Mountain Site Research Articles

Gentiana asclepiadea L. from Two High Mountainous Habitats: Inter- and Intrapopulation Variability Based on Species' Phytochemistry.

Natural populations of Gentiana asclepiadea L., located at two mountainous sites, were HPLC-analyzed regarding the contents of six representative secondary metabolites. The contents of swertiamarin (SWM), gentiopicrin (GP), sweroside (SWZ), mangiferin (MGF), isoorientin (ISOOR), and isovitexin (ISOV) were determined in six populations (three per study site), and separately for aboveground and belowground plant parts. PCA showed a clear separation of four groups according to the contents of the analyzed secondary metabolites. Out of six analyzed compounds, five were present in all samples and only one (SWZ) was found in Golija populations (belowground parts) but not in Vlasina populations, and its presence can be indicative of the geolocation of populations. Clear separation of groups was mostly affected by the different contents of chemical compounds in plant parts (aboveground versus belowground) and by the differences related to population origin (higher content of SWM and GP in belowground parts of individuals from Vlasina populations and higher content of MGF and ISOOR of individuals from Golija populations). The results of this study contribute to the spatiochemical profiling of G. asclepiadea populations and a better understanding of inter- and intrapopulation variability of pharmacologically important compounds.

Effects of topographic factors on distribution of cacti along an elevation gradient in Brazilian Caatinga

Abstract The Cactacea family comprises 128 genera and 1450 species with predominantly neotropical distribution. Cacti are commonly found in arid and semi-arid regions and have great ecological relevance due to their interactions with animals and other groups of plants. Abiotic interactions, such as topography, altitude, rainfall, temperature and soils, also influence the composition and distribution of cacti. The objective of the present study was to assess patterns of species composition and distribution for cacti along an elevation gradient in Brazilian Caatinga vegetation. Four transects (composed by 25 plots of 100 m² each) were established at each of two mountain sites. The topographic variables of elevation, slope, rockiness and soil depth were evaluated to determine if they affect the distribution of richness and abundance of cacti along the elevation gradient using Spearman's (rs) correlation coefficient. A total of 554 individuals of five cacti species (Pilosocereus gounellei, Pilosocereus pachycladus, Tacinga palmadora, Tacinga inamoena and Melocactus zehntneri) were sampled. Cacti richness and abundance were found to be negatively correlated with elevation, slope and rockiness, and positively correlated with soil depth (p<0.05). All species exhibited aggregate spatial distribution patterns, which may be related to different environmental conditions produced by interactions among topographic variables (slopes, rockiness and soil depth), that synergistically influence the patterns of species richness and abundance along the elevation gradient.

How much survey effort is required to assess bird assemblages in fire-prone eucalypt forests using acoustic recorders?

Abstract Context Forest fire activity is expected to increase in many parts of the globe over the course of the 21st century, with corresponding potential for heightened levels of proximate and ultimate threats to avian diversity. Landscape-scale investigations of the responses of birds in locations where current extreme fire regimes represent those expected in the future provide opportunities to identify potentially vulnerable species in advance. Autonomous acoustic recorders are well suited to survey birds in the typically large and remote natural areas with low accessibility required for these types of studies, because they offer cost-effective and relatively safe options for obtaining reliable data. Aims The present study aimed to optimise survey using acoustic recorders to achieve a satisfactory assessment of montane dry sclerophyll forest bird assemblages using these devices. Survey completeness, or the number of species detected as a percentage of total species, was used as a metric to gauge survey suitability. Methods Acoustic recorders were deployed in 10 ridge-top forest sites in the Blue Mountains, south-eastern Australia. Extensive field recordings were processed by an analyst, with species detected by their calls recorded in a series of 20-min samples. A results-based approach, incorporating a stopping rule that established when to conclude sampling at a site, was applied to the data. The results guided the target survey completeness and sampling effort levels assigned to a set of fixed-effort survey methods, which were subsequently evaluated. Key results The optimal survey method involved using recordings from five 20-min sampling periods immediately following dawn for 2 days, achieving an average survey completeness level of 69%. Conclusions The optimal survey method can obtain results that are suitable for many types of studies involving assessments of bird assemblages, because the method can detect all common and moderately common species in assemblages, plus a fair proportion of rare species. Implications The present study has systematically developed an effective method of using autonomous acoustic recorders to research and monitor montane bird assemblages in fire-prone dry sclerophyll forests. This methodological approach may also be applied in systems subject to altered patterns of flood, storm or other extreme weather under climate change.

