Comparative studies on the mycorrhization of Larix decidua and Picea abies by Suillus grevillei

Summary Mycorrhization of Picea abies has been achieved, for the first time, with six strains of Suillus grevillei by a new culture method, using activated charcoal paper and liquid medium as a substrate. Mycorrhization of P. abies and Larix decidua was compared, and the process was found to be significantly different in the two tree species. S. grevillei is not incompatible with P. abies, but it forms mycorrhizae more readily with L. decidua. Hyphal growth was clearly stimulated on the surface of roots of Larix but retarded on Picea. A well organized Hartig net was formed with both tree species, but wall protuberances were frequently observed on the outer cell walls of Picea cortex cells when the Hartig net was not fully developed. No conspicuous cell wall reactions occurred in Larix roots. Cell wall protuberances may be comparable to those in transfer cells and are interpreted as an alternative to Hartig net development. Anatomical differences between roots of Larix and Picea, and physiologically active substances such as recognition factors on the root surfaces, are discussed with respect to their responsibility for the different reactions of S. grevillei.     

50 years of change in a Swedish boreal old-growth Picea abies forest

Abstract. Changes in the tree layer (> 1.3m) and sapling layer (< 1.3m, including seedlings) of a Swedish boreal old-growth Picea abies (Norway spruce) forest from the 1930s to the 1980s were studied in permanent plots. The plots were established in 1938–1939 and re-analysed in 1983–1988. Regeneration, mortality, turnover rate in the tree layer and amount of decomposing logs as well as the time required for complete decomposition of logs were investigated using the detailed data from the 1930s. Ca. 25 % of the trees present during the first analysis were no longer alive. This mortality was balanced by recruitment from the sapling layer. The rate of mortality suggests a turnover time for the tree layer of ca. 200 yr. The number of spruces in the sapling layer has increased by ca. 85 %, hypothetically in response to an increase in amount of decomposing wood that can serve as nurse logs and stumps. The mean time for total decomposition was calculated as ca. 200 yr. Spruce regeneration on logs does not occur until the log is at least ca. 50 yr old. The survival pattern in the sapling layer suggests a high mortality rate at the seedling stage (≤ 1 yr) and a low mortality rate at the sapling stage. In conclusion, it is suggested that the amount of coarse woody debris available for regeneration, the occurrence of seedlings, and seedling mortality constitute concurrent factors through which climatic fluctuations, in a long-term perspective, direct stand recruitment and density. As a consequence, these boreal forests will be kept in a dynamical equilibrium.     

Differential energization of the tonoplast in suspension cells and seedlings from Picea abies

 Vacuolar ATPase (EC 3.6.1.3) and PPase (EC 3.6.1.1) were studied in suspension cells and seedlings from spruce [Picea abies (L.) Karst. Proton transport activity and uncoupler (1 μM nigericin) stimulated substrate hydrolysis were measured in tonoplast enriched membrane vesicles. In suspension cells the vacuolar PPase exhibited 1.8-fold activity of the ATPase. In roots and needles from 12-week-old spruce seedlings the vacuolar PPase was inactive, whereas the ATPase was active. Therefore, we investigated whether the preparation of spruce tonoplast vesicles from roots and needles inactivates the vacuolar PPase but not the ATPase. For this purpose, maize (Zea mays L.) tonoplast membranes exhibiting vacuolar PPase as well as ATPase activity were used as a probe and added to the homogenization medium prior to the preparation of spruce vesicles. The preparation of spruce vesicles was more inhibitory to the vacuolar ATPase than to the PPase. The comparison of vacuolar PPases from spruce suspension cells and maize roots revealed similar enzymatic properties. After isopycnic centrifugation on continuous sucrose gradients the vacuolar PPase from spruce suspension cells co-purified with the vacuolar ATPase. Together, these data show: (1) vacuolar PPases from spruce suspension cells and maize roots are similar, (2) the preparation of tonoplast vesicles from spruce roots and needles does not inactivate the vacuolar PPase, (3) tonoplasts of suspension cultured cells and seedlings from spruce are differentially energized by the vacuolar pyrophosphatase that may indicate a difference in pyrophosphate metabolism between embryogenic and differentiated spruce cells, and (4) tonoplast vesicles from spruce seedlings may allow investigations of the effect of pyrophosphate on the vacuolar ATPase in the absence of vacuolar PPase activity. Received: 2 July 1998 / Accepted: 14 September 1998     

