Long-term exposure to enhanced UV-B radiation has no significant effects on growth or secondary compounds of outdoor-grown Scots pine and Norway spruce seedlings

The effects of long-term enhanced UV-B radiation on growth and secondary compounds of two conifer species were studied in an outdoor experiment. Scots pine (Pinus sylvestris) seedlings were exposed for two growing seasons and Norway spruce (Picea abies) seedlings for three growing seasons to supplemental UV-B radiation, corresponding to a 30% increase in ambient UV-B radiation. The experiment also included appropriate controls for ambient and increased UV-A radiation. Enhanced UV-B did not affect the growth of the conifer seedlings. In addition, neither the concentrations of terpenes and phenolics in the needles nor the concentrations of terpenes in the wood were affected. However, in the UV-A control treatment the concentrations of diterpenes in the wood of Scots pine decreased significantly compared to the ambient control. Apparently, a small increase in UV-B radiation has no significant effects on the secondary compounds and growth of Scots pine and Norway spruce seedlings.     

Trends in needle and soil chemistry of Norway spruce and Scots pine stands in South Sweden 1985-1994

The nutrient status of the trees and soil in 42 stands of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in Scania, South Sweden was followed from 1985 to 1994. Samples from needles taken in winter 1985, 1987, 1990, and 1994, and soils in 1988 and 1993 were analyzed. Concentrations, as well as ratios to N, of K and Cu in needles of both species decreased by approximately 40% from 1985 to 1994. Soil analyses indicate ongoing soil acidification and leaching of mineral nutrients from the soil profile. Together with deposition data and corroboration from modeled scenarios, these data support the recent contention that one consequence of enhanced deposition of N and S will be the development of nutrient imbalances in trees growing in southern Sweden.     

Response of needle sulphur and nitrogen concentrations of Scots pine versus Norway spruce to SO2 and NO2

The results of two field studies and an open-top chamber fumigation experiment showed that the response of mature Scots pine to SO(2) and NO(2) differed from that of mature Norway spruce. Moreover, the response of pine seedlings to SO(2) and NO(2) differed from that of mature trees. The greater increase in the needle total S concentrations of pine suggested more abundant stomatal uptake of SO(2) compared to spruce. Both pine seedlings and mature trees also seemed to absorb more N from atmospheric deposition. Mature pine was able to assimilate SO(4)(2-) derived from SO(2) into organic S more effectively than mature spruce at the high S and N deposition sites, whereas both pine and spruce seedlings accumulated SO(4)-S under NO(2)+SO(2) exposure. Spruce, in turn, accumulated SO(4)-S even when well supplied with N. Net assimilation of SO(4)(2-) in conifer seedlings was enhanced markedly by elevated temperature. To protect the northern coniferous forests against the harmful effects of S and N deposition, it is recommended that the critical level for SO(2) as a growing season mean be set at 5-10 microg m(-3) and NO(2) at 10-15 microg m(-3), depending on the 'effective temperature sum' and/or whether SO(2) and NO(2) occur alone or in combination.     

Effects of simulated rain acidity on ectomycorrhizae of red spruce seedlings potted in natural soil

Formation of ectomycorrhizae of red spruce (Picea rubens) grown in natural soil was measured after seedlings were exposed to 25 or 50 applications of simulated rain of pH 5.5, 3.5 or 2.5. Ectomycorrhizae were quantified as the total number of ectomycorrhizal tips per centimeter, and as the number of ectomycorrhizal tips for each morphotype and for Cenococcum geophilum. Rain solutions were applied to the soil alone, to foliage and stem alone, or to entire potted seedlings. Final soil pH was linearly related to rain solution acidity. Lower base saturation, calcium and zinc content, and higher exchangeable acidity were observed after pH 2.5 treatments if the soil was exposed. Rain solutions and the subsequent changes in soil characteristics did not affect the total numbers of ectomycorrhizal tips. Four morphotypes of ectomycorrhizae observed for these seedlings were unaffected by simulated rain. However, the numbers of ectomycorrhizal tips formed by C. geophilum tended to increase with rain solution acidity after 50 applications. Method of rain deposition did not affect ectomycorrhizae, suggesting both plant and soil mediated responses may favor certain mycobionts. The results of this study indicate that short-term acidic deposition does not induce significant changes in the frequency of ectomycorrhizae, but higher numbers of C. geophilum tips suggest there may be changes in the relative occurrence of specific morphotypes of fungus species.     

