
0.3

0.3
0.3

1.4
2.9

5.7
5.8
11
11

Ðd
5.2
Ðd
11

5.9
5.9
11
11

5.0
5.1
11
11

5.3
5.4
11
11

3.1
1.2
11.2***c
4.3*a

3.3
1.5
0.6
1.0

a

*p < 0.05.
**p < 0.01.
c
***p < 0.001.
d
No value because lingonberries could not yet be found on burned plots in 1991.
e
Means with the same letter do not differ significantly from each other ( p < 0.05).
b

stemmed feather moss or wavy fork moss had not
reappeared on the burnt plots even after six growing
seasons. The coverage of lingonberry on both, the
burnt and control plots was 17%. Ash fertilization

reduced the coverage of lingonberry to some extent.
On the plot given the largest dose of ash
(5000 kg haÿ1) the coverage of lingonberry was only
8%.

T. Levula et al. / Forest Ecology and Management 126 (2000) 269±279

Fig. 3. Dependence of

275

137

Cs concentration in the lingonberries on nutrient concentrations and pH(water) in the humus layer in 1991.

4. Discussion
Changes in soil acidity affect the chemical and
biological properties of the soil, thus in¯uencing the
uptake of nutrients by plants. The increase in the pH of
the substrate caused by ash fertilization may have a
detrimental effect on the functioning of the mycorrhizas of berry species (Moberg and TidstroÈm, 1985).
According to RuÈhling (1996), the fungi which form
mycorrhizal associations decrease after ash fertilization, while fungi that decompose litter increase.
According to Swedish studies, a reduction in lingonberry stands was not observed on mineral soil sites 2±9

years after ash fertilization (Gyllin and Kruuse, 1996).
In this study, however, the dwarf shrub stand was
slightly reduced by the application of 5000 kg
ash haÿ1.
Changes in the ground vegetation after prescribed
burning are long-lasting. According to Viro (1969), 10
years after burning the coverage of mosses was about
one-third and that of dwarf shrubs about half that on
unburnt plots. On the burnt plots in this study crowberry plants, red-stemmed feather moss or wavy fork
moss had not reappeared at all after six growing
seasons, but the coverage of lingonberry was already
the same as on the control plots.

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T. Levula et al. / Forest Ecology and Management 126 (2000) 269±279

Table 2
Coverage of plant species six growing seasons after prescribed burning or wood ash fertilization
Plant species

Coverage (%)
controla

Lichens
Cladonia rangiferina (L.) Weber ex F. H. Wigg.
Cladonia arbuscula (Wallr.) Flot.

burneda

asha (kg haÿ1)
1000

2500

5000

7
1

0
0

5
0

3
1

1
0

Mosses
Ceratodon purpureus (Hedw.) Brid.
Dicranum polysetum Sw.
Hylocomium splendens (Hedw.)
Pleurozium schreberi (Brid.) Mitt.
Pohlia nutans (Hedw.) Lindb.
Polytrichum juniperum Hedw.

0
22a
2
50a
0
0

18
0b
0
0b
5
5

0
25a
3
52a
0
0

0
19a
5
57a
0
0

0
11a
2
68a
0
0

Vascular species
Calluna vulgaris (L.)
Empetrum nigrum L.
Epilobium angustifolium L.
Vaccinium vitis-idaea L.

2
13a
0
17

2
0b
1
16

3
15a
0
14

2
11a
0
12

3
9a
0
8

a

Mean values with the same letter do not differ significantly from each other according to the F-test (p < 0.05).

The nutrient concentrations of the lingonberries in
this study were of the same level as those reported in
earlier studies (Silfverberg and Issakainen, 1991;
Laine et al., 1993; RuÈhling, 1996). The Cd concentrations in this study were lower than those reported by
Silfverberg and Issakainen (1991), but of the same
level as those obtained by RuÈhling (1996). The natural
Cd concentrations in berries are