Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary A declining Picea abies (L.) Karst. stand produced as much foliage and branches as a healthy stand but less stemwood at a similar leaf area index and climate. Nutrient analyses revealed that most biomass components at the declining site had lower concentrations of calcium and magnesium, but similar nitrogen and potassium (except for lower potassium in younger needles) and higher phosphorus, manganese and aluminum than the respective components at the healthy site. Comparison of these data with the results from studies on the nutrition and growth of P. abies seedlings (Ingestad 1959) led to the conclusion that the healthy stand is in a balanced nutritional state, while trees at the declining stand have only 56% of the foliar magnesium concentration required to permit growth at a rate which could be achieved at their nitrogen status. It appears that acidic deposition, which involves an input of nitrogen and a leaching of cations from the soil, causes an imbalance in the availability of nitrogen and magnesium. Growth is eventually reduced as magnesium becomes limiting.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary The water relations of Picea abies in a healthy stand with green trees only and a declining stand with trees showing different stages of needle yellowing were investigated in northern Bavaria. The present study is based on observations of trees differing in their nutritional status but apparently green on both sites in order to identify changes in the response pattern which might be caused by atmospheric concentrations of air pollutants and could lead to the phenomenon of decline. Transpiration was measured as water flow through the hydroactive xylem using an equilibrium mass-flow measurement system. Total tree transpiration was monitored diurnally, from July 1985 until October 1985 at both sites. The relationship between transpiration and meteorological measurements indicated that transpiration was a linear function of the vapor pressure deficit. No differences in transpiration of green trees were observed between the two sites. Canopy transpiration was 57%–68% of total throughfall and 41%–54% of total rainfall. Due to this positive water balance, soil water potential at 10 and 20 cm depths remained close to-0.02 MPa (max.-0.09 MPa) for most of the summer. Soil water potential was correlated with the difference between the weekly precipitation and transpiration. No differences in the water relations of apparently healthy trees in the two P. abies stands were observed. It is concluded that differences between green trees at the two sites in terms of nutrient relations or growth rate cannot be explained by changes in whole-tree transpiration or soil water status.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary This is the first in a series of papers on the growth, photosynthetic rate, water and nutrient relations, root distribution and mycorrhizal frequency of two Norway spruce forests at different stages of decline. One of the stands was composed of green trees only while the other included trees ranging in appearance from full green crowns to thin crowns with yellow needles. In this paper we compare the growth and carbohydrate relations of the two stands and examine relationships among growth variables in ten plots. The declining stand produced 65 percent of the wood per ground area compared with the stand in which all trees were green because its foliage produced less wood at any level of leaf area index. The difference in foliage efficiency between the sites could not be explained by differeneces in climate, competition or stand structure. The declining stand appeared to have lower carbon gain as indicated by a smaller increase in reserve carbohydrates before bud break, and weaker sinks for carbohydrates as indicated by less use of the stored carbohydrates than the healthy stand. Thus, growth reduction was probably related to factors which affect both photosynthesis and, even more, the sinks for carbohydrate.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary Photosynthetic rates and nutrient contents of spruce needles were measured in a region with high levels of air pollution in NE Bavaria, Germany (FRG), and compared to spruce grown under clean air conditions at Craigieburn, in the South Island of New Zealand (NZ). The absolute rates of CO₂ uptake, the slope of the CO₂ response curve at 240 l l^–1 internal CO₂ concentration, and the change of photosynthetic rates with needle age at ambient and saturated CO₂ concentrations were virtually identical at both measuring sites. These results confirm an earlier conclusion, that there is no long-term effect of atmospheric pollutants directly on photosynthetic CO₂ uptake rates with persistent exposure at the FRG site to high levels of anthropogenic air pollution. Photosynthetic capacity at saturating CO₂ concentration was three times higher in the NZ spruce. Needles with high photosynthetic capacity in NZ had lower nitrogen and higher calcium concentrations per unit dry weight but higher concentrations of nitrogen, phosphorus, potassium, magnesium and calcium per unit leaf area, and twice the specific leaf weight.     

Performance of two Picea abies (L.) Karst. stands at different stages of decline

Summary The annual replacement of tillers of Agropyron desertorum (Fisch. ex Link) Schult., a grazing-tolerant, Eurasian tussock grass, was examined in the field following cattle grazing. Heavy grazing before internode (culm) elongation seldom affected tiller replacement. Heavy grazing during or after internode elongation, which elevates apical meristems, increased overwinter mortality of fall-produced tillers and reduced the number and heights of these replacement tillers. Unexpectedly, tussocks grazed twice within the spring growing season tended to have lower overwinter tiller mortality, greater tiller replacement, and larger replacement tillers than tussocks grazed only once in late spring. These responses of twice-grazed tussocks, however, were still less than those of ungrazed tussocks or tussocks grazed moderately in early spring. The presence of ungrazed tillers on partially grazed tussoks did not increase the replacement of associated grazed tillers relative to tillers on uniformly grazed plants. This result indicates that resource sharing among tillers, if present, is short-lived or ecologically unimportant in this species. Although A. desertorum is considered grazing-tolerant, tiller replacement on heavily grazed tussocks, particularly those grazed during or after internode elongation when apical meristems were removed, was usually inadequate for tussock maintenance. These observations at the tiller (ramet) level of organization in individual tussocks (genet) may explain the often noted reduction in stand (population) longevity with consistent heavy grazing.     

