Pinus Sylvestris Needles Research Articles

The essential oil qualitative and quantitative composition in the needles of Pinus sylvestris L. growing along industrial transects

The aim of this study was to evaluate composition of the essential oils in the needles of Pinus sylvestris growing in the areas affected by a cement factory (CF), and an oil refinery (OR). Volatile components of the needles were analyzed by GC and GC/MS. The most heavily polluted CF stand had significantly higher concentration of gamma-Terpinene, Caryophyllene oxide in the current-year needles, while higher concentration of delta-3-Carene, alpha-Terpinene, gamma-Terpinene and Terpinolene was documented for 1-year-old needles. The most heavily polluted OR stand had a significantly higher concentration of Sabinene+beta-Pinene, 1-epi-Cubenol in the current-year needles and a significantly higher concentration of Camphene, Sabinene+beta-Pinene, Myrcene, alpha-Cadinene, 1-epi-Cubenol in the 1-year-old needles than the least polluted site. Along transects an increase in the amount of some diterpenes and a decrease in the components of the shorter chain essential oils was observed. These effects could be at least partially attributed to SO(2).

Two new antitumor diterpenes from Pinus sylvestris

Two new diterpenes, 15-ethyl-18-methyl pinifolate ( 1) and 18-hydroxy-labda-8(17),13 E-dien-15-acetate ( 2), were isolated from the needles of Pinus sylvestris. Their structures were elucidated by spectroscopic methods, including 2D-NMR spectra. Compound 1 exhibited the significant cytotoxic activity against the human carcinoma cell lines Hela, SK-N-SH and BEL-7402 in vitro.

Changes in nitrogen level and mycorrhizal structure of Scots pine seedlings inoculated with Thelephora terrestris

• We investigated the influence of Thelephora terrestris, an ectomycorrhizal fungus, on the concentration of nitrogen in needles of Pinus sylvestris L. seedlings and their mycorrhizal structure within four seasons of growth. • Seedlings were grown in four treatments: (I) inoculated + 0.030 g N, (II) inoculated + 0.045 g N, (III) non-inoculated + 0.030 g N, (IV) non-inoculated + 0.045 g N under laboratory conditions and later planted in post-agricultural land. • For inoculated treatments, statistically significant differences in N concentration of needles were observed for two- and four-year-old seedlings. The number of ectomycorrhizae and concentration of N in needles were negatively correlated. After four seasons of growth the greatest numbers of ectomycorrhizae were present on seedlings from treatment II, and the smallest on seedlings from treatment IV. • Two-year-old seedlings had been colonized by at least six different fungal taxa, i.e. Cenococcum geophilum, Hebeloma crustuliniforme, Rhizopogon sp., Suillus bovinus, Thelephora terrestris and a non-identified one. Treatments I and II were dominated by the ectomycorrhizae of T. terrestris and their number was significantly greater than in treatments III or IV. On four-year-old seedlings ectomycorrhizae of T. terrestris were dominated in all treatments, while ectomycorrhizae of Hebeloma sp. were not found.

Chemical Composition on Essential Oils from Needles of Pinus sylvestris L. Grown in Northern Lithuania

Content and composition of needle essential oils of Pinus sylvestris (Scots pine) grown in the north of Lithuania have been studied. Volatile components of dried current-year and 1 year old needles were extracted by simultaneous hydrodistillation-extraction and analyzed by GC and GC/MS. The most predominant fraction was found to be monoterpene hydrocarbons (26.4–41.3%), with the major constituents α-pinene (7.0–16.1 %) and δ-3-carene (5.2–14.3 %) in it. Among the oxygenated monoterpenes bornyl acetate was the most dominant constituent (1.1–3.9 %). Sesquiterpene hydrocarbons formed 19.4–26.0 % of the oils; amounts of main sesquiterpenes β-caryophyllene and δ-cadinene were 2.6–5.8 % and 2.3–5.9 %, respectively. α-Cadinol (4.2–8.5 %) and epi-α-cadinol with epi-α-muurolol and α-muurolol (4.0–9.1 %) were the major compounds in oxygenated sesquiterpenes fraction. Diterpenoids (including and tentitatively identified compound) comprised 6.2–13.7 % of the oils. Also, differences in composition of current-year and 1 year old needles were represented in the study. Seventy-one identified component made up 89.1–98.2 % of total oil content. One sample of fresh needles was analyzed in order to compare the composition with oils obtained from dried needles. Relative amount of monoterpene hydrocarbons was significantly higher (71.0 %) in the oil of fresh needles.