Failures and Reliability in Hawts Operating in Mountainous Areas, Open Sea and in Harsch Climate Sites

Recently, offshore wind plants, as Horn’s Riv one, have reached a remarkable interest and development. In these sites, HAWT’s blades experiment corrosion, erosion and fouling and, at higher latitudes, icing conditions too, as in mountainous areas and in harsch climate sites. The operative conditions may influence the machine damages and they may occur as consequence of erosion, corrosion, fouling, icing, exfoliation caused by the above mentioned environmental conditions. The paper reports about data collection about failures occurred to HAWTS operating in offshore, mountainous and harsch climate sites in last ten years. Particularly, the damage occurred to blades, gears and bearings have been examined and the consequences analysed. The occurred failures are examined and the reliability of WTGs is assessed by appropriate models and analysis. The results are com pared to literature data and they may be very useful in programmable maintenance and in predictable one. Reliability analysis may be also useful to increase energy production.

Modern Data on the Bronze Age Radiocarbon Chronology in the Minusinsk Basins

In 2009, the first radiocarbon chronology of the Bronze Age and Scythian period of the Minusinsk Basins was published, which laid foundation for a system analysis of further results. Over the past decade, the total number of radiocarbon definitions has further increased by almost a quarter. The most important changes have affected the chronological frames of Afanasyeva Culture. A vast series of new AMS dates obtained from the Altai Mountains sites showed that a significant number of the earlier age estimates erroneously suggested the sites to be considerably older. This phenomenon probably affected the Minusinsk Basins as well. The new dates shifted the boundaries of the Afanasyeva Culture in the Middle Yenisei Region to the 30th–25th c. BC, and the timing of the earliest Okunev Culture burials to the end of the 26th c. BC rather than the beginning of the 25th c. BC. This suggests a 100-year period of coexistence of the Afanasyeva and Okunev Cultures. Moreover, the new dates filled the “hiatus” between the end of the Okunev and beginning of the Andronovo Culture, discussed in 2009. The end of the Okunev can now be attributed to the 17th c. BC. The new dates fully confirm the narrow chronology of the Andronovo (Fedorov) Culture on the Middle Yenisei — 17th–15th c. BC. Minor changes are seen at the beginning of the Late Bronze Age in the Minusinsk Basins, previously called the Karasuk Culture. The new determinations suggest the end of the 15th c. BC as the beginning of this period, which is somewhat older than previously thought. The end of the Bronze Age is still dated to the end of the 9th c. BC.

Validation of the TROPOspheric Monitoring Instrument (TROPOMI) surface UV radiation product

Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite was launched on 13 October 2017 to provide the atmospheric composition for atmosphere and climate research. The S5P is a Sun-synchronous polar-orbiting satellite providing global daily coverage. The TROPOMI swath is 2600 km wide, and the ground resolution for most data products is 7.2×3.5 km2 (5.6×3.5 km2 since 6 August 2019) at nadir. The Finnish Meteorological Institute (FMI) is responsible for the development of the TROPOMI UV algorithm and the processing of the TROPOMI surface ultraviolet (UV) radiation product which includes 36 UV parameters in total. Ground-based data from 25 sites located in arctic, subarctic, temperate, equatorial and Antarctic areas were used for validation of the TROPOMI overpass irradiance at 305, 310, 324 and 380 nm, overpass erythemally weighted dose rate/UV index, and erythemally weighted daily dose for the period from 1 January 2018 to 31 August 2019. The validation results showed that for most sites 60 %–80 % of TROPOMI data was within ±20 % of ground-based data for snow-free surface conditions. The median relative differences to ground-based measurements of TROPOMI snow-free surface daily doses were within ±10 % and ±5 % at two-thirds and at half of the sites, respectively. At several sites more than 90 % of cloud-free TROPOMI data was within ±20 % of ground-based measurements. Generally median relative differences between TROPOMI data and ground-based measurements were a little biased towards negative values (i.e. satellite data < ground-based measurement), but at high latitudes where non-homogeneous topography and albedo or snow conditions occurred, the negative bias was exceptionally high: from −30 % to −65 %. Positive biases of 10 %–15 % were also found for mountainous sites due to challenging topography. The TROPOMI surface UV radiation product includes quality flags to detect increased uncertainties in the data due to heterogeneous surface albedo and rough terrain, which can be used to filter the data retrieved under challenging conditions.

