Growth of adult Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) under free-air ozone fumigation

This study attempted to detect the impact of ozone on adult trees of Norway spruce ( Picea abies [L.] Karst.) and European beech ( Fagus sylvatica L.) in an experimental mixed stand in Southern Bavaria, Germany. The aim was to examine whether there is a decrease in growth when trees are exposed to higher than atmospheric concentrations of ozone. This exposure was put into effect using a free-air fumigation system at tree crown level. Growth analysis was carried out on a group of 47 spruce and 36 beech trees, where radial stem increment at breast height - a sensitive index for stress - was measured. The ozone monitoring system allowed values to be obtained for the accumulated ozone exposure (SUM00) of each individual tree, so that their radial increment over three years could be correlated with the corresponding ozone exposure for the same time period. Correlation and regression analysis were then carried out to test the influence of ozone on diameter increment. In both spruce and beech, the initial stem diameter was the most influential factor on radial increment in the following year. A linear model was applied, including the diameter of the preceding year and the ozone exposure of the current year as predicting factors. For spruce trees, a significant negative influence of ozone exposure was found. In contrast, no significant ozone effect on diameter increment of beech was detected. The effect of ozone stress on a large spruce tree can lead to a decrease in potential radial increment of 22 %. The results are discussed in relation to other stress factors such as drought and lack of light.     

Development of biomass proportions in Norway spruce (Picea abies [L.] Karst.)

This study tests the hypotheses that (1) the above-ground structure of Norway spruce (Picea abies [L] Karst.) is derivable from the functional balance theory, and that (2) crown ratio is a key source of structural variation in trees of different age and social position. Twenty-nine trees were measured in three stands (young, middle-aged, and mature), with three thinning treatments (unthinned, normal, and intensive) in the two older stands. There was a strong linear relationship between the total cross-sectional area of branches and that of stem at crown base. Foliage mass was linearly related with stem basal area at crown base. Also an allometric relationship was found between foliage mass and crown length. The mean length (weighted by basal area) of branches obeyed an exponential function of crown length. The parameters of most of these relationships were independent of slenderness (tree height/breast height diameter) and tree age However, total branch cross-sectional area per stem cross-sectional area in the young trees was greater than in the older trees. The young trees also had slightly shorter branches than predicted by the mean branch length equation. This was probably caused by branch senescence which had not yet started in the young stand. The older trees had a relatively long lower crown segment which was growing slowly and senescing. It was proposed that a segmented crown structure is characteristic of shade tolerant tree species, and that the structural model could be further developed by making the two segments explicit.     

Structural variation of tracheids in Norway spruce (Picea abies [L.] Karst.)

The orientation of cellulose microfibrils in the cell wall and the shape and the dimensions of the cells of earlywood of four Norway spruce (Picea abies [L.] Karst.) stems grown in Finland were studied by X-ray diffraction and optical microscopy. The average microfibril angle (MFA) decreased and the diameter of the cell increased rapidly up to rings 5-10 from the pith and remained at the same level after that. The average MFA close to the pith was over 20 degrees and decreased to about 8 degrees after ring 10 from the pith. The average diameter of the cells was 35 microm in the outer rings. The shape of the cross section of the lumen changed from circular to rectangular from the pith to the bark. The tracheid length increased also as a function of the distance from the pith. The thickness of the cell wall varied between 2.8 and 3.5 microm. Automatic cell lumen and cell wall recognition procedures were developed for the analysis of the images of the cross sections of the cells.     

