Seasonal Changes of Selected Parameters of CO2 Fixation Biochemistry of Norway Spruce Under the Long-Term Impact of Elevated CO2

Twelve-year-old Norway spruce (Picea abies [L.] Karst.) trees were exposed to ambient (AC) or elevated (EC) [ambient + 350 μmol(CO₂) mol^-1] CO₂ concentrations in open-top-chamber (OTC) experiment under the field conditions of a mountain stand. Short-term (4 weeks, beginning of the vegetation season) and long-term (4 growing seasons, end of the vegetation season) effects of this treatment on biochemical parameters of CO₂ assimilation were evaluated. A combination of gas exchange, fluorescence of chlorophyll a, and application of a mathematical model of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity was used. The analysis showed that the depression of photosynthetic activity by long-term impact of elevated CO₂ was mainly caused by decreased RuBPCO carboxylation rate. The electron transport rate as well as the rate of ribulose-1,5-bisphosphate (RuBP) formation were also modified. These modifications to photosynthetic assimilation depended on time during the growing season. Changes in the spring were caused mainly by local deficiency of nitrogen in the assimilating tissue. However, the strong depression of assimilation observed in the autumn months was the result of insufficient carbon sink capacity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Photosynthetic Assimilation of Sun versus Shade Norway Spruce [Picea abies (L.) Karst] Needles Under the Long-Term Impact of Elevated CO2 Concentration

The long-term impact of elevated concentration of CO₂ on assimilation activity of sun-exposed (E) versus shaded (S) foliage was investigated in a Norway spruce stand [Picea abies (L.) Karst, age 14 years] after three years of cultivation in two domes with adjustable windows (DAW). One DAW was supplied with ambient air [AC, ca. 350 µmol(CO₂) mol^–1) and the second with elevated CO₂ concentration [EC = AC plus 350 µmol(CO₂) mol^–1]. The pronounced vertical profile of the photosynthetic photon flux density (PPFD) led to the typical differentiation of the photosynthetic apparatus between the shaded and sun needles. Namely, photon-saturated values of maximal net photosynthetic rate (P _Nmax) and apparent quantum yield () were significantly higher/lower for E-needles as compared with the S-ones. The prolonged exposure to EC was responsible for the apparent assimilatory activity stimulation observed mainly in deeply shaded needles. The degree of this stimulation decreases in the order: S-needles dense part > S-needles sparse part > E-needles dense part > E-needles sparse part. In exposed needles some signals on a manifestation of the acclimation depression of the photosynthetic activity were found. The long-term effect of EC was responsible for the decrease of nitrogen content of needles and for its smoother gradient between E- and S-needles. The obtained results indicate that the E- and S-foliage respond differently to the long-term impact of EC.     

Long-Term Effects of Elevated CO2 on Woody Tissues Respiration of Norway Spruce Studied in Open-Top Chambers

In an open-top chamber experiment located in a mountain stand of 14-years-old Norway spruce (Picea abies [L.] Karst.), trees were continuously exposed to either ambient CO₂ concentration (A), or ambient + 350 µmol mol^–1 (E) over four growing seasons. Respiration rates of different woody parts (stem, branches, coarse roots) were measured during the last growing season. The calculated increase in the respiration rate related to a 10 °C temperature change (Q₁₀) was different in stem compared to branches and roots. Differences between the E and A variants were statistically significant only for roots in the autumn. Stem maintenance respiration (R_Ms) measured in April and November (periods of no growth activity) were not different. The stem respiration values (R_s) were recalculated to a standard temperature of 15 °C to estimate the seasonal course. The obtained R_s differed significantly between used variants during July and August. At the end of the season, R_s in E decreased slower than in A, indicating some prolongation of the physiological activity under the elevated CO₂ concentration. The total stem respiration carbon losses for the investigated growing season (May – September) were higher for A (2.32 kg(C) m^–2 season^–1) compared to E (2.12 kg(C) m^–2 season^–1). The respiration rates of the whorl branches (R_b) were lower compared with the stem respiration but not significantly different between the used variants. The root respiration rate was increased in E variant.     