Quantitative and localized element analysis in cross-sections of spruce [Picea abies (L.) Karst.] needles with different degrees of damage

Summary Proton-induced X-ray microanalysis (micro-PIXE) permits the simultaneous determination of the content and the distribution of elements with atomic numbers higher than Z = 13 in biological samples. This method was used to investigate element content and localization in cross-sections of 6-month-old spruce needles. It was possible to detect the elements silicon, phosphorus, sulphur, chlorine, potassium, calcium, manganese, iron and zinc in semithin (10 m) sections of the needles. The localization of the cationic elements like potassium, calcium and manganese was determined in the one-dimensional line scan mode and in the two-dimensional raster scan mode. To demonstrate the usefulness of this method for forest decline research, element content and localization were compared in needles from two trees, which differed in their degree of damage. We were able to detect differences in the amount of cations and in their distribution inside the needles.     

Photosynthetic performance and nutrient status of Norway spruce [Picea abies (L.) Karst.] at forest sites in the Ore Mountains (Erzgebirge)

Summary Photosynthetic performance of several needle age classes of Norway spruce trees [Picea abies (L.) Karst.] in highly SO₂-polluted and heavily damaged forest sites was measured at two different locations in the Ore Mountains (Erzgebirge, Krusne Hory) during early summer. The carboxylation efficiency showed a dramatic drop from current-year's needles to 1-year-old needles with only a slight further decrease with increased needle age. The light use efficiency also revealed these characteristics. For both parameters, no linear decrease with needle age could be found. In contrast, the maximum photosynthetic capacity (A₂₅₀₀) decreased linearly with time and revealed a good correlation with the total sulfur content of the needles. Absolute values measured for A₂₅₀₀ were approximately 50% lower than those of comparable trees in the nearby Fichtelgebirge. Mineral deficiencies or acute nutrient imbalances of the needles were not detected. In contrast to the situation in the forests of the Fichtelgebirge, a direct effect of gaseous SO₂ on the trees in the Ore Mountains seems plausible.This paper is dedicated to our teacher Professor Otto Ludwig Lange on the occasion of his 65th birthday     

Changes in the content and constituents of the cuticular wax of Picea abies (L.) Karst. in relation to needle ageing and tree decline in five European forest areas

Cuticular wax composition of healthy and and declining mature Norway spruce trees [Picea abies (L.) Karst.] was investigated in five European forest areas. The amount of extracted wax and the content of alkanes and secondary alcohols were analysed as a function of the factors sample area (five areas, detailed below), needle age (current year to 2 years) and decline class (Class O to Class 2). Using a GC-MS, alkanes from C₂₀ to C₃₁ and the following alcohols were quantified: 10-nonacosanol, 5,10-nonacosandiol, 4,10-nonacosandiol and the triterpenol 24-methylenecycloartanol. According to our results, the total wax content as well as the alkane and alcohol content of waxes show a large variation corresponding to sample area and needle age. Ageing caused a highly significant increase in alkane content and a highly significant decrease in total wax and alcohol content. The decline class significantly influenced only the content of the long chain alkane C₃₁ (increase), the secondary alcohol 10-nonacosanol (decrease), and the triterpenic alcohol (decrease). Total wax weight was not influenced by tree damage. Thus, according to our results, needle ageing and progressive tree damage are correlated to different changes in the examined parameters.     

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.

Experiments on the water budget of densely and sparsely needled spruces [Picea abies (L.) Karst.] in a declining stand

Summary The osmotic potentials of needles were compared from numerous trees that had been classified according to needle loss along an altitude profile. With the increasing degree of damage of the trees, the maximum and minimum values deviated more strongly above and below the common mean of all samples. The level of water content of the needles unequivocally reflected the vitality of the trees. Experiments covering a whole vegetation period were performed on a tree pair selected from a natural stand. They were designed to demonstrate differences in water balance between the healthy and damaged state of the trees. For the damaged tree, measurements of the water potentials of single needles showed a greater reduction of potential during the course of the day compared to the healthy tree. Recovery in the evenings was slower and often incomplete. The osmotic potentials of damaged and healthy shoots measured in individual needles also differed both predawn and especially after transpiration stress. Depending on weather and soil desiccation, the differences were more or less pronounced. In the damaged tree, the rises in potential after saturation of the twigs fell far short of the healthy tree. Reduction of water potential, osmotic potential and relative water content under comparable stress conditions suggest a reduced tolerance of drought by damaged trees. In the context of earlier experiments this result was ascribed to a lack of stomatal control, and long-term pollution effects were thus explained as a specific disturbance of hydroregulation.     

