Full text of DOI:10.1093/forestry/73.4.393

Long-term effects of lim e
1
5
application on N availability to
Sitka spruce seedlings growing in
pots containing peat soils
M. KAKEI AND P.E. CLIFFORD2
1
1
Varbergagatan 10, 703 51 Örebro, Sweden
School of Biology and Biochemistry, The Queen’s University of Belfast, Medical Biology Centre,
2
9
7 Lisburn Road, Belfast BT9 7BL, Northern Ireland
Summary
The long-term effects of liming a peat soil on nitrogen availability to 3-year-old Picea sitchensis
seedlings were assessed in greenhouse experiments. Seedlings were planted in pots containing either
unlimed or limed peat soils that had been limed 28 years earlier. The plants were harvested in
October 1993, April 1994 and July 1994 with these dates representing 100, 160 and 263 days after
–
planting respectively. Concentration of extractable NO3 in the limed peat was higher than in the
unlimed peat. Liming also resulted in increases in extractable organic N and total extractable N in
1
5
the peat. On all harvesting occasions, percentage N utilization and total N were reduced in plants
grown on the limed peat. Decreased concentrations of N in the fine-root fractions were apparent for
plants grown on the limed peat at the October and July harvests only. During the growing season,
the above-ground parts of the plant were the dominant sinks for nitrogen. The needles and fine roots
1
5
were the major fractions for the utilization of N particularly in April and July. The only effect of a
limed peat on dry weight of plant fractions was a decrease in fine-root dry weight when plants were
examined in October 1993. On all harvesting occasions, populations of mycorrhizae were decreased
and roots were blackened for plants grown in the limed peat soil.
Introduction
Ca in the soil (Kamprath and Foy, 1985). Appli-
cation of lime also changes the properties of soils
The high acidity of deep, oligotrophic blanket which, in turn, has effects on the availability of
peat is an undesirable characteristic as a medium soil nutrients and nutrient uptake by plants
for growing trees (Dickson, 1972). To restrict the growing on such soils (Marschner and Wilczyn-
negative effect of low pH on growth processes, ski, 1991).
liming is a common practice for acid forest soils.
Liming increases the breakdown rate of the
Limestone is often used to neutralize acidity, to soil organic matter and this is associated
reduce exchangeable Al and to increase available with increases in the activities and numbers of
©
Institute of Chartered Foresters, 2000
Forestry, Vol. 73, No. 4, 2000

3
94
FO R EST RY
actinomycetes, bacteria, earthworms and fungal details of all treatments applied to the experi-
fruiting bodies (Adams et al., 1978; Carey et al., mental site have been recorded by the Depart-
1
981). Immobilization, either of nitrogen in the ment of Agriculture for Northern Ireland.
forest floor or of added nitrogen, as a conse- Data related to the forest stand have been
quence of increased microbial activity has been recorded by Kakei (1995). Concentration of
reported (Adams and Cornforth, 1973; Carey et phosphorus in needles of trees growing in the
al., 1981). Lime application, therefore, leads to a limed plots was high compared with the unlimed
–1
decrease in quantity of mineral nitrogen and to a plots (L = 1.45 and L = 2.05 mg g DW respec-
0
1
greater proportion of mineral nitrogen recovered tively). Concentration of N in needles of trees
in peat soils as nitrate (Farrell, 1985). On the growing in the limed and unlimed plots was 9.75
–1
other hand, mycorrhizal associations may and 11.15 mg g DW respectively. There were no
increase the ability of higher plants to compete differences in tree growth between the limed and
for nitrogen (Dickson, 1989).
unlimed plots, while fine-root growth was
The storage of nitrogen and its internal supply increased by liming. The peat moisture in the
is important for sustainable growth of evergreen limed and unlimed plots was 81.5 and 85.3 per
trees (Miller et al., 1979; Millard and Proe, cent, respectively, when the peat was removed
1
992). The main objectives of this study were to from the plots. The peat pH was 5.38 and 3.55
investigate the long-term effects of liming on the in the limed and unlimed plots, respectively, when
1
5
15
N dynamics of peat soils and N utilization by the peat was removed from the plots for use in
3
-year-old Picea sitchensis seedlings growing in experiments.
these peat soils. Data were also obtained for
A sampling core was used to take peat samples.
extractable mineral and organic nitrogen levels in After removing the litter layer, plastic pots (1.75
the peat soils as well as total and percentage nitro- l in volume) were filled with fresh peat contain-
gen, dry weight of plant fractions, characteristics ing about 140 g dry matter in each pot. To deter-
of fine roots and populations of mycorrhizae for mine calcium content of limed and unlimed peats,
the experimental plants.
