Young Norway Spruce Trees Research Articles

Traces of Local Adaptive Acclimatization Response in the Tracheid Anatomical Traits between Dry and Wet Mesic Norway Spruce (Picea abies) Forests in Moravia, Czech Republic?

Norway spruce (Picea abies) forests in temperate zones are already reacting to short-term extreme summer heatwaves, threatening the vitality of trees and forest productivity, and can even lead to local and regional dieback events. Examining quantitative wood anatomy can provide helpful information in terms of understanding the physiology mechanisms and related responses of conifer trees to local environmental interactions in relation to tracheid adaptive capacity. This study analysed the tracheid functional anatomical traits (FATs) plasticity of six young Norway spruce trees growing in two mesic research plots with high annual precipitation (~43%) and air temperature differences during 2010–2017. The research plots are located in the sub-mountainous (Rájec Němčice) and mountainous (Bílý Kříž) belts of the Moravia region, Czech Republic. Vapour pressure deficit and cell wall reinforcement index (CWRI) were shown to be the most representative environmental parameters as proxies of dry conditions. Tracheid FATs indicated latewood phenological plasticity sensitivity, with more pronounced variability in the warmer and drier plots. Latewood tracheids of Norway spruce trees grown in the RAJ formed significantly thicker cell walls than BK during the studied period. The observed differences between the two research plots indicate additional support for tracheid cells’ hydraulic safety against cavitation and potential traces of adaptive acclimatization response.

Effects of combined drought and pathogen stress on growth, resistance, and gene expression in young Norway spruce trees.

Drought-induced mortality is a major direct effect of climate change on tree health, but drought may also affect trees indirectly by altering their susceptibility to pathogens. Here we report how a combination of mild or severe drought and pathogen infection affected growth, pathogen resistance, and gene expression in potted 5-year-old Norway spruce trees (Picea abies). After 5weeks of drought, trees were inoculated with the fungal pathogen Endoconidiophora polonica. Combined drought-pathogen stress over the next 8weeks led to significant reductions in growth of drought-treated trees relative to well-watered trees, and more so in trees subjected to severe drought. Belowground, growth of the smallest fine roots was most affected. Aboveground, shoot diameter change was most sensitive to the combined stress, followed by shoot length growth and twig biomass. Both drought-related and some resistance-related genes were upregulated in bark samples collected after five weeks of drought (but before pathogen infection), and gene expression levels scaled with the intensity of drought stress. Trees subjected to severe drought were much more susceptible to pathogen infection than well-watered trees or trees subjected to mild drought. Overall, our results show that mild drought stress may increase tree resistance to pathogen infection by upregulating resistance-related genes. Severe drought stress, on the other hand, decreased tree resistance. Because drought episodes are expected to become more frequent with climate change, combined effects of drought and pathogen stress should be studied in more detail to understand how these stressors interactively influence tree susceptibility to pests and pathogens.

Allometric models for estimating aboveground biomass of young Norway spruce trees in the Western Carpathians, Slovakia

Abstract In the period of climate change, it is necessary to have biomass models for trees of all sizes to make precise estimations of biomass forest stocks to quantify carbon sequestration by forest cover. Therefore, we created allometric models of aboveground biomass in young Norway spruce (Picea abies [L.] Karst.) trees including main components, i.e. stem, branches and needles. The models used 200 sampled trees from 10 sites located in the central part of the Western Carpathians in Slovakia. The models, i.e. allometric regression relations implemented stem base diameter (diameter d0) and/or tree height. Moreover, using the derived allometric relations and a constant annual diameter increment of 10 mm, we calculated quasi-annual aboveground biomass production with regard to diameter d0. While stem had the largest contribution to aboveground biomass, followed by needles and branches, a different situation was revealed for the annual aboveground biomass production with the largest share of needles followed by stem and branches. Finally, we implemented the allometric models in a specific forest stand, where repetitive measurements were performed within 14 consecutive years. The results showed for example nearly 650 kg of the aboveground biomass per 102 m2 at the stand age of 10 years. The new biomass models can be applied to estimate the aboveground biomass stock in Norway spruce dominating stands in the Western Carpathians. Since the models are based on both diameter d0 and tree height a user can choose which variable is more suitable for particular conditions.