Effects of liming and boron fertilization on mycorrhizas of Picea abies

Effects of liming and B fertilization on Norway spruce [Picea abies (L.) Karst.] mycorrhizas were studied in factorial field experiments. The lime was applied twice, about 30 years and 12 years before sampling (2000 and 4000 kg ha^-1 dolomite). B was applied at the rate of 1.5 kg B ha^-1 two years before sampling.Boron fertilization doubled the number of root tips in the top 10 mm of the humus layer. The proportion of dead short root tips was increased from 10 % in control plots to 29 % in the limed plots. Numbers of dead root tips were increased when both lime and B were applied. The % of mycorrhizas with external mycelium was slightly increased and the % of Piloderma croceum Erikss. and Hjortst. was decreased by lime. In conclusion, adverse effects of lime on mycorrhizas were found, which were ameliorated by B fertilization, but lime-induced B deficiency alone was not the only reason for the effects of lime on root mortality.     

Effects of soil pH and calcium on mycorrhizas of Picea abies

The effects of lime, increased soil pH and increased soil Ca concentration on the mycorrhizas of Norway spruce. [Picea abies (L.) Karst.] were studied independently of each other to elucidate the different mechanisms through which lime may influence mycorrhizas in acidic soil. In a field experiment (mature Norway spruce in podzol), lime was applied as CaCO₃; increased Ca concentration without an increase in pH was achieved with CaSO₄; and soil pH was increased without calcium by means of Na₂CO₃ and K₂CO₃ (Na+K treatment). Treatments were done in October, and mycorrhizas were counted from samples collected in the following June and September. All treatments increased the percentage of dead short root tips compared to controls in September, and Na+K already in June. Cenococcum geophilum Fr. increased in proportion in plots treated with Na+K.In a sand culture experiment, Norway spruce seedlings were grown from seed and inoculated with Cenococcum geophilum, or root inoculum, or left uninoculated. When mycorrhizas were beginning to form, CaCO₃ and CaSO₄ treatments were applied. Six weeks later, the percent of dead short root tips in both salt treatments was significantly increased from control, but formation of mycorrhizas was not inhibited by treatments.As all the treatments increased the proportion of dead short root tips, it is concluded that lime directly and adversely affected mycorrhizas of Norway spruce in sand culture and in mor humus. Both increased ionic strength and increased pH may be reasons for this rather than Ca²⁺ specifically.     

Response of fine roots to an experimental gap in a boreal Picea abies forest

We examined the initial response of the quantity and distribution of fine roots to the creation of an experimental canopy gap with a diameter of 50 m in a mature managed Norway spruce forest. Under the canopy, the fine root length densities of trees, shrubs, and grasses and herbs were 3207, 707 and 2738 m m^–2, respectively. The fine root biomass of trees, shrubs, and grasses and herbs were 182, 47 and 52 g m^–2, respectively. Two growing seasons after gap creation hardly any fine tree roots were found in the middle part of the gap. The living tree roots in the gap edge zone were mainly located within a 5-m distance from the standing edge trees. The indices developed here to show the influence of trees on fine root lenght density clearly revealed the effect of the vicinity of living trees on fine root lenght density. The root densities of grasses, herbs and dwarf shrubs did not show a clear response to gap creation despite the increase of their foliage. Our results suggest that in boreal spruce forests a gap disturbance creates a distinct tree root gap and that the gap edge trees do not extend their root systems rapidly into the formed root gap.     

