Betula Fruticosa Research Articles

Nutrient responses of vascular plants to N2-fixing tree Alnus hirsuta encroachment in a boreal peatland.

The N2-fixing trees Alnus spp. have been widely encroaching into boreal peatlands, but the nutrient responses of native vascular plants remain unclear. Here, we compared nutrient concentrations and isotope signal of six common plants (Betula fruticosa, Salix rosmarinifolia, Vaccinium uliginosum, Rhododendron tomentosum, Chamaedaphne calyculata, and Eriophorum vaginatum) between Alnus hirsuta island and open peatland and assessed plant nutrient responses to A. hirsuta encroachment in boreal peatlands. Alnus hirsuta encroachment increased nitrogen (N) concentration of leaf, branch, and stem. Despite no significant interspecific difference in branch and stem, the increment magnitude of leaf N concentration varied among species, with greatest magnitude for R. tomentosum (55.1% ± 40.7%) and lowest for E. vaginatum (9.80% ± 4.40%) and B. fruticosa (18.4% ± 10.7%). Except for E. vaginatum, the significant increase in δ15N occurred for all organs of shrubs, with interspecific differences in change of leaf δ15N. According to the mass balance equation involving leaf δ15N, R. tomentosum and E. vaginatum, respectively, obtained highest (40.5% ± 19.8%) and lowest proportions (-14.0% ± 30.5%) of N from A. hirsuta. Moreover, the increment magnitudes of leaf N concentration showed a positive linear relationship with the proportion of N from A. hirsuta. In addition, A. hirsuta encroachment reduced leaf phosphorus (P) concentration of deciduous shrubs (i.e., B. fruticosa, S. rosmarinifolia, and V. uliginosum), thus increasing N:P ratio. These findings indicate that Alnus encroachment improves native plant N status and selectively intensifies P limitation of native deciduous shrubs, and highlight that the N acquisition from the symbiotic N2-fixing system regulates plant N responses in boreal peatlands.

A native herbaceous community exerts a strong allelopathic effect on the woody range-expander Betula fruticosa

Abstract Biological invasions by alien and range-expanding native plant species can suppress native plants through allelopathy. However, the homeland security hypothesis suggests that some native plants can resist invasion by producing allelopathic compounds that inhibit the growth of invasive plants. Most research has focused on allelopathic interactions between individual native and invasive plant species, with less emphasis on how allelopathy helps entire native communities resist invasions. Additionally, limited knowledge exists about allelopathic interactions between range-expanding native species and recipient native communities, and their influence on invasion success. To bridge this knowledge gap, we conducted two greenhouse competition experiments to test reciprocal allelopathic effects between a native woody range-expanding species, Betula fruticosa, and a community of four native herbaceous species (Sanguisorba officinalis, Gentiana manshurica, Sium suave and Deyeuxia angustifolia) in China. We assessed whether B. fruticosa and the native community differed in their competitive effects and responses, and whether these were influenced by activated carbon, which neutralizes allelochemicals in the soil. Activated carbon reduced the suppressive effects of the native community on the above-ground biomass of B. fruticosa, which indicates that the native community exerted a strong allelopathic effect on B. fruticosa. In contrast, activated carbon only marginally enhanced the suppressive effects of B. fruticosa on the native community, which indicates that allelopathy is not the primary mechanism by which B. fruticosa exerts its suppression. Overall, these findings support the homeland security hypothesis and suggest that biotic resistance from the native herbaceous community may limit the invasion success of the woody range-expander B. fruticosa.

Temporal changes in mixing effects on litter decay and nitrogen release in a boreal riparian forest in northeastern China

In riparian forests, litter decay provides essential energy and nutrients for both terrestrial and fluvial ecosystems. Litter mixing effects (LMEs) are crucial in regulating litter decay and nutrient dynamics, yet how LMEs change over time is unclear in riparian forests. In this study, leaf litter of three common species (Alnus sibirica Fisch. ex Turcz, Betula platyphylla Sukaczev, and Betula fruticosa Pall.) were mixed in an equal mass ratio and LMEs were measured for mass and nitrogen (N) remaining in whole litter mixtures over a 3-year period in a boreal riparian forest, northeastern China. LMEs were also assessed for component litter mass and N remaining by separating litter mixtures by species. During the decay of litter mixtures, antagonistic effects on mass and N remaining were dominant after one and two years of decay, whereas only additive effects were observed after three years. LMEs correlated negatively with functional diversity after the first and two years of decay but disappeared after three years. When sorting litter mixtures by species, non-additive LMEs on mass and N remaining decreased over incubation time. Moreover, non-additive LMEs were more frequent for litter of both B. platyphylla and B. fruticosa with lower N concentration than for A. sibirica litter with higher N concentration. These results indicate that incubation time is a key determinant of litter mixing effects during decay and highlight that late-stage litter mixture decay may be predicted from single litter decay dynamics in boreal riparian forests.