Holocene Paleoseismology of the Steamboat Mountain Site: Evidence for Full-Length Rupture of the Teton Fault, Wyoming

ABSTRACT The 72-km-long Teton fault in northwestern Wyoming is an ideal candidate for reconstructing the lateral extent of surface-rupturing earthquakes and testing models of normal-fault segmentation. To explore the history of earthquakes on the northern Teton fault, we hand-excavated two trenches at the Steamboat Mountain site, where the east-dipping Teton fault has vertically displaced west-sloping alluvial-fan surfaces. The trenches exposed glaciofluvial, alluvial-fan, and scarp-derived colluvial sediments and stratigraphic and structural evidence of two surface-rupturing earthquakes (SM1 and SM2). A Bayesian geochronologic model for the site includes three optically stimulated luminescence ages (∼12–17 ka) for the glaciofluvial units and 16 radiocarbon ages (∼1.2–8.6 ka) for the alluvial-fan and colluvial units and constrains SM1 and SM2 to 5.5±0.2 ka, 1σ (5.2–5.9 ka, 95%) and 9.7±0.9 ka, 1σ (8.5–11.5 ka, 95%), respectively. Structural, stratigraphic, and geomorphic relations yield vertical displacements for SM1 (2.0±0.6 m, 1σ) and SM2 (2.0±1.0 m, 1σ). The Steamboat Mountain paleoseismic chronology overlaps temporally with earthquakes interpreted from previous terrestrial and lacustrine paleoseismic data along the fault. Integrating these data, we infer that the youngest Teton fault rupture occurred at ∼5.3 ka, generated 1.7±1.0 m, 1σ of vertical displacement along 51–70 km of the fault, and had a moment magnitude (Mw) of ∼7.0–7.2. This rupture was apparently unimpeded by structural complexities along the Teton fault. The integrated chronology permits a previous full-length rupture at ∼10 ka and possible partial ruptures of the fault at ∼8–9 ka. To reconcile conflicting terrestrial and lacustrine paleoseismic data, we propose a hypothesis of alternating full- and partial-length ruptures of the Teton fault, including Mw∼6.5–7.2 earthquakes every ∼1.2 ky. Additional paleoseismic data for the northern and central sections of the fault would serve to test this bimodal rupture hypothesis.

Evaluation of Phase Discrimination Methods and Snow Fraction Perturbations in Arid Regions of Northwest China

AbstractSnow fraction has a direct impact on water resources in arid regions. The selection of proper methods for estimating snow fraction is thus essential. Two temperature-based and two humidity-based approaches to discriminate precipitation phase were evaluated using daily meteorological observations over the past six decades in Xinjiang in arid northwest China. The main findings included that 1) the finest discrimination was achieved by the wet-bulb temperature (Tw) method whereas the single temperature threshold at 0°C produces the poorest result; the performances of the Dai and humidity-dependent empirical method (TRH) methods were between them, with slightly lower error using the Dai method. Also, the Tw method is the least sensitive to regional heterogeneity and less affected by distinct changes in elevation; the other three methods, however, are biased mostly toward underestimating snow and show larger variations due to the regional discrepancies. Careful adjustment of snow discrimination thresholds based on the local properties of observation spots is needed for these methods. 2) Despite widespread warming, snow fraction perturbations in Xinjiang are characterized mainly by insignificant changes plus pronounced reductions at high mountain sites. Proxy drivers of such changes can be better explained by considering the hydrothermal diversity and changing climatic factors. Across the wetter subregions, snowfall has been significantly increasing, and the positive impact of which on snow fraction was hindered by significant warming, particularly in winter, and summer rainfall; across the drier subregions, however, insignificant change in snow fraction corresponds to a slow and insignificant increase in snowfall joined by the negative impacts of significant winter warming and summer rainfall.