Advances in understanding Norway spruce natural resistance to needle bladder rust infection: transcriptional and secondary metabolites profiling

BackgroundNeedle rust caused by the fungus Chrysomyxa rhododendri causes significant growth decline and increased mortality of young Norway spruce trees in subalpine forests. Extremely rare trees with enhanced resistance represent promising candidates for practice-oriented reproduction approaches. They also enable the investigation of tree molecular defence and resistance mechanisms against this fungal disease. Here, we combined RNA-Seq, RT-qPCR and secondary metabolite analyses during a period of 38 days following natural infection to investigate differences in constitutive and infection-induced defence between the resistant genotype PRA-R and three susceptible genotypes.ResultsGene expression and secondary metabolites significantly differed among genotypes from day 7 on and revealed already known, but also novel candidate genes involved in spruce molecular defence against this pathogen. Several key genes related to (here and previously identified) spruce defence pathways to needle rust were differentially expressed in PRA-R compared to susceptible genotypes, both constitutively (in non-symptomatic needles) and infection-induced (in symptomatic needles). These genes encoded both new and well-known antifungal proteins such as endochitinases and chitinases. Specific genetic characteristics concurred with varying phenolic, terpene, and hormone needle contents in the resistant genotype, among them higher accumulation of several flavonoids (mainly kaempferol and taxifolin), stilbenes, geranyl acetone, α-ionone, abscisic acid and salicylic acid.ConclusionsCombined transcriptional and metabolic profiling of the Norway spruce defence response to infection by C. rhododendri in adult trees under subalpine conditions confirmed the results previously gained on artificially infected young clones in the greenhouse, both regarding timing and development of infection, and providing new insights into genes and metabolic pathways involved. The comparison of genotypes with different degrees of susceptibility proved that several of the identified key genes are differently regulated in PRA-R, and that the resistant genotype combines a strong constitutive defence with an induced response in infected symptomatic needles following fungal invasion. Genetic and metabolic differences between the resistant and susceptible genotypes indicated a more effective hypersensitive response (HR) in needles of PRA-R that prevents penetration and spread of the rust fungus and leads to a lower proportion of symptomatic needles as well as reduced symptom development on the few affected needles.

Effect of two organic fertilizers on some anatomical features of Pinus pinea L. seedlings grown in field and lathe house

Effect of two organic fertilizers on some anatomical features of Pinus pinea L. seedlings grown in field and lathe house

Crown level clumping in Norway spruce from terrestrial laser scanning measurements

The clumping of coniferous needles into shoots is widely acknowledged as a structural feature that cannot be ignored in radiation regime models of coniferous forests. However, higher level clumping, i.e. the aggregation of leaves and shoots in tree crowns and forest stands, is still rarely accounted for in the models. Clumping reduces the light interception of and increases the light penetration depth in a plant stand. To improve forest radiation regime models with respect to this forest structural parameter, we propose a method that can quantify clumping at different hierarchical levels by estimating the silhouette to total area ratio from point clouds acquired by laser scanners. Our method is based on estimating attenuation coefficients in a voxel grid, and subsequently computing the total leaf area and spherically averaged silhouette area of a tree crown or forest stand. We tested our method with empirical data in young Norway spruce trees, where we compared leaf area and silhouette area to destructive and photogrammetric reference measurements. The accuracy of leaf area estimates depended strongly on the voxel size, with voxel sizes below 10 cm side length exhibiting up to 100% higher estimates than the reference leaf area, and large voxels with 90 cm side length being closest to the reference measurements due to crown clumping. The silhouette area estimates varied less with voxel size and were slightly higher than the reference estimates. We analyzed possible error sources and point out ways to improve the measurements of leaf and silhouette area for conifer trees using laser scanning data.

Crown architecture and structural development of young Norway spruce trees (Picea abies Karst.): A basis for more realistic growth modelling

The crown architecture and structural growth strongly affect the total volume and biomass of Norway spruce trees at a specific age. The main objective of this study was to explore the branching strategy of young spruce trees growing in a highly-dense naturally regenerated forest stand. The level of branching described by the Gravelius order of the growth units, as well as the unit’s branching direction and angles were analyzed. The significant factors that influence the occurrence frequency of growth units were the branching order and their life status. The results manifested the highest frequency of growth units in the first and second order in given conditions. A significant association between the branching direction of the mother unit and the first successive growth unit of higher order was revealed. Also, the mean branching angles were influenced by the branching order and relative position of the growth unit in relation to the mother unit. The branching angle distributions were left-skewed and the angles varied between 40° and 70°. The results improve our understanding of structural development of spruce crowns and can contribute to more realistic modeling of biomass production using tree growth simulators.

