Alnus Viridis Research Articles

Mountain ash (Sorbus aucuparia) forests of the Central and Southern Alps (Grisons and Ticino, Switzerland – Prov. Verbano-Cusio-Ossola, N-Italy): Plant ecological and phytosociological aspects

Mountain ash (Sorbus aucuparia) is widespread in Europe from sea level to the timberline and reaches its most northern range in N-Norway at 71 °N. Sorbus aucupariaoccurs on acid, dry to moist and mesotrophic to oligotrophic soils. The species often grows in secondary forests together with Alnus viridis, Sambucus racemosa, Betula pendula, Frangula alnus and some Salix spp. In most climax forests mountain ash grows only in the shrub layer. In the subalpine belt, the tree is present in green alder scrub and European larch-Swiss stone pine forests. On some N-exposed mountain slopes of the S-Alps, small mountain ash forests with green alder build the upper forest limit above 1500 m. In this study, ecological and phytosociological aspects of this particular forest community along a N-S-transect from the Swiss Central Alps (Grisons) to the South Alps (Ticino/ N-Italy) were investigated. We consider site conditions, local spread, rejuvenation, tree age structure, infestation and phytosociological aspects of S. aucuparia. The occurrence of A. viridis in the N-S-transect and the role of S. aucupariain the secondary and climax forests have been investigated. While in the green alder scrub (Alnetum viridis) of the North single mountain ash trees are present, alder-mountain ash forests have been found at the S-Alpine sites with S. aucupariacovers 25–80%. Here, the Alnetum viridis is absent, and A.viridis is element of the mountain ash forests. In the montane and lower subalpine zone, S. aucupariawill often be replaced later by beech or other climax trees. Above the upper beech limit, we consider the green alder-mountain ash forests as climax forests. At the driest forest sites, grass species are pre-dominant – mainly Calamagrostis spp. and Avenella flexuosa. Based on the earlier provisional phytosociological name of S-Alpine green alder-mountain ash forests, we suggest the name Alno viridi-Sorbetum aucupariae Hari, Leisinger et Zysset 1993 – according to the first description by HARI et al. (1993). Based on our vegetation records of green alder-mountain ash forests, we propose a new sub-association Alno viridi-Sorbetum aucupariae calamagrostietosum subass. nov.

Growth Response of Aspen and Alder to Fresh and Stockpiled Reclamation Soils

Soil stockpiling is a common reclamation practice used in oil sands mining in the boreal forest region of Canada to conserve soil resources; but stockpiling may have detrimental effects on soil quality and plant growth. We examined growth response of trembling aspen (Populus tremuloides Michx.), a fast-growing early successional tree, and green alder (Alnus viridis (Chaix) DC. ssp crispa (Ait.) Turrill), a nitrogen-fixing shrub, to stockpiling and fertilization treatments on two reclamation soils (forest floor mineral mix (FFMM) and peat mineral mix (PMM)). Aspen and alder seeds were planted and their growth monitored for four months in the greenhouse. We found that unfertilized stockpiled FFMM supported significantly higher aspen and alder aboveground biomass than the other fresh and stockpiled soils. Phosphorus and potassium supply rates were highest in stockpiled FFMM and were positively correlated with aboveground plant biomass. There was no significant difference in aspen and alder aboveground biomasses between unfertilized fresh FFMM and PMM soils. Aspen grown in combination with nitrogen-fixing alder did not experience competition or facilitation except on fresh PMM, where aspen height declined. Fertilization increased both aspen and alder growth and eliminated differences in growth between soil types and stockpiling treatments. Our study showed that individual soil properties are more important for revegetation purposes than type of soil or stockpiling treatment.