Differentiation among Austrian populations of Norway spruce [Picea abies (L.) Karst.] assayed by mitochondrial DNA markers

Thirty-seven populations of Norway spruce [Picea abies (L.) Karst.] across the Austrian Alps and Bohemian Massif were sampled to elucidate the geographical pattern of genetic differentiation. Three polymorphic mitochondrial DNA (mtDNA) loci were surveyed. Two or three alleles were detected at each locus, resulting in seven multilocus mtDNA haplotypes (A–F). Western populations proved to be monomorphic, whereas eastern and central Austrian populations were slightly to highly polymorphic, respectively. As revealed by spatial analysis of molecular variance and Monmonier’s analysis, the two main haplotypes A and B are not randomly distributed. Haplotype A was restricted to central and eastern Austria, whereas haplotype B occurred in all Austrian populations but was the only haplotype identified in western populations. This pattern may be explained by different glacial refugia located in the Dinaric Alps and the Carpathian mountains.     

The distribution of genetic variation in Norway spruce (Picea abies Karst.) populations in the western Alps

Aim  In order to look for a possible centre of survival for the Norway spruce ( Picea abies Karst.) in the south-western Alps, six natural populations of this area were investigated by means of genetic markers in order to assess the degree and the distribution of genetic diversity within the species.
Location  Western and South-western Alps.
Methods  Populations were genotyped using seven simple sequence repeat (SSR) markers. Basic population genetics parameters were estimated and the amount of genetic differentiation calculated.
Results  A large amount of variability was found (0.59 <  H _e < 0.67); genetic differentiation as measured by F _ST was 0.05, close to other similar studies; no isolation by distance was detected by a Mantel test. Analysis of molecular variance confirmed a high degree of variability within populations and a low degree of variability among populations. Finally, the number of populations from which those observed could have arisen was estimated by Bayesian analysis.
Main conclusions  The results presented here suggest that the present populations derive their genetic make-up from three inferred clusters. The possible existence in this area of a relict/refuge population during the last glaciation is discussed.     

Effects of varied soil nitrogen supply on Norway spruce (Picea abies [L.] Karst.)

During a seven-month period the effect of different nitrogen (N) availability in soil on growth and nutrient uptake was studied in three-year-old Norway spruce (Picea abies [L.] Karst.) trees. The plants were grown in pots on N-poor forest soil supplied with various amounts and forms (inorganic and organic) of N. Increasing supply of inorganic N (as NH₄NO₃) increased the formation of new shoots and shoot dry weight. The root/shoot dry weight ratio of new growth was drastically decreased from 1.6 in plants without N supply to 0.5 in plants supplied with high levels of NH₄NO₃. This decrease in root/shoot dry weight ratio was associated with distinct changes in root morphology in favour of shorter and thicker roots. The addition of keratin as organic N source did neither affect growth nor root morphology of the trees. The amount of N taken up by plants was closely related to the supply of inorganic N, and trees supplied with highest levels of NH₄NO₃ also had the highest N contents in the dry matter of needles and roots. In contrast, N contents in needles of trees grown without additional N, or with keratin supply, were in the deficiency range. Supply of NH₄NO₃ decreased the contents of phosphate (P) and potassium (K) and therefore markedly increased N/P and N/K ratios in the needles. On the other hand, the contents of calcium (Ca), magnesium (Mg), and manganese (Mn) in the needles were increased in the plants supplied with inorganic N, suggesting high soil availability and promotion of uptake of these divalent cations by high nitrate uptake. The observed effects on root/shoot dry weight ratio, root morphology, and mineral nutrient composition of the needles indicated that high inorganic N supply may increase above-ground productivity but at the same time decrease the tolerance of trees against soil-borne (e.g. deficiency of other mineral nutrients) stress factors. Deceased 21 September 1996 Deceased 21 September 1996     

Vertical distribution of an ectomycorrhizal community in upper soil horizons of a young Norway spruce (Picea abies [L.] Karst.) stand of the Bavarian Limestone Alps

