Acid mist and soil Ca and Al alter the mineral nutrition and physiology of red spruce

We examined the effects and potential interactions of acid mist and soil solution Ca and Al treatments on foliar cation concentrations, membrane-associated Ca (mCa), ion leaching, growth, carbon exchange, and cold tolerance of red spruce (Picea rubens Sarg.) saplings. Soil solution Ca additions increased foliar Ca and Zn concentrations, and increased rates of respiration early in the growing season (July). Soil Al treatment had a broad impact, reducing foliar concentrations of Ca, Mg, Mn, P and Zn, and resulting in smaller stem diameters, sapling heights and shoot lengths compared with soil treatments with no added Al. Aluminum treatment also reduced respiration when shoots were elongating in July and decreased net photosynthesis at the end of the growing season (September). Three lines of evidence suggest that Al-induced alterations in growth and physiology were independent of foliar Ca status: (1) Ca concentrations in foliage of Al-treated saplings were within the range of sufficiency established for red spruce; (2) mCa concentrations were unaffected by Al treatment; and (3) no Al x Ca interactions were detected. Acid mist treatment increased foliar Fe and K concentrations and increased leaching of Ca, Mg, Mn, Zn, Fe, and Al from foliage. Leaching losses of Ca were more than twice those of the element with the next highest amount of leaching (Zn), and probably led to the reductions in mCa concentration and membrane stability of acid-treated saplings. Acidic mist resulted in enhanced shoot growth, and consistent reductions in foliar cold tolerance in the fall and winter. Of the few significant interactions among treatments, most involved the influence of mist pH and Al treatment on foliar nutrition. In general, reductions in cation concentration associated with Al addition were greater for pH 5.0-treated saplings than for pH 3.0-treated saplings. We propose that H(+)-induced leaching of mCa from mesophyll cells is the mechanism underlying acid-induced reductions in foliar cold tolerance of red spruce.     

Physiological implications of seasonal variation in membrane-associated calcium in red spruce mesophyll cells

We examined the pattern of seasonal variation in total foliar calcium (Ca) pools and plasma membrane-associated Ca (mCa) in mesophyll cells of current-year and 1-year-old needles of red spruce (Picea rubens Sarg.) and the relationship between mCa and total foliar Ca on an individual plant and seasonal basis. Foliar samples were collected from seedlings and analyzed on 16 dated at 2- to 3-week intervals between June 1994 and March 1995. Concentrations of mCa in current-year needles were more seasonally dynamic and responsive to temporal environmental changes than either mCa concentrations of 1-year-old needles, which were largely stable, or total foliar Ca concentrations in both tissues. In current-year needles, mCa was barely evident in early summer, increased steadily through summer, and then increased dramatically in early fall and surpassed the concentration in 1-year-old needles. Coincident with the first severe frost, mCa concentrations in current-year needles declined significantly and subsequently maintained concentrations comparable to those of 1-year-old needles. Following an extended January thaw, which included 5 days of minimum temperatures > 5 degrees C, mCa concentrations of current-year needles temporarily, but significantly, declined. However, there was no change in mCa concentrations of 1-year-old needles or total Ca concentrations of either tissue. Total Ca concentrations were stable through midsummer in both tissues, doubled in late summer, and then were stable in both tissues throughout fall and winter. Total Ca concentrations were consistently higher in 1-year-old than in current-year needles. Correlations between concentrations of mCa and total foliar Ca were consistently low and mostly nonsignificant. Thus, the dominant, but insoluble, extracellular Ca pool reflected in commonly measured total foliar Ca concentrations is not a meaningful surrogate for the physiologically important and labile pool associated with the plasma membrane-cell wall compartment of red spruce mesophyll cells. It is likely that shifts in the critical mCa compartment would not be detected by analysis of total foliar Ca pools. Seasonal changes in mCa concentration seemed to parallel seasonal changes in membrane structure, and possibly the important role of extracellular Ca in transducing messages associated with environmental signals.     