Plant and Soil Drivers of Whole-Plant Microbiomes: Variation in Switchgrass Fungi from Coastal to Mountain Sites

Plant-associated microbial diversity is regulated by dispersal from local and regional species pools, as well as filtering by the environment and plant host. However, few studies have simultaneously examined microbial community variation in multiple plant-associated habitats across multiple sites; thus, it is unclear what scales and filters are most important in shaping whole-plant microbiome diversity. To address this, we characterized fungal communities associated with switchgrass (Panicum virgatum L.) leaves, roots, and soils within and across 14 stands spanning mountain to coastal ecoregions of North Carolina. Niche differences at small scales (i.e., less than half a kilometer) best explained variation in fungal communities. However, the specific environmental drivers of fungal community composition differed for leaves, roots, and soils. Leaf and root fungi were both affected by plant height, whereas soil fungi were controlled by stand age. Different soil properties were important for fungi in all plant-associated habitats: K, P, and pH for leaves; clay, Mn, and pH for roots; and clay, dissolved organic carbon, total inorganic N, and Cu for soils. Climate and spatial variables were not significant, further supporting the key role of plant and soil properties. Advances such as these will help us explain, predict, and manipulate microbial assemblages that support plant growth in managed and natural systems.

A high proportion of norway spruce in mixed stands increases probability of stand failure

Abstract The decline of pure spruce forests in the Beskydy Mountains in the Czech Republic and Slovakia is mainly driven by bark beetle attacks and storm events. Salvage-harvest records based on timber volume on the forest-stand level document the extent of stand failure processed by salvage logging. On the basis of these records, the stand failure proportion was expressed as the proportion of timber volume processed by salvage harvest divided by the standing timber volume over a period of 10 years (sf). Two null hypotheses to be tested are that sf is not influenced by (H1) the size of trees expressed by mean stand age (age) or alternatively by mean stand diameter (dbh); and (H2) the volume proportion of spruce within the stand (spp). The dataset was evaluated as a total and separately for the three site types, each for spruce, beech, fir, larch, pine, and other broadleaved species. The dataset was analysed using a binary logistic regression. The sf increased with age, dbh, and the spp. Pure spruce stands with high age and high dbh on mountain sites are associated with the highest sf. However, a slight admixture of 25% tree species other than spruce was shown to stabilise the stands significantly. Species other than spruce in a minor admixture to spruce stands were destabilised by the breakdown of spruce stands. For a realistic financial evaluation of forest-stand management, managers should consider the risk of stand failure, and reduce the risk by increasing species admixture in the spruce forest stands.

Standardization of complementary work time in timber harvesting processes

Abstract One of the essential elements of work technology assessment is task performance time. In the working day structure, production times are crucial; however, under certain conditions, complementary work times can have a share of up to 30%. Accurate determination of the time structure of a work shift is very time consuming and requires time measurements using the methods of cumulative timing or snapshot observations. For this reason, the overall share of complementary work times in a work shift is usually estimated roughly, equally for all timber harvesting conditions. The aim of this study was to determine the impact of selected working environment factors on the share of complementary work times in a work shift, in technologies on the manual-machine and the machine levels. The analyses were carried out in 33 forest districts of the Regional Directorate of State Forests in Wrocław. Among forest contractors, surveys were carried out to analyse the time structure of a working day. For each forest district, analyses of environmental factors potentially relevant to the share of complementary work times in a work shift were carried out; these included field features, dispersion of stands, features of timber, area accessibility. The total share of complementary work times in the machine-level technology variant amounted to approx. 40% and was higher than the manual-machine technological variant, where this share amounted to approx. 35%. The models developed for standardization of the share of variability of complementary work times, in the case of the manual-machine technology level, took into account the share of timber assortments with the length of over 2.5 m as well as the share of upland and mountain sites. In the case of timber harvesting at the machine technology level, the standardization model included as significant the factors such as the share of coniferous forest sites, the number of forest complexes with an area of over 100 hectares, and the total length of roads. Therefore, the above features could be selected as decisive for the share of the complementary work time category out of the full set of environmental variables taken into consideration in the estimation of the time-consumption of timber harvesting processes.

