High level histone H2A gene expression during early stages of adventitious bud formation in Norway spruce (Picea abies)

We have demonstrated the correlation between cell division and the expression of a histone H2A-encoding gene, His2A , in Norway spruce. Picea abies (L.) Karst and used a cDNA clone in in situ hybridization experiments to monitor the cytokinin-induced cell division during early stages of adventitious bud development. A general stimulation of division of epidermal and cortical cells followed upon the cytokinin treatment. After two weeks in culture a high mitotic activity was detected only in single cells or small groups of cells in the epidermis and subepidermal cell layers. These cells presumably constitute the early stages of meristem primordia. The small clusters of dividing cells enlarge and subsequently form adventitious buds. Cells of the meristem and needle primordia of adventitious buds divide frequently as do the corresponding cells in vegetative buds. A quiescent center is distinguished within the apical meristem of vegetative buds. These cells, in the summit of the domed meristem, divide with a considerably lower frequency than cells in the flanking region. Differences in the temporal expression pattern of the histone H2A gene in cells of the vascular tissue, detected between embryos germinating in vitro and bud-induced embryos, suggest that the cytokinin treatment affects the timing of cell divisions in the differentiating procambium.     

Populations of root-feeding aphids in the Liphook forest fumigation experiment

Three species of root aphid (Pachypappa vesicalis Koch, Pachypappa tremulae L. and Prociphilus (Stagona) xylostei De Geer) were found feeding on Norway spruce [Picea abies (L.) Karsten] that were exposed to elevated concentrations of O₃, and/or SO₂ in a field manipulation experiment at Liphook, England. The experiment exposed conifer trees to controlled concentrations of these gases between 1987 and 1990. Root-aphid populations feeding on Norway spruce were monitored in autumn 1990, the third year of fumigation and in autumn 1991, 10 months after fumigation had ceased. In 1990 the numbers of aphids in the high-SO₂, high-SO₂+ O₃ and O₃ treatments were significantly less than in ambient plots. Although after fumigation had ceased in 1991 the ambient plots still had higher numbers than the treatment plots, most of these differences were no longer statistically significant. In all plots sampled, total numbers of root aphids were higher in 1991 than in 1990. These results indicate that the numbers of root aphids in the experiment were negatively related to pollution levels. This relationship is the same as that shown in controlled laboratory experiments and is the converse of that generally reported in experiments using shoot-feeding aphids.     

Estimates of larval survival of cod by releases of genetically marked yolk-sac larvae

In the spring of 1995, 18 million genetically marked yolk-sac cod larvae Gadus morhua were released into a 2.9-km², nearly land-locked fjord in western Norway. Four quantitative surveys were conducted, 11, 33, and 63 days, and 1 year after the first release. Almost 100% of the collected cod larvae were successfully identified to GPI-1 * genotype. The marked cod larvae constituted 18% of all sampled cod larvae in the first survey and 9% in the two next. The average rate of mortality was estimated to be 23% day ⁻¹ for the first 10 days after release and 12% day ⁻¹ during the next month after release. After 1 year (April 1996), the number genetically marked I-group cod in the fjord was estimated to be <120. The effect of the historical programme of large-scale releases of yolk-sac larvae on recruitment were evaluated and found to be small.     

Effects of aluminium on calcium and magnesium uptake and translocation by root segments of whole seedlings of Norway spruce (Picea abies Karst.)

In the Ardennes, spruce decline is correlated with Mg deficiency caused by acid rain leaching of soil nutrients, associated with solubilization of Al-containing soil minerals. Laboratory experiments were carried out to measure the uptake and translocation of 45Ca and 28 Mg by intact roots of spruce seedlings in solutions containing various amounts of added AlCl3. Translocation rates in the various organs of the seedlings were higher for magnesium than for calcium. A 1 mt M Al nutrient solution had a much stronger inhibitory effect on uptake and translocation of Mg than it had on Ca. These rate differences result largely from differences in the chemical characteristics of these two elements.     

