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Treelines and treeline species are being studied the world over because of their sensitivity to climate change but most of these studies have not focused on the essential belowground mutualists which could influence the outcome of the interaction between treeline species and climate change, such as the treeline shift. To fill this knowledge gap, we processed 27 root samples of Betula utilis from two sites in the Kashmir Himalaya and identified 590 species of root-associated fungi belonging to 158 genera, 80 families, 38 orders, 15 classes and 3 phyla from a total of 9157 quality reads. Most of the identified species belonged to Basidiomycetes. Papiliotrema, Humaria, Sphaerobolus, Sebicina, Inocybe, Cryptococcus, Lactarius and Laccaria were the dominant taxa. Symbiotroph, Saproptroph-Symbiotroph and Saprotrophs were the dominant trophic modes of the identified root-associated fungi and most of the identified species belonged to the Ectomycorrhizae (ECM) guild. Differences in the species richness between the two sites were noted and a total of 511 taxa were recovered from root samples at the Sinthan Top site in south Kashmir whereas only 302 taxa were recovered from root samples at the Apharwat site in north Kashmir. Papiliotrema and Inocybe with > 75% prevalence represented the core microbiome. Our study provides the first detailed and comprehensive account of the diversity of fungi associated with the roots of B. utilis and paves way for exploring their functional role in the growth of this treeline species, particularly under changing climate. [ABSTRACT FROM AUTHOR]

Treeline patches are among Earth’s most sensitive and are important model ecosystems for assessing climate change trends. To explore ecological factors that limit the species’ survival in treelines, the treeline patch of Li Mountain National Nature Reserve was selected as the research site. Pinus armandii (P. armandii), Betula albo-sinensis (B. albo-sinensis), and Betula utilis (B. utilis) were selected as research species based on their dominance. Two 50 m × 50 m plots were established separately from the upper and lower limits of the highest treeline patch for point pattern analysis. Five 10 m × 10 m quadrats per plot were sampled to investigate the flora and environmental factors. The results showed that: (1) Slope and community composition at tree layer in quadrates had significant differences between upper and lower limits. Pinus armandii had a greater population size at the upper limit. Seedling recruitment restricted population development for B. albo-sinensis at the lower limit and B. utilis at the upper limit and less regeneration of B. albo-sinensis at the upper limit. (2) More aggregation scales occurred at the upper limit, and P. armandii had more aggregation scales than the other two species at 0–25 m. The heterogeneity caused by density distribution affected P. armandii pattern at the upper limit, and heterogeneity of seed dispersal could explain species patterns in both limits. Distinctness of size difference may have an influence on inter-specific species correlations. [ABSTRACT FROM AUTHOR]

Traditional wound dressings have a limited capacity to absorb exudates, are permeable to microbes, and may adhere to wounds, which leads to secondary injuries. Hydrogels are promising alternative dressings to overcome the above challenges. In this study, we developed sodium alginate-based hydrogel films loaded with Betula utilis bark extract. These films were prepared via solvent-casting crosslinking method and evaluated for wound healing activity. Prepared films were 0.05–0.083 mm thick, flexible with folding endurance ranging from 197–203 folds, which indicates good physical properties. Optimized formulations exhibited successful loading of extract in the film matrix without any interaction as confirmed by FTIR. Maximum zone of inhibition against Gram-positive and Gram-negative bacteria was achieved by optimum formulation (B6), i.e., 19 mm and 9 mm, respectively, with > 90% scavenging activity. Furthermore, this optimum formulation (B6) was able to achieve 93% wound contraction in rats. Histograms of the optimized formulation treated group also revealed complete reepithelization of wounds. Conclusively, our extract-loaded hydrogel dressing successfully demonstrated its potential for cutaneous wound healing.