New particle formation at urban and high-altitude remote sites in the south-eastern Iberian Peninsula

Abstract. A substantial fraction of the atmospheric aerosols originates from secondary new particle formation (NPF), where atmospheric vapours are transformed into particles that subsequently grow to larger sizes, affecting human health and the climate. In this study, we investigate aerosol size distributions at two stations located close to each other (∼ 20 km) but at different altitudes: urban (UGR; 680 m a.s.l., metres above sea level) and high-altitude remote (SNS; 2500 m a.s.l.) sites, both in the area of Granada, Spain, and part of AGORA observatory (Andalusian Global ObseRvatory of the Atmosphere). The analysis shows a significant contribution of nucleation mode aerosol particles to the total aerosol number concentration at both sites, with a contribution of 47 % and 48 % at SNS and UGR, respectively. Due to the important contribution of NPF events to the total aerosol number concentrations and their high occurrence frequency (> 70 %) during the study period, a detailed analysis of NPF events is done in order to get insight into the possible mechanisms and processes involved in NPF events at these contrastive sites. At SNS, NPF is found to be associated with the transport of gaseous precursors from lower altitudes by orographic buoyant upward flows. NPF events at the SNS site are always observed from the smallest measured sizes of the aerosol size distribution (4 nm), implying that NPF takes place in or in the vicinity of the high-altitude SNS station rather than being transported from lower altitudes. Although NPF events at the mountain site seem to be connected with those occurring at the urban site, growth rates (GRs) at SNS are higher than those at the UGR site (GR7−25 of 6.9 and 4.5 nm h−1 and GR4−7 of 4.1 and 3.6 nm h−1 at SNS and UGR, respectively). This fact could have special importance for the production of cloud condensation nuclei (CCN) and therefore for cloud formations which may affect regional/global climate, since larger GRs at mountain sites could translate to a larger survival probability of NPF particles reaching CCN sizes, due to the shorter time period needed for the growth. The analysis of sulfuric acid (H2SO4) shows that the contribution of H2SO4 is able to explain a minimal fraction contribution to the observed GRs at both sites (< 1 % and < 10 % for the 7–25 and 4–7 nm size ranges, respectively), indicating that other condensing vapours are responsible for the majority of particle growth, as well as the differing growth rates between the two sites. Results also show that the condensation sink (CS) does not play a relevant role in NPF processes at both sites and points to the availability of volatile organic compounds (VOCs) as one of the main factors controlling the NPF events at both sites. Finally, a closer analysis of the NPF events that were observed at the SNS site during a Saharan dust episode that occurred during the field campaign was carried out, evidencing the role of TiO2 and F2O3 together with VOCs in promoting new particle formation during this dust intrusion event. Although further investigation is needed to improve our understanding in this topic, this result suggests that climate effects of mineral dust and NPF are not disconnected from each other as it was commonly thought. Therefore, since mineral dust contributes to a major fraction of the global aerosol mass load, dust–NPF interaction should be taken into account in global aerosol-climate modelling for better climate change prediction.

Spatio-Temporal Variation of Ozone Concentrations and Ozone Uptake Conditions in Forests in Western Germany

The study analyzes the long-term trends (1998–2019) of concentrations of the air pollutants ozone (O3) and nitrogen oxides (NOx) as well as meteorological conditions at forest sites in German midrange mountains to evaluate changes in O3 uptake conditions for trees over time at a plot scale. O3 concentrations did not show significant trends over the course of 22 years, unlike NO2 and NO, whose concentrations decreased significantly since the end of the 1990s. Temporal analyses of meteorological parameters found increasing global radiation at all sites and decreasing precipitation, vapor pressure deficit (VPD), and wind speed at most sites (temperature did not show any trend). A principal component analysis revealed strong correlations between O3 concentrations and global radiation, VPD, and temperature. Examination of the atmospheric water balance, a key parameter for O3 uptake, identified some unusually hot and dry years (2003, 2011, 2018, and 2019). With the help of a soil water model, periods of plant water stress were detected. These periods were often in synchrony with periods of elevated daytime O3 concentrations and usually occurred in mid and late summer, but occasionally also in spring and early summer. This suggests that drought protects forests against O3 uptake and that, in humid years with moderate O3 concentrations, the O3 flux was higher than in dry years with higher O3 concentrations.