Assimilation and stomatal conductance responses of red spruce to midwinter frosts and the constituent ions of acid mist

Red spruce (Picea rubens Sarg.) seedlings growing outside in open-top chambers were sprayed twice weekly with artificial mists at either pH 2.5 or 5.6, for five months during the 1988 growing season. The mists contained one of the following: water, pH 5.6 (control); (NH(4))(2)SO(4), pH 5.6; NH(4)NO(3), pH 5.6; HNO(3), pH 2.5; H(2)SO(4), pH 2.5; or (NH(4))(2)SO(4) + NH(4)NO(3), pH 2.5. During January 1989, the light responses of assimilation and stomatal conductance were assessed in the laboratory following a 4-day equilibration at 12 degrees C. The aerial portions of the intact trees were then subjected to a mild (-10 degrees C) frost for three hours during the night and the rate of recovery of light-saturated assimilation (A(max)) was determined the following day using the same branches as were used for the assimilation studies before the frost treatment. The same trees were then subjected to a second frost of -18 degrees C for three hours during the following night and the recovery of A(max) of the same branches was measured the next day. All of the acid mist treatments increased A(max) and apparent quantum yield relative to the control treatment when measured before the frost treatments. Frosts of -10 and -18 degrees C resulted in a significant decline in A(max) of seedlings in all treatments except the control. Stomatal conductance increased with increasing irradiance in seedlings in the acid mist treatments that did not contain SO(4) (2-) ion. Stomatal conductance of seedlings in acid mist treatments containing SO(4) (2-) ion was insensitive to changes in irradiance over the range 50-1500 micro mol m(-2) s(-1). It is concluded that acid precipitation increased the sensitivity of the assimilation response to midwinter frosts that follow a brief warm period. The SO(4) (2-) ion appears to be significant in causing increased sensitivity to frost and in causing stomatal insensitivity to light flux density.     

Water relations of red spruce seedlings treated with acid mist

Pressure-volume curves, day and night transpiration rates, needle drying curves, and shoot water potentials were determined for 2-year-old red spruce trees that had been exposed for three months to a range of acid mists (pH 2.5 to pH 5.0) containing equimolar (NH(4))(2)SO(4) and HNO(3). No effect of acid mist was observed on cuticular resistance or on the rates of day and night transpiration, although trees exposed to acid mist exhibited symptoms of mild water stress. Significant decreases in maximum turgor, the relative water content (RWC) associated with zero turgor, and bulk volumetric elastic modulus occurred as the pH of the mist decreased from 5.0 to 2.5. At all RWC values, there was an increase in solute potential as mist pH decreased. Shoot water potential declined with a decrease in pH of the mist.     

Impacts of nursery cultural treatments on stress tolerance in 1 + 0 container white spruce (<Emphasis Type="Italic">Picea glauca</Emphasis> [Moench] Voss) seedlings for summer-planting

Impacts of nursery cultural treatments (T) on stress tolerance of greenhouse-grown 1 + 0 container white spruce (Picea glauca [Moench] Voss) seedlings (mean height 24 cm, root collar diameter 3.1 mm) for summer planting were studied. Seedlings were subjected to 12-h short-day treatments of 0 (T0), 3 (T3), 7 (T7), 10 (T10), or 15 (T15) days, followed by 0, 7, 17, 40, or 46 days of reduced N supply, respectively. Relevant physiological and morphological factors were examined concurrently. Foliar N concentrations exceeded optimal levels and differed little among treatments, suggesting a minor confounding role for N reduction. Both frost and drought tolerance increased incrementally from T0 through T15. Electrolyte leakage index decreased steadily from T0 (25% for roots, 17% for needles) to T15 (1% for roots, 2% for needles) after 2-h exposure of fine roots to − 2°C and of needles to − 8°C. Withholding soil watering for 19 days caused 80% mortality among seedlings in T0, 50% in T3, and < 10% in T7–T15. The transpiration decline curve suggested that enhanced drought tolerance was largely attributable to quicker stomatal closure during water stress and lower cuticular transpiration rate. The treatments increased root growth capacity on a per-seedling, but not per-root-mass, basis. Needle primordia were developed in all T7-T15 seedlings but not in T0 and T3 treatments, suggesting that nurseries may need no more than 7 days of blackout application for conditioning spruce seedlings for summer planting. Shoot dry weight fraction increased gradually from T0 through T15 and was linearly correlated with needle specific weight and frost tolerance, and may thus be useful in monitoring progress of conditioning treatments.     

