Morphological and stomatal responses of Norway spruce foliage to irradiance within a canopy depending on shoot age

Morphological and stomatal responses of Norway spruce (Picea abies) foliage to light availability were studied in respect to shoot age. Needle minor diameter (D(1), anatomical width), major diameter (D(2), anatomical thickness), dry weight (M), and tissue density index (I(D)) increased, and needle flatness (Fl) and specific leaf area (SLA) decreased with foliage age, while shade foliage demonstrated higher morphological plasticity as compared to sun foliage. Needle minor diameter, dry weight, and the ratio of total to projected leaf area increased, and needle flatness and specific leaf area decreased with daily average photosynthetic photon flux density (Q(D)). The current-year foliage exhibited the highest variation with irradiance, while the morphological plasticity decreased with needle ageing. The morphological characteristics of needles were independent of irradiance if Q(D) was above 300 μmol m(-2) s(-1). D(1) was the only linear needle characteristic which significantly changed with light availability within a canopy, and thus determined needle flatness, SLA, as well as the ratio of total to projected leaf area (TLA/PLA). Needle flatness was a characteristic responding most sensitively to the photosynthetic photon flux density, R(2) was 0.68, 0.44, and 0.49 for the current-year, 1-year-old, and 2-year-old foliage, respectively. TLA/PLA ranged from 2.2 to 4.0 depending on D(1). Variation in SLA in response to light availability can be attributed to changes both in needle shape and tissue density. Stomatal responses to photosynthetic photon flux density (Q(P)) depended on foliage type (sun or shade) and age. Sun needles demonstrated higher daily maximum leaf conductances to water vapour compared to shade needles. The shade needles responded more sensitively to changes in Q(P) at dawn and sunset than the sun needles, while older needles of both foliage types exhibited faster stomatal responses. The light-saturation of leaf conductance (g(L)) was achieved by 20 μmol m(-2) s(-1) for shade foliage, and approximately by 50 μmol m(-2) s(-1) for sun foliage. As a rule, g(L) changed in response to irradiance faster in the evening, i.e. at decreasing irradiance. Stomata were not usually completely closed in the dark before sunrise and after sunset, the phenomenon being more pronounced in older shoots and sun needles. Nightly water losses from spruce foliage are attributable primarily to older shoots, and are related to age-dependent changes in stomatal responsiveness.     

Needle area measurement by the cut method and estimation of specific leaf area inCryptomeria japonica

Needle surface area inCryptomeria japonica was measured using a newly proposed cut method. Sample needles of various lengths were taken from foliage shoots belonging to various height layers of nine trees growing at three sites. Needles were cut into small pieces with a hand-made cutter made of razor blades and washers. By measuring the circumference and thickness of each piece, its lateral area was calculated and summed to give the total surface area of the needle. For estimating the surface area of a needle (s), two linear parameters of needle size termedy _n* and /were proposed:y _n* was the distance between the needle tip and the uppermost point of attachment of the needle to the shoot, whilel was the distance between the needle tip and the lowermost point of attachment. The power-form relationship betweens andl was superior to thes-y _n* relationship, since the former did not differ significantly among shoots of different diameter. Based on thes-l relationship, the total surface area of a shoot was estimated from thel-census of the shoot. Specific leaf area of a shoot (SLA), defined as half of the shoot surface area divided by the dry weight of the shoot, decreased from 90 to 3 [cm²g(dry wt)⁻¹] with the diameter of the woody tissue of the foliage shoot.     

Relationship between specific leaf area of aCryptomeria japonica foliage shoot segment and its diameter

Dependency of specific leaf area (SLA) on shoot diameter (x) was studied forCryptomeria japonica foliage shoot segments about 5 cm in length taken from 18 branches at different height levels on 3 trees in August 1987. The leaf area of a shoot segment (S) was defined as half the sum of the needle area (s) estimated by the allometric relationship betweens and needle length. The dry weight of woody tissue (W _w) and needles (W _n) of a segment and itsS were divided by the segment length (L) to give linear densities asW _w/L,W _n/L andS/L, respectively. The densities were related tox by power-form equations.S/L values tended to be constant around 1.2 [cm² cm⁻¹] within the discussed range ofx, whileW _w/L andW _n/L values clearly increased withx. The approximately reciprocal relationship between average needle area (s) and linear density of the number of needles supported the fact thatS/L values were roughly constant regardless ofx.SLA andSNA were defined asS/(W _w+W _n) andS/W _n, respectively. TheSLA-x relationship expected from the average value ofS/L and theW _w/L-x and theW _n/L-x relationships was well fitted to the observed decrease inSLA with increasingx. SNA also decreased asx increased. Variations inSLA andSNA among the shoot segments with similarx were not systematically related to their height levels. An empirical equation with a maximum value ofx (Xmax) was also proposed in order to formulate theSLA-x relationship.     