Characteristics of Microbial Abundance in Rhizosphere and Non-Rhizosphere Soils of Permafrost Peatland, Northeast China

The rhizosphere microenvironment is crucial to plant–soil physiological processes. The differences among microbial communities in the rhizosphere and non-rhizosphere peatland topsoil (0–15 cm) and subsoil (15–30 cm) in five plant communities dominated by Carex schmidtii, Chamaedaphne calyculata, Ledum palustre, Betula fruticosa, and Vaccinium uliginosum, as well as non-rhizosphere soil in discontinuous and continuous permafrost regions, were studied. We found that the bacteria and nifH gene abundances in the C. calyculata rhizosphere soil in the discontinuous permafrost region were higher than those in continuous permafrost region, while the nirK and nifH gene abundances in the non-rhizosphere soil of the discontinuous permafrost region were lower than those in the continuous permafrost region. The ratio of bacteria to fungi decreased and that of nirK to nirS increased significantly from the discontinuous to the continuous permafrost region, indicating that permafrost degradation can change soil microbial community composition. Fungal abundance was higher in the rhizosphere than the non-rhizosphere soils, suggesting that plant roots provide a more suitable environment for fungi. Moreover, the abundances of the topsoil bacteria; the fungi; and the nirK, nirS, and nifH genes were higher than those in the subsoil because of the organic matter from plant litter as a source of nutrients. The microbial abundance in the subsoil was also more affected by nutrient availability. To sum up, the microbial abundance varied among the different types of rhizosphere and non-rhizosphere soils, and the carbon and nitrogen cycling processes mediated by soil microorganisms may be greatly altered due to permafrost degradation under climate warming.

Nitrogen addition mediates monospecific and mixed litter decomposition in a boreal peatland

Litter decomposition is a key determinant of soil organic matter accumulation in boreal peatlands. Climate warming and atmospheric nitrogen (N) deposition have recently increased N availability in boreal peatlands. However, how increased N availability alters decomposition dynamics of plant litter is uncertain in these ecosystems, especially for litter mixtures. Here, we collected fresh litter of four common species (Betula fruticosa, Ledum palustre, Eriophorum vaginatum, and Sphagnum palustre) in a poor fen of northeast China, and established an N addition (6 g N m−2 year−1) experiment to assess the effect of increased N availability on monospecific and mixed litter decomposition in the hummocks and hollows after one and three years of decomposition. In both hummocks and hollows, N addition increased mass loss of four monospecific litter after one year of decomposition but only accelerated litter decomposition of E. vaginatum and S. palustre with low litter quality after three years of decomposition. Moreover, N addition effects on monospecific litter decomposition were negatively related to monospecific litter decomposition in the absence of N addition. Irrespective of decomposition position, additive effects were more frequent than synergistic effects during decomposition of litter mixtures. In addition, N addition generally changed synergistic effects to additive effects after one and three years of decomposition, and such changing trends were stronger in hummocks than in hollows. These observations suggest that litter quality mediates N addition effects on monospecific litter decomposition, and highlight that increased N availability will alter mixed litter decomposition by reducing synergistic effects in boreal peatlands.

Driving Factors on Greenhouse Gas Emissions in Permafrost Region of Daxing'an Mountains, Northeast China

