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

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

Ozone flux over a Norway spruce forest and correlation with net ecosystem production

Daily ozone deposition flux to a Norway spruce forest in Czech Republic was measured using the gradient method in July and August 2008. Results were in good agreement with a deposition flux model. The mean daily stomatal uptake of ozone was around 47% of total deposition. Average deposition velocity was 0.39 cm s⁻¹ and 0.36 cm s⁻¹ by the gradient method and the deposition model, respectively. Measured and modelled non-stomatal uptake was around 0.2 cm s⁻¹. In addition, net ecosystem production (NEP) was measured by using Eddy Covariance and correlations with O₃ concentrations at 15 m a.g.l., total deposition and stomatal uptake were tested. Total deposition and stomatal uptake of ozone significantly decreased NEP, especially by high intensities of solar radiation.     

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

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

Effects of acid rain on growth and nutrient concentrations in Scots pine and Norway spruce seedlings grown in a nutrient-rich soil

The effects of artificially applied acid precipitation on growth and nutrient concentrations of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) seedlings were investigated in a long-term acid irrigation experiment in field conditions. Seedlings of northern and southern origin were planted in boxes containing peat and composted soil rich in nutrients, and sprinkler irrigated with water acidified with nitric and sulphuric acids to pH 3 or pH 4 for periods varying from two to three and a half growing seasons during 1986-1989. Water irrigated (pH 5.4-7.6) and non-irrigated groups of seedlings were also included in the experiment. At the end of the experiment needles, main and lateral shoots and roots were collected from the seedlings for the determination of height growth and biomass partitioning, and for the analysis of S, N, Mg, P, K, Ca, Mn and Fe concentrations. The treatment effects compared to the irrigated control were studied using multivariate analyses of variance and covariance. In the pine seedlings the total dry matter production increased by 25-70% compared with the irrigated controls when the total wet deposition to the seedlings exceeded 67 kg S ha(-1) and 36 kg N ha(-1) (e.g. after two growing seasons' exposure of the pH 3 treatment). The increase was mainly due to an increase in needle dry weight (54-72% greater at pH 3) and root weight (20-65% greater at pH 3), whereas the height growth or shoot weight growth were less affected. The northern provenance pine seedlings responded more clearly to the pH 3 irrigation than the southern ones. The treatments had no consistent effects on any of the growth variables studied in the spruce seedlings, however. The pines had higher root and foliage Ca concentrations as a result of the acid irrigation, whereas in spruce, acid rain decreased the Ca concentration in needles and shoots. Root Mn and Fe concentrations were higher in both species as a result of the pH 3 treatment. A higher soil conductivity and Ca concentration resulted from the prolonged pH 3 treatment. The results strongly support the hypothesis that the long-term growth and nutrient allocation response of conifers to acid precipitation is dependent both on the tree species and on the nutritional status of the soil.     

Replacing monocultures with mixed-species stands: Ecosystem service implications of two production forest alternatives in Sweden

Whereas there is evidence that mixed-species approaches to production forestry in general can provide positive outcomes relative to monocultures, it is less clear to what extent multiple benefits can be derived from specific mixed-species alternatives. To provide such insights requires evaluations of an encompassing suite of ecosystem services, biodiversity, and forest management considerations provided by specific mixtures and monocultures within a region. Here, we conduct such an assessment in Sweden by contrasting even-aged Norway spruce (Picea abies)-dominated stands, with mixed-species stands of spruce and birch (Betula pendula or B. pubescens), or spruce and Scots pine (Pinus sylvestris). By synthesizing the available evidence, we identify positive outcomes from mixtures including increased biodiversity, water quality, esthetic and recreational values, as well as reduced stand vulnerability to pest and pathogen damage. However, some uncertainties and risks were projected to increase, highlighting the importance of conducting comprehensive interdisciplinary evaluations when assessing the pros and cons of mixtures.     

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

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

Comparison of VOC emissions between air-dried and heat-treated Norway spruce (Picea abies), Scots pine (Pinus sylvesteris) and European aspen (Populus tremula) wood

Heat-treated wood is an increasingly popular decoration material. Heat-treatment improves dimensional stability of the wood and also prevents rot fungus growth. Although production of heat-treated wood has been rapidly increasing, there is only little information about the VOC emissions of heat-treated wood and its possible influences on indoor air quality. In the present study, VOC emissions from three untreated (air-dried) and heat-treated wood species were compared during a four weeks test period. It appeared that different wood species had clearly different VOC emission profiles. Heat-treatment was found to decrease VOC emissions significantly and change their composition. Especially, emissions of terpenes decreased from softwood samples and aldehydes from European aspen samples. Emissions of total aldehydes and organic acids were at the same level or slightly higher from heat treated than air-dried softwood samples. In agreement with another recent study, the emissions of furfural were found to increase and those of hexanal to decrease from all the wood species investigated. In contrast to air-dried wood samples, emissions of VOCs were almost in steady state from heat treated wood samples even in the beginning of the test.     