10 random fresh peat samples (each sample was
kg) from each type were dried (60ºC for 72 h)
1
and weighed. The dried samples were separately
ground (Cyclotec, 1093 sample mill, mesh size =
Materials and methods
2
mm) and then digested in 70 per cent HNO3.
Two types of peat, limed and unlimed, were col- After digestion, samples were analysed for
lected on 8 July 1993 from the top 15 cm below concentration of calcium using an inductively
the litter layer from two plots under 30-year-old coupled plasma–optical emission spectrometer
P. sitchensis trees growing on deep unflushed (Perkin-Elmer) (ICP-OES). The mean concentra-
blanket peat in Beaghs forest in Northern Ireland. tions of calcium in the limed and unlimed peats
–1
–1
One of the plots had been limed (22.5 t ha ) in were 9.8 and 1.2 mg g DW respectively.
965 and the second plot was unlimed. Freshly dug, 3-year-old P. sitchensis seedlings
These two plots are part of a designed experi- (2 + 1) of Queen Charlotte Islands origin were
1
ment with the following history. Each plot transferred into pots, one plant per pot, on 9 July
measures 30 ꢀ 15 m. In September 1965, ground 1993 for the October experiment and on 29
–
1
limestone at 0 (L ), and 22.5 t ha (L ) and October 1993 for both the April and July experi-
0
1
1
–
coarse rock phosphate at 750 kg ha were ments. The average dry weight of a seedling was
applied 6 months prior to planting. In spring 10.11 g. In the nursery, the seedlings had received
966, seedlings of Sitka spruce were planted. In three fertilizer applications, each of 42.5 kg ha–1
970, muriate of potash (KCl) was applied at 225 of N, P O and K O. Following potting, plants
kg ha to the plots. Coarse rock phosphate was were placed outdoors at the Department of Agri-
reapplied at 750 kg ha in 1974. In spring 1976, culture, Newforge Lane, Belfast. The pH in each
KCl and urea were applied at 200 kg ha and pot was measured by direct insertion of the elec-
00 kg ha , respectively, to the plots. Urea at the trode of a pH-meter (Whatman PHA 400) at the
standard rate of 350 kg ha was reapplied to the rooting zone just prior to each harvest. Mean pH
plots prior to growth in 1985 and 1993. Full was 3.48, 3.58 and 3.42 in the unlimed peat and
1
1
2
5
2
–1
–1
–1
–1
5
–1

EFFEC T S O F LIM E O N SIT KA SPR UC E SEED LIN G S
395
6
.52, 5.18 and 5.45 in the limed peat at the centrifuged for 5 min and filtered. Concentrations
October, April and July harvests respectively. One of extractable NH4+-N and NO -N were
–
3
1
5
week before supplying N, the plants were measured using
a Flow Injection Analyser
moved into a glasshouse (15–22°C).
(Tecator Ltd). Extractable mineral N was the sum
of extractable NH4+-N and NO -N. Extractable
–
Each pot received 139 mg of N as (NH ) SO
4
2
4
3
1
5
labelled with N at 5 atom per cent excess dis- organic N was calculated as total extractable N
solved in 50 ml of distilled water. For the October minus extractable mineral N.
experiment, the plants were supplied with
labelled N on 11 October 1993 and harvested on under a stereo microscope (ꢀ60) to determine the
5 October 1993. For the April experiment, effects of lime on them.
Fine roots and mycorrhizae were examined
2
labelled N was added on 7 March 1994 and
For each occasion, the effects of lime appli-
plants were harvested on 5 April 1994, while for cation on extractable NH4+-N, NO -N and
–
3
the July experiment, labelled N was added on 22 organic N and total extractable N in the peat
June 1994 and plants were harvested on 22 July were tested by analysis of variance. Significant
1
994. The plants were watered with distilled differences between means were established using
water twice a week while in the glasshouse. There t-tests. For each plant fraction, effects of lime on
1
5
were five replicates for the October experiment percentage N utilization by plant fractions and
and 10 replicates for the April and July experi- peat soils, and on the total N contents and per-
ments.
centage of N in plant fractions, were tested in the
At harvest, plant parts were dissected into same manner.
