Host range differentiation of spore-positive and spore-negative strain types of Frankia in stands of Alnus glutinosa and Alnus incana in Finland

Host compatibility of different spore-positive (Sp⁺)and spore-negative (Sp^?) strain types of Frankia from alder stands in Finland was studied in Modulation tests with hydrocultures of Alnus glutinosa (L.) Gaertner, A. incana (L.) Moench and A. nitida Endl. Root nodules and soil samples from stands of A. incana (Lammi forest and Hämeenlinna forest) were dominated by Sp ⁺ types of Frankia (coded AiSp⁺ and AiSp⁺ H. respectively), which caused effective root nodules in test plants of A. incana, but failed to induce nodules in A. nitida. In A. glutinosa Frankia strain types AiSp ⁺ and AiSp ⁺ H caused small, ineffective root nodules with sporangia (coded Ineff ^?), which were recognized by the absence or near absence of vesicles in the nodule tissue. Ineffective nodules without sporangia (coded Ineff ^?) were induced on A. glutinosa with soil samples collected at Lammi swamp. The spore-negative strain type of Frankia was common in root nodules of A. glutinosa in Finland (Lammi swamp) and caused effective Sp^? type root nodules (coded AgSp ^?) in hydrocultures of A. incana, A. glutinosa and A. nitida. A different Sp ⁺ strain type of Frankia. coded AgSp⁺ Finland, was occasionally found in stands of A. glutinosa. It was clearly distinguished from strain type AiSp ⁺ by the ability to produce effective nodules on both A. glutinosa and A. incana. The nodulation capacities of soil and nodule samples were calculated from the nodulation response in hydrocutlure and served as a measure for the population density of infective Frankia particles. Sp ⁺ nodules from both strain types had equal and high nodulation capacities with compatible host species. The nodulation capacities of Sp type root nodules from A. glutinosa were consistently low. High frequencies of Frankia AiSp⁺ and AiSp⁺ H were found in the soil environment of dominant AiSp ⁺ nodule populations on A. incana. The numbers of infective particles of this strain type were insignificant in the soil environment of nearby Sp ^? nodule populations on A. glutinosa and in the former field at Hämeen-linna near the Sp⁺ nodule area in Hämeenlinna forest. Strain type AgSp^? had low undulation capacity in the soil environment of both A. incana and A. glutinosa stands, Explanations for the strong associations between Frankia strain types AiSp⁺ and AiSp ^? H and A. incana and between strain type AgSp^? and A. glutinosa are discussed in the light of host specificity and of some characteristics of population dynamics of both strain types. The possible need to adapt the concept of Frankia strain types Sp ⁺ and Sp ^? to strains with some variation in spore development was stressed by the low potentials of strain type AiSp ⁺ H to develop spores in symbioses with hydrocultures of A. incnna.     

Early interactions between Alnus glutinosa and Frankia strain ArI3. Production and specificity of root hair deformation factor(s)

Actinomycetes from the genus Frankia are able to form symbiotic associations with more than 200 different species of woody angiosperms, so called actinorhizal plants. Many actinorhizal plants are infected via deformed root hairs. Factor(s) eliciting root hair deformation in actinorhizal symbioses have been found to be released into the culture medium, but the factor(s) has (have) not yet been characterized. In the present work, we describe the constitutive production of factor(s) by Frankia strain ArI3 causing root hair deformation on Alnus glutinosa . Deformation was detected after 4–5 h of incubation with both Frankia cultures and their cell-free culture filtrates. When culture filtrate was used, deformation was concentration dependent. A contact time of 2 min between culture filtrate and host roots was sufficient to induce subsequent root hair deformation. No root hair deformation on A. glutinosa could be detected with purified Nod factors from Rhizobium meliloti or R. leguminosarum biovar viciae . No correlation was found between Frankia strains belonging to different host specificity groups and their ability to deform root hairs on A. glutinosa. However, strains not able to deform root hairs on A. glutinosa were also unable to nodulate.     