The tree species matters: Biodiversity and ecosystem service implications of replacing Scots pine production stands with Norway spruce

Ambio - The choice of tree species used in production forests matters for biodiversity and ecosystem services. In Sweden, damage to young production forests by large browsing herbivores is helping...     

Uptake,translocation and fate of trichloroacetic acid in a Norway spruce/soil system

Trichloroacetic acid (TCA) is a secondary atmospheric pollutant formed by photooxidation of chlorinated solvents in the troposphere--it has, however, recently been ranked among natural organohalogens. Its herbicidal properties might be one of the factors adversely affecting forest health. TCA accumulates rapidly in conifer needles and influences the detoxification capacity in the trees. The aim of the investigations--a survey of which is briefly given here--was to elucidate the uptake, distribution and fate of TCA in Norway spruce. For this purpose young nursery-grown plants of Norway spruce (Picea abies (L.) Karst.) were exposed to [1,2-14C]TCA and the fate of the compound was followed in needles, wood, roots, soil and air with appropriate radio-indicator methods. As shown by radioactivity monitoring, the uptake of TCA from soil by roots proceeded most rapidly into current needles at the beginning of the TCA treatment and was redistributed at later dates so that TCA content in older needles increased. The only product of TCA metabolism/biodegradation found in the plant/soil-system was CO(2) (and corresponding assimilates). TCA biodegradation in soil depends on TCA concentration, soil humidity and other factors.     

Gas chromatography-mass spectrometry analysis of dichlorophene used as a growth inhibitor in containerized seedlings of pine and spruce

Gas chromatography with a flame ionization detector and gas chromatography-mass spectrometry were employed in the analysis of dichlorophene used in the nursery cultivation of pine and spruce. The analysis was performed in paper and peat after the conversion of dichlorophene to its dimethyl other. With multiple ion detection a sensitivity of 1 mg/g paper or peat was achieved.     

Effects of copper deficiency and copper toxicity on organogenesis and some physiological and biochemical responses of Scots pine (Pinus sylvestris L.) seedlings grown in hydroculture

The morphological, physiological, and biochemical parameters of 6-week-old seedlings of Scots pine (Pinus sylvestris L.) were studied under deficiency (1.2 nM) and chronic exposure to copper (0.32, 1, 2.5, 5, and 10 μM CuSO₄) in hydroculture. The deposit of copper in the seed allowed the seedlings to develop under copper deficiency without visible disruption of growth. The high sensitivity of Scots pine to the toxic effects of copper was shown, which manifested as a significant inhibition of growth and development. The loss of dominance of the main root and a strong inhibition of lateral root development pointed to a lack of adaptive reorganization of the root system architecture under copper excess. A preferential accumulation of copper in the root and a minor translocation in aerial organs confirmed that Scots pine belongs to a group of plants that exclude copper. Selective impairment in the absorption of manganese was discovered, under both deficiency and excess of copper in the nutrient solution, which was independent of the degree of development of the root system. Following 10 μM CuSO₄ exposure, the absorption of manganese and iron from the nutrient solution was completely suppressed, and the development of seedlings was secured by the stock of these micronutrients in the seed. The absence of signs of oxidative stress in the seedling organs was shown under deficiency and excess of copper, as evidenced by the steady content of malondialdehyde and 4-hydroxyalkenals. Against this background, no changes in total superoxide dismutase activity in the organs of seedlings were revealed, and the increased content of low-molecular-weight antioxidants was observed in the roots under 1 μM and in the needles under 5 μM CuSO₄ exposures.