Fluxes of inorganic and organic arsenic species in a Norway spruce forest floor

To identify the role of the forest floor in arsenic (As) biogeochemistry, concentrations and fluxes of inorganic and organic As in throughfall, litterfall and forest floor percolates at different layers were investigated. Nearly 40% of total As(total) input (5.3g Asha(-1)yr(-1)) was retained in Oi layer, whereas As(total) fluxes from Oe and Oa layers exceeded the input by far (10.8 and 20g Asha(-1)yr(-1), respectively). Except dimethylarsinic acid (DMA), fluxes of organic As decreased with depth of forest floor so that <10% of total deposition (all <0.3g Asha(-1)yr(-1)) reached the mineral soil. All forest floor layers are sinks for most organic As. Conversely, Oe and Oa layers are sources of As(total), arsenite, arsenate and DMA. Significant correlations (r>/=0.43) between fluxes of As(total), arsenite, arsenate or DMA and water indicate hydrological conditions and adsorption-desorption as factors influencing their release from the forest floor. The higher net release of arsenite from Oe and Oa and of DMA from Oa layer in the growing than dormant season also suggests microbial influences on the release of arsenite and DMA.     

Regional variation in surface properties of Norway spruce and scots pine needles in relation to forest decline

Measurements of leaf wettability (contact angle), amounts of epicuticular wax and of surface dust are reported for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L) Karst) trees growing at 12 sites in Europe from SW Germany to NE Scotland. At each site, three year classes (current year, 1 and 2-year-old) of needles were sampled from the mid-crown of up to 12 trees. Trees were selected at random from two strata, those showing visible decline symptoms (i.e. loss of needles or discoloration) and those apparently healthy. Needles for analysis were taken from apparently healthy (green) shoots in both cases. There were no significant differences between 'declining' and 'healthy' trees within sites, suggesting that leaf surface properties reflect environmental exposure rather than plant response. There were significant differences between sites, particularly for Norway spruce, which may be related to environmental factors including air pollution. Contact angles were consistently smaller at low-altitude sites in Britain and The Netherlands than at high-altitude sites in Germany where forests show decline symptoms. Leaf wettability decreased (contact angles increased) with wax amount and increased with dust amount. Leaf surface properties integrate environmental influences over long periods, and may be useful in identifying sites 'at risk' of developing decline symptoms, but causal relationships cannot be deduced without further direct experimentation.     

Ozone exposure-response relationships for biomass and root/shoot ratio of beech (Fagus sylvatica), ash (Fraxinus excelsior), Norway spruce (Picea abies) and Scots pine (Pinus sylvestris)

Current-year seedlings of beech, ash, Norway spruce and Scots pine were exposed during one growing season to different, but moderate, ozone (O(3)) scenarios representative for Switzerland (50, 85, 100% ambient, 50% ambient+30 nl l(-1)) in open-top chambers (OTCs) and to ambient O(3) concentrations in the field. Biomass significantly decreased with increasing O(3) dose in all species except for spruce. Losses of 25.5% (ash), 17.4% (beech), 9.9% (Scots pine) were found per 10 microl l(-1) h accumulated O(3) exposure over a threshold concentration of 40 nl l(-1) during daylight hours (AOT40). Ratios of root/shoot biomass (RSR) also significantly decreased with increasing AOT40 levels in beech and ash, but not in Norway spruce and Scots pine. The data show that the deciduous species beech and ash were more susceptible to O(3) with respect to RSR and biomass than the coniferous species Norway spruce and Scots pine.     

Modelling of stomatal conductance and ozone flux of Norway spruce: comparison with field data

It has been proposed that stomatal flux of ozone would provide a more reliable basis than ozone exposure indices for the assessment of the risk of ozone damage to vegetation across Europe. However, implementation of this approach requires the development of appropriate models which need to be rigorously tested against actual data collected under field conditions. This paper describes such an assessment of the stomatal component of the model described by Emberson et al. (2000. Modelling stomatal ozone flux across Europe. Environmental Pollution 110). Model predictions are compared with field measurements of both stomatal conductance (g(s)) and calculated ozone flux for shoots of mature Norway spruce (Picea abies) growing in the Tyrol Mountains in Austria. The model has been developed to calculate g(s) as a function of leaf phenology and four environmental variables: photosynthetic flux density (PFD), temperature, vapour pressure deficit (VPD) and soil moisture deficit (SMD). The model was run using climate data measured on site, although the SMD component was omitted since the necessary data were not available. The model parameterisation for Norway spruce had previously been collected from the scientific literature and therefore established independently from the measurement study. Overall, strong associations were found between model predictions and measured values of stomatal conductance to ozone (GO(3)) and calculated stomatal ozone flux (FO(3)). Average diurnal profiles of GO(3) and FO(3) showed good agreement between the field data and modelled values except during the morning period of 1990. The diurnal pattern of ozone flux was determined primarily by PFD and VPD, as there was little diurnal variation in ozone concentration. In general, the model predicted instances of high ozone flux satisfactorily, indicating its potential applicability in identifying areas of high ozone risk for this species.     