Control Mechanisms of Photosynthetic Capacity Under Elevated CO2 Concentration: Evidence from Three Experiments with Norway Spruce Trees

Twelve-year-old Norway spruce (Picea abies [L.] Karst.) were exposed to ambient (AC) or elevated (EC) [ambient + 350 mol(CO₂) mol^–1] CO₂ concentration [CO₂] using the facilities of open-top-chambers (OTCs) and glass domes (GDs). A combination of gas exchange measurements and application of a biochemical model of photosynthesis were used for the evaluation of CO₂ assimilation characteristics. Morphological change was assessed on the base of specific leaf area (SLA). Nitrogen (N) content in the assimilation apparatus was considered a main factor influencing the biochemical capacity. Three experiments confirm the hypothesis that an adjustment of photosynthetic capacity under EC is controlled by the combination of biochemical, morphological, and physiological feedback mechanisms. We observed periodicity of down-regulation of photosynthetic capacity (Experiment No. 1) during the vegetation seasons. In the spring months (May–June), i.e. during the occurrence of active carbon sink associated with the formation of new foliage, up-regulation (10–35 %) of photosynthetic capacity (P _Nsat) was observed. On the contrary, in the autumn months (September–October) down-regulation (25–35 %) of P _Nsat was recorded that was mainly associated with reduced carbon sink strength and biochemical change, i.e. decrease of N status (up to 32 %) and accumulation of saccharides (up to 72 %) in leaves. Different adjustments of photosynthetic activities were observed in current (C) and one-year-old (C-1) needles exposed to EC (Experiment No. 2). Strong down-regulation of P _Nsat and the diminution of the initial stimulation of photosynthetic rate (P _Nmax) was associated with decreases of both ribulose-1,5-bisphosphate carboxylase/oxygenase carboxylation activity (by 32 %) and RuBP regeneration (by 40 %). This performance was tightly correlated with the absence of active carbon sinks, decrease of N content, and starch accumulation in C-1 needles. Finally, different responses of sun- and shade-adapted needles to EC (Experiment No. 3) were associated with the balance between morphological and biochemical changes. Observed P _Nsat down-regulation (by 22 %) of exposed needles in EC was predominantly caused by effects of both higher assimilate accumulation and stronger N dilution, resulting from higher absolute photosynthetic rates and incident irradiances in the upper canopy.     

Chlorophyll a Fluorescence Response of Norway Spruce Needles to the Long-Term Effect of Elevated CO2 in Relation to Their Position Within the Canopy

The long-term impact of elevated CO₂ concentration on photosynthetic activity of sun-exposed (E) versus shaded (S) foliage was investigated in a Picea abies stand (age 12 years) after three years of cultivation in adjustable-lamella-domes (ALD). One ALD is supplied with either ambient air [ca. 350 µmol(CO₂) mol^–1; AC-variant) and the second with elevated CO₂ concentration [ambient plus 350 µmol(CO₂) mol^–1; EC-variant). The pronounced vertical profile of the photosynthetically active radiation (PAR) led to the typical differentiation of the photosynthetic apparatus between the S- and E-needles in the AC-variant estimated from the irradiance-responses of various parameters of the room temperature chlorophyll (Chl) a fluorescence parameters. Namely, electron transport rate (ETR), photochemical efficiency of photosystem 2, PS2 (_PS2), irradiance-saturated values of non-photochemical quenching of minimum (SV₀) and maximum (NPQ) fluorescence levels, and photochemical fluorescence quenching (q_p) at higher irradiances were all significantly higher for E-needles as compared with the S-ones. The prolonged exposure to EC did not cause any stimulation of ETR for the E-needles but a strongly positive effect of EC on ETR was observed for the S-needles resulting in more than doubled ETR capacity in comparison with S-needles from the AC-variant. For the E-needles in EC-variant a slightly steeper reduction of the _PS2 and q_p occurred with the increasing irradiance as compared to the E-needles of AC-variant. On the contrary, the S-needles in EC variant revealed a significantly greater capacity to maintain a high _PS2 at irradiances lower than 200 µmol m^–2 s^–1 and to prevent the over-reduction of the PS2 reaction centres. Moreover, compared to the AC-variant the relation between SV₀ and NPQ exhibited a strong decrease (up to 72 %) of the SV₀-NPQ slope for the E-needles and an increase (up to 76 %) of this value for the S-needles. Hence the E- and S-foliage responded differently to the long-term impact of EC. Moreover, this exposure was responsible for the smoothing of the PAR utilisation vertical gradient in PS2 photochemical and non-photochemical reactions within the canopy.     

