Effect of deicing chloride salts on ion accumulation in spruce (Picea abies (L.) sp.)

Among the inorganic chloride salts, NaCl, CaCl₂ and in a minor proportion KCl and MgCl₂ are used as deicing agents. Mixturs of these salts were merely applied with respect to their physico-chemical properties, but their effect on roadside vegetation has never been studied so far. From a screening of different salt mixtures on ion accumulation in needles and twigs of spruce tress (Picea abies sp.) it was shown that the presence of a small amount of calcium in the salt treatments had some beneficial effects on ion regulation. In the presence of calcium, sodium accumulation could be reduced. But more straightforward was its effect on the selectivity between sodium and potasium in favour of the latter. Chloride concentrations did not alter very much; their role in the presence of monovalent cations is nevertheless obvious and is discussed. The study also confirms the presence of potassium retranslocation in conifer trees. The ion characteristics are briefly discussed with respect to the ecological effects of chloride salts on tress.     

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.     

Effect of nitrogen on drought strain and nutrient uptake in Norway spruce Picea abies (L.) Karst.) trees

A field lysimeter study was established with the aim of investigating the effect of nitrogen availability upon drought strain in Norway spruce trees. Forest soil (Typic Udipsamment) was filled in lysimeters 1 m in diameter and 1 m deep. Small trees of Norway spruce from five different clones were planted in the lysimeters. Roofs under the canopy of the trees ensured full control of water and nutrient input. Three levels of nitrogen were given to the trees during five years; ambient rainwater, and five and fifteen times this N concentration, respectively. Additional N was given as NH₄NO₃ in irrigation water. Mean annual N-addition during the five years corresponded to 5, 27 and 82 kg per ha and year for the three treatments, respectively. During the third and fifth growth season drought was artificially induced. In addition to a watered control, two levels of drought were applied, representing water deprivation for 2 and 3 months, respectively, in 1990 and 3 and 4 months, respectively in 1992. A higher water consumption in the nitrogen fertilized trees during the droughts resulted in a significantly lower pre-dawn shoot water potential compared to the trees receiving ambient rain N. The interaction between drought and nitrogen fertilization was clear also for photosynthesis and transpiration. A decrease in height- and diameter increment caused by drought was most pronounced in the 82 kg N ha^–1 yr^–1 treatment. A water strain integral showed a strong positive correlation to the needle biomass of the trees. Foliar concentrations of several nutrients decreased significantly with increasing drought strain in the trees. Concentration of potassium and boron were especially low and visual symptoms of deficiency occurred.     

Respiration and photosynthesis in cones of Norway spruce (Picea abies (L.) Karst.)

Summary Dark respiration and photosynthetic carbon dioxide refixation in purple and green Picea abies cones were investigated from budbreak to cone maturity. The rate of dark respiration per unit dry weight and CO₂ refixation capacity decreased during cone maturation. At the beginning of the growing season, photosynthetic CO₂ refixation could reduce the amount of CO₂ released by respiration in green and purple cones by 50% and 40%, respectively. The seasonal performance of the components of the cone carbon balance was calculated using information on the seasonal course of respiration, refixation capacity and the light response curves of cone photosynthesis, as well as the actual light and temperature regime in the field. The daily gain of CO₂ refixation reached 28%–34% of respiration in green and 22%–26% in purple cones during the first month of their growth, but decreased later in the season. Over the entire growth period refixation reduced carbon costs of cone production in both cone colour polymorphs by 16%–17%.     

Enhancement of somatic embryogenesis in Norway spruce (Picea abies L.)

Summary Embryogenic callus developed in 55% of the mature embryo explants of Norway spruce (Picea abies L.) growing on a LP medium minus the amino acids and sugars (except sucrose). This is the highest reported yield of embryogenic callus from mature embryos of P. abies that has ever been reported. Callus induction from either the middle or the end of the hypocotyl of the embryos began after 2–3 weeks. Three types of calli were recovered: (a) globular, (b) light green-compact, (c) white mucilaginous. Only the white mucilaginous calli were embryogenic. The globular and light green-compact calli never become embryogenic, even after several subcultures. The development of somatic embryos was accomplished on half-strength macro-elements of NSIII medium containing 1 M -naphthaleneacetic acid, 1 M abscisic acid, and 3% sucrose. The addition of 10^–7 M buthionine sulfoximine to the medium increased the development of somatic embryos by three fold. These results suggest that there is a great potential for increasing the frequency and development of somatic embryos in P. abies. Careful selection of the genotype and modification of the culture medium is required.     

