High-altitude Site Research Articles

Gene expression in the female tree swallow brain is associated with inter- and intra-population variation in glucocorticoid levels

Studies of the evolutionary causes and consequences of variation in circulating glucocorticoids (GCs) have begun to reveal how they are shaped by selection. Yet the extent to which variation in circulating hormones reflects variation in other important regulators of the hypothalamic-pituitary-adrenal (HPA) axis, and whether these relationships vary among populations inhabiting different environments, remain poorly studied. Here, we compare gene expression in the brain of female tree swallows (Tachycineta bicolor) from populations that breed in environments that differ in their unpredictability. We find evidence of inter-population variation in the expression of glucocorticoid and mineralocorticoid receptors in the hypothalamus, with the highest gene expression in a population from an extreme environment, and lower expression in a population from a more consistent environment as well as in birds breeding at an environmentally variable high-altitude site that are part of a population that inhabits a mixture of high and low altitude habitats. Within some populations, variation in circulating GCs predicted differences in gene expression, particularly in the hypothalamus. However, some patterns were present in all populations, whereas others were not. These results are consistent with the idea that some combination of local adaptation and phenotypic plasticity may modify components of the HPA axis affecting stress resilience. Our results also underscore that a comprehensive understanding of the function and evolution of the stress response cannot be gained from measuring circulating hormones alone, and that future studies that apply a more explicitly evolutionary approach to important regulatory traits are likely to provide significant insights.

The ARTI framework: cosmic rays atmospheric background simulations

ARTI is a complete framework designed to simulate the signals produced by the secondary particles emerging from the interaction of single, multiple, and even from the complete flux of primary cosmic rays with the atmosphere. These signals are simulated for any particle detector located at any place (latitude, longitude and altitude), including the real-time atmospheric, geomagnetic and detector conditions. Formulated through a sequence of codes written in C++, Fortran, Bash and Perl, it provides an easy-to-use integration of three different simulation environments: MagnetoCosmics, CORSIKA and Geant4. These tools evaluate the geomagnetic field effects on the primary flux and simulate atmospheric showers of cosmic rays and the detectors’ response to the secondary flux of particles. In this work, we exhibit the usage of the ARTI framework by calculating the total expected signal flux at eight selected sites of the Latin American Giant Observatory: a cosmic ray Observatory all over Latin America covering a wide range of altitudes, latitudes and geomagnetic rigidities. ARTI will also calculate the signal flux expected during the sudden occurrence of a gamma-ray burst or the flux of energetic photons originating from steady gamma sources. It also compares these fluxes with the expected background when they are detected in a single water Cherenkov detector deployed in a high-altitude site. Furthermore, by using ARTI, it is possible to calculate in a very precise way the expected flux of high-energetic muons and other secondaries at the ground level and to inject them through geological structures for muography applications.

Variability of ambient black carbon concentration in the Central Himalaya and its assessment over the Hindu Kush Himalayan region

During 2015–2018, eight black carbon (BC) monitoring sites were established in Nepal and Bhutan to fill a significant data gap regarding BC measurement in Central Himalaya. This manuscript analyzes and presents data from these eight stations and one additional station on the Tibetan plateau (TP). Complex topography, varied emission sources, and atmospheric transport pathways significantly impacted the BC concentrations across these stations, with annual mean concentrations varying from 36 ng m−3 to 45,737 ng m−3. Higher annual mean concentrations (5609 ± 4515 ng m−3) were recorded at low-altitude sites than in other locations, with seasonal concentrations highest in the winter (7316 ± 2541 ng m−3). In contrast, the annual mean concentrations were lowest at high-altitude sites (376 ± 448 ng m−3); the BC concentrations at these sites peaked during the pre-monsoon season (930 ± 685 ng m−3). Potential source contributions to the total observed BC were analyzed using the absorption angstrom exponent (AAE). AAE analysis showed the dominance of biomass burning sources (>50 %), except in Kathmandu. By combining our data with previously published literature, we put our measurements in perspective by presenting a comprehensive assessment of BC concentrations and their variability over the Hindu Kush Himalayan (HKH) region. The BC levels in all three geographic regions, high, mid, and low altitude significantly influenced by the persistent seasonal meteorology. However, the mid-altitude stations were substantially affected by valley dynamics and urbanization. The low-altitude stations experienced high BC concentrations during the winter and post-monsoon seasons. Concentration weighted trajectory (CWT) and frequency analyses revealed the dominance of long-range transported pollution during winter over HKH, from west to east. South Asian sources remained significant during the monsoon season. During pre- and post-monsoon, the local, regional, and long-distance pollution varied depending on the location of the receptor site.