The present study aimed to analyse the population structure, forest composition and regeneration dynamics of Betula utilis D.Don in two core zone of Nanda Devi Biosphere Reserve. A total of 346 plants species belonging to 198 genera and 82 families were recorded dominated by Asteraceae (24) followed by Rosaceae (21 species) and Ranunculaceae (19 species), respectively. The total tree stand density was ranged between 1133 ind.ha−1 and 2137 ind.ha−1 in the south and north aspect of the each sites. Among tree species B. utilis was showed the dominant tree species with highest density ranged between 663 ind.ha−1 and 1525 ind.ha−1 at north and south aspects of both sites. Highest seedling density (1033 saplings ha−1 and 1783 seedlings ha−1) and sapling density (1033 saplings ha−1 and 1470 saplings ha−1) was recorded for B. utilis in north and south aspects. The density-diameter curve of B. utilis forest resembled a reverse J-shape which exhibits good regeneration with higher number of individuals in seedling and sapling stages, followed by a sharp decline in tree classes. This study suggests urgent need of long term ecological monitoring of timberline zone to assess the significant change in timberline vegetation and development of sustainable management plans.

The sensitivity and response of climatic treelines in the Himalayas to climate change is still being debated. Regeneration of tree species in the treeline ecotone is considered a sensitivity indicator and thus of great scientific interest. The aim of this study is to detect predictor variables for regeneration densities of the major tree species in central Himalayan treeline ecotones (Abies spectabilis, Betula utilis, Rhododendron campanulatum), analysing five development stages from seedling to mature tree. We applied negative binomial generalized linear models with predictors selected from a wide range of soil, topography, climate and stand characteristic variables. We found considerably varying predictors across the tree species and their stages of development. Soil conditions, topography and climate, as well as competing and facilitating tree species, had high predictive power for population densities. These predictors were clearly species- and development stage-specific. Predictors' spatial- and development-specific heterogeneity induce a high degree of complexity and diversify any potentially linear response of tree population densities and treeline position to changing climatic conditions. [ABSTRACT FROM AUTHOR]

A simple, rapid, sensitive, and reliable ultra‐high‐performance liquid chromatography‐hybrid linear ion trap triple quadrupole mass spectrometry method was developed and validated for simultaneous determination of 10 bioactive compounds in stem bark of Betula utilis grown in high altitude of Himalaya, India. The objective of the study is to develop and validate ultra‐high‐performance liquid chromatography‐hybrid linear ion trap triple quadrupole mass spectrometry for investigation of geographical variations of triterpenoids, phenolics, and flavonoids contents in stem bark of B. utilis. The validated method was successfully applied to investigate geographical variations of triterpenoids, phenolics, and flavonoids in stem bark of B. utilis. The contents of betulinic acid and oleanolic acid were detected higher among selected analytes. The present variation study reveals great importance for the application and overall assessment of B. utilis. [ABSTRACT FROM AUTHOR]

The present study was conducted in Hamta Pass area of Kullu district, Himachal Pradesh, India with a focus on Betula utilis populations. Totally 16 populations of B. utilis representing four habitats and three aspects were studied. The maximum sites were represented by moist and moist, shaded habitats with northwestern aspect. Totally 188 plant species representing trees, shrubs and herbs were recorded. Acer acuminatum, Abies pindrow, Prunus cornuta and Quercus semecarpifolia were the major associated species of B. utilis in the subalpine zone of Hamta Pass. Based on importance value index five tree communities, namely A. acuminatum, A. pindrow, B. utilis, Q. semecarpifolia and B. utilis--P. cornuta mixed were identified. Among the communities, total density of trees, shrubs and herbs was recorded from 160 to 270, 300 to 515 and 21 to 33 individuals m--2 respectively. The total basal area recorded was 6.94--42.10 m2 ha--1, species richness 15--127, and species diversity for trees 0.4--0.9, shrubs 0.0--2.1 and herbs 1.7--4.2. The density and regeneration (i.e. seedlings and saplings) of B. utilis in most of the populations revealed that this species will continue to grow in the area. However, continued anthropogenic activities, climate change and other factors may cause population depletion in the study area. [ABSTRACT FROM AUTHOR]

The sensitivity and response of climatic treelines in the Himalayas to climate change is still being debated. Regeneration of tree species in the treeline ecotone is considered a sensitivity indicator and thus of great scientific interest. The aim of this study is to detect predictor variables for regeneration densities of the major tree species in central Himalayan treeline ecotones (Abies spectabilis, Betula utilis, Rhododendron campanulatum), analysing five development stages from seedling to mature tree. We applied negative binomial generalized linear models with predictors selected from a wide range of soil, topography, climate and stand characteristic variables. We found considerably varying predictors across the tree species and their stages of development. Soil conditions, topography and climate, as well as competing and facilitating tree species, had high predictive power for population densities. These predictors were clearly species- and development stage-specific. Predictors’ spatial- and development-specific heterogeneity induce a high degree of complexity and diversify any potentially linear response of tree population densities and treeline position to changing climatic conditions.