Extending Limited In Situ Mountain Weather Observations to the Baseline Climate: A True Verification Case Study

The availability of in situ atmospheric observations decreases with elevation and topographic complexity. Data sets based on numerical atmospheric modeling, such as reanalysis data sets, represent an alternative source of information, but they often suffer from inaccuracies, e.g., due to insufficient spatial resolution. sDoG (statistical Downscaling for Glacierized mountain environments) is a reanalysis data postprocessing tool designed to extend short-term weather station data from high mountain sites to the baseline climate. In this study, sDoG is applied to ERA-Interim predictors to produce a retrospective forecast of daily air temperature at the Vernagtbach climate monitoring site (2640 MSL) in the Central European Alps. First, sDoG is trained and cross-validated using observations from 2002 to 2012 (cross-validation period). Then, the sDoG retrospective forecast and its cross-validation-based uncertainty estimates are evaluated for the period 1979–2001 (hereafter referred to as the true evaluation period). We demonstrate the ability of sDoG to model air temperature in the true evaluation period for different temporal scales: day-to-day variations, year-to-year and season-to-season variations, and the 23-year mean seasonal cycle. sDoG adds significant value over a selection of reference data sets available for the site at different spatial resolutions, including state-of-the-art global and regional reanalysis data sets, output by a regional climate model, and an observation-based gridded product. However, we identify limitations of sDoG in modeling summer air temperature variations particularly evident in the first part of the true evaluation period. This is most probably related to changes of the microclimate around the Vernagtbach climate monitoring site that violate the stationarity assumption underlying sDoG. When comparing the performance of the considered reference data sets, we cannot demonstrate added value of the higher resolution data sets over the data sets with lower spatial resolution. For example, the global reanalyses ERA5 (31 km resolution) and ERA-Interim (80 km resolution) both clearly outperform the higher resolution data sets ERA5-Land (9 km resolution), UERRA HARMONIE (11 km resolution), and UERRA MESCAN-SURFEX (5.5 km resolution). Performance differences among ERA5 and ERA-Interim, by contrast, are comparably small. Our study highlights the importance of station-scale uncertainty assessments of atmospheric numerical model output and downscaling products for high mountain areas both for data users and model developers.

Activation properties of aerosol particles as cloud condensation nuclei at urban and high-altitude remote sites in southern Europe

Understanding the activation properties of aerosol particles as cloud condensation nuclei (CCN) is important for the climate and hydrological cycle, but their properties are not fully understood. In this study, the CCN activation properties of aerosols are investigated at two different sites in southern Spain: an urban background station in Granada and a high altitude mountain station in the Sierra Nevada National Park, with a horizontal separation of 21 km and vertical separation of 1820 m.CCN activity at the urban environment is driven by primary sources, mainly road traffic. Maximum CCN concentrations occurred during traffic rush hours, although this is also when the activation fraction is lowest. This is due to the characteristics of the rush hour aerosol consisting of ultrafine and less hygroscopic particles. In contrast, the mountain site exhibited larger and more hygroscopic particles, with CCN activity driven by the joint effect of new particle formation (NPF) and vertical transport of anthropogenic particles from Granada urban area by orographic buoyant upward flow. This led to the maximum concentrations of CCN and aerosol particles occurring at midday at the mountain site. Clear differences in the diurnal evolution of CCN between NPF events and non-event days were observed at the Sierra Nevada station, demonstrating the large contribution of NPF to CCN concentrations, especially at high supersaturations. The isolated contribution of NPF to CCN concentration has been estimated to be 175% higher at SS = 0.5% relative to what it would be without NPF. We conclude that NPF could be the major source of CCN at this mountain site.Finally, two empirical models were used to parameterize CCN concentration in terms of aerosol optical or physical parameters. The models can explain measurements satisfactorily at the urban station. At the mountain site both models cannot reproduce satisfactorily the observations at low SS.