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.     

Patterns and mechanisms of transpiration in a large subalpine Norway spruce (Picea abies (L.) Karst.)

In situ water relations of a large subalpine Norway spruce (Picea abies) were analyzed by simultaneous measurements of sap flow at different crown positions. In the diurnal scale, transpiration varied greatly, both spatially and temporally. Over longer periods, however, different parts of the crown transpired in fairly constant proportions. The average estimated transpiration was about 3.5 times greater in the upper than in the lower half and decreased 1.6-fold from south to north. Water intercepted from rain, fog and dew buffered and significantly decreased the transpiration. The effect was strongest in those parts which were least coupled to the free atmosphere. The top of the crown seemed to experience a regular shortage of water shortly after starting transpiration, when it was forced to switch from internal reserves to sources in the soil. Further, lower branches then started transpiring, which may have led them to compete for the water. An enhanced nocturnal sap flow during warm and dry winds (Foehn) indicated that the tree also transpired at night. Shaded twigs had more capacity to intercept water externally than twigs in the sun. The significance of the crown structure for interaction with water in both liquid and vapour phases is discussed.     

Effect of artificial soil acidification and liming on growth and nutrient status of mycorrhizal roots of Norway spruce (Picea abies [L.] Karst.)

Effects of soil acidification and liming on biomass responses and free Al, Ca, K, Mg, Mn and P contents of mycorrhizal roots of mature Norway spruce (Picea abies [L.] Karst.) were studied at Höglwald Forest in Southern Germany.At the untreated site, mycorrhizal root biomass was lower in the acid humus (pH = 3.3) than in the less acid upper (0–5 cm) mineral soil (pH 4.1). Mycorrhizal roots from the humus contained 10% of the level free Al in mycorrhizal roots from the upper mineral soil. During seven years of soil acidification the quantity of mycorrhizal roots remained unaffected in the humus and the upper mineral soil, perhaps due to the high buffering capacity of the humus which prevented a significant alteration of the nutrient status of the roots. However, two years after soil acidification had been terminated, the percentage of mycorrhizal roots in the humus decreased, possibly because the free root concentrations of K had decreased.On the other hand, six years after liming, there was a two-fold increase of the annual mean quantity of mycorrhizal roots in the humus. Compensatory liming (acid irrigation after liming) had a similar effect on mycorrhizal root production in the humus. However, two years after acid irrigation had been terminated a decrease of mycorrhizal roots in the upper mineral soil (0–5 cm) was observed. Since the total amount of mycorrhizal roots in the humus and upper mineral soil remained constant, compensatory liming produced a shift in fine roots to the humus layer.The higher mass of living mycorrhizal roots in the upper mineral soil (0–5 cm) as compared to the humus of the untreated plot as well as the increased mass of mycorrhizal roots in the humus after liming or compensatory liming are both attributed to an increase in pH to 4.5 rather than alleviation of Al toxicity.     

Dendrochronology of Norway spruce (Picea abies (L.) Karst.) from two range centres in lowland Poland

In Europe, spruce grows in two main regions which meet in Poland, one to the north and east, the other to the south and west. The northeastern area ranges from the northern treeline extending from Norway to Siberia, to southern Sweden, north-eastern Poland and the southern Ural mountains. The southwestern spruce region reaches the mountainous areas of the Alps and the Balkans, the mountains and uplands of the Sudety Mountains, the Carpathians and neighbouring lowlands. Opinions about the distribution of Norway spruce have changed over the years, and its scarcity in the centre of Poland has been strongly debated. The favoured current theory is that Norway spruce once had a continuous distribution in Poland. It is assumed that the rare occurrence in the central Polish lowland is due to a combination of unfavourable soil conditions and previous management activity. The main aim of this work was to analyse climate–growth relationships of Norway spruce in eastern Poland and distinguish regions with similar increment patterns with regards to spruce range. Spruce growth in northern Polish sites is positively correlated with rainfall from May to July. Tree-ring widths in southern sites are more correlated with March temperature. Selected homogenous regions are the same as range types. Trees from the so-called “spruceless area” seem to have similar climate–growth relationships to trees from the southern region. This finding does not settle the question of the origin of the trees, but it does indicate that similar environmental conditions exist in these two areas and proves that the climate was not a limiting factor there.