Glucose and ammonium additions affect needle decomposition and carbon allocation by the litter degrading fungus Mycena epipterygia

Saprotrophic microorganisms in soils have traditionally been assumed to be carbon (C) limited, since additions of readily assimilable carbohydrates usually result in increased respiration. In many forest soils, however, rapid nitrogen (N) immobilization and increased microbial growth in response to N addition indicate N limitation. Here we test whether this apparent contradiction could be explained by changes in C allocation between microbial growth and respiration (i.e. changed C-use efficiency) under controlled conditions in laboratory microcosms. Respiration, mycelial production and needle mass loss were monitored after application of glucose or ammonium sulphate to Pinus sylvestris needles inoculated with the litter decomposer fungus Mycena epipterygia. Addition of ammonium resulted in a 32% increase in respiration, 31% increase in needle mass loss and increased mycelial production, indicating that both growth and activity of the fungus were N limited. In spite of N limitation, additions of glucose resulted in a 19% increase in respiration but had no effect on mycelial production and led to a 17% decrease in needle mass loss, indicating a reduced C-use efficiency of the fungus. The capacity of individual fungi to adapt their C-use efficiency to C availability implies that additions of labile C could increase respiration even under N-limited conditions.

Differential response of ectomycorrhizal and saprotrophic fungal mycelium from coniferous forest soils to selected monoterpenes

The mycelia of saprotrophic (SP) and ectomycorrhizal (ECM) fungi occur throughout the upper soil horizons in coniferous forests and could therefore be exposed to high concentrations of monoterpenes occurring in the needle litter of some tree species. Monoterpenes are mycotoxic and could potentially affect fungi that are exposed to them in the litter layers. In order to investigate whether monoterpenes typical of coniferous litters could influence fungal communities, we analysed the monoterpene content of freshly fallen needles of Pinus sylvestris, Picea abies and Picea sitchensis. The most abundant monoterpenes were found to be α-pinene, β-pinene and 3-carene. We evaluated the effects of these three monoterpene vapours on the biomass production of 23 SP isolates and 16 ECM isolates. Overall, 75% of ECM isolates and 26% of SP isolates were significantly inhibited by at least one of the monoterpene treatments and both intra- and inter-specific variations in response were observed. Monoterpene concentrations are highest in surface litters. The differential effects on fungal taxa may influence the spatial and temporal distribution of fungal community composition, indirectly affecting decomposition and nutrient cycling, the fundamental ecosystem processes in which fungi have a key role in coniferous forest soils.

Variation in the δ13C of foliage of Pinus sylvestris L. in relation to climate and additions of nitrogen: analysis of a 32‐year chronology

