Rise In Altitude Research Articles

Comparison of Three Remote Sensing Indices in Revealing the Vegetation Growth Dynamics in Nepal from 2000 to 2020

Remote sensing indices have been widely used to monitor the vegetation growth dynamics induced by climate change and human activities, and yet the consistency of the vegetation dynamics revealed by different remote sensing indices in mountains is unclear. Using Nepal as a case study, this study explored the spatial-termporal consistencies of the three widely-used remote sensing indices （i.e., normalized difference vegetation index （NDVI）, leaf area index （LAI）, and net primary production （NPP）） in quantifying the vegetation growth dynamics in mountainous regions. The results indicated that the spatial distributions of the multi-year mean estimates varied greatly by remote sensing index, especially in the low-altitude regions. The maximum NDVI, LAI, and NPP occurred in the low, medium, and high mountain regions, respectively. Although all three indices showed an overall increasing tendency from a long-term perspective, the area percentage of the lands with a significant trend was obviously larger in NDVI （82%） than that in NPP （58%） and LAI （56%）. In addition, the land area percentages with vegetation growth enhancement decreased gradually by the rise of altitude for both the NDVI and LAI indices but decreased after an increase for the NPP index. Only 9.6% of the lands showed consistent long-term trends （with the same change directions and significant levels） in the three indices on a per-pixel basis. Our findings highlight the large uncertainties of remote sensing indices in monitoring vegetation growth dynamics in mountainous areas, and the importance of developing reinforced remote sensing products in future efforts.

Three-dimensional numerical simulation and experimental validation of airborne ground-penetrating radar based on CNCS-FDTD method under undulating terrain conditions

Traditional Finite Difference Time Domain (FDTD) approaches face challenges with increased computational demands and errors as terrain complexity and flight altitude rising. This study introduces the Crank-Nicolson-Cycle-Sweep-FDTD (CNCS-FDTD) method, enhancing airborne ground penetrating radar (GPR) simulations over undulating terrains. CNCS-FDTD, as an unconditionally stable implicit algorithm, overcomes these by allowing larger time steps without the constraints of the Courant-Friedrichs-Lewy (CFL) condition. Our research aims to assess how CNCS-FDTD can improve computational efficiency and accuracy in modeling airborne GPR responses across varied terrains. Initial simulations using a three-dimensional graben model indicate that CNCS-FDTD can maintain calculation stability with significantly larger time steps, reducing computational time by 42%. To further verify the reliability of the numerical simulation results, the paper also presents experimental tests of the undulating terrain model. By comparing the numerical and physical simulation results of models under different flight altitudes and terrain conditions, the accuracy of the simulation results is validated.

Understory vegetation diversity patterns of Platycladus orientalis and Pinus elliottii communities in Central and Southern China.

As a vital component of arbor forests, understory vegetation serves as an essential buffer zone for storing carbon due to its strong capacity for community regeneration. This study aimed to identify the diversity pattern and construction mechanism of Platycladus orientalis and Pinus elliottii understory vegetation based on large-scale sample surveys. The Bayesian Information Criterion value of species abundance distribution (SAD) indicated that the Zipf and Zipf-Mandelbrot models were the best-fitting models. The SAD and gambin fitting results suggested that the Pi. elliottii community had a more balanced structure, with most species being relatively abundant. The multiple regression tree model detected four and six indicator species in P. orientalis and Pi. elliottii communities, respectively. The α-diversity index increased with a rise in altitude and showed a wavy curve with latitude. Linear regression between the β diversity and environmental and geographic distance indicated that the P. orientalis and Pi. elliottii understory communities tended to be dominated by different ecological processes. The partition of β diversity indicated that both communities were dominated by turnover processes, which were caused by environmental classification or spatial constraints. This study helped to understand the diversity maintenance in the P. orientalis and Pi. elliottii understory vegetation communities, and will benefit for diversity restoration and conservation of pure conifer forests.