High Spatial Variability of Biomass Burning Emissions Observed at Three Tibetan Plateau Sites

AbstractAerosol from biomass burning (BB) can affect regional and global climate by changing radiation balance and cloud properties, especially over the high altitude environ‐vulnerable region. To investigate the contributions of BB on atmospheric particulate matter trans‐the Tibetan Plateau (TP), the total suspended particle samples were collected at three high altitude sites over the northeastern (Qinghai lake, 3,200 m a.s.l.), central (Beiluhe, 4,659 m a.s.l.), and southwestern TP (Ngari, 4,360 m a.s.l.), respectively. Highly spatial variations of BB tracers (including levoglucosan, mannosan, and galactosan) were obtained. Elevated BB tracer concentrations were observed in the northeastern and southwestern sites compared to the central TP site. The heighten concentrations of particulate matter from biomass burning and organic carbon from biomass burning were obtained at Ngari (with 5260.3 and 2257.7 ng m−3) and Qinghai lake (with 1508.8 and 647.6 ng m−3) compared with those at Beiluhe (with 18.8 and 8.1 ng m−3), respectively. The results indicated that the BB contributions to aerosol were significant on the margin of the TP. In addition to the long‐range transport of BB pollutant, the local emissions may be an important contributor in the northeastern and southwestern TP. The present study can improve the understanding of BB characteristics and effects in the TP.

Species conflict at Earth’s edges – Contests, climate, and coveted resources

Direct conflict between species is an infrequently witnessed biological phenomenon. Potential drivers of such contests can include climate change, especially at Earth’s high elevation and latitudinal extremes where temperatures warm 2–5 times faster than elsewhere and hydro-geomorphic processes such as glacial recession and soil erosion affect species access to abiotic resources. We addressed a component of this broader issue by empirical assessments of mammalian conflict over access to four abiotic resources – minerals, water, snow, and shade – by annotation of past studies and by empirical data collection. Evidence for Nearctic and Palearctic mammals indicates that when desert waters are in short supply, contests intensify, generally favoring larger species regardless of their status as native or exotic. Our empirical data indicate that contests between two large and approximately similarly-sized mammals – mountain goats (Oreamnos americanus) and bighorn sheep (Ovis canadensis) – along a 2,500 km gradient at three high-altitude (above tree-line) sites in the Rocky Mountains of North America, result in striking asymmetries; goats dominated > 95% of interactions. Despite far fewer observations of encounters to access shade or snow patches, an increasingly prominent dialog needs to be held about rarely explored biological phenomena where less is known than we might otherwise presume, whether induced by climate or increasing anthropological alteration because of underpinnings to understand community structure and conservation planning. Observations on the frequency and intensity by which individuals escalate behavior to access abiotic resources remains an underappreciated arena to help identify the proximate importance of scarcity in the natural environment. Notwithstanding Darwin’s prediction some 165 years ago that populations in extreme environments (high-latitude, high-altitude) are more likely to be impacted by abiotic variables than biotic, conflict between species may be reflective of climate degradation coupled with the changing nature of coveted resources.