Estimation of leaf area at the level of branch,tree and stand inCryptomeria japonica

The frequency distribution of diameter (x) in foliage shoot segments, ø(x), was examined in 18 branches at different height levels of three trees in a 25-yr-old sugi (Cryptomeria japonica D. Don) plantation. The ø-x relationships were approximated by power-form equations, in which the exponent differed among the branches from ?0.6 to ?4.2. Leaf area (S _B) and leaf weight (W _B) of a branch were estimated on the basis of the ø-x relationship, and the dependency of specific leaf area (SLA ₀) and density (ρ ₀) of a foliage shoot segment on itsx. SLA _B value of a branch defined byS _B/W _B ranged from 27 to 80 cm² g. d.w.^?1 according to the exponent in the function of ø(x). Total leaf area (u) and leaf weight (wl) of a tree were estimated by summation ofS _B andW _B for seven sample trees. TheSLA _T value of a tree defined byu/wl ranged from 65 to 76 cm² g d.w.^?1 and increased with stem diameter at clear length (D _B). By use of the allometric equations betweenu andD _B,LAI of the plot was estimated to be 17.3 ha ha^?1 (half of the total surface area of needles). By a process similar to that used for calculatingLAI, the amount of woody tissues included in sugi foliage was evaluated to be about 10% of the stand foliage biomass.     

Measurement methods and variability assessment of the Norway spruce total leaf area: implications for remote sensing

Estimation of total leaf area (LA_T) is important to express biochemical properties in plant ecology and remote sensing studies. A measurement of LA_T is easy in broadleaf species, but it remains challenging in coniferous canopies. We proposed a new geometrical model to estimate Norway spruce LA_T and compared its accuracy with other five published methods. Further, we assessed variability of the total to projected leaf area conversion factor (CF) within a crown and examined its implications for remotely sensed estimates of leaf chlorophyll content (C _ab). We measured morphological and biochemical properties of three most recent needle age classes in three vertical canopy layers of a 30 and 100-year-old spruce stands. Newly introduced geometrical model and the parallelepiped model predicted spruce LA_T with an error <5 % of the average needle LA_T, whereas two models based on an elliptic approximation of a needle shape underestimated LA_T by up to 60 %. The total to projected leaf area conversion factor varied from 2.5 for shaded to 3.9 for sun exposed needles and remained invariant with needle age class and forest stand age. Erroneous estimation of an average crown CF by 0.2 introduced an error of 2–3 μg cm^?2 into the crown averaged C _ab content. In our study, this error represents 10–15 % of observed crown averaged C _ab range (33–53 μg cm^?2). Our results demonstrate the importance of accurate LA_T estimates for validation of remotely sensed estimates of C _ab content in Norway spruce canopies.     

Variation of specific leaf area and upscaling to leaf area index in mature Scots pine

Reliable and objective estimations of specific leaf area (SLA) and leaf area index (LAI) are essential for accurate estimates of the canopy carbon gain of trees. The variation in SLA with needle age and position in the crown was investigated for a 73-year-old Scots pine (Pinus sylvestris L.) stand in the Belgian Campine region. Allometric equations describing the projected needle area of the entire crown were developed, and used to estimate stand needle area. SLA (cm² g⁻¹) as significantly influenced by the position in the crown and by needle age (current-year versus 1-year-old needles). SLA increased significantly from the top to the bottom of the crown, and was significantly higher near the interior of the crown as compared to the crown edge. SLA of current-year needles was significantly higher than that of 1-year-old needles. Allometric relationships of projected needle area with different tree characteristics showed that stem diameter at breast height (DBH), tree height and crown depth were reliable predictors of projected needle area at the tree level. The allometric relationships between DBH and projected needle area at the tree level were used to predict stand-level needle area and estimate LAI. The LAI was 1.06 (m² m⁻²) for current-year needles and 0.47 for 1-year-old needles, yielding a total stand LAI of 1.53.     

