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Effects of wood ash and nitrogen fertilization on Scots pine crown biomass
ARTICLE IN PRESS
Biomass and Bioenergy 31 (2007) 700–709 www.elsevier.com/locate/biombioe
Effects of wood ash and nitrogen fertilization on Scots pine crown biomass R. Ozolincˇius, I. Varnagiryte’ -Kabasˇ inskiene’ , V. Stake’ nas, V. Miksˇ ys Lithuanian Forest Research Institute, Liepu 1, Girionys, LT-53101 Kaunas District, Lithuania Received 24 April 2007; accepted 4 June 2007 Available online 15 August 2007
Abstract The crown biomass, being one of the most susceptible components of the above-ground tree biomass, could respond positively to environmental changes and temporary increase in nutrient availability. The influence of wood ash and nitrogen fertilization on crown biomass was studied in a 40-year-old Scots pine (Pinus sylvestris L.) stand growing on a Haplic Arenosol. The 36-model trees for the crown biomass measurements were sampled for 3 growing seasons after the application of 5.0 t wood ash ha1, 180 kg N ha1, 2.5 t wood ash ha1 plus 180 kg N ha1, and control (untreated plots). The masses of the current, 1-year-old and older needles and shoots, and branches were measured. A significant influence on the current year needles and shoots was found after the application of 180 kg N ha1 or 2.5 t wood ash ha1 plus 180 kg N ha1. When wood ash was applied in combination with nitrogen, an extra response tendency of the crown growth, especially of the top and the middle sections of the crown, was determined. However, there was no short-term influence of wood ash on crown biomass growth. r 2007 Elsevier Ltd. All rights reserved. Keywords: Scots pine; Wood ash; Nitrogen; Fertilization; Crown biomass
1. Introduction The new focus on biofuels as a CO2-neutral energy source may lead to increased utilization of forest biomass. Lithuania is committed to reducing CO2 emissions under the Kyoto agreement by at least 8% from the 1990 rates during the period 2008–2012. Consumption of renewable energy sources is planned to be 12–15% of the total energy balance in the country by 2010. Thus, wood fuel can constitute a substantial proportion of the primary energy sources in the near future. The sustainable utilization of biomass fuels requires recycling of the nutrients removed with the biomass, and these can be compensated by wood ash recycling [1–3]. Since wood ash contains acid-buffering substances and most nutrients, except nitrogen (N), its recycling to the forest could be the way to compensate for the nutrients Corresponding author. Tel.: +370 37 547221; fax: +370 37 547446.
E-mail addresses: [email protected] (R. Ozolincˇius), [email protected] (I. Varnagiryte’ -Kabasˇ inskiene’ ), [email protected] (V. Stake’ nas), [email protected] (V. Miksˇ ys). 0961-9534/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biombioe.2007.06.016
removed by harvesting and leaching, and to counteract the acidification of forest soils. In regions with low N deposition or poor sandy soils, compensation with N may also be required. It is well known that the balance between N and other nutrients plays an important role in forest growth and nutrition [4,5]; however, the growth of different tree components could also be influenced differently by deposition rates, weather conditions, site fertility, etc. [6,7]. The application of the nutrients with wood ash and N fertilizers could alter the growth of different biomass components of the trees (stem, living branches, needles). First of all, the fertilization could give a positive growth response, if some of the nutrients are limiting. Ingerslev and Hallba¨cken [8] observed that when the stand did not suffer from nutrient deficiency the general treatment response in terms of biomass production could be insignificant. On the other hand, Jacobson [6] found a positive growth response at more fertile sites. Most often, stemwood increment changes due to forest fertilization are recorded [7,9–11]. Increased stemwood production by 22–36% was found in pine stands only on
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poor sites, but fertilization caused small changes in the needle biomass [10]. Studies from Estonia, where young Scots pines (Pinus sylvestris L.) growing on mineral soils were examined, showed no significant differences in the height and radial growth of trees on plots treated with 2.5–5 t ash ha1 [7]. Similarly, no effect of wood ash was found on the volume growth of Scots pine stands during a 5-year period; however, a significant 42–71% increase occurred after the application of 3 t ash ha1 together with 150 kg N ha1 [12]. Some of the fertilization experiments in Scots pine stands performed in the Nordic countries showed that N was the only element that gave a consistent and significant effect on tree growth [13–16]. Still, the highest production was obtained with additional inputs of P, K and Mg [13]. In Finland, the application of P together with N gave an occasional additional growth response only on more fertile sites [14]. Valinger et al. [17] stated that N fertilization accelerates crown expansion and needle efficiency during the first 5 years, but that no response remains after 12 years. It was hypothesized that stem growth is regulated by crown development [18], so first of all it is essential to define and measure crown biomass components and their chemical contents. Only a small impact of different wood ash treatments on the chemical content of crown biomass components has been found. Moilanen and Issakainen [11] found a slight increase in the concentrations of Ca and K in needles 18 months after wood ash application in a Scots pine stand where wood ash treatments applied with different procedures and at different doses were studied. Application of 3 t ha–1 wood ash to a Scots pine stand in northern Finland showed no effect on needle nutrient concentrations 1 year after the treatment [19]. Jacobson [20] showed that wood ash tended to increase needle K concentrations 1–2 and 3–5 years after ash application, but that this effect disappeared with increasing time after the application. Tree crown biomass could be treated as a responsive and susceptible component of the above-ground biomass, which may be affected by the environmental changes in the short term, i.e. the temporary increase in nutrient availability. Crown biomass studies are always relevant when assessing the mass of slash, which could be left after logging operations. The aim of this study was to determine the influence of wood ash, N, and combined ash+N treatments on the crown biomass. We hypothesized that wood ash applied together with N fertilizers could give an extra response of tree crown growth compared with ash treatment or N alone in Scots pine stands growing on poor sandy soils. 2. Materials and methods The experimental site was located at the Kacergine forest district (541550 N, 231430 E) of the Dubrava Experimental and Training Forest Enterprise in south-western Lithuania.
701
Table 1 Soil profile horizons and their basic characteristics for the Haplic Arenosol used in this study Horizon
Depth (cm)
pH (CaCl2)
N (g kg1)
C (g kg1)
Texture
519 463 19.0
– – Medium sand Medium sand Medium sand Medium sand
Upper
Lower
Ol Olf E
2 1.5 0
1.5 0 1
– 3.5 3.5
7.47 12.2 0.91
Ap
1
30
4.3
0.20
3.41
Bs
30
65
4.8
0.04
0.41
C
65
100
4.8
0.02
0.06
Horizon designation and subscripts (l ¼ litter, lf ¼ litter and fermentation, p ¼ ploughing, s ¼ illuvial accumulation of sesquioxides) according to FAO (1990) [30].
The annual precipitation was 686 mm and the annual mean temperature was 6.5 1C. A Scots pine (Pinus sylvestris L.) stand was planted in 1964, on former agricultural land. The poor medium sandy soil, classified as a Haplic Arenosol, developed on a limnoglacial plain overlying old fluvioglacial sands [21]. The pHCaCl2 was 3.5 in the O+E horizon, and 4.3–4.8 in the mineral soil layers (Table 1). The average tree height was 14.8 m and the mean diameter at breast height was 14.3 cm at the start of the experiment. The standing volume was 174.4m3 ha1 and the stand production class determined as 5.3 m3 ha1 year1. The integrated wood ash and N fertilization field experiment was established in 2002. The experiment included 24 plots (25 20 m) grouped into 4 blocks with 6 different treatments in each block: (a) 1.25 t wood ash ha1, (b) 2.5 t wood ash ha1, (c) 5 t wood ash ha1, (d) 180 kg N ha1, (e) 2.5 t wood ash ha1+180 kg N ha1 and (f) control (untreated) [22] (Fig. 1). Raw (not stabilized) wood ash was obtained from a district heating plant and had the chemical composition given in Table 2: the concentrations of nutrients (P, K, Ca and Mg) as well as heavy metals (Cr, Cd, Pb, Ni, Cu and Zn) were all less than the recommended maximum concentrations used in Sweden for wood ash applied in forests [3] (Table 2). N fertilizer was added in the form of ammonium nitrate. The present study of the effects of compensatory wood ash and N fertilization on Scots pine crown biomass increment was focused on the highest treatment levels: 5 t wood ash ha1, 180 kg N ha1 and 2.5 t wood ash ha1+180 kg N ha1 together with the control, 12 plots altogether (3 replicates of each treatment). The main characteristics of the experimental plots before treatment and during the sampling period are given in Table 3. Sampling of crown biomass components was carried out in the dormant season 2004/2005 on 3 trees per plot, in total 36 trees. The sample trees were selected by first sorting all the trees into diameter classes, and then trees of the diameter of 15.1–17.0 cm were chosen for the estimations. The tree selection method was based on a sampling of trees
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1 4-
4 4-
N
2 4-
5 43 4-
33-3
3-1
3-4
3-K
33-5
2-5
2-2
4-
K
2-3 1-4
33-2 2-1
2-K
2-4 11-5 1-1
Symbole K 1 2 3 4 5
Treatment Control (no treatment) Raw ash: 1.25 t ha-1 (dry mass) Raw ash: 2.5 t ha-1 (dry mass) Raw ash: 5.0 t ha-1 (dry mass) 180 kg N ha-1 (2.5t ash + 180 kg N) ha-1
1-K
1-2
1-3
Fig. 1. Experimental design of the wood ash fertilization experiment.
