Early drought-induced changes to the needle proteome of Norway spruce

To elucidate early drought responses in needles of Norway spruce (Picea abies (Karst.) L.), we subjected 1-year-old seedlings to gradual desiccation for 6 weeks. Four weeks of drought treatment caused a small but significant decrease in photosystem II quantum yield of light-adapted needles (phi(a)) compared with that of well-watered controls. Six weeks of drought treatment reduced phi(a) and the photosystem II quantum yield of dark-adapted needles (phi) by 50 and 8%, respectively, and reduced shoot water potential by 0.7 MPa, but had no measurable effect on needle relative water content. After two weeks of drought treatment, and before there was a discernible effect of drought on phi or a statistically significant effect on shoot water potential, needles were analyzed for changes in protein composition. Five out of several hundred detected proteins in needles of drought-treated plants showed consistent changes compared with control leaves. The proteins were identified by LC-MS/MS as components of the oxygen-evolving complex (oxygen evolving enhancer protein 2), ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit, and one protein of unknown function, whose mRNA was found in a previous screen of wound- and methyl-jasmonate-induced bark proteins.     

Recovery of photosynthesis in 1-year-old needles of unfertilized and fertilized Norway spruce (Picea abies (L.) Karst.) during spring

Photosynthetic O(2) evolution and chlorophyll a fluorescence were measured in 1-year-old needles of unfertilized and fertilized trees of Norway spruce (Picea abies (L.) Karst.) during recovery of photosynthesis from winter inhibition in northern Sweden. Measurements were made under laboratory conditions at 20 degrees C. In general, the CO(2)-saturated rate of O(2) evolution was higher in needles of fertilized trees than in needles of unfertilized trees over a wide range of incident photon flux densities. Furthermore, the maximum photochemical efficiency of photosystem (PS) II, as indicated by the ratio of variable to maximum fluorescence (F(V)/F(M)) was higher in needles of fertilized trees than in needles of unfertilized trees. The largest differences in F(V)/F(M) between the two treatments occurred before the main recovery of photosynthesis from winter inhibition in late May. The rate of O(2) evolution was higher in needles of north-facing branches than in needles of south-facing branches in the middle of May. Simultaneous measurements of O(2) exchange and chlorophyll fluorescence indicated that differences in the rate of O(2) evolution between the two treatments were paralleled by differences in the rate of PS II electron transport determined by chlorophyll fluorescence. We suggest that, during recovery of photosynthesis from winter inhibition, the balance between carbon assimilation and PS II electron transport was maintained largely by adjustments in the nonphotochemical dissipation of excitation energy within PS II.     

Hydraulic and stomatal adjustment of Norway spruce trees to environmental stress

A study of how the water conducting systems of 30-50-year-old Norway spruce (Picea abies (L.) Karst.) trees growing at three sites adjust to shade and waterlogging indicated that water relations characteristics varied with the life histories of the trees. Xylem was more efficient at conducting water and stomata were more sensitive to atmospheric evaporative demand in trees subjected to favorable growth conditions (control trees) than in trees growing in shade or waterlogged conditions. At the same soil water availability, shade-grown trees suffered more severely from water deficit than control trees. Under conditions of high atmospheric vapor pressure deficit, foliage of shade-grown trees exhibited low water potentials, as a result of low hydraulic conductance of the vascular system and inefficient stomatal control. Because of the increased internal resistance to water flow, more negative leaf water potentials (Psi(x)) must be reached to provide an adequate water supply to the foliage. It is concluded that dynamic water stress is one of the main causes of the continuing growth retardation in suppressed Norway spruce trees after their release from the overstory. Trees growing in waterlogged soil (bog-grown trees) were characterized by weak stomatal control, resulting in large water losses from the foliage. Although bog-grown trees exhibited uneconomical water use, they possessed mechanisms (e.g., osmotic adjustment) that allowed leaves to tolerate low Psi(x) while stomata remained open. Under conditions of sufficient soil water availability and moderate atmospheric vapor pressure deficit, soil-to-leaf conductance was highest in bog-grown trees (1.45 +/- 0.06 mmol m(-2) s(-1) MPa(-1)), followed by control and shade-grown trees (1.04 +/- 0.04 and 0.77 +/- 0.05 mmol m(-2) s(-1) MPa(-1), respectively). The lowest soil-to-leaf conductance (0.45 +/- 0.04 mmol m(-2) s(-1) MPa(-1)) was recorded in control trees at high atmospheric evaporative demand, and was probably caused by tracheid cavitation.     