Is long-lived foliage in Picea mariana an adaptation to nutrient-poor conditions?

Summary This study evaluated the contribution of different ages of foliage to the nutrient and carbon balance of black spruce (Picea mariana (Mill.) B.S.P.) from a nutrient-poor peatland in Alberta. Seasonal patterns of foliar nitrogen and phosphorus concentration and content were examined in six needle cohorts up to 10 years old. Trees were treated to simulate excess nutrient deficiency (removal of all one-year-old foliage), nutrient excess (fertilized with 250, 50, 100 kg ha^–1 NPK split application in June and July), or left as controls. Gas exchange (net assimilation-Na, stomatal conductance-g_s, mesophyll conductance-g_m, water-use efficiency-WUE, dark respiration-RS) was measured on six different needle cohorts in several control trees in 1989 and 1990. Nitrogen and phosphorus concentration decreased with needle age. Foliar nutrient concentration fell from April to June and then was stable until September except for the fertilized trees where it increased. There was no evidence of greater than normal retranslocation of nutrients from older needles for defoliated trees or greater than normal nutrient loading in older needles of fertilized trees. NA, g_s, g_m, WUE, and RS were similar for all needles up to six or eight years old, these older needles having NA of 65% of current needles and similar RS. The results do not support to conclusion that older needles of black spruce are retained as an adaptation to nutrient stress. It does not appear that older needles serve as a nutrient storage site in conditions of excess nutrient availability or a greater than normal nutrient source during times of excess nutrient deficiency. It appears that the maintenance of long-livedfoliage in black spruce does not provide for greater flexibility in tree nutrient allocation. Their contribution to the carbon balance of the tree seems to be sufficient to explain their retention.     

The effects of elevated atmospheric [CO<Subscript>2</Subscript>] 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].     

Surface areas,lengths and volumes of Picea abies (L.) Karst. needles: determination,biological variability and effect of environmental factors

Summary A method for the rapid determination of the lengths and surface areas of very large samples of needles of Picea abies (L.) Karst. using a computer-aided image analysis system was developed. Two independent methods for measuring non-destructively the volumes of individual needles and of all needles attached to a twig were devised. The surface areas and lengths of about 38000 needles sampled from the three youngest needle age-classes (1986, 1985, 1984) of 48 trees approximately 130 years old at four sites in the Fichtelgebirge mountains (N. E. Bavaria, FRG) were measured. The frequency distributions of lengths and areas for each site and age-class are given. Variability of needle size was fairly large. Even though the sites differed in climate, soil, and air pollution levels no consistent effect of these factors on needle size could be detected. Needle lengths and surface areas did not correlate with either the total chlorophyll content of the needles or the degree of crown thinning. The needle surface area (in mm²) of fully developed P. abies needles can be estimated by the empirical equation surface area = 4.440 x needle length -24.8 (r = 0.937), and the needle volume (in mm³) by needle volume = 0.208 x projected needle area ^1.353 (r = 0.969).     

Carbon uptake and respiration in above-ground parts of a Larix decidua × leptolepis tree

Summary Shade needles of hybrid larch (Larix decidua × leptolepis) had the same rates of photosynthesis as sun needles per dry weight and nitrogen, and a similar leaf conductance under conditions of light saturation at ambient CO₂ (A_max). However, on an area basis, A_max and specific leaf weight were lower in shade than in sun needles. Stomata of sun needles limited CO₂ uptake at light saturation by about 20%, but under natural conditions of light in the shade crown, shade needles operated in a range of saturating internal CO₂ without stomatal limitation of CO₂ uptake. In both needle types, stomata responded similarly to changes in light, but shade needles were more sensitive to changes in vapor pressure deficit than sun needles. Despite a high photosynthetic capacity, the ambient light conditions reduced the mean daily (in summer) and annual carbon gain of shade needles to less than 50% of that in sun needles. In sun needles, the transpiration per carbon gain was about 220 mol mol^–1 on an annual basis. The carbon budget of branches was determined from the photosynthetic rate, the needle biomass and respiration, the latter of which was (per growth and on a carbon basis) 1.6 mol mol^–1 year^–1 in branch and stem wood. In shade branches carbon gains exceeded carbon costs (growth + respiration) by only a factor of 1.6 compared with 3.5 in sun branches. The carbon balance of sun branches was 5 times higher per needle biomass of a branch or 9 times higher on a branch length basis than shade branches. The shade foliage (including the shaded near-stem sun foliage) only contributed approximately 23% to the total annual carbon gain of the tree.     