AbstractWe report an analysis of both the long‐ and short‐term drivers of the carbon (C) isotope composition (δ13C) values of current year needles of Pinus sylvestris L. linked to changing atmospheric carbon dioxide (CO2) concentrations (ca) and climate using data from a uniquely long‐term nitrogen (N) fertilization experiment in the north of Sweden (consisting of three N dosage levels and a control treatment) from 1970 until 2002. N loading produced trees with less negative δ13C of foliage, by around 0.45‰ on average, with the difference in δ13C between control and N treatments not dependant upon N dosage. The average δ13C values decreased at a rate of around 0.03‰ yr−1, even after accounting for the Suess effect (the decrease in the atmospheric CO2δ13C due to anthropogenic emissions of isotopically light CO2). This decrease is large enough to cause a significant, progressive change in the δ13C down through a soil profile. Modelled values of plant intrinsic water use efficiency (WUEi) and the ratio of leaf internal to external [CO2] (ci/ca) showed that this was the result of ci increasing in parallel with ca (while ci/ca increased), thus causing little change in WUEi over the 32 years of study. The residuals from the relationships between year and δ13C were used to examine the impact of climate on the interannual variation of C isotope composition of needles. This included the use of a fire hazard index (FHI) model, which integrates climatic factors known to influence plant stomatal conductance and hence δ13C. The FHI produced the best fit with δ13C values when climate data were averaged over the whole growth season (for control plots) and for July for all the N treatments, explaining ca. 60% of the total interannual variation in δ13C. Further, trees from the N treatments appeared more susceptible to air‐humidity‐based climate parameters, as seen from higher correlation coefficients, than were control trees. Thus, our data suggest the possibility of increased susceptibility to drought conditions in ecosystems with moderate to high N deposition rates. Also, there is the possibility that, because there was no apparent change in WUEi of P. sylvestris in this ecosystem over the last 32 years, the rate of sequestration of C into boreal ecosystems may not increase with ca, as has been predicted.

Feeding behavior and performance of Neodiprion sertifer larvae reared on Pinus sylvestris needles

The feeding behavior of herbivorous insects is a crucial element of plant–insect interactions. The quality of food often determines the place of feeding and performance of herbivorous insects. The aim of the study was to show how food quality controls feeding behavior of European pine sawfly ( Neodiprion sertifer Geoffr.), an important pest of young pine plantations. In spring 2003 we observed an outbreak of N. sertifer on 10-year-old Pinus sylvestris L. trees. We found that the larvae fed mainly on 1-year-old needles belonging to the branches where eggs were laid during the previous year. The older (2-year old) and younger (current-year) needles and the needles from the terminal leader (trunk) were eaten by larvae only after all 1-year-old needles were consumed. We conducted two experiments with larvae of European pine sawfly. In the first experiment (May 2003) larvae were released on the first, second or third whorl of Scots pine trees. After 1 and 2 days we recorded the locations where larvae fed. In the next experiment (in May 2004) we reared the larvae in the laboratory using four needle types: 1-year old from branches, 2-year old from branches, 1-year old from terminal leader and 2-year old from terminal leader. In the first experiment larvae passed by the 2-year-old needles with higher content of phenolic compounds and fed on 1-year-old needles. In most cases the larvae fed on the branches and only incidentally on the terminal leader ( χ 2, P < 0.01). The age and type of needles affected duration of insect development and efficiency of ingested food. The duration of development was shorter, the amount of food eaten smaller and the efficiency of ingested food higher, in the larvae raised on 1-year-old needles from branches. Female individuals were twice as big as males, therefore they had longer duration of development and ate more food. The level of total phenolic compounds and nitrogen were significantly different by age and type of needles. Our results indicated that larvae raised on needles high in nitrogen and low in phenolic compounds were characterized by short duration of development. Therefore, it is likely that the chemical composition (food quality) of Scots pine needles, not accident, is responsible for the choice of feeding place for European pine sawfly larvae.

Comparison of the moss Pleurozium schreberi with needles and bark of Pinus sylvestris as biomonitors of pollution by industry in Stalowa Wola (southeast Poland)

Concentrations of heavy metals were determined in the terrestrial bryophyte Pleurozium schreberi and in samples of bark and current and previous year needles of Pinus sylvestris collected along transects around the Stalowa Wola industry center (southeast Poland) and compared with material of the same species from a control site. The suitability of bark and pine needles for use in monitoring of serious heavy metal pollution was investigated. In the examined area current and previous year pine needles can be considered suitable biomonitors for atmospheric pollution for Cu and Zn and bark for only Cu. Bioaccumulation abilities of Cd and Cu in P. schreberi and P. sylvestris current and previous year needles were similar. Current and previous year needles were better accumulators of Mn, Ni, and Zn compared to the moss P. schreberi. Bark was a better accumulator of Cd, Cu, and Ni and an inferior accumulator of Mn compared to P. schreberi in the examined area.