Association of Tiarosporella parca with needle reddening and needle cast in Norway spruce

Needles of Norway spruce turned red-brown in late fall and were consequently shed. On these needles fungal fruit bodies of Tiarosporella parca were found. This fungus could also be isolated from green needles of all ages.     

Basal area growth models for individual trees of Norway spruce, Scots pine, birch and other broadleaves in Norway

Distance-independent individual tree growth models based on about 30,000 observations from the National Forest Inventory and the Norwegian Forest Research Institute have been developed for the main tree species in Norway. The models predict 5-year basal area increment over bark for trees larger than 5 cm at breast height. Potential input variables were of four types: size of the tree, competition indices, site conditions, and stand variables including species, mixtures and layers. The squared correlation coefficient (R²) varied from 0.26 to 0.55. The accuracy of the models was tested by comparing the individual tree models with Norwegian diameter increment models. The accuracy is similar, but individual tree models forecast diameter distributions directly. The inclusion of species mixture and layer as variables increases the reliability of the models in mixed and in uneven-aged stands.     

Growth and carbon sequestration by ectomycorrhizal fungi in intensively fertilized Norway spruce forests

A substantial portion of the carbon (C) fixed by the trees is allocated belowground to ectomycorrhizal (EM) symbionts, but this fraction usually declines after fertilization. The aim of the present study was to estimate the effect of optimal fertilization (including all the necessary nutrients) on the growth of EM fungi in young Norway spruce forests over a three year period. In addition, the amount of carbon sequestered by EM mycelia was estimated using a method based on the difference in δ¹³C between C₃ and C₄ plants. Sand-filled ingrowth mesh bags were used to estimate EM growth, and similar bags amended with compost made from maize leaves (a C₄ plant) were used to estimate C sequestration. Fertilizers had been applied either every year or every second year since 2002 and the estimates of EM growth started in 2007. The application of fertilizer reduced EM growth to between 0% and 40% of the growth in the control plots at one site (Ebbegärde), while no significant effect was found at the other three sites studied. The effect of the fertilizer was similar in sand-filled and maize-compost-amended mesh bags, but the total production of EM fungi was 3-4 times higher in maize-compost-amended mesh bags. The fertilizer tended to reduce EM growth more when applied every year than when applied every second year. The amount of C sequestered in maize-compost-amended mesh bags collected from unfertilized treatments was estimated to be between 0.2 and 0.7 mg C g sand⁻¹ at Ebbegärde and between 0.2 and 0.5 mg C g sand⁻¹ at Grängshammar. This corresponds to between 300 and 1100 kg C per ha, assuming a similar production in the soil as in the mesh bags. Fertilization at the Ebbegärde site reduced carbon sequestration, which confirmed the results based on estimates of fungal growth (ergosterol levels). A correlation was found between fungal biomass and δ¹³C in mesh bags amended with maize compost. Based on this, it was estimated that a fungal production of 1 μg ergosterol corresponded to 0.33 mg of sequestered carbon. In conclusion, the effect of the fertilizer on EM growth seemed to be dependent on the effect of the fertilizer on tree growth. Thus, at Ebbegärde, were tree growth was less stimulated by the fertilizer, EM growth was reduced upon fertilization. At other sites, where tree growth was more stimulated, the fertilizer did not influence EM growth. The large amounts of carbon sequestered during the experiment may be a result of fungal residues remaining in the soil after the death of the hyphae.     

