Alnus Viridis Research Articles

Mechanical site preparation and nurse plant facilitation for the restoration of subarctic forest ecosystems

Sustainable forest management implies successful regeneration following disturbances. Tree regeneration in subarctic ecosystems can, however, be constrained by limitations to seedling establishment related to cold soils, slow decomposition rates, and competition by ericaceous species. We established a field trial at the northern limit of commercial forests in Québec, Canada, to evaluate to what extent mechanical site preparation (MSP) and planting of a nurse N2-fixing species could promote conifer establishment on a site burned in 2007. The experiment comprised four treatments applied in 2010: standard MSP (disc trenching), standard MSP plus planting of Alnus crispa, intensive MSP, with larger furrows than standard MSP, and a control. Main plots were divided and planted in 2011 with Picea mariana (Mill.) Britton, Stearns & Poggenb. or Pinus banksiana Lamb. We monitored seedling survival, growth, nutrition, and microsite over a 3-year period. Results revealed interactions between treatments and planted species. Mechanical site preparation resulted in higher conifer growth relative to the control conditions, and planting Alnus resulted in growth gains similar to those obtained from intensive MSP. We measured competitive interactions between Alnus and the conifers that might eventually cancel out the initial benefits derived from facilitation by planting the nurse species. Longer term monitoring of interspecific interactions is needed to unravel the mechanisms responsible for the facilitative effect and identify the best management practices.

Shrub encroachment by green alder on subalpine pastures: Changes in mineral soil organic carbon characteristics

Shrub encroachment by green alder (Alnus viridis) has been an ongoing process in European mountain areas after land abandonment. The invasion of this N2-fixing and highly productive plant on former subalpine pastures and meadows changes the properties and interactions in the plant-soil system. In the national carbon inventory, it is assumed that green alder woodlands contain the same amount of SOC (~69tCha−1) as productive forests due to the lack of data. To explore the rarely studied change of the soil organic carbon (SOC) pools during the shrub establishment, the study used a chronosequence approach by testing pastures in a pre-encroached status and green alder stands with an age of 15, 25, 40 and 90years, respectively. Besides the estimation of the SOC stock, the soil samples, taken in four different depth layers, were physically fractionated to characterize the quality of the SOC. While pasture grassland contained a median SOC stock (0–30cm) of 100tCha−1, the SOC stocks decreased to 81tCha−1 for 40years old shrub stands. The 90years old green alder bushes showed the significantly highest C stock in the mineral soil with 174tCha−1. Green alder encroachment led to an increase of the particulate organic material (POM) in the mineral soil resulting in a high concentration of unprotected carbon. By contrast, a stabilization of the SOC with the mineral soil phase was not visible during green alder establishment. The study concludes that green alder encroachment causes a significant increase of fresh and unprotected carbon in the soil system compared to subalpine pastures, resulting in a significantly higher total SOC stock (+74tCha−1) after 90years and a doubling of the potential to leach dissolved organic carbon. At landscape level, the ingrowth and establishment of green alder on abandoned subalpine pastures can therefore influence the terrestrial and aquatic systems. Secondly, the SOC stocks of shrub forests are insufficiently represented in the current National Inventory Report.

From pristine forests to high‐altitude pastures: an ecological approach to prehistoric human impact on vegetation and landscapes in the western Italian Alps