Short- versus Long-Term Effects of Elevated CO2 on Night-Time Respiration of Needles of Scots Pine (Pinus sylvestris L.)

Dark respiration rate in the night (R _D) was measured in five-year-old Scots pine (Pinus sylvestris L.) trees grown for two years under ambient (AC) and elevated (AC + 400 µmol mol^–1 = EC) CO₂ concentrations in open top chambers. Two needle age classes (i.e., current-year and one-year-old) were measured at AC and EC in both AC- and EC-grown pines. Additionally different chemical characteristics were determined on the needles, such as nitrogen (N), carbon (C), starch, and soluble sugar concentrations as well as specific leaf area. The direct, short-term and indirect, long-term effects of EC on R _D for the two needle age classes were examined. R _D was expressed on a per needle area, needle mass, N, C, and C/N bases. Direct effects were only pronounced in the AC treatment where inhibition of R _D was found at EC in both current- and one-year-old needles. Indirect effects were only significant in one-year-old needles where a decrease was found in the EC grown trees as compared with AC ones when R _D was expressed per unit needle mass, C, or C/N. R _D per unit needle area and needle N were not sensitive to long-term EC, in any needle age class. Long-term EC treatment also influenced the response of the two needle age classes. One-year-old needles from the EC treatment had significantly lower R _D than current-year needles, but no such response was observed in the AC treatment. Our experiment re-emphasised the importance of expressing R _D on different bases for a correct interpretation of the responses to EC. Moreover, we showed that different needle age classes can respond differently to a CO₂ enrichment.     

Understanding changes in black (Picea mariana) and white spruce (Picea glauca) foliage biomass and leaf area characteristics

Key message

Growth conditions related to inter-tree competition greatly influence black and white spruce foliage biomass and projected leaf area characteristics.

Abstract

Foliage characteristics such as biomass and area are important among other reasons because they can be related to tree growth. Despite their economic and ecologic importance, equations to characterize foliage biomass and projected area of black (Picea mariana (Miller) BSP) and white (Picea glauca (Moench) Voss) spruces are sparse. Total foliage biomass and projected leaf area, foliage biomass and leaf area density, and relative vertical distribution of black and white spruces foliage biomass and leaf area were modelled with linear and nonlinear mixed effect models. A total of 65 white spruces and 57 black spruces were destructively sampled at four different locations in Alberta, Québec, and Ontario, Canada. Our results show that for each species, total tree foliage biomass and projected leaf area is proportional to stem diameter, total height, and crown length. The addition of crown length in the equations improved the precision of the predictions of total foliage biomass for both species and diminishes greatly the site level random effect. An increase in DBH for black spruce and in the DBH to total height ratio for white spruce skewed the relative vertical foliage biomass distribution toward the base of the living crown. According to our results, growth conditions or tree development stage influence both foliage biomass and leaf area characteristics of black and white spruces. Our results emphasize the importance of inter-tree competition on foliage biomass characteristics.     

Leaf surface properties of Norway spruce needles exposed to sulphur dioxide and ozone in an open-air fumigation system at Liphook

Samples of current-year and 1-year-old foliage were taken from Norway spruce (Picea abies (L.) Karst.) trees in April 1991, 4 months after a 3–4 year controlled fumigation with O₃ and SO₂ in the open at Liphook, south-east England. Trees were grown in seven plots, and treated in a factorial design with three levels of SO₂ and two levels of O₃ (ambient and c. 1.3 × ambient), with an extra ambient air plot. All statistical analyses were made on plot means. Leaf wettability, as measured by the contact angle of water droplets, was significantly affected by needle age and by SO₂ treatment (P≤0–05. in older needles, decreasing with increasing SO₂ concentration. There was no effect of O₃ on wettability, and no effect of any treatment on amounts of surface wax extracted by immersion of needles in chloroform. Electrolyte leakage rates from detached current-year needles were not affected by prior exposure to O₃, but decreased significantly (P= 0.034) with increasing exposure to SO₂. There was no detectable effect of fumigation on the rate of water loss from detached needles. Similarly, there was no effect of fumigation on the dry weight/fresh weight ratio of needles. The total sulphur content of needles increased significantly (P≤0.0001) with exposure to SO₂ and with needle age. Amounts of water-extractable sulphate, however, varied greatly among plots, but with no pattern with respect to fumigation treatment. It is concluded that leaf wettability and electrolyte leakage rates may be good indicators of the persistent effects of SO₂ on Norway spruce growing in the open air, and that the observed changes in leaf surface properties in response to SO₂ fumigation have implications for the processes, both biotic and abiotic, that occur on leaf surfaces.     