Elevational transects of modern pollen samples: Site-specific temperatures as a tool for palaeoclimate reconstructions in the Alps

The potential of quantitatively reconstructing climate from modern pollen assemblages from high mountain environments has been widely debated but seldom tested. We analysed the pollen deposition in 53 surface samples (mosses) in relation to July temperature in two elevational transects in the European Alps. Each surface-sample site was assigned climate data derived from the local-scale climate. We compared our results with a larger calibration set extracted from the European Modern Pollen Database (EMPD) and centred on the European Alps. This also was assigned local climate data. The main calibration set (234 pollen samples) had Alnus harmonized at genus level; in contrast, a second set was selected (174) that retained the taxonomic resolution of Alnus viridis, which is one of the main climate indicators in the timberline ecotone. The overall and individual pollen responses to July temperature were inferred by canonical correspondence analysis (CCA), generalized linear regression (eHOF) and weighted averaging (WA). Quantitative climate reconstructions for each sample site of the two elevational transects were obtained using transfer functions, that is, WA and WA partial least squares (WA-PLS) regressions. In each calibration set, around 30% of the pollen taxa show a relationship with July temperature through monotonic or unimodal functions. The best transfer function obtained has a good statistical performance, with a determination coefficient ( r2) of 0.74. We propose new calibration procedures formulated to include the full climate space of the modelled taxa, as well as to account for uphill pollen transport in the high mountains and for human activity.

In Planta Sporulation of Frankia spp. as a Determinant of Alder-Symbiont Interactions.

The Alnus genus forms symbiosis with the actinobacteria Frankia spp. and ectomycorrhizal fungi. Two types of Frankia lineages can be distinguished based on their ability to sporulate in planta Spore-positive (Sp+) strains are predominant on Alnus incana and Alnus viridis in highlands, while spore-negative (Sp-) strains are mainly associated with Alnus glutinosa in lowlands. Here, we investigated whether the Sp+ predominance in nodules is due to host selection of certain Frankia genotypes from soil communities or the result of the ecological history of the alder stand soil, as well as the effect of the sporulation genotype on the ectomycorrhizal (ECM) communities. Trapping experiments were conducted using A. glutinosa, A. incana, and A. viridis plantlets on 6 soils, differing in the alder species and the frequency of Sp+ nodules in the field. Higher diversity of Frankia spp. and variation in Sp+ frequencies were observed in the trapping than in the fields. Both indigenous and trapping species shape Frankia community structure in trapped nodules. Nodulation impediments were observed under several trapping conditions in Sp+ soils, supporting a narrower host range of Sp+ Frankia species. A. incana and A. viridis were able to associate equally with compatible Sp+ and Sp- strains in the greenhouse. Additionally, no host shift was observed for Alnus-specific ECM, and the sporulation genotype of Frankia spp. defined the ECM communities on the host roots. The symbiotic association is likely determined by the host range, the soil history, and the type of in plantaFrankia species. These results provide an insight into the biogeographical drivers of alder symbionts in the Holarctic region.IMPORTANCE Most Frankia-actinorhiza plant symbioses are capable of high rates of nitrogen fixation comparable to those found on legumes. Yet, our understanding of the ecology and distribution of Frankia spp. is still very limited. Several studies have focused on the distribution patterns of Frankia spp., demonstrating a combination of host and pedoclimatic parameters in their biogeography. However, very few have considered the in planta sporulation form of the strain, although it is a unique feature among all symbiotic plant-associated microbes. Compared with Sp- Frankia strains, Sp+ strains would be obligate symbionts that are highly dependent on the presence of a compatible host species and with lower efficiency in nitrogen fixation. Understanding the biogeographical drivers of Sp+ Frankia strains might help elucidate the ecological role of in planta sporulation and the extent to which this trait mediates host-partner interactions in the alder-Frankia-ECM fungal symbiosis.

Holocene vegetation history and quantitative climate reconstructions in a high-elevation oceanic district of the Italian Alps. Evidence for a middle to late Holocene precipitation increase