AbstractPermafrost regions are an important source of greenhouse gases. However, the effects of different permafrost wetland types on greenhouse gas emissions and the driving factors are still unclear in the permafrost region. Here, we selected three typical permafrost wetlands from the Daxing'an Mountains to investigate the effects of permafrost wetland types on greenhouse gas emissions. The cumulative N2O, CO2, and CH4 emissions were 84–122, 657,942–1,446,121, and 173–16,924 kg km−2, respectively. The linear mixed effects model indicated that N2O emissions were significantly affected by the NO3−‐N content, whereas CO2 emissions were mainly driven by soil temperature, water table level, and NO3−‐N content. CH4 emissions were affected by soil temperature and water table level. Permafrost wetland types significantly affected the average and cumulative N2O, CO2, and CH4 emissions. The cumulative N2O emissions were highest in the Larix gmelinii ‐ Carex appendiculata (LC) wetland and lowest in the Betula fruticosa Pall. (B) wetland, driven by NO3−‐N content. The cumulative CO2 emissions were highest in the B wetland and lowest in the L. gmelinii ‐ Ledum palustre var. dilatatum (LL) wetland. The cumulative CH4 emissions from B wetland were significantly higher than those from LL and LC wetlands. The differences in cumulative CO2 and CH4 emissions were driven by the water table level. Our findings indicate that NO3−‐N content affect the spatial‐temporal variation of N2O emissions, whereas water table level influence the spatial‐temporal variation of CO2 and CH4 emissions in the permafrost region of the Daxing'an Mountains.

Resource Remobilization Efficiency Varies With Plant Growth Form but Not Between Fens and Bogs

Resource resorption from senescing leaves is an important strategy for internal nutrient recycling in plants. However, our understanding of whether the responses of resource remobilization to mire types (fens vs. bogs) differ among various plant growth forms remains unclear. We thus assessed resource remobilization among various growth forms in fens and bogs in the Hani peatland in the Changbai Mountains, northeastern China. We analyzed and compared the concentrations of non-structural carbohydrates (NSCs), nitrogen (N), phosphorus (P), and potassium (K) in leaves and roots collected in August (mid-season) and September (end-season), and calculated the resource remobilization efficiency (RRE) of four species belonging to four growth forms grown in both fens and bogs. The deciduous dwarf trees (Betula fruticosa) and perennial grass (Phragmites australis) had relative higher leaf RRE than the moss (Sphagnum magellanicum). Although leaf nutrient RRE did not differ between fens and bogs, the deciduous dwarf trees had a higher leaf NSC RRE in bogs than in fens, and the moss NSC RRE was lower in bogs than in fens. Our results suggest that reallocation of mobile carbohydrates seems to be more sensitive to the growth condition than nutrients (N, P, and K) under nutrient-poor inhabits, which may be one of the reasons leading to nutrient limitation in peatlands.

CLUSTER COMPOSITION OF POLLEN PARTICLES OF ANEMOPHILIC PLANTS ENTERING ATMOSPHERE

A study is made on pollen emission into atmosphere of 21 species of anemophilous plants ( Betula divaricata Ledeb., Betula costata Trautv., Betula davurica Pall., Betula fruticosa Pall., Ulmus japonica (Rehd.)Sarg., Salix acutifolia Willd., Salix cinerea L., Salix purpurea L., Salix rosmarinifolia L., Alnus glutinosa (L.) Gaertn., Poa alpina L., Arrhenatherum elatius (L.) J. Presl & C. Presl, Briza maxima L., Deschampsia cespitosa (L.) P. Beauv., Urtica urens L., Carex altaica (Gorodkov) V.I. Krecz., Carex pallescens L., Carex flacca Schreb., Carex vesicaria L., Carex diluta M. Bieb., Plantago lanceolata L.), exposed by the Central Siberian Botanical Garden, SB RAS. These plants are widely spread over the territory of the Russian Federation and produce great amounts of allergenic pollen. The proportion of clusters of two or more pollen grains from the total number of pollen particles entering the atmosphere during the flowering periods of these plant species is estimated. It was shown that such clusters in significant quantities were formed in all series of experiments. At the same time, the proportion of pollen grains in their composition could reach 95% of the total number of pollen grains entering the atmosphere.