Question: Tree growth at high altitude in the Himalayan region is limited by cold temperatures and also strongly influenced by the seasonality of the Asian monsoon. Understanding whether the ongoing increase in temperatures and changes in precipitation regimes in the Himalayan region can stimulate or limit tree growth is of particular importance to predict the local treeline dynamics. Location: Altitudinal treeline (~4000 m a.s.l.) in the Sagarmatha (Mt. Everest) National Park (Central Himalaya, Eastern Nepal). Methods: We assessed the relationships between ring widths and monthly precipitations and mean temperatures, and analysed cellulose stable isotopes (δ13C and δ18O) and their derived C discrimination (Δ13C), and intrinsic water use efficiency (iWUE) in Abies spectabilis and Betula utilis at the Himalayan treeline. Results: Growth of A. spectabilis strongly depended on summer temperatures, whereas that of B. utilis on spring precipitation. δ13C and iWUE increased with time in both species, especially in A. spectabilis. The long‐term decrease in Δ13C was accompanied by an increase in δ18O in both species, thus suggesting an increase in photosynthetic efficiency rather than a stronger stomatal control of transpiration. Conclusions: Climate change is progressively reducing the physiological limitations due to low temperatures and low spring precipitations at the Central Himalayan treeline, thus potentially facilitating a further altitudinal forest advance. [ABSTRACT FROM AUTHOR]

Increase in endemism with elevation is a common feature in Himalayas because of increased isolation of higher areas like treelines. To protect species of treeline, we at least need to record their numbers and distribution. We estimated that the total number of tree species in Himalayan treeline is 58, and they belong to 14 genera and 8 families. It is impressive, given that globally alpine treeline species richness is unlikely to be considerably higher than 100. While estimating the species number, we confronted uncertainties in some cases concerning synonyms of species, weak demarcation between species and incorrect identification. Because of a high species differentiation in the Hengduan Mountains and Western Sichuan Province in Tibet, the eastern part of the Himalayan arc (88°E and more) has much higher species richness than the western part (less than 88°E), despite similar number of genera. These areas of high species differentiation accounted for nearly half of the total species. The dominant genera in terms of geographical distribution are Juniperus, Abies, Rhododendron, and Betula. Among the families, Pinaceae, Cupressaceae, Ericaceae, Betulaceae, and Rosaceae were prominent. Because of global climatic change, species shifts are predicted to occur along an altitudinal gradient (representing temperature gradient) as well as along the 31º longitudinal range, representing a moisture gradient. The Himalayan treelines are relatively species-rich, largely because of variations in precipitation, topography, continentality, and cultural factors, among others along the east-to-west arc. There is a need to undertake additional taxonomic studies, using tools such as molecular techniques to provide solution to confusion relating to incorrect identification of some species. [ABSTRACT FROM AUTHOR]

Aim: The spatial patterns of tree populations reflect multiple ecological processes. However, little is known on whether these patterns mediate responses to climate in marginal tree populations such as those forming alpine tree lines. We examined the influence of tree‐to‐tree interactions on the responsiveness of tree lines to climate warming. Location: Central Himalayas. Taxon: Betula utilis; Abies spectabilis. Methods: We analysed a network of 17 tree line sites located across the central Himalayas, encompassing a wide longitudinal gradient characterized by increasing precipitation eastwards. We quantified the changes in density and the spatial patterns of three 50‐year age classes of the two main tree species found at the tree line (Betula utilis and Abies spectabilis), and related them to reconstructed shifts in tree line elevation. Results: Younger trees showed clustering near the tree line, while older trees tended to show random spatial distribution. Clustering decreased as climate conditions ameliorated, that is, in the wetter eastern sites. Lower rate of tree line elevation change was observed at the sites with higher clustering intensity. Main Conclusions: Our study indicates that tree aggregation weakens tree line responsiveness to climate warming, and thus warming‐induced drought stress tends to lower tree line shift rates by enhancing clustering. It also highlights the complexity and contingency of site‐dependent tree line responses to climate. Hence, to advance our understanding of tree line processes, we should consider both direct and indirect influences of relevant biotic (tree‐to‐tree interactions) and abiotic (climate) drivers of tree line dynamics. [ABSTRACT FROM AUTHOR]