We reconstructed the vegetation and climate history during the last 10 ka in a high-elevation sedimentary record (Armentarga peat bog, 2345 m asl) on the southern flank of the European Alps through the study of paleoecological and sedimentary proxies. We included a specific elevational transect of modern Pollen Accumulation Rates for timberline-forming trees and shrubs (Alnus viridis, Pinus sylvestris/mugo, Pinus cembra). Quantitative reconstructions of July temperature and annual precipitation were obtained by applying numerical transfer functions built on an extensive pollen-climate calibration set from the European Alps. Changes in elevational vegetation arrangement were primarily driven by phases of precipitation increase, and to a lesser extent by millennial-scale temperature changes already known from glacier, timberline, chironomids and speleothem records at Alpine scale. Changes in pollen-inferred annual precipitation occurred in three main steps. An early Holocene moderately humid phase is mirrored by the early spread of Alnus viridis dwarf forests. Precipitation started to increase at 6.2 ka cal BP. A further, prominent step forward at the Middle to Late Holocene transition led to the high values of snowfall and runoff characterizing today's oceanic elevational climates of the outer Italian Alps. This change led to timberline depression and grassland expansion. Locally, human impact was weak at the Late Neolithic/Bronze Age transition. This event correlates with lake level oscillations in the northern Mediterranean borderlands, suggesting intensification of southern air masses conveyed by Tyrrhenian cyclones towards windward districts.

Landscape variability of vegetation change across the forest to tundra transition of central Canada

Widespread increases in the productivity of tundra ecosystems and static trends – or even declines – in boreal ecosystems have been detected since the early 1980s using coarse-scale remote sensing. However, intermediate-scale Landsat studies have shown that these changes are heterogeneous and may be related to landscape and regional variability in climate, land cover, topography and moisture availability. In this study, a Landsat Normalized Difference Vegetation Index (NDVI) time-series (1984–2016) was examined for an area spanning the transition from sub-Arctic boreal forest to Low Arctic tundra in central Canada. This was supplemented by analyses of relationships with a suite of environmental variables and in situ measurements of bulk vegetation volume. Results show that NDVI trends were generally positive (i.e. increasing) across the study area but were smallest in the forest zone and largest in the northern tundra zone. More than one-quarter (27%) of un-masked pixels exhibited a significant (p < 0.05) trend and virtually all (99.3%) of those pixels exhibited an increasing, or “greening”, trend. Greening pixels were most common in the northern tundra zone and the southern ecotone zone. Random Forest modeling of the relationship between NDVI and environmental variables indicated that the magnitude and direction of trends varied across the forest to tundra transition. Areas that experienced larger increases in NDVI include: (i) areas where summer temperatures increased; (ii) areas exhibiting predominantly shrub and forest cover; and (iii) locations closer to major drainage systems, further from major lakes, and at lower elevations. Ground validation in the central portion of the study area reveals a strong relationship (R2 = 0.79) between vegetation volume and NDVI for non-tree functional groups and that alder (Alnus crispa) shrublands and open spruce (Picea mariana and P. glauca) woodland with shrubby understories were most likely to exhibit greening. These findings indicate that the largest positive and more significant NDVI trends were associated with increased productivity in shrub-dominated environments, especially at, and north of the treeline in localities with favorable growing conditions. Smaller and less significant NDVI trends in boreal forest environments south of the treeline were likely associated with long-term successional change following disturbance rather than the variables analyzed here.

Ecosystem carbon dynamics differ between tundra shrub types in the western Canadian Arctic

Shrub expansion at high latitudes has been implicated in driving vegetation ‘greening’ trends and may partially offset CO2 emissions from warming soils. However, we do not yet know how Arctic shrub expansion will impact ecosystem carbon (C) cycling and this limits our ability to forecast changes in net C storage and resulting climate feedbacks. Here we quantify the allocation of photosynthate between different ecosystem components for two common deciduous Arctic shrubs, both of which are increasing in abundance in the study region; green alder (Alnus viridis (Chaix) DC.) and dwarf birch (Betula glandulosa Michx., B.). Using 13C isotopic labelling, we show that carbon use efficiency (i.e. the fraction of gross photosynthesis remaining after subtracting respiration) in peak growing season is similar between the two shrubs (56 ± 12% for A. viridis, 59 ± 6% for B. glandulosa), but that biomass production efficiency (plant C uptake allocated to biomass production, per unit gross photosynthesis) is 56 ± 14% for A. viridis, versus 31 ± 2% for B. glandulosa. A significantly greater proportion of recent photosynthate is allocated to woody biomass in A. viridis dominated plots (27 ± 5%), compared to plots dominated by B. glandulosa (4 ± 1%). Allocation of C to belowground pools also differs significantly; after 2.5 weeks we recovered 28 ± 6% of recent photosynthate in root-free soil under B. glandulosa, but under A. viridis we were unable to detect recent photosynthate in the soil. We provide the first evidence that the impact of shrub expansion on Arctic C cycling will be species dependant. Where Betula dominates, ~1/3 of recently photosynthesised C will be rapidly allocated belowground to soil and microbial pools. Where Alnus dominates, more recently fixed C will be allocated to woody biomass. We conclude that models driven by remotely-sensed aboveground canopy characteristics alone (i.e. greenness) will be unable to accurately represent the impact of vegetation change on Arctic C storage.