Relationship between respiratory depletion of sugars and loss of cold hardiness in coniferous seedlings over-wintering at raised temperatures: indications of different sensitivities of spruce and pine

Long-term effects of elevated winter temperatures on cold hardiness were investigated for Norway spruce (Picea abies L. Karst.), lodgepole pine (Pinus contorta Dougl.) and Scots pine (Pinus sylvestris L.). Two-year-old seedlings with the same pre-history of growth and cold hardening in the field were maintained from early December to late March at two field sites in northern Sweden and in a cold room. The temperatures at these locations averaged –13·5, –8·9 and 5·5°C, respectively. Following treatments, carbohydrate contents and cold tolerances were assessed. Needle respiration was also analysed during the 5·5°C treatment. Cold tolerance of lodgepole pine and Scots pine was much reduced following the 5·5°C treatment. Cold tolerance was somewhat reduced in lodgepole pine following the –8·9 °C treatment, but was essentially maintained in spruce throughout all treatments. The cold tolerance of needles was strongly correlated with their soluble sugar contents. Spruce maintained cold hardiness by having larger reserves of sugars and lower rates of respiration which decreased more rapidly as sugars were depleted. Tolerance of lodgepole pine to frost desiccation was also much reduced following the 5·5°C treatment.     

Dynamics of understory vegetation in an old-growth boreal coniferous forest, 1988–1993

Abstract. Understorey vegetation changes in a South Norwegian old-growth coniferous forest were studied between 1988 and 1993 in 200 1-m² vegetation plots. Our aims were to quantify the amount of between-year compositional change, and to elaborate the environmental basis for long-term vegetation change, including the previously identified gradient structure with a major gradient related to topography (and soil nutrient status and soil depth) and a minor gradient reflecting paludification and canopy coverage. Species richness (yearly mean and cumulative species number) and change in species richness differed between vascular plants and cryptogams, and between forest types. The number of vascular plant species decreased in pine forest in dry years; bryophyte species number increased in spruce forest. Statistically significant vegetation change, as tested by constrained ordination (CCA) with time as the constraining variable, is demonstrated for most one-year periods and for the five-year period in most forest types. Vegetation change along identified gradients, measured as plot displacement along DCA ordination axes, also occurred. The magnitude of year-to-year vegetation change was related neither to forest type nor to one-year period; different responses to climatic and environmental change were observed in each forest type. The largest average displacement observed, from medium-rich spruce forest towards poor spruce forest, was interpreted as a long-term trend. Humus-layer pH decreased by ca. 0.25 units from 1988 to 1993, most strongly in medium-rich spruce forest where exchangeable Ca decreased and Al and Mn increased strongly. Our study supports the hypothesis that vascular plants show a long-term and broad-scale response to soil acidification. Change in bryophyte composition is linked to some very long growing-seasons. Detailed analysis of short-term vegetation dynamics enhances the interpretation of long-term changes and stresses the complementarity of univariate and multivariate methods in the analysis of vegetation change.     

Net primary production and light use efficiency in a mixed coniferous forest in Sweden

Simple light use efficiency (ɛ) models of net primary production (NPP) have recently been given great attention (NPP = ɛ × absorbed photosynthetically active radiation). The underlying relationships have, however, not been much studied on a time step less than a month. In this study daily NPP was estimated as the sum of net ecosystem exchange (NEE) and heterotrophic respiration (R_h) of a mixed pine and spruce forest in Sweden. NEE was measured by eddy correlation technique and R_h was estimated from measurements of forest floor respiration (R_f) and the root share of R_f. The total yearly NPP was on average 810 g C m⁻² year⁻¹ for 3 years and yearly ɛ was between 0.58 and 0.71 g C MJ⁻¹, which is high in comparison with other studies. There was a seasonal trend in ɛ with a relatively constant level of approximately 0.90 g C MJ⁻¹ from April to September Daily NPP did not increase for daily intercepted radiation above 6 MJ m⁻² d⁻¹, indicating that between-years variation in NPP is not directly dependent on total Q_i. The light was most efficiently used at an average daytime temperature of around 15 °C. At daytime vapour pressure deficit above 1400 Pa ɛ was reduced by approximately 50%.     