Phloem transport in Picea abies (L.) Karst. in mid-winter

Summary Translocation of ¹⁴C assimilates was studied on four different transport systems of Picea abies branches after induced activation in January. ¹⁴CO₂ assimilation of terminal shoots for 48 h at 25° C resulted in phloem loading and basipetal transport of ¹⁴C photosynthate into the following, older shoot generations. ¹⁴C import was enhanced, when these older shoot generations were kept in the dark. Microautoradiographs of the labelled terminal shoots showed that ¹⁴C assimilates were exported from needles via sieve elements of the leaf traces and loaded into the latest increment of the axial secondary phloem. No ¹⁴C label appeared in the obliterated sieve cells or in the tracheids. In addition, ¹⁴C photosynthate accumulated densely in the chlorophyllous cells of the cortex and in cells of the resin ducts, indicating certain sink activity. In the darkened 2-year-old shoot, imported ¹⁴C photosynthate was concentrated in the functional secondary phloem, while some ¹⁴C label was unloaded into the latest xylem increment. When 6-year-old shoots were exposed to ¹⁴CO₂ for 48 h in the light, ¹⁴C assimilates accumulated in the phloem of the leaf trace and in the latest increment of the axial secondary phloem. However, a substantial amount of radioactivity was unloaded into ray cells and phloem parenchyma cells. Thus, the presence of functioning phloem in needles and twigs of P. abies during winter allows long-distance translocation and radial distribution of assimilates according to existing source-sink relations.     

Seasonal variation in the monoterpenes in needles of Picea abies (L.) Karst.

Summary This investigation was conducted to obtain information about the fluctuations in composition and amount of needle monoterpenes during the development of spruce needles. Studies conducted with two Norway spruce clones clearly revealed the existence of fluctuations. In juvenile needles, the amounts of the oxygenated terpenes increase constantly with age during the first 2 months of needle growth. The hydrocarbon terpenes dominate within the first weeks, some of them even showing a very distinct first maximum within the first 3 weeks after bud burst. All terpenes, including the oxygenated ones, have a maximum in June/July, which favours the hypothesis of a substitution of the hydrocarbons later on. There are significant changes even in mature needles of Norway spruce. The terpene level of 1-year-old needles of the clonal trees increased from spring to early summer and then dropped again towards winter. In addition, fluctuations in mature needles were shown for a set of ten wild trees. Needles of the same age class, which emerged in 1986, were sampled 4 times from 1986 to 1988. The needle terpene concentrations of the 1 -year-old needles were considerably lower in spring at the time of bud burst than in autumn. The terpene level of older needles thus seems to be influenced by biosynthetic and catabolic activities.     

Naturally occurring monoterpenoids in needles of Picea abies (L.) Karst

Summary An analysis was made of the effects of different sampling and extraction techniques on the amounts and pattern of monoterpenoids isolated from needles of Norway spruce. The following isolation and analysis procedure was finally adopted: liquid nitrogen-cooled needles were pulverized by a microdismembrator, extracted with pentane overnight at 2°–3°C and concentrated to a volume not less than 3 ml/g fresh weight on a Vigreux column. The crude extract was injected splitless (with solvent split) onto a cold programmed temperature vaporized (PTV) precolumn of a gas chromatograph and the vaporizable compounds heated to a capillary column. This method was tested for production of artefacts and quantitative extraction and applied to needles of eleven 80-year-old spruce trees.     

Isolation of two cytokinin metabolites from the rhizosphere of Norway spruce seedlings (Picea abies L. Karst.)

Roots of young Norway spruce seedlings were incubated under hydroculture conditions in a synthetic nutrient medium containing either ³H-isopentenyladenosine, isopentenyladenosine or zeatin riboside. When feeding with ³H-isopentenyladenosine a new radiaolabelled metabolite was found in the feeding solution as well as in root extracts. Isopentenyladenosine and zeatin riboside were metabolised and for both compounds an unknown metabolite was detected in the feeding solution. The metabolites were purified by solid phase extraction, HPLC and partially characterised. A major characteristic of the metabolites is their reactivity in the presence of NH₄OH, which results in the formation of the cytokinin bases isopentenyladenine or zeatin, respectively. UV-spectra and the chemical characteristics indicate that the new metabolites are closely related. The GC-MS analysis revealed, that the metabolites are true derivatives of isopentenyladenine and zeatin. The biogenesis of the new metabolites is discussed with regard to plant microbial interactions.Abbreviations Ck(s) = cytokinin(s) - GC-MS = gas chromatography-mass spectrometry - iP = isopentenyladenine - [9R]iP = isopentenyladenosine - [9G]iP = isopentenyladenine-9-glucoside - [9R-MP]iP = isopentenyladenosine-5-monophosphate - Z = trans-zeatin - [9R]Z = trans-zeatin riboside     

Fungal injury to seed tissues of Norway spruce,Picea abies (L.) Karst.

