Alpine Herb Research Articles

Variation in adaptation mechanisms of medicinal herbs to the extreme winter conditions across the North Western Himalaya

The North Western Himalaya region is characterized by extreme seasonal variability and local changes in microclimate. Plants adapted to this region demonstrate marked variability to the extreme winter conditions. This region, designated as a biodiversity hotspot, is rich in medicinal herbs, which exhibit diverse growth and adaptation mechanisms to the harsh environment. In the present study, physiological mechanisms of adaptation to the winter season conditions were compared in five medicinal herbs. Components of the photosynthetic machinery, and osmoregulation which are of importance for secondary metabolism is not well known in these alpine herbs and was studied. The medicinal herbsRumex dentatus,Atropa accuminata,Lupinus polyphyllus,Hyoscyamus niger, andLavandula officinaliswere collected before snowfall in September–November to evaluate variability in metabolic and physiological responses to the varied seasonal regimes. Plants were followed over a period of 8 weeks (summer to early winter) in three sites which vary in altitude and thereby climatic conditions: Site I, 4175 m (Pahalgam); Site II, 3748 m (Duksum Sinthan Top); and Site III, 4100 m (Mount Apharwat). Variations in photosynthetic capacity and components of the photosynthetic machinery, a range of antioxidants, antioxidant enzymes and total non-structural carbohydrates (TNC) were studied to test their involvement in adaptation schemes and secondary metabolism under the harsh winter conditions. The results demonstrate a range of adaptations to the freezing stress conditions including high photon energy use efficiency; an increase in the proportion of Chlb, carotenoid content; specific activity of the antioxidant enzymes superoxide dismutase, catalase, glutathione reductase, ascorbate peroxidase activity, and TNCs.

SOIL MICROMYCETES AND VEGETATION CHANGES ASSOCIATED WITH VEGETATIVE COVER DESTRUCTION ON CHOSEN LOCALITIES OF TATRY MOUNTAINS - FIRST APPROACH

AbstractĎugova O., Barančokova M., Krajči J., Barančok P.: Soil micromycetes and vegetation changes associated with vegetative cover destruction on chosen localities of Tatry Mountains - first approach. Ekologia (Bratislava), Vol. 32, No. 2, p. 158-172, 2013.Species composition of soil micromycetes and vegetation and its changes associated with vegetative cover destruction were observed in four localities of Tatry Mts. Three research plots with different extent of vegetation destruction on each locality were subjectively chosen: control plots with almost no destruction of vegetation and soil cover (C), partially disturbed plots (B) and plots with high level of soil cover destruction where cover of herb layer was less than 20% (A). Plant species composition of control plots was characterised by the highest level of taxonomical diversity, highest cover of herb and moss layer and represented by alpine herb and grass communities on siliceous bedrock (Juncion trifidi alliance) and alpine and subalpine plant communities on calcareous bedrock (Seslerion tatrae alliance). Devastation of soil and vegetation on B and A plots was performed particularly by decreasing of herb layer cover and changes in species composition: species as Vaccinium myrtillus, Vaccinium vitis-idaea and Calluna vulgaris were absent, whereas Poa alpina, Potentilla aurea, Agrostis rupestris or Avenella flexuosa occurred on devastated plots often. From investigated soils 43 species of soil micromycetes were identified. Control plot of each locality was represented by the highest taxonomical diversity of soil micromycetes. The number of species significantly decreased on plots with successive destruction of vegetation cover (B and A). Several species were identified in just one case (Penicillium digitatum (pers.:Fr.) Sacc., Chrysosporium keratinophilum D.Frey ex J.W. Carmich. etc.). The outcomes showed that soil microorganisms as well as vascular plants react on destruction of soil cover very sensitively.

