North Atlantic Oscillation seesaw effect in leaf morphological records from dwarf birch shrubs in Greenland and Finland

The North Atlantic Oscillation (NAO) determines wind speed and direction, seasonal heat, moisture transport, storm tracks, cloudiness and sea-ice cover through atmospheric mass balance shifts between the Arctic and the subtropical Atlantic. The NAO is characterized by the typical, yet insufficiently understood, seesaw pattern of warmer winter and spring temperatures over Scandinavia and cooler temperatures over Greenland during the positive phase of the NAO, and vice versa during the negative phase. We tested the potential to reconstruct NAO variation beyond the meteorological record through the application of a microphenological proxy. We measured the Undulation Index (UI) in Betula nana epidermal cells from herbarium leaf samples and fossil peat fragments dating back to 1865—exceeding most meteorological records in the Arctic—to estimate imprints of spring thermal properties and NAO in Greenland and Finland. We found negative relations between Greenland UI and late winter, spring and early summer NAO, and mostly positive, but not significant, relations between Finland UI and NAO in years with pronounced NAO expression. The direction of the UI response in this common circumpolar species is, therefore, likely in line with the NAO seesaw effect, with leaf development response to NAO fluctuations in northern Europe opposing the response in Greenland and vice versa. Increased knowledge of the UI response to climate may contribute to understanding ecological properties of key Arctic species, whilst additionally providing a proxy for NAO dynamics.

Reconstruction of climate and ecology of Skagit Valley, Washington, from 27.7 to 19.8 ka based on plant and beetle macrofossils

Glacial lake sediments exposed at two sites in Skagit Valley, Washington, encase abundant macrofossils dating from 27.7 to 19.8 cal ka BP. At the last glacial maximum (LGM) most of the valley floor was part of a regionally extensive arid boreal (subalpine) forest that periodically included montane and temperate trees and open boreal species such as dwarf birch, northern spikemoss, and heath. We used the modern distribution and climate of 14 species in 12 macrofossil assemblages and a probability density function approach to reconstruct the LGM climate. Median annual precipitation (MAP) at glacial Lake Concrete (GLC) was ~50% lower than today. In comparison, MAP at glacial Lake Skymo (GLS) was only ~10% lower, which eliminated the steep climate gradient observed today. Median January air temperature at GLC was up to 10.8°C lower than today at 23.5 cal ka BP and 8.7°C lower at GLS at 25.1 cal ka BP. Median July air temperature declines were smaller at GLC (3.4°C–5.0°C) and GLS (4.2°C–6.3°C). Warmer winters (+2°C to +4°C) and increases in MAP (+200 mm) occurred at 27.7, 25.9, 24.4, and 21.2–20.7 cal ka BP. These changes accord with other regional proxies and Dansgaard–Oeschger interstades in the North Atlantic.

Genetic diversity of Betula nana in Sweden and conservation implications for protection of relict Polish populations

The natural range of the dwarf birch (Betula nana L.) includes the boreal, subarctic and arctic regions of Europe, Asia and North America, where it is relatively common. In Poland, it is a relict species occurring in fragmented populations. Using the random amplification of polymorphic DNA (RAPD) technique, we investigated the genetic diversity of the four Swedish populations representing a part of the continuous range of dwarf birch. With the knowledge of the level of genetic diversity of a population from a continuous distribution, we can assess the genetic status of polish populations and answer the question if habitat fragmentation and a decrease in population size lead to a loss in genetic diversity. Knowledge of genetic diversity is important for species conservation, especially to predict their ability to respond to environmental pressures. We found that the populations Abisko, Malbo, Gällivare and Storlien, which are located at the edge of the natural range of B. nana and occupy different habitats, are genetically diverse to varying degrees. The northern populations from Abisko and Gällivare showed a lower level of genetic polymorphism than the population from Malbo, the southernmost site of dwarf birch in Sweden. The data presented indicate higher genetic diversity existed within populations, whereas genetic differentiation between populations was lower. The high level of genetic differentiation within B. nana populations that were analysed in the present study may be explained by a limited capacity for dispersal among populations via both pollen and seeds. We found that the level of genetic diversity in one of the Polish populations of B. nana is comparable to that in areas in Scandinavia where populations are large and continuous. Based on these studies, we conclude that the “Linje” population has sufficient genetic resources.