云南省自然休闲地与桤木休闲地地上部分生物量与养分蓄积量的研究

通过样方调查和采样 ,对云南省西盟县新厂乡阿莫村自然条件相似、经历了相同休闲年限的桤木休闲地和自然休闲地的地上部分植被生物量和养分蓄积量进行了比较研究 ,结果表明 ,休闲 3a后 ,桤木休闲地的休闲效果显著高于自然休闲地。表现在桤木休闲地的地上部分生物量高于自然休闲地 ,休闲 6 a后 ,桤木林的地上部分生物量干重达到 6 9,6 4 0 kg/hm2 ,是自然休闲地的 4倍 ;桤木休闲地 N、P、K三大营养元素的地上部分蓄积量 ,经过 2～ 3a超过自然休闲地 ,并在休闲 3a后显著高于自然休闲地 ,休闲 6 a后 ,N蓄积量达到 5 5 7kg/hm2 ,是自然休闲地的 3倍 ,P、K的蓄积量分别达到 4 1kg/hm2 、2 6 5 kg/hm2 ,是自然休闲地的 2倍。目前研究说明桤木种植有改进轮歇农业的明显作用 ,具有在类似地区推广应用的价值。     

Black alder (Alnus Glutinosa (L.) Gaertn.) trees mediate methane and nitrous oxide emission from the soil to the atmosphere

Three-year-old seedlings of black alder (Alnus glutinosa (L.) Gaertn.), a common European wetland tree species, were grown in native soil taken from an alder swamp. Fluxes of methane (CH₄) and nitrous oxide (N₂O) between the tree stem and the atmosphere were determined under controlled conditions. Both CH₄ and N₂O were emitted through the bark of the stem into the atmosphere when the root zone exhibited higher-than-ambient CH₄ and N₂O gas mixing ratios. Flooding of the soil caused a decreased N₂O emission but an increased CH₄ efflux from the stem. Immediately after flooding of the soil, N₂O was emitted from the seedlings' bark at a rate of 350 mol N₂O m^-2 h^-1 whereas CH₄ flux could not be detected. After more than 40 days of flooding CH₄ fluxes up to 3750 mol CH₄ m^-2 h^-1 from the stem were measured, while N₂O emission had decreased below the limit of detection. Gas efflux decreased with increasing stem height and correlated with gas mixing ratios in the soil, indicating diffusion through the aerenchyma as the major path of gas transport. From these results it is assumed that woody species with aerenchyma can serve as conduits for soil-derived trace gases into the atmosphere, to date only shown for herbaceous plants. This, yet unidentified, woody plant pathway contributes to the total greenhouse gas source strength of wetlands.     

The occurrence of amoeboid plastids in the actinorhizal root nodules of Alnus glutinosa (L.) Gaertn.

Abstract. The invasion of the actinomycete Frankia into the root cells of Alnus glutinosa with subsequent nodule formation effects a number of ultrastructural changes in the host cell cytoplasm. Among other changes the amyloplasts rapidly lose their starch and acquire an amoeboid or pleomorphic form. Such plastids occur predominantly in the mature vesicle-containing, nitrogen-fixing cells of the nodule. They lack starch, have an electron dense stroma and a complex lamellar system. This last would appear to be associated with a distinct membranous reticulum which can be extensive. The flexible form of these plastids is mirrored in their ability to enclose portions of host cytoplasm together with organelles and even other plastids. Their close association with cristate mitochondria suggests an active metabolic role in the nodule symbiosis.     

Occurrence of hemoglobin in the nitrogen-fixing root nodules of Alnus glutinosa

A true hemoglobin (Hb) was shown to be present in the root nodules of Alnus glutinosa L. After purification by gel filtration and ion exchange, the Hb formed a stable complex with oxygen. This oxygen complex could then be converted to carboxyhemoglobin by treatment with CO. Optical absorption spectra typical of Hb were observed. The molecular weight was estimated to be 15 100 by gel filtration, and 18 300 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The Hb was largely insoluble when the initial homogenization was done in the absence of a detergent. Under these conditions much of the Hb appears to be associated with clusters of Frankia , the nitrogen-fixing actinomycete that infects plant cells within the nodules. The exact localization of the Hb in vivo is uncertain. The relatively low average concentration of Hb in Alnus nodules suggests that it is either confined to a relatively small fraction of total nodule volume, or has a function other than facilitation of O₂ transport.     