Summary This paper addresses the origin and development of the oldest prehistoric pasture in the timberline ecotone known so far in the Alps and its relation to anthropogenic pressure and natural climate change. Palaeoecological and geochemical techniques were applied on the Crotte Basse mire stratigraphy (2365 m a.s.l, northwestern Italy) to describe changes in vegetation composition, forest biomass, land use and fertilization between c. 6400–1800 cal years bp. Subalpine forests dominated by Pinus cembra occurred at very high‐altitude up to c. 5600 cal years bp, when a sharp contraction of woody vegetation took place. This major vegetation shift is matched by increasing charcoal input and markers of pastoral/grazing activities (pollen, dung spores and forms of phosphorus) in the sediment sequence in this small basin. Major phases of landscape change detected in our multiproxy record chronologically match intervals of cumulative probability density of 14C ages from nearby archaeological sites, suggesting that human activity was the factor leading to massive landscape change from the onset of the Copper Age (c. 5600 cal years bp). The change may have been reinforced by climate variability in the period 5700–5300 cal years bp. Sensitivity of woody species to fires was statistically explored (Appendix S1, Supporting Information), revealing negative reactions of P. cembra and Betula to frequent fire episodes and positive reactions of Alnus viridis and Juniperus. Fire episodes do not affect Larix dynamics. Synthesis. Mt. Fallère provides some of the oldest and consistent evidence so far available in the Alps for major anthropogenic pressure at the upper forest limit. As far back as 5600 cal years bp, high‐elevation forest ecosystems were permanently disrupted and the alpine pastures were created. Palaeoecological data enable a clear distinction between a random and sporadic use of the alpine space, typical for Mesolithic and Neolithic societies, and an organized seasonal exploitation of natural resources, starting from the Copper Age onwards. The chronological comparison of independent climate proxies, palaeoecological information and pollen‐based temperature reconstructions sheds light on the relationships between climate and humans since prehistoric times.

Wildfire size alters long‐term vegetation trajectories in boreal forests of eastern North America

AbstractAimWildfire activity is projected to increase under global warming in many parts of the world. Knowledge of the role of these disturbances in shaping the composition of boreal forests is needed to better anticipate their future impacts. Here, we investigate the incidence of wildfire activity (burned biomass, frequency and size) on multi‐millennia vegetation trajectories in two coniferous boreal forest regions that display different types of vegetation composition and relief. We hypothesize that this difference in vegetation results from dissimilar wildfire activity during the Holocene.LocationConifer‐dominated boreal forests in Quebec‐Labrador, eastern North America.MethodsFire and vegetation histories during the last 8000 years were reconstructed and compared through analyses of charcoal and pollen records extracted from nine lacustrine deposits located in two spruce‐moss forests: the western region, co‐dominated by Pinus banksiana, and the eastern region, co‐dominated by Abies balsamea.ResultsBetween 7000 and 2000 cal. yr bp, the western region experienced fewer fires than the eastern region, but they were larger in size. The main species adapted to fire, P. banksiana and Alnus viridis ssp. crispa, progressively co‐dominated with Picea sp.. Conversely, in the eastern region, P. banksiana and A. viridis ssp. crispa were very rare, and Picea sp. co‐dominated with non‐fire‐adapted A. balsamea and Betula sp.. Then, around 2000 cal. yr bp, fires decreased in frequency but were larger in size in the eastern region than in the western one, thus allowing densification of P. banksiana and A. viridis ssp. crispa in these landscapes.Main conclusionsIn the coniferous boreal forests of eastern North America, fire size was relatively more important in determining the long‐term vegetation trajectories in comparison with fire frequency. Changes in the rate of occurrence of large‐fire episodes will have significant impacts on vegetation dynamics over the next decades under continuing warming.

Alder, Nitrogen, and Lake Ecology: Terrestrial-Aquatic Linkages in the Postglacial History of Lone Spruce Pond, Southwestern Alaska.

Diatoms, combined with a multiproxy study of lake sediments (organic matter, N, δ15N, δ13C, biogenic silica, grain size, Cladocera and chironomids, Alnus pollen) from Lone Spruce Pond, Alaska detail the late-glacial to Holocene history of the lake and its response to regional climate and landscape change over the last 14.5 cal ka BP. We show that the immigration of alder (Alnus viridis) in the early Holocene marks the rise of available reactive nitrogen (Nr) in the lake as well as the establishment of a primarily planktonic diatom community. The later establishment of diatom Discostella stelligera is coupled to a rise of sedimentary δ15N, indicating diminished competition for this nutrient. This terrestrial-aquatic linkage demonstrates how profoundly vegetation may affect soil geochemistry, lake development, and lake ecology over millennial timescales. Furthermore, the response of the diatom community to strengthened stratification and N levels in the past confirms the sensitivity of planktonic diatom communities to changing thermal and nutrient regimes. These past ecosystem dynamics serve as an analogue for the nature of threshold-type ecological responses to current climate change and atmospheric nitrogen (Nr) deposition, but also for the larger changes we should anticipate under future climate, pollution, and vegetation succession scenarios in high-latitude and high-elevation regions.