Table 2 Chemical composition of the wood ash applied in the field experiment Macro-nutrients
Concentrations in applied ash g kg1
Minimum concentrationsa
Heavy metals
Concentrations in applied ash mg kg1
Maximum concentrationsa
P K Ca Mg
2.15 5.29 72.0 9.45
10 30 125 20
Cr Cd Pb Ni Cu Zn
9.51 0.62 4.53 8.05 13.1 73.7
100 30 300 70 400 7000
a
Source: [3].
of class II according to Kraft’s classification, taking into account the minimal influence of cenotic relationships within the ecosystem. The number of branches in each whorl were counted and weighed, and for each whorl an average branch with needles was taken for the dry mass analyses. In the laboratory, each sampled living branch was divided into 4 components: (1) current year shoots with needles, (2) 1-year-old shoots with needles, (3) older shoots with needles and (4) branches and shoots without needles. All the samples were dried at approximately 75 1C until constant mass and weighed. The mass of the needles and shoots of different age were measured separately. The mass of sampled and dried shoots and branches plus needles in grams was multiplied with the number of
branches per whorl. The biomass of each crown section as well as the total crown was calculated by summation of the mass of each whorl. For further calculations, the crown was divided into 3 sections numbered from the top of the tree up to the crown limit. The top section included whorls no. 1–5 from the top of the tree, the middle section included whorls no. 6–10 and the bottom section included whorls no. 11–15. For the chemical analyses, needles were sampled from 3 Scots pine trees in each plot. The current year and 1-yearold needles were sampled from the 5th–7th whorl from the upper 1/3 of the crown in October 2004. The needles were removed from the twigs and grouped into 2 groups according to age: current year and 1-year-old needles. Before analysis, equal quantities of each of the 3 samples
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Table 3 Main characteristics of the experimental plots before treatment (03/2002) and at sampling (10/2004) Treatment
Block no.
Year
No. of trees per hectare
Volume (m3 ha1)
Basal area (m2 ha1)
Average DBH (cm)
Average height (m)
Control
1
03/2002 10/2004 03/2002 10/2004 03/2002 10/2004
1733 1733 1600 1556 1689 1644
234.9 260.8 180.1 222.4 172.2 201.4
31.4 34.2 25.0 29.6 24.3 27.4
15.2 15.9 14.1 15.6 13.5 14.6
15.2 15.5 14.7 15.4 14.4 15.0
03/2002 10/2004 03/2002 10/2004 03/2002 10/2004
1644 1600 1422 1422 1644 1644
186.9 209.3 126.6 147.6 165.5 203.7
25.4 27.8 18.4 20.7 23.4 27.6
14.0 14.9 12.8 13.6 13.5 14.6
14.6 15.1 14.1 14.6 14.4 15.0
03/2002 10/2004 03/2002 10/2004 03/2002 10/2004
1467 1467 1867 1867 1689 1689
194.2 221.7 178.4 215.1 137.9 177.7
26.1 29.1 25.5 29.5 20.4 24.8
15.1 15.9 13.2 14.2 12.4 13.7
15.1 15.5 14.3 14.8 13.8 14.6
03/2002 10/2004 03/2002 10/2004 03/2002 10/2004
1467 1422 1778 1733 1156 1156
193.0 217.6 125.1 166.7 148.8 188.0
26.0 28.5 19.3 23.8 20.1 24.4
15.0 16.0 11.8 13.2 14.9 16.4
15.1 15.6 13.5 14.4 15.0 15.7
2 3 5 t ash ha1
1 2 3
180 kg N ha1
1 2 3
(2.5 t ash+180 kg N) ha1
1 2 3
from each plot were pooled to form a composite sample and were dried at 60 1C for 24 h [23]. Total N was analysed by the Kjeldahl method. Total P was determined by the colorimetric method and total K by flame photometry. The statistical significance of the differences in various biomass indices and nutrient concentrations between the treatments was tested using analysis of variance and pairwise t-tests. The wood ash treatment, N addition and combined ash+N treatment were chosen as fixed factors. Significant differences of the effects of single treatments were considered at the po0.05 significance level. 3. Results 3.1. Effects on crown biomass No significant ash, N or combined ash plus N treatment influence on the total crown biomass was determined 3 growing seasons after the application (Table 4). However, the wood ash applied together with N increased the mass of the total crown from 12.5 kg (control) to 16.5 kg (2.5 t ash plus 180 kg N). This treatment also increased the mass of the needles by 40%. Only a small increasing tendency in the various crown biomass components was found when wood ash or N alone was applied. The N and wood ash applied together with N significantly increased the mass of the current and 1-yearold needles and shoots (Fig. 2). The mass of the current year needles increased from 1.3 kg (control) to 2.2 kg
(2.5 t ash plus 180 kg N) on average per tree. The influence of the combined treatment (ash plus N) was about 15% stronger than that of the N treatment alone. Comparable changes in the mass of the 1-year-old pine needles were also found: a significant increase by about 1.5 times compared with the control was caused by ash plus N addition (Fig. 2). Thus, the strongest significant increase, with p values varying from p ¼ 0.001 to 0.011 in the current and 1-yearold needles, was found when 2.5 t ash plus 180 kg N was applied (Table 5). The mass of the current and 1-year-old pine shoots without needles also increased from 0.4 to 0.5 kg (control) to about 0.7 kg per tree on average in response to N and ash plus N treatment (Fig. 2). A significant increase of the shoot mass was caused by N addition, with p values varying from p ¼ 0.018 to 0.047, and by ash plus N application, when p values varied from p ¼ 0.005 to 0.032 (Table 5). The highest mass increase for current year needles and shoots compared with older ones, by 1.6–1.8 times, was found when the ash was applied together with N (Fig. 2). There were no differences and no treatment effects on the older needle and shoot mass (in all cases p40.05). No significant wood ash effects on the mass of the current and 1-year-old needles and shoots were found (Fig. 2, Table 5). The comparison of each treatment with each of the other treatments for different crown biomass indices is given in Table 6. The higher mass of the current and 1-year-old needles and shoots that was determined after the addition
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Table 4 Effects of wood ash, nitrogen, and ash together with nitrogen on total crown biomass, needles, shoots, and branches 3 growing seasons after treatment Treatment
Biomass (kg)
Control 5 t ash/ha 180 kg N/ha (2.5 t ash+180 kg N) ha1
Total crown (without stem)
All needles
All shoots and branches
12.4871.87 13.9670.64 15.3072.15 16.5272.12
3.4770.52 3.8870.25 4.5270.48 5.0070.44
9.0371.38 10.1070.39 9.8170.91 11.5171.67
There were no significant differences at the po0.05 level.
3.5
Mean mass, kg per tree
3.0 2.5 2.0
1.61
Control
5 t ash /ha
180 kg N /ha
2.5 t ash + 180 kg N /ha
** * 2.14 1.91
*** ** 2.17 1.89 1.40 1.47
1.34
1.5 0.72 0.79 0.72 0.70
1.0 0.5 0.0
Mean mass, kg per tree
Current year needles 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0
One-year-old needles
Older needles 16
* 0.65
** 0.72
*
* 0.71
0.62 0.39
0.50
0.47 0.52
14 12
10.60 8.73 9.70 9.21
10 8 6 4 2 0
Current year shoots (without needles)
One-year-old shoots (without needles)
Older shoots and branches (without needles)
Fig. 2. Mean biomass of the current and 1-year-old needles, shoots and branches (without needles) in the Scots pine stand 3 growing seasons after the application of wood ash, nitrogen and wood ash together with nitrogen. Asterisks indicate significant differences from the control: *po0.05; **po0.01; ***po0.001.
of N or ash plus N differed significantly from the control. The application of N significantly influenced the length of the current year shoots compared with the control. There were no significant differences between the treatments of wood ash and N alone. Comparing fertilization with wood ash and ash plus N, the combined ash plus N treatment had a stronger positive effect on the current and 1-year-old needles and shoots. The latest changes were determined when the mass of 50 current year needles was analysed (p ¼ 0.02), and a slight influence (p ¼ 0.08) of treatment on the length of the current year shoots was found (Table 6). The detailed analyses of the current and 1-year-old needles in each of 3 crown sections showed the highest increase in the needle mass after the addition of N and ash plus N (Table 7). The combined treatment increased the
mass of the needles significantly by 1.6 times in the top (po0.05) and middle (po0.01) sections of the crown. Compared with the ash treatment alone, the ash plus N treatment gave 1.2–1.5 times greater needle mass in the whole crown, and 1.6 times greater N impact in the bottom section of the crown. In the top section, a significant (po0.05) wood ash effect on the current and 1-year-old needle mass was determined, contrary to the case for the total needle mass. Here, the application of wood ash increased needle mass by 1.4 times compared with the control. There was no significant ash influence on needle mass in other crown sections (Table 7). Very similar increasing tendencies were found for the shoot mass after the application of wood ash together with N. In the top and middle sections of the crown, the increase
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Table 5 Effects of wood ash and nitrogen treatments on some crown biomass indices 3 growing seasons after treatment Biomass
Effect 5 t ash ha1
180 kg N ha1
(2.5 t ash+180 kg N) ha1
Current and 1-year-old shoots Current year needles Current year shoots (without needles) Current year needles and shoots One-year-old needles One-year-old shoots (without needles) One-year-old needles and shoots
0.176 0.142 0.144 0.740 0.479 0.647
0.011* 0.018* 0.011* 0.029* 0.047* 0.023*
0.001* 0.005* 0.001* 0.011* 0.032* 0.013*
Older shoots Older needles Older shoots (without needles) Older needles and shoots
0.624 0.563 0.470
0.272 0.392 0.174
0.857 0.240 0.102
Other indices Mass of 50 current year needles Total length of current year shoots Total crown (without stem)
0.698 0.502 0.404
0.993 0.322 0.082
0.894 0.777 0.544
Significant effect of the treatment (one-way ANOVA) indicated by *po0.05. The strongest effects of wood ash and N treatment compared to pure ash and nitrogen are shown in bold.