Identification ofLophodermium seditiosumandL. pinastriin Swedish forest nurseries using species‐specific PCR primers from the ribosomal ITS region

SummaryLophodermium seditiosumis a serious needle pathogen on pine, particularly in nurseries, and there is a need to detect the pathogen during its latent phase. The internal transcribed spacer (ITS) regions of the rDNA ofL. seditiosumandL. pinastriwere amplified with universal primers and sequenced. Sequence comparisons of the two species allowed the design of species‐specific primers for the ITS regions. The primers were between 18 and 24 bp long with a minimum of 3 bp differences between the species. These primer pairs did not give any amplification of DNA from any other of the examined fungal species or from healthyPinus sylvestrisneedles. It was also possible to identify eitherL. seditiosumorL. pinastriin infected needles with and without signs of infection using these primer pairs. The method was found to be very useful for detection of latent infections ofL. seditiosuminP. sylvestrisneedles in nurseries.

Local variations in microfungal populations on Pinus sylvestris needles

We studied the fungal colonization of Pinus sylvestris needles in two neighbouring sites, comparing stands of isolated and grouped trees. We observed large variations among the proportions of needles bearing fruit bodies of Cyclaneusma minus, Lophodermium pinastri, Verticicladium trifidum and black lines characteristic of L. pinastri colonization. Variations between sites and within trees were greater than that between stands or between trees. The frequency of L. pinastri colonization was negatively correlated with C. minus fruit body frequency, while the frequency of V. trifidum conidiophores was positively correlated with L. pinastri colonization frequency without fruiting, and negatively correlated with C. minus apothecia frequency. Although L. pinastri black lines and C. minus apothecia were nearly randomly associated on individual needles in each sample, the two fungi occupied different segments when they occupied the same needle. These patterns at needle and sample scales do not explain the negative correlation between the frequencies of these two species observed at larger scales. In each sample, frequency of V. trifidum conidiophores was highest on needles colonized by L. pinastri without fruiting. On individual needles, V. trifidum conidiophores developed on segments colonized by L. pinastri without fruiting, but not on segments bearing fruit bodies of L. pinastri or C. minus. These patterns at needle and sample scales were consistent with the correlations between frequencies observed at larger scales. These results were compared to variations observed with stand age and climate in others studies. The observed variations might result from both microclimate variations and fungal interactions.

Electrophysiological responses of Thaumetopoea pityocampa females to host volatiles: implications for host selection of active and inactive terpenes

AbstractVolatiles from newly cut branches with needles of Pinus sylvestris L. were collected with headspace sampling technique, and then identified and quantified by combined gas chromatographic‐mass spectrometry (GC‐MS). The response of antennae of the female pine processionary moth, Thaumetopoea pityocampa, to these volatiles was recorded by coupled gas chromatographic‐electroantennographic detection (GC‐EAD). Surprisingly, the most common and major monoterpene hydrocarbons (MT), α‐pinene, 3‐carene, and β‐pinene were antennally inactive. Female antennae responded strongly only to four minor MT components, myrcene, β‐phellandrene, trans‐β‐ocimene, and terpinolene. Weaker, but repeatable responses were also found to limonene, cis‐β‐ocimene, and γ‐terpinene. Further EAD recordings with two synthetic MT mixtures supported our findings from the natural material. When separating the two enantiomers of limonene by running different synthetic MT mixtures, the EAD response was found only to the(−)‐enantiomer, but not to the opposite (+)‐enantiomer. EAD‐responses were also found to some less volatile compounds, such as sesquiterpenes (SqT), active at ng‐levels. The sensitivity and specificity of the antenna to a select number of active host MTs and SqTs suggest that these play a role in the host selection process of T. pityocampa females.