Erratum to: Unexpectedly high outcrossing rate in both dense and sparse patches in self-compatible Pedicularis rex (Orobanchaceae)

Pedicularis rex, a self-compatible alpine herb, depends exclusively on pollinators for reproduction. Previous study has revealed that 74.7 % of genetic variability occurs among populations in Yunnan, indicating a mixed mating system for the species. The large floral display also indicates high potential geitonogamy. Therefore, plant density and display size may be important factors influencing the realized mating system of P. rex. In the study reported here we explored the effects of plant density and floral display size on pollinator movements and thus outcrossing rate in two patches of in P. rex at low and high plant densities. We examined foraging behavior of bumblebees, measured reproductive outputs under hand and natural pollination, and estimated the outcrossing rates using RAPD markers. Floral display size was significantly larger and bumblebees visited significantly more flowers in sequence on individual plants in the sparse patch than in the dense patch. We found a significant positive correlation between floral display size and successive visits in the sparse patch, but not in the dense patch. Regression analysis revealed a significant inverse correlation between fruit production and flower production per plant with a theoretical maximum of 63 fruits per plant, but no relationship between seed production and flower production per plant. Contrary to previous studies on genetic structure, however, we found an unexpectedly high outcrossing rate in both the sparse and the dense patch (tm = 1.151 and 0.924, respectively). Resource limitation may intensify seed competition and result in selected seed abortion, which may largely explain the unexpectedly high outcrossing rate.

Identifying genetic signatures of selection in a non-model species, alpine gentian (Gentiana nivalis L.), using a landscape genetic approach

It is generally accepted that most plant populations are locally adapted. Yet, understanding how environmental forces give rise to adaptive genetic variation is a challenge in conservation genetics and crucial to the preservation of species under rapidly changing climatic conditions. Environmental variation, phylogeographic history, and population demographic processes all contribute to spatially structured genetic variation, however few current models attempt to separate these confounding effects. To illustrate the benefits of using a spatially-explicit model for identifying potentially adaptive loci, we compared outlier locus detection methods with a recently-developed landscape genetic approach. We analyzed 157 loci from samples of the alpine herb Gentiana nivalis collected across the European Alps. Principle coordinates of neighbor matrices (PCNM), eigenvectors that quantify multi-scale spatial variation present in a data set, were incorporated into a landscape genetic approach relating AFLP frequencies with 23 environmental variables. Four major findings emerged. 1) Fifteen loci were significantly correlated with at least one predictor variable (R adj 2 > 0.5). 2) Models including PCNM variables identified eight more potentially adaptive loci than models run without spatial variables. 3) When compared to outlier detection methods, the landscape genetic approach detected four of the same loci plus 11 additional loci. 4) Temperature, precipitation, and solar radiation were the three major environmental factors driving potentially adaptive genetic variation in G. nivalis. Techniques presented in this paper offer an efficient method for identifying potentially adaptive genetic variation and associated environmental forces of selection, providing an important step forward for the conservation of non-model species under global change.

The relative importance of solitary bees and syrphid flies as pollinators of two outcrossing plant species in the New Zealand alpine

AbstractPollinators vary in their relative contribution to the conspecific pollen deposited onto receptive stigmas, because of variation in both visitation rate and effectiveness of pollen transfer. Syrphid flies and short‐tongued solitary bees are common flower visitors in alpine New Zealand, yet their relative importance as pollinators is unknown. We measured pollinator performance of the New Zealand alpine endemics Hylaeus matamoko (Hymenoptera: Colletidae) and Allograpta spp. (Diptera: Syrphidae) on two New Zealand alpine herbs, Ourisia glandulosa (Plantaginaceae) and Wahlenbergia albomarginata (Campanulaceae). Ourisia glandulosa received visits by solitary bees and syrphid flies at equal frequencies, whereas W. albomarginata was mostly visited by H. matamoko. Based on single‐visit pollen deposition to virgin stigmas, H. matamoko was a much more effective pollinator than Allograpta spp., delivering 10 times as much pollen per visit to O. glandulosa stigmas and 3 times as much to W. albomarginata stigmas. By multiplying visitation frequency by single‐visit pollen deposition, we estimated that H. matamoko performed 90% and 95% of the pollination of O. glandulosa and W. albomarginata, respectively. Although H. matamoko bees are short‐tongued and small in size, they are critically important to plant reproductive success in the New Zealand alpine. These bees contributed most of the pollination, even to a species that received just as many visits by flies, underscoring the need to consider per‐visit effectiveness as well as visitation rate in assessing the importance of different pollinators.