Radial growth, present status and future prospects of west Himalayan fir (Abies pindrow Royle) growing in the moist temperate forest of Himalayan mountains of Pakistan

Forests play a significant role for maintaining the biodiversity. In order to manage sustainable forests, tree species history, distribution, and their future prospects are vital. Using standardized quantitative approaches, the age, radial growth, and size class distribution of Abies pindrow (Himalayan fir) were determined from three different altitudinal sites (i.e. high, middle, and lower). The results indicate that Himalayan fir growing in the high-altitude site (Ayubia, 2 917 m a.s.l.) of moist temperate forests of the Himalayan mountains showed lower radial growth (0.13 cm) than in the middle (Bara Gali, 2 617 m a.s.l.; radial growth = 0.13 cm) and lower (Kuldana, 2 455 m a.s.l.; radial growth = 0.22 cm) altitude sites. Correlation analysis demonstrated that age showed a significant positive correlation (P < 0.001) with diameter at breast height. The tree-ring width chronology (totally 80 core samples) of Himalayan fir was developed from moist temperate forests of Himalayan mountains of Pakistan. At Ayubia site it possesses a long time-span (1703–2020 C.E.), followed by Bara Gali (1862–2020 C.E.) and Kuldana (1864–2020 C.E.). Further, the tree-ring width (TRW) chronology of Ayubia showed a significant positive correlation (P < 0.05) with May and June temperature, and a significant negative correlation (P < 0.05) with June and October precipitation, indicating that summer temperatures are the key factor for the radial growth of Himalayan fir. For the Kuldana site, the response of TRW chronology to temperature and precipitation was the same, however, it was significant only for June temperature at Bara Gali. The size class distribution of the high-altitude region (Ayubia) showed a higher number of individuals than the lower altitude region, indicating the lowest disturbance conditions. The absence of individuals in the early size classes and the gap in middle and mature size classes indicate a lower regeneration potential and anthropogenic impact. The pointer year analysis indicated that the Bara Gali forest is more sensitive to abnormal climate events than the other sites. Based on the present study, we suggest that proper attention and conservation strategy should be provided to Himalayan fir growing in the moist temperate forests of Pakistan.

Life history variation between two Eurasian tree sparrow Passer montanus populations at different altitudes

Abstract Altitudinal gradients create environmental variation that can strongly affect avian life history strategies. To fully understand this issue, a comparison of the demography of populations of the same species over large altitudinal differences is required. Here, we investigated the breeding ecology of two populations of Eurasian tree sparrow (Passer montanus), one in the temperate zone of central China at an altitude of 30 m and another in the alpine zone of the northeastern Tibetan plateau at an altitude of 3430 m. The breeding ecology of this species was rarely studied at such a high altitude before. Our result revealed that high-altitude tree sparrows started breeding later, had a shorter breeding period (80 versus 140 days), produced smaller broods (1.2 versus 2.5 chicks) and had significantly smaller clutches (4.0 versus 4.9 eggs) but larger eggs (4272 versus 3443 mm3) when compared with their low-altitude counterparts. Besides, tree sparrows at our high-altitude site had longer nestling periods (14.5 versus 13.4 days) than those at the low-altitude site. High-altitude tree sparrows tend to have reduced fecundity but allocate more energy into each offspring to confront the stressful conditions at high altitudes. The observed patterns are consistent with adaptive life history strategies.

Nonnegligible biogenic organic aerosol and the correlations with light absorption at three high altitude locations in the Qinghai–Tibetan Plateau

To investigate the contribution of primary biological aerosol particles (PBAPs) to aerosol and the correlations with brown carbon (BrC) light absorption over the Tibetan Plateau (TP), the total suspended particle (TSP) samples were collected at three high altitude sites. The spatial variations of PBAPs tracers and absorption Ångström exponent (AAE) were obtained over the TP for the first time. Elevated PBAPs tracers concentrations were observed in the northeastern and southwestern sites compared to the central TP. The high concentrations of FSPD OC (the fungal-spore-derived OC and plant-debris OC) and PBAPs were obtained in the northeastern (with 74 ng m−3 and 2333 ng m−3) and southwestern sites (with 80 ng m−3 and 2682 ng m−3), respectively. The results indicated that PBAPs may be important fraction of BrC chromophores in the southwestern TP. The highest AAEs of BrC, primary BrC (BrCpri), and secondary BrC (BrCsec) were observed in the northeastern site with the values of 5.1, 3.7, and 5.7, respectively. The potential PBAPs and FSPD OC source distributions were obtained. The results are important for evaluating the effects of PBAPs in the TP.

Evaluation of the Sources, Precursors, and Processing of Aerosols at a High-Altitude Tropical Site.

