Ozone and drought stress — Interactive effects on the growth and physiology of Norway spruce (Picea abies (L.) Karst.)

Young trees of Norway spruce (Picea abies (L.) Karst.) were grown in 120 litre pots under two different ozone levels in open-top chambers for three seasons, 1992–1994. The ozone treatments were charcoal filtered air (CF, average 24 h seasonal mean 6.5 ppb) and non-filtered air with extra ozone aiming to track 1.5 times ambient (NF+, average seasonal mean 34 ppb). In addition, half of the spruce trees in Aug – Sep each season recieved a drought period of between five and seven weeks. The remaining half were kept well-watered. The soil water content, the needle water potentials, and the gas exchange as well as the chamber micro climate were measured before, during and after the drought period. Furthermore, the growth of the trees was measured as biomass increase. During the 1993 drought period, where the trees experienced a moderate drought stress, the trees grown in NF+ consumed soil water faster and showed a higher needle conductance compared to CF. However, no negative effects were found on needle water potential or growth. During the more severe 1994 drought stress period we did not find any differences between the two ozone treatments in soil water consumption, needle conductance or needle water potential. There was a significant negative effect of the high ozone treatment on tree biomass of the well-watered trees. Total plant biomass was reduced 18 % and stem biomass was reduced as much as 28 %. The negative effect of ozone on tree biomass was much smaller for the droughted trees.     

Variation in Soil Nitrate Concentrations in Two N-Saturated Norway Spruce Forests (Picea abies (L.) Karst.) in Southern Bavaria

Persistently high Nitrogen (N) deposition may have caused widespread N saturation in Central Europe’s forests. Simple and inexpensive methods are required for estimating the N status. This study suggests that the current N status of forest ecosystems can be estimated by measuring CaCl₂-extractable nitrate concentrations in the soil below the main rooting zone. We tested this possibility using a large number of samples (135 in total) in a nested sampling design in two homogeneous Norway spruce forests in southern Bavaria. This approach was accompanied by a small scale survey with suction cups (N = 54) in one forest. Nitrate concentrations determined by soil extracts varied widely (coefficients of variance 95 and 125%) and were well comparable with those of the simultaneous investigation of seepage water. Site and stand conditions explained only a small portion (<10%) of the total variation. Mineral soil nitrate concentrations were not spatially dependent at the medium and large scales (about 10 m to several km) in both forests. Therefore the reliability of estimates at these scales depends mainly on the sample size. At the small scale (<about 10 m) large variation in nitrate concentrations and a considerable spatial dependency could be observed. Therefore intensive sampling is necessary at short distances in order to estimate the mean adequately. From our results, we deduct possibilities and limitations of nitrate inventories as a tool for regional assessment of the N status of forests.     

Aluminium-induced callose formation in root tips of Norway spruce (Picea abies (L.) Karst.)

The objective of this study was to examine whether aluminium (Al) induces callose formation in roots of Norway spruce as it does in soybean. Spruce seedlings were grown in Al-free nutrient solution under controlled conditions in a growth chamber at pH 3.8. After 21 days 170 μM Al was added or not (controls) to the complete nutrient solution (molar Ca/Al ratio: 0.75). Callose could be detected in outer root-tip cells of Al-treated plants within 3 h, using fluorescence microscopy after staining with aniline blue. Prolonged Al treatment up to 24 h increased both the density of the callose deposits and the number of affected cell layers. Control plants showed no comparable callose deposits. Ultrastructural examinations showed cell-wall appositions in Al-treated root cells but not in controls. The possible implications of Al-induced callose formation for nutrient and water uptake by roots are discussed.     

Effects of growing roots of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) on rhizosphere soil solution chemistry

The chemical conditions of the rhizosphere can be very different from that of bulk soil. Up to now, little attention has been given to the problem of spatial heterogeneity and temporal dynamics of rhizosphere soil solution and little is known about the influence of different tree species on rhizosphere chemistry. In the present study, we used micro suction cups to collect soil solution from the rhizosphere of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) seedlings in high spatial resolution and capillary electrophoresis for the determination of major cations and anions. The results indicate, that in a soil with a base saturation of about 20—25% and a pH of 6.5, growing roots of beech and spruce lower the concentrations of nutrient cations and nitrate in the rhizosphere soil solution and decrease significantly the pH. The H⁺ release leads to an enhanced mineral weathering as indicated by an increase of CEC and base saturation and to a mobilization of soluble Al, however, on a very low concentration level. In our experiment rhizosphere effects of spruce have been more pronounced than those of beech, indicating, that with respect to below ground activity young spruce trees have a better competitive power than beech.     