Insights about past forest dynamics as a tool for present and future forest management in Switzerland

Mountain forest ecosystems in central Europe are a product of millennia of land use and climate change, and this historical legacy shapes their vulnerability to projected climate change and related disturbance regimes (e.g. fire, wind throw, insect outbreaks). The transitional and highly dynamic state of present-day forests raises questions about the use of modern ecological observations and modeling approaches to predict their response to future climate change. We draw on records from the different subregions (northern, central and southern Alps and their forelands) in and around the Swiss Alps, which has one of the longest evidence of human land-use in Europe, to illustrate the importance of paleoecological information for guiding forest management and conservation strategies. The records suggest that past land use had different impacts on the abundance and distribution of woody species, depending on their ecology and economic value. Some taxas were disadvantaged by intensified burning and browsing (e.g. Abies alba, Ulmus, Tilia, Fraxinus, Pinus cembra and the evergreen Ilex aquifolium and Hedera helix); others were selected for food and fiber (e.g. Castanea sativa, Juglans regia) or increased in abundance as consequence of their utility (charcoal, acorns, litter and other products) or resistance to disturbance (e.g. Picea abies, Fagus sylvatica, Pinus sylvestris, and deciduous Quercus). Another group of trees increased in distribution as an indirect result of human-caused disturbance (e.g. Betula, Alnus viridis, Juniperus, and Pinus mugo). Knowledge of past species distribution, abundance and responses under a wide range of climate, land use and disturbance conditions is critical for setting silvicultural priorities to maintain healthy forests in the future.

Where to Combat Shrub Encroachment in Alpine Timberline Ecosystems: Combining Remotely-Sensed Vegetation Information with Species Habitat Modelling.

In many cultural landscapes, the abandonment of traditional grazing leads to encroachment of pastures by woody plants, which reduces habitat heterogeneity and impacts biodiversity typical of semi-open habitats. We developed a framework of mutually interacting spatial models to locate areas where shrub encroachment in Alpine treeline ecosystems deteriorates vulnerable species’ habitat, using black grouse Tetrao tetrix (L.) in the Swiss Alps as a study model. Combining field observations and remote-sensing information we 1) identified and located the six predominant treeline vegetation types; 2) modelled current black grouse breeding habitat as a function thereof so as to derive optimal habitat profiles; 3) simulated from these profiles the theoretical spatial extension of breeding habitat when assuming optimal vegetation conditions throughout; and used the discrepancy between (2) and (3) to 4) locate major aggregations of homogeneous shrub vegetation in otherwise suitable breeding habitat as priority sites for habitat restoration. All six vegetation types (alpine pasture, coniferous forest, Alnus viridis (Chaix), Rhododendron-dominated, Juniperus-dominated and mixed heathland) were predicted with high accuracy (AUC >0.9). Breeding black grouse preferred a heterogeneous mosaic of vegetation types, with none exceeding 50% cover. While 15% of the timberline belt currently offered suitable breeding habitat, twice that fraction (29%) would potentially be suitable when assuming optimal shrub and ground vegetation conditions throughout the study area. Yet, only 10% of this difference was attributed to habitat deterioration by shrub-encroachment of dense heathland (all types 5.2%) and Alnus viridis (4.8%). The presented method provides both a general, large-scale assessment of areas covered by dense shrub vegetation as well as specific target values and priority areas for habitat restoration related to a selected target organism. This facilitates optimizing the spatial allocation of management resources in geographic regions where shrub encroachment represents a major biodiversity conservation issue.