Acclimation of Photosystem 2 Function of Norway Spruce Induced during First Season under Elevated CO2 in Lamellar Domes

Since July 28^th, 1997 the two experimental mini-stands of young Norway spruce [Picea abies (L.) Karst.] have been grown in lamellar domes at ambient (AC) and elevated concentrations of CO₂ [EC, i.e., ambient + 350 µmol(CO₂) mol^–1]. Before the start of exposure to EC (June 1997) the dependencies of photosystem 2 (PS2) quantum yield (Y) on irradiance, estimating the efficiency of PPFD utilisation in PS2 photochemistry, were the same for AC and EC shoots. After one month of EC simulation (August 1997), Y values were higher for EC needles as compared with the AC ones (by 1–42 %), whereas two months later (October 1997) an opposite effect was observed (decrease of Y by from 1 to 33 %). By chlorophyll a (Chl a) fluorescence induction the effects of EC on PS2 function were further characterised. During the first month a moderate improvement of PS2 function was estimated for EC needles from slightly higher potential yield of PS2 photochemistry (F_V/F_M, by 1 %) and reduced amount of inactive PS2 reaction centres (relative F_p1 level, by 15 %). However, the prolonged exposure to EC led firstly to a slight but significant decrease of F_V/F_M (by 3 %), secondly to a reduction of half time of fluorescence rise (t_1/2, by 14 %), and finally to pronounced accumulation of inactive PS2 reaction centres (by 41 %). From the gradual response of individual Chl a fluorescence parameters we suggest a probable sequence of events determining the stimulation and subsequent depression of PS2 function for Norway spruce during the first season under EC.     

Impact of In-Situ CO2 Nano-Bubbles Generation on Freezing Parameters of Selected Liquid Foods

The impact of in-situ CO₂ nano-bubbles generation on the freezing properties of soft serve, milk, and apple juice was investigated. Carbonated (0, 1000, and 2000 ppm) liquid foods contained in a tube were submerged and cooled for 90 min in a pre-set ethylene glycol bath (−15 °C). Before the enclosed liquid reached 0 °C, the vibration was discharged through ultrasound in the bath to create nano-bubbles within the carbonated food samples, and the changes in temperature for 90 min of each food were recorded as a freezing curve. The time for onset of nucleation of control soft serve mix was halved in samples with 2000-ppm CO₂ due to the presence of nano-bubbles. Likewise, the nucleation time for milk with and without nano-bubbles at the same CO₂ concentration of 2000 ppm was 7.9 ± 0.1 and 2.8 ± 0.8 min_, respectively. The generation of CO₂ nano-bubbles from 2000-ppm CO₂ level in 10 ^oBx apple juice displayed −9.3 ± 0.3 °C nucleation temperature while the control one had −11.7 ± 0.9 °C.

     

Effect of Norway Spruce Planting Density on Shoot Morphological Parameters

Temporal and spatial variations of shoot structural parameters, including shoot silhouette to projected needle area ratio, are very important, e.g., for the correction of leaf area index estimated by indirect methods. Here we bring few examples of their evolution within mountain spruce monoculture planted in two different densities.     

Accumulation of a Metallothionein-like mRNA in Norway Spruce Under Environmental Stress

Differential screening of a Norway spruce ( Picea abies L., Karst) cDNA library with probes from damaged and symptomless trees identified a cDNA clone of a 650 nt metallothionein-like (MTL) mRNA as damage-related. Northern blot analysis revealed an about six-fold increase of the MTL mRNA in damaged trees in 1 year and a two-fold increase in the consecutive year. In the N-terminal domain this MTL mRNA comprises typical CysXCys motifs of a subgroup of class II MTL proteins found in kiwi and a few other plant species. In the C-terminal domain, however, the Norway spruce MTL protein is different to the kiwi subgroup and also distinct from a novel Douglas fir metallothionein-related protein, respectively. Hence, the cDNA identified during this study may represent a new type of MTL protein in plants. The accumulation of this MTL mRNA in needles of trees growing in an area of high ozone, sulphur dioxide and nitrogen oxide input and showing clear symptoms of forest decline may be a senescence effect or may play a role in the metal-mediated regulation of the intracellular activated oxygen concentration.     