A comparative study of above- and below-ground parameters of healthy and declining young Norway spruce trees in a mountain area affected by air pollution

ABSTRACTThe aim of this study was to characterize possible connections between above- and below-ground parameters and the decline of Norway spruce trees in the Jeseníky Mountains of the Czech Republic – an area affected both by long-term air pollution and subjected to liming. A part of this study was dedicated to soil analysis, which showed considerable changes in the soil environment and highlighted particularly high concentrations of magnesium and calcium, exceeding optimal limits by as much as 8 and 13 times, respectively. Our results suggest that the decline of evaluated trees is primarily connected to root system development, as we found no differences between evaluated above-ground parameters for either healthy or declining trees. Tree decline related directly to low numbers of skeletal roots, root origin and higher maximal angles between skeletal roots. Declining trees had on average five skeletal roots with maximal angles between them of 173o, indicating poor mechanical stability. Regardless of tree vitality, 93% of all examined root systems were restricted to upper humus horizons with an average rooting depth of 10.2 cm. All evaluated trees showed severe root deformation into tangle, which suggests crucial influence of artificial planting on the architectural development of root systems.

Effects of prolonged drought on the anatomy of sun and shade needles in young Norway spruce trees.

Predicted increases in the frequency and duration of drought are expected to negatively affect tree vitality, but we know little about how water shortage will influence needle anatomy and thereby the trees' photosynthetic and hydraulic capacity. In this study, we evaluated anatomical changes in sun and shade needles of 20-year-old Norway spruce trees exposed to artificial drought stress. Canopy position was found to be important for needle structure, as sun needles had significantly higher values than shade needles for all anatomical traits (i.e., cross-sectional needle area, number of tracheids in needle, needle hydraulic conductivity, and tracheid lumen area), except proportion of xylem area per cross-sectional needle area. In sun needles, drought reduced all trait values by 10-40%, whereas in shade needles, only tracheid maximum diameter was reduced by drought. Due to the relatively weaker response of shade needles than sun needles in drought-stressed trees, the difference between the two needle types was reduced by 25% in the drought-stressed trees compared to the control trees. The observed changes in needle anatomy provide new understanding of how Norway spruce adapts to drought stress and may improve predictions of how forests will respond to global climate change.

Biomass allocation in natural regeneration of Fagus sylvatica and Picea abies trees in Italian Alps

Abstract Biomass allocation in seedlings and saplings at different stages of growth is important information for studying the response of species to site conditions. The objectives of the paper are: (a) to analyse the relationship between height and biomass in young Norway spruce and European beech trees, (b) to study the influence of the leaf area on ontogenetic growth stages and biomass sequestration capacity on the regeneration of these two species. 96 seedlings (H < 30 cm) and saplings (31 < H < 130 cm) were collected in different light conditions in a case study in the Alps (Trentino province, Italy). Leaf Area Index and shoot/root ratio were used as indicators of the ecological conditions (e.g. light, soil moisture, nutrient status) able to influence the seedlings and saplings growth. Two non-linear regressions were fitted to analyse the relationship between height and biomass and to develop the aboveground and below-ground allometric equations. Non-linear regressions show that sapling or seedling height is a good predictor of above-ground and below-ground biomass with a R2 aj above 0.8 for all equations and a R2 aj above 0.9 for above-ground biomass of Norway spruce. The results show that silvicultural practices may influence the regeneration patterns and increase the biomass allocation rate influencing stand density and canopy cover.