This work presents the results from a set of aerosol- and gas-phase measurements collected during the BIO-MAÏDO field campaign in Réunion between March 8 and April 5, 2019. Several offline and online sampling devices were installed at the Maïdo Observatory (MO), a remote high-altitude site in the Southern Hemisphere, allowing the physical and chemical characterization of atmospheric aerosols and gases. The evaluation of short-lived gas-phase measurements allows us to conclude that air masses sampled during this period contained little or no anthropogenic influence. The dominance of sulfate and organic species in the submicron fraction of the aerosol is similar to that measured at other coastal sites. Carboxylic acids on PM10 showed a significant contribution of oxalic acid, a typical tracer of aqueous processed air masses, increasing at the end of the campaign. This result agrees with the positive matrix factorization analysis of the submicron organic aerosol, where more oxidized organic aerosols (MOOAs) dominated the organic aerosol with an increasing contribution toward the end of the campaign. Using a combination of air mass trajectories (model predictions), it was possible to assess the impact of aqueous phase processing on the formation of secondary organic aerosols (SOAs). Our results show how specific chemical signatures and physical properties of air masses, possibly affected by cloud processing, can be identified at Réunion. These changes in properties are represented by a shift in aerosol size distribution to large diameters and an increased contribution of secondary sulfate and organic aerosols after cloud processing.

Impact of the selected boundary layer schemes and enhanced horizontal resolution on the Weather Research and Forecasting model performance on James Ross Island, Antarctic Peninsula

The output of the various Weather Research and Forecasting (WRF) model configurations was compared with ground-based observations in the northern part of James Ross Island, Antarctic Peninsula. In this region, a network of automatic weather stations deployed at ice-free sites (as well as small glaciers) is operated by the Czech Antarctic Research Programme. Data from these stations provide a unique opportunity to evaluate the WRF model in a complex terrain of James Ross Island. The model was forced by the ERA5 reanalysis data and the University of Bremen sea ice data. The model configurations include a novel Three-Dimensional Scale-Adaptive Turbulent Kinetic Energy (3D TKE) planetary boundary layer scheme and a more traditional Quasi-Normal Scale Elimination (QNSE) scheme. Impact of model horizontal resolution was evaluated by running simulations in both 700 m and 300 m. The validation period, 25 May 2019 to 12 June 2019, was selected to cover different stratification regimes of air temperature and a significant snowfall event. Air temperature was simulated well except for strong low-level inversions. These inversions occurred in 44% of all cases and contributed to a higher mean bias (2.0–2.9°C) at low-elevation sites than at high altitude sites (0.2–0.6°C). The selection of the 3D TKE scheme led to improvement at low-elevation sites; at high altitude sites, the differences between model configurations were rather small. The best performance in wind speed simulation was achieved with the combination of the 3D TKE scheme and 300 m model resolution. The most important improvement was decrease of bias at a coastal Mendel Station from 3.5 m·s‑1 with the QNSE scheme on the 700 m grid to 1.2 m·s‑1 with the 3D TKE scheme on the 300 m grid. The WRF model was also proven to simulate a large snowfall event with a good correspondence with the observed snow height.

Distribution and assemblage structure of black flies of the western Aures Mountains, Algeria (Diptera: Simuliidae)

Besides their important ecological role in flowing waters, blackflies (Diptera: Simuliidae) may pose medical and veterinary risks. For seventeen months, we surveyed the blackflies of ten localities across the Aures Mountains, in the Saharan Atlas, Algeria, and recorded eight taxa (i.e. species, species groups or species complexes). High altitude sites were dominated by the Simulium ornatum (Meigen, 1818) group, whereas sites located on the southern slope of the Aures Mountains were occupied by the eurytopic Simulium velutinum (Santos Abreu, 1922) complex and the thermophilic, pollutant-tolerant Simulium ruficorne Macquart, 1838 ‘A’ morphotype.Co-inertia analysis was used to determine the relationship between a species’ abundance and habitat types. The co-inertia analysis revealed a likely co-structure between blackfly assemblages and measured environmental descriptors (water temperature, conductivity, current velocity, bed width, etc.) in sampled habitats. This confirmed the importance of altitude as a driver of blackfly distribution. Our results also showed that there has been an increase in anthropogenic pressures on the vulnerable freshwater biota of the Aures Mountains.