Physiological and morphological responses of red alder and sitka alder to flooding

Red alder (Alnus rubra Bong.) and sitka alder (A. viridis ssp. sinuata [Regel] Löve & Löve) are nitrogen-fixing woody species that grow sympatrically along the Pacific coast of North America. Red alder is found in poorly drained lowlands, as well as in soils of moist upland slopes, whereas sitka alder generally colonizes well-drained soils. To identify factors that contribute to flood tolerance, we conducted greenhouse experiments subjecting both species to a 20-day flood and 10-day recovery and red alder to a 50-day flood and 20-day recovery. We determined the effect of this stress on nitrogenase activity, root and nodule alcohol dehydrogenase (ADH) activity, lenticel and adventitious root development, relative growth rate (RGR), and leaf gas exchange. After 24 h of flooding, nitrogenase activity could not be detected in either species. Limited nitrogenase activity did return in red alder at the end of a 10-day recovery following the 20-day flood, but sitka alder showed no recovery of nitrogenase activity. After 50 days of continuous flooding, red alder nitrogenase activity returned to pretreatment levels. Red alder root and nodule ADH activity was more than twice that of sitka alder under flooded conditions. Sitka alder showed extensive root mortality and leaf abscission over the same 20-day flooding period. Flooded red alder exhibited an initial decline in root RGR, but recovered between days 10 and 20 with the formation of adventitious roots. Furthermore, initiation of adventitious roots in red alder coincided with an increase in stomatal conductance without a similar recovery of carbon dioxide exchange rate. Sitka alder formed few adventitious roots, lost much of its root and leaf biomass, and showed no restoration of growth during flooding or recovery. Different responses of red and sitka alder to flooding serve as a partial explanation for the different patterns of distribution of these species and suggest some adaptations of red alder that permit flood tolerance.     

Genetic diversity and phylogenetic relationships in alder,Alnus firma, revealed by AFLP

Molecular markers for alder,Alnus firma Sieb. et Zucc, have not been studied extensively. Here, we used amplified fragment length polymorphism (AFLP) to investigate genetic relationships among 15 natural populations. EcoRI-ACG + Msel-CTG combinations revealed the highest polymorphism (62.2%). A total of 171 DNA fragments were identified. On average, 58.1% of the AFLP markers that were generated using four primer pairs were polymorphic. Diversity was insignificant among the populations. The combination of a wind-pollinated, outcrossing breeding system along with large population sizes, and the ability to regenerate by stump sprouting may explain the high level of genetic diversity within this species. The majority (98%) of the genetic variance resided within populations. The average number of individuals that were exchanged between populations per generation was very high (N _em = 12.3). Gene dispersal in alder is apparently by seed dispersalvia water and human activity as well as through pollen. Five individuals per population were claded in the same cluster.     

In vitro propagation of mature trees of Alnus incana (L.) Moench.

Mature trees of European grey alder (Alnus incana) were micropropagated on a modified MS medium containing 2.5 M BA, 6.2 mM (500 mg l^-1) NH₄NO₃ and 1.5% glucose. Prior to in vitro culture, mature scions were multiplied through grafting and cutting techniques. Shoot tips from cuttings were established in vitro. After six months of culture, shoots were rooted either in vitro or in vivo and plantlets were transferred to greenhouse conditions.     

Leaf water relations of black alder [Alnus glutinosa (L.) Gaertn.] growing at neighbouring sites with different water regimes

 The tree species black alder [Alnus glutinosa (L.) Gaertn.] typically inhabits wet sites in central Europe but is also successful on well drained soils. To test the physiological adjustment of the species in situ, conductances, transpiration rates and water potentials (Scholander pressure chamber) of black alder leaves were investigated at two neighbouring sites with different water regimes: alder trees at an occasionally water logged alder forest and alder shrubs in a nearby, much drier hedgerow. Additional experiments with alder cuttings in nutrient culture showed that leaf conductances and gas exchange were both strongly influenced by the substrate water potential. In situ however, there was little spatial variability within the different parts of a crown and we found that physiological regulation at leaf level was hardly influenced by different site water regimes or different tree sizes. Diurnal courses of leaf water relations as well as their regulation at the leaf level (e.g. the hyperbolic relationship between conductances and ΔW) were strikingly similar at both sites. Leaf water potential in black alder was shown to be a consequence of immediate transpiration rates, which were high in comparison to other tree species (up to 4 mmol H₂O m^–2 s^–1), rather than the water potentials being a factor that influenced conductance and, therefore, transpiration. The always high leaf conductances and consequent high transpiration rates are interpreted as a strategy to maximise productivity through low stomatal limitation at sites where water supply is usually not limited. However, at the same time this behaviour restricts black alder to sites where at least the deep-going roots can exploit water. Received: 10 September 1998 / Accepted: 12 January 1999     