Lethal drought leads to reduction in nonstructural carbohydrates in Norway spruce tree roots but not in the canopy

Summary Heat waves and droughts are expected to increase in frequency and severity in many regions with future climate change, threatening the survival of a number of forest ecosystems. However, our understanding of the physiological processes and mechanisms underlying drought‐induced tree mortality is incomplete. Here, we present results on the physiological response of young Norway spruce trees exposed to lethal drought stress. We applied three levels of drought treatment (control, drying–rewetting, complete drought) and monitored relevant physiological functions and processes of carbon and water relations at high temporal resolution until tree death occurred. Only trees subjected to continuous drought died in our experiment. Trees subjected to drying–rewetting cycles consistently recovered in their ability to transport water, indicating that these trees do not suffer permanent damage to the hydraulic system. In all cases, drought reduced carbon assimilation, caused changes in carbon allocation and appeared to have severely reduced phloem functioning and carbon translocation. Structural growth was sacrificed for carbon investment in maintenance respiration and osmoprotection. Severe drought caused trees to rely on stored carbon reserves but, in contrast to above‐ground tissues, only root carbon pools were strongly reduced when trees died. Our results indicate that drought‐induced changes in carbon allocation, use and transport differ between above‐ and below‐ground tissues in trees. While root death may have been caused by carbon depletion, this was definitely not the case in above‐ground tissues. Our findings indicate that mortality mechanisms are not defined at the organism level but rather within tree compartments.

The effects of elevated atmospheric [CO2] on Norway spruce needle parameters

Studies of selected morphological needle parameters were carried out on young (17–19 year old) Norway spruce trees cultivated inside glass domes at ambient (A, 370 μmol (CO2) mol−1) and elevated (E, 700 μmol (CO2) mol−1) atmospheric CO2 concentrations [CO2] beginning in 1997. Annual analyses performed from 2002 to 2004 revealed higher values for needle length (especially for current needles, up to 18%) and projected needle area (up to 13%) accompanied by lower values for specific needle area (up to 15% lower, as quantified by needle mass to projected area ratio) in the E treatment compared to the A treatment. Statistically significant differences for most of the investigated morphological parameters were found in young needles in the well irradiated sun-adapted crown parts, particularly under water-limiting soil conditions in 2003. This was likely a result of different water relations in E compared to A trees as investigated under temperate water stress (Kuper et al. in Biol Plantarum 50:603–609, 2006). Furthermore, E trees had much higher absorbing root area, which modified and enhanced root:shoot as well as root:conductive stem area proportions. These hydraulic properties and early seasonal stimulation of photosynthesis forced advanced needle development in E trees, particularly under limited soil water conditions. The number of needles per unit shoot length was found to be unaffected by elevated [CO2].

Growth dynamics after historic disturbance in a montane forest and its implications for an endangered epiphytic lichen

Bolli J.C., Wagner H.H., Kalwij J.M., Werth S., Cherubini P., Scheidegger C. and Rigling A. 2008. Growth dynamics after historic disturbance in a montane forest and its implications for an endangered epiphytic lichen. Bot. Helv. 118: 111 – 127. Endangered forest species are often negatively affected by disturbances, which may have long-lasting effects on the distribution, abundance and genetic diversity of such species. To understand the effects of historic disturbances, detailed knowledge of the conditions for survival and recolonisation is needed, and this requires precise information on the perimeter and severity of historic disturbance events. We reconstructed a major historic disturbance (intensive logging followed by windthrow and fire in 1871) in the Swiss Jura mountains to analyse its effect on the disturbance-sensitive epiphytic lichen Lobaria pulmonaria. Tree-ring analysis of old and young Norway spruce trees (Picea abies L.), sampled systematically on a 100 m grid, revealed that (1) the disturbance was of intermediate severity, (2) a large, well-defined area of disturbance was created, and (3) an undisturbed zone remained in the centre of the disturbed area. Acomparison with lichen genetic data from a previous survey revealed that genetic diversity was particularly high in the remnant zone. These results suggest that the lichen survived there, and that it re-colonised the disturbed area both from the edge and from the remnant undisturbed zone. This illustrates that a detailed reconstruction of historic disturbances, as achieved with dendroecology, is very important for understanding the recolonisation process and thus, the conditions for the long-term persistence of disturbance-sensitive species in a dynamic landscape.