     

Trichloroacetic acid in Norway spruce/soil-system. I. Biodegradation in soil

Trichloroacetic acid (TCA) as a phytotoxic substance affects health status of coniferous trees. It is known as a secondary air pollutant (formed by photooxidation of tetrachloroethene and 1,1,1-trichloroethane) and as a product of chlorination of humic substances in soil. Its break-down in soil, however, influences considerably the TCA level, i.e. the extent of TCA uptake by spruce roots. In connection with our investigations of TCA effects on Norway spruce, microbial processes in soil were studied using 14C-labeling. It was shown that TCA degradation in soil is a fast process depending on TCA concentration, soil properties, humidity and temperature. As a result, the TCA level in soil is determined by a steady state between uptake from the atmosphere, formation in soil, leaching and degradation. The process of TCA degradation in soil thus participates significantly in the chlorine cycle in forest ecosystems.     

Clone and soil effects on the growth of young Norway spruce during 14 months exposure to ozone plus acid mist

Five clones of 3-year old Norway spruce (Picea abies [L.] Karst), planted in a soil from the Bavarian Forest (pH 4.4) or a soil from the Calcareous Bavarian Alps (pH 6.9), were exposed for two successive vegetation periods, in closed environmental chambers, to a pollution treatment consisting of acidic mist (pH 3.0) plus ozone levels of 100 microg m(-3) with episodes of 130-360 microg m(-3); control trees were exposed to mist of pH 5.6 and ozone levels of 50 microg m(-3). Climatic and pollution protocols followed the diurnal and seasonal pattern characteristic for the Inner Bavarian Forest in Southern Germany, an area affected by the new-type forest decline. Biometric parameters were strongly related to clone and soil. Pollution treatment had a limited effect on only a few growth parameters. The stem diameter growth increment of two clones was reduced by pollution treatment in both soils, a third clone was affected in the acidic soil only. Two other clones were not affected at all. Stem volume increment of three clones, calculated as D(2)H, was reduced by pollution treatment in the neutral soil, a fourth clone was affected in the acidic soil only. Bud break was either delayed (two clones) or accelerated (two other clones) by treatment. Depending on soil and clone, needle yellowing was observed in previous years' needles in both treatment and control trees exposed to increased light intensities. The 'spotted' yellowing was not identical to symptoms found in forest decline areas and was most likely a consequence of nutrient deficiencies during the vegetation period preceding the experiment. The results of this experiment are discussed with regard to field observations and forest productivity. The complex pattern of growth responses resulting from interactions between air pollution, soil and genetic factors is considered to reflect different susceptibilities of trees to air pollutants.     

Effect of simulated acid rain on quantity of epiphytic microfungi on Scots pine (Pinus sylvestris L.) needles

The effects of simulated acid rain on the phyllosphere microflora of pine (Pinus sylvestris L.) were studied experimentally in northern Finland during the summer of 1988. Trees were irrigated with artificial acid rain of pH4 and pH3 (H(2)SO(4) and HNO(3), weight ratio of S:N=2.86:1). Untreated trees and trees irrigated with spring water (pH6) were used as controls. Two sampling heights (0.5m and 2m) were used. The needles were colonized exclusively by epiphytic fungi, mainly Aureobasidium pullulans (de Bary) Arnaud. The lower branches had significantly more epiphytic fungi than the upper branches. Compared to the control trees, the numbers of epiphytic fungi were significantly decreased on the needles of trees irrigated with acid rain. Acid rain affected the number of epiphytic fungi equally at both sampling heights. The species composition of the epiphytic fungi was not affected by the acid treatments.     

Phytotoxicity of short-term exposure to excess zinc or copper in Scots pine seedlings in relation to growth,water status,nutrient balance,and antioxidative activity

The toxic effects of heavy metals pose a significant threat to the productivity and stability of forest ecosystems. Changes in the agrochemical properties of polluted forest soils due to global climate changes can increase the bioavailability of previously immobilized heavy metals. To test this hypothesis, we studied the effects of short-term shock exposure to ZnSO₄ (50, 150, 300 μM) or CuSO₄ (2.5, 5, 10 μM) in hydroculture on 4- to 6-week-old seedlings of Scots pine (Pinus sylvestris L.) with well-developed root systems. The effects of the excess heavy metals on mineral nutrients and the functioning of low-molecular-weight antioxidants and glutathione in protecting plants from oxidative damage were studied. Even short-term exposure to exogenous metals led to their rapid accumulation in the root system and their subsequent transport to aboveground organs. An increase in the 4-hydroxyalkenals content in seedling needles exposed to excess Cu led to an increase in the content of proanthocyanidins and catechins, which act as scavengers of reactive oxygen species. The impact of both metals led to the rapid development of mineral nutrient imbalances in the seedlings, which were most pronounced in the presence of excess Zn. Exposure to excess Zn led to a disruption in the translocation of Fe and a decrease in the Fe content in the needles. The most dramatic consequence of Zn exposure was the development of Mn deficiency in the roots, which was the likely cause of the inhibition of phenolic compound synthesis. A deficiency in phenolic compounds can have serious environmental consequences for pine populations that are at risk of contamination by Zn and Cu salts.