Impact of atmospheric deposition on the status of planted Norway spruce stands: A comparative study between sites in southern Sweden and the northeastern Czech Republic

Six Norway spruce stands (Picea abies L.) in southern Sweden and six in the northeastern Czech Republic, 12 stands in total, were selected for short-term investigations during the summer and autumn of 1991. In each of the plots, an assessment of foliar damage and dendrometric measurement of the trees was made. Soil and leaf samples were collected and analyzed for their chemical composition. After statistical evaluation of the most important correlations, it was concluded that the main cause of tree damage in both countries was through the acidification of the soils. In both countries, but especially in the Czech Republic, heavy metal accumulation in the humus layer was observed. The main results of the study were the discovery of the similarity of damage processes in the two countries, despite the differences in their geographic location and ambient air pollution levels     

Foliar sulphur species in pine: a new indicator of a forest ecosystem under air pollution stress

An eleven-year foliar sulphur (S) monitoring program was carried out from 1976 to 1986 near a sulphur recovery-gas plant in west-central Alberta, Canada, as part of a case study designed to determine the effects of chronic, low concentration sulphur gas emissions on the forest ecosystem surrounding the gas plant. Measurements of both foliar total sulphur (ST) and foliar inorganic sulphur (SO4-S) concentration in lodgepole x jack pine trees at the end of each of the 11 growing seasons were taken to provide an indication of S loading of the forest from industrial sulphur emissions. To measure the state of the forest ecosystem, foliar ST was separated into foliar accumulated sulphur (inorganic sulphur or SO4-S) and foliar assimilated sulphur (organic sulphur or S0) and the ratio of SO4-S/S0 taken. Foliar S0 was calculated as the difference between foliar ST and foliar SO4-S. The median SO4-S/S0 ratio, with all three years of needles considered, varied from 0.29 at a reference location (AV) to 0.88 at the location with the highest stress (AI). The corresponding mean values ranged from 0.3 at the reference location to 2.2 at the location of highest stress. The mean seasonal photosynthetic rate of current year's foliage of the pine trees and soil pH were reduced at a stressed location (AI) compared to the reference location (AV), between 1976 and 1981. Over this same time period the mean foliar SO4-S/S0 ratio increased from 0.4 +/- 0.1 to 1.0 +/- 0.3 at the stressed location (AI) and remained nearly the same at the reference location (AV) at 0.3 +/- 0.1. This research suggests that the foliar SO4-S/S0 ratio is a useful indicator of the state of forest ecosystems under S air pollution stress. It is concluded that foliar S separated into various fractions has potential as an early warning environmental management tool.     

Effect of fertilisation on the potassium and radiocaesium distribution in tree stands (Pinus sylvestris L.) and peat on a pine mire

This paper compares the effects of single and repeated fertilisation on the contents of potassium, 134Cs and 137Cs in different Scots pine compartments at different levels above ground and in the peat profile 9 years after the Chernobyl disaster. The material was collected from a ditch spacing and fertilisation experiment in Finland. Above a needle potassium concentration of 3.0 mg g(-1) in composed crown samples, 137Cs and 134Cs concentrations remained at about the same level but below that the values were higher on average. This potassium value corresponded to the potassium concentrations of 3.5-3.6 mg g(-1) in the current-year needles of two topmost whorls. The result indicates an enhanced radiocaesium uptake by pine trees under severe potassium deficiency. Fertilisation with potassium-containing fertilisers decreased the caesium uptake considerably. The inhibiting effect of fertilisation on caesium uptake by trees seemed to be fairly long lasting. Fertilisation had sped up the penetration of caesium downwards in the peat profile and its moving out of the active circulation of elements between soil and plants.     

The spatial distribution of different elements in and on the foliage of Norway spruce growing in Switzerland

This study centres around the question of how far the analysis of spruce needles (Picea abies L.) provides a suitable tool for detecting and describing large-scale air pollution, primarily by heavy metals, in Switzerland. For that reason 1637 spruce shoots from 833 sites were analysed, relationships between the different elements were calculated and maps of their spatial distribution drawn. The results show that needle analysis is a valid instrument for the identification of various air pollutants in Switzerland. The element best suited is Pb, followed by some others like Mo, Fe, Cd or S. The most heavily polluted areas in Switzerland are the midlands, and in the north and north-west. Their spatial distribution suggests that in these areas the indicator elements are derived from local sources.     

