Identification of a RAPD marker linked to the pendula gene in Norway spruce (Picea abies (L.) Karst. f. pendula)

The pendula phenotype of Norway spruce [Picea abies (L.) Karst f. pendula] is characterized by narrow crowns and strong apical dominance and is controlled by a single dominant gene (P). This defined genetic control presents one of the few opportunities to map a single gene controlling a morphological trait in a forest tree. We used random amplified polymorphic DNA (RAPD) markers and bulked segregant analysis to identify one locus OPH10_720, linked to the pendula gene. The estimated recombination frequency (r) between OPH10_720 and P was 0.046 (SE _r =0.032). Mapping of the pendula gene is an important first step towards the ultimate identification and cloning of this gene.     

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.     

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.     

Seasonal accumulation of ultraviolet-B screening pigments in needles of Norway spruce (Picea abies (L.) Karst.)

Conifer needles are highly effective in screening ultraviolet-B radiation (280–320 nm). This ability is mainly attributed to the presence of flavonoids and hydroxycinnamic acids in the epidermal tissue. In two field cabinet experiments with two different clones of Norway spruce we assessed the seasonal accumulation of UV-B screening pigments under near-ambient, and close-to-zero UV-B irradiation. At the beginning of needle development, i.e. in June, kaempferol 3- O -glucoside was the dominant UV-B screening pigment. It was replaced during needle differentiation by the more effective diacylated flavonol glucosides, particulary kaempferol 3- O -(3",6"- O -di- p -coumaroyl)-glucoside, which reached highest concentrations in July. In addition to the soluble pool of diacylated flavonol glucoside derivatives, a cell wall-bound UV-B screen in the epidermal cell walls was formed during needle differentiation, consisting mainly of p -coumaric acid and kaempferol 3- O -glucoside. An effect of UV-B radiation on the accumulation of diacylated flavonol glucosides was only observed in 1996 with clone 2, when the concentrations of kaempferol 3- O -(3",6"- O -di- p -coumaroyl)-glucoside were significantly higher in July and August under field, and near-ambient than under close-to-zero UV-B irradiance. For wall-bound p -coumaric acid and kaempferol 3- O -glucoside UV-B radiation enhanced the concentrations of these compounds by approximately 20% in relation to the concentrations in close-to-zero UV-B-treated plants in both field cabinet experiments.     

Soil changes in different age classes of Norway spruce (Picea abies (L.) Karst.) on afforested farmland

The aim of this study was to test the hypothesis that afforestation changes the content and distribution of soil organic carbon, nutrients and pH in the A-horizon of land previously used in agriculture, and that such soil changes depend on stand development. The investigation was evaluated as a completely randomised design with three treatments representing different age classes of trees: 20 years (Y20), 40 years (Y40) and 55 years (Y55). Eighteen trial plots, six per treatment, were established in plantations of Picea abies (L.) Karst. on soils of similar texture and mineralogy. Tree volume was 220 m³ ha^-1 in Y20, 400 in Y40 and 440 m³ ha^-1 in Y55.Concentrations of carbon (C) and nitrogen (N) were significantly higher in the uppermost part of the soil in the older stands Y40 and Y55 than in Y20. The total amount of organic C in the litter layer plus the top 15 cm of the soil differed between age classes, with Y40 and Y55 having the largest amounts. A reference layer (15–20 cm) was used in calculating the amount of soil C that had accumulated in the horizon since afforestation, being about 10 tonnes ha^-1 of C in Y20 and 19 tonnes ha^-1 in Y40 and Y55.Cation exchange capacity (CEC) and base saturation (BS) was higher in the older stands. Carbon contents and CEC were strongly correlated. In Y40 and Y55, pH was significantly lower than in Y20 in the lower part of the soil horizon. There was a general decrease with depth of C, N, CEC, K⁺ and Mg²⁺ in the soil horizon. BS, Ca²⁺, Na⁺ and pH showed a somewhat different pattern of distribution, with deceasing values in the upper part of the soil horizon and increasing values in the lower part of the soil horizon.Abbreviations BD Bulk density - CEC cation exchange capacity - BS base saturation - Ca²⁺ calcium ion - Mg²⁺ magnesium ion - K⁺ potassium ion - Na⁺ sodium ion - C carbon - Ca _a accumulated carbon content - C _t total carbon content - N nitrogen - Y20 age class 20 years - Y40 age class 40 years - Y55 age class 55 years     