Changes in Sulfur Metabolism During Needle Development of Norway Spruce*

In a field-study with approx. 150-year-old spruce trees, seasonal changes in thiol composition and content, sulfate content, and oxtractable activities of enzymes of sulfate reduction and assimilation were analyzed in needles and buds and were related to developmental processes during flushing. GSH was the predominant thiol in spruce needles throughout the year, with maximum contents of more than 400nmol g FW^?1 during winter and minimum contents of less than 200 nmol g FW^?1 during summer. Negative correlation of changes in GSI1 contents during winter and spring with air temperature showed a low correlation coefficient (r =– 0.55), suggesting minor significance of GSH in frost protection. Drastic changes in thiol contents during flushing suggested that GSH accumulated in the previous year's needles during winter supports the growing needles with reduced sulfur. Sulfate and other substrates for sulfate assimilation appeared to be available in buds and the new needles. An external supply with reduced sulfur may still be required because of insufficient activities of enzymes of sulfate reduction and assimilation, esp. ATP-sulfurylase and APS-sulfotransferase.     

Different Responses of Norway Spruce Needles from Shaded and Exposed Crown Layers to the Prolonged Exposure to Elevated CO2 Studied by Various Chlorophyll a Fluorescence Techniques

The acclimation depression of capacity of photon utilisation in photochemical reactions of photosystem 2 (PS2) can develop already after three months of cultivation of the Norway spruces (Picea abies [L.] Karst.) under elevated concentrations of CO₂ (i.e., ambient, AC, + 350 µmol(CO₂) mol^–1 = EC) in glass domes with adjustable windows. To examine the role that duration of EC plays in acclimation response, we determined pigment contents, rate of photosynthesis, and parameters of chlorophyll a fluorescence for sun and shade needles after three seasons of EC exposure. We found responses of shaded and exposed needles to EC. Whereas the shaded needles still profited from the EC and revealed stimulated electron transport, for the exposed needles the stimulation of both electron transport activity and irradiance saturated rate of CO₂ assimilation (P _Nmax) under EC already disappeared. No signs of the PS2 impairment were observed as judged from high values of potential quantum yield of PS2 photochemistry (F_V/F_M) and uniform kinetics of Q_A reoxidation for all variants. Therefore, the long-term acclimation of the sun-exposed needles to EC is not necessarily accompanied with the damage to the PS2 reaction centres. The eco-physiological significance of the reported differentiation between the responses of shaded and sun exposed needles to prolonged EC may be in changed contribution of the upper and lower crown layers to the production activity of the tree. Whereas for the AC spruces, P _Nmax of shaded needles was only less than 25 % compared to exposed ones, for the EC spruces the P _Nmax of shaded needles reached nearly 40 % of that estimated for the exposed ones. Thus, the lower shaded part of the crown may become an effective consumer of CO₂.     

Effects of Elevated CO2 and Simulated Seasonal Changes in Temperature on the Species Composition and Growth Rates of Pasture Turves