Spatial heterogeneity of soil solution chemistry in a mature Norway spruce (Picea abies (L.) Karst.) stand

The determination of the average soil solution concentrations in forest soils is hindered by the spatial heterogeneity of the soil conditions and the stand structure on all scales. The aim of this paper is to investigate the spatial heterogeneity of the soil solution chemistry within a mature stand of Norway spruce and to evaluate the implication of this heterogeneity for the sampling design for soil solutions. The site is a 140 years old Norway spruce stand of 2.5 ha located in the German Fichtelgebirge at 800 m elevation on granitic, deeply weathered bedrock. At 35 cm soil depth, 59 ceramic suction lysimeters (5 cm length, 2 cm diameter) were installed in a systematic grid of 25 · 25 m and soil solution was sampled at 3 dates in June and July 1994. The solutions were analysed for major cations and anions. Semi-variance of the concentrations at a given date revealed no systematic spatial patterns. The coefficients of variance of the element concentrations were between 36 and 298% with highest values for NH₄ ⁺-N. The implications of the observed heterogeneity for the appropriate number of replicates was investigated by Monte Carlo simulations. As an example, the probability that the measured average concentration of SO₄ ^2?-S is outside a ±10% range (related to the ‘true’ 59 lysimeter average) is about 68% if only 3 replicates would have been used, 41% with 10 replicates and 25% with 20 replicates. Due to the generally large spatial heterogeneity of the soil solution chemistry in forest soils the number of lysimeters used must be carefully adjusted to site conditions and the specific question.     

Nutritional status of declining spruce (Picea abies (L.) Karst.): Effect of soil organic matter turnover rate

Foliar analysis was undertaken in two plots of Picea abies (L.) Karst., located in a watershed of Haute Ardenne, Belgium, in order to estimate the decline of the trees. Apart from a general Mg deficiency, the concentrations of the needles were in the same range as those determined in other European stands. Comparisons between healthy and declining trees within each plot revealed a general pattern of decline similar to that observed elsewhere in Western Europe. This was shown as lower Ca, Mg, Zn concentrations and water content and higher N and P concentrations of the needles collected from declining trees. It is concluded that this decline could be due to N over fertilization by the atmospheric deposition. The difference of decline between the two plots was attributed to the turnover rate of the soil organic layer which was less intensive in the most damaged plot.     

Response of Picea abies (L.) Karst. Provenances to sulphur dioxide and aluminum: A pilot study

Seedlings of six Picea abies provenances were exposed to Al, SO₂ and A1+SO₂ for 12 weeks. A molaric Ca/Al ratio of 0.05 was chosen by using 1.68 mM Al. On the average, concentration of SO₂ was 335 μg m^?3. Shoot and root growth were measured and needle discoloration was scored for different pollution regimes. Plant response to different environmental stresses differed significantly among the provenances used and showed marked provenance x treatment interactions. It is noteworthy that the high intraspecific variation of the traits investigated could cause misleading conclusions in nongenetic studies if inappropriate plant material is employed.     

Long-term development of element budgets in a Norway spruce (Picea abies (L.) Karst.) forest of the German solling area

To evaluate ecosystem response to changing atmospheric deposition, element budgets were established over the period from 1973 to 1991 for a Norway Spruce (Picea abies (L.) Karst.) site. Budgets for Na⁺, Cl^?, Ca²⁺, Mg²⁺, N, S and H⁺ were based on total deposition and seepage water fluxes. The deposition of Ca²⁺, Mg²⁺, particularly, of S and H⁺ decreased with time, while calculated N deposition remained constant at a high level. The decrease in Ca²⁺ deposition led to a reduction of Ca²⁺ fluxes with seepage water. The decrease of Mg²⁺ deposition did not have an effect on the output fluxes of Mg²⁺. The reversibility of soil and seepage water acidification by reduced S deposition was delayed by the release of previously accumulated soil SO ₄ ^2? . The highest NO ₃ ^? fluxes were observed during the period of 1986 to 1988; NO ₃ ^? fluxes in general demonstrated a considerable annual and periodic variation. Total N accumulation in the ecosystem amounted to nearly 590 kg ha^?1 yr^?1 during the observation period. The major sink of N in the spruce site is the aggrading humus layer. The results emphasize the need for measurements over several years to make conclusions regarding the function of ecosystems in response to atmospheric deposition.     