The vertical niche differentiation of genera of ectomycorrhiza (ECM) was assessed in a 17-year-old Norway spruce (Picea abies [L.] Karst.) plantation on a mountainous dolomitic site (1,050 m above sea level) of the Bavarian Limestone Alps. We determined ECM anatomotypes, recorded the abundance of corresponding ECM root tips and classified them into groups of ECM exploration types, which refer to the organisation and the extent of their extramatrical mycelia. The abundance of ECM was highest in the organic soil layers, compared to the mineral soil horizon. The ordination of the ECM communities and of the exploration types revealed segregation related to soil horizon properties. While Cenococcum geophilum preferred the organic soil layers, Lactarius spp., Tomentella spp. and Craterellus tubaeformis were generally most abundant in the mineral soil horizons. Cenococcum geophilum was the predominant species, possibly based on enhanced competitiveness under the prevailing site conditions. The short-distance exploration types (e.g. C. geophilum) preferentially colonised the organic soil layer, whereas the contact types (e.g. most of the Tomentella spp., C. tubaeformis) together with medium-distance types (e.g. Amphinema byssoides) were primarily associated with the underlying A-horizons. Therefore, the soil horizons had an important effect on the distribution of ECM and on their community structure. The spatial niche differentiation of ECM genera and exploration types is discussed in regard to specific physico-chemical properties of soil horizon and the assumed ecophysiological strategies of ECM.     

Effects of climate on vertical resin duct density and radial growth of Norway spruce [Picea abies (L.) Karst.]

 Vertical resin duct density in spruce tree-rings was used as a dendroclimatological variable and compared with radial growth. Resin duct density data were statistically stable and distributed with higher mean sensitivity and standard deviation but lower signal-to-noise rate than the corresponding growth rate. Radial growth and resin duct density relationships with climate were investigated using correlation and response function analysis. It was found that resin duct density has a significant positive response to above-normal temperature especially from June to August and a less significant negative response for above-normal precipitation from May – July during the current growing season. Ring width showed a significant negative response to above-normal precipitation from June to August but no response with temperature. Ring width and resin duct density were not related to each other. Sufficient data indicate that vertical resin duct density is a useful variable for dendroclimatology. Received: 14 March 1996 / Accepted: 24 June 1996     

Activities of enzymes of starch metabolism in developing Norway spruce [Picea abies (L.) Karst.] needles

 Development of spruce needles starts with high levels of starch. These are derived from imported sucrose, and, with some fluctuation, largely vanish during sink/source transition (Hampp et al. 1994, Physiol Plant 90: 299 – 306). In order to get more information about starch metabolism during this period, we collected current year needles of approximately 25-year-old Norway spruce trees [Picea abies (L.) Karst.] for up to 100 days starting from bud break. Levels of extractable activities of α-amylase (EC 3.2.1.1), ADP-glucose pyrophosphorylase (AGP, EC 2.7.7.27), D-enzyme (4-α-D-glucotransferase; EC 2.4.1.25), and of starch phosphorylase (STP, EC 2.4.1.1.) exhibited specific development-related responses. Insoluble starch dissolving α-amylase was close to the limit of detection for up to 70 days after bud break. At this stage, which marked the start of sink/source transition, α-amylase showed a rise in activity which could be related to the activity of sucrose phosphate synthase, a key enzyme of sucrose formation (correlation coefficient r = + 0.93). Similarly, the activity of AGP, a key enzyme of starch synthesis, was low during the initial phase of needle development and started to increase from about 60 days onwards. STP and D-enzyme, both involved in starch cycling, differed from each other. While STP activity changed in parallel to that of AGP, it was only the D-enzyme which showed appreciable rates shortly after bud break. We thus assume that in spruce needles D-enzyme is mainly responsible for starch turnover during the early period of development, whereas needle maturation, i. e. the acquisition of the ability to export photoassimilates, is characterized by an increased turnover of transitory starch – both synthesis (AGP) and degradation (α-amylase, STP) – and this is closely connected to the emergence of activity of the key enzyme of sucrose synthesis, sucrose phosphate synthase. Received: 16 October 1995 / Accepted: 20 February 1996     

Osmotic potential of Norway spruce [Picea abies (L.) Karst.] secondary phloem in relation to anatomy