Riparian defoliation by the invasive green alder sawfly influences terrestrial prey subsidies to salmon streams

AbstractInvasive species in riparian forests are unique as their effects can transcend ecosystem boundaries via stream‐riparian linkages. The green alder sawfly (Monsoma pulveratum) is an invasive wasp whose larvae are defoliating riparian thin‐leaf alder (Alnus tenuifolia) stands across southcentral Alaska. To test the hypothesis that riparian defoliation by this invasive sawfly negatively affects the flow of terrestrial prey resources to stream fishes, we sampled terrestrial invertebrates on riparian alder foliage, their subsidies to streams and their consumption by juvenile coho salmon (Oncorhynchus kisutch). Invasive sawflies altered the composition of terrestrial invertebrates on riparian alder foliage and as terrestrial prey subsidies to streams. Community analyses supported these findings revealing that invasive sawflies shifted the community structure of terrestrial invertebrates between seasons and levels of energy flow (riparian foliage, streams and fish). Invasive sawfly biomass peaked mid‐summer, altering the timing and magnitude of terrestrial prey subsidies to streams. Contrary to our hypothesis, invasive sawflies had no effect on the biomass of native taxa on riparian alder foliage, as terrestrial prey subsidies, or in juvenile coho salmon diets. Juvenile coho salmon consumed invasive sawflies when most abundant, but relied more on other prey types selecting against sawflies relative to their availability. Although we did not find effects of invasive sawflies extending to juvenile coho salmon in this study, these results could change as the distribution of invasive sawflies expands or as defoliation intensifies. Nevertheless, riparian defoliation by these invasive sawflies is likely having other ecological effects that merits further investigation.

Inconsistent relationships between annual tree ring-widths and satellite-measured NDVI in a mountainous subarctic environment

Recent climate warming has intensified efforts to understand patterns of vegetation productivity at northern high latitudes. Remotely-sensed and dendrochronological measurements have indicated significant changes in aboveground vegetation production in these regions, but the relationship between the two indicators remains unclear. We examined the relationship between remotely-sensed data, using the normalized difference vegetation index (NDVI), and annual ring-width indices obtained from trees and shrubs in the boreal mountains of southwest Yukon. A 24-year (1990–2013) trend in annual maximum NDVI was generated from two Advanced Very High Resolution Radiometer (AVHRR) datasets: the Alaska Composite NDVI (1 km), and the third generation Global Inventory Modeling and Mapping Studies (GIMMS3g) NDVI (8 km). Twenty sites were systematically selected for dendrochronological sampling and chronologies were developed for the dominant coniferous (Picea glauca and Picea mariana) and deciduous (Salix glauca, Alnus crispa, and Populus tremuloides) species at each site. NDVI trends indicated low-level greening across much of the region during the 24-year period. However, ring-width trends varied in direction and magnitude and the agreement with annual maximum NDVI was low. Correlations between annual ring-width indices and biweekly NDVI values were also low, although eight coniferous chronologies did show significant positive correlations with GIMMS3g biweekly data, suggesting that radial growth may be reflected in NDVI at some point during the growing season. Reasons for the inconsistent relationships between ring-width and NDVI remain unclear. Future studies should examine the role of climatic variables on the ring-width-NDVI relationship, especially when multiple datasets and various resolutions are being used. Investigating the relative contributions of plant growth, establishment of new plants, and changes in plant resource allocation to NDVI trends are critical to achieve a more functional understanding of the changes occurring in mountainous boreal ecosystems.