Differential responses of litter decomposition in the air and on the soil surface to shrub encroachment in a graminoid-dominated temperate wetland

Graminoid-dominated wetlands have been subjected to widespread shrub encroachment, yet the effect of this shift in species composition on litter decomposition remains unclear, especially in the standing-dead stage. We collected labile (Deyeuxia angustifolia) and recalcitrant (Carex schmidtii) graminoid leaf litter from a freshwater wetland in northeast China, and used the litterbag method to characterize litter ash-free dry mass (AFDM) loss and nitrogen (N) release in the air and on the soil surface in open wetlands and two shrub islands (Salix floderusii producing phenol-poor litter and Betula fruticosa producing phenol-rich litter) over 360 days of decomposition. Litter decomposition in the air and on the soil surface responded differentially to shrub expansion. In the air, AFDM loss and N release for both labile and recalcitrant litter were often lower in shrub islands than in open wetlands. On the soil surface, labile litter decomposition was decelerated in the presence of shrubs with phenol-rich litter, but accelerated in the presence of shrubs with phenol-poor litter. Despite the absence of significant differences in N release, recalcitrant litter AFDM loss was lower in shrub islands than in open wetlands after 360 days of decomposition on the soil surface. Shrub encroachment retards litter decomposition in the air, but the effects on litter decomposition on the soil surface vary with shrub type and litter degradability in graminoid-dominated wetlands. Moreover, these findings emphasize that standing litter decomposition should be considered to enhance our understanding of shrub encroachment effects on litter decomposition in these wetlands.

Functional identity and functional diversity co-regulate litter mixture decomposition and nitrogen release in boreal riparian forest ponds

The relationship between biodiversity and litter decomposition has received considerable attention, but the complex biodiversity effects on decomposition and the underlying mechanisms are still unclear, especially in boreal riparian forest ponds. Here, we collected leaf litter from an N2-fixing species (Alnus sibirica) and two non-N2-fixing species (Betula platyphylla and Betula fruticosa) in a boreal riparian forest, northeast China. Then, we mixed leaf litter with varying composition and evenness to create a large gradient of litter functional identity and functional diversity, and used the litterbag method to examine the effect of altering plant composition on litter mass loss and nitrogen (N) release during 2 years of decomposition in forest ponds. Over 2 years of decomposition, the presence of A. sibirica in litter assemblages accelerated mass loss and N release by improving functional identity and increasing functional diversity of litter mixtures. Irrespective of the dominant species, litter mass loss generally increased with rising evenness, whereas the effect of species evenness on N release was dependent on the dominant species. When all litter mixtures were pooled, litter mixing effects on mass loss and N release correlated positively with litter functional diversity. Moreover, the decomposition dynamics of litter mixtures were regulated by litter functional diversity and the resulting mixing effects, as well as the community-weighted mean traits such as N and lignin concentrations. These findings confirm the importance of litter functional identity and functional diversity in driving decomposition processes of litter mixtures, and also indicate that increased abundance of N2-fixing species will accelerate litter decomposition and enhance N release in boreal riparian forest ponds.

Effect of expanded shrub litter on decomposition of graminoid litter in a temperate freshwater marsh

Shrub encroachment can alter litter decomposition in temperate graminoid-dominated wetlands, yet its influence on the direction of litter mixing effects is still elusive. We collected senesced aboveground tissues of two graminoid species (Deyeuxia angustifolia and Carex schmidtii) and leaf litter of two shrub species (Betula fruticosa and Salix floderusii) in a freshwater marsh of Northeast China, and measured litter mass loss dynamics in monocultures and shrub-graminoid mixtures (in mass ratios of 1:2 and 2:1) using a 730-day incubation experiment. In the monocultures, shrub litter had greater mass loss than graminoid litter presumably due to the relatively higher N, and dissolved organic C and N concentrations. Additive effects were observed in all shrub-graminoid mixtures after 182 days of decomposition, while nonadditive effects gradually became more prominent as litter decomposition proceeded. Salix floderusii leaves usually promoted decomposition of neighboring graminoid litter, especially when S. floderusii dominated, leading to a synergistic effect on mass loss of the whole litter mixtures. However, the effects of B. fruticosa on decomposition of graminoid litter varied with incubation time, species composition and species proportion. At the end of incubation, synergistic effects were observed in B. fruticosa-D. angustifolia mixtures, while additive effects occurred in B. fruticosa-C. schmidtii mixtures. The effects of shrub expansion on the direction of litter mixing effects are dependent on incubation time, shrub species and dominant graminoid types in this freshwater marsh. These findings help to predict the consequence of altered species composition on community-level litter decomposition in temperate graminoid-dominated wetlands.