Chlorophyll formation and the development of photosynthesis in dark grown seedlings of Picea abies

Abstract Seeds of Picea abies were germinated and grown in either darkness or constant light. The chlorophyll content and photosynthetic carbon dioxide uptake of developing seedlings of different ages was determined. Ten-day-old dark grown seedlings showed an instant ability for photosynthetic carbon dioxide uptake and also formed further chlorophyll most rapidly upon subsequent illumination. These activities progressively diminished when the dark growth period was extended. Light grown seedlings reached a maximum chlorophyll level after 15 days growth, and this preceded maximal photosynthetic development.     

Effects of liming and boron fertilization on boron uptake of Picea abies

The effects of liming on concentrations of boron and other elements in Norway spruce [Picea abies (L) Karst.] needles and in the mor humus layer were studied in long-term field experiments with and without B fertilizer on podzolic soils in Finland. Liming (2000+4000 kg ha^-1 last applied 12 years before sampling) decreased needle B concentrations in the four youngest needle age classes from 6–10 mg kg^-1 to 5 mg kg^-1. In boron fertilized plots the corresponding concentrations were 23–35 mg kg^-1 in control plots and 21–29 mg kg^-1 in limed plots. Both liming and B fertilizer decreased the Mn concentrations of needles. In the humus layer, total B concentration was increased by both lime and B fertilizer, and Ca and Mg concentrations and pH were still considerably higher in the limed plots than controls. Liming decreased the organic matter concentration in humus layer, whilst B fertilizer increased it.The results about B uptake were confirmed in a pot experiment, in which additionally the roles of increased soil pH and increased soil Ca concentration were separated by means of comparing the effects of CaCO₃ and CaSO₄. Two-year-old bare-rooted Norway spruce seedlings were grown in mor humus during the extension growth of the new shoot. The two doses of lime increased the pH of soil from 4.1 to 5.6 to 6.1, and correspondingly decreased the B concentrations in new needles from 22 to 12 to 9 mg kg^-1. However, CaSO₄ did not affect the pH of the soil or needle B concentrations. Hence the liming effect on boron availability in these soils appeared to be caused by the increased pH rather than increased calcium concentration.     

Forest microsite effects on community composition of ectomycorrhizal fungi on seedlings of Picea abies and Betula pendula

Niche differentiation in soil horizons, host species and natural nutrient gradients contribute to the high diversity of ectomycorrhizal fungi in boreal forests. This study aims at documenting the diversity and community composition of ectomycorrhizal fungi of Norway spruce ( Picea abies ) and silver birch ( Betula pendula ) seedlings in five most abundant microsites in three Estonian old-growth forests. Undisturbed forest floor, windthrow mounds and pits harboured more species than brown- and white-rotted wood. Several species of ectomycorrhizal fungi were differentially represented on either hosts, microsites and sites. Generally, the most frequent species in dead wood were also common in forest floor soil. Ordination analyses suggested that decay type determined the composition of EcM fungal community in dead wood. Root connections with in-growing mature tree roots from below affected the occurrence of certain fungal species on seedling roots systems in dead wood. This study demonstrates that ectomycorrhizal fungi differentially establish in certain forest microsites that is attributable to their dispersal and competitive abilities. Elevated microsites, especially decayed wood, act as seed beds for both ectomycorrhizal forest trees and fungi, thus affecting the succession of boreal forest ecosystems.     

Effects of pre-harvest soil acidification,liming and N fertilization on the survival,growth and needle element concentrations of Picea abies L. Karst. seedlings