Changes in chemical composition of Pinus sylvestris needle litter during decomposition along a European coniferous forest climatic transect

The objective of this investigation was to assess the changes in chemical composition (lignin, cellulose, hemicelluloses, non-structural compounds, N, and ash) of decomposing litter. Standard Pinus sylvestris needle litter, originating from southern Sweden, was incubated in litterbags at 15 sites selected from the Netherlands to south Spain. The changes in chemical composition of this litter were determined using near infrared reflectance spectroscopy. The hypothesis was that standard (chemically uniform) litter decomposing under a range of climates would show different dynamics of accumulation and loss of C-fractions, N, and ash, relative to mass loss. It was shown that, for a given mass-loss value (10, 20, 30, 40, or 50%), the proportion of lignin, cellulose, hemicelluloses, non-structural compounds, N, and ash in the decomposing pine needles differed between sites. Lignin concentration in the litter residue at 50% mass loss ranged from approximately 26 to 43%, cellulose from 19 to 27%, hemicelluloses from 7 to 11%, non-structural compounds from 19 to 25%, N from 0.7 to 1.3%, and ash content from 1.4 to 10.1%. Lignin concentrations showed the highest range of variation. Lignin concentrations during decomposition were positively related to moisture factors as significant correlations were found with actual evapotranspiration and were improved in multiple regressions by the mean annual precipitation or the water surplus. Cellulose was degraded further at sites with high precipitation whereas hemicellulose degradation was related to temperature. This leads to the conclusion that the remaining organic matter produced by standard litter decomposition within the studied climatic range of variations tended to be more recalcitrant under wet and warm climatic conditions than under cold or dry climate.

Mineral nutrients in needles of Pinus sylvestris seed trees after release cutting and their correlations with cone production and seed weight

The effect of release cutting on seed production was investigated in six Scots pine ( Pinus sylvestris L.) seed tree stands and four unreleased stands (forests) in central Sweden. The study was restricted to the uppermost 2 m of the tree crowns. Correlations were analysed between concentrations of nutrient elements in the needles, seed characteristics and numbers of conelets. The mean number of conelets was ca. 65% higher in released seed trees than in control trees in unreleased stands. The mean 1000-seed weight was about 15% higher in the released trees, while the mean percentage of viable seeds was lower in released trees (94%) compared to control trees (98%). However, the number of viable seeds per cone was not significantly different between released and unreleased trees. The concentration of nitrogen, potassium, and phosphorus in needles was ca. 23, 10, and 13% higher, respectively, in released trees. The mean needle dry weight was 20% higher. Nitrogen, potassium and phosphorus concentrations in needles were significantly positively correlated to numbers of conelets as well as to mean 1000-seed weight. None of the other analysed mineral nutrients were significantly correlated to seed production. The mean needle dry weight was significantly positively correlated to the number of conelets, but not to the mean 1000-seed weight. Our conclusion is that improved nutrient status in the seed trees is an important factor explaining the increase in seed production that occurs after release cutting.

Flavonoids from Pinus sylvestris needles and their variation in trees of different origin grown for nearly a century at the same area

Flavonoids in needles of Scots pine planted in 1912–1914 in Poland from seeds originating from different parts of Europe, were isolated, chemically characterised and analysed by HPLC. It was shown that flavonoid profiles were similar in all tested populations and were different from those previously reported for Scots pine seedlings. They included taxifolin, taxifolin 3′- O-glucoside, quercetin as well as quercetin 3- O-glucoside and 3′- O-glucoside. The quercetin 3- O-glucoside could be found only in a trace amount in all samples and quercetin 3′- O-glucoside appeared in all samples regardless their origin. The relative concentration of taxifolin 3′- O-glucoside, quercetin, taxifolin and total flavonoids showed dependence on the origin of seeds; needles from high latitude populations contained smaller amounts of these compounds. Presented data clearly indicate that Scots pine contain glycosidases specific for glycosylation at C-3′ rather than at C-3. Besides, they indicate that long lasting influence of similar environmental factors is not able to change genetic regulatory systems responsible for flavonoid biosynthesis.