Large turves from a ryegrass/white clover based pasture wereexposed to 350 or 700 µl l^-1 CO₂ for a period of 217 din controlled environment rooms. The temperature was increasedduring the experiment from 10/4 °C day/night to 16/10 °Cand finally to 22/16 °C. The turves were cut to a heightof 2 cm at intervals and growth rates calculated from the regrowth. Growth rates over the duration of the experiment were 8% higherat elevated CO₂; the difference between CO₂ treatments beingstatistically significant only at the highest temperature. Speciescomposition of the turves at 350 µl l^-1 CO₂ showed seasonalchanges similar to those measured in the field. The effect ofCO₂ was to exaggerate the normal decline of ryegrass at warmertemperatures and increase the proportion of white clover. About30% of the total growth rate was from other species (notablyBromus hordeaceus L. and Poa trivialis L.) and this fractionwas similar between CO₂ levels. Root mass was measured at theend of the experiment and was 50% higher at elevated CO₂. The modest above-ground response to CO₂ was a result of CO₂stimulation occurring only at the higher temperature. Becauseof the CO₂ x temperature interaction, the effect of CO₂ in temperateregions will be seasonal. When this is matched with seasonalgrowth patterns of herbage species, a complex response of pasturecommunities to CO₂ is possible. In our case, white clover wasgrowing most strongly during the period of greatest CO₂ stimulationand consequently its growth was enhanced more than that of ryegrass;however, the cooler season growth of ryegrass gives it a temporalniche which is little affected by CO₂ and this may be importantfor ryegrass stability if it is an inherently poor responderto CO₂. The results indicate that for temperate species theeffects of competition at elevated CO₂ cannot be easily determinedfrom experiments conducted at a single temperature.Copyright1994, 1999 Academic Press CO₂ enrichment, seasonal growth, species composition, turves, Trifolium repens L., Lolium perenne L., climate change     

Carbon Balance of a Winter Wheat-Root Microbiota System Under Elevated CO2

We examined the carbon budget of young winter wheat plants and their associated microorganisms as affected by a doubling of the atmospheric CO₂ concentration (700 μmol mol^-1). Plants were grown hydroponically in pre-sterilised sand at a controlled irradiance and temperature regime. Net photosynthesis (P_N) and respiration (R_D) rates of roots and shoots were measured continuously, plant growth and carbon distribution in the plant-root medium-associated microorganism system were determined destructively in interval-based analyses. P_N in elevated CO₂ grown plants (EC) was 123% of that in the control (AC) plants when averaged over the whole life span (39-d-old plants, 34 d in EC), but the percentage varied with the developmental stage being 115, 88, and 167% in the pretillering, tillering, and posttillering phase, respectively. There was a transient depression of P_N, higher amplitude of day/night fluctuations of the chloroplast starch content, and depression of carbon content in rhizosphere of EC plants during the period of tillering. After 34 d in EC, carbon content in shoots, roots, and in rhizodepositions was enhanced by the factors 1.05, 1.28, and 1.96, respectively. Carbon partitioning between above and belowground biomass was not affected by EC, however, proportionally more C in the belowground partitioning was allocated into the root biomass. Carbon flow from roots to rhizodepositions and rhizosphere microflora was proportional to P_N; its fraction in daily assimilated carbon decreased from young (17%) to order (3-4%) plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Seasonal variation in CO2 efflux of stems and branches of Norway spruce trees

BACKGROUND AND AIMS: Stem and branch respiration, important components of total forest ecosystem respiration, were measured on Norway spruce (Picea abies) trees from May to October in four consecutive years in order (1) to evaluate the influence of temperature on woody tissue CO2 efflux with special focus on variation in Q10 (change in respiration rate resulting from a 10 degrees C increase in temperature) within and between seasons, and (2) to quantify the contribution of above-ground woody tissue (stem and branch) respiration to the carbon balance of the forest ecosystem. METHODS: Stem and branch CO2 efflux were measured, using an IRGA and a closed gas exchange system, 3-4 times per month on 22-year-old trees under natural conditions. Measurements of ecosystem CO2 fluxes were also determined during the whole experiment by using the eddy covariance system. Stem and branch temperatures were monitored at 10-min intervals during the whole experiment. KEY RESULTS: The temperature of the woody tissue of stems and branches explained up to 68% of their CO2 efflux. The mean annual Q10 values ranged from 2.20 to 2.32 for stems and from 2.03 to 2.25 for branches. The mean annual normalized respiration rate, R10, for stems and branches ranged from 1.71 to 2.12 micromol CO2 m(-2)s (-1) and from 0.24 to 0.31 micromol CO2 m(-2) s(-1), respectively. The annual contribution of stem and branch CO2 efflux to total ecosystem respiration were, respectively, 8.9 and 8.1% in 1999, 9.2 and 9.2% in 2000, 7.6 and 8.6% in 2001, and 8.6 and 7.9% in 2002. Standard deviation for both components ranged from 3 to 8% of the mean. CONCLUSIONS: Stem and branch CO2 efflux varied diurnally and seasonally, and were related to the temperature of the woody tissue and to growth. The proportion of CO2 efflux from stems and branches is a significant component of the total forest ecosystem respiration, approx. 8% over the 4 years, and predictive models must take their contribution into account.     