Effect of woody plant expansion on decomposition of fine root mixtures in a grass-dominated temperate wetland

Little is known about the effect of woody plant expansion on decomposition of root mixtures in grass-dominant temperate wetlands. Here, we collected fine roots (< 1 mm) of Deyeuxia angustifolia (grass) and Betula fruticosa (shrub) from a freshwater wetland in the Sanjiang Plain, Northeast China, and decomposition rates of their monocultures and mixtures (with 2:1 and 1:2 mass ratios) were determined by measuring carbon (C) mineralization and mass loss with a 365 days incubation experiment. Meanwhile, litter mixing effects were assessed by the differences in observed decomposition rates of root mixtures and predicted values based on the performance of component species decomposing alone. Betula fruticosa fine roots had higher N, total polyphenol, and condensed tannin concentrations than D. angustifolia fine roots. By the end of incubation, B. fruticosa fine roots generally had greater C mineralization rate and mass loss than the other three root treatments. Notably, both C mineralization rate and mass loss were lower than the expected values in the B. fruticosa-dominant mixture, whereas there were no significant differences between observed and expected values in the D. angustifolia-dominant mixture. Our findings imply that the increase in woody plant abundance will exert influences on fine root decomposition rates through altered substrate quality and litter mixing effects in grass-dominated temperate wetlands.

The Early Khvalynian stage in the Caspian Sea evolution: Pollen records, palynofloras and reconstructions of paleoenvironments

In addressing the controversial issues of the Late Pleistocene paleogeography of the Caspian basin, an important role is given to the results of the spore-pollen analysis and based on them reconstructions of climate and vegetation changes in the Northern Caspian region during the development of the Early Khvalynian transgression. In this paper we present the main results of the palynological study of deposits (chocolate clays and the overlying and underlying layers from the Srednyaya Akhtuba section) of maximum stage of the Early Khvalynian transgression; the materials are illustrated by pollen diagram with the data of spore-pollen analysis and the detailed list of palynoflora recovered from the studied Lower Khvalynian sequences, and complemented with photographs of pollen belonging to the principal autochtonous taxa and, for comparison, to some redeposited palynomorphs. Palynological materials indicate subaqual (brackish marine and freshwater) sedimentation of the sediments studied in periglacial landscapes and, for the most part, under very harsh climatic conditions. The performed climate-stratigraphic reconstructions do not contradict the data of absolute dating on the accumulation of the studied deposits during the Late Valdai (Ostashkov) late Glacial period. During this interval in the territory of the study area, plant communities of the glacial climate — tundra-steppe, periglacial forest-steppe, periglacial steppe, periglacial parklands and periglacial forests — were developed. The widespread occurrence in the composition of the periglacial vegetation cover of the studied region of the yernik formations from Betula nana and shrub communities from Betula fruticosa, B. nana, Alnaster fruticosus, Juniperus, etc. testifies to the severe climatic conditions and, possibly, the existence of sporadic permafrost in the cold stages (stadials) of the Ostashkov Late Glacial period.

Ecological indicators of near-surface permafrost habitat at the southern margin of the boreal forest in China

Abstract The most dramatic permafrost degradation is expected to occur at the southern edge of permafrost distribution, which is difficult to detect directly on a large scale. Ecological indicators can be used to provide an early signal of changes in terrestrial ecosystems for regional near-surface permafrost habitats and potentially to monitor near-surface permafrost degradation. In this study, plant composition and community structure indicate the near-surface permafrost distribution at the southern edge of the boreal forest and permafrost in northeastern China. The plant species composition and structure of aboveground vegetation were linked to the belowground near-surface permafrost distribution in order to find indicators of changes in vegetation features from permafrost melting. These indicators are essential for assessing changes in permafrost vegetation systems under climate change. Carex schmidtii and C. appendiculata in the herb layer and Betula fruticosa in the shrub layer were found to be specific near-surface permafrost plant indicator species, especially for the wetland permafrost. Shrub cover, moss mat thickness and tree canopy cover are also strongly correlated with near-surface permafrost distribution. The active layer thickness (ALT) showed negative correlations with moss thickness and shrub cover because these features may act as buffers for regional climate warming. We chose the cover of each indicator species, near-surface permafrost-specific community features and geographical information as independent variables to predict the possible distribution of near-surface permafrost in our study region using logistic regression. The results showed that the prediction model had good performance and accuracy. Our study sheds light on early caution of deepening of regional-scale permafrost active layer with vegetation indicators that can further be identified from satellite images.