Norway spruce bore an abundance of cones in Finland in 2000, but these cones were often fungal-infected. The seeds had structural injuries that were revealed when seed samples were examined using light (LM) and a field emission scanning electron microscope (FESEM). Two main types of spores were found either in the tissues inside the seed coat or on the sarcotesta, the outermost layer of seed coat. The spores of Chrysomyxa pirolata appeared particularly in the nucellar tissue, where the cell walls were disintegrated at the middle lamellae and cytoplasm was disrupted. Degenerated remnants of fungal structures resembling aecial peridium were found close to aeciospores. The tissue of the megagametophyte differed also from that of a normal mature seed. Conidia of Thysanophora penicillioides were often encountered on the sarcotesta where the ordinary wax cover was missing. Fungal injury occurred in the nucellar layers that shelter the embryo and megagametophyte from desiccation and oxidation. Destruction of these structures together with rapid opening of the seed coat advance deterioration of seeds during storage and may cause unexpected economic losses in forest plant production.     

Characterization of Picea abies (L.) Karst. ectomycorrhizas: discrepancy between classification according to macroscopic versus microscopic features

Summary In a 3-year study of ectomycorrhizal diversity in 2 Norway spruce stands in Switzerland the macroscopically classified ectomycorrhizal types were analyzed microscopically to compare the results of the 2 approaches. A total of 22 ectomycorrhizal types were macroscopically classified in the 2 stands. Microscopic investigations — particularly of mantle structures — resulted in the identification of 7 additional types to give a total of 29. These additional types resulted from separation of macroscopically identical types occurring on both stands (type-pairs) at the microscopic level. The problematic nature of characterization and classification of ectomycorrhizas is discussed.     

Poor stomatal control of water balance and the abscission of green needles from a declining stand of spruce trees [Picea abies (L.) Karst.] from the northern Alps

On a site on the west slope of the Wank in the northern Alps changes in water potential, osmotic potential and transpiration rate were measured in spruce trees during the dry summer months of 1991. The pattern of decrease in water potential and osmotic potential on days of varying evaporative demand from trees of widely different decline conditions was used to describe the relative ability of the trees to withstand drought stress. Stress diagrams served as a tool for interpreting the state of health of each tree. The criterion is independent of the water situation of the tree and the other external conditions of the respective experiment. These diagrams clearly show that the foliage of spruces with high needle losses reaches the limit of endurance relatively early. For equal evaporative demand much lower turgor levels were observed in spruces with high needle loss compared to undamaged trees. Associated with the occurrence of low turgor values was the shedding of green needles. The abscission zone was shown in sections. The accumulation of highly fluorescent substances in the bundle sheath cells of the same material was described. Incomplete to non-existent stomatal control over water loss was attributed to modifications in the cell walls of the stomata which appear to alter the ability of the guard cells to sense changes in either atmospheric or cellular hydration. Our studies point to the following situation: air pollution directly affects stomatal control, the loss of stomatal control changes the drought avoidance abilities of the foliage and, as a consequence, low turgor levels occur and premature needle abscission is induced. As site water balance decreases, either due to a dry year or to poor moisture holding abilities of the soil, these conditions become apparent.     

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.     

Uptake of water and solutes through twigs of Picea abies (L.) Karst

Summary Uptake of water and magnesium chloride solution was investigated through the outer surface of twigs of Picea abies (L.) Karst. Water uptake was determined by using pressure/volume (P/V) curves of the twigs as a basis for calculation to avoid problems of superficial extraneous water. When water was sprayed on bark and needles of 3- to 7-year-old twigs at a xylem water potential of -1.00 MPa, they absorbed as much as 80 mm³ water in 200 min/g twig dry weight as the twig water potential recovered to -0.15 MPa. With fluorescent dyes, pathways for absorption of water and solutes through the twig bark were found, particularly through the radially orientated ray tissue. In addition to uptake by mass flow, magnesium could also diffuse along a concentration gradient from the twig surface into the xylem. In the field, the magnitude of these uptake processes would depend on the concentration of elements deposited by atmospheric precipitation, the concentration gradient between the plant surface and the xylem sap, the xylem water potential and the intensity and duration of each precipitation event.     

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%.