Betula utilis D. Don. is an important species of alpine Himalaya and forms the major treeline component of western Himalaya. The different populations of B. utilis are declining and are under high risk. In the present study, novel expressed sequence tag–simple sequence repeat (EST–SSR) primers were developed from expressed sequence tag (EST) data of different Betula species. Of the 10,796 designed primers, the percentages of di-, tri-, tetra-, penta-, and hexa-repeats were 36%, 35%, 15%, 5.5% and 7.7%, respectively. For validation, 50 primers were synthesized randomly and were characterized in 20 different B. utilis accessions from north-western Himalaya. Of these, 45 primers amplified fragments in a range of 1–6. The 24 polymorphic primers produced 111 fragments in aggregate with 4.6 fragments on average. Polymorphism information content (PIC) ranged from 0.288 in marker BUMS-24 to 0.497 in BUMS-3 and BUMS-7, with an average of 0.447 among polymorphic markers. Dendrogram based on Jaccard's similarity coefficient and UPGMA method showed that newly developed SSR markers distinguished twenty accessions of B. utilis into two groups. As no SSR markers were available in this species, the newly developed markers will foster molecular genetics research and conservation efforts for this species. [ABSTRACT FROM AUTHOR]

• Study was conducted to determine the best medium for in vitro pollen germination of B. utilis. • An effect of sucrose, boric acid, calcium nitrate, magnesium sulfate, potassium nitrate and time of incubation on pollen germination and tube growth was investigated. • The germination rate and pollen tube length varied significantly with different concentrations and incubation time. • Pollen grains collected immediately after anther dehiscence showed the best germination ability however steadily decreased with time. The study was conducted to determine the optimum medium for in vitro pollen germination for B. utilis based on germination percentages and length of the pollen tube. Studies about pollen germination and tube growth of B. utilis are limited. Therefore, this study aimed to investigate the effects of sucrose (1, 3, 5, 10 and 15%), boric acid (25, 50, 100 and 200 ppm), calcium nitrate (50, 100, 200, 300 and 400 ppm), magnesium sulfate (50, 100, 200 and 300 ppm) and potassium nitrate (50, 100 and 200 ppm) and time of incubation on pollen germination and tube growth. Pollen germination rates and tube growth were recorded periodically at 2, 4, 6, and 10 h. The length varied significantly with different concentrations and incubation time. The germination rate and pollen tube length varied significantly with different concentrations and incubation time. Pollen germination was maximal (98 ± 6.1%) when the germination medium contained 10% sucrose solution supplemented with 100 ppm H 3 BO 3 , 300 ppm Ca(NO 3) 2 , 200 ppm MgSO 4 and 100 ppm KNO 3, after 6 h of incubation. In addition, results revealed that pollen grains collected immediately after anther dehiscence showed the best germination ability but gradually decreased with time. [ABSTRACT FROM AUTHOR]

Himalayan Silver Fir (Abies spectabilis) and Himalayan Birch (Betula utilis) are tree species often found coexisting in sub-alpine forests of the Nepal Himalayas. To assess species-specific growth performances of these species, tree-ring samples were collected from the subalpine forest in the Dhorpatan Hunting Reserve, Nepal. Standard ring width chronologies of both species were correlated with climatic variables in both static and running windows. Differential and contrasting temporal responses of radial growth of these species to climate were found. Warmer and drier springs appeared to limit birch radial growth. Whereas radial growth of fir showed weakened climate sensitivity. Moving correlation analyses revealed divergent influences of spring climate on both fir and birch. Significant warming that occurred in the 1970s coincided with growth declines in birch and an increase in fir, as indicated by basal area increment. In summary, recent warming has been unfavorable for birch, and favorable to fir radial growth.