Anyone for an aperitif? Yes, but only a Braulio DOC with its certified proteome

The trace proteome of a Braulio aperitif (a 21% alcohol beverage, named after a mountain in the Val di Stelvio, Italy) has been investigated via capture with combinatorial peptide ligand libraries (CPLL, ProteoMiner). This aperitif is made with an infusion of 13 mountain herbs and berries, among which four are officially indicated in the label: Achillea moschata, juniper (Juniperus communis subsp. alpina) berries, absinthe (Artemisia absinthium) and gentian (Gentiana alpina) roots. Via capture with CPLLs at pH 7.0 and 2.2 we were able to identify 29 unique gene products, among which the PR5 (parasite resistance) allergen Jun r 3.2, a 25kDa species from Juniperus rigida. Due to the paucity of data on these alpine herbs, it was difficult to attribute these proteins to the specific plant extracts presumably present in this beverage; however most of the species identified indeed belong to alpine herbs and plants, living in a habitat between 1000 and 2000m of elevation. Most of them are enzymes, spanning a Mr range from 10 to 65kDa. It is hoped that such a proteomic signature should help tracking counterfeited products sold on the market.

Where have all the blue flowers gone: pollinator responses and selection on flower colour in New ZealandWahlenbergia albomarginata

Although pollinators are thought to select on flower colour, few studies have experimentally decoupled effects of colour from correlated traits on pollinator visitation and pollen transfer. We combined selection analysis and phenotypic manipulations to measure the effect of petal colour on visitation and pollen export at two spatial scales in Wahlenbergia albomarginata. This species is representative of many New Zealand alpine herbs that have secondarily evolved white or pale flowers. The major pollinators, solitary bees, exerted phenotypic selection on flower size but not colour, quantified by bee vision. When presented with manipulated flowers, bees visited flowers painted blue to resemble a congener over white flowers in large, but not small, experimental arrays. Pollen export was higher for blue flowers in large arrays. Pollinator preference does not explain the pale colouration of W.albomarginata, as commonly hypothesized. Absence of bright blue could be driven instead by indirect selection of correlated characters.

Relationships between Flowering Phenology and Functional Traits in Eastern Tibet Alpine Meadow

Flowering phenology is a key life history trait that strongly influences reproductive success. We investigated the relationship between flowering phenology and functional traits of 48 alpine herb species using the Leaf-Height-Seed (LHS) scheme developed by Westoby (1998) to quantify the ecological strategy of the plant species. Phenological data were obtained by weekly observation of fifty 0.5 × 0.5 m2 quadrates. Specific leaf area (SLA), height, and seed size of 48 alpine herbs were measured. Comparative generalized estimating equations and generalized linear models suggested that flowering peak date was positively correlated with size of maternal plant (biomass and height) and negatively correlated with seed size. Species with a longer flowering period were smaller and produced bigger seeds than those with a short flowering season. Flowering peak date and duration were negatively correlated, although this correlation was mainly present in annuals, which are relatively rare in the alpine meadow. Relationships between flowering phenology and specific leaf area (SLA) were weak. There were only weak effects of phylogeny on the relationships between flowering phenology and functional traits. Wind-pollinated species flowered earlier than insect-pollinated species. Annuals flowered longer than perennials. Relationships between flowering phenology and functional traits indicate that there is a tradeoff between maternal and reproductive growth, and flowering time may underlie the correlation between plant height and seed size.