leader (including its needles), needle (needles of
whole plant except needles of leader), shoot (total
branches without needles), stem (whole main
stem), coarse root (> 5 mm in diameter), medium
Results
root (2–5 mm in diameter) and fine root (< 2 mm Peat samples were analysed to study the effects of
in diameter). Plant fractions and peat soils were lime application on concentrations of extractable
oven-dried (60°C for 72 h), weighed and ground NH4+-N and NO -N for the April and July
–
3
with a micro-mill (Glen Creston, DCFH 48 type, experiments only (Table 1). In April, the concen-
mesh size = 1 mm).
tration of extractable NH4+-N in the unlimed
Concentrations of 15N in plant fractions and peat was double that in the limed peat, while in
peat samples were determined using a Carlo Erba July there were no significant differences in peat
NA 1500 Elemental analyser, linked to a VG concentration of extractable NH4+-N between the
Micromass 622 Stable Isotope Mass Spectrome- limed and unlimed treatments. Concentration of
–
ter. A Roboprep CN Elemental Analyser was used extractable NO -N in the limed peat was 135
3
to determine percentage nitrogen in the plant and 23 times that in the unlimed peat in April and
samples.
July respectively.
Percentage 15N utilization by plant fractions
Extractable mineral N (mg g ) in the unlimed
peat was 33 per cent greater than that in the limed
peat in April (Table 1). In contrast, extractable
–1
and peat soils was calculated as:
Atom per cent excess in sample
–1
organic N (mg g ) in the limed peat was 25 and
—
——————————————
Atom per cent excess in fertilizer
2
3 per cent greater than that in the unlimed peat
in April and July respectively. Total extractable N
Yield of N (mg/pot)
ꢀ
———————————— ꢀ 100
Rate of N applied (139 mg)
–1
(
mg g ) in the limed peat was 22 and 23 per cent
greater than that in the unlimed peat in April and
The atom per cent excess in the sample and fer- July respectively (Table 1).
1
5
tilizer was corrected for the atom per cent N in
the sample and fertilizer using 0.367 atom per
cent N as natural abundance.
In the October experiment, the percentages of
N utilization by all plant fractions, with the
exception of the medium-root fraction, were
1
5
1
5
A 40 g subsample of the peat soil from each pot greater for plants on the unlimed peat compared
was treated with 200 ml of 2 mol/l KCl to extract with plants on the limed peat (Table 2). Lime
+
–
NH4 -N and NO -N. The extracts were application decreased total N in the leader,
3

3
96
FO R EST RY
Table 1: Long-term effects of lime application on concentrations of extractable NH4+-N, NO3–-N, mineral N
–1
and organic N and total extractable N (mg g DW) in peat soils used for the April and July experiments
Month/
lime level
Extractable
NH4 -N
Extractable
NO3–-N
Extractable
mineral N
Extractable
organic N
Total
extractable N
+
April
L0
1.07
0.002
1.072
14.23
15.30
L1
0.54
0.269
0.809
17.78
18.59
SE
0.143**
0.073***
0.095**
0.251***
0.272***
July
L0
0.13
0.001
0.131
14.15
14.28
L1
0.10
0.023
0.123
17.38
17.50
SE
0.059 NS
0.009***
0.027 NS
0.348***
0.157***
L = unlimed peat; L = limed peat; n = 10.
0
1
NS, not significant; **significant at P < 0.01; ***significant at P < 0.001.
Table 2: Effects of lime application on percentage 15N utilization by plant fractions and peat soils and on total
and percentage N in plant fractions in October 1993
%
Utilization 15N
————————————— —————————————– ————————————
Total N (mg)
N%
—
Plant fraction
L0
L1
SE
L0
L1
SE
L0
L1
SE
Leader
Needles
Shoots
Stem
0.34
2.97
1.48
1.16
1.04
0.48
5.68
5.95
7.20
13.15
73.60
0.02
0.24
0.20
0.50
0.43
0.44
2.96
0.96
3.84
4.80
79.20
84.00
0.038***
0.473***
0.151***
0.234**
0.221**
0.166 NS
1.009**
1.334*** 162.2 128.1
1.298** 58.2 37.8
1.705*** 220.4 165.9
16.968 NS
10.5
81.8
39.1
30.8
12.9
4.6
6.4
56.3
28.8
36.6
9.2
2.22*
5.85**
4.59*
11.24 NS
5.55 NS
2.65 NS
8.78*
17.21*
9.32*
32.98*
1.30
1.25
0.88
0.49
0.59
0.79
1.24
0.90
0.96
0.91
1.25
1.17
0.88
0.62
0.61
0.56
1.10
0.88
0.85
0.88
0.351 NS
0.222 NS
0.155 NS
0.323 NS
0.216 NS
0.447 NS
0.069*
0.123 NS
0.251 NS
0.173 NS
Coarse roots
Medium roots
Fine roots
Above-ground
Below-ground
Whole plant
Peat
3.8
24.8
40.7
%
15N recovered 86.75
23.369 NS
L = unlimed treatment; L = limed treatment; n = 5.