Growth, nutrition and response to water stress of Pinus pinaster inoculated with ten dikaryotic strains of Pisolithus sp

Reconstituted dikaryons of Pisolithus sp. (Pers.) Coker & Couch from South Africa influenced growth parameters (shoot length, shoot/root ratio and leaf area), nutrition and physiological indicators (transpiration rate, stomatal conductance and xylem water potential) of maritime pine (Pinus pinaster Ait.) seedlings during drought and recovery from drought. Seedlings colonized with certain dikaryons were more sensitive to water stress and showed less mycorrhiza formation under water stress than seedlings colonized with other dikaryons. Control (uninoculated) seedlings were significantly smaller than those inoculated with dikaryons. Transpiration rate, stomatal conductance and xylem water potential varied among mycorrhizal treatments during the water stress and recovery periods. After rewatering, the controls and seedlings inoculated with dikaryon 34 x 20 had a weaker recovery in transpiration rate, stomatal conductance and xylem water potential than the other treatments and appeared to have experienced damage due to the water stress. Concentrations of various elements differed in the shoots of Pinus pinaster colonized by the various dikaryons. It is suggested that breeding of ectomycorrhizal fungi could constitute a new tool for improving reforestation success in arid and semi-arid zones.     

模拟酸雨对盆栽广玉兰幼苗叶矿质元素含量的影响

以广玉兰为试材,采用盆栽方法,配制3种不同pH值(3.0、4.0、5.0)的模拟酸雨溶液对幼苗进行浇灌处理,分析了不同pH值的酸雨对幼苗叶中矿质元素含量的影响.结果表明:盆栽广玉兰幼苗经模拟酸雨浇灌处理后,幼苗叶中矿质元素含量受到一定程度的影响;3种酸雨处理的幼叶中P、Mg、S含量均较对照有所增加,Ca、Zn、Mn、Ni、Cd含量均下降,N、Fe、Cu、Pb变化趋势相同,即都是pH3.0处理含量增加,pH4.0和pH5.0处理下降;C、K、Al含量不随酸雨pH值改变而变化,其中C含量pH3.0、pH4.0处理增加,pH5.0处理下降;K含量pH3.0和pH5.0处理下降,pH4.0处理增加;Al含量pH3.0、pH5.0处理增加,pH4.0处理略微减少.该项研究可为南方城市绿化树种的选择提供理论依据.     

Water relations characteristics of competing singleleaf pinyon seedlings and sagebrush nurse plants

Encroachment of singleleaf pinyon (Pinus monophylla) into adjacent low sagebrush (Artemisia arbuscula) and basin big sagebrush (Artemisia tridentata ssp. tridentata) communities may be enhanced by the efficient use of limited water resources by tree seedlings. Seedlings and sagebrush nurse plants were monitored over two growing seasons to determine water-use patterns. Predawn xylem water potential of low sagebrush declined rapidly, reaching −3.5 to −5.5 MPa by late summer. Big sagebrush values dropped to −2.0 to −3.0 MPa during summer drought. The drop in sagebrush xylem water potential was related to the decline in soil water potential (r=0.68 and 0.82). The change in pinyon predawn xylem water potential was moderate, declining to values of −1.5 to −2.5 MPa. An apparent diurnal threshold xylem water potential (−2.3 to −3.0 MPa) that results in stomatal closure enables pinyon seedlings to maintain a seasonally stable xylem water potential. Water use by pinyon seedlings declined by 50% from May to August in association with a reduction in stomatal conductance. Despite reduced stomatal conductance, sagebrush water use continued to increase during summer and reached levels up to five times greater (per unit leaf area) than associated pinyon. Pinyon seedlings appear to have greater drought avoidance than sagebrush nurse plants.     