Carbon dioxide exchange in Norway spruce at the shoot, tree and ecosystem scale

Net CO2 exchange in a 35-year-old boreal Norway spruce (Picea abies (L.) Karst.) forest in northern Sweden was measured at the shoot (NSE), tree (NTE) and ecosystem levels (NEE) by means of shoot cuvettes, whole-tree chambers and the eddy covariance technique, respectively. We compared the dynamics of gross primary production (GPP) at the three levels during the course of a single week. The diurnal dynamics of GPP at each level were estimated by subtracting half-hourly or hourly model-estimated values of total respiration (excluding light-dependent respiration) from net CO(2) exchange. The relationship between temperature and total respiration at each level was derived from nighttime measurements of NSE, NTE and NEE over the course of 1 month. There was a strong linear relationship (r2 = 0.93) between the hourly estimates of GPP at the shoot and tree levels, but the correlation between shoot- and ecosystem-level GPP was weaker (r2 = 0.69). However, the correlation between shoot- and ecosystem-level GPP was improved (r2 = 0.88) if eddy covariance measurements were restricted to periods when friction velocity was > or = 0.5 m s(-1). Daily means were less dependent on friction velocity, giving an r2 value of 0.94 between shoot- and ecosystem-level GPP. The correlation between shoot and tree levels also increased when daily means were compared (r2 = 0.98). Most of the measured variation in carbon exchange rate among the shoot, tree and ecosystem levels was the result of periodic low coupling between vegetation and the atmosphere at the ecosystem level. The results validate the use of measurements at the shoot and tree level for analyzing the contribution of different compartments to net ecosystem CO2 exchange.     

Photosynthesis in Norway spruce seedlings infected by the needle rust Chrysomyxa rhododendri

Chrysomyxa rhododendri (DC.) De Bary is a needle rust with a host shift between Rhododendron sp. and Norway spruce (Picea abies (L.) Karst.), penetrating only the new developing flushes of the conifer. Because little is known about its effects on trees, we investigated several parameters related to photosynthesis in artificially infected 3-year-old Norway spruce seedlings. The potential efficiency of photosystem II (PSII; derived from chlorophyll fluorescence measurements) was reduced in infected current-year needles as soon as disease symptoms were visible, about three weeks after inoculation. Two weeks later, photosynthetic O(2) evolution (P(max)) of infected needles was less than 20% of control needles, whereas respiratory O(2) uptake (R(D)) was about three times higher than that of control needles. Nonstructural carbohydrate concentrations were about 60% of control values in all parts of the shoots of infected trees. Photosynthetic inhibition was associated with marked decreases in chlorophyll concentration and chlorophyll a/b ratio but only a small reduction in carotenoid concentration. In infected trees, P(max) of noninfected 1-year-old and 2-year-old needles was 50 and 80% higher than in the corresponding age class of needles of control trees. Estimation of potential daily net dry mass production, based on P(max), R(D), specific leaf area, carbon content and needle biomass, indicated that seedlings infected once were able to produce 60%, and those infected twice only 25%, of the dry mass of controls. We conclude that afforestation and regeneration of Norway spruce is seriously impaired in regions where seedlings are frequently attacked by Chrysomyxa.     

Occurrence of microorganisms in the wood of Norway spruce trees from polluted sites

Bacteria, yeasts and other fungi were isolated from stem and root wood of Norway spruee trees with disease symptoms and were identified in order to evaluate a possible mierobial involvement in the widespread tree decline in Central Europe.     

Fatty acids of ozone-exposed Scots pine and poplar trees and of damaged field-grown Norway spruce trees

In foliage of Pinus sylvestris, Populus euramericana, and Picea abies the fatty acid composition was analyzed. Whereas clonal material of pine and poplar in controlled ozone fumigations did not show any significant differences as compared to controls, such differences were obtained in fieldgrown spruces showing needle loss.     

Effects of ABA application on cessation of shoot elongation in long-day grown Norway spruce seedlings

Abscisic acid (ABA) was applied in lanolin to apical buds of Norway spruce (Picea abies (L.) Karst.) seedlings actively growing in a 24 h photoperiod. At a rate of 100 microg per plant, ABA suspended shoot elongation for about three weeks in the majority of plants but failed to induce normal winter buds. The role of ABA in the induction of dormancy is thus uncertain in conifers as well as in deciduous woody plants.     