New distributional record of Gentiana tetrasepala Biswas (Gentianales: Gentianaceae) from the Valley of Flowers National Park, Garhwal Himalaya

A threatened endemic Himalayan herb discovered from the Valley of Flowers National Park (VoFNP). Gentiana tetrasepala Biswas belonging to the family Gentianaceae was rediscovered by Rawat (2009) after a long gap of 123 years from Garhwal Himalaya. In our investigation of the climatic and glacial variation within VoFNP, Gentiana tetrasepala Biswas was recorded for the first time. The Valley of Flowers, a world Heritage site situated in the alpine meadows of District Chamoli in the state Uttarakhand. Recording of G. tetrasepala Biswas an alpine herb from VoFNP is good indication although, due to recent climatic and glacial variation the habitat of the species might be replace cause overlapping and vegetational adjustment in the form of upward shifting. In the present communication the manuscript deals G. tetrasepala conservation and probability of being disappearance along with valid taxonomical description for future reference, which will be useful to the botanist and environmentalist.

Genetic diversity and population structure of Swertia tetraptera (Gentianaceae), an endemic species of Qinghai-Tibetan Plateau

Swertia tetraptera maxim is an annual alpine herb endemic to the qinghai-tibetan plateau (qtp). its populations are locally scattered as isolated patches throughout this region. genetic variation within and among thirty-four populations of this species was assessed using issr fingerprinting with 10 primers. high levels of genetic diversity exist within species (p = 98.9%, i = 0.3475; he = 0.2227), while the within-population diversity is low (p = 32.7%, i = 0.177; he = 0.12). high levels of genetic differentiation were detected among populations based on various statistics, including nei's genetic diversity analysis (g(st) = 0.4608), bayesian analysis (theta(b) = 0.476) and amova (f(st) = 0.57). that is, populations shared low levels of genetic identity (i = 0.2622-0.0966). this genetic structure was probably due to severe genetic drift, breeding system and limited gene flow. the observed genetic structure of the populations implies that different populations across the distribution range of the species should be sampled to maintain high genetic diversity when a conservation strategy is implemented. (c) 2011 elsevier ltd. all rights reserved.

The importance of Anatolian mountains as the cradle of global diversity in Arabis alpina, a key arctic–alpine species

Anatolia is a biologically diverse, but phylogeographically under-explored region. It is described as either a centre of origin and long-term Pleistocene refugium, or as a centre for genetic amalgamation, fed from distinct neighbouring refugia. These contrasting hypotheses are tested through a global phylogeographic analysis of the arctic-alpine herb, Arabis alpina. Herbarium and field collections were used to sample comprehensively the entire global range, with special focus on Anatolia and Levant. Sequence variation in the chloroplast DNA trnL-trnF region was examined in 483 accessions. A haplotype genealogy was constructed and phylogeographic methods, demographic analysis and divergence time estimations were used to identify the centres of diversity and to infer colonization history. Fifty-seven haplotypes were recovered, belonging to three haplogroups with non-overlapping distributions in (1) North America/Europe/northern Africa, (2) the Caucuses/Iranian Plateau/Arabian Peninsula and (3) Ethiopia-eastern Africa. All haplogroups occur within Anatolia, and all intermediate haplotypes linking the three haplogroups are endemic to central Anatolia and Levant, where haplotypic and nucleotide diversities exceeded all other regions. The local pattern of haplotype distribution strongly resembles the global pattern, and the haplotypes began to diverge approx. 2·7 Mya, coinciding with the climate cooling of the early Middle Pleistocene. The phylogeographic structure of Arabis alpina is consistent with Anatolia being the cradle of origin for global genetic diversification. The highly structured landscape in combination with the Pleistocene climate fluctuations has created a network of mountain refugia and the accumulation of spatially arranged genotypes. This local Pleistocene population history has subsequently left a genetic imprint at the global scale, through four range expansions from the Anatolian diversity centre into Europe, the Near East, Arabia and Africa. Hence this study also illustrates the importance of sampling and scaling effects when translating global from local diversity patterns during phylogeographic analyses.

The effect of flower position on variation and covariation in floral traits in a wild hermaphrodite plant.