Untersuchungen zum Einfluß des Matrixpotentials im Boden auf Stammdickenänderungen von Fichten (Picea abies (L.) Karst.)

Effects of soil water potential on stem radius changes of Norway spruce (Picea abies (L.) Karst.) The stem radius of 2 mature Norway spruce trees and the soil water potential were continuously measured in situ with dendrometers and tensiometers, respectively. In a period without growth and frost events the stem radius and the soil water potentials correlated closely. A young spruce tree grown under controlled conditions changed its radius in response to the soil water supply likewise. The shrinkage of the stem was reversible, even if the soil was very dry (soil water potential ± ? 1000 hPa). An estimate of the soil water potential seems to be possible even beyond ? 1000 hPa by measurements of stem radius changes.     

Foliar symptoms,ethylene biosynthesis and water use of young Norway spruce (Picea abies (L.) Karst.) exposed to drought and ozone

Four-year old Norway spruce (Picea abies (L.) Karst.) trees were pretreated at low and high water supply, and then placed into a growth chamber containing four compartments so that two levels of ozone exposure, 0.02 and 0.4 Μl l^?1, could be replicated. They were exposed to ozone and drought stress for 59 days, and water use was determined by periodic weighing. Small effects of ozone treatment were detected on new shoot dry weight, and water use by trees receiving the high ozone treatment appeared higher. Both visual symptoms and ethylene biosynthesis showed that drought stress reduced damage to trees exposed to high ozone. Ethylene emission and 1-aminocyclopropane-1-carboxylic acid (ACC) levels increased after 18 days of exposure to 0.4 Μl l^?1 ozone, while visual symptoms were seen at 30 days. After 59 days of exposure to the combined stresses, ethylene and ACC levels were lower, but showed an ozone x water interaction. Most ethylene and ACC were produced by wet trees at high ozone concentration, but dry trees also had high ethylene and ACC levels at low ozone. Levels of needle malonyl-ACC (MACC) were not significantly affected by treatment, and did not change with time, but root MACC levels, which were twice needle levels, were high in wet trees at high ozone concentration, but also high in dry trees at low ozone concentration. These results suggest that drought stress occurring during ozone exposure could be expected to reduce damage to young Norway spruce, and that this damage may be related to ethylene biosynthesis.     

The effect of spruce (Picea abies Karst.) on soil development: an analytical and experimental approach

Changes in soil and biogeochemical processes following the replacement, 60 years ago, of part of a deciduous forest by a coniferous stand were evaluated by (i) a balance-sheet approach using soil and biomass element content analyses and the mineral flux, and (ii) the inclusion of test-mineral and resin bags in an integrative experimental approach. The comparison of soils under different stands shows that the change to spruce is inducing physical, chemical and biological modifications in soil properties. Changes in the humus layers lead to a reduction in mineralization and the mobilization of active organic acids in the system. Under spruce, the soil structural stability is reduced as fine clay is dispersed. Soil acidification is increased, linked to a decrease in soil pH and desaturation of the soil exchange complex. Soil mineralogy also indicates this tendency, particularly with an increase in the stability of Al intergrades. The biogeochemical cycle is modified especially for N, S and Al. with large changes in the internal fluxes between the ecosystem components, but the modification of the input-output balance due to spruce introduction is large only for S. The acidification is partly due to a change in litter quality, which inhibits biological activity, and partly because, during the dormant season, evergreen species intercept ‘dry and occult’ depositions from the atmosphere containing acidic or potentially acidic components. Use of test-mineral bags improves understanding and interpretation of the current soil mechanisms. The test mineral, a vermiculite, introduced into the soil or placed in the lysimeter flux very quickly undergoes measurable transformation characterized by desaturation and fixation of non-exchangeable Al in the interlayer zone, easily identified by Al speciation. The acidifying effect of spruce is clearly demonstrated by the experimental approach used, including the characterization of soil solutions by resin bags. All the techniques are complementary and could be used together or individually, depending on the aim of the study.     