White and black spruce seedling development using the concept of relative addition rate

Ingestad's concept of relative addition rate was used to grow a range of seedling types, of both black (Picea mariana) (Mill.) B.S.P.), and white spruce (Picea glauca (Moench) Voss). Seedlings were grown for about 18 weeks in styrofoam containers under greenhouse conditions, and fertilized at exponentially increasing rates of either one, two, four or six per cent per day, following a one month pretreatment period. Pretreatment consisted of applying a nutrient solution proportionally low in nitrogen, but that had a relatively high conductivity compared to the initial solutions used in the exponentially increasing fertilizer treatments. Black spruce seedlings grew fastest, had significantly more root development or had a higher efficiency of nitrogen uptake when nutrients were applied at exponentially increasing amounts. In contrast, white spruce grew more rapidly when fertilized with a constant level of fertilizer (control treatment). Biomass allocation and nitrogen concentrations in seedlings of both species varied significantly with treatment, indicating that various levels of nitrogen stress had been achieved. It is suggested that different seedling stock types, which are acclimated to various levels of nutrient stress, can be produced by controlling the rate of nutrient addition.     

Competition for soil water between perennial bunch-grass (Elymus glaucus B.B.) and blue oak seedlings (Quercus douglasii H. & A.)

The competition effects of the perennial bunch-grass (Elymus glaucus B.B.) on the growth and survival of the oak seedlings (Quercus douglasii H. & A.) were investigated. There were four levels of Elymus competition, replicated three times. The three densities ofElymus employed were zero (control), 50 (Low — ‘L’ -), 116 (Medium — ‘M’ -) and 199 (High — ‘H’ -) plants m^?2. Rates of soil water depletion, stomatal conductance, transpiration, shoot elongation and leaf expansion rates were measured between 23 March and 26 May 1988. Rates of soil water depletion, stomatal conductance and transpiration differed amongst the treatments and were higher in the control for the duration of the experiment. Shoot elongation rate (SER) and leaf expansion rate (LER) of blue oak seedling were directly related to soil water potentials. Zero values of LER rates for all treatments were observed at soil water potentials lower than?1.91 MPa, and concurrent reductions of stomatal conductance indicated stomatal closure due to the soil water deficit. In the control treatment, transpiration alone was not high enough to deplete soil moisture and to reduce LER of the oak seedlings. Leaf dessication occurred first in the H and M treatments (53% of seedlings dessicated) and two weeks later in the L treatment (37% dessicated) when the soil water potential was approximately ?4.0 MPa. The number of reproductive tillers and seed dry weight indicated thatElymus plants were under water stress from April 25 and concluded on May 25 with an early summer dormancy in all treatments. Data indicated that light intensity of 50% of ambient did not limit the development of oak seedlings. The results suggested that density of the perennial bunch-grassElymus glaucus lower than 50 plants m^?2 could allow survival and successful establishment of blue oak in understories.     

Detection and quantification of changes in membrane-associated calcium in red spruce saplings exposed to acid fog