BackgroundFloral traits within plants can vary with flower position or flowering time. Within an inflorescence, sexual allocation of early produced basal flowers is often female-biased while later produced distal flowers are male-biased. Such temporal adjustment of floral resource has been considered one of the potential advantages of modularity (regarding a flower as a module) in hermaphrodites. However, flowers are under constraints of independent evolution of a given trait. To understand flower diversification within inflorescences, here we examine variation and covariation in floral traits within racemes at the individual and the maternal family level respectively in an alpine herb Aconitum gymnandrum (Ranunculaceae).ResultsWe found that floral traits varied significantly with flower position and among families, and position effects were family-specific. Most of the variance of floral traits was among individuals rather than among flowers within individuals or among families. Significant phenotypic correlations between traits were not affected by position, indicating trait integration under shared developmental regulation. In contrast, positive family-mean correlations in floral traits declined gradually from basal to distal flowers (nine significant correlations among floral traits in basal flowers and only three in distal flowers), showing position-specificity. Therefore, the pattern and magnitude of genetic correlations decreased with flower position.ConclusionsThis finding on covariation pattern in floral reproductive structures within racemes has not been revealed before, providing insights into temporal variation and position effects in floral traits within plants and the potential advantages of modularity in hermaphrodites.

Divergent selection in trailing- versus leading-edge populations of Biscutella laevigata

Knowledge on how climate-induced range shifts might affect natural selection is crucial to understand the evolution of species ranges. Using historical demographic perspectives gathered from regional-scale phylogeography on the alpine herb Biscutella laevigata, indirect inferences on gene flow and signature of selection based on AFLP genotyping were compared between local populations persisting at the trailing edge and expanding at the leading edge. Spatial autocorrelation revealed that gene flow was two times more restricted at the trailing edge and genome scans indicated divergent selection in this persisting population. In contrast, no pattern of selection emerged in the expanding population at the leading edge. Historical effects may determine different architecture of genetic variation and selective patterns within local populations, what is arguably important to understand evolutionary processes acting across the species ranges.

Morphological and genetic variations of Potentilla matsumurae (Rosaceae) between fellfield and snowbed populations

Identifying ecological factors associated with local differentiation of populations is important for understanding microevolutionary processes. Alpine environments offer a unique opportunity to investigate the effects of habitat-specific selective forces and gene flow limitations among populations at a microscale on local adaptation because the heterogeneous snowmelt patterns in alpine ecosystems provide steep environmental changes. We investigated the variation in morphological traits and enzyme loci between fellfield and snowbed populations of Potentilla matsumurae, a common alpine herb with a wide distribution along snowmelt gradients in northern Japan. We found significant differences in morphological traits between fellfield and snowbed habitats in a northern distribution region. These differences were maintained when plants were grown under uniform conditions in a greenhouse. Allozyme variations among 15 populations from geographically separated regions with different historical backgrounds showed that the populations are more genetically differentiated between the fellfield and snowbed habitats within a region than between populations occupying the same habitat type in different regions. These results suggest that variation in snowmelt regimes could be a driving force creating local adaptation and genetic differentiation of alpine plant populations.

Costs of reproduction in circumpolar Parnassia palustris L. in light of global warming

Life-history theories predict competition and compromises between different reproductive and somatic (e.g., growth) functions in plants. This study concerns the costs of reproduction in an alpine herb, Parnassia palustris L., in light of global warming. The field experiments involved manipulations of temperature regime using open top chambers, and manipulations of the current level of reproductive investment by supplemental hand-pollination (SP) and bud removal (BR). The study continued for 2 years and costs of reproduction were evaluated in the second year by comparing reproductive outputs and growth between treatment groups. Flower manipulations carried out the first year had no statistically significant effect on reproductive or somatic variables in the second year, which suggests that reproductive costs in P. palustris are limited. Increased temperature, however, had a positive effect on a range of reproductive traits such as seed number, seed mass per fruit, mass per seed, and ratios between reproductive outputs and growth, but had no statistically significant influence on growth. No statistically significant interaction effects between flower manipulation and warming were revealed, which implies that the effects of flower manipulation in the first year does not differ statistically significantly between the two temperature regimes in the next year. We conclude that the lack of reproductive costs found in P. palustris at Finse expresses that resources are not restricted under a level that will induce high costs of reproduction. Furthermore, higher temperatures do not affect the costs, and finally, it appears that the reproductive costs are fine-tune controlled, which implies optimizing rather than maximizing of reproductive and somatic outputs.