Effect of open-air fumigation with sulphur dioxide and ozone on phyllosphere and endophytic fungi of conifer needles

The phyllosphere microbial populations inhabiting the needles of three conifer species, Scots pine (Pinus sylvestris L.), Sitka spruce (Picea sitchensis L.) and Norway spruce (Picea abies (L.) Karst.), exposed to SO₂ and O₃, in an open-air fumigation experiment were analysed over a 3 year period using serial dilution after washing, direct plating and a fluorescein diacetate (FDA) enzyme assay. Total fungal populations ranged from 10² to 10⁵ colonyforming units (CPU) g^?1 fresh weight of needles. The dominant fungi isolated from needles varied with tree species and isolation technique; Aureobasidium pullulans (de Bary) Arnaud was most common on Scots pine and Norway spruce and white yeasts on Sitka spruce using the dilution plating method. However, direct plating of needle segments onto culture media indicated that Sclerophoma pythiophila (Corda) Hohnel was dominant on Scots pine and A. pullulans on Sitka and Norway spruce. Green needles of Sitka spruce were found to be endophytically colonized by Rhizosphaera kalkhoffii Bubak, but seldom by Lophodermium piceae (Fuckel) Hohn during extensive sampling in 1990. Statistical analyses revealed significant differences (P<0.05) between plots in the 3 year mean of the total fungal populations or the fungal biomass (FDA assay) on all three tree species. Differences between plots were also observed for a number of dominant component species. Data were also analysed for treatment effects. A significant effect of SO₂ treatment was observed on the total fungal populations on Sitka spruce (P<0.05) which were reduced markedly by the low-SO₂ treatment, while the O₃ treatment caused a significant increase in total fungal numbers on Scots pine (P<0.05). The FDA activity on needles of both Scots pine and Sitka spruce was noticeably higher in the 0₃-only treatment plot, but the overall O₃ effect was not significant. Treatment effects were also detected on the occurrence of component species. The serial dilution method revealed an SO₂ effect (P<0.05) of a reduction in the occurrence of pink yeasts on Sitka spruce and an O₃ effect (P<0.05) of an increase in the occurrence of S. pythiophila on Sitka spruce (P<0.01) but a decrease of Epicoccum nigrum Link and Cladosporium spp. on Scots pine. The direct-plating method revealed an SO₂ effect of an increase in S. pythiophila on Norway spruce (P<0.05). Ozone treatment caused a significant increase in the isolation of a black strain of A. pullulans on Norway spruce (P<0.05). Endophytic colonization of Sitka spruce needles by R. kalkhoffii was found to be increased on two occasions by O₃ exposure.     

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, R ² = 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. Received: 24 January 1997 / Accepted: 1 July 1997     

Seasonal dynamics of chlorophyll and microelement content in developing conifer needles of <Emphasis Type="Italic">Abies sibirica</Emphasis> and <Emphasis Type="Italic">Picea abies</Emphasis>

Composition of microelements and photosynthetic pigment content (chlorophylls (Chl) a and b) were monitored in growing needles of spruce (Picea abies (L.) Karst.) and Siberian fir (Abies sibirica Ledeb.) during spring-autumn vegetation period. The dynamics of fresh weight and needle length for the first-year needles of spruce and fir revealed a number of shared and species-specific features in growth patterns of photosynthetic organs. In the beginning of growth period (in May), the needles elongated rapidly, while June–July were marked by the increase in needle weight. In P. abies the needle weight accumulated rapidly (specific growth rates μ_max up to 0.20 day⁻¹) over a short period (14 days), while in A. sibirica the needle weight increased slower (μ_max ≤ 0.11 day⁻¹) but over a longer period (≥30 days). The dynamics of Chl a and Chl b content and their ratio were identical in needles of both species over the growth period, although changes in Chl a were pronounced stronger than those in Chl b. In spring (May), a relatively high total Chl content per needle dry weight was noted. In summer (June–August), the total Chl content declined appreciably. In autumn (September–November), the total chlorophyll content in first-year needles increased slightly. Microelements were classified into two groups according to seasonal dynamics of their relative content in first-year needles. The first group includes Ba, Mn, Zn, B, Cu, Co, Cr, Pb, and Mo, whose relative content had a distinctive maximum in July, coincident with the peak in Chl content. The second group comprises Ni, V, Ag, Be, Cd, and As, whose relative content was minimal at this period. Seasonal changes in microelement composition were similar for the two conifer species examined, which is likely due to different physiological values of various microelements for photosynthetic organs.     

