Norway spruce is often considered to have a negative impact on a site, yet it is native to many mountain regions of Europe. The relative influence of Norway spruce on site properties has frequently been compared with that of both broadleaved and other coniferous tree species. In our study, growth, as well as needle, forest floor, and topsoil chemistry were compared between Norway spruce and introduced spruce species (white, black, red, Serbian, Sitka, and blue spruce), all growing on the same, formerly polluted mountain site. There were few differences in needle nutrient status between the introduced spruce species and native Norway spruce. The chemistry of forest floor horizons beneath some of the non-native species showed less acidity and better conditions of the soil sorption complex. There were no significant differences in the nutrient pools, indicating that the influence of the various spruce species on the site was comparable. Given the small differences observed in the various nutritional characteristics, it appears that, under the conditions of the study site, the alternative spruces had substituted for the role of Norway spruce before its recovery in the 2000s. The six spruces grew quite consistently during 2001-2012, while the mean height of Norway spruce shifted from the lowest 176 cm (2001) to one of the tallest. At 710 cm (2012), its height had become comparable with that of Sitka. The poorest performing were black spruce (due to bark beetle attack) and blue spruce (due to bud blight infestation and decline).
Severe air pollution in the second half of the 20th century had substantial impacts upon forest health across most mountain ranges of Central Europe, but particularly in the Ore Mountains (Krušné hory), which comprise the frontier range between the Czech Republic and Germany, and in the Jizera Mountains (Jizerské hory) straddling the Czech and Polish borders (
Specific needs, properties, and growth rates of tree species affect the utilization of nutrients available at a site in different ways even as their litterfall retroactively influences nutrient cycles (
The objective of our study was to compare the performance of a range of spruce species, the chemistry of their needles, and the properties of the forest floor (including topsoil) under young stands growing on a formerly air-polluted site in the Czech Republic. Excepting growth, no major difference between the introduced spruce species (white, black, red, Serbian, Sitka, and blue spruce) and the native Norway spruce were expected.
The evaluated forest stands are situated within the Jizerka research plot (see
The experimental plantings consist of five North American spruce species and two of European origin. The treatments of white spruce (
Pm gradually declined and was attacked by bark beetles in 2010. Since 2009, Pp has been infested by bud blight disease (
Each year (but with a two-year interval at the end of the experiment) the height (h, in cm) of individual trees was measured within the experimental stands and the occurrence of stem deformation or other damage was evaluated in autumn. The height growth of individual tree species was assessed in this study until 2012, when these stands were thinned. Diameter at breast height (DBH, in cm) and h/DBH (slenderness) ratio also were evaluated. The evaluation was made using data for 20% of the tallest trees from the actual number on each plot because they constitute the most dominant, vigorous trees.
In November 2011, samples of current-year needles and one-year-old needles were taken for each spruce species. Needles were not sampled for black spruce due to decay of its stand in 2010. In five trees performing well on a plot, two branches were taken from the upper part of the crown. In the laboratory, a composite sample was produced for the individual needle age classes per parcel. For each spruce species, three composite samples were taken (
For each needle sample, the contents of basic nutrients (N, P, K, Ca, Mg, and S) and of silicon were analysed using methods described by
In autumn 2013, topsoil samples were taken using a sampling frame of internal size 25 × 25 cm below the closed canopies of Pa, Pg, Pr, and Ps stands, and in 2015 the topsoil was analysed also in Pp and Po stands. L+F and F+H horizons were separated and their total dry weight was determined. The A horizon also was separated. Each tree species was represented by three plots with three replications of samplings in each parcel (
Analysed parameters included oxidizable carbon (Cox), nitrogen according to Kjeldahl, acidity (pH/H2O and pH/KCl), sorption complex characteristics (base cation content - BCC, cation exchange capacity - CEC, base saturation - BS) and nutrient contents by the Mehlich III method (
Based upon exploratory data analysis (EDA), data consistency was first assessed. Some nutrient ratios (N/P, N/K, N/Ca, K/Mg, Ca/Mg), describing nutrient balance were computed for macroelements in the needles. Using dry weight and nutrient ratios, nutrient pools in soil were computed for the L+F and F+H horizons.