Influence of larval outbreaks on the climate reconstruction potential of an Arctic shrub

Arctic shrubs have a strong potential for climate and environmental reconstructions in the chronically understudied regions of the high northern latitudes. The climate dynamics of these regions are important to understand because of large-scale feedbacks to the global climate system. However, little is known about other factors influencing shrub ring growth, possibly obscuring their climate signal. For example, as of yet we are not able to differentiate between herbivory or climatically induced growth depressions. Here, we use one of the most common Arctic shrubs, Alnus viridis as a test case to address this question. We sampled Alnus in Kobbefjord, Greenland, measured shrub-ring width and cell wall thickness and built site chronologies of each parameter. We analysed climate-growth relationships, tested their stability over time and employed a pointer-year analysis to detect growth depressions. We employed bootstrapped transfer function stability tests (BTFS) to assess the suitability of our shrub chronologies for climate reconstruction. Correlations with climate data showed strong significantly positive and stable correlations between summer temperature and ring-width with the exception of the recent decade. A climate reconstruction model failed stability tests, when the complete period of record was used for calibration and verification. Wood anatomy analysis uncovered the occurrence of unusual cell structure (very thin cell walls) in the exceptionally narrow ring of 2004, a recorded insect outbreak year in other parts of Greenland. When excluding the affected ring and a recovery period, the reconstruction model passed all tests, suggesting that the unusual 2004 ring was not climate driven, but rather the result of an insect attack. When combining anatomical analysis with traditional ring-width measurements, we move a step further in potentially distinguishing small rings caused by insect attacks from small rings formed in climatically challenging years. While this study does not provide unambiguous evidence, it does provide potential useful methodological combinations to enable more robust climate reconstructions in areas where climatic records are extremely sparse.

Frankia Diversity in Host Plant Root Nodules Is Independent of Abundance or Relative Diversity of Frankia Populations in Corresponding Rhizosphere Soils

Actinorhizal plants form nitrogen-fixing root nodules in symbiosis with soil-dwelling actinobacteria within the genus Frankia, and specific Frankia taxonomic clusters nodulate plants in corresponding host infection groups. In same-soil microcosms, we observed that some host species were nodulated (Alnus glutinosa, Alnus cordata, Shepherdia argentea, Casuarina equisetifolia) while others were not (Alnus viridis, Hippophaë rhamnoides). Nodule populations were represented by eight different sequences of nifH gene fragments. Two of these sequences characterized frankiae in S. argentea nodules, and three others characterized frankiae in A. glutinosa nodules. Frankiae in A. cordata nodules were represented by five sequences, one of which was also found in nodules from A. glutinosa and C. equisetifolia, while another was detected in nodules from A. glutinosa Quantitative PCR assays showed that vegetation generally increased the abundance of frankiae in soil, independently of the target gene (i.e., nifH or the 23S rRNA gene). Targeted Illumina sequencing of Frankia-specific nifH gene fragments detected 24 unique sequences from rhizosphere soils, 4 of which were also found in nodules, while the remaining 4 sequences in nodules were not found in soils. Seven of the 24 sequences from soils represented >90% of the reads obtained in most samples; the 2 most abundant sequences from soils were not found in root nodules, and only 2 of the sequences from soils were detected in nodules. These results demonstrate large differences between detectable Frankia populations in soil and those in root nodules, suggesting that root nodule formation is not a function of the abundance or relative diversity of specific Frankia populations in soils.IMPORTANCE The nitrogen-fixing actinobacterium Frankia forms root nodules on actinorhizal plants, with members of specific Frankia taxonomic clusters nodulating plants in corresponding host infection groups. We assessed Frankia diversity in root nodules of different host plant species, and we related specific populations to the abundance and relative distribution of indigenous frankiae in rhizosphere soils. Large differences were observed between detectable Frankia populations in soil and those in root nodules, suggesting that root nodule formation is not a function of the abundance or relative diversity of specific Frankia populations in soils but rather results from plants potentially selecting frankiae from the soil for root nodule formation. These data also highlight the necessity of using a combination of different assessment tools so as to adequately address methodological constraints that could produce contradictory data sets.

Interspecific Plant Interactions Reflected in Soil Bacterial Community Structure and Nitrogen Cycling in Primary Succession.