In plateaus, land cover replaced climate as the vital environmental factor on the spatial composition of bumblebees with the altitude rising

Abstract Bumblebees show a series of advantages over other pollinating insects in offering pollination services for both the ecosystem and agricultural production, especially in high‐altitude areas. With climate warming, their diversity at high altitudes will be threatened. Therefore, more attention should be paid to the management of bumblebee resources at high altitudes to prevent their decline here. Discovering drivers responsible for the spatial variation of biodiversity is a benefit for developing appropriate management. Here, based on the bumblebee diversity on three plateau areas with an altitude gradient, the roles of different environmental factors, the climate, land cover, topography, habitat heterogeneity and soil, in the bumblebee composition were assessed by generalised dissimilarity modelling. And the relative importance of variables was evaluated by the impact on the magnitude of total biological change and the per cent change in deviance explained by models. According to the results, in the low‐altitude area, the climate played a vital role and the most important variable was the climate variable. Then, with the altitude rising, the effect of land cover continually increased. In the medium‐altitude area, the effects of different factors were detected to be similar, and the most important variables were a climate variable and a land cover variable. In the high‐altitude area, land cover finally replaced the climate as the most important factor, and one land cover variable was assessed as the most important variable. Our study revealed that the relative importance of different environmental factors on the biodiversity of bumblebees can differ as the altitude rises.

Assessment of Accuracy in Unmanned Aerial Vehicle (UAV) Pose Estimation with the REAL-Time Kinematic (RTK) Method on the Example of DJI Matrice 300 RTK.

The growing possibilities offered by unmanned aerial vehicles (UAV) in many areas of life, in particular in automatic data acquisition, spur the search for new methods to improve the accuracy and effectiveness of the acquired information. This study was undertaken on the assumption that modern navigation receivers equipped with real-time kinematic positioning software and integrated with UAVs can considerably improve the accuracy of photogrammetric measurements. The research hypothesis was verified during field measurements with the use of a popular Enterprise series drone. The problems associated with accurate UAV pose estimation were identified. The main aim of the study was to perform a qualitative assessment of the pose estimation accuracy of a UAV equipped with a GNSS RTK receiver. A test procedure comprising three field experiments was designed to achieve the above research goal: an analysis of the stability of absolute pose estimation when the UAV is hovering over a point, and analyses of UAV pose estimation during flight along a predefined trajectory and during continuous flight without waypoints. The tests were conducted in a designated research area. The results were verified based on direct tachometric measurements. The qualitative assessment was performed with the use of statistical methods. The study demonstrated that in a state of apparent stability, horizontal deviations of around 0.02 m occurred at low altitudes and increased with a rise in altitude. Mission type significantly influences pose estimation accuracy over waypoints. The results were used to verify the accuracy of the UAV's pose estimation and to identify factors that affect the pose estimation accuracy of an UAV equipped with a GNSS RTK receiver. The present findings provide valuable input for developing a new method to improve the accuracy of measurements performed with the use of UAVs.

The influence of altitude on combustion characteristics within gas‐fired boiler by numerical simulation

AbstractThe reduced atmospheric pressure and oxygen mass concentration at high altitudes have brought tremendous problems to the operation of gas‐fired boiler, mainly due to their influence on gas combustion and flow within furnace. Boilers designed for plateau region generally experience insufficient output, incomplete combustion, and reduced thermal efficiency when operating at high altitudes. However, the impacts from increasing altitude to the combustion characteristics within furnace are still ambiguous, which greatly hampers the boiler design for high‐altitude area. In this paper, the influences of altitude on the gas combustion characteristics within furnace were explored by using the computational fluid dynamics (CFD) method. The simulation shows that when altitude rises from 0 to 4000 m, the flame length and width increase as well as the temperature within furnace, but the burnout rate decreases due to the reduced residence time. The furnace length and diameter of the boiler designed for high altitudes should be appropriately increased to avoid the high temperature flame from scouring the back tube sheet and the furnace liner. While the CO emissions are generally very low, an increasing trend with altitude was observed. In addition, for each 1000 m of altitude rise, the NOx emissions increase by about 14 mg·m−3 at 100% loads and α = 1.05. The present work reveals the influence of altitude on combustion characteristics within gas‐fired boiler, which can guide the design and operation of the gas‐fired boiler at high altitudes.