Conductance of needle and twig axis phloem of damaged and intact Norway spruce (Picea abies (L.) Karst.) as investigated by application of14C in situ

Summary Phloem conductance of¹⁴C-labelled assimilates was investigated in natural stands of Norway spruce showing substantial damage from needle yellowing and needle loss disease. Terminal current-year shoots of a branch were allowed to fix¹⁴CO₂ (300–600 ppm in air) and carbon dioxide net uptake was monitored with a gas analyser. The difference between¹⁴C-uptake and the amount of radiocarbon determined in the photosynthesizing needles was interpreted to reflect assimilate export from the needles to the axis of the tree. Compared with an undamaged control tree,¹⁴C-export from the assimilating needles was not impaired in the yellowing tree and only slightly reduced in the tree showing needle loss. Incorporation of¹⁴C into starch increased significantly during autumn particularly in the tree showing needle loss. Import of radiocarbon from the¹⁴C-labelled phloem sap in twig axes and needles older than 1 year was used as a measure of phloem conductivity of older sections of a branch which showed considerable damage. Carbon uptake by these older plant parts was more pronounced than in undamaged twigs. In the case of older needles enhancement of¹⁴C-incorporation suggested an increased sink strength, while the same phenomenon in the twig axes was interpreted as a consequence of partially impaired conductivity of individual sieve elements resulting in an inhomogeneous velocity of phloem transport. The hypothesis is put forward that curtailed viability of the sieve cells is responsible for a delay of transport, which is compensated for by an augmented production of phloem elements from the cambium.     

Structure and stand development in three subalpine Norway spruce (Picea abies (L.) Karst.) stands in Paneveggio (Trento, Italy)

1. Three permanent plots (100×0 m) were established in the subalpine Norway spruce (Picea abies (L.) Karst.) forest of Paneveggio in the spring of 1993, to begin a long-term forest ecosystem research project. The main purpose of these plots was to provide information about subalpine Norway spruce stand dynamics and to provide suggestions for close-to-nature silviculture. 2. The three stands were selected to represent the most common forest structures in the Paneveggio forest. The first stand is close to forestry roads, has a relatively regular and continuous canopy, and thinning and cutting operations only ended in the 1980s; the second stand is far from forest roads and has developed without anthropogenic influence for several decades; the third one is located at the present upper limit of the pure spruce forest and, apparently, was heavily used in the past as a pasture. 3. The first step in the investigation was to describe the structure and to study the history of the three stands using both written evidence from manage- ment plans and biological archives from tree rings. 4. The stands in plots 1 and 2 began to establish after a disturbance that removed part of the previous stands according to dendroecological studies, which are partially supported by written evidence. The remaining parts of these stands were eliminated by two major disturbances that occurred during the following decades. Written records about the use of the forest lead us to assume that the initial disturbances that occurred in the two stands were logging activities as a part of a group shelterwood system. The stand in plot 2 has developed without significant human interference for about half a century as confirmed by the presence of many dead trees. The stand in plot 3 consists of old trees that were part of an open stand and a secondary population that established after cessation of grazing. 5. The study has confirmed that dendroecological techniques can be used to identify occurrence and intensity of previous disturbance in forests stands, although at Paneveggio it is difficult to distinguish between natural and anthropogenic disturbances in the tree ring record. The presence of human activity necessitates investigation of multiple lines of evidence. 6. Paneveggio's forest management plans were useful in the interpretation of the data obtained through dendroecological analysis, although events did not always correspond because data from the management plans (yearly thinning, felling, wind-throw damage) never gave stand-level details, but applied to areas of several hectares. Despite these limitations, the information included in the management plans is of crucial importance in studying stand history and only by using all these sources of information is it possible to delineate the most important features of the history and disturbance that affected the origin and subsequent growth of the forest stands.     