A Hybrid Data Balancing Method for Classification of Imbalanced Training Data within Google Earth Engine: Case Studies from Mountainous Regions

Distribution of Land Cover (LC) classes is mostly imbalanced with some majority LC classes dominating against minority classes in mountainous areas. Although standard Machine Learning (ML) classifiers can achieve high accuracies for majority classes, they largely fail to provide reasonable accuracies for minority classes. This is mainly due to the class imbalance problem. In this study, a hybrid data balancing method, called the Partial Random Over-Sampling and Random Under-Sampling (PROSRUS), was proposed to resolve the class imbalance issue. Unlike most data balancing techniques which seek to fully balance datasets, PROSRUS uses a partial balancing approach with hundreds of fractions for majority and minority classes to balance datasets. For this, time-series of Landsat-8 and SRTM topographic data along with various spectral indices and topographic data were used over three mountainous sites within the Google Earth Engine (GEE) cloud platform. It was observed that PROSRUS had better performance than several other balancing methods and increased the accuracy of minority classes without a reduction in overall classification accuracy. Furthermore, adopting complementary information, particularly topographic data, considerably increased the accuracy of minority classes in mountainous areas. Finally, the obtained results from PROSRUS indicated that every imbalanced dataset requires a specific fraction(s) for addressing the class imbalance problem, because different datasets contain various characteristics.

Physiochemistry characteristics and sources of submicron aerosols at the background area of North China Plain: Implication of air pollution control in heating season

Aerosol physiochemistry and sources in the background regions of North China Plain (NCP) remains poorly characterized. Here we present a comprehensive characterization of aerosol composition and sources at an NCP mountain site during heating periods (November 12 to December 24, 2018) using a Quadrupole Aerosol Mass Spectrometer (Q-AMS). The average mass concentration of non-refractory submicron aerosols (NR-PM1) was 22.6 ± 29.9 μg/m3, in which organic aerosol (OA) and nitrate showed comparable contribution of 32.8% and 35.1%, respectively, followed by ammonium (15.3%), sulfate (13.9%) and chloride (2.6%). Secondary inorganic aerosol (SIA) was found to dominated in polluted days (70%) which the aerosol level is 15 times higher than that in clean days which dominated by organics (54%). In addition, organics, nitrate and sulfate showed similar unimodal size distributions peaked at 600–800 nm in polluted days, which appear to be internally mixed that originated from regional transportation of aged aerosol. Whereas, the different size distribution mode of organics with SIA that peaked at smaller particle size (200–300 nm) in cleans days suggested contributions from local emissions. Positive matrix factorization (PMF) and ME2 analysis showed oxidized organic aerosols (OOA) dominated the total OA (64%), while the contribution of the hydrocarbons-like OA (HOA) and biomass burning OA (BBOA) was comparable (15–21%). To evaluate the effect of air pollution control on the background aerosols chemistry, interannual variations in aerosol chemical compositions during heating periods in 2014–2018 were deduced combined with the trajectory cluster analysis. The results showed the aerosol source region was mainly from the urban agglomeration of NCP, which showed the largest decrease in aerosol mass concentration during the past five years. In addition, the aerosol compositions became to be SIA dominated gradually under different air mass influence condition, suggesting the air pollution control is more effective for the reduction of primary emissions than the secondary species.

Symbolic seasonal variation newly found in atmospheric ammonia concentration in urban area of Japan