Observed features of monsoon low-level jet and its relationship with rainfall activity over a high-altitude site in Western Ghats, India

Observed features of monsoon low-level jet and its relationship with rainfall activity over a high-altitude site in Western Ghats, India

Increasing Accumulation of Perfluorocarboxylate Contaminants Revealed in an Antarctic Firn Core (1958-2017).

Perfluoroalkyl acids (PFAAs) are synthetic chemicals with a variety of industrial and consumer applications that are now widely distributed in the global environment. Here, we report the measurement of six perfluorocarboxylates (PFCA, C4–C9) in a firn (granular compressed snow) core collected from a non-coastal, high-altitude site in Dronning Maud Land in Eastern Antarctica. Snow accumulation of the extracted core dated from 1958 to 2017, a period coinciding with the advent, use, and geographical shift in the global industrial production of poly/perfluoroalkylated substances, including PFAA. We observed increasing PFCA accumulation in snow over this time period, with chemical fluxes peaking in 2009–2013 for perfluorooctanoate (PFOA, C8) and nonanoate (PFNA, C9) with little evidence of a decline in these chemicals despite supposed recent global curtailments in their production. In contrast, the levels of perfluorobutanoate (PFBA, C4) increased markedly since 2000, with the highest fluxes in the uppermost snow layers. These findings are consistent with those previously made in the Arctic and can be attributed to chlorofluorocarbon replacements (e.g., hydrofluoroethers) as an inadvertent consequence of global regulation.

Altitudinal variation in life-history features of a Qinghai-Tibetan Plateau lizard.

Environmental changes along an altitudinal gradient can facilitate the differentiation of life-history features in ectothermic species, but little attention has been devoted to the reciprocal influence of altitude and alpine slope directionality on life-history variation. According to life-history theory, increased environmental stress causes a change in reproductive allocation from number to quality of offspring, as well as a stronger trade-off between size and number of offspring. To clarify the influence of environmental pressures on the life-history features of the Qinghai toad-headed lizard Phrynocephalus vlangalii along an altitudinal cline, we surveyed late pregnant females from 3 populations of low (2,600 m), middle (3,400 m), and high (3,600 m) elevations in the Dangjin Mountain of Gansu, China from July to October 2019, and compared their inter-population differences in maternal body size, reproductive characteristics, offspring growth, and locomotor performance. Because of lower temperatures, higher humidity, and lower light intensity caused by slope aspect and altitude, the middle-altitude region experienced stronger environmental stress than the high- and low-altitude regions. Our results showed that females were larger at middle- and high-altitude sites and smaller at the low-altitude site, following Bergmann's rule. We also found that females from low-altitude population gave birth earlier than those from the middle and high altitudes. Our results showed a shift in the offspring size-number trade-off of P. vlangalii in response to colder and harsher environments, with lizards from the alpine steppe (i.e. the middle- and high-altitude habitats) producing fewer but larger offspring than those from the warm steppe (i.e. the low-altitude habitat). Low-altitude juveniles grew faster than high-altitude ones, but at the same rates as middle-altitude juveniles. This result demonstrates that the growth of P. vlangalii was associated with temperature and light intensity. Our findings contribute to enhancing our understanding of the altitudinal variation in life-history features of plateau ectotherms and their phenotypic plasticity or local adaptation.

Oxidative potential and hydroxyl radical generation capacity of ambient PM2.5 over a high-altitude site in northeastern Himalaya: Role of long-range transport