Past research demonstrating the importance plant–microbe interactions as drivers of ecosystem succession has focused on how plants condition soil microbial communities, impacting subsequent plant performance and plant community assembly. These studies, however, largely treat microbial communities as a black box. In this study, we sought to examine how emblematic shifts from early successional Alnus viridus ssp. sinuata (Sitka alder) to late successional Picea sitchensis (Sitka spruce) in primary succession may be reflected in specific belowground changes in bacterial community structure and nitrogen cycling related to the interaction of these two plants. We examined early successional alder-conditioned soils in a glacial forefield to delineate how alders alter the soil microbial community with increasing dominance. Further, we assessed the impact of late-successional spruce plants on these early successional alder-conditioned microbiomes and related nitrogen cycling through a leachate addition microcosm experiment. We show how increasingly abundant alder select for particular bacterial taxa. Additionally, we found that spruce leachate significantly alters the composition of these microbial communities in large part by driving declines in taxa that are enriched by alder, including bacterial symbionts. We found these effects to be spruce specific, beyond a general leachate effect. Our work also demonstrates a unique influence of spruce on ammonium availability. Such insights bolster theory relating the importance of plant–microbe interactions with late-successional plants and interspecific plant interactions more generally.

Modelling the impact of land use changes on peak discharge in the Urseren Valley, Central Swiss Alps

In alpine regions, global climate change will likely alter rain and snowfall patterns and increase the frequency of extreme meteorological events such as floods. These events, combined with land use changes, may pose an immediate hazard to the life and properties of downslope inhabitants and to water resource structures downstream. The aim of this study is to evaluate the impact of land use changes (e.g., areas covered by grassland, green alder, and dwarf shrubs) on peak discharge for different return periods and different scenarios (past, current, and future) in the Urseren Valley in the Central Swiss Alps. In addition to the entire Urseren Valley, we also considered four microcatchments of various sizes and land covers within the valley. We used the ZEMOKOST model, which considers the impact of a wide range of vegetation and channel characteristics on surface hydrology. Results at the catchment scale show an increase in peak discharge for all return periods from 2 to 300years. In two microcatchments, simulation results indicate that expected changes in the vegetation cover will drastically decrease peak discharge in the future for all return periods, by up to 41% (for a 100-year return period). At the catchment scale, although the surface area covered by green alder increases by 38% and the area covered by dwarf shrubs decreases by 26% from the current to the future scenario, the peak discharge increases for all return periods except for the 2- and 5-year return periods. It appears that the drastic decrease of grassland area from the current to future (−52%) scenario is responsible for the slight increase in peak discharge (about 4% for a 100-year period). In addition, surface area covered by dwarf shrub not only decreases from the current to future scenario, but also clusters into more continuous zones damping lateral flow and resulting in such moderate increase. The consistency between observed and simulated peak discharge for a 100-year return period attests the reliability of our modelling outcomes. Careful land use planning taking into account the results of our analysis can help to better manage land and water resources in the region.