Table 6 Comparison of the different treatment effects on some crown biomass indices 3 growing seasons after the treatment Treatment
Pairwise comparison of crown biomass indices Current year
Control Control Nitrogen Ash+N Ash+N Ash+N
Nitrogen Ash Ash Nitrogen Control Ash
One-year-old
Needles
Shoots
Shoots+needles
Needles
Shoots
Shoots+needles
0.006 0.157 0.147 0.151 0.000 0.006
0.007 0.257 0.095 0.458 0.001 0.019
0.004 0.161 0.111 0.189 0.000 0.006
0.017 0.726 0.038 0.261 0.001 0.002
0.073 0.535 0.227 0.291 0.006 0.028
0.023 0.658 0.060 0.236 0.001 0.004
Total crown
Mass of 50 cur. yr. needles
Length of cur. yr. shoots
0.164 0.461 0.502 0.543 0.050 0.205
0.098 0.175 0.753 0.020 0.000 0.009
0.022 0.629 0.064 0.067 0.616 0.985
Significant differences (pairwise comparisons) at the level po0.05 are shown in bold.
of the mass of both current and 1-year-old needles exceeded that of the control by 1.7–1.8 times, and in the bottom part of the crown by 1.5 times. N applied alone increased the mass of the current year shoots by 1.5–1.7 times in the crown, while the mass of 1-year-old shoots increased by 1.6 times in the bottom crown section. Wood ash insignificantly (by 1.5 times) increased the mass of the current and 1-year-old shoots, similarly to the changes in needle mass. 3.2. Changes in needle nutrient content There were no significant effects on N concentrations in the current and 1-year-old needles 3 growing seasons after the application of 5.0 t ha1 of wood ash. The application of N increased the concentration of N from 13.9–14.3 g kg1 (control) to 15.9–17.2 g kg1 (N treatment) in both current and 1-year-old needles (Table 8).
The N concentrations in both the current year and 1-yearold needles were similar. Both the ash and the N treatment insignificantly elevated the Ca concentration. The concentrations of P, K and Mg were not significantly affected either by the wood ash or the N treatment for any of the needle types. Still, the concentrations of Mg and P showed small increases after wood ash application. The concentrations of N, P, K, Ca and Mg in all treatments and the control varied within the range of optimal levels [24,25], and the N concentration seemed to be even higher after N treatment (Table 8). About 1.2–1.3 times higher N, and 9–10% higher amounts of P, were found in the current and 1-year-old needles in the plots treated with N (Fig. 3). K amounts, however, did not differ between the treatments. The application of N fertilizers decreased the amount of K by 20% in the current year needles, while in older needles it increased from 6.671.0 to 7.170.6 g per tree on average.
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Table 7 Mean biomass of current and 1-year-old needles and shoots (without needles) in the top (whorls 1–5 from the top of the tree), middle (whorls 6–10) and bottom (whorls 11–15 from the top, up to the crown limit) sections of the crown Treatment
Crown section Top section
Middle section
Bottom section
Current year needles (g) Control 5 t ash ha1 180 kg N ha1 (2.5 t ash+180 kg N) ha1
309.49735.34 465.70756.76** 438.02773.87 548.86771.91**
707.48772.71 863.947112.76 951.33775.05** 1206.817104.04***
295.06733.14 242.23736.27 385.35774.55 340.62758.96
One-year-old needles (g) Control 5 t ash ha1 180 kg N ha1 (2.5 t ash+180 kg N) ha1
97.00711.16 157.04715.45** 163.93726.58** 189.48730.60**
198.46729.30 251.10734.28 303.51738.87* 392.32747.24***
86.96718.48 76.90714.58 146.91733.91 120.34724.61
Current year shoots (without needles) (g) Control 5 t ash ha1 180 kg N ha1 (2.5 t ash+180 kg N) ha1
257.75742.80 320.21756.87 306.48738.17 387.00766.74
754.96791.16 799.66798.57 959.49742.96* 1189.737108.16**
348.79743.86 290.04755.91 472.86786.87 465.12786.97
One-year-old shoots (without needles) (g) Control 5 t ash ha1 180 kg N ha1 (2.5 t ash+180 kg N) ha1
126.06719.85 170.57727.67 165.72724.27 196.30737.10
256.39735.37 251.55746.46 296.63721.04 369.12744.45*
74.09710.44 82.77711.48 122.02724.34* 117.80726.17
Significant effect of the treatment indicated by * po0.1, ** po0.05, *** po0.01.
Table 8 Concentrations of N, P and K (g kg1) in the current and 1-year-old needles 3 growing seasons after wood ash and nitrogen application Treatment
N
P
K
Ca
Mg
Current year needles Control 5 t ash ha1 180 kg N ha1
13.9070.35 14.4370.66 15.8770.48*
1.4370.03 1.5070.06 1.5770.03*
4.7770.41 4.3370.30 3.9370.07
2.2370.45 2.8770.12 2.8770.18
1.2370.12 1.5070.06 1.3070.10
One-year-old needles Control 5 t ash ha1 180 kg N ha1
14.4370.37 14.3070.35 17.2370.20*
1.4370.07 1.5070.06 1.5770.03
4.1070.21 3.9370.07 4.4770.09
3.3370.38 3.7770.19 3.5770.32
1.0070.15 1.2170.06 1.0070.10
Critical levels of deficiency for concentrations [24] Optimal levels for concentrations in Scots pine needles [25]
12–15 15–16
1.2–1.5 1.0–1.3
3.5–5.5 4.5–6.0
0.4–0.7 0.5–3.0
0.4–0.8 0.6–1.2
Mean values and SE are given for each treatment, n ¼ 3. Significant effect of the treatment indicated by * po0.05.
The concentration of Ca increased by 1.3 times in the current year needles, and up to 10% in the 1-year-old needles, after both wood ash and N addition. A small increase in the Mg concentration was found after N application, and an increase by 20% in wood-ash-treated plots. 4. Discussion In the present study, it was assumed that there was no significant response of the stand growth to the application of wood ash, at least with regard to the most usual stand
parameters such as basal area, average stand DBH or stand height (Table 3). Except after application of additional amounts of nutrients together with wood ash, even a decrease of up to 15% in stand growth relative to the control could be seen. On the other hand, most stand parameters showed an increasing tendency when N or ash in combination with N was applied. The treatment with wood ash and N did not significantly affect the total crown biomass. However, an increasing tendency from on average 12.571.9 kg (control) to 14.070.6 kg (wood ash) per tree was determined (Table 4). Compared with the control, an increase of the total crown
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Control 5 t ash /ha
30
Mean content, g per tree
707
180 kgN /ha 25 20 15 10 5 0 Cur.
O ne-yr. N
Cur.
One-yr.
Cur.
P
One-yr. K
Cur.
One-yr. Ca
Cur.
One-yr.