The data set from the analysis of particular needle age classes and soil horizons was evaluated by principal component analysis (PCA) using the FactoMineR package (
Using Student’s
In the first ten years after planting, the mean height growth rate of the tallest 20% of Pa individuals was slower compared to those of the other spruces. In the following period up to 2012, however, its increment increased so as to catch up with the growth of the Ps, which was the tallest treatment after 20 years (height of 7.1 m in 2012 -
In 2012, both Pa and Ps were significantly taller than the other spruce species while Pa had significantly greater DBH compared to Pg, Pr, and Pp. The 2012 slenderness ratio was similar among the species, with the exception that Pp showed a significantly lower h/DBH ratio compared to Pa (
Deep snow cover in the 2004-2005 and 2005-2006 winter seasons (more than 200 cm at some places) caused trunk and top breaks of Pr and Pm trees (42% and 40% of individuals, respectively) while the break frequency in Pa (24%) was close to the overall average.
In current-year needles, the first two axes of PCA explained 66.9% of data variance. The distribution of samples in multivariate space was indicated by differences in the chemistry of Pa needles, especially in comparison to Pr and Po, and great data variance in Pg and Ps (
Statistical comparison of the parameters corresponded with the multivariate analysis. There was a trend for higher average content of N, P, and Ca in Pa needles compared to needles of the other spruces, but the differences were rarely significant. In the case of nitrogen, there was a significantly greater content in Pa compared to Po in current-year needles and to Pr in both needle age classes. Higher phosphorus in Pa needles was significant only in current-year needles in comparison with Po and Ps. Calcium was also significantly higher in both needle age classes of Pa compared to Pr and in current-year needles in comparison with Ps (
Potassium contents in individual spruce species were more differentiated, with significantly lower content found in current-year needles of Pg and Pp compared to Pa. Magnesium was significantly lower only in one-year-old needles of Pp.
Sulphur contents in needles of all introduced species were similar to the values in Pa. The largest differences were measured in silicon content, which was significantly lower in the non-native spruce species compared to Pa in both needle age classes (except the current-year needles in the case of Pg -
The N/P ratio in Pa was among the lowest, but with the exception of current-year needles of Ps these differences were not significant (
Dry matter of the L+F horizon in individual spruce species accounted on average for 8.5% (in Po) to 30.3% (in Ps) of the total dry matter of forest floor (L+F+H). Mean total dry weight of forest floor layers in stands of the analysed species ranged from 12.4 to 14.3 kg m-2, without significant differences between Pa and the other spruce species. The greatest variation in values was observed under Pa (
The PCA multivariate comparison of particular horizons data provided no interpretable outputs in spite of the relatively high probability of data variance explained (the first two axes explained 60.1-65.7% of the variance).
The soil pH values for all horizons were very strongly acid (according to
Among the sorption complex characteristics, a significantly higher value of CEC-BCC difference was revealed in the L+F horizon in Pa compared to Pg, Po, and Pp; in the F+H horizon, it was also higher than in Ps. In the soil under Pa within the L+F horizon, the CEC value was significantly higher than for Po and in F+H higher than for Pg and Ps.
With the exception of significantly higher P content in the A horizon under Pp, no other significant differences in element contents in soil horizons were found between Pa and the introduced spruce species (Tab. S1 in Supplementary material).