Decomposition and nitrogen dynamics of fine roots of Norway spruce (Picea abies (L.) Karst.) at different sites

Long-term decomposition and nitrogen dynamics of Norway spruce finest (<1 mm in diameter) and fine (<2 mm in diameter) roots were estimated using the root litter-bag techniques. The seasonal decomposition of the finest roots was investigated in a 40-year-old high site quality stand grown on brown lessive soil at different depths as part of productivity studies. The fine root decomposition studies were conducted on 8 permanent plots in the Estonia with the aim to describe the site variation. The initial material was collected from one of stands (high quality site) and incubated at the depth of 10 cm in 1989 (at one site 1990). The bags were collected once or twice a year except for one site, where the seasonal dynamics was investigated. In all initial and decomposing root samples oven-dry weight, ash and energy content and nitrogen concentration was determined. After five years the finest roots had lost 40% of their initial dry weight, half of it during the first year. The initial concentration of nitrogen was 1.29%, the mean concentrations varied during the incubation from 1.47 to 1.78%. After the first year fine roots had lost 21.0 to 32.7% of their initial dry weight, after two years the weight loss was 22.5 to 43.2%. The initial N concentration in fine roots was 0.73% and in the first years it varied from 0.97 to 1.40% at different sites.     

Root distribution in a Norway spruce (Picea abies (L.) Karst.) stand subjected to drought and ammonium-sulphate application

Results of the spatial distribution of fine roots are reported from a Norway spruce (Picea abies (L.) Karst.) in SW Sweden stand subjected to drought (D) and ammonium-sulphate application (NS). The sampling was carried out by excavating monoliths in segments of 0.5 × 0.5 × 0.1 m to a depth of one meter. Root data also included in the study were obtained by excavating whole trees and soil coring.The data suggest a fairly deep distribution pattern of fine roots (< 1 mm in diameter) in the study area compared with other forest sites in SW Sweden. The weight fraction of living fine roots in the LFH-horizon amounted to 53, 36 and 55% of the total fine-root biomass and 12, 30 and 32% of the total fine-root necromass (dead fine roots) in the control, D and NS-treatment areas respectively. Drought seemed to result in a redistribution of fine roots to deeper mineral soil horizons. Ammonium sulphate application led to the reverse, viz, a concentration of fine roots to the LFH-horizon. A significantly smaller fine-root necromass was indicated in the LFH-horizon of the control areas compared with both the D and NS-treatment areas, suggesting a high mortality of fine roots in these areas. A heavy dry matter fraction accumulates in roots > 1 mm in diameter and in stumps. These root fraction, were frequently found between the trees, although the stump constitutes an important fraction in terms of dry weight.     

Temperature-respiration relationships differ in mycorrhizal and non-mycorrhizal root systems of Picea abies (L.) Karst

Root respiration has been shown to increase with temperature, but less is known about how this relationship is affected by the fungal partner in mycorrhizal root systems. In order to test respiratory temperature dependence, in particular Q (10) of mycorrhizal and non-mycorrhizal root systems, seedlings of PICEA ABIES (L.) Karst. (Norway spruce) were inoculated with the ectomycorrhizal fungus PILODERMA CROCEUM (Eriksson and Hjortstam, SR430; synonym: PILODERMA FALLAX: [Libert] Stalpers) and planted in soil respiration cuvettes (mycocosms). Temperature dependence of hyphal respiration in sterile cultures was determined and compared with respiration of mycorrhizal roots. Respiration rates of mycorrhizal and non-mycorrhizal root systems as well as sterile cultures were sensitive to temperature. Q (10) of mycorrhizal root systems of 3.0 +/- 0.1 was significantly higher than that of non-mycorrhizal systems (2.5 +/- 0.2). Q (10) of P. CROCEUM in sterile cultures (older than 2 months) was similar to that of mycorrhizal root systems, suggesting that mycorrhizae may have a large influence on the temperature sensitivity of roots in spite of their small biomass. Our results stress the importance of considering mycorrhization when modeling the temperature sensitivity of spruce roots.     

Nitrogen and drought effects on ectomycorrhizae of Norway spruce [Picea abies L.(Karst.)]

Effects of N addition and drought on ectomycorrhizae of Norway spruce trees were investigated in an outdoor pot lysimeter study. Three levels of N were applied as ammonium nitrate in irrigation water for five years; ambient rainwater (N0) and 5 (N5) and 15 (N15) times this N concentration. Mean annual N addition during the five years corresponded to 5, 27 and 82 kg·ha^-1·y^-1 for the N0, N5 and N15 treatments, respectively. During the third and fifth growth seasons two levels (lengths) of drought were artificially induced in addition to a watered control. Soil cores taken from each pot lysimeter were analyzed for mycorrhizal colonization and ectomycorrhizae were categorized according to macroscopic morphology. Drought decreased mycorrhizal colonization significantly. There was a significant interaction of drought and N effects on reduction of the mycorrhizal colonization. Although all of the mycorrhiza types were influenced by drought, only Cenococcum geophilum showed a significant change. N treatment alone did not show any significant effect either on mycorrhizal colonization or mycorrhizal types.     