0
1
NS, not significant; *significant at P < 0.05; **significant at P < 0.01; ***significant at P < 0.001.
needle, shoot and fine-root fractions. Total N in the exception of the medium-root fraction (Table
1
5
the above-ground parts, below-ground parts and 3). Likewise, the percentages N utilization by
whole plants was decreased with liming by 21.0, above-ground parts, below-ground parts and
3
5.1 and 24.7 per cent respectively. Lime appli- whole plants were greater for plants on the
cation decreased the concentration of N in the unlimed peat compared with plants on the limed
1
5
fine-root fraction. Percentage N utilization by peat. Liming decreased total N in the needle,
plant fractions was low in the October experi- shoot and coarse-root fractions. Total N content
ment compared with the April and July experi- in the above-ground parts of the unlimed plants
ments (cf. Tables 2, 3 and 4).
was 30 per cent greater than that for limed plants.
In the April experiment, lime decreased per- Lime application decreased the concentration of
1
5
15
centage N utilization by all plant fractions with N in the shoot fraction. Percentage N recovered

EFFEC T S O F LIM E O N SIT KA SPR UC E SEED LIN G S
397
Table 3: Effects of lime application on percentage 15N utilization by plant fractions and peat soils and on total
and percentage N in plant fractions in April 1994
%
Utilization 15N
————————————— —————————————– ————————————
Total N (mg)
N%
—
Plant fraction
L0
L1
SE
L0
L1
SE
L0
L1
SE
Leader
Needles
Shoots
Stem
Coarse roots
Medium roots
Fine roots
Above-ground
Below-ground
Whole plant
Peat
3.52
16.22
4.91
1.99
0.39
0.23
7.35
26.64
7.97
34.61
60.20
2.37
7.40
2.08
0.90
0.20
0.20
5.25
12.75
5.65
18.40
59.4
77.80
0.396**
2.284*** 119.7
21.8
22.6
89.1
31.9
19.7
3.5
7.33 NS
11.19*
6.66**
8.93 NS
1.22*
1.61 NS
14.56 NS
19.88*
1.95
1.87
1.35
0.70
0.64
0.71
1.66
1.48
1.33
1.45
2.00
1.74
1.19
0.65
0.48
0.64
1.52
1.37
1.21
1.33
0.882 NS
0.977 NS
0.050*
0.323 NS
0.203 NS
0.231 NS
0.372 NS
0.467 NS
0.308 NS
0.446 NS
0.319***
0.122***
0.033**
0.107 NS
0.449*
3.969*** 211.7 163.3
1.018* 50.1 45.7
6.356*** 261.8 209.0
23.995 NS
47.1
23.1
5.6
2.8
41.7
3.1
39.1
12.12 NS
16.55*
%
15N recovered 94.81
8.349*
L = unlimed treatment; L = limed treatment; n = 10.
0
1
NS, not significant;* significant at P < 0.05; **significant at P < 0.01; ***significant at P < 0.001.