Responses of Reclamation Plants to High Root Zone pH: Effects of Phosphorus and Calcium Availability.

Low phosphorus (P) availability and high pH inhibit plant growth in calcareous soils and some oil sands reclamation sites in northeastern Alberta, Canada. In this study, we used a split-root hydroponic setup to test the effects of supplemental P with different calcium (Ca) concentrations and root-zone pH conditions on the growth and physiological response of trees commonly found in the region: paper birch ( Marsh.), trembling aspen ( Michx.), green alder [ (Chaix) DC.], and black spruce [ (Mill.) Britton, Sterns & Poggenb.] seedlings. Plant roots were divided and treated with different combinations of P (0.5 and 15 mmol L), Ca (2 and 50 mmol L), and pH (5.0 and 9.0) for 6 wk. After that time, we measured seedling height, net photosynthesis and transpiration rates, and the concentration of chlorophyll and different elements in the leaves. Plant responses varied between species; black spruce was most resistant to high pH and high Ca concentrations. We did not find any strong beneficial effects of adding P to plants subjected to high root zone pH and high Ca concentration. However, exposure of part of the root system to low pH alleviated the effects of high pH, likely through the improved supply of micronutrients. Because pH conditions are often not uniform in disturbed sites and reclamation soils, our findings may help improve potential reclamation and phytoremediation strategies for the oil sands, bauxite, and coal-combustion residue utilization industries.

Diarylheptanoids from Alnus viridis ssp. viridis and Alnus glutinosa: Modulation of Quorum Sensing Activity in Pseudomonas aeruginosa

Diarylheptanoids from the barks of Alnus viridis ssp. viridis (green alder) and Alnus glutinosa (black alder) were explored for anti-quorum sensing activity. Chemicals with anti-quorum sensing activity have recently been examined for antimicrobial applications. The anti-quorum sensing activity of the selected diarylheptanoids was determined using two biosensors, namely Pseudomonas aeruginosa PAO1 and Chromobacterium violaceum CV026. Although all of the investigated compounds negatively influenced the motility of P. aeruginosa PAO1, four were able to inhibit biofilm formation of this human opportunistic pathogen for 40-70 %. Three of the diarylheptanoids (3, 4, and 5) negatively influenced the biosynthesis of pyocyanin, which is under the control of quorum sensing. Platyphyllenone (7) and hirsutenone (5) were able to inhibit the biosynthesis of violacein in C. violaceum CV026, with 5 being able to inhibit the synthesis of both biopigments. Only one of the tested diarylheptanoids (1) was shown to significantly decrease the production of acyl homoserine lactones (AHL) in P. aeruginosa PAO1, more specifically, production of the long chain N-(3-oxododecanoyl)-l-HSL. On the other side, four diarylheptanoids (2-5) significantly reduced the synthesis of 2-alkyl-4-quinolones, part of the P. aeruginosa quinolone-mediated signaling system. To properly assess therapeutic potential of these compounds, their in vitro antiproliferative effect on normal human lung fibroblasts was determined, with doses affecting cell proliferation between 10 and 100 µg/mL. This study confirms that the barks of green and black alders are rich source of phytochemicals with a wide range of biological activities that could further be exploited as natural agents against bacterial contaminations and infections.

Shrub Expansion of Alnus viridis Drives Former Montane Grassland into Nitrogen Saturation