Five-year-old red spruce saplings (Picea rubens Sarg.) were exposed to either (1) acid fog consisting of a mixture of H(2)SO(4) and HNO(3) adjusted to pH 2.5, (2) distilled-water fog at pH 5.6, or (3) no fog (dry control) for 3.5 hours per day, five times a week during the 1996 and 1997 growing seasons. The effect of fog on cell membrane-associated calcium (mCa) of leaf mesophyll cells was investigated with the fluorescence probe chlortetracycline (CTC). In both years, mean mCa concentrations were significantly less in needles exposed to acid fog than in needles exposed to distilled-water fog or in untreated needles. In 1997, acid-fog treatment resulted in 25 and 12% reductions in mCa in current-year needles, and 18 and 15% reductions in 1-year-old needles, compared with untreated needles and needles exposed to distilled-water fog, respectively, indicating that acid deposition induced calcium leaching from the membranes of photosynthetic mesophyll cells. Exposure to distilled-water fog also led to reductions in mCa in young needles, suggesting that water films on needle surfaces can induce losses by diffusion between the needle interior and surface. Consistent with the chamber studies, field data obtained from red spruce trees at two sites in Maine showed that low mCa concentrations in needles were associated with exposure to acid fog.     

Infection experiments with Gremmeniella abietina on seedlings of Norway spruce and Scots pine

Conidia of Gremmeniella abietina infected and caused disease symptoms in annual shoots of both Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) seedlings. In Norway spruce shoots the infection remained largely latent, with only a few seedlings showing symptoms. Mycelial growth inside the shoots was faster in Scots pine than in Norway spruce and was favoured by low temperature in both hosts. The shoots of Norway spruce seedlings had higher endophyte populations than those of Scots pine, and the populations were decreased by low temperatures. Reductions in the normal epiphytic or endophytic flora by acid mist treatments seemed to favour the development of G. abietina.     

Differential adsorption of Al, Ca, and Mg by roots of red spruce (Picea rubens Sarg.)

The surface adsorption characteristics of red spruce (Picea rubens) roots were examined as a function of changes in external acidity and cation concentrations. Root cation exchange capacity varied significantly with changes in pH, increasing from 110 micromol(c) g(-1) at pH 3.5 to 155 micromol(c) g(-1) at pH 4.5, and reaching 250 micromol(c) g(-1) at pH 7.0. In general, Al adsorption by spruce roots was much greater than either Ca or Mg adsorption under the same initial conditions. However, root affinity for the divalent cations was proportionately much more sensitive to pH changes than was root affinity for Al. The fractions of adsorbed Ca and Mg increased by 50 to 100% as pH increased from 3.5 to 4.5, whereas the fraction of adsorbed Al remained relatively constant at both initial pH conditions. Competition experiments at pH 3.5 and 4.5 indicated that Al adsorption was strongly favored over Ca adsorption, except at low Al concentrations (~10 micromol l(-1)), high solution Ca(2+)/Al(3+) ion activity ratios (> 1.5 to 5.0), and at the higher pH. These results suggest that cell wall exchange sites in red spruce roots will tend to become progressively saturated with Al under the prevailing conditions of many acidic forest soils. To the extent that root adsorbed Al interferes with the active uptake of Ca and Mg, this process of competitive cation adsorption can contribute to impaired mineral nutrition in the spruce forest community.     

Influence of nutrient supply on spring frost hardiness and time of bud break in Norway spruce (Picea abies (L.) Karst.) seedlings

When spring frosts occur on recently planted forest sites, severe damage may occur to the seedlings. The aim of the present study was to test how different low levels of nutrient concentrations in Norway spruce (Picea abies (L.) Karst.) seedlings affected spring frost hardiness and time of bud break. Seedlings were grown in a greenhouse for one season and supplied with fertiliser containing 22, 43 and 72 mg N l^–1, respectively. The treatments resulted in needle nitrogen concentrations ranging from 0.9 to 1.8% in autumn. After winter storage at 0 °C, bud break was recorded on seedlings growing in the greenhouse, outdoors and in growth chambers at 12 °C and at 17 °C. Freezing tests were performed on seedlings directly removed from winter storage and following one week growth in the greenhouse. Seedlings receiving fertiliser with 43 mg N l^–1 had less freezing injury than the two other fertilisation treatments in the present study. The earliest bud break occurred in seedlings receiving 72 mg N l^–1.     