Spatial Heterogeneity of Soil Bacterial Community Structure and Enzyme Activity along an Altitude Gradient in the Fanjingshan Area, Northeastern Guizhou Province, China.

Changes in altitude can cause regional microclimate changes, leading to the spatial heterogeneity of environmental factors and soil bacteria. However, the internal driving process and mechanism remain unclear. Here, we selected Fanjingshan, a typical nature reserve in the subtropical region of south China with a clear altitudinal belt, to reveal the response mechanisms of microbial populations with altitude changes. We examined the physiochemical and biological properties (pH and soil enzyme activities) of 0~10 cm soil layers, soil bacterial diversity, and community structure across the 2.1 km belt (consisting of six altitude ranges). Our results showed that soil pH was highest at the altitude range below 900 m and decreased with altitude thereafter. Soil enzyme activities showed an overall decreasing trend with altitude rising. The soil sucrase and catalase activity was highest (48.35 mg.g-1.d-1 and 23.75 µmol.g-1, respectively) at altitudes below 900 m; the soil urease activity was highest (704.24 µg.g-1.d-1) at 900~1200 m; and the soil acid phosphatase activity was highest (57.18 µmol.g-1) at 1200~1500 m. In addition, the soil bacterial community diversity showed a linear increasing trend, with the maximum abundance at 1500~1800 m. Soil pH was correlated with enzyme activity and bacterial community composition and structure, and the correlation was the strongest between pH and the distribution of bacterial diversity at altitudes below 900 m. Overall, soil enzyme activities and soil bacterial diversity showed spatial heterogeneity along the altitude gradient, and their community structure and composition were affected by altitude as a result of changes in soil physicochemical factors. This study provides a better and deeper understanding of the spatial succession of soil in the Fanjingshan area and the distribution pattern of soil microorganisms in central subtropical mountain ecosystems.

The effect of high altitude environment on diesel engine performance: Comparison of engine operations in Hangzhou, Kunming and Lhasa cities

The all-area operating performance of the vehicles requires the development of diesel engines that can operate at high altitudes without significant performance deterioration. Prior to optimizing the efficiency and emissions of highland engines, there is a necessity to investigate the underlying causes of engine performance degradation. The purpose of this paper was to study the in-cylinder activities occurring in the combustion chamber of diesel engines at high altitudes, which can help explain the effect of altitude on engine efficiency and emissions of concern to the customer. Specifically, a turbocharged direct injection compression ignition engine was operated at a constant engine speed and load, but at different altitudes. The theoretical analyses based on experimental data suggested that the mismatch between air and diesel quantities caused by the high altitude atmosphere led to the engine combustion deterioration. Specifically, the lower gas density at high altitudes during fuel injection resulted in a reduction of the injection angle and an enhancement of the penetration capability. In addition, the rise in altitude extended the ignition delay, which increased the fuel fraction mixed with air in the premixed combustion stage and raised the pressure rise rate. Moreover, at high altitudes, the reduction in excess air ratio and increased possibility of wall impingement of the fuel droplets resulted in uneven mixture concentration distribution and reduced air utility. Accordingly, combustion deterioration occurred in the combustion chamber of the plateau engines, which reduced energy release during main mixing-controlled combustion, lowered combustion efficiency, increased exhaust energy, and raised engine-out incomplete combustion emissions. All these effects resulted in a decrease in engine thermal efficiency of ∼6.5% and an increase in soot emissions of ∼4.2 times from Hangzhou to Lhasa city for the engine and operating conditions investigated in this study. Consequently, engines operating in highland areas need to be optimized in terms of efficiency and emissions.

Eco-Stoichiometric Characteristics of Rhizosphere and Bulk Soils of Smilax china L. along Vertical Zone Spectrum of Fanjing Mountain.