Extensive population expansion of Pedicularis longiflora (Orobanchaceae) on the Qinghai‐Tibetan Plateau and its correlation with the Quaternary climate change

The Qinghai-Tibetan Plateau (QTP) is thought to be more strongly affected by the Quaternary glaciations than most other regions of the same latitude. It would be of great interest to investigate the population genetic structure of organisms distributed on the platform and its correlation with the Quaternary climatic oscillations. Here we used the chloroplast (cp)DNA trnT-trnF sequence to study genetic variation and phylogeography of Pedicularis longiflora, an alpine herb with extensive distribution on the QTP. Based on a range-wide sampling comprising 41 populations and 910 individuals, we detected 30 cpDNA haplotypes that were divided into five clades by phylogenetic and network analyses and a strong phylogeographical structure. All haplotypes but one in the three basal clades occur exclusively in the southeast QTP, whereas haplotypes in the young clade V occupy almost the whole species range. In particular, the young haplotype H18 occurs in 420 individuals, even at a frequency of 100% in some QTP platform populations and the Altai population. The haplotype distribution pattern, together with molecular clock estimation and mismatch distribution analysis, suggests that the southeast QTP was either a refuge for P. longiflora during the Quaternary climatic change or is the place of origin of the species. The present wide distribution of the species on the QTP platform has resulted from recent population expansions which could be dated back to 120,000-17,000 years ago, a period mostly before the last glacial maximum. The possible relationships among geographic genetic structure, climatic change and species diversification in Pedicularis are also discussed.

Do clonal growth form and habitat origin affect resource-induced plasticity in Tibetan alpine herbs?

To investigate how growth form and habitat origin affect phenotypic plasticity to resource supply in the Tibetan alpine herbs, the phalanx-type species Stipa capillacea and the guerilla-type species Carex montis-everestii were sampled from two different habitats (alpine steppe and alpine scrubland) and grown under three levels of light intensity and two levels of nutrient supply. Interspecific differences in light-induced plasticity were detected only in number of ramets, specific leaf area and leaf sheath length. Plasticity in plant biomass, number of ramets and rhizome length in response to light intensity differed between the two habitats. Stipa plants were more plastic than Carex plants in number of ramets and specific leaf area in response to light intensity. Carex plants from the alpine scrubland expressed greater light-induced plasticity in plant biomass and number of ramets than those from the alpine steppe, and Stipa plants showed less interhabitat differences in plasticity, which may be closely related to their contrasting growth forms. Clonal growth form and habitat origin affected nutrient-induced plasticity in none of the measured traits. It may be the guerilla growth form that makes Carex plants more efficiently adapted to highly heterogeneous light conditions in scrubland, and less habitat-dependent plasticity contributes to success of the phalanx-type Stipa plants in alpine habitats. The results are discussed in the context of foraging for heterogeneously distributed essential resources and adaptation to habitat origin.

Podophyllotoxin content in Podophyllum hexandrum Royle plants of known age of seed origin and grown at a lower altitude

Podophyllum hexandrum Royle, an important alpine herb, and a source of the highly valued aryltetralin-type lignan, podophyllotoxin, has been subjected to heavy collection from the wild due to ever increasing demand. The present study deals with an attempt to bring this plant under cultivation at a relatively lower altitude and to evaluate (1) various growth parameters including above and below ground biomass accumulation, net assimilation rate and relative growth rate, etc., and (2) podophyllotoxin content from the resulting above and below ground biomass in seed raised plants of a known age series of 1–5 years. The podophyllotoxin content was estimated on the basis of HPLC analyses. The levels were found to increase with the plant age and the maximum amount was found in 5-year old plants. This study demonstrates that (1) seeds can be conveniently used for raising healthy propagules in easily approachable locations at a relatively lower altitude, and that the plants can be maintained in such sites over long periods, and (2) this approach of “conservation through cultivation” can be suggested as an effective tool for the management of this “critically endangered status” species.