Table 4: Effects of lime application on percentage 15N utilization by plant fractions and peat soils and on total
and percentage N in plant fractions in July 1994
%
Utilization 15N
————————————— —————————————– ————————————
Total N (mg)
N%
—
Plant fraction
L0
L1
SE
L0
L1
SE
L0
L1
SE
Leader
Needles
Shoots
Stem
Coarse roots
Medium roots
Fine roots
Above-ground
Below-ground
Whole plant
Peat
2.41
25.16
9.36
5.97
1.84
2.77
21.86
7.77
5.04
1.89
1.103 NS
0.243*** 132.8 116.9
10.7
13.4
5.54 NS
1.74**
0.69**
9.93 NS
3.89 NS
2.22 NS
6.34*
11.21*
20.25 NS
17.05*
1.47
1.55
0.96
0.60
0.50
0.57
1.40
1.13
1.01
1.10
1.54
1.54
0.95
0.62
0.49
0.65
1.26
1.14
0.92
1.09
0.594 NS
0.577 NS
0.463 NS
0.254 NS
0.259 NS
0.227 NS
0.023**
0.338 NS
0.387 NS
0.299 NS
0.091***
0.013***
0.577 NS
0.358 NS
0.076***
0.123*** 228.6 204.7
0.248** 65.0 57.4
0.100*** 293.6 262.1
0.319**
52.5
32.6
10.6
4.7
45.7
28.7
10.6
5.0
0.81
0.92
8.24
10.78
42.90
13.43
56.33
35.60
49.7
41.8
37.44
11.05
48.49
45.30
93.79
%
15N recovered 91.93
21.568 NS
L = unlimed treatment; L = limed treatment; n = 10.
0
1
NS, not significant;* significant at P < 0.05; **significant at P < 0.01; ***significant at P < 0.001.
in the unlimed peat was higher than that in the peat was 27 per cent greater than that by the
limed peat. unlimed peat. Total N in the needles, shoots, fine
With regard to the July experiment, lime roots, above-ground parts and whole plants was
1
5
decreased the percentage
N utilization in decreased by liming. The application of lime had
needles, shoots, stem, fine roots, above-ground a significant effect only on the concentration of N
parts, below-ground parts and whole plants in the fine roots decreasing it from 1.4 to 1.26 per
1
5
(
Table 4). Percentage N utilization by the limed cent.

3
98
FO R EST RY
Table 5 shows the effect of lime on the dry high concentration of extractable NO -N in the
3
weight of various plant fractions. Growing plants limed peat observed in this study might have been
on the limed peat had no effect on the dry weight derived from increased nitrification due to higher
of plant fractions except for the fine-root fraction populations and activities of microorganisms
in October. The dry weight of this fraction was under less acid conditions (Adams and Cornforth,
lower with lime than without lime.
1973; Carey et al. 1981).
The plants grown on the limed peat had black-
Concentration of extractable organic N in the
ened roots and many of their root tips were killed limed peat was high in both the April and July
compared with plants grown on the unlimed peat. experiments compared with the unlimed peat.
The mycorrhizal populations were lower in the This might be due to immobilization of peat
limed peat than those in the unlimed peat.
nitrogen in microorganisms, whose populations
increased as a result of liming. There were no
differences in concentration of peat extractable
NH4+-N between the limed and unlimed peat for
the July experiment. This could be because the
Discussion
Ammonium (NH4+) and nitrate (NO ) are the difference in percentage N utilized by the plants
–
3
major inorganic nitrogen ions in the soil. The grown with or without limed peat was low in July
concentration of these ions in the root zone is compared with that in April. In addition, concen-
controlled by the rate of mineralization and nitri- tration of extractable NO -N in the limed peat in
3
fication. Nitrogen mineralization is the biologi- April was 11.7 times greater than that in July,
cally mediated release of organically bound suggesting a higher rate of nitrification in April.
+
–
15
nitrogen and its conversion into NH4 and NO . Percentages of N utilized by whole plants
3
Net mineralization will occur only when the grown in limed and unlimed peats in July were
nitrogen released by decomposition exceeds that 1.6 and 2.6 times, respectively, higher than those
required by the microflora (Carlyle, 1986). This utilized by these plants in April. This could be due
occurs when the substrate C:N ratio decreases to to the generally higher concentration of
+
that of microbial biomass; thus the C:N ratio at extractable NH4 -N in the peat soils in April
which mineralization begins can be associated compared with July.