To explore the correlations between nutrients and stoichiometric characteristics in the rhizosphere and bulk soils of understory Smilax china L. in forest ecosystems at different altitudes and to clarify the rhizosphere effect of understory vegetation in forest ecosystems and its response strategy to altitude, providing a theoretical basis for better forest ecological environment protection and high-quality development in Fanjing Mountain. Understory Smilax china L. at four different altitudes were selected, with the differences and influencing factors of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) mass fractions and stoichiometric ratios in their rhizosphere and bulk soils analyzed. The average mass fractions of total C, total N and alkali-hydrolyzed N in the rhizosphere and bulk soils of Smilax china L. at different altitudes were 224.43 and 181.55 g·kg−1; 9.56 and 6.81 g·kg−1; and 648.19 and 600.70 g·kg−1, respectively. The rhizosphere effect of Smilax china L. was significant at altitudes of 500 m and 1000 m but became not so prominent with the rise of altitude. The C:N ratio in the rhizosphere and bulk soils ranged from 19.51 to 39.75 and the C:P ratio ranged from 225.29 to 543.05. C accumulation is greater than N accumulation in the rhizosphere and bulk soils of Smilax china L., and both present P limitation. Based on the comprehensive analysis of the mass fractions and eco-stoichiometric ratios of soil nutrients, the P limitation in Fanjing Mountain forest ecosystem is commonly seen and should be addressed.

云南省植被水分利用效率时空变化及影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 云南省植被水分利用效率时空变化及影响因素 DOI: 10.5846/stxb202011253023 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41871198） Spatiotemporal variation and influencing factors of vegetation water use efficiency in Yunnan Province Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:对云南省植被水分利用效率（WUE）的时空特征及影响因素进行研究可以更加全面的了解全球气候变化在区域上的响应。基于MODIS数据定量估算了2000-2014年云南省植被水分利用效率，利用趋势分析法和相关分析来对其时空格局和影响因素进行研究。研究结果表明：（1）云南省植被WUE整体呈现显著上升的趋势，增速为0.0078 gC mm-1 m-2 a-1，年内表现为"M"型的变化趋势。2009-2013年的干旱对该地区植被WUE产生了滞后的正效应。不同土地利用类型下的植被WUE从高到低依次为森林，灌木地，草地和耕地。（2）在空间分布上植被WUE呈现西部高于东部的分布特征；在时间尺度上呈现北增南减的趋势。云贵高原与青藏高原的连接区域--丽江市的植被WUE最高，整体上大于2.5 gC mm-1 m-2。澜沧江上游的三江并流区植被WUE随着山脉的走势呈现条状变化分布，不仅是植被WUE的低值集中区，同时也是植被WUE增加10%以上的集中区，另外滇东北和滇东南也是植被WUE的低值区。总的来看，除丽江以外，其他WUE高值区从2000-2014年呈下降的趋势，WUE低值区呈上升的趋势。（3）随着海拔的上升，植被WUE呈先上升后下降的变化趋势，并且海拔越高植被WUE增加越明显，变化率为0.01%。在低海拔区植被蒸散量（ET）和总初级生产力（GPP）都较高，随着海拔的上升ET骤降，GPP波动下降，直至海拔3000 m左右植被WUE达到峰值。高于海拔3000 m后，GPP直线下降，ET波动变化，直至海拔5000 m左右植被WUE几乎为0。（4）相较于降水因子，植被WUE受气温影响更大，特别是在三江并流区，其他地区则受非气候因素影响较大。在全球气候变化的背景下，这些发现展现了全球碳水循环变化在区域上的响应；云南省作为中国低纬高原的主体，研究也可为全球低纬高原区域生态建设提供参考。 