     

Effects of simulated acid rain on growth rate in a spruce-living spider

Growing juveniles of the spruce-living spider Pityohyphantes phrygianus were sprayed with water of different acidity--pH approximately 7 (control), 4.0 (acid rain) and 2.2-in a 2.5-month laboratory experiment. The growth rates did not differ between control and pH 4.0, while there was a significant growth reduction at pH 2.2. A low mortality occurred only in the pH 2.2 group. P. phrygianus seems to be resistant against acid rain although negative long-term effects cannot be ruled out.     

Effects of acid mist on mature grafts of Sitka spruce. Part I. Frost hardiness and foliar nutrient concentrations

Mature grafts of five clones of Sitka spruce (Picea sitchensis Bong. Sarg.) were exposed to simulated acid mist composed of an equimolar mixture of sulphuric acid and ammonium nitrate at pH 2.5 and pH 5.0 in open-top chambers from May to November 1991. Treatments were applied on consecutive days, four times a week. The pH 2.5 treatment provided an overall dose three times higher than that received by forests in upland areas of Britain. Frost hardiness was assessed in November by freezing detached current year shoots at a range of temperatures and assessing the rate of electrolyte leakage Foliar nutrient concentrations were determined on the same shoots. Acid mist at pH 2.5 significantly reduced frost hardiness in four of the five clones; the temperature causing 50% shoot death (LT50) was increased by 0 to 7 degrees C. The clones varied in their level of hardiness, one clone being exceptionally frost sensitive. The frost hardiness of the frost sensitive clone was found to be less perturbed by acid mist than the hardiness of the more frost resistant clones. Mature grafts showed a smaller reduction in hardiness at an equivalent dose than that found previously with Sitka spruce seedlings. Compared with seedlings, grafts had lower absolute concentrations of foliar sulphur. Exposure to acid mist at pH 2.5 increased %S in current year foliage by <0.05% compared with absolute increases of more than 0.10% in current year foliage of seedlings. We conclude that the effect of acid mist on frost hardiness is likely to be less on mature trees than on seedlings and that the increased frost risk to mature trees of Sitka spruce from occult deposition alone is small.     

The effect of simulated acid rain on the biochemical composition of Scots pine (Pinus sylvestris L.) needles

The effects of prolonged simulated acid rain on the biochemistry of Scots pine needles were studied in Finnish Lapland. Pine trees were exposed by spraying the foliage and soil with either clean water or simulated acid rain (SAR; both sulphuric and nitric acids) over the period 1985-1991. The concentrations of carbohydrates (starch, glucose, fructose, sucrose) in one-year-old pine needles were not affected by SAR-treatments. The SAR-treatments did not have significant effects on protein bound amino acids, which was true also for most of the free amino acids. However, the citrulline concentration was over three-fold greater in the foliage of pines exposed to SAR of pH 3 compared to irrigated controls. The concentrations of total phenolics, individual low molecular weight phenolics and soluble proanthocyanidins were not affected by the treatments, but insoluble proanthocyanidins had increased in acid-treated trees. Some of the studied biochemical compounds showed significant differences between two sub-areas (similar treatments) only 120 m apart.     