There are concerns that the anthropogenic acidification of Swedish forest soils may have severe effects on forest yield, and it has been suggested that liming could be used to counter this problem. The aim of this study was to investigate the survival, growth and element concentrations of C+1 needles of Picea abies (L.) Karst. seedlings planted on plots that had been acidified (in 12 annual treatments totalling 600 or 1200 kg S ha^–1 in the form of elemental sulphur), limed (12×500=6000 kg lime ha^–1 in the form of CaCO₃) or N-fertilized (3×200=600 kg N ha^–1 in the form of urea) prior to harvest. Seedlings growing on plots given a combination of the N plus low S treatments were also tested. None of the treatments, given to triplicate plots, significantly influenced seedling survival during the first five growing seasons. Furthermore, none of the treatments significantly affected growth, although the average growth rate was slightly higher for limed plots. The survival and growth of the seedlings are discussed in relation to differences in the cover of field-layer vegetation between the treatments after the final felling. Needles from seedlings in the limed plots showed significantly lower concentrations of Mn and Al, and higher concentrations of Ca and Zn compared with needles from seedlings in the other plots (i.e. control, high S or N-treated). The K concentration in the needles was significantly higher in limed plots than in high-S plots. Changes of element concentrations observed in the soil, associated with the treatments, where in some cases reflected in the needle concentrations.     

The use of root growth and modelling data to investigate amelioration of aluminium toxicity by silicon in Picea abies seedlings

Three-week-old Picea abies seedlings were grown for 7 days in 100 microM aluminium (Al), combined with 1000 or 2000 microM silicon (Si). Solution pH was adjusted to 4.00, 4.25, 4.50, 4.75, or 5.00. In the absence of Si, solution pH had no effect on the decrease in root growth caused by 100 microM Al. Silicon did not ameliorate toxic effects of Al on root growth at pH 4.00, 4.25 and 4.50, whereas significant, and apparently complete, amelioration was found at pH 4.75 and 5.00. An equilibrium speciation model (EQ3NR), with a current thermodynamic database, was used to predict the behaviour of Al and Si in growth solutions. When Si was not present in the 100 microM Al solutions, Al(3+) declined from 92.4% of total Al at pH 4.00 to 54.6% at pH 5.00, and there was a concomitant increase in hydroxyaluminium species as pH increased. The addition of 1000 microM Si to the 100 microM Al solutions caused a reduction in Al(3+) content over the whole pH range: at pH 4.00 Al(3+) fell from 92.4 to 83.3% in the presence of Si; and at pH 5.00 the fall was from 54.6 to 17.7%. These falls were attributed to the formation of hydroxyaluminosilicate (HAS) species. Similar, but somewhat greater, changes were observed in solutions containing 2000 microM Si. The match between root growth observations and the modelling data was not very good. Modelling predicted that change in Al(3+) content with pH in the presence of Si was gradual, but root growth was markedly increased between pH 4.50 and 4.75. Differences between root growth and modelling data may be due to the model not correctly predicting solution chemistry or to in planta effects which override the influence of solution chemistry.     

Growth and morphological response of old-forest lichens transplanted into a young and an old Picea abies forest

This experimental study focuses on why old-forest lichens such as Lobaria scrobiculata and Platismatia norvegica are scarce in younger spruce stands. Understanding the factors limiting the distribution of species is important for developing appropriate methods for forest management aiming to maintain biodiversity. A successful growth of L. scrobiculata and P. norvegica was found in the young planted stand as the rate of growth did not differ between the young stand and the old spruce forest where they naturally occurred, during 14 months of transplantation. In the young forest environment, L. scrobiculata showed a significantly higher specific thallus weight, and a slightly higher water-holding capacity. This morphological response is probably due to a higher light exposure in the young stand and consequently a higher rate of desiccation. The ubiquitous species Platismatia glauca showed a significantly higher rate of growth in the young forest than in the old forest, and a positive relationship between growth rate and light exposure was found. This transplant study has shown that the environmental conditions in younger planted forests are not necessarily unfavourable for growth of old-forest lichens. Other factors, such as limited dispersal ability and poor diaspore production, are probably important for explaining the species scarcity in younger stands.     