Abstract:The study of the spatiotemporal characteristics and influencing factors of vegetation water use efficiency (WUE) in Yunnan Province could provide a more comprehensively understanding of the regional response to global climate change. In this study, MODIS data were used to quantitatively estimate the water use efficiency in Yunnan Province from 2000 to 2014, and trend analysis and correlation analysis were used to investigate the spatiotemporal patterns and influencing factors. The results showed that:(1) the overall WUE in Yunnan Province indicated a significant upward trend, with a growth rate of 0.0078 gC mm-1 m-2 a-1, and exhibited an "M" shape trend during the year. The drought events that occurred during 2009-2013 had a lagged positive effect on the vegetation WUE in this area. The vegetation WUEs of different land use types, in descending order, were forest, shrubland, grassland and the cultivated land. (2) The spatial distribution of WUE was higher in the west than in the east with a tendency of increasing in the north and decreasing in the south. The highest WUE was found in Lijiang, the region connecting the Yunnan-Guizhou Plateau and the Qinghai-Tibet Plateau, where the WUE was greater than 2.5 gC mm-1 m-2 overall. The vegetation WUE in the Three Parallel Rivers of upper Lancang River showed a striped distribution with the trend of the mountains, and was a concentration of low vegetation values. But it was also a focus where the WUE increased by more than 10%. In addition, northeastern and southeastern Yunnan were also areas with low WUE. Overall, except for Lijiang, there was a decreasing trend of high WUE and an increasing trend of low WUE from 2000 to 2014. (3) With the rise of altitude, WUE showed a tendency to increase first and then decrease, and the increase of WUE was more obvious in the higher altitude, with a change rate of 0.01%. Both evapotranspiration (ET) and Gross Primary Productivity (GPP) were prominent at low altitude, and with the rise of altitude ET plummets and GPP fluctuates and decreases until the peak of WUE was reached 3000 m. Above about 3000 m, the GPP dropped linearly and the ET fluctuated until the WUE was almost zero at about 5000 m. (4) Compared with precipitation, WUE was more obviously influenced by temperature, especially in the Three Parallel Rivers, while other regions were more significantly influenced by non-climatic factors. In the context of global climate change, the findings demonstrated the regional response to changes in the global carbon and water cycle; as the main body of low-latitude plateau in China, this study also could provide a reference for the ecological construction in low-latitude plateau regions around the world. 参考文献 相似文献 引证文献