Diurnal Changes in Photosynthesis,Sugars, and Nitrogen of Wheat and Mungbean Grown Under Elevated CO2 Concentration

The diurnal changes in leaf net photosynthetic rate (P _N) and sugar and nitrogen contents in wheat [Triticum aestivum (L.) cv. HD 2285] and mungbean [Vigna radiata (L.) Wilczek cv. PS 16] were analysed under ambient, AC [350±25 µmol mol^–1] and elevated, EC [600±50 µmol mol^–1] CO₂ concentrations. In both mungbean and wheat P _N of AC- and EC-grown plants compared at the same CO₂ concentration showed that P _N was higher under EC. However, increased P _N in EC-plants declined in the afternoon and approached P _N of AC-plants. Depression in P _N, however, was less in mungbean compared with the large depression in wheat. Greater down regulation of P _N in wheat was associated with the accumulation of large amount of sugars and low nitrogen content in wheat leaves. Mungbean leaves accumulated mostly starch under EC and the difference in N content in AC- and EC-plants was relatively less than in wheat.     

Temporal and Nutritional Influences on the Response to Elevated CO2 in Selected British Grasses

To investigate the duration of the CO₂ response and its interactionwith mineral nutrition, CO₂-enrichment experiments were performedon four British grasses of differing ecology and functionaltype: Arrhenatherum elatius (L.) Beauv., Festuca ovina L., Festucarubra L. and Poa annua L. Naturally-lit, glasshouse cabinetswere used, with a non-limiting water supply and a daytime meantemperature of 18 °C. Two CO₂ treatments were maintainedat nominal concentrations of 350 and 700 vpm and were combinedfactorially with two levels of balanced mineral nutrition atconductivities of 0·1 and 1 mS cm^-1. Harvests took placeat planting-out, and at 16, 37 and 58 d thereafter. Fitted curves were used to derive instantaneous values of totaldry weight, relative growth rate (RGR), shoot weight fraction(SWF) and unit shoot rate (USR) for all combinations of species,CO₂ level, nutrient level and time of harvesting. At the higher nutrient level there was a reasonably close agreementwith previous estimates of the CO₂ response in the four species.The response, if any, most often arose from an increase in USRbeing accompanied by a less than proportionate decline in SWF.Responses were sustained throughout the period studied. At thelower nutrient level, all species showed a CO₂ response initially,but this declined at a rate which was inversely related to theCO₂-responsiveness of the species at the higher nutrient level. The underlying ontogenetic drift appeared to be markedly towardsadjustment in SWF and away from that of USR. However, this driftwas retarded, suspended or even reversed by low-nutrient conditionsand/or by high CO₂ responsiveness in the species itself.Copyright1995, 1999 Academic Press Climate change, CO₂ enrichment, plant strategies, mineral nutrition, growth analysis, relative growth rate, shoot weight fraction, unit shoot rate, functional equilibria     

Response of Photosynthesis to Radiation and Intercellular CO2 Concentration in Sun and Shade Shoots of Norway Spruce

Functional differentiation of assimilation activity of sun versus shade foliage was analysed in a Norway spruce monoculture stand (age 15 years). The investigated stand density (leaf area index 8.6) and crown structure led to variation in the photosynthetically active photon flux density (PPFD) within the crowns of the sampled trees. At the saturating PPFD, the maximum rate of CO₂ uptake (P _Nmax) of exposed shoots (E-shoots) was 1.7 times that of the shaded shoots (S-shoots). The apparent quantum yield (α) of E-shoots was 0.9 times that of the S-shoots. A lower ability to use excess energy at high PPFD in photosynthesis was observed in the S-layer. The CO₂- and PPFD-saturated rate of CO₂ uptake (P _Nsat) of the E-shoots was 1.12 times and the carboxylation efficiency (τ) 1.6 times that of the S-shoots. The CO₂-saturated rate of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) carboxylation (V_Cmax) and of actual electron transport (J_amax) in the S-needles amounted to 89 and 95 % of V_Cmax and J_amax in the E-needles. Thus, in addition to the irradiation conditions and thus limitation by low J_a, the important limitation of photosynthesis in shade needles is due to carboxylation. This limitation of photosynthesis is accompanied by lower stomatal conductance. This revised version was published online in June 2006 with corrections to the Cover Date.     