This study investigates the dithiothreitol (DTT)-based oxidative potential (OP) and corresponding hydroxyl radical (•OH) generations capacity of PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5 μm) over a high-altitude site, Shillong (25.7 °N, 91.9 °E; 1064 m above mean sea level), located in the northeastern Himalaya. Measured OP and •OH are reported in two units: per m3 of filtered air (OPV and OHV) or per unit mass of PM2.5 in μg (OPM and OHM). Based on the characteristic ratios of chemical species in different sources, PM2.5 were classified into three source categories: Biomass Burning (BB) (N = 10), Secondary Organic Aerosols (SOA) (N = 12), and Mixed (N = 12). Consistently higher OP and •OH generation per m3 of air (OPV: 6.2 ± 1.0 (average ± SD, 1σ) nmol DTT min−1 m−3, and OHV: 1.2 ± 0.31 nmol •OH m−3) in all BB-dominated PM2.5 samples indicate relatively hazardous exposure dose from BB emissions among all sources. Characteristic OC/EC, WSOC/OC, and nss-K+/EC ratios evoked that SOA from biogenic precursors was a significant source for the observed OP and •OH in SOA-categorized samples. Distinctly different chemical composition of PM2.5 over Shillong (about 55% composed of organic matter) makes it relatively more (2–4 times) intrinsically redox-active compare to a reported study over another high-altitude site in a semi-arid region of India. Despite ∼1.7 times lower PM2.5 mass over Shillong (characterized by more aged PM2.5) compare to Patiala (30.3°N, 76.4°E; 250m amsl, a semi-urban city, characterized by fresher PM2.5 from mixed sources), the observed OPV over Shillong was about 1.2 times higher, and the OPM was about 2 times higher. It is attributed to the effect of atmospheric processing on particle's redox-activity. While examining the relationship of OPV and OHV with chemical species, it was observed that •OH generation capacity was more influenced by WSOC species' origin (primary or secondary) compare to DTT consumption. Such an observation restricts the practicality of particle-induced OP to be considered as the only metric for aerosol particle toxicity, and suggests also to consider simultaneous measurements of •OH generations. For the BB-dominated category, OC-normalized OP (OPOC) was correlated strongly with the fractions of N-containing water-soluble organic aerosols (i.e., a fraction of WSON and a fraction of familyCHO1N). Corresponding OC/EC, nss-K+/EC and nss-SO42−/EC ratios hint that coal combustion, in addition to BB, could be a significant source of redox-active WSON species in these samples. Such studies are important for identifying redox-active aerosol species and developing appropriate mitigation policies for healthy air.

Status, distribution and aspects of ecology of monal (Lophorus impeyanus) in Garhwal Himalayas, Uttarakhand, India

The Himalayan Monal (Lophophorus impejanus), state bird of Uttarakhand state is also the national bird of Nepal. The bird is of conservation priority species due to the nine coloured bird is distributed throughout the higher altitude of Himalayas and due to the bright coloured feather, they have been exploited for the feather as well as for the meat purposes. This species conservation priority species in its entire range because of its declining population due to anthropogenic threats. This bird is facing greatest threat of extinction due to poaching and habitat degradation. Out of the 17 species of Pheasant that occur in India are protected from capture by national and international legislation. Due to decrease in population they have been recognised as Schedule I species of Wildlife Protection Act (1972). However, it is highly desirable that status, distribution, and threats to conservation of monal pheasant should be given due importance. To understand the status distribution and habitat preference of the monal an intensive study was carried out. Surveys were conducted at 6 high altitude sites in Garhwal Himalayas including Kedarnath Wildlife sanctuary and the Nanda Devi Biosphere Reserve, between the altitudinal range from 2500m to 4000m a.s.l. The direct as well indirect methods were used and found that the number of faecal group was found to be maximum in Himtoli (2.64±2.2) followed by Madh Maheshwer (0.96±1.29), Saukhark (0.75±1.4). For the direct sighting the maximum number of monal were sighted in Tungnath (0.26±0.59), followed by Bansinarayan (0.14±.43), Madh Maheshwer (0.14±0.44). No direct sightings were recoded from Himtoli. Due to illegal poaching and habitat destruction the population of monal pheasant has declined and now confined to a few small fragmented patches and needs urgent attention for the conservation.