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In this study on treeline phenology in Tungnath, Garhwal Himalaya (altitude, 2955-3334 m asl), we (i) collected data on micro-climatic conditions, timing of major phenophases, leaf and shoot growth phenology and leaf nitrogen resorption in four major tree species (Abies spectabilis, Betula utilis, Quercus semecarpifolia, Rhododendron arboreum) and a krummholz species (R. campanulatum); and (ii) compared the treeline species phenology with mid-altitude forest tree species phenology of this region. Meteorological data reported for this site revealed that the mean monthly atmospheric temperature during growing period (July-September) has increased at the rate of 0.11 °C yr-1 in the last two decades. Leaf bud-break occurred in all the species in May, however, the proportion of marked tree population in bud-break phase at the time of first observation in May varied considerably across the species from 10% in Q. semecarpifolia to 50% in R. arboreum. Leaf initiation and leafing in the treeline species was delayed by about two months, compared to the mid-altitude tree species. Also, the leaf expansion within one month of leafing was conspicuously slower in treeline species than mid-altitude species (43% vs. 83% in Quercus spp. and 49% vs. 76% in R. arboreum). The treeline species were characterized by short growing period (2-4 months), lower period of steady-state in peak leaf mass and rapid leaf mass loss, low nitrogen concentration in leaves (1.7% vs. 2.5%), slow shoot growth, lower shoot length (5.6 cm vs. 9.5 cm) and shoot growth period, and higher leaf density in shoots (1.2 vs. 0.8 leaves cm-1 shoot length) than the mid-altitude forest trees. It is expected that with the increasing rate of warming in Tungnath the phenological behaviour of treeline species would change markedly in future leading to changes in ecosystem properties. [ABSTRACT FROM AUTHOR]

The Himalayas is one of the most ecologically sensitive and fragile areas in the world. The climate of the region is dominated by the monsoon seasonality, with typical dry winters and abundant summer precipitations. Here, forest vegetation spreads up to the world’s highest elevations, where cold temperatures and early spring droughts represent the main limiting factors for growth. In this study, we applied a dendro-anatomical approach to assess xylem trait chronologies and their association to local climate variability in the diffused broadleaved Betula utilis D Don close to the treeline (above 3900 m a.s.l.). We measured tree-ring width on increment cores from 73 trees. On seven cores, we prepared 12 μm thick sections, which were analysed with ROXAS for the assessment of ring-based xylem parameters. We then built up the corresponding trait chronologies and analyzed them against the time series of monthly temperatures and precipitations. Mean ring width (MRW), mean vessel area (MCA_V) and ring-specific hydraulic conductivity (Kr) positively correlated with summer temperatures in the previous and current year. In addition, MCA_V was significantly associated with March precipitations. Instead, fibres’ area showed a widely negative correlation only with temperatures during the previous and current season suggesting that fibres get narrower when vessels are wider. These results revealed that Himalayan birch is well adapted to the monsoon seasonality and is responding positively to atmospheric warming, thus suggesting the potential for this species to further expand in altitude under the forecasted climate change scenarios. [ABSTRACT FROM AUTHOR]

A treeline can respond to climate change by shifting position, infilling, increasing recruitment, and increasing radial growth. More studies from understudied areas and their associated species are needed to understand treeline structure and dynamics. We established two transects of 20 m width and 120 m length (100 m above and 20 m below the forestline) in the Betula utilis subalpine forest of the Dhorpatan Hunting Reserve in Western Nepal. All individuals of B. utilis within the transects were classified into three height classes - trees (>2 m), saplings (0.5-2 m), and seedlings (<0.5 m) - and measured for morphometric features. Tree-ring cores were collected for age structure analysis. B. utilis forms an abrupt treeline in the region, and the mean forestline and treeline elevations were 3893 and 3898 m, respectively. The average age (57 yr) of trees at the treeline ecotone suggests a young stand. Poor regeneration was observed above the forestline in both transects when compared to below the forestline. Low regeneration at the treeline ecotone suggests site-specific biotic and abiotic controlling factors. Seedling and sapling establishment above the forestline is limited by a lack of moisture, absence of suitable microsites, and presence of herbivores. [ABSTRACT FROM AUTHOR]