Effect of changes in nitrogen nutrition on the polyamine content of Alnus glutinosa

Abstract. The principal polyamines in Alnus glutinosa roots, nodules and root pressure sap, putrescine, spermidine and spermine, were quantified by reversed-phase, high-performance liquid chromatography with fluorescence detection following precolumn derivatization with 9-fluorenylmethyl chloroformate and 1-ada-mantanamine. Putrescine was the major component of all tissues and sap. It comprised 70% or more of the polyamine pool except in roots of KNO₃-fed plants, in which similar amounts of putrescine and spermidine were present at levels five-fold lower than plants fed (NH₄)₂SO₄. Polyamine levels in nodules were 50% greater than in roots. The polyamine content of roots and nodules was not altered significantly when the nitrogen nutrition was changed from sole reliance on nitrogen fixation to partial or complete utilization of (NH₄)₂SO₄. However, the polyamine content of root pressure sap from nodulated plants increased almost four-fold when they were fed with increasing concentrations of NH₄NO₃, although the total polyamine content remained low (5mmol m⁻³ sap). The polyamine content of the Alnus root system changed with plant age. In particular, the spermidine content of both roots and nodules was higher in 10- as compared to 16-week-old plants.     

Micropropagation of Alnus cordata (Loisel.) Loisel.

Procedures were developed for micropropagation of Alnus cordata through in vitro axillary shoot multiplication of axillary bud explants cultured in Murashige & Skoog (MS) medium. Establishment of cultures from plants grown in the field was very difficult due to bacterial contamination and phenolic oxidation in explants causing severe browning. Explants were first cultured on an MS medium containing 4.4 M 6-benzyladenine and 87.6 mM sucrose (initiation medium) for 7 days and then transferred to an MS medium containing 1.1 M 6-benzyladenine and 333 mM glucose (multiplication medium) for a further 20–25 days. It was necessary to transfer cultures from initiation medium to multiplication medium after 7 days to minimize excessive callus growth, abnormally thick and brittle leaves, inhibition of shoot elongation, and senescence. Shoot multiplication comparable to the above method was achieved by culture of axillary bud explants in MS medium supplemented with 1.1–4.4 M 6-benzyladenine and 333 mM glucose 4–5 weeks after culture. Shoots rooted in MS medium (1/2 x macro-nutrients) supplemented with 1.2–4.9 M indolebutyric acid. Also, 98% rooting was achieved when cultures were treated with 625 mgl^-1 indolebutyric acid for 24 h at the end of the shoot production stage and rooted in vivo as mini-cuttings. Plantlets established well in soil.     

Effects of elevated oxygen tensions on acetylene reduction in Alnus incana-Frankia symbioses

An open flow-through gas system was used to determine the effect of C₂H₂ and elevated O₂ on acetylene reduction activity (ARA) and respiration of the intact, potted root system of Alnus incana (L.) Moench in symbiosis with Frankia Avcll or with a local source of Frankia . Both symbiotic systems responded to C₂H₂ by an immediate plateau range in ARA. The Plateau in ARA was in some cases followed by a decline of less extent than reported for many legumes. A concurrent decline in net respiration of the root system was on average 8% of the CO₂ efflux prior to C₂H₂ introduction.
Respiration of the root systems in both symbioses responded to elevated oxygen levels in the 10 kPa C₂H₂ atmosphere by an increase of up to 17% of the net respiration prior to C₂H₂ introduction in 21 kPa O₂. In contrast, the elevated oxygen levels resulted in an immediate drop in ARA followed by a minor increase to a stable level lower than that at the preceding, lower oxygen tension. The symbiosis with the local Frankia had lost all ARA when the partial pressure of O₂ exceeded 50 kPa, whereas the symbiosis with Avcll still had some activity at 80 kPa O₂. This difference in tolerance of elevated O₂ clearly shows that the oxygen exclusion mechanisms may be controlled by the microsymbiont in Alnus-Frankia symbioses. The symbiotic systems recovered ARA to a similar extent when returned from elevated O₂ levels to 21 kPa O₂.     