The use of light and electron microscopy to assess the impact of ozone on Norway spruce needles

Light (LM) and transmission electron (TEM) microscopy were used to study previously specified ozone symptoms in the foliage of Norway spruce. The three youngest green needle generations from twenty mature trees in two stands on sites of different soil fertility at Asa, southern Sweden, were sampled in 1999. The critical dose of ozone, expressed as AOT40, was 6,362 ppb.h. LM showed ozone-specific symptoms: decreased chloroplast size with electron dense stroma advancing gradually from the outer to the inner cell layers, being most severe in the needle side facing the sky. The symptoms were expressed as ozone syndrome indices at the needle generation, tree and stand levels. The index had higher values at the low fertility site. TEM was used to confirm the LM results. The study shows that LM can be used for diagnosis of the impact of ozone on conifers in the field.     

Dissecting the ecosystem service of large-scale pollutant retention: The role of wetlands and other landscape features

Various features of a landscape contribute to the regulating ecosystem service of reducing waterborne pollutant loading to downstream environments. At local scales, wetlands have been shown to be effective in retaining pollutants. Here, we investigate the landscape-scale contribution to pollutant retention provided by multiple wetlands. We develop a general analytical model which shows that the retention contribution of wetlands and other landscape features is only significant if a large fraction of the total waterborne pollutant transport passes through them. Next, by means of a statistical analysis of official data, we quantify the nutrient retention contribution of wetlands for multiple sub-catchments in two Swedish Water Management Districts. We compare this with the retention contribution of two other landscape features: the waterborne transport distance and major lakes. The landscape-scale retention contribution of wetlands is undetectable; rather, the other two landscape features account for much of the total nutrient retention.     

Effects of ozone on foliar leaching in Norway spruce (Picea abies L. Karst): confounding factors due to NOx production during ozone generation

Previous experiments with conifers fumigated with O(3), produced by air-operated electric discharge ozonators, have provided evidence that O(3) increases the leaching of NO(3)(-), NH(4)(+), K(+), Ca(2+), Mg(2+) and some other cations from needles, when the trees are treated with acid mist. This evidence has provided the foundation of the ozone-acid mist hypothesis of spruce decline. We report experiments with Norway spruce saplings fumigated with purified and unpurified O(3). The results show that the accumulation of NO(3)(-) in the needles arises from the rapid deposition of N(2)O(5) and HNO(3) formed from N(2) in the ozonator. An increase in removal of NH(4)(+), Na(+), Ca(2+), Mg(2+), Zn(2+) and Mn(2+) from the needles during soaking in H(2)SO(4), pH3, was also observed, which was related to the increase in NO(3)(-) but was independent of O(3) concentration. It is concluded that results of previous experiments cited in support of the ozone-acid mist hypothesis arose from effects which were at least partly caused by N(2)O(5) produced as a contaminant, and were incorrectly attributed to ozone. Other effects, such as growth stimulations, visible symptons, enhanced frost sensitivity, and infestation by pests or pathogens, which have been attributed to O(3) generated by electric discharge in air, should be interpreted with caution. Future experiments with ozone must eliminate this problem by either using O(2)-driven ozonators, or by purifying the output from air-driven ozonators using cold and/or water traps.     

The impact of constituent ions of acid mist on assimilation and stomatal conductance of Norway spruce prior and post mid-winter freezing

Norway spruce seedlings were sprayed twice weekly with one of a range of artificial mists at either pH 2.5, 3.0 or 5.6, for three months. The mists consisted of either (NH4)2SO4 (pH 5.6), NH4NO3 (pH 5.6), water (pH 5.6), HNO3 (pH 2.5), H2SO4 (pH 2.5). In late December 1988 and early January 1989 the light response of assimilation and stomatal conductance were assessed in the laboratory following a 4-day equilibration period at 12 degrees C. The intact trees were then subjected to a mild (-10 degrees C), brief (3 h) frost in the dark and the recovery of light saturated assimilation (Amax) was followed during the subsequent light period. The same trees were then subjected to a second 3 h (-18 degrees C) frost. The recovery of Amax during the next day was followed. All ion-containing mists stimulated Amax and apparent quantum yield relative to control trees, irrespective of pH. The mists containing SO4 made stomatal conductance unresponsive to light flux density and caused the stomata to lock open. Frosts of -10 degrees C and -18 degrees C did not inhibit the Amax of control trees for longer than 200 min into the light period. In contrast, the ion-containing mists exerted a significant inhibitory effect upon the recovery of Amax. Nitric acid inhibited Amax to 35% of the pre-frost value, whilst the remaining treatments inhibited Amax between 15% and 40% of the pre-frost value. It is concluded that SO4 causes increased mid-winter frost sensitivity and NO3 ameliortes this effect. The results are discussed in relation to forest decline.