Long-Term Trends in Black Carbon and Aerosol Optical Depth Over the Central Himalayas: Potential Causes and Implications

Continuous ground-based observations of aerosols over the Himalayan region are highly beneficial in studying aerosol trends over the complex geographic terrain. This study presents the results from continuous long-term observations (2004–2016) of aerosols over a high-altitude site in the central Himalayas – Nainital, quantifying multihued aspects of black carbon (BC) and columnar aerosol optical depth (AOD). The results reveal that BC and AOD have a positive trend of 23.04 ± 3.00 ng m−3 year−1 and 0.0076 ± 0.0003 year−1, respectively. Simultaneously, a positive trend of 0.0066 ± 0.0059 year−1 is observed in the Angstrom exponent, thus indicating an increase in anthropogenic aerosols. The satellite observations covering a broader region around Nainital also depicted increasing trends in AOD (0.0042–0.0074 year−1), absorbing aerosol optical depth (0.0001 ± 0.0001 year−1) and aerosol index (0.0131 ± 0.0019 year−1), along with a slight decline in single scattering albedo (−0.0004 year−1). These results suggest that aerosols of absorbing nature might have increased over this region in recent times. Investigation of the AOD ratio, obtained from aerosol vertical profiles, revealed an increasing trend in aerosol load below 1 km. The observed trends in aerosols are found to be associated with enhanced biomass burning activity, reflected in terms of the positive trend in fire count ∼38.65 ± 5.88 year−1 over the region.

Characteristics of rain events of different durations at a high-altitude site in the Western Ghats of India

Characteristics of rain events of different durations at a high-altitude site in the Western Ghats of India

Snow albedo and its sensitivity to changes in deposited light-absorbing particles estimated from ambient temperature and snow depth observations at a high-altitude site in the Himalaya

Snow darkening by deposited light-absorbing particles (LAP) accelerates snowmelt and shifts the snow melt-out date (MOD). Here, we present a simple approach to estimate the snow albedo variability due to LAP deposition and test this method with data for 2 seasons (February–May 2016 and December 2016–June 2017) at a high-altitude valley site in the Central Himalayas, India. We derive a parameterization for the snow albedo that only depends on the daily observations of average ambient temperature and change in snow depth, as well as an assumed average concentration of LAP in snow precipitation. Linear regression between observed and parameterized albedo for the base case assuming an equivalent elemental carbon concentration [ECeq] of 100 ng g–1 in snow precipitation yields a slope of 0.75 and a Pearson correlation coefficient r2 of 0.76. However, comparing the integrated amount of shortwave radiation absorbed during the winter season using observed albedo versus base case albedo resulted in rather small differences of 11% and 4% at the end of Seasons 1 and 2, respectively. The enhanced energy absorbed due to LAP at the end of the 2 seasons for the base case scenario (assuming an [ECeq] of 100 ng g–1 in snow precipitation) was 40% and 36% compared to pristine snow. A numerical evaluation with different assumed [ECeq] in snow precipitation suggests that the relative sensitivity of snow albedo to changes in [ECeq] remains rather constant for the 2 seasons. Doubling [ECeq] augments the absorption by less than 20%, highlighting that the impact on a MOD is small even for a doubling of average LAP in snow precipitation.

Tree Regeneration and Vegetation Structure in High Altitudes of Uttarakhand Himalaya, India

The present paper is unique because of the use of modern statistical techniques to assess the species composition,distribution, and regeneration pattern at high altitude Himalayas. Threats to the forest community were alsoassessed at different survey sites. Stratified random sampling was carried out at 13 high altitude sites ofUttarakhand, from east to west at altitudinal range from 2500m to 4000m a.s.l., irrespective of protected areas.The tree species density was found maximum at Saukherk (665.5±192.3) followed by Mulakherk (586.2+367.7).A total of 16 regenerating tree species were recorded from 13 surveyed sites. The densities of regeneration treespecies were low at all the surveyed sites especially towards the glacier; however, saplings were recorded maximumat Hitoli (5176.2±3690.4). PCA was performed to understand the patterns of relationship among various surveyedsites at the landscape level. The tree cover, density, diversity, and richness play a powerful role in discriminatingthe sites at PC I while the second PC is a gradient of grass and disturbances. The high altitude Himalayas havethe anthropoegenic pressure due to tree cutting, lopping, cattle grazing etc. The mean tree cutting, lopping, cattledung, grazing, and impact of the fire were assessed at different surveyed sites and threat scores were calculated.The Saukherk, Dungiadong are the least threatened sites while the Liwari, Mulakherk and Hitoli are the mostthreatened sites.