Betula utilis, commonly known as Himalayan birch is an important tree species of fragile ecosystem of Himalayas placed in endangered category. In the present study genetic diversity, structure and interrelationships of B. utilis accessions from North-western Himalayan regions were analyzed using Random Amplified Polymorphic DNA (RAPD) and Inter Simple Sequence Repeat (ISSR) markers. 15 RAPD and 16 ISSR primers collectively amplified 109 polymorphic fragments with an average of 3.51 fragments in a size range of 300-1300 bp. Polymorphism Information Content (PIC) ranged from 0.21 to 0.5 with an average of 0.43. Dendrogram grouped all the accessions into two major clusters. Factorial analysis showed three groups for all the analyzed accessions. Bayesian clustering using STRUCTURE grouped all the accessions in two clusters and separated majority of accessions belonging to Jammu & Kashmir Himalaya (cluster-II) from other accessions of Himachal Pradesh and Uttarakhand Himalaya (cluster-I). Exceptionally, four accessions namely, Sinth-12, Sinth-20, Son-06 and Son-16 from Kashmir grouped in Cluster-I. Structure analysis showed that two genetic stocks were contributing in genetic makeup of all the analyzed accessions. Results of the present study can be useful for selection of diverse accessions as well as can be useful in designing conservation and management strategies in North-western Himalayan regions. [ABSTRACT FROM AUTHOR]

This article enfolds a rapid and sensitive high-performance thin-layer chromatographic (HPTLC) method for the estimation of four triterpenoids, namely, betulin (BU), betulinic acid (BA), lupeol (LU), and oleanolic acid (OA), from the bark, roots, and leaves of Betula utilis D. Don, an endangered Himalayan tree. All the four phytoconstituents have high therapeutic value. Separation was performed on thin-layer chromatography (TLC) aluminum plates precoated with silica 60 F254 (20 × 20 cm) followed by detection of betulin, lupeol, and oleanolic acid carried out by derivatizing the plate with ceric ammonium sulfate followed by heating at 110°C for 5 min. For betulinic acid, the plate was dried and visualized after spraying with Liebermann-Burchard reagent. CAMAG TLC Scanner 4 equipped with winCATS software was used for densitometric scanning at 500-550 nm. The proposed technique was further validated in terms of linearity, precision, accuracy, and sensitivity as per the International Conference on Harmonisation (ICH) guidelines. A good linear relationship was obtained for the calibration plots with r² = 0.9994, 0.9995, 0.9969, and 0.9998 for betulin, lupeol, oleanolic acid, and betulinic acid, respectively. Accuracy of the method was checked by recovery study conducted at three different levels with the average recovery between 98.9% and 99.3% for all the four markers. [ABSTRACT FROM AUTHOR]

Seedling establishment is a crucial factor for spatial dynamics of treelines. However, safe sites for successful tree regeneration which is a basic prerequisite for a supposed treeline advance in response to climate warming have not been fully characterised, especially in the Himalayas. In this study, we aim at analysing safe sites of the tree species Abies spectabilis, Betula utilis and Rhododendron campanulatum, dominating the near-natural treeline ecotone in Rolwaling Himal, Nepal. We investigated microhabitat ground cover of established seedlings in rectangular plots along the treeline ecotone from subalpine forest stands via the krummholz belt to alpine dwarf shrub heaths (3800-4200 m). We examined protective elements that potentially ameliorate seedlings' growth conditions and quantified the distance of seedlings to the nearest protective element. Our results showed species-specific microhabitat preferences for seedling establishment. While A. spectabilis seedlings establish on ground that is covered in average by 70% with litter, B. utilis and R. campanulatum seedlings primarily emerge on bryophyte mats (mean site cover 80%). Microhabitat structure did not vary significantly in relation to different vegetation types encompassing the treeline ecotone. The majority of seedlings of all species grew in maximum 2 m distance to at least one potentially protective element. Geomorphic elements and deadwood were the most important shelters for seedling establishment. Our results emphasise the importance of safe sites for successful tree regeneration in harsh environments. As growth conditions in high mountain ecosystems may substantially alter under contemporary climate change, the necessity of safe sites may increase to buffer potential extremes. [ABSTRACT FROM AUTHOR]