The N2-fixing shrub Alnus viridis is currently encroaching on montane grasslands in the Alps as a result of reduced land management and complete abandonment. Alnus introduces large amounts of nitrogen (N) into these formerly N-poor grasslands and restricts the succession to montane forests. We studied pools and fluxes of N and the associated C pools in pastures (controls) and adjacent Alnus shrublands at two elevations (1650 versus 1950 m a.s.l.) in three valleys in the Swiss central Alps. The total N and C pools stored in 50-year-old Alnus shrubland did not exceed those in adjacent pastures with a total of approximately 610 g N m−2 in phytomass plus soil (down to 30 cm) at both elevations. In Alnus stands, reduced soil N pools balanced the gain in phytomass N pools, a likely result of a faster turnover of soil N. The soil solution under Alnus was continuously enriched with nitrate, with a total N leaching of 0.79 g N m−2 season−1 (June–October) under 50-year-old stands at both elevations and the highest flux of 1.76 g N m−2 season−1 in 25-year-old shrubland at low elevation, clearly indicating an excess of available N in Alnus shrubland. In contrast, N leaching across all pastures was close to zero (0.08 g N m−2) throughout the season. At the catchment scale, streamlet water showed increased nitrate concentrations with typical flushing peaks in spring and autumn, provided more than one fifth of the catchment area was covered by Alnus shrubs. We conclude that the expansion of Alnus rapidly converts centuries-old, N-poor grassland into N saturated shrubland, irrespective of elevation, and it reduces the C storage potential of the landscape because the Alnus dominance constrains re-establishment of a natural montane forest.

Postglacial vegetation history of Orcas Island, northwestern Washington

The revegetation of islands following retreat of Pleistocene glaciers is of great biogeographical interest. The San Juan Islands, Washington, feature regionally distinctive xerophytic plant communities, yet their vegetation history, as it relates to past climate and sea level, is poorly known. We describe a 13,700-year-old pollen record from Killebrew Lake Fen and compare the vegetation reconstruction with others from the region. The data suggest that the narrow channels surrounding Orcas Island were not a barrier to early postglacial immigration of plants. Between 13,700 and 12,000 cal yr BP, Pinus, Tsuga, Picea, Alnus viridis, and possibly Juniperus maritima were present in a mosaic that supported Bison antiquus and Megalonyx. The rise of Alnus rubra-type pollen and Pteridium spores at ca. 12,000 cal yr BP suggests a warming trend and probably more fires. Temperate conifer taxa, including Cupressaceae, Pseudotsuga, Tsuga heterophylla, and Abies, increased after 11,000 cal yr BP and especially in the last 7000 cal yr BP. After 6000 cal yr BP, Pseudotsuga and Cupressaceae dominated the vegetation. The last 1500 yr were the wettest period of the record. Due to its rain shadow location, Orcas Island experienced drier conditions than on the mainland during most of the postglacial period.

Structural differences in diarylheptanoids analogues from Alnus viridis and Alnus glutinosa influence their activity and selectivity towards cancer cells

Diarylheptanoids represent a group of plant secondary metabolites that possess multiple biological properties and are increasingly recognized for their therapeutic potential. A comparative study was performed on structurally analogous diarylheptanoids isolated from the bark of green (Alnus viridis) and black alder (Alnus glutinosa) to address their biological effects and determine structure-activity relationship. The structures and configurations of all compounds were elucidated by NMR, HR-ESI-MS, UV and IR. Diarylheptanoids actions were studied in human non-small cell lung carcinoma cells (NCI-H460) and normal keratinocytes (HaCaT). A. viridis compounds 3v, 5v, 8v and 9v that possess a carbonyl group at C-3 were considerably more potent than compounds without this group. A. viridis/A. glutinosa analogue pairs, 5v/5g and 9v/9g, which differ in the presence of 3′ and 3″-OH groups, were evaluated for anticancer activity and selectivity. 5v and 9v that do not possess 3′ and 3″-OH groups showed significantly higher cytotoxicity compared to analogues 5g and 9g. In addition, these two A. viridis compounds induced a more prominent apoptosis in both cell lines and an increase in subG0 cell cycle phase, compared to their A. glutinosa analogues. 5v and 9v treatment triggered intracellular superoxide anion accumulation and notably decreased mitochondrial transmembrane potential. In HaCaT cells, 9v and 9g with a 4,5 double bond caused a more prominent loss of mitochondrial transmembrane potential compared to 5v and 5g which possess a 5-methoxy group instead. Although green alder diarylheptanoids 5v and 9v displayed higher cytotoxicity, their analogues from black alder 5g and 9g could be more favorable for therapeutic use since they were more active in cancer cells than in normal keratinocytes. These results indicate that minor differences in the chemical structure can greatly influence the effect of diarylheptanoids on apoptosis and redox status and determine their selectivity towards cancer cells.