Bio-Energy Retains Its Mitigation Potential Under Elevated CO2

Background

If biofuels are to be a viable substitute for fossil fuels, it is essential that they retain their potential to mitigate climate change under future atmospheric conditions. Elevated atmospheric CO₂ concentration [CO₂] stimulates plant biomass production; however, the beneficial effects of increased production may be offset by higher energy costs in crop management.

Methodology/Main Findings

We maintained full size poplar short rotation coppice (SRC) systems under both current ambient and future elevated [CO₂] (550 ppm) and estimated their net energy and greenhouse gas balance. We show that a poplar SRC system is energy efficient and produces more energy than required for coppice management. Even more, elevated [CO₂] will increase the net energy production and greenhouse gas balance of a SRC system with 18%. Managing the trees in shorter rotation cycles (i.e., 2 year cycles instead of 3 year cycles) will further enhance the benefits from elevated [CO₂] on both the net energy and greenhouse gas balance.

Conclusions/Significance

Adapting coppice management to the future atmospheric [CO₂] is necessary to fully benefit from the climate mitigation potential of bio-energy systems. Further, a future increase in potential biomass production due to elevated [CO₂] outweighs the increased production costs resulting in a northward extension of the area where SRC is greenhouse gas neutral. Currently, the main part of the European terrestrial carbon sink is found in forest biomass and attributed to harvesting less than the annual growth in wood. Because SRC is intensively managed, with a higher turnover in wood production than conventional forest, northward expansion of SRC is likely to erode the European terrestrial carbon sink.     

Changes in Sapwood of Roots of Norway Spruce, Attacked by Fomes annosus

Acetone extracts of sapwood and reaction zone of spruce roots attacked by Fomes annosus, collected in February, June and October, were separated into resinous and phenolic fractions. The fractions were further separated by column, thin layer and gas liquid chromatography, followed by biological tests, using Fomes annosus and other rot fungi. The reaction zone contained quantitatively less light petroleum soluble compounds than the sapwood but more acids. The phenolic content was about ten times higher in the reaction zone than in the sapwood. Nine lignans and one simple phenol (4-methylcatechol) were identified and quantitatively estimated in the reaction zone. The resinous fraction of the extract from the reaction zone as well as some of the lignans and 4-methylcatechol inhibited fungal growth, in some cases followed by detoxification and continued growth. The predominant lignan, hydroxymatairesinol, had no effect on Fomes annosus or five other wood degrading fungi. About 15 unidentified phenols were observed, some of them probably of importance as inhibitors, either alone or in combination with other phenols.     

Anatomical and Histochemical Changes of Norway Spruce Buds Induced by Simulated Acid Rain

The study was focused on changes of anatomical and histochemical parameters of buds of 4-year-old Norway spruce (Picea abies L. Karst) trees subjected to simulated acid rain (SAR). Solutions of pH 2.9 and 3.9 were applied by spraying on shoot and/or by watering for two years. No macroscopic changes of buds or needles were observed in connection with SAR application and the only induced change was 2-week earlier onset of bud break in all treated variants compared to the control. Two-year treatment caused decrease in number of leaf primordia and increase in number of living bud scales in treated dormant buds while these parameters remained unchanged in the control buds. Treatments with solution of pH 2.9 caused decrease of flatness of bud apical meristem during the vegetative season. Increased activity of non-specific esterase in treated buds occurred during dormancy and bud break and the enhanced accumulation of phenolic compounds was detected at the beginning of shoot growth. Changes in histochemical parameters of bud tissues were induced mainly by spraying of shoots and can thus be qualified as primary damage.