Site fertility and the morphological and photosynthetic acclimation of Pinus sylvestris needles to light.

Morphological and photosynthetic acclimation of current-year needles to canopy gradients in light availability (seasonal mean integrated quantum flux density, Q(int)) was studied in the temperate conifer, Pinus sylvestris L., at two sites of contrasting nutrient availability. The nutrient-rich site supported a monospecific P. sylvestris stand on an old-field. The trees were approximately 30 years old and 19-21 m tall. Mean foliar N and P contents (+/- SD) were 1.53 +/- 0.11% and 0.196 +/- 0.017%, respectively. The nutrient-poor site was located on a raised bog supporting a sparse stand of 50- to 100-year-old trees, with a height of 1-2 m, and mean needle N and P contents of 0.86 +/- 0.12% and 0.074 +/- 0.010%, respectively. At both sites, needle thickness (T) and width (W) increased with increasing Qint, and leaf dry mass per unit leaf area (MA) was also greater at higher irradiance. The light effects on MA-the product of needle density (D) and volume to total area ratio (V/AT)-resulted primarily from large increases in V/AT with Qint rather than from modifications of D, which was relatively insensitive to light. Although needle morphology versus light relationships were qualitatively similar at both sites, needles were shorter, and the slopes of W, T, MA and V/AT versus light relationships were lower, at the nutrient-poor than at the nutrient-rich site, indicating that the plasticity of foliar morphological characteristics was affected by nutrient availability. As a result of lower plasticity, needles at the nutrient-poor site were narrower, thinner, and had lower MA at high irradiance than needles at the nutrient-rich site. The maximum carboxylase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Vcmax) and the maximum photosynthetic electron transport rate (Jmax) scaled positively with foliar N and P contents. The correlations were generally stronger with P than with N, suggesting that needle photosynthetic capacity was more heavily limited by the availability of P than of N. The Jmax/Vcmax ratio was positively related to the foliar P/N ratio, indicating that Jmax was more strongly suppressed than Vcmax under conditions of low P availability. Phosphorus and N deficiency also limited the plasticity of foliar photosynthetic characteristics. There was a moderate increase in needle photosynthetic capacity of up to 1.6-fold from the bottom to the top of the canopy at the nutrient-rich site, but net assimilation rates were essentially independent of canopy position at the nutrient-poor site. Stomatal constraints on photosynthesis were similar between the sites, indicating that photosynthetic acclimation was curtailed at the biochemical level. We conclude that the foliar capacity for morphological and physiological acclimation to high light significantly decreases with decreasing nutrient availability in P. sylvestris, and that both N and P availability are potentially important determinants of foliar carbon gain capacities.

Associations between three fungi on pine needles and their variation along a climatic gradient

This paper develops field data analysis and theoretical hypotheses concerning the role of climatic factors and fungal interactions in the control of fungal populations. We studied three ‘resource unit restricted fungi’ colonizing Pinus sylvestris needles along a climatic gradient. We investigated both competition and succession. A general linear model was used for statistical analysis. Despite interference competition at the scale of the individual needle, the first two colonizers, Lophodermium pinastri and Cyclaneusma minus, coexisted and the frequencies of both increased with altitude. This increase seemed to be related to the greater humidity at altitude. The initial stages of development of the final colonizer, Verticicladium trifidum, were strongly dependent on the first two colonizers on the individual needles. The observed decrease in frequency of V. trifidum with increasing altitude may be due to interactions with the early colonizers, with no direct effect of altitude on V. trifidum. Fungal colonization at low and high altitudes can be interpreted by accounting for both climatic effects and fungal interactions expressed as interference and succession.