Length of cold stratification period affects germination in green alder (Alnus viridis(Chaix) DC. subsp.crispa(Aiton) Turrill) seed collected from northwestern Alberta

Alnus viridis (Chaix) DC. subsp. crispa (Aiton) Turrill (Betulaceae), commonly known as green alder or mountain alder, is a boreal shrub used to revegetate disturbed lands because of its ability to persist and flourish in adverse conditions. Cold stratification, as a seed pretreatment, has been effective in breaking the embryo dormancy of green alder seed; however, the recommended duration of cold stratification varies from 0 to 60 d. To determine the optimum time for seed collection and the impact of duration of cold stratification, seed was collected from 3 locations in 2013. One location was chosen for collection of seed over 3 consecutive mo. Seed was subjected to 4 cold stratification treatments at +4 °C (39.2 °F), and we included a non-treated control. Mean germination time was significantly lower with cold-stratified seed than with the non-stratified seed. Green alder seed showed more rapid and uniform germination when cold stratified for 2 wk or 6 wk as compared to 12 wk of stratification or non-stratified. Germination rate of green alder seed was similar over a 3-mo collection period from late summer to fall.

Water and solute dynamics during rainfall events in headwater catchments in the Central Swiss Alps under the influence of green alder shrubs and wetland soils

AbstractIn the Swiss Alps, shrubs (e.g. Alnus viridis (Chaix) DC) are encroaching into formerly open habitats. The shrub encroachment might affect soil hydrological properties, which in turn influence runoff generation. Moreover, alder species (Alnus spp.) are known to affect chemical soil properties (e.g. increase of nitrate concentrations in the soil solution) and can therefore alter the water quality of stream water. In our study, we investigated four small alpine headwater catchments to assess the influence of shrub encroachment and wetland soils on stream water geochemistry during storm runoff. Stream water was sampled in the growing season of 2010 at hourly intervals during one single rainfall event. Stable isotope values (δ18O) of stream water (ranging from −13.8 to −8.5‰) and rainfall (bulk mean δ18O value of about −5.6‰) during the single event were used to estimate the fraction of event water in stream discharge. Continuously measured electrical conductivity in the growing seasons of 2010 and 2011 was used to infer information on runoff generation during 15 rainfall events. Riparian wetland soils were flushed by a high fraction of event water of up to 72% during peak discharge, which increased the dissolved organic carbon export during the single rainfall event. Besides the atmospheric input through nitrate in rainwater, the expected expansion of green alder shrubs in the region, associated with increasing number and intensity of summer rainfall events in the future, might increase the episodic export of nutrients such as dissolved organic carbon and NO3− from these catchments. Copyright © 2015 John Wiley & Sons, Ltd.

Reconstruction of Holocene vegetation dynamics at Lac de Bretaye, a high-mountain lake in the Swiss Alps

A deeper understanding of past vegetation dynamics is required to better assess future vegetation responses to global warming in the Alps. Lake sediments from Lac de Bretaye, a small subalpine lake in the Northern Swiss Alps (1780 m a.s.l.), were analysed to reconstruct past vegetation dynamics for the entire Holocene, using pollen, macrofossil and charcoal analyses as main proxies. The results show that timberline reached the lake’s catchment area at around 10,300 cal. BP, supporting the hypothesis of a delayed postglacial afforestation in the Northern Alps. At the same time, thermophilous trees such as Ulmus, Tilia and Acer established in the lowlands and expanded to the altitude of the lake, forming distinctive boreo-nemoral forests with Betula, Pinus cembra and Larix decidua. From about 5000 to 3500 cal. BP, thermophilous trees declined because of increasing human land use, mainly driven by the mass expansion of Picea abies and severe anthropogenic fire activity. From the Bronze Age onwards ( c. 4200–2800 cal. BP), grazing indicators and high values for charcoal concentration and influx attest an intensifying human impact, fostering the expansion of Alnus viridis and Picea abies. Hence, biodiversity in alpine meadows increased, whereas forest diversity declined, as can be seen in other regional records. We argue that the anticipated climate change and decreasing human impact in the Alps today will not only lead to an upward movement of timberline with consequent loss of area for grasslands, but also to a disruption of Picea abies forests, which may allow the re-expansion of thermophilous tree species.