Biomass functions and expansion factors in young Norway spruce ( Picea abies [L.] Karst) trees

Roots, stems, branches and needles of 160 Norway spruce trees younger than 10 years were sampled in seven forest stands in central Slovakia in order to establish their biomass functions (BFs) and biomass expansion factors (BEFs). We tested three models for each biomass pool based on the stem base diameter, tree height and the two parameters combined. BEF values decreased for all spruce components with increasing height and diameter, which was most evident in very young trees under 1 m in height. In older trees, the values of BEFs did tend to stabilise at the height of 3–4 m. We subsequently used the BEFs to calculate dry biomass of the stands based on average stem base diameter and tree height. Total stand biomass grew with increasing age of the stands from about 1.0 Mg ha −1 at 1.5 years to 44.3 Mg ha −1 at 9.5 years. The proportion of stem and branch biomass was found to increase with age, while that of needles was fairly constant and the proportion of root biomass did decrease as the stands grew older.

Influence of stand density, thinning and elevated CO<sub>2</sub> on stem wood density of spruce

Stem wood density (SWD) of young Norway spruce trees (<i>Picea abie</I>s [L.] Karst.) growing at ambient (A variant, 350 µmol(CO<sub>2</sub>)/mol) and elevated (E variant, A + 350 µmol(CO<sub>2</sub>)/mol) atmospheric CO<sub>2</sub> concentration inside of the glass domes with adjustable windows was estimated after six and eight years of the cultivation. Stand density of two subvariants (s – sparse with ca 5,000 trees/ha and d – dense with ca 10,000 trees/ha) and thinning impact (intensity of 27%) on SWD and its variation along the stem vertical profile were investigated. After six years of CO<sub>2</sub> fumigation, stems of sparse subvariant had about 10% lower values of SWD comparing to dense ones, although the difference was not statistically significant. In 2004 (two years after thinning), the SWD values were higher in all subvariants along the whole stem vertical profile. This increase was more obvious in E variant (about 6% in d subvariant and only 3% in s subvariant). The highest increase of SWD values was found in Ed subvariant, particularly in the middle stem part (about 8%, statistically significant increase).

Stem radius changes and their relation to stored water in stems of young Norway spruce trees

Changes in the stem radius of young Norway spruce [Picea abies (L.) Karst.] were related to changes in stem water content in order to investigate the relationship between diurnal stem size fluctuations and internally stored water. Experiments were performed on living trees and on cut stem segments. The defoliated stem segments were dried under room conditions and weight (W), volume (V), and xylem water potential (Ψ s) were continuously monitored for 95 h. Additionally, photos of cross-sections of fresh and air-dried stem segments were taken. For stem segments we found that the change in V was linearly correlated to the change in W as long as Ψ s was >–2.3±0.3 MPa (phase transition point). Stem contraction occurred almost solely in the elastic tissues of the bark (cambium, phloem, and parenchyma), and the stem radius changes were closely coupled to bark water content. For living trees, it is therefore possible to estimate the daily contribution of "bark water" to transpiration from knowledge of the stem size and continuous measurements of the stem radius fluctuations. When Ψ s reaches the phase-transition point, water is also withdrawn from the inelastic tissue of the stem (xylem), which – in the experiment with stem segments – was indicated by an increasing ratio between Δ V and Δ W. We assume that for Ψ s below the transition point, air is sucked into the tracheids (cavitation) and water is also withdrawn from the xylem. Due to the fact that in living P. abies Ψ s rarely falls below –2.3±0.3 MPa and the xylem size is almost unaffected by radius fluctuations, dendrometers are useful instruments with which to derive the diurnal changes in the bark water contents of Norway spruce trees.

Long-term effects of a high nitrogen supply to soil on the growth and nutritional status of young Norway spruce trees

Central European forests are characterised by increasing N inputs. In a pot experiment with 3-year-old trees, the effects of varied N supply in soil (in mineral or organic form) on the growth and nutrient uptake of Norway spruce were examined over a period of 20 months. A nutrient-poor mineral forest soil was used in the experiment. N was added to the soil once, at the onset of the experiment. High mineral N supply (NH 4NO 3) decreased root growth and the root/shoot ratio of newly grown plant biomass, which resulted in wide N/P and N/K ratios in needles, and significantly decreased needle K concentrations. On the contrary, needle Ca concentrations were increased in plants with additional mineral N supply. The organic N form (keratin) slowly became available to plants, and also decreased the root/shoot ratio. In contrast to many observations in short-term experiments, the specific root length and the number of root tips per cm of root length were not affected by the soil N supply. High supply of mineral N did not cause visual symptoms of toxicity or damage in the plant. Induced cation or P deficiency may be a harmful consequence of high soil N levels, but will occur only when the soil supply of these nutrients is critically low.