Mg
Fig. 3. Mean content of some nutrients in the current (Cur.) and 1-year-old (One-yr.) needles 3 growing seasons after treatment.
biomass by 23–30% was also found when N and 2.5 t ash plus 180 kg N were applied. Similarly, there was no significant effect of wood ash and N on the average total mass of needles per tree. The highest, though insignificant, positive effect was found when wood ash was applied together with N. The total biomass of the shoots and branches also showed a tendency to increase, comparable to the above-mentioned changes due to the different treatments. The biomass of the shoots and branches increased insignificantly by 9% after the N treatment and by 27% after the application of ash together with N. Wood ash insignificantly affected the mass of the current, 1-year-old and older shoots and branches. The mass of the current year shoots increased from 0.470.1 kg (control) to 0.570.0 kg (wood ash) per tree on average, while that of the 1-year-old shoots was almost unchanged. Even though the total crown biomass did not appear to be significantly influenced by the different treatments, the analyses of the 3 main crown sections gave a slightly different view. The various crown biomass components (current, 1-year-old needles and shoots) increased after the application of wood ash (Fig. 2). However, the only significant effect on the needle mass was determined in the top section of the crown. The biomass of the current year needles and shoots increased by about 20% and that of the 1-year-old needles by 5%, compared with the control. When the 3 crown sections were analysed separately, the mass of the current and 1-year-old needles was significantly higher in the top section on the fertilized plots. It is possible that visible effects of the wood ash on the total crown could occur after some more years, as our study was made after only 3 growing seasons. The results of our experiment were in agreement with earlier studies. In Sweden, there was no wood ash effect after 5 years when 0.3–0.5 t of ash were applied [26], and a similar result was found in Finland after 5–11 years when 3 t of ash [12] or even after 10–15 years when 3.6–10 t of ash were applied [11]. However, when N is the growth-limiting
factor in stands growing on mineral soils [4], addition of other nutrients is unlikely to cause an increase of tree growth. In our experiment, clearer effects on various tree crown biomass indices were obtained after the application of N. Most often, the addition of N is recorded as the only treatment which could give a significant biomass increase [16,27]. In the present study, N, and also ash together with N, applied on a sandy soil gave a significant positive growth response on the active crown biomass. Earlier studies have shown that this combination of fertilizers usually results in a growth increase and that fertilizer treatments containing N have a growth-promoting effect on Scots pine [13,14,17]. It is important to add that for practical operations, wood ash recycling or its combination with other fertilizers, which have often been suggested for nutrient management, may, over time, affect stand growth in different ways [28]. The question still remains whether the combined ash plus N treatment gives extra stand growth under any conditions. Saarsalmi et al. [12] stated that wood ash, as a soilameliorating amendment, might be useful on forested mineral soils as long as it is supplied together with N. Some authors [13,14] also recorded that a combined treatment with different nutrients could give a higher positive response in terms of stand growth on mineral soils. The highest production was obtained after the application of P, K, Mg and micronutrients in Sweden and Norway [13], while in Finland the application of P together with N gave a growth response on more fertile sites [14]. However, other studies have shown that wood ash reduces the response to N fertilization [29] or that there are no differences if N alone or ash together with N is applied in Scots pine stands on poor sites [6]. To explain the above-mentioned disagreements, we statistically tested the changes in the crown biomass components under different treatments. Our results indicate that raw wood ash applied in combination with N
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significantly increased the biomass of only the current and 1-year-old needles and shoots but not of the older components of the pine trees. Despite the non-significant difference between the treatments of N and ash combined with N, the combination effect could be treated as an extra response compared not only to ash but also to N alone. The nutrient content in the needles also appears to be an important factor for the development of the crown biomass. The N treatment resulted in significantly elevated N concentrations in the current year and 1-year-old needles, while wood ash alone had no influence on the N concentration in the needles 3 growing seasons after treatment. The high availability of N in the N treatment seems to have stimulated uptake of Ca in the needles, as did the ash treatment. Still, analyses of the crown nutrient content did not highlight any effect of the treatments and showed no higher nutrient mobilization to the active crown biomass. The results from this study confirm that the effects of wood ash application on needle concentrations in Scots pine are quite small [11,19]. These results suggest that wood ash application should preferably be done together with N fertilization. This treatment might lead to a greater development of crown biomass, and furthermore would regulate stem growth [18]. 5. Conclusions Nitrogen significantly increased the biomass of the current and 1-year-old shoots and needles. No changes were determined in the older parts of the crown. The effect of wood ash was small and in most cases insignificant. The mass of the current and 1-year-old year needles increased only in the top section of the crown. When wood ash was added in combination with nitrogen, an extra response in terms of crown expansion, especially in the top and middle sections of the crown, was found. Forest fertilization with a combination of nutrients would be preferable to the application of wood ash or nitrogen alone. Acknowledgements This study was supported by the project ‘Wood for Energy—A Contribution to the Development of Sustainable Forest Management (WOOD-EN-MAN, QLK5-CT2001-00527)’ under ‘Quality of Life and Management of Living Resources’. We thank the technicians at the Lithuanian Forest Research Institute for their help with biomass sampling in the forest and the laboratory, the referees for valuable comments on the manuscript, and Nicholas Clarke for language corrections. References [1] Bramryd T, Fransman BO. Silvicultural use of wood ashes—effects on the nutrient and heavy metal balance in a pine (Pinus sylvestris L.) forest soil. Water Air and Soil Pollution 1995;85:1039–44.
[2] Ingerslev M. Vitalization of mature Norway spruce stands by fertilization and liming. In: The research series, vol. 23. Hørsholm: Danish Forest and Landscape Research Institute; 1998. 126pp. [3] Swedish recommendations for the extraction of forest fuel and compensatory fertilizing in Sweden. National Board of Forestry/ Skogsstyrelsen, 2002. [4] Tamm CO. Nitrogen in terrestrial ecosystems, questions of productivity, vegetational changes and ecosystem stability. Berlin: Springer; Ecology Studies 81, 1991. [5] Linder S. Foliar analysis for detecting and correcting nutrient imbalances in Norway spruce. Ecological Bulletins (Copenhagen) 1995;44:178–90. [6] Jacobson S. Addition of stabilized wood ashes to Swedish coniferous stands on mineral soils—effects on stem growth and needle nutrient concentrations. Silva Fennica 2003;37:437–50. [7] Pa¨rn H. Effect of wood ash application on radial and height growth of young Scots pines (Pinus sylvestris L.). Forestry Studies/ Metsanduslikud uurimused 2005;42:48–55. [8] Ingerslev M, Hallba¨cken L. Above ground biomass and nutrient distribution in a limed and fertilized Norway spruce (Picea abies L.) plantation. Part II. Accumulation of biomass and nutrients. Forest Ecology and Management 1999;119:21–38. [9] Ma¨kinen H, Uusvaara O. Effects of fertilization on the branchiness and the wood quality of Scots pine. Foliar Forest 1992;801 [in Finnish with an English summary]. [10] Ma¨lko¨nen E, Kukkola M. Effect of long-term fertilization on the biomass production and nutrient status of Scots pine stands. Fertilizer Research 1991;27:113–27. [11] Moilanen M, Issakainen J. Effects of wood ash on forests. Metsa¨tehon raportti 93, 2000. [12] Saarsalmi A, Ma¨lko¨nen E, Kukkola M. Effects of wood ash fertilization on soil chemical properties and stand nutrient status and growth of some coniferous stands in Finland. Scandinavian Journal of Forest Research 2004;19:217–33. [13] Nilsen P, Abrahamsen G. Scots pine and Norway spruce stand responses to annual N, P and Mg fertilization. Forest Ecology and Management 2003;174:221–32. [14] Kukkola M, Sarama¨ki J. Growth response in repeatedly fertilized pine and spruce stands on mineral soils. Communicationes Instituti Forestalis Fenniae 1983;114. [15] Nilsen P. Fertilization experiments on forest mineral soils: a review of the Norwegian results. Scandinavian Journal of Forest Research 2001;16:541–54. [16] Nohrstedt H-O¨. Response of coniferous forest ecosystems on mineral soils to nutrient additions: a review of Swedish experiences. Scandinavian Journal of Forest Research 2001;16:555–73. [17] Vallinger E, Elfving B, Mo¨rling T. Twelve-year response of Scots pine to thinning and nitrogen fertilization. Forest Ecology and Management 2000;134:45–53. [18] Little CHA, Pharis RP. Hormonal control of radial and longitudinal growth in tree stem. In: Gartner BL, editor. Plant stems: physiology and functional morphology. San Diego: Academic Press; 1995. p. 281–319. [19] Vuorinen M, Kurkela T. Lophodermella sulcigena infection in Scots pine needles and tree nutrition. Forestry 2000;73:239–46. [20] Jacobson S. Fertilization to increase and sustain tree growth in coniferous stands in Sweden. Swedish University of Agricultural Sciences. PhD thesis. Silvestria 2001;217:1–34. [21] ISSS-ISRIC-FAO. World reference base for soil resources. World Soil Resources Report 84. Rome: FAO; 1998. [22] Ozolincius R, Varnagiryte I, Armolaitis K, Karltun E. Initial effects of wood ash fertilization on soil, needle and litterfall chemistry in Scots pine stands. Baltic Forestry 2005;11(2):59–67. [23] UN/ ECE. Manual on methods and criteria for harmonized sampling, assessment, monitoring and analysis of the effects of air pollution on forests. Part IV. Sampling and analysis of needles and leaves. Hamburg/Geneva: Programme Coordinating Centre; 2000 (p. 1–37).
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[28] Ingerslev M, Ma¨lko¨nen E, Nilsen P, Nohrstedt HO¨, Oskarsson H, Raulund-Rasmussen K. Main findings and future challenges in forest nutritional research and management in the Nordic countries. Scandinavian Journal of Forest Research 2001;16:488–501. [29] Pettersson F. Kompensationsgo¨dsling efter tra¨ddelsgallring [Complementary fertilization after whole-tree thinning]. Information va¨xtna¨ring-skogsproduktion 2 1990/1991. Uppsala: Institutet fo¨r Skogsfo¨rba¨ttring; 1990. [30] FAO. Guidelines for soil description. Rome: FAO; 1990.