Recent greening driven by species-specific shrub growth characteristics in Nunatsiavut, Labrador, Canada

Satellite remote sensing is a popular approach for identifying vegetation change in northern environments; however, disentangling ecological processes causing variability in spectral indices remains a challenge. Here, we aim to determine how shrub characteristics differ between low and rapidly greening areas near Nain, Nunatsiavut, Canada. Using a cross-scale approach, we combined remotely sensed spectral greening trends (Normalized Difference Vegetation Index; Landsat Collection 1; 1985-2018) with shrub dynamics derived from ring-widths of green alder (Alnus alnobetula) and dwarf birch (Betula glandulosa). Differentiation of spectral greening classes appears to be driven by the distribution of shrub species. Alder were taller, grew faster, had more recent stem initiation than dwarf birch, and were dominant in rapid greening subplots. In low greening subplots, alders were co-dominant with dwarf birch, whose dominant stems initiated more gradually, were shorter, and had lower rates of vertical growth. The radial growth of both shrub species was favoured by warm winter temperatures and precipitation, whereas rapid greening alder was also favoured by warm summer temperatures. Further shrub growth will likely be enhanced under continued climate warming if moisture does not become limiting. This research demonstrates the importance of species identity in determining rates of spectral greening in northern environments.

Lichens buffer tundra microclimate more than the expanding shrub Betula nana

Background and Aims In tundra systems, soil-borne lichens are often the dominant groundcover organisms, and act to buffer microclimate extremes within or at the surface of the soil. However, shrubs are currently expanding across tundra systems, potentially causing major shifts in the microclimate landscape. Methods Here, we compared soil temperature and moisture underneath the dwarf birch Betula nana and seven abundant lichen species in subalpine Norway. We also examined mixtures of lichens and dwarf birch, an intermediate phase of shrubification, and measured several functional traits relating to microclimate. Key Results We found that all lichen species strongly buffered the daily temperature range, on average reducing maximum temperatures by 6.9 °C (± 0.7 SD) and increasing minimum temperatures by 1.0 °C (± 0.2 SD) during summer. The dwarf birch had a much weaker effect (maximum reduced by 2.4 °C ± 5.0 SD and minimum raised by 0.2 °C ± 0.9 SD). In species mixtures, the lichen effect predominated, affecting temperature extremes by more than would be expected from their abundance. Lichens also tended to reduce soil moisture, which could be explained by their ability to intercept rainfall. Our trait measurements under laboratory conditions suggest that, on average, lichens can completely absorb a 4.09 mm (± 1.81 SD) rainfall event, which might be an underappreciated part of lichen-vascular plant competition in areas where summer rainfall events are small. Conclusions In the context of shrubification across tundra systems, our findings suggest that lichens will continue to have a large effect on microclimate until they are fully excluded, at which point microclimate extremes will increase greatly.

Palynological diagrams of Holocene sediments and ice wedges at the mouth of the Seyakha River (Zelenaya), Yamal Peninsula