ПРИРОДНІ ТЕРИТОРІАЛЬНІ КОМПЛЕКСИ ВЕРХІВ’Я БАСЕЙНУ РІЧКИ ЛАЗЕЩИНА В МЕЖАХ ЧОРНОГОРИ

The article presents the results of the study of the landscape structure of the upper part of the Lazeshchyna basin within the limits of Chornogory. The tracts, streets and highlands were the objects of mapping. The research was carried out according to the methodology of Field Landscape Research by G. P. Miller (1974) with the wide use of literary sources, topographic maps and stock materials (geological, geomorphological maps, maps of Quaternary deposits), aerophotographic and cosmic images, and the ArcGis 10 software environment. Rich landscape features of the study area form six high altitudes: a mild convex denudation alpine-subalpine highlands with white-and-blueberries wilderness and meadow grass on mountain-meadow-brown and mountain-peat and brown soils; sharply concave long-glacial-erosional subalpine highlands with formations of deciduous and coniferous shrubs on mountain-peat and brown soils in a complex with rocky deposits and outcrops of indigenous rocks; mild convex denudation cold forested middle class with the domination of spruce forests on burozems; old-glacial-accumulative wooded middle mountains with the domination of spruce forests on brown soils; steep-eroded erosion-denudation forest of middle with domination of cyprinid and fir-beech- spruce-wood forests on brownfields; terraced bottom of river valleys with cold, humid climates and rivers of flood regime, with formation of fires, gray alder and secondary grass meadows on sod-brown soils and burozems. The morphological structure of highlands is expressed by twenty landscape streams and one hundred and thirty-two tracts. Established that the rough part of the main ridge of Chornogory between the peaks of Hoverla and Petros belongs to the high-altitude area of the miteconvex denudation forest middle middle with the domination of spruce forests on the brownfields, and not to the high-altitude area of the miteconvex denudation Alpine subalpine highlands with white-and-blueberries and wild mushrooms on mountain-meadow-brown-earth and mountain-t'orfyano-brown soils, as previously thought. For the first time, for the territory of the Ukrainian Carpathians, within the terraced bottoms of the river valleys with cool climate and rivers of flood regime, with the formation of feldspar, gray alder and secondary grass meadows on sod-brown soils and burozems, two new rows were discovered and encoded: the convex surfaces of low ridges composed of proluvial (muddy) deposits, represented by the depths, gravel and loam with crushed stone, with moisturite on rubbers; and the surfaces of the terraces are made in the water-glacial sediments represented by boulders, loams and sunsets and boulders and sand-pebble alluvium in the rivers of the year with the formation of fir and green alder on brown soils.

Polymorphism of Chloroplast DNA and Phylogeography of Green Alder (Alnus alnobetula (Ehrh.) K. Koch s. l.) in Asiatic Russia

This paper studies the phylogeography of Alnus alnobetula s. l. in the Asian part of the Russian range with the use of chloroplast DNA (cpDNA) sequences (intergenic spacers trnH-psbA, trnS-trnG, and psaA-trnS). Nine haplotypes were identified as a result of a combination of polymorphism of all sites in 241 plants in 20 populations of A. alnobetula. High interpopulation differentiation (GST = 0.914, NST = 0.928) and a significant phylogeographic structure (NST > GST, p < 0.05) were found. Reconstruction of genealogical relationships of green alder haplotypes revealed five highly divergent genetic lineages: one geographically widespread throughout Siberia and the Urals and several allopatric lines in the Far East of Russia, namely, the Chukotka Peninsula and the mouth of the Yana River, Magadan oblast, Primorye and the central part of Sakhalin Island, and the southern part of Sakhalin Island. Our data confirm that in the past the range of this species in the Far East was fragmented in several refugia that were isolated for a long time in various ice-free regions. This could have contributed to a high level of intraspecific polymorphism of green alder as a result of the divergence of endemic haplotypes, with almost non-overlapping distribution. However, the level of their molecular divergence does not correspond to the level of morphological differences.

Relationships within Capitotricha bicolor (Lachnaceae, Ascomycota) as inferred from ITS rDNA sequences, including some notes on the Brunnipila and Erioscyphella clades

DNA sequences of Capitotricha bicolor from Quercus, Fagus sylvatica, Alnus alnobetula, and Nothofagus, and C. rubi from Rubus idaeus were obtained from apothecia to establish whether specimens from different hosts belong to separate species. The obtained ITS1–5.8S–ITS2 rDNA sequences were examined with Bayesian and parsimony phylogenetic analyses. Intra- and interspecific variation was also investigated based on molecular distances in the ITS region. The phylogenetic analyses supported the specific distinctness of Capitotricha rubi and the Capitotricha from Nothofagus, but also suggest specific distinctness between samples from Quercus, Fagus, and Alnus. The interspecific distances were larger than intraspecific distances for all examined units. The smallest distance was found between the “Alnus alnobetula” and “Fagus sylvatica” units. Two new sequences of Brunnipila are published. Capitotricha, Lachnum, and Erioscyphella are compared to each other based on hair and excipulum characteristics.