The biogeographical status of Alnus crispa (Ait.) Pursch in sub-Arctic southern Greenland: Do pollen records indicate local populations during the past 1500 years?

Phytogeographical studies of south-western Greenland suggest that Alnus crispa is not native to the far south of the island. Palynological investigations dating to the 1970s concluded that this was the case throughout the Holocene, with the regular occurrences of Alnus seen in pollen diagrams from this region explained as the result of long-distance transport of alder pollen from Canada. Recently, macrofossil evidence from an archaeological site in southern Greenland has emerged that indicates that alder was amongst the fuel resources available to the Norse settlers around AD 1000–1400. In light of this discovery, we present data from 13 pollen diagrams produced since 2008 to re-examine the past status of Alnus within southernmost Greenland over the last 1500 years. Only at one site with a very large pollen source area do Alnus pollen frequencies regularly exceed a threshold which may be interpreted as indicating a regional presence for the plant. This pattern is argued to be consistent with the presence of a small but variable regional population of the plant, perhaps restricted in its distribution to the inland district of Vatnahverfi.

Holocene environmental changes in southern Kamchatka, Far Eastern Russia, inferred from a pollen and testate amoebae peat succession record

High resolution palaeoenvironmental records in Far-Eastern Russia are rare, and the Kamchatka Peninsula is among the least studied areas of the region. This paper describes a record spanning the last ca. 11,000yr, obtained from a bog in the southern part of Kamchatka. The radiocarbon dated core was analysed for pollen, testate amoebae, charcoal and loss-on-ignition (LOI).The vegetation during the early Holocene was dominated by grasses (Poaceae), birch (Betula) and heath (Ericaceae p. p.). Around 10,300calyr BP there was a substantial change in the vegetation cover to shrub alder (Alnus viridis s.l.) stands with sedges and ferns (Polypodiophyta) as well as herbs such as meadow rue (Thalictrum) in the understory. In the surroundings of Utka peatlands started to form. The variations in the vegetation cover were most probably caused by climatic changes. At the beginning of sediment accumulation, before 10,300calyr BP, the composition of the vegetation points to cooler summers and/or decreased annual precipitation. Around 10,300calyr BP, changes in vegetation occurred due to rising temperatures and/or changed water regimes. Increased abundancies of dry indicating testate amoebae after 9100calyr BP point to intermediate to dry soil conditions. Between 8600 and 7700calyr BP tree alder (Alnus incana) was widely spread at the site which probably indicates optimal environmental conditions. The tephra layer at 381–384.5cm (ca. 8500calyr BP) produces a strong impact on the testate amoebae assemblages. At 7700calyr BP there was a sudden drop of A. incana in the local vegetation. From this time on, A. incana and also A. viridis decrease continuously whereas Betula gradually increases. The upper part of the sequence (after 6300calyr BP) shows higher abundancies of meadowsweet (Filipendula) and sweet gale (Myrica) pollen. After 6300calyr BP, changes in testate amoebae demonstrate variable soil moisture conditions at the site. Between 3700 and 1800calyr BP, wet conditions dominate as dry indicating testate amoebae decrease. After 1800calyr BP soil conditions become more variable again but this time with dry dominating testate amoebae.In contrast to surrounding regions, there is no evidence of trees such as spruce or larch growing in the surroundings of the site even though those trees are characteristic of many eastern Siberian sites. This difference might be because of the maritime influence of the Okhotsk Sea. Even dwarf pine (Pinus pumila), which is currently widely dispersed in northern Kamchatka, became part of the local vegetation only during the last 700yr.