Biomass and Bioenergy 31 (2007) 700–709 www.elsevier.com/locate/biombioe
Effects of wood ash and nitrogen fertilization on Scots pine crown biomass R. Ozolincˇius, I. Varnagiryte’ -Kabasˇ inskiene’ , V. Stake’ nas, V. Miksˇ ys Lithuanian Forest Research Institute, Liepu 1, Girionys, LT-53101 Kaunas District, Lithuania Received 24 April 2007; accepted 4 June 2007 Available online 15 August 2007
Abstract The crown biomass, being one of the most susceptible components of the above-ground tree biomass, could respond positively to environmental changes and temporary increase in nutrient availability. The influence of wood ash and nitrogen fertilization on crown biomass was studied in a 40-year-old Scots pine (Pinus sylvestris L.) stand growing on a Haplic Arenosol. The 36-model trees for the crown biomass measurements were sampled for 3 growing seasons after the application of 5.0 t wood ash ha1, 180 kg N ha1, 2.5 t wood ash ha1 plus 180 kg N ha1, and control (untreated plots). The masses of the current, 1-year-old and older needles and shoots, and branches were measured. A significant influence on the current year needles and shoots was found after the application of 180 kg N ha1 or 2.5 t wood ash ha1 plus 180 kg N ha1. When wood ash was applied in combination with nitrogen, an extra response tendency of the crown growth, especially of the top and the middle sections of the crown, was determined. However, there was no short-term influence of wood ash on crown biomass growth. r 2007 Elsevier Ltd. All rights reserved. Keywords: Scots pine; Wood ash; Nitrogen; Fertilization; Crown biomass
1. Introduction The new focus on biofuels as a CO2-neutral energy source may lead to increased utilization of forest biomass. Lithuania is committed to reducing CO2 emissions under the Kyoto agreement by at least 8% from the 1990 rates during the period 2008–2012. Consumption of renewable energy sources is planned to be 12–15% of the total energy balance in the country by 2010. Thus, wood fuel can constitute a substantial proportion of the primary energy sources in the near future. The sustainable utilization of biomass fuels requires recycling of the nutrients removed with the biomass, and these can be compensated by wood ash recycling [1–3]. Since wood ash contains acid-buffering substances and most nutrients, except nitrogen (N), its recycling to the forest could be the way to compensate for the nutrients Corresponding author. Tel.: +370 37 547221; fax: +370 37 547446.
E-mail addresses: [email protected] (R. Ozolincˇius), [email protected] (I. Varnagiryte’ -Kabasˇ inskiene’ ), [email protected] (V. Stake’ nas), [email protected] (V. Miksˇ ys). 0961-9534/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biombioe.2007.06.016
removed by harvesting and leaching, and to counteract the acidification of forest soils. In regions with low N deposition or poor sandy soils, compensation with N may also be required. It is well known that the balance between N and other nutrients plays an important role in forest growth and nutrition [4,5]; however, the growth of different tree components could also be influenced differently by deposition rates, weather conditions, site fertility, etc. [6,7]. The application of the nutrients with wood ash and N fertilizers could alter the growth of different biomass components of the trees (stem, living branches, needles). First of all, the fertilization could give a positive growth response, if some of the nutrients are limiting. Ingerslev and Hallba¨cken [8] observed that when the stand did not suffer from nutrient deficiency the general treatment response in terms of biomass production could be insignificant. On the other hand, Jacobson [6] found a positive growth response at more fertile sites. Most often, stemwood increment changes due to forest fertilization are recorded [7,9–11]. Increased stemwood production by 22–36% was found in pine stands only on
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poor sites, but fertilization caused small changes in the needle biomass [10]. Studies from Estonia, where young Scots pines (Pinus sylvestris L.) growing on mineral soils were examined, showed no significant differences in the height and radial growth of trees on plots treated with 2.5–5 t ash ha1 [7]. Similarly, no effect of wood ash was found on the volume growth of Scots pine stands during a 5-year period; however, a significant 42–71% increase occurred after the application of 3 t ash ha1 together with 150 kg N ha1 [12]. Some of the fertilization experiments in Scots pine stands performed in the Nordic countries showed that N was the only element that gave a consistent and significant effect on tree growth [13–16]. Still, the highest production was obtained with additional inputs of P, K and Mg [13]. In Finland, the application of P together with N gave an occasional additional growth response only on more fertile sites [14]. Valinger et al. [17] stated that N fertilization accelerates crown expansion and needle efficiency during the first 5 years, but that no response remains after 12 years. It was hypothesized that stem growth is regulated by crown development [18], so first of all it is essential to define and measure crown biomass components and their chemical contents. Only a small impact of different wood ash treatments on the chemical content of crown biomass components has been found. Moilanen and Issakainen [11] found a slight increase in the concentrations of Ca and K in needles 18 months after wood ash application in a Scots pine stand where wood ash treatments applied with different procedures and at different doses were studied. Application of 3 t ha–1 wood ash to a Scots pine stand in northern Finland showed no effect on needle nutrient concentrations 1 year after the treatment [19]. Jacobson [20] showed that wood ash tended to increase needle K concentrations 1–2 and 3–5 years after ash application, but that this effect disappeared with increasing time after the application. Tree crown biomass could be treated as a responsive and susceptible component of the above-ground biomass, which may be affected by the environmental changes in the short term, i.e. the temporary increase in nutrient availability. Crown biomass studies are always relevant when assessing the mass of slash, which could be left after logging operations. The aim of this study was to determine the influence of wood ash, N, and combined ash+N treatments on the crown biomass. We hypothesized that wood ash applied together with N fertilizers could give an extra response of tree crown growth compared with ash treatment or N alone in Scots pine stands growing on poor sandy soils. 2. Materials and methods The experimental site was located at the Kacergine forest district (541550 N, 231430 E) of the Dubrava Experimental and Training Forest Enterprise in south-western Lithuania.
701
Table 1 Soil profile horizons and their basic characteristics for the Haplic Arenosol used in this study Horizon
Depth (cm)
pH (CaCl2)
N (g kg1)
C (g kg1)
Texture
519 463 19.0
– – Medium sand Medium sand Medium sand Medium sand
Upper
Lower
Ol Olf E
2 1.5 0
1.5 0 1
– 3.5 3.5
7.47 12.2 0.91
Ap
1
30
4.3
0.20
3.41
Bs
30
65
4.8
0.04
0.41
C
65
100
4.8
0.02
0.06
Horizon designation and subscripts (l ¼ litter, lf ¼ litter and fermentation, p ¼ ploughing, s ¼ illuvial accumulation of sesquioxides) according to FAO (1990) [30].
The annual precipitation was 686 mm and the annual mean temperature was 6.5 1C. A Scots pine (Pinus sylvestris L.) stand was planted in 1964, on former agricultural land. The poor medium sandy soil, classified as a Haplic Arenosol, developed on a limnoglacial plain overlying old fluvioglacial sands [21]. The pHCaCl2 was 3.5 in the O+E horizon, and 4.3–4.8 in the mineral soil layers (Table 1). The average tree height was 14.8 m and the mean diameter at breast height was 14.3 cm at the start of the experiment. The standing volume was 174.4m3 ha1 and the stand production class determined as 5.3 m3 ha1 year1. The integrated wood ash and N fertilization field experiment was established in 2002. The experiment included 24 plots (25 20 m) grouped into 4 blocks with 6 different treatments in each block: (a) 1.25 t wood ash ha1, (b) 2.5 t wood ash ha1, (c) 5 t wood ash ha1, (d) 180 kg N ha1, (e) 2.5 t wood ash ha1+180 kg N ha1 and (f) control (untreated) [22] (Fig. 1). Raw (not stabilized) wood ash was obtained from a district heating plant and had the chemical composition given in Table 2: the concentrations of nutrients (P, K, Ca and Mg) as well as heavy metals (Cr, Cd, Pb, Ni, Cu and Zn) were all less than the recommended maximum concentrations used in Sweden for wood ash applied in forests [3] (Table 2). N fertilizer was added in the form of ammonium nitrate. The present study of the effects of compensatory wood ash and N fertilization on Scots pine crown biomass increment was focused on the highest treatment levels: 5 t wood ash ha1, 180 kg N ha1 and 2.5 t wood ash ha1+180 kg N ha1 together with the control, 12 plots altogether (3 replicates of each treatment). The main characteristics of the experimental plots before treatment and during the sampling period are given in Table 3. Sampling of crown biomass components was carried out in the dormant season 2004/2005 on 3 trees per plot, in total 36 trees. The sample trees were selected by first sorting all the trees into diameter classes, and then trees of the diameter of 15.1–17.0 cm were chosen for the estimations. The tree selection method was based on a sampling of trees
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1 4-
4 4-
N
2 4-
5 43 4-
33-3
3-1
3-4
3-K
33-5
2-5
2-2
4-
K
2-3 1-4
33-2 2-1
2-K
2-4 11-5 1-1
Symbole K 1 2 3 4 5
Treatment Control (no treatment) Raw ash: 1.25 t ha-1 (dry mass) Raw ash: 2.5 t ha-1 (dry mass) Raw ash: 5.0 t ha-1 (dry mass) 180 kg N ha-1 (2.5t ash + 180 kg N) ha-1
1-K
1-2
1-3
Fig. 1. Experimental design of the wood ash fertilization experiment.