Variations in water status of secondary phloem of Picea abies (L.) Karst., caused by (1) radial and (2) vertical differences within the tree, (3) seasonal influences, and (4) tree class, and their relation to bark anatomy were investigated. The water status parameters measured were the osmotic potential at full saturation [O_{o (sat)}], the in situ osmotic potential [O_{o (in situ)}], the in situ water content (C_{in situ}), and the in situ relative water content (R_{in situ}). O_{o (sat)} reached most negative values in the conducting part of the secondary phloem, whereas O_{o (in situ)} was similar in conducting (P_C) and non-conducting secondary phloem (P_N). The remarkable discontinuity in the radial course of C_{in situ} and O_{o (sat)} at the transition from P_C to P_N can be attributed to the degeneration of sieve cells and Strasburger cells. In P_C, the vertical decrease of O_{o (sat)} towards the crown was compensated by an increase in R_{in situ}, so that O_{o (in situ)} did not change along the stem. With stem height, O_{o (sat)} decreased and P_C width increased. The determining factor for vertical gradients in O_{o (sat)} was the distance to the sources; similar gradients were also measured in P_N. Seasonal differences in O_{o (sat)} could only be detected in P_C, where they corresponded exactly to changes of O_{o (sat)} in needles. Suppressed trees showed less negative O_{o (sat)} values in P_C, smaller annual secondary phloem increments and smaller radial lumen diameter of living sieve cells than predominant or dominant trees.     

Seasonal development of the photosynthetic performance of Norway spruce (Picea abies [L.] Karst.) under magnesium deficiency

In order to investigate the influence of different magnesium nutrition on photosynthesis, one hundred 6-year-old spruce trees derived from one clone were planted in October 1990 into a special out-door experimental construction, where they were cultivated in sand culture with an optimal supply of nutrients, except magnesium, via circulating nutrient solutions. Magnesium was added to the nutrient solutions in three different concentrations, varying from optimal to severe deficient supplies. During the first vegetative period in 1991, photosynthetic performance and carboxylation efficiency were measured under saturating light, controlled CO₂ conditions, optimal temperature and humidity, using a minicuvette system.During summer, the trees under moderate magnesium deficiency developed tip yellowing symptoms on older needles, while the youngest needles remained green with unchanged chlorophyll contents. Trees under severe magnesium deficiency showed yellowing symptoms on all needle age classes combined with decreased chlorophyll contents in the youngest needles as well. In comparison with the controls, the photosynthetic performance of the 1-year-old needles was significantly lower in both deficiency treatments. The same was observed in the youngest needles of the trees under severe deficiency. Trees under moderate deficiency treatment decreased in photosynthetic performance during the summer without reduction of chlorophyll contents. The reduction of photosynthetic rates corresponded to a decrease in carboxylation efficiency, which is taken as a measure of the activity of the enzyme ribulose-1,5-bisphosphate carboxylase. This reduction, together with the observed increase of carbohydrate contents in needles of trees growing under magnesium deficiency, led to the assumption that the photosynthetic carbonfixation is reduced as a consequence of the accumulation of carbohydrates.     

Influence of cultivation method on root grafting in Norway spruce (Picea abies (L.) Karst.)