Even though there was great variability in the forest floor nutrient pools (kg ha-1) under stands of individual spruce species, few statistically significant differences were apparent (
Norway spruce was the slowest growing among all the spruce species tested during 1990-2001. Its growth rate then accelerated and the height was found to be comparable with that of Sitka spruce, which performed well from the very beginning. The improvement in the growth parameters of Norway spruce reflected the diminishing stress from air pollution (
Winter necrotic injury of needles observed in most spruce species was associated with periods of extremely low temperature, and this has been reported also in other regions. For example, winter injury of red spruce needles is well known from its natural distribution range (
A massive decline of black spruce was recorded due to an attack in summer 2010 by bark beetles, in particular by pine bark beetle (
Nutrient contents in Norway spruce needles indicated a sufficient nitrogen reserve (
A part of the forest floor whose properties can be directly influenced by tree species is the upper, least decomposed layer of litter and detritus (L+F). In our study, the smallest amount of L+F material was found under Serbian spruce. At deeper layers (F+H), however, no differences in the amount of forest floor were observed between the non-native spruces and Norway spruce. The accumulation of this material through litterfall substantially influences the total pool of nutrients in forest floor (
The comparison of performance, foliar nutrient content, and forest floor under 20-year-old spruce stands on the formerly air-polluted mountain site revealed only minor differences between native Norway spruce (Pa) and the introduced spruces. As regards height growth, in spite of initial differences, the performance of Pa was improving over time relative to those of Pp, Pr, Pg, and Po, while Ps performed well throughout the entire period of interest. Pm (due to bark beetle attack) and Pp (due to growth rate and bud blight decline) performed the worst of all. The differences in foliar nutrient concentrations between Pa and other spruce species were negligible, although mostly lower concentrations in the introduced spruces were indicated. Chemistry of the upper soil horizons under Pa and other spruces was similar. There were no significant differences in the forest floor nutrient pools, thus indicating the comparable impact of Pa and other spruces on the site. There has been an obvious recovery in the growth of native Pa compared to the non-native spruces with the exception of Ps. This indicates that it is no longer necessary to plant non-native tree species as replacements for Norway spruce. Further research could determine whether Sitka spruce, which is native to an oceanic climate, can perform comparably with Norway spruce on a montane site in central Europe’s improved pollution conditions.
This study was supported by the Ministry of Agriculture of the Czech Republic within MZE-RO0118 institutional support and research project QJ1520291. The authors would like to thank three anonymous reviewers for valuable comments on an earlier version of the manuscript and also Gale A. Kirking (English Editorial Services) for editing the language.
Location of the Jizerka research plot in the Jizera Mountains (source: Google Maps™).