Table 2 Chemical composition of the wood ash applied in the field experiment Macro-nutrients
Concentrations in applied ash g kg1
Minimum concentrationsa
Heavy metals
Concentrations in applied ash mg kg1
Maximum concentrationsa
P K Ca Mg
2.15 5.29 72.0 9.45
10 30 125 20
Cr Cd Pb Ni Cu Zn
9.51 0.62 4.53 8.05 13.1 73.7
100 30 300 70 400 7000
a
Source: [3].
of class II according to Kraft’s classification, taking into account the minimal influence of cenotic relationships within the ecosystem. The number of branches in each whorl were counted and weighed, and for each whorl an average branch with needles was taken for the dry mass analyses. In the laboratory, each sampled living branch was divided into 4 components: (1) current year shoots with needles, (2) 1-year-old shoots with needles, (3) older shoots with needles and (4) branches and shoots without needles. All the samples were dried at approximately 75 1C until constant mass and weighed. The mass of the needles and shoots of different age were measured separately. The mass of sampled and dried shoots and branches plus needles in grams was multiplied with the number of
branches per whorl. The biomass of each crown section as well as the total crown was calculated by summation of the mass of each whorl. For further calculations, the crown was divided into 3 sections numbered from the top of the tree up to the crown limit. The top section included whorls no. 1–5 from the top of the tree, the middle section included whorls no. 6–10 and the bottom section included whorls no. 11–15. For the chemical analyses, needles were sampled from 3 Scots pine trees in each plot. The current year and 1-yearold needles were sampled from the 5th–7th whorl from the upper 1/3 of the crown in October 2004. The needles were removed from the twigs and grouped into 2 groups according to age: current year and 1-year-old needles. Before analysis, equal quantities of each of the 3 samples
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Table 3 Main characteristics of the experimental plots before treatment (03/2002) and at sampling (10/2004) Treatment
Block no.
Year
No. of trees per hectare
Volume (m3 ha1)
Basal area (m2 ha1)
Average DBH (cm)
Average height (m)
Control
1
03/2002 10/2004 03/2002 10/2004 03/2002 10/2004
1733 1733 1600 1556 1689 1644
234.9 260.8 180.1 222.4 172.2 201.4
31.4 34.2 25.0 29.6 24.3 27.4
15.2 15.9 14.1 15.6 13.5 14.6
15.2 15.5 14.7 15.4 14.4 15.0
03/2002 10/2004 03/2002 10/2004 03/2002 10/2004
1644 1600 1422 1422 1644 1644
186.9 209.3 126.6 147.6 165.5 203.7
25.4 27.8 18.4 20.7 23.4 27.6
14.0 14.9 12.8 13.6 13.5 14.6
14.6 15.1 14.1 14.6 14.4 15.0
03/2002 10/2004 03/2002 10/2004 03/2002 10/2004
1467 1467 1867 1867 1689 1689
194.2 221.7 178.4 215.1 137.9 177.7
26.1 29.1 25.5 29.5 20.4 24.8
15.1 15.9 13.2 14.2 12.4 13.7
15.1 15.5 14.3 14.8 13.8 14.6
03/2002 10/2004 03/2002 10/2004 03/2002 10/2004
1467 1422 1778 1733 1156 1156
193.0 217.6 125.1 166.7 148.8 188.0
26.0 28.5 19.3 23.8 20.1 24.4
15.0 16.0 11.8 13.2 14.9 16.4
15.1 15.6 13.5 14.4 15.0 15.7
2 3 5 t ash ha1
1 2 3
180 kg N ha1
1 2 3
(2.5 t ash+180 kg N) ha1
1 2 3
from each plot were pooled to form a composite sample and were dried at 60 1C for 24 h [23]. Total N was analysed by the Kjeldahl method. Total P was determined by the colorimetric method and total K by flame photometry. The statistical significance of the differences in various biomass indices and nutrient concentrations between the treatments was tested using analysis of variance and pairwise t-tests. The wood ash treatment, N addition and combined ash+N treatment were chosen as fixed factors. Significant differences of the effects of single treatments were considered at the po0.05 significance level. 3. Results 3.1. Effects on crown biomass No significant ash, N or combined ash plus N treatment influence on the total crown biomass was determined 3 growing seasons after the application (Table 4). However, the wood ash applied together with N increased the mass of the total crown from 12.5 kg (control) to 16.5 kg (2.5 t ash plus 180 kg N). This treatment also increased the mass of the needles by 40%. Only a small increasing tendency in the various crown biomass components was found when wood ash or N alone was applied. The N and wood ash applied together with N significantly increased the mass of the current and 1-yearold needles and shoots (Fig. 2). The mass of the current year needles increased from 1.3 kg (control) to 2.2 kg
(2.5 t ash plus 180 kg N) on average per tree. The influence of the combined treatment (ash plus N) was about 15% stronger than that of the N treatment alone. Comparable changes in the mass of the 1-year-old pine needles were also found: a significant increase by about 1.5 times compared with the control was caused by ash plus N addition (Fig. 2). Thus, the strongest significant increase, with p values varying from p ¼ 0.001 to 0.011 in the current and 1-yearold needles, was found when 2.5 t ash plus 180 kg N was applied (Table 5). The mass of the current and 1-year-old pine shoots without needles also increased from 0.4 to 0.5 kg (control) to about 0.7 kg per tree on average in response to N and ash plus N treatment (Fig. 2). A significant increase of the shoot mass was caused by N addition, with p values varying from p ¼ 0.018 to 0.047, and by ash plus N application, when p values varied from p ¼ 0.005 to 0.032 (Table 5). The highest mass increase for current year needles and shoots compared with older ones, by 1.6–1.8 times, was found when the ash was applied together with N (Fig. 2). There were no differences and no treatment effects on the older needle and shoot mass (in all cases p40.05). No significant wood ash effects on the mass of the current and 1-year-old needles and shoots were found (Fig. 2, Table 5). The comparison of each treatment with each of the other treatments for different crown biomass indices is given in Table 6. The higher mass of the current and 1-year-old needles and shoots that was determined after the addition
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Table 4 Effects of wood ash, nitrogen, and ash together with nitrogen on total crown biomass, needles, shoots, and branches 3 growing seasons after treatment Treatment
Biomass (kg)
Control 5 t ash/ha 180 kg N/ha (2.5 t ash+180 kg N) ha1
Total crown (without stem)
All needles
All shoots and branches
12.4871.87 13.9670.64 15.3072.15 16.5272.12
3.4770.52 3.8870.25 4.5270.48 5.0070.44
9.0371.38 10.1070.39 9.8170.91 11.5171.67
There were no significant differences at the po0.05 level.
3.5
Mean mass, kg per tree
3.0 2.5 2.0
1.61
Control
5 t ash /ha
180 kg N /ha
2.5 t ash + 180 kg N /ha
** * 2.14 1.91
*** ** 2.17 1.89 1.40 1.47
1.34
1.5 0.72 0.79 0.72 0.70
1.0 0.5 0.0
Mean mass, kg per tree
Current year needles 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0
One-year-old needles
Older needles 16
* 0.65
** 0.72
*
* 0.71
0.62 0.39
0.50
0.47 0.52
14 12
10.60 8.73 9.70 9.21
10 8 6 4 2 0
Current year shoots (without needles)
One-year-old shoots (without needles)
Older shoots and branches (without needles)
Fig. 2. Mean biomass of the current and 1-year-old needles, shoots and branches (without needles) in the Scots pine stand 3 growing seasons after the application of wood ash, nitrogen and wood ash together with nitrogen. Asterisks indicate significant differences from the control: *po0.05; **po0.01; ***po0.001.
of N or ash plus N differed significantly from the control. The application of N significantly influenced the length of the current year shoots compared with the control. There were no significant differences between the treatments of wood ash and N alone. Comparing fertilization with wood ash and ash plus N, the combined ash plus N treatment had a stronger positive effect on the current and 1-year-old needles and shoots. The latest changes were determined when the mass of 50 current year needles was analysed (p ¼ 0.02), and a slight influence (p ¼ 0.08) of treatment on the length of the current year shoots was found (Table 6). The detailed analyses of the current and 1-year-old needles in each of 3 crown sections showed the highest increase in the needle mass after the addition of N and ash plus N (Table 7). The combined treatment increased the
mass of the needles significantly by 1.6 times in the top (po0.05) and middle (po0.01) sections of the crown. Compared with the ash treatment alone, the ash plus N treatment gave 1.2–1.5 times greater needle mass in the whole crown, and 1.6 times greater N impact in the bottom section of the crown. In the top section, a significant (po0.05) wood ash effect on the current and 1-year-old needle mass was determined, contrary to the case for the total needle mass. Here, the application of wood ash increased needle mass by 1.4 times compared with the control. There was no significant ash influence on needle mass in other crown sections (Table 7). Very similar increasing tendencies were found for the shoot mass after the application of wood ash together with N. In the top and middle sections of the crown, the increase
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Table 5 Effects of wood ash and nitrogen treatments on some crown biomass indices 3 growing seasons after treatment Biomass
Effect 5 t ash ha1
180 kg N ha1
(2.5 t ash+180 kg N) ha1
Current and 1-year-old shoots Current year needles Current year shoots (without needles) Current year needles and shoots One-year-old needles One-year-old shoots (without needles) One-year-old needles and shoots
0.176 0.142 0.144 0.740 0.479 0.647
0.011* 0.018* 0.011* 0.029* 0.047* 0.023*
0.001* 0.005* 0.001* 0.011* 0.032* 0.013*
Older shoots Older needles Older shoots (without needles) Older needles and shoots
0.624 0.563 0.470
0.272 0.392 0.174
0.857 0.240 0.102
Other indices Mass of 50 current year needles Total length of current year shoots Total crown (without stem)
0.698 0.502 0.404
0.993 0.322 0.082
0.894 0.777 0.544
Significant effect of the treatment (one-way ANOVA) indicated by *po0.05. The strongest effects of wood ash and N treatment compared to pure ash and nitrogen are shown in bold.