Root uptake of lead by Norway spruce grown on Pb spiked soils

The root uptake of lead (Pb) by trees and the transfer of Pb by leaf litter deposition to the forest floor were investigated through a pot experiment with Norway spruce. Natural Pb and radio isotopic lead (²¹⁰Pb) were determined in needles and twigs and in the pot soil spiked with ²¹⁰Pb. Calculations of the specific activity in plant material and in the supporting pot soil showed that less than 2% of the Pb content of needles and twigs originates from root uptake and approximately 98% are deposited from the atmosphere. Atmospheric Pb has declined by a factor of 7 from 1980 to 2007 but is still a major pathway of Pb to vegetation and topsoils. The conclusion from the experiment is that the internal circulation of Pb through root uptake, translocation and litterfall, gives an insignificant input of Pb to the forest floor compared to atmospheric deposition.     

Changes in the concentrations of phenolics and photosynthates in Scots pine (Pinus sylvestris L.) seedlings exposed to nickel and copper

Studies were done on the effects of elevated soil concentrations of copper (Cu) and (Ni) on foliar carbohydrates and phenolics in Scots pine (Pinus sylvestris L.). Four year-old seedlings were planted in pots filled with metal-treated mineral forest soil in early June. The experimental design included all combinations of four levels of Cu (0, 25, 40 and 50 mg kg(-1) soil dw) and Ni (0, 5, 15 and 25 mg kg(-1) soil dw). Current year needles were sampled for soluble sugar, starch and phenolics at the end of September. Ni increased sucrose concentration in the needles, indicating disturbances in carbohydrate metabolism. Trees exposed to Ni had higher concentrations of condensed tannins compared with controls. In contrast, concentrations of several other phenolic compounds decreased when seedlings were exposed to high levels of Cu or to a combination of Ni and Cu. The results suggest that concentrations of phenolics in Scots pine needles vary in their responses to Ni and Cu in the forest soil.     

Detection and localization of aluminum and heavy metals in ectomycorrhizal Norway spruce seedlings

Norway spruce seedlings colonized with Hebeloma crustuliniforme were grown in growth pouches. After formation of ectomycorrhizas, the seedlings were exposed to Al or the heavy metals Cd, Cu, Ni, or Zn at various concentrations for 5 weeks to estimate the detection limits of metals with X-ray microanalysis in the cryo-scanning electron microscope. When the lowest metal concentrations (1 mM Al(3+), 0.1 mM Cd(2+), 0.2 mM Cu(2+), 0.5 mM Ni(2+), 2 mM Zn(2+)) were applied, only Al and Zn were detected at low X-ray counts in the ectomycorrhizas. After application of 10-fold higher metal concentrations, distinct metal accumulation patterns were observed. Cd was detected predominantly in the Hartig net, Al and Ni in the Hartig net and in the cell walls of the cortex, and Zn in the Hartig net, the cortical cell walls and the fungal mantle. Cu was not detected at all. By combining X-ray microanalysis with absolute metal concentrations found in the roots, the estimated detection limits of X-ray microanalysis were: Al> or =0.86 mg g(-1), Cd> or =0.26 mg g(-1), Ni> or =1.30 mg g(-1), and Zn> or =0.54 mg g(-1), whereas Cu was not detectable even at root concentrations of 0.47 mg g(-1). Treatments with the highest metal concentrations showed high X-ray counts of metals in cells of the stele but reduced concentrations of the macronutrients K, Mg, and P in roots, indicating a possible disturbance of root and ectomycorrhizal function.     

Impact of ozone, acid mist and soil characteristics on growth and development of fine roots and ectomycorrhiza of young clonal Norway spruce

As part of the joint 14-month exposure experiment on Norway spruce (Picea abies (L.) Karst.) sensitivity to pollution (two levels of ozone plus acid mist) of growth and development of the fine-root system and of mycorrhizae, have been investigated in two forest soils from areas showing forest decline. This study shows that differences in fine-root biomass and the occurrence of species of ectomycorrhizae were mainly due to prevailing conditions within the acid or calcareous substrate. The pollution treatment resulted in higher numbers of short root tips in only one soil, whereas the percentage of ectomycorrhizal roots with a well-developed mantle was low (10-23%) in both soils, irrespective of exposure of trees to ozone and acid mist. There was no consistent response, with the two clones examined, in terms of mycorrhizal frequency, beaded short roots and renewed growth. Regarding the effects on root growth, data cannot be used unrestrictedly for extrapolation to a more complex field situation.