The influence of stand density and canopy position on sulfur content in needles of Norway spruce (Picea abies L. Karst.)

Analysis of total S in tree foliage has become widely accepted as a means of assessing S pollution of forests when air quality data are lacking. An investigation of total S content of mixed needle samples of different age and canopy height from two stands of young Norway spruce with different densities showed that S-content exceeded the maximum natural S-content (i.e. in the absence of SO₂-pollution) for spruce. Significantly higher average needle S contents were encountered with decreasing stand density. Changed aerodynamic roughness and physiological status of thinned trees indicated combined action of atmospheric and tree physiological variables on S deposition and uptake in forest ecosystems. A marked increase in S content from 1 yr old to older needles and from the lower to the upper canopy was observed.     

On the causes of decline of Norway spruce (Picea abies Karst.) in Central Europe

Abstract. A careful study of the etiology and symptoms of the decline phenomena in stands of silver fir ( Abies alba Mill.), Scots pine ( Pinus sylv L.), European beech ( Fagus silv. L.) and Norway spruce ( Picea abies Karst.) in southern Germany leads to the conclusion that all these diseases, although exhibiting some common features (e.g. premature senescence and shedding of leaves, formation of transparent crowns), vary considerably between species and, within one particular species, between forest regions. It therefore seems plausible to assume, as a first approach, that we have to deal with different types of disease or decline, and consequently also with varying sets of causes or stress factors. This approach can be demonstrated best by reviewing the present knowledge of diseases in Norway spruce.     

The effect of lime on microbial activity in spruce (Picea abies L.) forests

Summary The use of lime increased heat output and decreased the C:N ratio (global indicators of biological activity) in the organic horizons of a spruce forest (Picea abies L.) soil. These changes were still present after 18 years. During the same period, the muramic acid content increased slightly, while the concentration of both ergosterol and glucosamine decreases. The ratios of ergosterol or glucosamine to muramic acid decreased significantly after 3 years in the plots that had been irrigated and limed, and after 8 years in the limed non-irrigated plots.     

Bodenanalytische Diagnose von K- und Mg-Mangel in Fichtenbeständen (Picea abies Karst.)

Soil Analytical Diagnosis of K- and Mg-Deficiency in Spruce Stands (Picea abies Karst.) Significant correlations were demonstrated between the amounts of exchangeable K, Mg, Ca and Al in the soil and the corresponding amounts in the needles of 44 spruce stands in southwestern Germany. Strong correlation was also found between the exchangeable Mg in the soil and the degree of yellowing of older needles. The critical levels of nutrient elements in the soil were derived from the respective contents found in the needles. Acute Mg deficiency occurs at a level of 2 μeq/g soil material. For an evaluation of the Mg nutrition of Picea abies soil analysis can replace the needle analysis. For K a similar clear definition of the deficiency range is not possible, though for K contents < 2 μeq/g soil material a deficiency is probable. However, a K deficiency can also occur at higher levels (2–5 μeq/g soil material). The soil analysis can only be regarded as a guideline indicating K deficiencies.     

Chemistry of soil organic matter as related to C : N in Norway spruce forest (Picea abies(L.) Karst.) floors and mineral soils

Due to high nitrogen deposition in central Europe, the C : N ratio of litter and the forest floor has narrowed in the past. This may cause changes in the chemical composition of the soil organic matter. Here we investigate the composition of organic matter in Oh and A horizons of 15 Norway spruce soils with a wide range of C : N ratios. Samples are analyzed with solid‐state ¹³C nuclear magnetic resonance (NMR) spectroscopy, along with chemolytic analyses of lignin, polysaccharides, and amino acid‐N. The data are investigated for functional relationships between C, N contents and C : N ratios by structural analysis. With increasing N content, the concentration of lignin decreases in the Oh horizons, but increases in the A horizons. A negative effect of N on lignin degradation is observed in the mineral soil, but not in the humus layer. In the A horizons non‐phenolic aromatic C compounds accumulate, especially at low N values. At high N levels, N is preferentially incorporated into the amino acid fraction and only to a smaller extent into the non‐hydrolyzable N fraction. High total N concentrations are associated with a higher relative contribution of organic matter of microbial origin.     