Mean height growth of the tree species within analysed stands (20% of the tallest trees for each species) over the period 1990-2012. The years 2008-2009 were measured retrospectively. Relevant data are no longer available for Pm due to forest stand damage. (Pa):
Ordination diagram from principal component analysis of macroelement contents in current-year (a) and one-year-old (b) needles. Percentage expresses variance explained by the two axes. (Pa):
Cumulative mortality during 1990-2012, as well as height (h), DBH, and slenderness ratios (h/d) of individual tree species in 2012. Asterisks indicate significant differences between Norway spruce (first row) and the respective non-native spruce species (
Species | Mortality (%) | h (cm) | DBH (cm) | h/d | ||||
---|---|---|---|---|---|---|---|---|
mean | SD | mean | SD | mean | SD | mean | SD | |
Pa | 27.5 | 13.5 | 709.5 | 64.2 | 12.9 | 2.6 | 56.7 | 10.3 |
Pg | 25.5 | 9.0 | 590.4** | 48.3 | 10.4** | 1.7 | 57.9 | 7.0 |
Pr | 29.3 | 15.4 | 541.4** | 46.4 | 9.8** | 2.0 | 57.2 | 11.7 |
Po | 29.0 | 3.0 | 615.0** | 36.0 | 11.4 | 2.1 | 55.7 | 9.5 |
Pp | 41.0 | 12.0 | 465.4** | 52.4 | 10.4** | 1.6 | 45.2** | 5.4 |
Ps | 22.0 | 2.0 | 714.1 | 66.5 | 11.9 | 2.2 | 61.6 | 9.8 |
Percentage content of macroelements and silicon (mean and standard deviation, SD) in current-year (cy) and one-year-old (oy) needles of tested spruce species. Asterisks indicate significant differences in nutrient contents within needle age classes between Norway spruce and the respective non-native spruce species (
Species | Needle age class | N | P | K | Ca | Mg | S | Si | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
mean | SD | mean | SD | mean | SD | mean | SD | mean | SD | mean | SD | mean | SD | ||
Pa | cy | 1.38 | 0.10 | 0.086 | 0.010 | 0.54 | 0.02 | 0.47 | 0.00 | 0.106 | 0.011 | 0.157 | 0.023 | 0.27 | 0.03 |
oy | 1.45 | 0.22 | 0.082 | 0.015 | 0.55 | 0.09 | 0.77 | 0.04 | 0.097 | 0.009 | 0.169 | 0.015 | 0.49 | 0.03 | |
Pg | cy | 1.28 | 0.17 | 0.070 | 0.010 | 0.39* | 0.05 | 0.54 | 0.16 | 0.106 | 0.018 | 0.151 | 0.017 | 0.19 | 0.02 |
oy | 1.32 | 0.29 | 0.061 | 0.008 | 0.64 | 0.13 | 0.60 | 0.17 | 0.138 | 0.052 | 0.139 | 0.003 | 0.31** | 0.03 | |
Pr | cy | 1.05* | 0.07 | 0.063 | 0.001 | 0.59 | 0.04 | 0.28** | 0.02 | 0.084 | 0.002 | 0.160 | 0.013 | 0.12** | 0.01 |
oy | 1.08* | 0.08 | 0.062 | 0.010 | 0.60 | 0.07 | 0.42* | 0.04 | 0.091 | 0.013 | 0.150 | 0.015 | 0.16** | 0.03 | |
Po | cy | 1.08* | 0.05 | 0.058* | 0.003 | 0.59 | 0.06 | 0.36 | 0.05 | 0.089 | 0.006 | 0.151 | 0.006 | 0.08* | 0.05 |
oy | 1.26 | 0.11 | 0.058 | 0.006 | 0.52 | 0.10 | 0.47 | 0.19 | 0.087 | 0.009 | 0.163 | 0.012 | 0.13** | 0.08 | |
Pp | cy | 1.24 | 0.06 | 0.079 | 0.004 | 0.46* | 0.02 | 0.37 | 0.04 | 0.094 | 0.007 | 0.142 | 0.011 | 0.18* | 0.03 |
oy | 1.21* | 0.02 | 0.071 | 0.011 | 0.42 | 0.03 | 0.56 | 0.19 | 0.069* | 0.010 | 0.157 | 0.003 | 0.34** | 0.03 | |
Ps | cy | 1.22 | 0.11 | 0.059* | 0.009 | 0.64 | 0.12 | 0.38* | 0.03 | 0.107 | 0.015 | 0.155 | 0.016 | 0.16* | 0.03 |
oy | 1.20 | 0.09 | 0.052 | 0.018 | 0.54 | 0.09 | 0.67 | 0.09 | 0.090 | 0.007 | 0.149 | 0.017 | 0.23** | 0.03 |
Nutrient ratios (mean and standard deviation, SD) in current-year (cy) and one-year-old (oy) needles of tested spruce species. Asterisks indicate significant differences in nutrient ratios within needle age classes between Norway spruce and the respective non-native spruce species (