This article examines the sections of the high floodplain of the Seyakha River (Zelenaya) and sections of Holocene peat layers with ice wedges on the third terrace. Palynospectra from sediments and ice wedges of the high floodplain are characterized by a rhythmic fluctuations typical to floodplain facies. The presence of spruce pollen is related to resedimentation, since spruce pollen is detected in the samples with the composition of verifiably resedimented palynomorphs around 10% or higher. The change in composition of the pollen of Siberian pine, scots pine, and birch tree is associated with a change in wind drift, since fluctuations in the composition of the pollen of these taxonomic units do not correlate with fluctuations in resedimented palynomorphs. Therefore, the three periods of increased wind drift and possible increase in pollen productivity can be determined based on mid-period contrast changes in the structure of palynospectra. At the same time, the local peak of cereals is replaced three times by the maximum pollen of dwarf birch and alder. The absence of larch trunks can be substantiated by fires, the traces of which are observed in the section, as well as that larch at the northern limit of its habitat has crumbly wood tissue, which is being rapidly destroyed. Tree limb, needles, and cones usually remain, while the wood tissue is absent. It is assumed that ice wedges formed here 8.5-6 thousand years ago during a single cycle of the change in wind direction and speed , when prevalence of birch tree pollen with some alder pollen at a relatively low pollen concentration was replaced by the dominance of gramineae pollen, and then, dwarf birch pollen in the spring pollen rain. Palynospectra of these ice wedges indicates an increase in the sum of positive temperatures from 8.3 to 6 thousand years.

Shrub and dwarf shrub communities of Sangilen Plateau

The paper presents a detailed ecological and caenotic characteristic of dwarf shrub and shrub communities growing in the highmountain belt of the Sangilen Plateau. The communities investigated were referred to the class of Loiseleurio-Vaccinietea Eggler 1952. The dwarf birch thickets with prevalence of Betula rotundifolia and the high incidence of Caragana jubata, Juniperus pseudosabina, J. sibirica, Pentaphylloides fruticosa, Salix glauca, Spiraea alpina were referred to the union of Carici tristis–Betulion rotundifoliae Zibzeev et al. 2018 of the order of Betuletalia rotundifoliae Mirkin at al. ex Chytrý Pešout et Anenkhonov 1993. Communities with dominant calciphilous shrubs and dwarf shrubs, such as Rhododendron adamsii, Caragana jubata, Salix berberifolia, S. reticulata, were referred to the union of Saxifrago oppositifoliae–Rhododendrion adamsii Zibzeev et al. 2018 of the order of Rhododendro-Vaccinietalia Br.-Bl. ex Daniels 1994.

Merger of Betula tatewakiana (Betulaceae) from northern Japan with northeast Asian B. ovalifolia based on ploidy level

It has been controversial whether Betula tatewakiana, a dwarf birch distributed in Hokkaido of northern Japan, is an endemic species or a synonym of B. ovalifolia broadly distributed in northeast Asia. The endemic hypothesis is based on the idea that B. tatewakiana is diploid while B. ovalifolia is tetraploid and that they are separated based on the ploidy level; however, no chromosome data have actually been published before. Resolving the taxonomic problem is crucial also in judging the conservation priority of B. tatewakiana in a global perspective. Our chromosome observation revealed that B. tatewakiana is tetraploid as well as B. ovalifolia. We also conducted morphological observations and clarified that B. tatewakiana is morphologically identical to B. ovalifolia in white hairs and dense resinous glands respectively on adaxial and abaxial leaf surfaces, in which they differ from closely related species in the same section Fruticosae. We conclude that the hypothesis that B. tatewakiana is a Hokkaido endemic based on the ploidy level is not supported and that B. tatewakiana should be merged with B. ovalifolia.

Lateglacial and Holocene floras and faunas from the Salpetermosen area, north-east Sjælland, Denmark