Effects of litter mixtures on aerobic decomposition rate and its temperature sensitivity in a boreal peatland

Litter mixing effects during decomposition remain inconclusive for boreal peatlands, and such effects may vary with climate warming and associated shifts in vegetation composition. Here, litters were collected from four common species (deciduous shrub Betula fruticosa, evergreen shrub Ledum palustre, graminoid Eriophorum vaginatum, and moss Sphagnum divinum) in a boreal peatland of northeast China, resulting in 15 species combinations with species richness ranging from one to four. We determined litter mixing effects on carbon (C) mineralization rate and mass loss under aerobic conditions at 10 °C and 20 °C in a 315-d incubation experiment, and assessed the differences in litter mass loss for the individual species within monocultures and mixtures. Non-additive effects on C mineralization and mass loss were prevalent during decomposition of litter mixtures. Moreover, the sensitivity of C mineralization and mass loss to rising incubation temperature (Q10) was found to be non-additive in five and three out of 11 mixtures, respectively. Notably, mass loss of other litters in the mixtures was generally promoted by B. fruticosa, but inhibited by S. divinum in two- and three-species litter mixtures. Furthermore, B. fruticosa increased and S. divinum decreased Q10 values for mass loss of other litters in four out of seven cases. These findings suggest that the shifts in plant community composition will not only influence community-level litter decomposition through altered litter mixing effects during decomposition, but also modulate the response of litter decomposition to rising temperature in boreal peatlands.

Флористические находки адвентивных и аборигенных видов в Новосибирской области

New locations of some adventive and rare native plant species in Novosibirskaya oblast are reported. The adventive species Tanacetum balsamita L. was found in Siberia for the first time. The new plant species for Novo­sibirskaya oblast are adventive ones: Alcea rosea L., Antirrhinum majus L., Miscanthus sinensis Anderss., Galinsoga ciliata (Rafin.) Blake and aboriginal ones: Plantago uliginosa F. W. Schmidt. The new locations of rare adventive species – Aster novi-belgii L., Eragrostis minor Host, Papaver dubium L. – and rare native species – Betula fruticosa Pall., Hypericum ascyron L., Inula helenium L., Myosotis krylovii Serg., Spiraea salicifolia L. were found.

Dynamics of Vegetation of the Islands of Peter the Great Bay

Paleopalynological researches of modern sedimentary deposits allowed discovering specifics and tendencies of the development of vegetation cover on the islands of Peter the Great Bay in Holocene under climatic fluctuations and the related with them variations of the sea level as well as under the impact of a human factor. In cold Holocene periods small-leaved-broadleaved forests with Betula fruticosa were widespread. During warm periods broadleaved forests predominated. In the second half of Late Holocene the development of coniferous-broadleaved forests occurred. The climate was colder than the present one. Vegetation of modern islands consists of broadleaved and sparse broadleaved forests which appeared under the impact of the anthropogenic factor. It is also noted that the areas occupied with meadow and shrubby communities are spreading. The comparative analysis of the islands by the similarity of the stages of paleovegetation development allows identifying regularities and factors of the development of vegetation cover.

Zonation of plant cover and environmental factors in wetlands of the Sanjiang Plain, northeast China

The zonation of depressional and riparian wetlands in the Sanjiang Plain of northeastern China was studied to describe their vegetation composition and environmental variables. We sampled 108 plots in 6 depression and riparian wetlands. Samples were classified into 4 groups using two‐way indicator species analysis (TWINSPAN). Emergent marsh vegetation was characterized by Carex lasiocarpa and C. pseudocuraica, meadow marsh vegetation by tussock species such as Carex appendiculata and C. meyeriana, wet meadow vegetation by Calamangrostis angustifolia and Carex appendiculata, and shrub meadow vegetation by the shrubs Betula fruticosa, Alnus sibirica and Salix rosmarinifolia and the graminids Carex schmidtii and Calamagrostis angustifolia. CCA ordination showed that water table, organic matter and available N were the major factors explaining the vegetation zonation pattern. Compared with other Northern Hemisphere regions, bog and fen vegetation are completely absent due to climatic conditions unfavorable for peat formation. Out of four vegetation types, only the Carex lasiocarpa community and the C. pseudo‐curaica community have been found in other regions. However, at the species level many species are widespread and some species are vicariant or pseudovicariant to other regions in the world. Our study suggests that topography and hydrology may be the most important determinants of the vegetation pattern in this region.