Table 6 Comparison of the different treatment effects on some crown biomass indices 3 growing seasons after the treatment Treatment
Pairwise comparison of crown biomass indices Current year
Control Control Nitrogen Ash+N Ash+N Ash+N
Nitrogen Ash Ash Nitrogen Control Ash
One-year-old
Needles
Shoots
Shoots+needles
Needles
Shoots
Shoots+needles
0.006 0.157 0.147 0.151 0.000 0.006
0.007 0.257 0.095 0.458 0.001 0.019
0.004 0.161 0.111 0.189 0.000 0.006
0.017 0.726 0.038 0.261 0.001 0.002
0.073 0.535 0.227 0.291 0.006 0.028
0.023 0.658 0.060 0.236 0.001 0.004
Total crown
Mass of 50 cur. yr. needles
Length of cur. yr. shoots
0.164 0.461 0.502 0.543 0.050 0.205
0.098 0.175 0.753 0.020 0.000 0.009
0.022 0.629 0.064 0.067 0.616 0.985
Significant differences (pairwise comparisons) at the level po0.05 are shown in bold.
of the mass of both current and 1-year-old needles exceeded that of the control by 1.7–1.8 times, and in the bottom part of the crown by 1.5 times. N applied alone increased the mass of the current year shoots by 1.5–1.7 times in the crown, while the mass of 1-year-old shoots increased by 1.6 times in the bottom crown section. Wood ash insignificantly (by 1.5 times) increased the mass of the current and 1-year-old shoots, similarly to the changes in needle mass. 3.2. Changes in needle nutrient content There were no significant effects on N concentrations in the current and 1-year-old needles 3 growing seasons after the application of 5.0 t ha1 of wood ash. The application of N increased the concentration of N from 13.9–14.3 g kg1 (control) to 15.9–17.2 g kg1 (N treatment) in both current and 1-year-old needles (Table 8).
The N concentrations in both the current year and 1-yearold needles were similar. Both the ash and the N treatment insignificantly elevated the Ca concentration. The concentrations of P, K and Mg were not significantly affected either by the wood ash or the N treatment for any of the needle types. Still, the concentrations of Mg and P showed small increases after wood ash application. The concentrations of N, P, K, Ca and Mg in all treatments and the control varied within the range of optimal levels [24,25], and the N concentration seemed to be even higher after N treatment (Table 8). About 1.2–1.3 times higher N, and 9–10% higher amounts of P, were found in the current and 1-year-old needles in the plots treated with N (Fig. 3). K amounts, however, did not differ between the treatments. The application of N fertilizers decreased the amount of K by 20% in the current year needles, while in older needles it increased from 6.671.0 to 7.170.6 g per tree on average.
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Table 7 Mean biomass of current and 1-year-old needles and shoots (without needles) in the top (whorls 1–5 from the top of the tree), middle (whorls 6–10) and bottom (whorls 11–15 from the top, up to the crown limit) sections of the crown Treatment
Crown section Top section
Middle section
Bottom section
Current year needles (g) Control 5 t ash ha1 180 kg N ha1 (2.5 t ash+180 kg N) ha1
309.49735.34 465.70756.76** 438.02773.87 548.86771.91**
707.48772.71 863.947112.76 951.33775.05** 1206.817104.04***
295.06733.14 242.23736.27 385.35774.55 340.62758.96
One-year-old needles (g) Control 5 t ash ha1 180 kg N ha1 (2.5 t ash+180 kg N) ha1
97.00711.16 157.04715.45** 163.93726.58** 189.48730.60**
198.46729.30 251.10734.28 303.51738.87* 392.32747.24***
86.96718.48 76.90714.58 146.91733.91 120.34724.61
Current year shoots (without needles) (g) Control 5 t ash ha1 180 kg N ha1 (2.5 t ash+180 kg N) ha1
257.75742.80 320.21756.87 306.48738.17 387.00766.74
754.96791.16 799.66798.57 959.49742.96* 1189.737108.16**
348.79743.86 290.04755.91 472.86786.87 465.12786.97
One-year-old shoots (without needles) (g) Control 5 t ash ha1 180 kg N ha1 (2.5 t ash+180 kg N) ha1
126.06719.85 170.57727.67 165.72724.27 196.30737.10
256.39735.37 251.55746.46 296.63721.04 369.12744.45*
74.09710.44 82.77711.48 122.02724.34* 117.80726.17
Significant effect of the treatment indicated by * po0.1, ** po0.05, *** po0.01.
Table 8 Concentrations of N, P and K (g kg1) in the current and 1-year-old needles 3 growing seasons after wood ash and nitrogen application Treatment
N
P
K
Ca
Mg
Current year needles Control 5 t ash ha1 180 kg N ha1
13.9070.35 14.4370.66 15.8770.48*
1.4370.03 1.5070.06 1.5770.03*
4.7770.41 4.3370.30 3.9370.07
2.2370.45 2.8770.12 2.8770.18
1.2370.12 1.5070.06 1.3070.10
One-year-old needles Control 5 t ash ha1 180 kg N ha1
14.4370.37 14.3070.35 17.2370.20*
1.4370.07 1.5070.06 1.5770.03
4.1070.21 3.9370.07 4.4770.09
3.3370.38 3.7770.19 3.5770.32
1.0070.15 1.2170.06 1.0070.10
Critical levels of deficiency for concentrations [24] Optimal levels for concentrations in Scots pine needles [25]
12–15 15–16
1.2–1.5 1.0–1.3
3.5–5.5 4.5–6.0
0.4–0.7 0.5–3.0
0.4–0.8 0.6–1.2
Mean values and SE are given for each treatment, n ¼ 3. Significant effect of the treatment indicated by * po0.05.
The concentration of Ca increased by 1.3 times in the current year needles, and up to 10% in the 1-year-old needles, after both wood ash and N addition. A small increase in the Mg concentration was found after N application, and an increase by 20% in wood-ash-treated plots. 4. Discussion In the present study, it was assumed that there was no significant response of the stand growth to the application of wood ash, at least with regard to the most usual stand
parameters such as basal area, average stand DBH or stand height (Table 3). Except after application of additional amounts of nutrients together with wood ash, even a decrease of up to 15% in stand growth relative to the control could be seen. On the other hand, most stand parameters showed an increasing tendency when N or ash in combination with N was applied. The treatment with wood ash and N did not significantly affect the total crown biomass. However, an increasing tendency from on average 12.571.9 kg (control) to 14.070.6 kg (wood ash) per tree was determined (Table 4). Compared with the control, an increase of the total crown
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Control 5 t ash /ha
30
Mean content, g per tree
707
180 kgN /ha 25 20 15 10 5 0 Cur.
O ne-yr. N
Cur.
One-yr.
Cur.
P
One-yr. K
Cur.
One-yr. Ca
Cur.
One-yr.