Variations in stomatal density and index: implications for palaeoclimatic reconstructions

The variation in stomatal characters in leaves from one Alnus glutinosa (L.) Gaertn. tree is analysed. Measurements were taken from over 70 sites on the abaxial surfaces of representative ‘sun’ and ‘shade’ leaves having the same insertion point. The mean values of stomatal density and index in the shade leaf were significantly lower (71 and 93%, respectively) than those for the sun leaf. Within leaves, up to 2.5-fold differences in stomatal density values were observed. Contour maps derived from the data reveal non-random trends over the leaf surface. Correlations between stomatal density, epidermal cell density and stomatal index indicate that the variation in stomatal density within leaves arose primarily from local differences in stomatal differentiation, rather than from local differences in leaf expansion. This research demonstrates that a high level of variation in stomatal characters occurs both within and between leaves. We conclude that a well-defined sampling strategy should be used when estimating stomatal characters for (tree) leaves. Furthermore, the leaf's insertion point and situation within the tree crown should be taken into account. We discuss the implications of these findings for palaeoclimatic interpretations and emphasize the need for great caution when drawing conclusions based solely on stomatal characters.     

Nitrate reductase activity, nitrogenase activity and photosynthesis of black alder exposed to chilling temperatures

Actinorhizal ( Frankia -nodulated) black alder [ Alnus glutinosa (L.) Gaertn.] seedlings fertilized with 0.36 m M nitrate (low nitrate fertilizer treatment) or 7.14 m M nitrate (high nitrate fertilizer treatment) and acclimated in a growth chamber for 2 weeks were exposed to 2.5 h of night-time chilling temperatures of −1 to 4°C. Cold treatment decreased nitrogenase activity (acetylene reduction activity) 33% for low nitrate fertilized plants and 41% for high nitrate fertilized plants. Recovery of nitrogenase activity occurred within 7 days after chilling treatment. In contrast, in vivo nitrate reductase (NR) activities of leaves and fine roots increased immediately after chilling then decreased as nitrogenase activities recovered. Fine roots of alder seedlings exhibited NR activities proportional to the amounts of nitrate in the rooting medium. In contrast, the NR activities of leaves were independent of substrate and tissue nitrate levels and corresponded to nitrogenase activity in the root nodules. In a separate experiment, net photosynthesis (PS) of similarly treated black alder seedlings was measured before and after chilling treatments. Net PS declined in response to chilling by 17% for plants receiving low nitrate fertilizer and 19% for plants receiving high nitrate fertilizer. After chilling, stomatal conductance (g_s) decreased by 39% and internal CO₂ concentration (c_i) decreased by 5% in plants receiving the high nitrate fertilizer, whereas plants receiving the low nitrate fertilizer showed no change in g_s and a 13% increase in c_i. Results indicate that chilling stimulates stomatal closure only at the high nitrate level and that interference with biochemical functions is probably the major impact of chilling on PS.     

Ghloroplast DNA and nuclear DNA variation in the sympatric alder species, Alnus cordata (Lois.) Duby and A. glutinosa (L.) Gaertn.

The European alder species, Alnus cordata and A. glutinosa have sympatric distributions on Corsica and southern Italy, where they often grow in mixed populations. An assessment was made of the levels of genetic variation in the chloroplast and nuclear genomes of individual trees from 22 alder populations from Corsica and Italy. The distribution of 10 chloroplast DNA polymorphisms generated by the PCR-RFLP method shows strong geographic structuring of cpDNA haplotypes. Conversely, variation in the nuclear genome, as determined by ISSR analysis, is strongly correlated to the taxonomic affinities of the individual trees analysed. Approximately 50% of ISSR variation (P= 0.00, AMOVA) could be attributed to differences between species. Possible reasons for the incongruence between variation in the chloroplast and nuclear genomes are discussed.     

Diarylheptanoids from Green Alder Bark and Their Potential for DNA Protection

Nine diarylheptanoids, 1 – 9 , catechin ( 11 ), and a phenolic glucoside, 10 , were isolated from the bark of green alder (Alnus viridis). Four of the isolated compounds, i.e., 2, 5, 8, 10 , are new. The structures of 1 – 11 were determined on the basis of spectroscopic data. All isolated compounds were evaluated for their in vitro protective effects on chromosome aberrations in peripheral human lymphocytes using cytokinesis‐block micronucleus (CBMN) assay. Almost all of them exerted a pronounced effect of decreasing DNA damage of human lymphocytes, acting stronger than the known synthetic protector amifostine.     