with site and other factors (Berg and Ekbohm,
1
It is clear that an increased concentration of
983). In high C:N litter, essentially all nitrogen NO3– in the peat soil is one of the long-term
is immobilized by microorganisms and is not effects of liming. What proportion of this is the
available to higher plants (Dickson, 1989). The direct result of nitrification was not determined in
Table 5: Effects of lime application on plant dry weight (g) in October, April and July
October 1993
April 1994
July 1994
—————————————— —————————————– ————————————
Plant fraction
L0
L1
SE
L0
L1
SE
L0
L1
SE
Leader
Needles
Shoots
Stem
Coarse roots
Medium roots
Fine roots
Above-ground
Below-ground
Whole plant
0.81
6.54
4.44
6.29
2.19
0.58
3.28
18.8
6.05
24.3
0.51
4.81
3.27
5.90
1.51
0.67
2.25
14.49
4.43
18.92
0.469 NS
2.765 NS
2.899 NS
3.031 NS
0.927 NS
0.311 NS
0.522*
7.951 NS
3.733 NS
9.405 NS
1.12
6.40
3.49
3.30
0.87
0.39
2.51
1.13 0.320 NS
5.12 2.221 NS
2.68 1.399 NS
3.03 1.457 NS
0.73 0.338 NS
0.49 0.241 NS
2.57 0.602 NS
0.73
8.57
5.47
5.43
2.11
0.83
3.55
0.87
7.59
4.81
4.63
2.16
0.77
3.32
0.332 NS
3.453 NS
2.810 NS
2.743 NS
1.101 NS
0.388 NS
1.134 NS
7.771 NS
2.297 NS
9.978 NS
14.31 11.96 5.210 NS 20.20 17.90
3.77 3.79 1.027 NS 6.49 6.25
18.08 15.75 6.353 NS 26.69 24.15
L = unlimed treatment; L = limed treatment; n = 5 in October and n = 10 in April and July.
0
1
NS, not significant; *significant at P < 0.05.

EFFEC T S O F LIM E O N SIT KA SPR UC E SEED LIN G S
399
this study. However, higher extractable NO3– 1987) with the result that a proportion of 15
N
levels could have had an important effect on was stored directly in the root system (Millard
reduction of nitrogen uptake by roots of plants and Proe, 1992). The present results are in agree-
grown on the limed peat. The current result is in ment with results reported by Millard and Proe
agreement with results reported for Norway (1993) for P. sitchensis plants. Among the plant
spruce by Persson (1988) and for Larix kaempferi fractions, fine roots and needles utilized the
1
5
trees by Arnold and Van Diest (1991). Nitrogen highest percentages of N. In P. sitchensis, the
can be taken up by mycorrhizae associated with main storage site for N is the needles of the
fine roots (Liljelund and Nihlgård, 1988). They current year, but roots can also store N (Millard
are able to absorb ammonical nitrogen and pass and Proe, 1993).
it on in some form to their host (Brady, 1984).
For April and July, the average percentages 15
N
Bigg (1982), in his study on P. sitchensis seedlings, utilized by the above-ground parts were 2.9 and
observed that P. sitchensis seedlings infected with 3.3 times higher, respectively, than those utilized
Lactarius rufus mycorrhizal fungi had root by the below-ground parts when data for limed
systems that were 66 per cent heavier and 38 per and unlimed treatments were combined. On
cent longer than those of uninoculated seedlings. average, the above-ground parts contained 3.9
He also found that this species of mycorrhizae and 3.5 times more total N than that did the
grew well when ammonium was supplied, but below-ground parts for April and July respec-
was completely unable to utilize nitrate. Thus, tively. Millard and Proe (1992) found that P.
any enhancement of nitrification as a result of sitchensis could remobilize N from roots to
liming could lower populations of mycorrhizae support the growth of new foliage in spring. The
1
5
and N uptake by them. In addition, the direct percentage N utilization and the total N con-
mineralization and cycling of nitrogen by mycor- tents were highest in the fine-root, needle and
rhizae are important for increasing the avail- shoot fractions, which might be due to the high
ability of nitrogen in the soil (Vogt et al., 1982).
demands of these fractions for N and transloca-
In the current study, the decrease in nitrogen tion of N from old to young tissues for reuse
uptake by plants grown on limed peat compared (Miller, 1986). The leader, needles and fine roots
with those grown on unlimed peat could also be contained the highest concentrations of N in all
due to decreasing fine-root length and number of three experiments. This was probably due to the
root tips as a result of growing plants under limed capacity of these fractions to store N during the
conditions for a short time (Kakei, 1995). A posi- autumn and winter (Millard and Proe, 1992) as
tive correlation between nutrient uptake and fine- well as to the high activity of these fractions
root length would be expected since root length during the spring and summer growing season
is important for resource acquisition. Lehto (Hulm and Killham, 1990).