Correlating phosphorus extracted by simple soil extraction methods with foliar phosphorus concentrations of Picea abies (L.) H. Karst. and Fagus sylvatica (L.)

Phosphorus (P) concentrations in needles and leaves of forest trees are declining in the last years in Europe. For a sustainable forest management the knowledge of site specific P nutrition/availability in forest soils is vital, but we are lacking verified simple methods for the estimation of plant available P. Within this study, four soil P extraction methods [water ( ), double‐lactate (P_lac), citric acid (P_cit), and sodium bicarbonate ( )], as well as total P content of the soil (P_tot) were tested to investigate which method is best correlated with foliar P concentrations of spruce [Picea abies (L.) H. Karst.] and beech [Fagus sylvatica (L.)]. Mineral soil samples from 5 depth levels of 48 forest sites of the Bavarian sample set of the second National Forest Soil Inventory (BZE II) were stratified according to tree species (spruce and beech) and soil pH (pH < 6.2 and > 6.2), covering the whole range of P nutrition. The extractable amount of P per mass unit of soil increased in the order << P_lac < < P_cit, decreased with soil depth, and was higher in soils with pH < 6.2. Citric acid extracted up to 10% of P_tot in acidic soils. Whereas P_cit delivers adequate regression models for P nutrition in the case of spruce (R² up to 0.53) and beech (R² up to 0.58) for acidic soils, shows good results for spruce growing on acidic soils (R² up to 0.66) and for beech on soils with pH > 6.2 (R² up to 0.57). P_lac produces adequate models only for beech on high pH soils (R² up to 0.64), while did not produce acceptable regression models. P_tot seems suitable to explain the P nutrition status of beech on acidic (R² up to 0.62) and alkaline soils (R² up to 0.61). Highest R²s are obtained mostly in soil depths down to 40 cm. As and P_cit showed good results for both investigated tree species, they should be considered preferentially in future studies.     

Fate of Nitrogen Compounds Deposited to Spruce (Picea Abies Karst.) and Pine (Pinus Silvestris L.) Forests Located in Different Air Pollution and Climatic Conditions

Measurements were made of NO₃-N and NH₄-N in bulk deposition, throughfall and soil solution on six permanent plots in pine and spruce stands located along a transect from the south to the north of Poland. Location differed both in the level of air pollution level and in climatic parameters. The total N load calculated from throughfall ranged from 12.5 to 34 kg^{-1a -1}. The load of NH₄-N exceeded the NO₃-N contribution. Differences in total N load were not reflected in foliar N concentration. Present forest health status of stands determined by defoliation class, and do not appear to be related to their N deposition.     

Effects of acid irrigation and liming in a norway spruce stand (Picea abies [L.] KARST.)

Acid irrigation (pH 2.7 to 2.8; mean annual input 4.1 kmol H⁺ ha^?1 as H₂SO₄) has caused significant changes in the chemistry of the soil of a mature Norway spruce stand (Picea abies [L.] KARST.) after 4 years of treatment. In the surface humus layer around 20% of the exchangeable Ca, Mg, K and Mn ions were leached. This was connected with a decrease of pH and cation exchange capacity. In the mineral soil no changes of pH and cation adsorption were observed. However there was a significant increase of Al³⁺ ions in the soil solution, exceeding 20 mg L^?1, mainly caused by dissolution of Al-hydroxides and Al-hydroxosulphates. Also the concentrations of ionic Cu, Zn and Cd were nearly doubled. Manganese concentrations are fluctuating according to periods with and without acid irrigation, showing reduction and oxidation phases. In contrast to microorganisms, certain moss species and Oxalis acetosella, the mature spruce stand was not severely damaged up to now. It is hypothesized that Ca/Al and Mg/Al ratios of single horizons are insufficient for characterizing Al stress in the field. Liming (4 Mg ha^?1) led to a significant increase of dissolved organic C, which is associated with mobilization of metals such as Pb, Cu and Al in organic complexation. Also nitrification increased in the surface humus layer. As a consequence the nitrate concentrations in the seepage water exceeded 250 mg NO₃ L^?1.