Inventory of aspen trees in spruce dominated stands in conserva-tion area

Background: The occurrence of aspen trees increases the conservation value of mature conifer dominated forests.Aspens typically occur as scattered individuals among major tree species, and therefore the inventory of aspens is challenging.Methods: We characterized aspen populations in a boreal nature reserve using diameter distribution, spatial pattern, and forest attributes: volume, number of aspens, number of large aspen stems and basal area median diameter. The data were collected from three separate forest stands in Koli National Park, eastern Finland. At each site, we measured breast height diameter and coordinates of each aspen. The comparison of inventory methods of aspens within the three stands was based on simulations with mapped field data. We mimicked stand level inventory by locating varying numbers of fixed area circular plots both systematically and randomly within the stands. Additionally, we also tested if the use of airborne laser scanning(ALS) data as auxiliary information would improve the accuracy of the stand level inventory by applying the probability proportional to size sampling to assist the selection of field plot locations.Results: The results showed that aspens were always clustered, and the diameter distributions indicated different stand structures in the three investigated forest stands. The reliability of the volume and number of large aspen trees varied from relative root mean square error figures above 50% with fewer sample plots(5–10) to values of25%–50% with 10 or more sample plots. Stand level inventory estimates were also able to detect spatial pattern and the shape of the diameter distribution. In addition, ALS-based auxiliary information could be useful in guiding the inventories, but caution should be used when applying the ALS-supported inventory technique.Conclusions: This study characterized European aspen populations for the purposes of monitoring and management of boreal conservation areas. Our results suggest that if the number of sample plots is adequate,i.e. 10 or more stand level inventory will provide accurate enough forest attributes estimates in conservation areas(minimum accuracy requirement of RMSE% is 20%–50%). Even for the more ecologically valuable attributes, such as diameter distribution, spatial pattern and large aspens, the estimates are acceptable for conservation purposes.     

Dry mass production in seedlings of Norway spruce infected by the needle rust Chrysomyxa rhododendri

The aim of this study was to assess the losses in productivity of Norway spruce (Picea abies) due to the attack by Chrysomyxa rhododendri, a rust that only penetrates new developing flushes. Three-year-old seedlings were artificially infected once or twice in two consecutive years and the dry mass was determined at the end of the growing season. Dry mass accumulation of all parts including roots was significantly reduced if more than about one-third of the young foliage was infected. Shoot and root dry mass of once severely infected seedlings were 32 and 48% less than that of controls. This deficit could not be compensated during a following rust-free year. When seedlings were infected in two consecutive years, dry mass accumulation was reduced by 58% compared with controls. Results indicate that rejuvenation of and afforestation with Norway spruce can seriously be impaired by Chrysomyxa at the alpine timberline where Rhododendron sp. (the telial host of the parasite) is widespread.     

Relationships between crown projected area and components of above-ground biomass in Norway spruce trees in even-aged stands: Empirical results and their interpretation

Sample tree material was reanalyzed in order to study the relationships between horizontal crown projected area and components of above-ground biomass in Norway spruce (Picea abies (L.) Karst.) trees growing in even-aged stands. The needle mass of dominant trees increased linearly with the increase in crown projected area, but in co-dominant and dominanted trees the increase in needle mass levelled off toward larger crown projected areas. The branch mass of dominant and co-dominant trees accumulated faster than linearly with increasing crown projected area, whereas in dominated trees an approximately linear relationship existed between these two variables. The increase in needle and branch mass per unit increase in crown projected area was highest in dominant trees and decreased to co-dominant and dominated trees, i.e. with tree position in the canopy. The stem mass accumulated obviously faster than linearly and similarly in all tree classes with the increase in crown projected area. The narrow crown shape indicated a high density of all components of above-ground biomass per unit of crown projected area.     

Stand responses to initial spacing in Norway spruce plantations in Norway

Abstract

Using data from nine spacing experiments of Norway spruce (Picea abies (L.) Karst.) in Norway, covering wide ranges of site index and initial spacing, this study evaluated stand basal area and volume responses to initial spacing and examined whether these responses varied by stand ages or site quality. We developed nonlinear regression models that described the standing basal area or volume responses to initial spacing along with site index and stand ages. The results show that closer spacings produced higher standing basal area and volume than wider spacings. The response curves are highly nonlinear in younger stands and become nearly linear in mid-rotation stands, indicating stronger responses at younger ages and weaker responses as age increases. Furthermore, for young stands, spacing effects are stronger at closer than at wider spacings. The basal area and volume responses to initial spacing tend to be similar across site indices. However, the interaction of site index and stand age on spacing responses makes it difficult to isolate the effect of site index on spacing responses. Mortality is higher and begins earlier at closer spacings than wider. The mean diameter of the largest 100, 400, 600, and 800 trees ha^?1 increased with spacing in three out of the nine experiments. Dominant height did not vary by initial spacing for any of the experiments. The findings suggest that the extra volume production in stands of closer initial spacing is restricted to early stand development.     