Vegetation establishment, succession and microsite frost disturbance on glacier forelands within patterned ground chronosequences

Aim The impact of microscale frost disturbance on vegetation colonization and successionary trends was examined within patterned ground features of Little Ice Age chronosequences. The goal was to investigate and compare vegetation response to micro‐site frost disturbance with that of previous studies done at a coarser landscape scale. Location The study sites occur on Little Ice Age glacier forelands within Jotunheimen, Norway (61°–62° N). The forelands of the glaciers Slettmarkbreen, Styggedalsbreen and Vestre Memurubreen have been well studied providing chronological controls for landscape studies. Sorted patterned ground features are found within the chronosequences, typically declining with frost intensity and disturbance with increasing terrain age. Methods Micro‐plots (8.3 × 8.3 cm) were placed at the inner borders and centres of patterned ground features. Species were identified and per cent species cover and per cent cover of life‐form category were noted. Nonparametric Kruskal–Wallis and Mann–Whitney U‐tests were used to test for differences between percent cover of life‐form categories within patterned ground features as well as to identify thresholds of successional change across the chronosequences. Results Significant relationships between life‐from groups and patterned ground positions of varying ages were deduced using nonparametric statistics. Findings were then used to discuss trends of succession within patterned ground features and across the chronosequences. Vegetation establishment occurs at the border positions of young (< 30 years) patterned ground features. With time and distance from the ice margin, vegetation encroaches inwards toward the disturbed centres. Succession within patterned ground exhibits several stages: (1) bryophytes/crusts and lichens, (2) grasses/sedges and (3) woody shrubs. The occurrence of forbs was sporadic and generally non‐significant. Main conclusions Frost disturbance in patterned ground appears to delay successional trends of vegetation communities when compared with previous studies on ‘stable’ terrain, producing micro‐site lag effects. These small patches of disturbed ground are therefore important regarding vegetation assemblages across the landscape and are unlikely to be detected at the landscape scale.     

Decay indices for evaluating wood decomposition activity

The goal of the current study was to evaluate the efficiency of Norway spruce wood decomposition by the saprotrophic fungus Phlebiopsis gigantea (Fr.) Jülich. We identified the following indices as reliable measures of wood decay: decay acceleration index (DAI), final decay index (FD), and decay intensity index (DI). DAI was used to assess acceleration and deceleration of spruce wood loss, FD to estimate the final wood decay, and DI to evaluate the ability of the fungus to decompose wood, taking into consideration changes in mycelial activity over time. We tested the hypothesis that the wood decay activity of any fungus can be evaluated more objectively when: (i) several isolates of the tested fungus are assessed simultaneously, (ii) tests are performed for at least two time-points, and (iii) samples vary in wood density. Allowing a three-month period for wood decomposition was inadequate for reliable assessment of the wood decay ability of P. gigantea. Conversely, six months after inoculation, the tested isolates showed significant differences in their ability to generate dry wood loss, which depended on wood density. In view of these results, the DAI, FD, and DI indices are practical tools for assessing fungal activity to predict wood loss.     

Antrodia gossypium,Phlebiopsis gigantea and Heterobasidion parviporum: in vitro growth and Norway spruce wood block decay

Polymerase chain reaction-amplified and sequenced isolates of Antrodia gossypium, Phlebiopsis gigantea and Heterobasidion parviporum from decaying Norway spruce wood blocks after three and six months, which exhibited linear growth, were investigated. P. gigantea strains showed the fastest growth, whereas A. gossypium growth was five times slower. The differences between the mean daily increment of A. gossypium and the other examined isolates (except Hp2) were statistically significant. There were also significant differences in wood decay between densities over time. These results were confirmed by the decay acceleration index (DAI) and decay activity index, which were positively correlated with wood density regardless of the fungus species. The registered P. gigantea strains (Rotstop and PG Suspension) exhibited a strong decomposition ability (28% after six months); the weight loss caused by A. gossypium after six months of decay (15.2%) was similar to the results of P. gigantea (GB) after just three months (13.2%). All tested H. parviporum isolates showed rather rapid growth and equally strong wood decay (20–25%) compared to those of P. gigantea. DAI showed that A. gossypium may significantly contribute to wood decomposition over time, particularly in less dense wood samples. The use of both saprotrophs as biological agents against root pathogens is discussed.