(
1994) also found that liming decreased numbers
In the current study, growth of plants on a
of short root tips of Picea abies. The latter author limed peat soil did not affect the dry weight of
concluded that lime directly and adversely plant fractions except in the case of fine roots in
affected the mycorrhizal populations. Root tips October. Negative effects of liming on fine-root
are important sites for nutrient uptake (Mengel growth when plants are grown under limed con-
and Kirkby, 1982). Hence, any changes in the ditions for a short time have also been reported
number of functional root tips will affect the by Murach (1988) and Kakei (1995).
uptake of nutrient minerals including N.
For the October experiment, percentage 15N
utilization by the below-ground parts was higher
than that for the above-ground parts, particularly
Conclusions
in the case of the plants grown on limed peat. The Liming of a peat soil led 28 years later to a higher
1
5
–
average percentage N utilization by the below- concentration of extractable NO3 some of which
ground parts was 1.6 times greater than that by might have derived from nitrification. Extractable
the above-ground parts for the limed and unlimed organic N and total extractable N in the peat soil
1
5
treatments taken together. This might be due to were also increased by liming. Percentage N uti-
continued root growth (cf. Van Den Driessche, lization and total N were decreased in 3-year-old

4
00
FO R EST RY
Sitka spruce plants that were grown in pots con-
taining the limed peat. The needles and fine roots
of plants growing in pots containing peat soils
were the main organs for the utilization and
storage of nitrogen. During the growing season,
the above-ground parts were the major regions
sitchensis (Bong.) Carr.) forest floor. 1. Influence of
lime and fertilisers. For. Ecol. Manage. 3, 209–222.
Carlyle, J.C. 1986 Nitrogen cycling in forested ecosys-
tems. For. Abstr. 47, 308–336.
Dickson, D.A. 1972 Effects of limestone, phosphate
and potash on the early growth and nutrient uptake
of Sitka spruce [Picea sitchensis (Bong.) Carr.]
planted on deep peat in Northern Ireland. In Trans-
actions of the 4th International Peat Congress 111.
Helsinki, 479–488.
1
5
15
utilizing N while in the fall N utilization by
plants was lower and the roots were the dominant
sink for nitrogen particularly in the case of plants
1
5
grown on the limed peat. The decrease in N uti- Dickson, R.E. 1989 Carbon and nitrogen allocation in
lization by the Sitka spruce plants grown on the trees. Ann. Sci. For. 46, 631–647.
limed peat might be caused by a reduction in myc- Farrell, E.P. 1985 Long-term study of Sitka spruce
(Picea sitchensis (Bong.) Carr.) on blanket peat. 1.
orrhizal populations associated with fine roots in
combination with a high transformation rate of
Water-table depth, peat depth and nutrient minerali-
sation studies. Ir. For. 42(2), 92–105.
+
–
peat nitrogen from NH4 -N to NO -N.
3
Hulm, S.C. and Killham, K. 1990 Response over
1
5
growing seasons of a Sitka spruce stand to N-urea
fertilizer. Plant Soil 124, 65–72.
Acknowledgements
Kakei, M. 1995 Effects of lime application on fine-root
development of Sitka spruce [Picea sitchensis (Bong.)
Carr.] trees grown on deep peat soils. Ph.D. thesis,
Department of Biology and Biochemistry, The
Queen’s University of Belfast, 281 pp.
Kamprath, C.D. and Foy, C.D. 1985 Lime-
fertilizers–plant interaction in acid soils. In Fertilizer
Technology and Use. 3rd edn. O. P. Engelstad (ed.).
Soil Science Society of America, Madison, Wis.,
This study was undertaken in the Department of Agri-
cultural and Environmental Science, Research Division,
Department of Agriculture for Northern Ireland. Pro-
fessor K.M. Garrett, Dr John Bailey and Dr Catherine
Watson from the same department are gratefully
acknowledged for their invaluable scientific advice and
help. Invaluable assistance was also given by Mr Harry
Nicholson. Statistical analysis was assisted by Dr David
Kilpatrick and the staff of Department of Biometrics.
Castlederg Forest Nursery of the Forest Service of
Northern Ireland supplied Sitka spruce seedlings for the
experiments.
9
1–151.
Lehto, L. 1994 Effects of soil pH and calcium on myc-
orrhizas of Picea abies. Plant Soil 163, 69–75.
Liljelund, L.E. and Nihlgård, B. 1988 Nutrient balance
in forests affected by air pollution. In Liming as a
Measure to Improve Soil and Tree Condition in Areas
Affected by Air Pollution. F. Andersson and T.
Persson (eds). National Swedish Environmental Pro-
tection Board, Solna, Report 3518, 93–115.
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