Root grafting is the process by which a functional union of two or more roots subsequent to their formation is formed. The above- and below-ground parts of three Norway spruce stands (natural stand, Umbric Luvisol; row-culture and group-culture, Planosol; stand ages 40, 43 and 43, respectively) of high site quality (I) were investigated. Stand densities were 1550, 1783 and 1722 stems ha^-1, respectively. In all investigated stands, root grafting was most sensitive to tree spacing. Grafts were observed in case the distance between the trees was 0.7–1.2 m. Grafts occurred always in areas of higher rooting density, in a row of the row-culture and within a tree group in the group-culture. Root grafting was enhanced in case of a narrower humus horizon in the group culture compared with the row-culture, 16.5 and 30 cm, respectively; the humus horizon contained 99% and 95% of conducting roots with d ≥ 5 mm, respectively. Root graftings occurred in 75% of excavated trees in the group-culture, in 37.5% of excavated trees in the row-culture and in 33.3% of excavated trees in the natural stand. Stand age was 24 years in the row-culture and 22 years in the group-culture at the beginning of root grafting. No grafts occurred between two suppressed trees, whereas in 86–100% of all cases, at least one tree was dominant or codominant. In row- and group-cultivated Norway spruce stands, the initial minimum diameter of the grafted root without bark was from 1 to 3 cm in 63% of cases. Grafting of roots with d < 1 cm or d > 10 cm was rare or absent. Root grafting had usually begun at the root age of 10–20 years (46% of cases). This revised version was published online in June 2006 with corrections to the Cover Date.     

The role of soil conditions in fine root ecomorphology in Norway spruce (Picea abies (L.) Karst.)

The present study is an attempt to investigate the pattern of morphological variability of the short roots of Norway spruce (Picea abies (L.) Karst.) growing in different soils. Five root parameters – diameter, length and dry weight of the root tip, root density (dry weight per water-saturated volume) and specific root area (absorbing area of dry weight unit) were studied with respect to 11 soil characteristics using CANOCO RDA analysis. The investigation was conducted in seven study areas in Estonia differing in site quality class and soil type. Ten root samples per study area were collected randomly from the forest floor and from the 20 cm soil surface layer. Eleven soil parameters were included in the study: humus content, specific soil surface area, field capacity, soil bulk density, pH (KCl and H₂O dilution's), N and Ca concentrations, Ca/Al and C/N ratios, and the decomposition rate of fine roots (<2 mm dia.). Root morphological characteristics most strongly related to the measured soil characteristics in the different sites were specific root area, root density and diameter of the short roots, the means varying from 29 to 42 m² kg⁻¹, from 310 to 540 kg m⁻³ and from 0.26 to 0.32 mm, respectively; root density being most sensitive. The most favourable site and soil types resulting in fine roots with morphological characteristics for optimizing nutrient uptake (e.g. low short root density and high specific root area) were Umbric Luvisol (Oxalis), Dystric Gleysol (Oxalis) and Gleyic Luvisol (Hepatica). These soil types correspond to highly productive natural forest stands of Norway spruce in Estonia. All measured soil variables explained 28% of total variance of the root characteristics. The most important variables related to root morphology were the humus content, field capacity and specific soil surface area. This revised version was published online in June 2006 with corrections to the Cover Date.     

Liming induced stimulation of the amino acid metabolism in mycorrhizal roots of Norway spruce (Picea abies [L.] Karst.)

Localization and activity of three enzymes involved in the amino acid metabolism of ectomycorrhizas were investigated within an interdisciplinary experiment performed in a mature Norway spruce stand in Southern Germany (Höglwald). The enzymes NAD-glutamate dehydrogenase and aspartate aminotransferase were present in root cells, whereas aminopeptidase was found in mycorrhizas of Norway spruce such as Piceirhiza nigra and those with the fungi Cenococcum geophilum, Elaphomyces sp., Russula ochroleuca and Tylospora sp. Mycorrhizas growing in the humus layer contained about double the amount of protein found in those taken from the upper mineral soil (0–5 cm).Acid irrigation of the soil had no effect on the activity of any of the investigated enzymes, soluble protein or total N-contents irrespective of whether roots were taken from the organic layer or from the upper mineral soil. Liming, however, stimulated the activity of the three enzymes in mycorrhizas of the organic layer (O_f+O_h) whereas it had no effect on the activity of the investigated enzymes of mycorrhizas in the upper mineral soil. This effect is attributed to increased contents of soluble organic nitrogen compounds in the soil of the limed plots as compared to the unlimed plots.