Effects of elevated CO(2) concentration and nutrition on net photosynthesis,stomatal conductance and needle respiration of field-grown Norway spruce trees

To study the effects of elevated CO(2) on gas exchange, nonstructural carbohydrate and nutrient concentrations in current-year foliage of 30-year-old Norway spruce (Picea abies (L.) Karst.) trees, branches were enclosed in ventilated, transparent plastic bags and flushed with ambient air (mean 370 &mgr;mol CO(2) mol(-1); control) or ambient air + 340 &mgr;mol CO(2) mol(-1) (elevated CO(2)) during two growing seasons. One branch bag was installed on each of 24 selected trees from control and fertilized plots. To reduce the effect of variation among trees, results from each treated branch were compared with those from a control branch on the same whorl of the same tree. Elevated CO(2) increased rates of light-saturated photosynthesis on average by 55% when measured at the treatment CO(2) concentration. The increase was larger in shoots with high needle nitrogen concentrations than in shoots with low needle nitrogen concentrations. However, shoots grown in elevated CO(2) showed a decrease in photosynthetic capacity compared with shoots grown in ambient CO(2). When measured at the internal CO(2) concentration of 200 &mgr;mol CO(2) mol(-1), photosynthetic rates of branches in the elevated CO(2) treatments were reduced by 8 to 32%. The elevated CO(2) treatment caused a 9 to 20% reduction in carboxylation efficiency and an 18% increase in respiration rates. In response to elevated CO(2), starch, fructose and glucose concentrations in the needles increased on average 33%, whereas concentrations of potassium, nitrogen, phosphorus, magnesium and boron decreased. Needle nitrogen concentrations explained 50-60% of the variation in photosynthesis and CO(2) acclimation was greater at low nitrogen concentrations than at high nitrogen concentrations. We conclude that the enhanced photosynthetic rates found in shoots exposed to elevated CO(2) increased carbohydrate concentrations, which may have a negative feedback on the photosynthetic apparatus and stimulate cyanide-resistant respiration. We also infer that the decrease in nutrient concentrations of needles exposed to elevated CO(2) was the result of retranslocation of nutrients to other parts of the branch or tree.     

Radial distributions of Pb in stems of young Norway spruce trees grown in Pb-contaminated soil

Concentrations of Pb in individual stem xylem rings of 5-year-old Norway spruce trees (Picea abies (L.) Karst.) were determined after one growing season in soil containing a low, medium or high concentration of Pb. In trees in the control and low-Pb soil treatments, Pb concentrations increased from the outer annual rings toward the stem center, whereas in trees grown in the soil treatment containing a medium Pb concentration, all of the four tree rings analyzed contained similar concentrations of Pb. Although trees grown in the high-Pb soil treatment had higher concentrations of Pb in the outer annual rings than both control trees and trees in the low-Pb soil treatment, the highest concentrations of Pb were never observed in the outermost rings, which were formed during the period of exposure to increased soil Pb. We conclude that radial distribution patterns of Pb in Norway spruce stems do not directly reflect changes in soil Pb concentration but depend on several internal, physiological factors and, therefore, do not provide reliable information about past variations in Pb contamination of soil.     

Root and transpiration studies on young Norway spruce trees with die back symptoms in Sweden

In the spring of 1977, scattered trees in young plantations of Norway spruce showed discoloration and loss of 1976 needles on twigs just below the apex. The main roots of damaged trees were smaller than those of healthy trees, and the extension roots lacked short roots and mycorrhizae. The transpiration rate of the current shoots of damaged trees was also higher. The damage was assumed to be the result of drought during the two previous years; the trees were thought to differ genetically in their ability to withstand water stress.     

Influence of gaps on some selected tree characteristics of edge trees in Norway spruce plantations

The present study examined branch and stem characteristics of trees growing around gaps in Norway spruce plantations. Trees located at the edge of gaps with a radius of either 5 m or 7 m either unplanted or with supplementary planting were compared to trees in the original closed plantation. The experiment was carried out in two locations in the south of Sweden and the design included four blocks at each location and one replicate of each treatment in each block. The measurements were carried out on standing and felled trees in 2005 at the time of the first thinning. The results indicate a significant effect of gaps and supplementary planting on the diameter of the largest branch, the number of living branches close to breast height, branch basal area, height to the first living branch and taper. The effect of supplementary planting on branch and stem characteristics was greater in large gaps than in small ones. This study indicated that supplementary planting may be useful in affecting stem-form and branch parameters, although other studies have shown that the trees that result from supplementary planting contribute little to total production.     

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.