Mineral nutrient imbalances and arginine concentrations in needles of Picea abies (L.) Karst. from two areas with different levels of airborne deposition

Summary This study evaluated the utility of free arginine concentrations as a possible alternative to mineral nutrient concentrations as an indicator of mineral nutrient imbalances in Norway spruce [Picea abies (L.) Karst.]. The concentrations of mineral nutrients and arginine were measured in the needles of spruce trees from two areas in Sweden, one with high (15–30 kg ha^–1 year^–1) airborne N deposition, and one with lower (1–4 kg ha^–1 year^–1) deposition. The spruce needles from the area with high deposition in southern Sweden had elevated concentrations of free arginine, especially on peat sites. No increase in concentrations was found in the low deposition area in northern Sweden. The arginine concentrations on different sampling occasions were consistent for each site and for individual trees. Trees on peat sites in the south seemed to suffer from P deficiency in relation to N availability. A tendency for K deficiency in needles from peat sites was also found. Needles from trees on mor plots showed acceptable levels of these nutrient elements. Sites in the northern area showed low N concentrations, but the ratios between the different mineral elements analyzed in this study and N were within ranges normally found. A low P/N ratio correlated to high free arginine concentration. The threshold for elevated arginine concentrations is crossed when P/N ratios drop below 0.07–0.08. A tendency for increased arginine levels when ratios between N and the other mineral elements are low was also found, although it was not as strong as that for the P/N ratio. The results are discussed in relation to mineral nutrient imbalances in spruce stands caused by airborne deposition.     

Crown development in Norway spruce [<Emphasis Type="Italic"> Picea abies </Emphasis>(L.) Karst.]

This study tests whether crown and stem development in Norway spruce could be described using a modified profile theory. 29 trees from three age-groups (25, 67, 86) with different treatments (unthinned, normally and intensively thinned) were destructively sampled. Crown ratio and crown length varied between age groups and treatments. Crown width was positively correlated with crown length, but branch length along the crown depended on tree age and growing space. Foliage mass density peaked at a relative crown height of 50–70% in middle-aged and mature stands, while young crowns were densest and widest at the base. Foliage mass was predictable from branch and stem cross-sectional area, provided the distance from the top was included. The ratio of foliage mass to branch cross-sectional area increased for 2–4 m down from the tip of the crown, then started to decrease. The relationship between cumulative foliage mass and stem cross-sectional area was non-linear along the stem in the upper crown, but the ratio of cumulative branch to stem cross-sectional area was linear. Trees in the mature and unthinned stands had more cross-sectional area in branches relative to stems than in the young and thinned stands. We conclude that the profile theory needs modification regarding (1) crown shape which varies with age and growing space, and (2) the ratio of foliage mass to branch area which varies along the stem. Both aspects emphasise the need to include impacts of disuse of sapwood pipes in models of crown and stem development.     

An attempt to predict long-term effects of atmospheric nitrogen deposition on the yield of Norway spruce stands (Picea abies (L.) Karst.) in southwestern Sweden

Long-term field experiments in Norway spruce stands on fertile sites (site indices 27–35 m) in southwestern Sweden were analysed with respect to volume increment. Three treatments were included (0=No fertilization, N = Fertilization with N, NP = Fertilization with N and P).Volume growth was monitored for 18 years in 10 blocks. No significant differences in annual volume increment between the treatments were detected. Volume increments in the N treatment were 97%, 99% and 107% as high as those in the 0 treatment for the periods 1–5, 6–10 and 11–15 years after the first fertilization. Corresponding values for the NP treatment were 104%, 108% and 110%, indicating that P has a small positive effect.The amount of N-fertilization would correspond to an annual N deposition of 20 kg ha^-1 during the next 30 years in southwestern Sweden. For this period, the results imply that this N deposition would not affect the growth of Norway spruce stands on fertile sites.     

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.