Species | Needleage class | N/P | N/K | N/Ca | K/Mg | Ca/Mg | |||||
---|---|---|---|---|---|---|---|---|---|---|---|
mean | SD | mean | SD | mean | SD | mean | SD | mean | SD | ||
Pa | cy | 16.1 | 0.7 | 2.6 | 0.2 | 2.9 | 0.2 | 5.1 | 0.7 | 4.5 | 0.5 |
oy | 18.0 | 2.5 | 2.7 | 0.4 | 1.9 | 0.2 | 5.7 | 1.4 | 7.9 | 0.7 | |
Pg | cy | 18.4 | 1.2 | 3.3 | 0.5 | 2.7 | 1.1 | 3.8 | 0.3 | 5.2 | 1.3 |
oy | 21.6 | 4.1 | 2.1 | 0.3 | 2.2 | 0.2 | 4.9 | 1.0 | 4.5** | 0.3 | |
Pr | cy | 16.6 | 1.0 | 1.8* | 0.3 | 3.8 | 0.5 | 7.1* | 0.4 | 3.3* | 0.1 |
oy | 17.8 | 2.7 | 1.8 | 0.3 | 2.6 | 0.4 | 6.8 | 1.8 | 4.8* | 1.2 | |
Po | cy | 18.8 | 1.7 | 1.8** | 0.2 | 3.1 | 0.6 | 6.6* | 0.3 | 4.0 | 0.6 |
oy | 22.2 | 4.0 | 2.5 | 0.4 | 3.1 | 1.2 | 6.0 | 0.8 | 5.6 | 2.6 | |
Pp | cy | 15.7 | 1.0 | 2.7 | 0.2 | 3.3 | 0.4 | 4.9 | 0.5 | 4.0 | 0.1 |
oy | 17.5 | 2.8 | 2.9 | 0.2 | 2.6 | 1.2 | 6.2 | 0.9 | 7.9 | 2.3 | |
Ps | cy | 21.1* | 2.7 | 1.9 | 0.3 | 3.2 | 0.4 | 6.0 | 0.7 | 3.6* | 0.3 |
oy | 26.5 | 9.9 | 2.3 | 0.4 | 1.8 | 0.2 | 6.0 | 0.7 | 7.5 | 0.8 |
Dry weight (mean and standard deviation, SD) of forest floor horizons (L+F, F+H, and in total). Differences between Pa and other spruce species were not significant. (Pa):
Horizon | Pa (kg m-2) | Pg (kg m-2) | Pr (kg m-2) | Po (kg m-2) | Pp (kg m-2) | Ps (kg m-2) | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
mean | SD | mean | SD | mean | SD | mean | SD | mean | SD | mean | SD | |
L+F | 3.12 | 1.45 | 3.30 | 1.32 | 3.63 | 1.57 | 1.14 | 0.45 | 2.07 | 1.59 | 4.21 | 0.74 |
F+H | 11.15 | 5.18 | 9.40 | 3.89 | 8.72 | 5.13 | 12.29 | 2.84 | 10.85 | 3.17 | 9.68 | 3.51 |
Total | 14.26 | 4.50 | 12.70 | 2.97 | 12.35 | 3.76 | 13.43 | 2.58 | 12.91 | 4.00 | 13.89 | 3.20 |
Nutrient pools (mean and standard deviation, SD) in L+F and F+H horizons. Asterisks indicate significant differences between Pa and particular non-native spruce species (
Horizons | Stand | Cox (kg ha-1) | N (kg ha-1) | P (kg ha-1) | K (kg ha-1) | Ca (kg ha-1) | Mg (kg ha-1) | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
mean | SD | mean | SD | mean | SD | mean | SD | mean | SD | mean | SD | ||
L+F | Pa | 1269.2 | 507.4 | 53.3 | 18.1 | 0.21 | 0.04 | 2.81 | 0.72 | 6.61 | 2.24 | 1.54 | 0.73 |
Pg | 1227.6 | 482.7 | 50.6 | 22.3 | 0.17 | 0.06 | 1.83 | 0.61 | 6.08 | 2.36 | 1.68 | 1.35 | |
Pr | 1343.3 | 571.2 | 55.3 | 24.5 | 0.18 | 0.08 | 2.15 | 1.28 | 6.52 | 3.17 | 1.79 | 1.17 | |
Po | 519.7 | 197.2 | 21.2 | 8.7 | 0.08* | 0.04 | 0.74* | 0.28 | 3.19 | 2.01 | 0.48 | 0.14 | |
Pp | 860.3 | 716.4 | 45.8 | 51.2 | 0.15 | 0.15 | 1.87 | 1.56 | 6.38 | 5.43 | 1.39 | 1.26 | |
Ps | 1781.4 | 518.5 | 63.4 | 11.7 | 0.22 | 0.05 | 3.00 | 1.31 | 9.41 | 1.96 | 2.34 | 0.37 | |
F+H | Pa | 3603.4 | 2022.8 | 149.1 | 89.3 | 0.41 | 0.25 | 4.27 | 2.15 | 17.37 | 10.46 | 5.55 | 4.57 |
Pg | 2914.5 | 1363.4 | 132.8 | 66.2 | 0.32 | 0.21 | 3.10 | 1.70 | 12.25 | 6.26 | 3.48 | 1.38 | |
Pr | 2683.9 | 1943.6 | 120.7 | 84.0 | 0.25 | 0.19 | 2.65 | 1.72 | 14.47 | 10.19 | 4.63 | 3.64 | |
Po | 3878.9 | 977.5 | 182.5 | 34.0 | 0.36 | 0.18 | 4.30 | 0.88 | 20.31 | 5.34 | 6.42 | 2.08 | |
Pp | 3198.1 | 928.5 | 165.7 | 39.1 | 0.47 | 0.26 | 4.02 | 1.58 | 18.25 | 4.55 | 5.63 | 2.07 | |
Ps | 2120.4 | 976.2 | 86.4 | 44.8 | 0.17 | 0.04 | 2.13 | 0.74 | 11.85 | 5.08 | 3.58 | 2.21 |
Tab. S1 - Properties of forest floor and soil horizons (mean and standard deviation).