New nomenclature combinations in the green alder species complex (Betulaceae).

The name Alnus viridis (Chaix) DC., based on Betula viridis Chaix (1785), has traditionally been attributed to green alders although it is based on a later basionym. Alnus alnobetula (Ehrh.) K. Koch based on Betula alnobetula Ehrh. (1783) is the correct name for green alders. In light of the increasing use and recognition of the name Alnus alnobetula (Ehrh.) K. Koch in the literature. I herein propose new nomenclatural combinations to account for the Japanese and Chinese subspecies respectively: Alnus alnobetula subsp. maximowiczii (Callier ex C.K. Schneid.) J. Chery and Alnus alnobetula subsp. mandschurica (Callier ex C.K. Schneid.) J. Chery. Recent phylogenetic analyses place these two taxa in the green alder species complex, suggesting that they should be treated as infraspecific taxa under the polymorphic Alnus alnobetula.

Antimicrobial activity of the diarylheptanoids from the black and green alder

Antimicrobial activity of fourteen diarylheptanoids isolated from the bark of black and green alder against twelve bacterial species (five Gram-positive and seven Gram-negative) and eight fungal strains has been reported. The most sensitive bacterial species were Klebsiella pneumoniae and Pseudomonas aeruginosa (Gram-negative), and Streptosporangium longisporum and Bacillus subtilis (Gram-positive). Among fungal strains the most sensitive to the diarylheptanoids were Fusarium equiseti, F. tricinctum, Candida albicans, and Saccharomyces cerevisiae. Oregonin (8), platyphyllenone (13), hirsutenone (14), (5S)-5-hydroxy-1,7-bis(4-hydroxyphenyl)heptan-3-one-5-O-β-d-apiofuranosyl(1 → 6)-β-d-glucopyranoside (2), and platyphylloside (1) were the most active diarylheptanoids against both bacteria and fungi, especially against fungi. Eleven of fourteen investigated diarylheptanoids exhibited stronger antifungal activity than standards nystatin and fluconazole against C. albicans and eight against S. cerevisiae. Structure/activity analysis revealed the importance of the enone moiety in the structure of diarylheptanoids for the antifungal activity. Significant antifungal activity and high content of oregonin (8) and hirsutenone (14) in the black alder bark chloroform/methanol (1:1) extract recommend the use of these compounds as easily accessible potential antifungal remedies.

Unusually early flowering of alder in Vienna: first report of Alnus × spaethii in Austria, combined LM and SEM study of alder species and impact on pollen allergy sufferers

Different species of alder cause hay fever symptoms in pollen allergy sufferers within Europe: Alnus glutinosa (black alder), A. incana (grey alder), A. viridis (green alder) and more recently A. × spaethii (japonica × subcordata; Spaeth’s alder). In Austria, the alder pollen season usually lasts from January to April (until June in the mountains due to later flowering of A. viridis). The pollen season started very early in 2014, namely by the end of December 2013 in Vienna with the first pollination of alder. Such an early flowering around Christmas is known for A. × spaethii and was first recognized as problem in Switzerland. Up to now, this alder species was not reported in Austria. A sample including twigs, leaves, catkins and pollen from Switzerland was compared with an unusually early flowering alder in Vienna. The pollen of these (Alnus × spaethii) and in addition from black and green alder was analysed by light microscopy and scanning electron microscopy to find possible morphological differences or similarities in their pollen morphology. The general morphology revealed that A. × spaethii is present in Austria (planted in a park) and was responsible for the first burden on pollen allergy sufferers during the alder pollen season in Vienna, although pollen data revealed no significant alder pollen concentrations. The results emphasize the importance of monitoring phenology for pollen information.