Pine Needles (Pinus Sylvestris) as a Bioindicator of Sulphur and Heavy Metal Deposition in the Area Around a Pulp and Paper Mill Complex at Kemi, Northern Finland

The determination of sulphur and heavy metals in plants is an integral part of many environmental studies. Pine needles (Pinus Sylvestris) have proved to be suitable air quality indicators for pollutants, especially for sulphur. This study was carried out in the vicinity of Kemi, a town situated on the Gulf of Bothnia in northern Finland. An industrial complex comprising two pulp and paper mills is located in the centre of the area. Scots pine (Pinus Sylvestris) needles were collected from 29 sampling sites. The samples were dried, homogenized and digested with nitric acid. The concentrations of the elements S, Fe, Zn, Ca, V, and Pb were determined by ICP-AES. According to our results pine needles (Pinus sylvestris) appear to be an ideal bioindicator and sampling material for identifying and assessing atmospheric sulphur pollution derived from pulp and paper mills and can complement the information provided by plant mapping studies around pulp and paper mills.

Distribution of three fungi colonising fallen Pinus sylvestris needles along altitudinal transects

This work tested the hypothesis that the abundance of fungal species on coniferous needles is correlated to climatic factors at a regional scale. The proportions of Pinus sylvestris needles colonised by Lophodermium pinastri, Cyclaneusma minus and Verticicladium trifidum were examined along two altitudinal transects in 2 successive years. L. pinastri and C. minus colonisation increased with altitude, whereas that of V. trifidum decreased. The data are discussed in relation to the importance of climatic controls on species distributions.

The effect of reindeer grazing on decomposition, mineralization and soil biota in a dry oligotrophic Scots pine forest

Reindeer grazing in the Fennoscandian area has a considerable influence on the ground vegetation, and this is likely in turn to have important consequences for the soil biota and decomposition processes. The effects of reindeer grazing on soil biota, decomposition and mineralization processes, and ecosystem properties in a lichen‐dominated forest in Finnish Lapland were studied inside and outside a large long term fenced reindeer exclosure area. Decomposition rates of Vaccinium myrtillus leaves in litter bags were retarded in the grazed area relative to the ungrazed area, as well as in subplots from which lichens had been artificially removed to simulate grazing. The effect of reindeer grazing on soil respiration and microbial C was positive in the lichen and litter layers of the soil profile, but retarded in the humus layer. There was no effect of grazing on gross N mineralization and microbial biomass N in the humus and upper mineral soil layer, but net N mineralization was increased by grazing. In these layers soil respiration was reduced by grazing, indicating that reindeer effects reduce the ratio of C to N mineralized by soil microorganisms. Grazing stimulated populations of all trophic groupings of nematodes in the lichen layer and microbe feeding nematodes in the litter layer, indicating that grazing by reindeer has multitrophic effects on the decomposer food‐web. Grazing decreased lichen and dwarf shrub biomasses and increased the mass of litter present in the litter layer on an areal basis, but did not significantly alter total C storage per unit area in the humus and mineral soil layers. The N concentration of lichens was increased by grazing, but the N concentrations of both living and dead Pinus sylvestris needles and Empetrum hermaphroditum leaves were not affected. There was some evidence for each of three mechanisms which could account for the grazing effects that we observed in our study. Firstly, reindeer may have changed the composition and quality of litter input by affecting plant species composition and through addition of N from urine and faeces, resulting in a lack of available C relative to N for decomposer organisms. Secondly, the organic matter in the soil may be older in the grazed area, because of reduction of recent production of lichen litter relative to the ungrazed area. The organic matter in the grazed area may have been in a different phase of decomposition from that in the exclosure. Thirdly, the soil microclimate is likely to be affected by reindeer grazing through physical removal of lichen cover on the ground, and this can have a significant influence on soil microbial processes. This is supported by the strong observed effects of experimental removal of lichens on decomposer processes. The impact of reindeer grazing on soil processes may be a result of complex interactions between different mechanisms, and this could help to explain why the below‐ground effects of reindeer grazing have different consequences to those which have been observed in recent investigations on other grazing systems.