Effects of elevated soil solution Al concentrations on fine roots in a middle-aged Norway spruce (Picea abies (L.) Karst.) stand

Aluminium (Al), mobilized by acidic deposition, has been claimed to be a major threat to forest vitality. Fine root mortality, decreased root growth and reduced nutrient uptake have been observed in controlled laboratory experiments where roots of tree seedlings were exposed to elevated concentrations of Al. Yet, evidence for Al-induced root damage from forest stands is scarcely reported. Nevertheless, Al dissolved in soil water has received a key role in the critical load concept for forests. Here, we present effects of artificially elevated concentrations of Al in the soil solution on fine roots in a middle-aged stand of Norway spruce (Picea abies (L.) Karst.). Although the inorganic Al concentrations about 200 µM and Ca:Al ratio about 0.7 that were established in the soil solution within this experiment have been associated with reduction of root growth and root mortality for spruce seedlings in hydroponic studies, no acute damage on fine roots was observed. Three years of treatment did not cause visual root damage, nor were effects on fine root necromass observed. Fine root necromass made up about 10% of fine root biomass for all treatments. However, significantly lower molar Ca:Al and Mg:Al ratios in living and dead fine roots were found in the plots where Al concentrations were highest and ratios of Ca to Al in the soil solution were lowest. The lack of response on fine root biomass suggests that forest stands tolerate higher Al levels than results from laboratory experiments indicate. We conclude that effect studies in the laboratory have limited value for field conditions. The key role of Al toxicity, expressed as the Ca/Al ratio, in critical load calculations for forests may have to be reconsidered.     

Effect of auxins and ectomycorrhizal elicitors on wall-bound proteins and enzymes of spruce [Picea abies (L.) Karst.] cells

Summary Elicitors of the ectomycorrhizal fungus Hebeloma crustuliniforme and auxins (IAA, NAA and 2,4-D) were tested for their effects on apoplastic proteins and enzymes of suspension cultured cells of Picea abies (L.) Karst. The ectomycorrhizal elicitor increased the amount of some ionically wall-bound proteins (36, 28, 24, 21 kDa) and decreased the amount of others (61, 22 kDa). The elicitor triggered an H₂O₂ burst and enhanced the peroxidase (EC 1.11.1.7) activity of the Picea cells by increasing one of the two wall-bound peroxidase isoforms. Auxins significantly suppressed the elicitor induction of peroxidase but did not influence the elicitor-triggered H₂O₂ burst. The elicitors and auxin did not change the amount and the pattern of wall-bound invertase isoforms (EC 3.2.1.26) of spruce cells. However, auxin reduced the uptake of glucose by spruce cells and increased the acidification of the cell culture medium. Since Hebeloma lacks apoplastic invertase as well as a sucrose uptake system, utilization of plant-derived sucrose depends on the apoplastic plant invertase activity. Although the host invertase is constitutive, the fungus might be able to increase this invertase activity within a mycorrhiza by lowering the pH of the interface towards the pH optimum of the enzyme via the action of auxin. This fungus-released hormone could increase the H⁺ extrusion of plant cells by activation of the plant membrane H⁺-ATPases. Additionally, an auxin-dependent suppression of glucose uptake by cortical root cells could improve the glucose supply for the fungus. Furthermore, the fungal auxin might suppress the elicitor induced formation of defense enzymes, such as peroxidase.     

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     

Bacterial endophytes from seeds of Norway spruce (Picea abies L. Karst)

Endophytic bacteria from wooden plants and especially seed-associated endophytes are not well studied. Fresh seeds collected from four Norway spruce trees (Picea abies) from different locations in the Slovene subalpine region were surface-sterilised and dissected into a seed coat, embryo and endosperm. The presence of endophytes was detected by culturing methods and by direct amplification of the eubacterial 16S rDNA gene. Both approaches identified bacteria from genera Pseudomonas and Rahnella in the Norway spruce seeds. Both are known plant-associated bacteria with growth-promoting properties and biological control potential. We suggest that plant seeds could serve as a vector for transmission of beneficial bacteria.     

The ion concentration of dew condensed on Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) needles

Summary Dew droplets collected with pipettes from coniferous needles were analysed for their ionic composition. Almost all samples of dew taken from Scots pine trees (Pinus sylvestris) showed significantly higher ion concentrations than those taken from Norway spruce trees (Picea abies). This can be explained by the micromorphology of the needle surface. The higher microscale roughness of the wax layer of a pine needle causes a more efficient flux of atmospheric aerosol particles compared to the spruce needle surface. Dew on coniferous needles is shown to be capable of maintaining pH values below 3 for several hours.     

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