The NH3(g) concentration measured at multi-site network in Kobe and Kitakyushu, Japan by using passive method continuously for one year in the late 2000s (September 2008–August 2009) and March 2018–February 2019, respectively, was statistically analyzed from the viewpoint of its controlling factors for temporal variation and spatial distribution. Nine survey sites were established in a region of Kobe, where highly urbanized, agricultural and mountainous areas were located within a 20-km x 20-km region; and one site in Kitakyushu, considered as urbanized and industrialized area, was taken into account. In terms of temporal variation, in both areas of Kobe and Kitakyushu, the NH3(g) concentration indicated lower level in the summer than those in other seasons and experienced higher concentration in colder period, which was newly found compared with the conventional wisdom and results in former studies. Regarding spatial distribution, the NH3(g) concentration showed large variations depending on the site, and the annual mean NH3(g) concentration ranged from 0 ppb (not detected: N.D.) to around 5 ppb. The NH3(g) concentration at the mountainous site with high elevation was the lowest, while it was the highest at the site where the contribution of agriculture was noticeably large in the NH3 inventory, followed by commercial and residential areas. The meteorological factors significantly contributed to the specific seasonal variation; moreover, multiple factors such as located situation, acid-base balance in the atmospheric reaction and vehicular emission were mutually related and presumably responsible for the seasonality of higher in the colder season and lower in the warmer season. When the NH3(g) concentration in the urbanized area is discussed, as in our present study area, the proportion of humans and pets (Human&Pet) to the total in the NH3 inventory could be a good parameter to account for the NH3(g) concentration.

Gaseous Oxidized mercury dry deposition measurements in the Four Corners area, U.S.A., after large power plant mercury emission reductions

Gaseous oxidized mercury (GOM) dry deposition measurements using surrogate surface passive samplers were collected at six sites in the Four Corners area, U.S.A., for the two-year period August 2017–August 2019, after the implementation of large power plant mercury emission reductions across the U.S.A. Two-year baseline GOM dry deposition measurements at the same six sites in the Four Corners area, taken before the implementation of U.S.A. power plant mercury control regulations, were conducted earlier from August 2009–August 2011. The GOM dry deposition rate estimate decreased at the Four Corners area high elevation remote mountain site of Molas Pass, Colorado (3249 m asl) from 0.4 ng/m2h for August 2009–August 2011 to 0.3 ng/m2h for August 2017–August 2019. In contrast, GOM dry deposition rate estimates for the remaining five sites increased for August 2017–August 2019, ranging from 0.8 to 1.3 ng/m2h, up from the August 2009–August 2011 range of 0.6–1.0 ng/m2h. Comparisons of median GOM dry deposition values showed a statistically significant decrease of 17 ng/m2 at the Molas Pass site between August 2009–August 2011 and August 2017–August 2019, and a statistically significant increase of 66 ng/m2 and 64 ng/m2, respectively, at the Mesa Verde National Park and Farmington Substation sites between August 2009–August 2011 and August 2017–August 2019. For the four years of GOM dry deposition data collected in the Four Corners area annual GOM dry deposition levels ranged from 2237 ng/m2yr (at the Molas Pass high elevation remote mountain site) to 11542 ng/m2yr (at the Mesa Verde National Park site), and the estimates were generally higher in magnitude in the spring and summer compared to the fall and winter. In light of the unexpected increases in GOM dry deposition rates at the non-remote sites, it is suggested that large regional wildfires and local anthropogenic mercury emission sources from cities and oil/gas production areas are possible notable contributors to the GOM dry deposition measurements collected in the Four Corners area.

Recent decline of high altitude coniferous growth due to thermo-hydraulic constrains: evidence from the Miyaluo Forest Reserve, Western Sichuan Plateau of China

Tree growth decline has been reported in many places around the globe under the context of increasingly warming climate, and strengthening drought intensity is detected to be the primary factor for such decline, particularly in northern forest sites, as well as arid and semi-arid areas. Yet, the forest growth decline in high altitude, high mountain sites certainly merits investigation. Here, we reported faxon fir (Abies fargesii var. faxoniana) forest growth decline (slope = -0.64) at the tree line (4150 m above sea level) in Miyaluo Forest Reserve (MFR) at the Western Sichuan Plateau, southwestern China since 2000. We investigated the cause of tree growth decline by applying dendrochronological approaches. We took tree-ring samples from fir trees at the tree line and developed tree-ring width (TRW) chronology. The tree growth – climate relationship analysis showed that maximum temperature (Tmax) was the primary factor limiting the radial growth of fir trees in the investigated area. The moving correlation analysis indicated the strengthening positive influence of Tmax, spring precipitation, and cloud cover during winter and monsoon period on radial growth since 2000s. Our results have shown that both thermal and hydraulic constrains accounted for the radial growth decline of fir trees at the tree line of MFR in the western Sichuan Plateau.