Influencing factors on early vegetation restoration in burned area of Pinus pumila – Larch forest

Pinus pumila (Dall.) Regel, a rare conifer and key species in high latitude and high altitude mountains, has an important role in soil and water conservation. This evergreen shrub grows 3–6m high in P. pumila – larch (Larix gmelini) open forest at altitudes of 800–1200m in the Greater Kingan Mountain Range (Daxing’an Mountain). Forest fires are major natural hazards to P. pumila – larch forest. The unique ecological role of this community gives important theoretical and practical significance to research on P. pumila – larch forest restoration after fires. Literature concerning factors influencing early vegetation restoration in burned areas in this habitat is sparse. We studied these factors, especially those related to P. pumila seedling establishment. The results showed fires in P. pumila – larch forest usually resulted in severe burns. Typically almost no P. pumila survived after fires. Nearly all ground fuels were consumed. Second growth after fires exhibited low species richness. The dominant tree/shrub seedlings found after fires were birch (Betula platyphylla) and larch, with small number of P. pumila. Other shrub seedlings found were Ledum palustre, Vaccinium vitis-idaea, Betula fruticosa, and Rubus arcticus. The main herb species found were Deyeuxia langsdorffii, and Chamaenerion angustifolium. Important factors influencing early vegetation restoration after fires included seed dispersal, fire size, and site condition. Seed dispersal in birch and larch is higher than in P. pumila; more seedlings of birch and larch were found in burned areas than seedlings of P. pumila. Most seeds germinated in the first year following a fire. The extent of the burned area influences seedling distribution patterns, especially in species with limited seed dispersal ability. Birch and larch seedlings were evenly distributed in the entire burned area, while seedlings of P. pumila were found only at the fire edge. No P. pumila seedlings were found more than 50m away from seed source trees. Site condition significantly influenced seed germination and growth in birch and larch; these seedlings only grew well in burned areas with good site conditions (shallow slopes, thick soils, etc.). They did not grow well in burned areas with poor site conditions (steep slopes, thin soils, etc.). However, P. pumila seedlings could grow well in burned areas with either good or poor site conditions. The strong vitality of P. pumila seedlings gives this species an enormous ecological advantage in soil conservation and environmental restoration and conservation. We conclude that the main factor influencing seedling establishment in P. pumila is its weak seed dispersal ability. Although the P. pumila seeds can germinate in all burned areas, natural regeneration rarely restores burned areas to the original P. pumila – larch forest. Planting seeds and/or seedlings may facilitate burned area restoration to P. pumila – larch forest. Because P. pumila seedlings grow very slowly, the restoration process may take decades.

Paleontological records indicate the occurrence of open woodlands in a dry inland climate at the present-day Arctic coast in western Beringia during the Last Interglacial

Permafrost records, accessible at outcrops along the coast of Oyogos Yar at the Dmitry Laptev Strait, NE-Siberia, provide unique insights into the environmental history of Western Beringia during the Last Interglacial. The remains of terrestrial and freshwater organisms, including plants, coleopterans, chironomids, cladocerans, ostracods and molluscs, have been preserved in the frozen deposits of a shallow paleo-lake and indicate a boreal climate at the present-day arctic mainland coast during the Last Interglacial. Terrestrial beetle and plant remains suggest the former existence of open forest-tundra with larch ( Larix dahurica), tree alder ( Alnus incana), birch and alder shrubs ( Duschekia fruticosa, Betula fruticosa, Betula divaricata, Betula nana), interspersed with patches of steppe and meadows. Consequently, the tree line was shifted to at least 270 km north of its current position. Aquatic organisms, such as chironomids, cladocerans, ostracods, molluscs and hydrophytes, indicate the formation of a shallow lake as the result of thermokarst processes. Steppe plants and beetles suggest low net precipitation. Littoral pioneer plants and chironomids indicate intense lake level fluctuations due to high evaporation. Many of the organisms are thermophilous, indicating a mean air temperature of the warmest month that was greater than 13 °C, which is above the minimum requirements for tree growth. These temperatures are in contrast to the modern values of less than 4 °C in the study area. The terrestrial and freshwater organism remains were found at a coastal exposure that was only 3.5 m above sea level and in a position where they should have been under sea during the Last Interglacial when the global sea level was 6–10 m higher than the current levels. The results suggest that during the last warm stage, the site was inland, and its modern coastal situation is the result of tectonic subsidence.