Foliar elemental composition of spruce-fir in the southern blue ridge province

Data are presented for what we believe to be the first assessment of the elemental foliar status of red spruce (Picea rubens Sarg.) and Fraser fir [Abies fraseri (Pursh.) Poir.] trees in the high elevation forests of the southern Appalachian mountans. Needle samples were collected from September–November 1984. Needles were separated according to flush year for the 1984, 1983 and 1982 growing seasons. Each sample was analyzed without washing for 28 macro- and micronutrients and trace elements. Significant differences in foliar concentrations were observed between flush year for N, P, Ca, Mg, K, Cl, Cu, Ce, Th, Cs, Pb, Fe, La and Rb for Fraser fir (n=41), and P, Ca, K, Cl, Cu, Pb and Rb for red spruce (n=30). Nitrogen concentrations ranged from 11.2–20.2 mg g^?1 for Fraser fir, and 8.7–15.9 mg g^?1 for red pruce. The mean concentration of Ca observed in red spruce needles (1.4 mg g^?1 1984 growing season) fell at the low extreme of reported values for non-necrotic red spruce foliage in the northeastern United States (1.2–11.6 mg g^?1). The mean concentration of Ca in Fraser fir foliage (3.4 mg g^?1, 1984 growing season) was also lower than reported values for eastern fir, but not to the extent demonstrated for red spruce. Fraser fir needles had higher concentrations of Al than red spruce (310vs 91 mg kg^?1, respectively, 1984 growing season), but both values are higher than those reported for spruce or fir from the northeastern United States. Calcium:aluminum ratios in current foliage are the lowest yet reported for the eastern spruce/fir forest type, suggesting that Al toxicity and/or Ca deficiency may be important stresses in these stands. Comparison of Pb concentrations with those of other rare-earth elements known to be associated with dust on needle surfaces (Ce, La, Sc, Sm, and Th) suggested that a substantial portion of the Pb found was due to particulates on the needle surfaces. The significance of these results to the observed forest decline syndrome in high elevation forests of the eastern United States is also discussed.     

The effects of enhanced ozone and enhanced carbon dioxide concentrations on biomass, pigments and antioxidative enzymes in spruce needles (Picea abies L.)

During one growing period, 5-year-old spruce trees (Picea abies L., Karst.) were exposed in environmental chambers to elevated concentrations of carbon dioxide (750 cm³ m^?3) and ozone (008 cm³ m^?3) as single variables or in combination. Control concentrations of the gases were 350cm³ m^?3CO₂ and 0.02 cm³ m ^?3 ozone. To investigate whether an elevated CO₂ concentration can prevent adverse ozone effects by reducing oxidative stress, the activities of the protective enzymes superoxide dismutase, catalase and peroxidase were determined. Furthermore, shoot biomass, pigment and protein contents of two needle age classes were investigated. Ozone caused pigment reduction and visible injury in the previous year's needles and growth reduction in the current year's shoots. In the presence of elevated concentrations of ozone and CO₂, growth reduction in the current year's shoots was prevented, but emergence of visible damage in the previous year's needles was only delayed and pigment reduction was still found. Elevated concentrations of ozone or CO₂ as single variables caused a significant reduction in the activities of superoxide dismutase and catalase in the current year's needles. Minimum activities of superoxide dismutase and catalase and decreased peroxidase activities were found in both needle age classes from spruce trees grown at enhanced concentrations of both CO₂ and ozone. These results suggest a reduced tolerance to oxidative stress in spruce trees under conditions of elevated concentrations of both CO₂ and ozone.     