Green alder encroachment in the European Alps: The need for analyzing the spread of a native-invasive species across spatial data

Forest regrowth is an ongoing process in the European Alps. In the Unteralptal, a valley in central Switzerland, landscape characteristics show considerable change toward the encroachment of green alder (Alnus viridis (Chaix) DC. = Alnus alnobetula (Ehrh.) K. Koch). Initially, green alder was described to grow on moist, north-facing and steep slopes of high geomorphic activity. However, the recent spreading of green alder described in several studies over the alpine arc questions the ecological habitat described in historic literature. Thus, a time series of aerial photographs and a digital elevation model (DEM) with a resolution of 2m were used to find proxies for green alder encroachment. The cover of “new shrub areas” was analyzed based on relief parameter values and geomorphic landforms. The results show that green alder is spreading on more gentle slopes and well-drained areas, as well as on areas with lower geomorphic activity than anticipated. Thus, the habitat spectrum of green alder is much wider than assumed and encroachment has potentially greater consequences for landscape ecology than expected.

Nitrogen fixation by Alnus species boosts soil nitrous oxide emissions

The aim of this study was to assess how higher soil temperatures and increased nitrogen (N) availability, mediated by the N2 fixation of different Alnus species, affect soil nitrous oxide (N2O) emissions. We measured rates of N2O emission in situ under non‐N2‐fixing tree species or grassland (controls) and under Alnus species by the closed chamber technique along a temperature gradient of 5.7 K from the lowlands to the upper montane belt in Switzerland. Similar soil conditions and representative tree and bush taxa at a given elevation were a key prerequisite for the site selection. Across the 12 test plots, and irrespective of the elevation, N2O emissions were on average 12‐fold larger in Alnus stands than in non‐N2‐fixing vegetation. The mean emission was 1.3 ± 0.2 kg N2O‐N ha−1 under Alnus and 0.1 ± 0.1 kg N2O‐N ha−1 under non‐N2‐fixing vegetation from mid‐June to mid‐October. The largest rates of emission were observed in Alnus viridis (Chaix.) D.C. shrubland at 1680 m a.s.l. (mid‐elevation), with a seasonal emission of 4.2 ± 0.5 kg N2O‐N ha−1. Differences in soil temperature along the elevation gradient did not affect the release of N2O in non‐N2‐fixing vegetation or across the different Alnus species. We conclude that larger N availability through N2 fixation increases N2O emissions in ecosystems even without intense agricultural management. The fast expansion of Alnus viridis across the Alps has been documented mainly in the context of ‘ecological consequences’. Here, we provide evidence that Alnus viridis also adds substantially to greenhouse gas emissions.Highlights We evaluated soil N2O emissions under Alnus and non‐fixing species along a temperature gradient of 5.7 K. Alnus stands emitted on average 12‐fold more N2O than non‐N2‐fixing vegetation. Neither short‐ nor long‐term variation in temperature affected N2O emissions in Alnus stands. During the growing season, soil under Alnus viridis emitted 1.5% of the annual Swiss N2O emission.

Green alder (Alnus viridis) encroachment shapes microbial communities in subalpine soils and impacts its bacterial or fungal symbionts differently.

Since the mid-twentieth century, subalpine grasslands undergo a progressive encroachment by Alnus viridis shrubs. Thanks to its rapid vegetative reproduction, its nitrogen fixing symbiosis with Frankia and its ectomycorrhizal cohorts, green alders are vigorous colonizers that quickly form mosaic of alder patches that evolves into a close canopy shrub community. To better understand how alder encroachment might influence microbial communities in this successional sequence, symbiont distribution, microbial richness and community structure in both soils and nodules were analyzed at three successional stages: grassland, mosaic and forest. Soil analyses were performed in association with measures of nitrification and denitrification, as well as DNA metabarcoding of three bacterial genes (16S rDNA, nifH and amoA) and one fungal gene (ITS1). Our results show that (i) A. viridis encroachment is associated with soil microbial community changes that are in turn, linked to certain soil properties (i.e., pH, C/N ratio and organic matter content), (ii) both taxonomic and N related functional gene structures of bacteria are modified by alder encroachment and (iii) the distribution in soils of its bacterial symbionts (Frankia) is apparently weakly influenced by alder establishment while Alnus-specific ectomyccorrhizae increase with the increase in alder shrub density.

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 &amp; 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.