多重复干旱循环对北美短叶松和黑云杉苗木气体交换及水分利用效率的影响

本文研究了多重复干旱循环对１年生北美短叶松（ＰｉｎｕｓｂａｎｋｓｉａｎａＬａｍｂ．）和黑云杉（Ｐｉｃｅａｍａｒｉａｎａ［Ｍｉｌ］Ｂ．Ｓ．Ｄ．）苗木的气体交换速率及水分利用效率的影响。结果表面，多重干旱循环对它们的气体交换（Ｃｓ，Ｐｎ，Ｔｒ）有显著影响（Ｐ＜０．５），而对其水分利用效率（ＷＵＥ）影响不大（Ｐ＞０．１）。尽管北美短叶松的气孔对轻度干旱胁迫不如黑云杉敏感，但是它对中度及严重干旱胁迫的敏感程度却高于黑云杉。在轻度及中度干旱胁迫下，北美短叶松的光合作用主要受非气孔因素的影响，而黑云杉则主要受气孔因素的影响。解除干旱胁迫后，黑云杉的气孔敏感性、光合能力及水分利用效率的恢复都要比北美短叶松更快．我们认为，延迟脱水是北美短叶松的主要耐旱机理，而忍耐脱水则是黑云杉重要的耐旱途径。轻度的干旱胁迫锻炼可以帮助北美短叶松在更严重的干旱胁迫下保持固有而较强的耐旱能力。然而，通过多重复干旱循环锻炼后黑云杉在改善耐旱能力的强度方面则大于北美短叶松     

Stomatal and mesophyll limitations of photosynthesis in black spruce seedlings during multiple cycles of drought

Container-grown black spruce (Picea mariana (Mill.) B.S.P.) seedlings were planted in trays containing a sand and peat mixture, and placed in a climate-controlled greenhouse. One group of seedlings was kept well-watered, and another group was subjected to three cycles of drought. Gas exchange analysis showed that mesophyll photosynthetic function was largely unimpaired by drought. In contrast, stomatal conductance was sensitive to drought, although it became less sensitive with each drought cycle. Both stomatal and mesophyll conductances increased with time in control and drought-stressed seedlings, but mesophyll conductance increased with time more rapidly than did stomatal conductance. Limitation of photosynthetic rate was dominated by the mesophyll. In control seedlings, relative stomatal limitation increased from 6 to 16% by the end of the experiment. In drought-stressed seedlings, relative stomatal limitation of photosynthesis reached 40% during the first drought, but decreased to near control values immediately after rewatering. Because the third, most severe drought had only a minor effect on stomatal conductance, relative stomatal limitation of photosynthesis was similar to that in control seedlings by the end of the experiment. Inhibition of ontogenetic change during drought stress may be responsible for the apparent acclimation of mesophyll photosynthetic processes. We conclude that it would be more effective to select for high photosynthetic capacity than for reduced stomatal sensitivity when breeding for increased drought resistance in black spruce seedlings.     

A controlled test of the dual-isotope approach for the interpretation of stable carbon and oxygen isotope ratio variation in tree rings

Seedlings of a conifer (Pinus radiata D. Don) and a broad leaf angiosperm (Eucalyptus globulus Labill.) were grown for 100 days in two growth cabinets at 45 or 65% relative humidity. The seedlings were exposed to treatments designed to modify carbon assimilation rates and capacities, stomatal conductance and transpiration to test conceptual models that attempt to clarify the interpretation of carbon isotope discrimination (Δ(13)C) by using oxygen isotope enrichment (Δ(18)O). Differences in relative humidity and within-cabinet treatments (including lower irradiance, lower nitrogen inputs, higher leaf temperature and lower moisture status than control seedlings) produced significant differences in assimilation rates, photosynthetic capacities, stomatal conductance, leaf transpiration rates and leaf evaporative enrichment. The dual-isotope approach accurately interpreted the cause of variation in wood cellulose Δ(13)C for some of the treatments, but not for others. We also tested whether we could use Δ(13)C variation to constrain the interpretation of δ(18)O variation. Carbon isotope discrimination appears to be influenced by transpiration (providing information on leaf evaporative enrichment), but the results did not provide a clear way to interpret such variation. The dual-isotope approach appears to be valid conceptually, but more work is needed to make it operational under different scenarios.     