Adverse impacts of pasture abandonment in Himalayan protected areas: Testing the efficiency of a Natural Resource Management Plan (NRMP)

The high elevational areas in the Himalayas of India are dominated by forests and alpine pastures. There are many protected areas in the region, including Nanda Devi Biosphere Reserve (NDBR) and Valley of Flowers (VOF) where natural resource management plan (NRMP) has been implemented for the conservation of biodiversity. This has affected the traditional animal husbandry system, as well as the vegetation dynamics of alpine pastures. An integrated approach to studying the impact of NRMP in the region has been applied by us. First, a survey was conducted regarding livestock management, data pertaining the livestock husbandry, the role of animal husbandry in economics of rural household, and socioeconomics. Second, field based study on phytosociology of some important alpine herbs was done to enumerate the density and species richness in different land mark of the region. Thereafter, satellite data and Geographic Information System (GIS) were used to develop a land cover map of the area and to note changes in the landscape over time after implementation of NRMP. From an economic point of view the implementation of such plan is a setback to the rural economy. However, the ecological perspective of such models is a threat to the diversity of alpine pastures. The invasion of bushes/thorny bushes/shrubs and weeds with their luxuriant growth is changing the vegetation index and dynamics. Consequently, the diversity of herbs in alpine pastures of the Himalayan Mountains is in jeopardy. Overall, the situation is leading to landscape change in the region. This study is helpful for generating useful outcomes and strategies considering the question or debate “is grazing good or bad for pasture ecosystems in the Himalayas?”.

Late Glacial and Holocene vegetational history of the Altai Mountains (southwestern Tuva Republic, Siberia)

Two lakes of glacial origin (Grusha at 2413 m and Akkol at 2204 m) are located on a broad high-mountain plateau on the dry eastern end of the Russian Altai Mountains in the Republic of Tuva, just north of Mongolia. The present vegetation of the area is an open high-mountain tundra–steppe mosaic, with patches of Larix and Pinus sibirica forests on north-facing slopes 30 km northwest of the lakes. Alpine meadows occur near streams and snow patches. Pollen diagrams and radiocarbon dates (16 for Grusha and 12 for Akkol) were used to reconstruct the vegetational history since the last glaciation. The core from Grusha contains about 50 cm of Late Glacial sediment of relatively low organic content, mostly correlated with the Younger Dryas episode because of the high percentages of Artemisia, Gramineae, and Chenopodiaceae, along with a diversity of non-arboreal pollen types indicating tundra–steppe and meadow-steppe. In the earliest Holocene, starting with increased organic matter at about 195 cm (12,000 cal. yr BP), the Artemisia–Gramineae–Chenopodiaceae pollen assemblage continued, along with an increase in shrub Betula but without the diversity of minor non-arboreal types. The interpretation of dry and warm climate at this time is supported by the unconformity at Akkol, implying a dried lake. Then after about 1000 years the increase of Pinus sibirica, P. sylvestris, Picea obovata, and Abies sibirica suggests that forests developed in response to increased humidity, first at the higher-elevation Grusha, and then at Akkol. After about 6000 cal. yr BP the role of forests decreased sharply in the area. The Picea and Abies components almost disappeared, as they did also in more westerly areas of the Altai Mountains. Steppe elements increased along with alpine herbs, especially after 2000 cal. yr BP as a result of cooling or increased aridity, as well as probable human activity. Correlation of the vegetation sequence for the Tuva sites with those to the west in the central Altai Mountains indicates that the Late Glacial open landscapes persisted in the earliest Holocene but then were invaded by coniferous forests as a result of increased moisture and temperature associated with Atlantic storm systems as well as with insolation-enhanced Asian monsoon. Cooling and drying after about 6000 cal. yr BP brought the decline of Abies and Picea and the expansion of tundra–steppe.