Ethylene effects on peroxidases and cell growth patterns in Picea abies hypocotyl cuttings

The effect of 2-chloroethylphosphonic acid (ethrel) on cell growth patterns and per-oxidase activity (EC 1.11.1.7) and location in young Norway spruce cuttings ( Picea abies [L.] Karst.) was investigated. The peroxidase activity in a fraction containing soluble and membrane bound enzymes show a diurnal variation, with decreased activity during the light period and a corresponding increase during the following dark period. The decrease during the day could to some extent be counteracted by treatment with ethrel. It appears that ethrel affects only peroxidases in the isolated membrane fraction, since peroxidases bound to the cell wall were not affected by ethrel. In vitro experiments indicated that the hydrophobicity of soluble peroxidases was increased by treatment with ethylene. Cytochemical localization of peroxidase activity in differentiating tracheids revealed a clear ethrel-induced increase in the tonoplast. It appears that ethylene affects soluble peroxidases in vivo in such a way that they are directed to a more hydrophobic environment, like the tonoplast. Treatment with ethrel also changed the appearance of the rough endoplasmic reticulum (ER) and Golgi apparatus. Dilated ER cisternae were observed on electron micrographs, as a result of treatment with ethrel. The number of vesicles produced by the Golgi apparatus and also the amount of vesicles fusing with the plasma membrane in secondary-wall-forming tracheids increased considerably. The results clearly indicate that the stimulatory effect of ethylene in spruce seedlings on lignification and cell wall formation, is due to a general stimulation on both synthesis, transport and secretion of cell wall material and not on a stimulation of peroxidase activity as reported for other species.     

Effects of growth medium, nutrients, water, and aeration on mycorrhization and biomass allocation of greenhouse-grown interior Douglas-fir seedlings

Commercial nursery practices usually fail to promote mycorrhization of interior Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco] seedlings in British Columbia, which may account for their poor performance following planting in the field. We tested the effects of four nursery cultivation factors (nitrogen fertilization, phosphorus fertilization, watering, and soil aeration) and field soil addition on mycorrhization, survival, growth, and biomass allocation of interior Douglas-fir seedlings in a series of greenhouse experiments. Where field soil was added to the growing medium, mycorrhization and root/shoot ratios were maximized at lower levels of mineral nutrient application and aeration. Where field soil was not added, mycorrhization was negligible across all fertilization and aeration treatments, but root/shoot ratio was maximized at lower levels of mineral nutrients and the highest level of aeration. Regardless of whether field soil was added, intermediate levels of soil water resulted in the best mycorrhizal colonization and root/shoot ratios. However, field soil addition reduced seedling mortality at the two lowest water levels. A cluster analysis placed ectomycorrhizal morphotypes into three groups (Mycelium radicis-atrovirens Melin, Wilcoxina, and mixed) based on their treatment response, with all but two morphotypes in the mixed group whose abundance was maximized under conditions common to advanced seedling establishment. For maximal mycorrhization and root development of interior Douglas-fir seedlings, nurseries should minimize addition of nitrogen and phosphorus nutrients, maximize aeration, provide water at moderate rates, and, where possible, add small amounts of field soil to the growing medium.     

Effects of long-term nutrient optimisation on stem wood chemistry in Picea abies

The aim of the present study was to determine how long-term nutrient optimisation of Norway spruce stands affects the chemical composition of stem wood. Material for the study was collected from Flakaliden (Sweden) where Norway spruce [Picea abies (L.) Karst.] stands have been grown either without fertilisation or under nutrient optimisation treatment, by supplying a complete nutrient mix in the irrigation water every 2nd day during the growing season. The experiment was established in 1987 and in the autumn of 1998, 12 trees were harvested both in control (no fertilisation) and irrigated-fertilised (IL) stands. The increased growth rate caused by the IL treatment affected the chemical composition of the stem wood. The most pronounced effect was a 7% increase in lignin concentration caused by the IL treatment. Increases in concentrations of acid-soluble lignin (1.1-fold), extractives (1.2-fold), soluble sugars (1.3-fold), sterols (1.3-fold) and dehydroabietic acid (1.6-fold) as well as a decrease in the proportional quantity of terpinolene were also found. These results demonstrate that nutrient optimisation affected the chemical composition of Norway spruce wood, which may influence the suitability of such wood for specific end-use purposes.