Stomatal conductance,growth and root signaling in Betula pendula seedlings subjected to partial soil drying

Seedlings of Betula pendula Roth were grown with their root systems separated between two soil compartments. Four treatments were imposed: (i) adequate irrigation in both compartments (WW, controls); (ii) adequate irrigation in one compartment and drought in the other compartment (WD); (iii) drought in both compartments (DD); and (iv) half of the root system severed and the remainder kept well-watered (root excision, RE). Predawn leaf water potential, stomatal conductance, soil-to-leaf specific hydraulic conductance, and root and leaf growth decreased in DD-treated seedlings, which also displayed severe leaf shedding (30% loss in leaf area). The DD treatment also resulted in increased concentrations of abscisic acid (ABA) and its glucose ester in the xylem sap of roots and shoots compared to concentrations in control seedlings (about 200 versus 20 nM). Despite the difference in xylem sap concentrations, total ABA flux to the shoots was similar in the two treatments (1-2 pmol ABA m(-2) leaf area s(-1)) as a result of reduced transpiration in the DD-treated seedlings. Compared with root growth in control plants, root growth increased in the RE-treated plants and decreased in the drying compartment of the WD treatment; however, the RE and WD treatments only slightly reduced leaf expansion, and had no detectable effects on shoot water relations or ABA concentrations of the root and shoot xylem sap. We conclude that short-term soil water depletion affecting only 50% of the root system does not cause a measurable stress response in birch shoots, despite root growth cessation in the fraction of drying soil.     

Effect of simulated acid fog on membrane-bound calcium (mCa) in fir (Abies firma) and cedar (Cryptomeria japonica) mesophyll cells

The decline of virgin fir (Abies firma) forest at Mt. Oyama has been reported. Related field observations suggest that high acidity fog is linked with its decline. However, cedar (Cryptomeria japonica) in the same area shows no symptoms of decline. For assessing effects of acid fog on membrane-bound calcium (mCa) of the leaf mesophyll cells, 9-year-old seedlings of fir (Abies firma) and 8-year-old seedlings of cedar (Cryptomeria japonica) were exposed twice a week to simulated acid fog (SAF at pH 3 with pH 5 as control) for 2 h per day in a chamber during May–December 2007 (except August). Current and 1-year-old needles were collected from seedlings and analyzed at 1-month intervals. For current-year needles of fir, mCa levels in cells exposed to SAF at pH 3 were significantly lower than in cells exposed to pH 5, especially during September 2007–March 2008. In contrast, it is noteworthy that mCa levels of cedar were maintained as virtually constant irrespective of SAF acidity, indicating that fir is more sensitive to acid fog than is cedar. Based on these results, mCa loss by acid fog might also be caused in the declining virgin fir forest at Mt. Oyama.     

Effects of Previous High N Addition on Nutrient Conditions in Above-ground Biomass of a Picea abies Stand in Sweden

The effect of different thawing procedures on seedling quality in Norway spruce (Picea abies) was evaluated. Freezer-stored seedlings were thawed rapidly for 20 h by immersion in water with an initial water temperature of 8°C or thawed more slowly by gradually increasing the temperature in storage over a period of 8 weeks. Seedlings from these treatments were also compared with seedlings thawed rapidly overnight at 15°C. Frost tolerance, carbohydrate content and the time of bud break were used as indicators of the vitality of the seedlings. Seedlings thawed rapidly in water or air showed significantly better frost tolerance after storage than slowly thawed seedlings. The contents of sucrose and raffinose in seedlings thawed rapidly were also significantly higher than in seedlings thawed more slowly. Bud break occurred later in seedlings thawed rapidly than in slowly thawed seedlings. Rapid thawing in water may be a good method to ensure the delivery of high-quality thawed seedlings throughout the planting season.