SO2-dependent cation competition and compartmentalization in Norway spruce needles

Ion contents in needles from Norway spruce trees [Picea abies (L.) Karst.] growing in Würzburg and in the SO₂-polluted Erzgebirge mountains were analysed to quantify cations which accumulate together with sulphate. In Würzburg there was a positive correlation of potassium (0.680 ± 0.300 Eq Eq^?1 SO₄^?2), magnesium (0.415 ± 0.111 Eq Eq^?1 SO₄^?2) and zinc (0.059 ± 0.006 Eq Eq^?1 SO₄^2?). In the Erzgebirge, potassium was also the stoichiometrically most important cation (0–887 ± 0–180 Eq K⁺ Eq^?1 SO₄^2?). All other correlations examined were weak or statistically non-significant. At both sites the calcium content of spruce needles did not depend on the sulphate content. The lack of a role for Ca²⁺ in neutralizing sulphate is a consequence of the presence of free oxalic acid in needles. Soluble oxalic acid precipitates Ca²⁺, which thereby becomes unavailable as a counterion for SO₄^2?. The activity coefficients of Ca²⁺ and oxalate^2?, and the solubility product of Ca-oxalate, were determined from in vivo data. It is concluded that the chronic accumulation of atmospheric sulphate in spruce needle vacuoles depletes available potassium and thereby strongly interferes with spruce growth and canopy turnover. This leads to impaired spruce vitality, even at sites where acute SO₂ disease symptoms are absent.     

Effects of elevated CO2, elevated O3 and potassium deficiency on Norway spruce [Picea abies (L) Karst.]: seasonal changes in photosynthesis and non-structural carbohydrate content

Two clones of 5-year-old Norway spruce [Picea abies (L.) Karst.] were exposed to two atmospheric concentrations of CO2 (350 and 750 μmol mol^?1) and O₃ (20 and 75nmolmol^?1) in a phytotron at the GSF-Forschung-szentrum (Munich) over the course of a single season (April to October). The phytotron was programmed to recreate an artificial climate similar to that at a high elevation site in the Inner Bavarian Forest, and trees were grown in large containers of forest soil fertilized to achieve contrasting levels of potassium nutrition, designated well-fertilized or K-deficient. Measurements of the rate of net CO₂ assimilation were made on individual needle year age classes over the course of the season, chlorophyll fluorescence kinetics were recorded after approximately 23 weeks, and seasonal changes in non-structural carbohydrate composition of the current year's foliage were monitored. Ozone was found to have contrasting effects on the rate of net CO₂ assimilation in different needle age classes. After c. 5 months of fumigation, elevated O₃ increased (by 33%) the rate of photosynthesis in the current year's needles. However, O3 depressed (by 30%) the photo-synthetic rate of the previous year's needles throughout the period of exposure. Chlorophyll fluorescence measurements indicated that changes in photosystem II electron transport played no significant role in the effects of O₃ on photosynthesis. The reasons for the contrasting effects of O₃ on needles of different ages are discussed in the light of other recent findings. Although O₃ enhanced the rate at which CO₂ was fixed in the current year's foliage, this was not reflected in increases in the non-structural carbohydrate content of the needles. The transfer of ambient CO₂-grown trees to a CO₂-enriched atmosphere resulted in marked stimulation in the photosynthetic rate of current and previous year's foliage. However, following expansion of the current year's growth, the photosynthetic rate of the previous year's foliage declined. The extent of photosynthetic adjustment in response to prolonged exposure to elevated CO₂ depended upon the clone, providing evidence of intraspecific variation in the long-term response of photosynthesis to elevated CO₂. The increase in photosynthesis induced by CO₂ enrichment was associated with increased foliar concentrations of glucose, fructose and starch (but no change in sucrose) in the new growth. CO₂ enrichment significantly enhanced the photosynthetic rate of K-deficient needles, but there was a strong CO₂soil interaction in the current year's needles, indicating that the long-term response of trees to a high CO₂ environment may depend on soil fertility. Although the rate of photosynthesis and non-structural carbohydrate content of the new needles were increased in O₃-treated plants grown at higher levels of CO₂, there was no evidence that elevated CO₂ provided additional protection against O₃ damage. Simultaneous exposure to elevated O₃ modified the effects of elevated CO₂ on needle photosynthesis and non-structural carbohydrate content, emphasizing the need to take into account not only soil nutrient status but also the impact of concurrent increases in photochemical oxidant pollution in any serious consideration of the effects of climate change on plant production.