The Salpetermosen area in north-east Sjælland, Denmark, was deglaciated about 18 000 to 17 000 years ago. Melting of bodies of stagnant glacier ice led to the for-mation of kettle holes, which contain Lateglacial and Holocene sediments with remains of plants and animals that provide information on the past flora and fauna of the area. During the Allerød period, open forests with Betula pubescens (downy birch) characterised the area, the flora included light-demanding species such as Arctostaphylos uva-ursi (bearberry), Empetrum nigrum (crowberry) and rare Populus tremula (aspen), Betula nana (dwarf birch) and Rubus saxatilis (stone bramble), as well as the thermophilous swamp plant Oenanthe aquatica (fine-leaved water dropwort). During the Younger Dryas, the vegetation was characterised by dwarf-shrub heaths dominated by Betula nana, but including Dryas octopetala (mountain avens), Salix herbacea (least willow), Arctostaphylos alpina (alpine bearberry,) and rare Betula pube-scens, as well as the thermophilous plants Urtica dioeca (stinging nettle) and Lychnis flos-cuculi (ragged robin). The Early Holocene forests were dominated by Betula pubescens, Populus tremula and Pinus sylvestris (scots pine), but included rare Betula nana. Alnus glutinosa (alder) arrived at c. 10 000 cal. years BP. The calciphilous sedge Cladium mariscus (fen-sedge) and the macrolimnophyte Najas marina (spiny naiad) were common. The Late Holocene flora included the acidophilous plant Scheuchzeria palustris (rannoch-rush).

Analysis of the state of spruce forest crops in the Republic of Tatarstan

Насаждения ели в Республике Татарстан по состоянию на 01.01.19 г. занимают площадь 81,5 тыс. га, 50% и 29% из которых приходится на молодняки 1 и 2-го класса возраста, 13% – на средневозрастные, 5% – на приспевающие, 3% – на спелые. Площадь лесных культур ели составляет около 70 тыс. га (86% от общей площади ельников). Большая их часть была создана за пределами естественного ареала в Закамье и Заволжье республики. Несмотря на то, что культуры ели создаются ежегодно на площади более 500 га, по итогам последнего лесоустройства 2011–2017 гг. площадь насаждений ели уменьшилась на 5 тыс. га. Практически во всех лесничествах лесостепной зоны Республики Татарстан доля площади погибших и находящихся в неудовлетворительном состоянии культур ели превышает 50% (52-71%). Основными причинами гибели культур являются заглушение мягколиственными породами и засуха 2010 г. Это является следствием создания лесных культур ели в лесостепной зоне под пологом леса или на вырубках мягколиственных пород. Количество подроста осины, липы мелколистной, березы повислой и клена остролистного на вырубках в первые годы может достигать 50 тыс. шт./га, ежегодный прирост 1,5 м. При отсутствии лесоводственных уходов высокой интенсивности к 5-10 годам лесные культуры оказываются под пологом мягколиственных пород и клена. В результате заглушения в 20-25 лет ель начинает усыхать и к 40 годам выпадает полностью из состава. При своевременном проведении уходов формируются смешанные насаждения с участием ели в составе от 3 до 8 единиц. Spruce plantations in the Republic of Tatarstan as of 01.01.19 occupy an are of 81.5 thousand hectares, 50% and 29% of them are young plantations of 1st and 2nd age classes, 13% are middle-aged, 5% are ripening, 3% are ripe. The area of spruce forest crops is about 70 thousand hectares (86% of total spruce plantations area). Most of them were created outside of the natural areas in Zakamye and Zavolzhye of the Republic of Tatarstan. Despite the fact that spruce crops are created annually on an area of more than 500 hectares, according to the results of the latest forest management in 2011–2017, the area of spruce plantations decreased by 5 thousand ha. The proportion of the area of dead and unsatisfactory spruce crops exceeds 50% (52–71%) in almost all forestries of the forest-steppe zone of the Republic of Tatarstan. Main reasons for the death of crops are drowning in soft-leaved breeds and the drought of 2010. This is a consequence of the creation of forest cultures of spruce in the foreststeppe zone under the forest canopy or on clearings of soft-leaved species. The volume of undergrowth of aspen, small-leaved linden, dwarf birch and holly maple in felling in the first years can reach 50 thousand units / ha, an annual growth is 1.5 m. In the absence of high intensity silvicultural nurseries, by 5-10 years forest crops became closed by canopy of softwood and maple. As a result of drowning at the age of 20-25, the spruce begins to dry out and by the age of 40 it completely drops out of the composition. With the timely conduct of forest management, mixed stands of spruce are formed with the participation in the composition from 3 to 8 units.