Betula utilis is a major constituent of alpine treeline ecotones in the western and central Himalayan region. The objective of this study is to analyse for the first time the performance of different climatic predictors in modelling the potential distribution of B. utilis in the subalpine and alpine belts of the Himalayan region. Using Generalized Linear Models (GLM) we aim at examining climatic factors controlling the species distribution under current climate conditions. We evaluate the predictive ability of climate data derived from different statistical methods GLMs were created using least correlated bioclimatic variables derived from two different climate data sets: 1) interpolated climate data (i.e. WORLDCLIM; Hijmans et al., 2005), and 2) quasi-mechanistical statistical downscaling (i.e. CHELSA; Karger et al., 2016). Model accuracy was evaluated using threshold-independent (Area Under the Curve) and threshold-dependent (True Skill Statistics) measures. Although there were no significant differences between the models in AUC, we found highly significant differences (p ≤ 0.01) in TSS. We conclude that models based on variables of CHELSA climate data had higher predictive power, whereas models using WORLDCLIM climate data consistently overpredicted the potential suitable habitat for B. utilis . Although climatic variables of WORLDCLIM are widely used in modelling species distribution, our results suggest to treat them with caution when topographically complex regions like the Himalaya are in focus. Unmindful usage of climatic variables for environmental niche models potentially causes misleading projections. [ABSTRACT FROM AUTHOR]

Changes in the position of altitudinal treelines and timberlines are considered useful indicators of climatic changes on tree growth and forest dynamics. We sought to determine if recent warming is driving contrasting growth responses of Himalayan birch, at moist treeline (Lete Lekh) and semi-arid timberline (Chimang Lekh) sites in the Trans-Himalayan zone of central Nepal. We used dendrochronological techniques to measure tree ring width (TRW) and basal area increment (BAI) of birch trees from climatically contrasting but nearby sites. The TRW series were correlated with climate records from nearby meteorological stations, and BAI was compared between populations to explore growth trends over recent decades. We found contrasting precipitation trends between nearby sites such that the wet site (Lete) is getting warmer and wetter, and the dry site (Chimang) is getting warmer and drier in recent decades. The radial growth of birch in both moist and semi-arid sites are positively correlated to spring (March-May) rainfall, and negatively correlated to mean and maximum temperature for the same period. The growth climate analysis indicated that moisture availability in early growing season is crucial for birch growth at these locations. The BAI of birch is declining more rapidly at the dry timberline than at the moist treelines in the recent decades, indicating that climatic warming might negatively impact birch radial growth where warming interacts with increasing spring drought in the region. Our work highlights contrasting growth response of birch to climate change at moist and semi-arid forests indicating that local climatic variation must be accounted for when assessing and forecasting regional patterns of tree growth in topographically complex regions like Trans-Himalaya, in order to make accurate predictions of vegetation responses to climate change. [ABSTRACT FROM AUTHOR]

Objective: The present study investigated the comparative analysis of fatty acid and antioxidant activity from the bark of Betula utilis, collected from Kashmir and Sikkim coded as BUK and BUS respectively. Methods: Fatty acid constituents were analyzed by GCMS (gas chromatography mass spectroscopy) in BUK and BUS bark. B. utilis bark extracts of both the locations were phytochemically investigated and radical scavenging activity was evaluated by DPPH in all solvent fractions. Results: Phenolic content were found to be higher in methanolic extracts of BUK bark, 5.8 ± 0.1 mg/gm and flavonoid content were higher in the water extract of BUK bark, 6.16 ± 0.2 mg/gm. The radical scavenging activity was found to be higher methanolic, alcoholic and water extracts of BUK bark. The lowest IC50 value for radical scavenging activity of methanolic and water extracts of B. utilis bark collected from Kashmir were found 18.7 ± 1.1 and 18.2 ± 0.3 µg/mL, respectively. Thirteen fatty acids were identified in the sample BUK as well as BUS in which the major fatty acids were found-Palmitic acid, linoleic acid and oleic acid. BUK possess the highest amount of Palmitic acid (18.07%) in oily portion of the bark. Conclusion: The present study concluded that BUK and BUS extracts have shown significant antioxidant activity in comparison to standard but BUK possess potent radical scavenging activity over BUS, and higher amounts palmitic acid, linoleic acid and oleic acid was present in the extract, and may a play an important role in nutritional and pharmaceutical applications. [ABSTRACT FROM AUTHOR]