Long-term effects on the nitrogen budget of a short-rotation grey alder (Alnus incana (L.) Moench) forest on abandoned agricultural land

Short-rotation energy forestry is one of the potential ways for management of abandoned agricultural areas. It helps sequestrate carbon and mitigate human-induced climate changes. Owing to symbiotic dinitrogen (N₂) fixation by actinomycetes and the soil fertilizing capacity and fast biomass growth of grey alders, the latter can be suitable species for short-rotation forestry. In our study of a young grey alder stand (Alnus incana (L.) Moench) on abandoned arable land in Estonia we tested the following hypotheses: (1) afforestation of abandoned agricultural land by grey alder significantly affects the soil nitrogen (N) status already during the first rotation period; (2) input of symbiotic fixation covers an essential part of the plant annual N demand of the stand; (3) despite a considerable N input into the ecosystem of a young alder stand, there will occur no significant environmental hazards (N leaching or N₂O emissions). The first two hypotheses can be accepted: there was a significant increase in N and C content in the topsoil (from 0.11 to 0.14%, and from 1.4 to 1.7%, respectively), and N fixation (151.5 kg N ha⁻¹ yr⁻¹) covered about 74% of the annual N demand of the stand. The third hypothesis met support as well: N₂O emissions (0.5 kg N ha⁻¹ yr⁻¹) were low, while most of the annual gaseous N losses were in the form of N₂ (73.8 kg N ha⁻¹ yr⁻¹). Annual average NO₃-N leaching was 15 kg N ha⁻¹ yr⁻¹ but the N that leached from topsoil accumulated in deeper soil layers. The soil acidifying effect of alders was clearly evident; during the 14-year period soil acidity increased 1.3 units in the upper 0-10 cm topsoil layer.     

Nitrogen cycling in dense plantings of hybrid poplar and black alder

Summary Nitrogen cycling was studied during the third growing season in pure and mixed plantings (33×33 cm spacing) of hybrid poplar and black alder in southeastern Canada. After 3 years, hybrid poplar growth and N content of living tissues in a plot and of individual hybrid poplar plants increased with the proportion of black alder in a planting. No differences were detected among N contents of individual alder plants regardless of plot treatment. Black alder allocated a larger portion of its N to roots than hybrid poplar. Symbiotic nitrogen fixation was estimated to account for 80% of the nitrogen in aboveground alder tissues in the pure treatment using natural¹⁵N dilution. N return in leaf litter was estimated to be 70kg ha^–1 in the pure alder treatment and decreased to a minimum of 20 kg ha^–1 in the pure hybrid poplar plots. No difference was detected among treatments for throughfall N content. Nitrogen concentration in roots and leaf litterfall of black alder was higher than hybrid poplar. Significant soil N accretion occurred in mixed plantings containing two alders to one poplar and pure black alder plantings. Nitrogen availability (NO₃–N) increased with the amount of black alder in a plot. Results suggest that the early increase in nitrogen accumulation of hybrid poplar in mixed treatments can be attributed to an increase of total soil N availability resulting from the input of large amounts of N from easily mineralizable alder tissue.     

Shrub encroachment in the Alps gives rise to the convergence of sub‐alpine communities on a regional scale

Question: How does Alnus alnobetula colonization affect plant communities in sub‐alpine grasslands undergoing land abandonment on a regional scale? Location: Savoie, French Alps. Methods: Variations within and between communities were monitored in 243 plots within three types of stands representing an A. alnobetula colonization chronosequence from grassland to dense vegetation. They were tested for species richness, species strategies and species distribution through multivariate analysis. Regional variations were assessed at three sites along a rain shadow gradient. Results: We detected a convergence of the understorey communities along an A. alnobetula colonization gradient at all sites, associated with a reduction in species richness and the replacement of stress related strategists by competitor strategists. This convergence was unaffected by the rain shadow gradient although it was a key factor of plant distribution. Conclusions: The dense cover and the soil properties provided by A. alnobetula stands buffered the heterogeneity of sub‐alpine communities induced by a rain shadow gradient throughout the study region. It facilitated the development a homogeneous understorey community dominated by competitor related strategists while excluding grasslands stress adapted species through competition processes. The resulting community, although species‐poor, has an interesting conservation value. Accordingly, as a ‘native invader’, A. alnobetula does not display typical traits of biological invaders. Future experimental research on the interactions between A. alnobetula and components of the understorey would be particularly interesting in a severe environment that promotes facilitation among plants.