Mg
Fig. 3. Mean content of some nutrients in the current (Cur.) and 1-year-old (One-yr.) needles 3 growing seasons after treatment.
biomass by 23–30% was also found when N and 2.5 t ash plus 180 kg N were applied. Similarly, there was no significant effect of wood ash and N on the average total mass of needles per tree. The highest, though insignificant, positive effect was found when wood ash was applied together with N. The total biomass of the shoots and branches also showed a tendency to increase, comparable to the above-mentioned changes due to the different treatments. The biomass of the shoots and branches increased insignificantly by 9% after the N treatment and by 27% after the application of ash together with N. Wood ash insignificantly affected the mass of the current, 1-year-old and older shoots and branches. The mass of the current year shoots increased from 0.470.1 kg (control) to 0.570.0 kg (wood ash) per tree on average, while that of the 1-year-old shoots was almost unchanged. Even though the total crown biomass did not appear to be significantly influenced by the different treatments, the analyses of the 3 main crown sections gave a slightly different view. The various crown biomass components (current, 1-year-old needles and shoots) increased after the application of wood ash (Fig. 2). However, the only significant effect on the needle mass was determined in the top section of the crown. The biomass of the current year needles and shoots increased by about 20% and that of the 1-year-old needles by 5%, compared with the control. When the 3 crown sections were analysed separately, the mass of the current and 1-year-old needles was significantly higher in the top section on the fertilized plots. It is possible that visible effects of the wood ash on the total crown could occur after some more years, as our study was made after only 3 growing seasons. The results of our experiment were in agreement with earlier studies. In Sweden, there was no wood ash effect after 5 years when 0.3–0.5 t of ash were applied [26], and a similar result was found in Finland after 5–11 years when 3 t of ash [12] or even after 10–15 years when 3.6–10 t of ash were applied [11]. However, when N is the growth-limiting
factor in stands growing on mineral soils [4], addition of other nutrients is unlikely to cause an increase of tree growth. In our experiment, clearer effects on various tree crown biomass indices were obtained after the application of N. Most often, the addition of N is recorded as the only treatment which could give a significant biomass increase [16,27]. In the present study, N, and also ash together with N, applied on a sandy soil gave a significant positive growth response on the active crown biomass. Earlier studies have shown that this combination of fertilizers usually results in a growth increase and that fertilizer treatments containing N have a growth-promoting effect on Scots pine [13,14,17]. It is important to add that for practical operations, wood ash recycling or its combination with other fertilizers, which have often been suggested for nutrient management, may, over time, affect stand growth in different ways [28]. The question still remains whether the combined ash plus N treatment gives extra stand growth under any conditions. Saarsalmi et al. [12] stated that wood ash, as a soilameliorating amendment, might be useful on forested mineral soils as long as it is supplied together with N. Some authors [13,14] also recorded that a combined treatment with different nutrients could give a higher positive response in terms of stand growth on mineral soils. The highest production was obtained after the application of P, K, Mg and micronutrients in Sweden and Norway [13], while in Finland the application of P together with N gave a growth response on more fertile sites [14]. However, other studies have shown that wood ash reduces the response to N fertilization [29] or that there are no differences if N alone or ash together with N is applied in Scots pine stands on poor sites [6]. To explain the above-mentioned disagreements, we statistically tested the changes in the crown biomass components under different treatments. Our results indicate that raw wood ash applied in combination with N
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significantly increased the biomass of only the current and 1-year-old needles and shoots but not of the older components of the pine trees. Despite the non-significant difference between the treatments of N and ash combined with N, the combination effect could be treated as an extra response compared not only to ash but also to N alone. The nutrient content in the needles also appears to be an important factor for the development of the crown biomass. The N treatment resulted in significantly elevated N concentrations in the current year and 1-year-old needles, while wood ash alone had no influence on the N concentration in the needles 3 growing seasons after treatment. The high availability of N in the N treatment seems to have stimulated uptake of Ca in the needles, as did the ash treatment. Still, analyses of the crown nutrient content did not highlight any effect of the treatments and showed no higher nutrient mobilization to the active crown biomass. The results from this study confirm that the effects of wood ash application on needle concentrations in Scots pine are quite small [11,19]. These results suggest that wood ash application should preferably be done together with N fertilization. This treatment might lead to a greater development of crown biomass, and furthermore would regulate stem growth [18]. 5. Conclusions Nitrogen significantly increased the biomass of the current and 1-year-old shoots and needles. No changes were determined in the older parts of the crown. The effect of wood ash was small and in most cases insignificant. The mass of the current and 1-year-old year needles increased only in the top section of the crown. When wood ash was added in combination with nitrogen, an extra response in terms of crown expansion, especially in the top and middle sections of the crown, was found. Forest fertilization with a combination of nutrients would be preferable to the application of wood ash or nitrogen alone. Acknowledgements This study was supported by the project ‘Wood for Energy—A Contribution to the Development of Sustainable Forest Management (WOOD-EN-MAN, QLK5-CT2001-00527)’ under ‘Quality of Life and Management of Living Resources’. We thank the technicians at the Lithuanian Forest Research Institute for their help with biomass sampling in the forest and the laboratory, the referees for valuable comments on the manuscript, and Nicholas Clarke for language corrections. References [1] Bramryd T, Fransman BO. Silvicultural use of wood ashes—effects on the nutrient and heavy metal balance in a pine (Pinus sylvestris L.) forest soil. Water Air and Soil Pollution 1995;85:1039–44.
[2] Ingerslev M. Vitalization of mature Norway spruce stands by fertilization and liming. In: The research series, vol. 23. Hørsholm: Danish Forest and Landscape Research Institute; 1998. 126pp. [3] Swedish recommendations for the extraction of forest fuel and compensatory fertilizing in Sweden. National Board of Forestry/ Skogsstyrelsen, 2002. [4] Tamm CO. Nitrogen in terrestrial ecosystems, questions of productivity, vegetational changes and ecosystem stability. Berlin: Springer; Ecology Studies 81, 1991. [5] Linder S. Foliar analysis for detecting and correcting nutrient imbalances in Norway spruce. Ecological Bulletins (Copenhagen) 1995;44:178–90. [6] Jacobson S. Addition of stabilized wood ashes to Swedish coniferous stands on mineral soils—effects on stem growth and needle nutrient concentrations. Silva Fennica 2003;37:437–50. [7] Pa¨rn H. Effect of wood ash application on radial and height growth of young Scots pines (Pinus sylvestris L.). Forestry Studies/ Metsanduslikud uurimused 2005;42:48–55. [8] Ingerslev M, Hallba¨cken L. Above ground biomass and nutrient distribution in a limed and fertilized Norway spruce (Picea abies L.) plantation. Part II. Accumulation of biomass and nutrients. Forest Ecology and Management 1999;119:21–38. [9] Ma¨kinen H, Uusvaara O. Effects of fertilization on the branchiness and the wood quality of Scots pine. Foliar Forest 1992;801 [in Finnish with an English summary]. [10] Ma¨lko¨nen E, Kukkola M. Effect of long-term fertilization on the biomass production and nutrient status of Scots pine stands. Fertilizer Research 1991;27:113–27. [11] Moilanen M, Issakainen J. Effects of wood ash on forests. Metsa¨tehon raportti 93, 2000. [12] Saarsalmi A, Ma¨lko¨nen E, Kukkola M. Effects of wood ash fertilization on soil chemical properties and stand nutrient status and growth of some coniferous stands in Finland. Scandinavian Journal of Forest Research 2004;19:217–33. [13] Nilsen P, Abrahamsen G. Scots pine and Norway spruce stand responses to annual N, P and Mg fertilization. Forest Ecology and Management 2003;174:221–32. [14] Kukkola M, Sarama¨ki J. Growth response in repeatedly fertilized pine and spruce stands on mineral soils. Communicationes Instituti Forestalis Fenniae 1983;114. [15] Nilsen P. Fertilization experiments on forest mineral soils: a review of the Norwegian results. Scandinavian Journal of Forest Research 2001;16:541–54. [16] Nohrstedt H-O¨. Response of coniferous forest ecosystems on mineral soils to nutrient additions: a review of Swedish experiences. Scandinavian Journal of Forest Research 2001;16:555–73. [17] Vallinger E, Elfving B, Mo¨rling T. Twelve-year response of Scots pine to thinning and nitrogen fertilization. Forest Ecology and Management 2000;134:45–53. [18] Little CHA, Pharis RP. Hormonal control of radial and longitudinal growth in tree stem. In: Gartner BL, editor. Plant stems: physiology and functional morphology. San Diego: Academic Press; 1995. p. 281–319. [19] Vuorinen M, Kurkela T. Lophodermella sulcigena infection in Scots pine needles and tree nutrition. Forestry 2000;73:239–46. [20] Jacobson S. Fertilization to increase and sustain tree growth in coniferous stands in Sweden. Swedish University of Agricultural Sciences. PhD thesis. Silvestria 2001;217:1–34. [21] ISSS-ISRIC-FAO. World reference base for soil resources. World Soil Resources Report 84. Rome: FAO; 1998. [22] Ozolincius R, Varnagiryte I, Armolaitis K, Karltun E. Initial effects of wood ash fertilization on soil, needle and litterfall chemistry in Scots pine stands. Baltic Forestry 2005;11(2):59–67. [23] UN/ ECE. Manual on methods and criteria for harmonized sampling, assessment, monitoring and analysis of the effects of air pollution on forests. Part IV. Sampling and analysis of needles and leaves. Hamburg/Geneva: Programme Coordinating Centre; 2000 (p. 1–37).
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[28] Ingerslev M, Ma¨lko¨nen E, Nilsen P, Nohrstedt HO¨, Oskarsson H, Raulund-Rasmussen K. Main findings and future challenges in forest nutritional research and management in the Nordic countries. Scandinavian Journal of Forest Research 2001;16:488–501. [29] Pettersson F. Kompensationsgo¨dsling efter tra¨ddelsgallring [Complementary fertilization after whole-tree thinning]. Information va¨xtna¨ring-skogsproduktion 2 1990/1991. Uppsala: Institutet fo¨r Skogsfo¨rba¨ttring; 1990. [30] FAO. Guidelines for soil description. Rome: FAO; 1990.