A rapid and reliable method was developed and validated for determining betulin and betulinic acid in bark inBetula utilisby high-resolution magic angle spinning1H nuclear magnetic resonance (HR-MAS NMR) spectroscopy. HR-MAS NMR spectroscopy clearly distinguished the resonances of betulin and betulinic acid in the bark of all accessions ofB. utilis. The concentrations of betulin and betulinic acid were calculated and added to the spectra. The determination of the targeted metabolites in chloroform extract of bark of each accession ofB. utiliswas performed by high-performance liquid chromatography (HPLC). Quantitatively, betulin was present at higher concentrations than betulinic acid in all accessions. The HR-MAS NMR and HPLC results showed that betulin and betulinic acid varied significantly among accessions ofB. utilis. Principal component analysis of the NMR and HPLC results provided classification into three metabolic groups in which the betulin concentration was high, moderate, or low. The results show that HR-MAS NMR is rapid for fingerprinting of betulin and betulinic acid in the bark ofB. utilis, while minimizing the drawbacks associated with solvent extraction. [ABSTRACT FROM PUBLISHER]

The phenological events, height class distribution, volume and biomass of Himalayan birchor bhojpatra (B. utilis D. Don) were monitored along the altitudinal gradient in distinct ecological settings at Sindh and Tangmarg forest divisions in western Himalayas, Kashmir. The observations recorded revealed high synchrony throughout the altitudinal gradients, especially for bud set, bud burst, peak flowering and seed maturation. All the phenological events began early at lower elevation as compared to higher elevation. The timing of phenophases along the altitude was governed by the timing of snow-melt which is usually responsible for early phenological changes in the northern alpine habitats. The height, volume and biomass showed a decreasing trend with increasing altitude at both the sites. Higher number of trees (116.71 trees/ha) with maximum height, volume (112.38 m3/ha) and biomass (57.31 tonnes/ha) were recorded at 3 000-3 200 m asl. The values for all these parameters decreased with increasing altitude from 3 200-3 400 and 3 400-3 600 m amsl, respectively. The short growing seasons, reduced air and soil temperature (an adiabatic effect), increased exposure to wind, lower availability of nutrients and increased exposure to frost are some of the common features of high altitude niches which greatly influences the growth of the existent vegetation.

Modelling ecological niches across vast distribution ranges in remote, high mountain regions like the Himalayas faces several data limitations, in particular nonavailability of species occurrence data and fine-scale environmental information of sufficiently high quality. Remotely sensed data provide key advantages such as frequent, complete, and long-term observations of land surface parameters with full spatial coverage. The objective of this study is to evaluate modelled climate data as well as remotely sensed data for modelling the ecological niche of Betula utilis in the subalpine and alpine belts of the Himalayan region covering the entire Himalayan arc. Using generalized linear models (GLM), we aim at testing factors controlling the species distribution under current climate conditions. We evaluate the additional predictive capacity of remotely sensed variables, namely remotely sensed topography and vegetation phenology data (phenological traits), as well as the capability to substitute bioclimatic variables from downscaled numerical models by remotely sensed annual land surface temperature parameters. The best performing model utilized bioclimatic variables, topography, and phenological traits, and explained over 69% of variance, while models exclusively based on remotely sensed data reached 65% of explained variance. In summary, models based on bioclimatic variables and topography combined with phenological traits led to a refined prediction of the current niche of B. utilis, whereas models using solely climate data consistently resulted in overpredictions. Our results suggest that remotely sensed phenological traits can be applied beneficially as supplements to improve model accuracy and to refine the prediction of the species niche. We conclude that the combination of remotely sensed land surface temperature parameters is promising, in particular in regions where sufficient fine-scale climate data are not available.