Effect of nitrogen on the seasonal course of growth and maintenance respiration in stems of Norway spruce trees.

To determine effects of stem nitrogen concentration ([N]) on the seasonal course of respiration, rates of stem respiration of ten control and ten irrigated-fertilized (IL), 30-year-old Norway spruce trees (Picea abies (L.) Karst.), growing in northern Sweden, were measured on seven occasions from June 1993 to April 1994. To explore sources of seasonal variation and mechanisms of fertilization effects on respiration, we separated total respiration into growth and maintenance respiration for both xylem and phloem bark. Stem respiration increased in response to the IL treatment and was positively correlated with growth rate, volume of living cells and stem nitrogen content. However, no significant effect of IL treatment or [N] in the living cells was found for respiration per unit volume of live cells. Total stem respiration during the growing season (June to September) was estimated to be 16.7 and 29.7 mol CO(2) m(-2) for control and IL-treated trees, respectively. Respiration during the growing season accounted for approximately 64% of total annual respiration. Depending on the method, estimated growth respiration varied between 40 and 60% of total respiration during the growing season. Between 75 and 80% of the live cell volume in the stems was in the phloem, and phloem maintenance accounted for about 70% of maintenance respiration. Because most of the living cells were found in the phloem, and the living xylem cells were concentrated in the outer growth rings, we concluded that the best base for expressing rates of stem growth and maintenance respiration in young Norway spruce trees is stem surface area.

The effect of nutrition on the seasonal course of needle respiration in Norway spruce stands

Respiration of 1-year-old needles of 30-year-old Norway spruce trees [Picea abies (L.) Karst.] was studied in a nutrient optimisation experiment in northern Sweden. Respiration rates of detached needles, from ten control (C) and ten irrigated-fertilised (IL) trees, were measured on 16 occasions from June 1992 to June 1993. The aim of the study was to determine the influence of temperature on the seasonal course of needle maintenance respiration, and the effect of nitrogen concentration [N] and carbohydrate content on needle respiration in young Norway spruce trees subjected to long-term fertilisation. The IL treatment significantly affected needle size, in terms of dry mass and length, but not specific needle length (SNL). There was, however, a strong tree-specific effect on SNL (P<10–9, R2 = 0.75). Needle starch content varied markedly with season (0–25% of total dry mass). This, unless accounted for, would cause erroneous estimates of nutrient concentrations, and of rates of needle respiration, within and between treatments. There was considerable seasonal variation in needle respiration, both in terms of maintenance respiration and temperature dependence (Q10). Q10 had its highest value (2.8) during winter and its lowest (2.0) in the middle of summer. In early autumn (August, September), respiration rate and needle [N] were significantly related (C: P = 0.001, IL: P<0.0005). There was no significant difference in the slope between the two regression lines, but a difference in intercept. At the same needle [N], needles from IL-plots always had a lower respiration rate than needles from control plots. No obvious explanation for the observed difference in intercept was found, but some plausible assumptions are put forward and discussed.

Seasonal variation of maximum photochemical efficiency in boreal Norway spruce stands

The seasonal variation in maximum photochemical efficiency of photosystem II (Fv/Fm) and the relationship between Fv/Fm and climatic factors such as irradiance, frost-nights and daily mean temperature was studied in young Norway spruce trees for 4 years in northern Sweden. As a result of night frost, the Fv/Fm-ratio gradually decreased during the autumn. There was between-year variation in the pattern of Fv/Fm in fully exposed shoots during autumn and spring, largely as an effect of differing temperature conditions. During spring, there was a strong apparent relationship between daily mean temperature and Fv/Fm within the temperature range –3 to 12°C. The light regime to which the needles were exposed during winter affected Fv/Fm, and moderately shaded shoots from the bottom of the canopy generally had a higher Fv/Fm-ratio than fully exposed shoots from the top of the canopy.