基于集合经验模态分解去趋势的水分利用效率对气候变化响应的高程分异——以“21世纪海上丝绸之路”沿线省份为例

PDF HTML阅读 XML下载 导出引用 引用提醒 基于集合经验模态分解去趋势的水分利用效率对气候变化响应的高程分异——以“21世纪海上丝绸之路”沿线省份为例 DOI: 10.5846/stxb202107091848 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目（41971382）；江苏省科技厅研究生科研创新项目（1812000024462） Elevation differences in the response of ecosystem water use efficiency to climate change based on EEMD detrending:A case study of the provinces along the “21st Century Maritime Silk Road” Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:水分利用效率(WUE)是表征陆地碳-水循环耦合关系的重要指标，但其对气候变化响应的高程分异仍不清楚。通过集合经验模态分解(EEMD)去趋势和偏相关方法，以"21世纪海上丝绸之路"沿线省份为研究区，揭示WUE对气候变化的响应及其随高程的分异。研究结果表明：(1)研究区内WUE多年均值由中心向南北递减。不同植被类型的WUE多年均值由高到低依次为：常绿针叶林、混交林、常绿阔叶林、稀树灌木草地、耕地和城市建设用地。(2)51.11%的区域表现出均温与WUE的正相关；而81.46%地区表明温差的扩大会使得WUE增加；有近一半的研究区表明最高温的升高有利于提高WUE，而最低温的作用则相反；有67.99%的区域表明降水增多反而会导致WUE的减少。(3)在大多数土地覆盖类型，日温差和最低温主要与WUE呈正相关，而最高温和降水主要与WUE呈负相关。在常绿针叶林、耕地和城市建设用地，日均温与WUE呈负相关。在其他三种植被类型下则呈正相关。(4)在低海拔地区，均温与WUE呈负相关而在中高海拔地区则转变为正相关关系。而最高温则正好相反。降水与WUE的负相关关系系数随高度的增加而不断加强，而温差和最低温与WUE的正相关关系也随高度的增加而剧烈波动增强。 Abstract:Water use efficiency (WUE) is an important index representing the coupling relationship between terrestrial carbon and water cycle, but the elevation differences in the response of WUE to climate change remains unclear. By Ensemble empirical mode decomposition (EEMD) de-trending and partial correlation methods, this paper takes provinces along the "21st Century Maritime Silk Road" as examples to reveal the response of WUE to climate change and its differentiation with elevation. The results showed that:(1) the multiyear average WUE decreased from the center to the south and the north. The multiyear average WUE of different vegetation types from high to low was as follows:evergreen needle-leaf forest, mixed forest, evergreen broadleaf forest, deciduous broadleaf forest, savannas, croplands and urban/built-up. (2) About 51.11% of the area showed a positive correlation between average temperature and WUE, and 81.46% of the area showed that diurnal temperature and WUE were positively correlated. Nearly half of the study area indicated that the highest temperature had positive coefficient with WUE, while the lowest temperature was the opposite. In 67.99% of the area, increasing precipitation led to less WUE. (3) In most land cover types, the daily diurnal temperature range and the minimum temperature were mainly positively correlated with WUE, while the maximum temperature and precipitation were negatively correlated with WUE. In evergreen coniferous forests, croplands and urban/built-up, the daily average temperature was negatively correlated with WUE, while it was positive correlation in the other three vegetation types. (4) Average temperature had a negative coefficient with WUE in the low-altitude area, while the coefficient was positive in the mid- and high-altitude area. But it was the opposite in the relationship between the maximum temperature and WUE. The negative correlation between average precipitation and WUE became stronger with altitude rising. Meanwhile, the positive correlation between diurnal temperature and WUE, the minimum temperature and WUE also became stronger with altitude rising but with wild fluctuation. 参考文献 相似文献 引证文献

Hypoxia signature: A useful tool for hypoxia recognition among aircrew

Introduction: Hypoxia, often referred to as “silent killer,” a common aeromedical stressor in aviation, may have catastrophic events in-flight unless recognized well in time. On exposure to hypoxia, an individual manifests a specific spectrum of symptoms referred to as “hypoxia signature.” The present study was conducted to assess the manifestation of “hypoxia signature” on repeated exposure to simulated hypobaric hypoxia for its potential usage as a tool for hypoxia recognition. Material and Methods: Twenty-two healthy adult volunteers were subjected to a simulated altitude of 22,000 feet for a duration of 5 min in the hypobaric altitude chamber. The symptoms experienced by the participants at the said altitude were recorded using a questionnaire. The heart rate (HR) and oxygen saturation (SpO2) were recorded during the exposure. The hypoxia exposure was repeated two more times with a minimum interval of 3 weeks between each. Paired t-test was used to compare the mean values of physiological parameters (HR and SpO2) between ground level and 22000 feet recorded in all the three exposures. The hypoxia symptoms and their severity reported during the exposures were compared with those of recalled symptoms (reported after 3 weeks of exposure) using McNemar test and Wilcoxon Signed Rank test, respectively. Results: Paired t-test revealed a statistically significant increase in HR and fall in SpO2 with rise in altitude from ground level to 22000 feet. The three most common symptoms consistently observed were lightheadedness, thinking slow, and warm feeling. The common hypoxic symptoms and their severity scores reported at 22,000 feet compared with recalled counterpart during subsequent exposures did not reveal any significant differences (P > 0.05). Conclusion: There was a high degree of similarity in the frequency and severity score of symptoms between acute exposure to hypobaric hypoxia and recall indicating evidence of repeatability of symptoms across the three sessions of hypoxia exposure within the individuals. This brings out the usefulness of “hypoxia signature” as a tool for hypoxia recognition and its application in hypoxia indoctrination and training for aircrew.

Editorial Note on Variation of carbon stock over altitudinal and slope gradients

By sequestering fuel in the environment and acting as a carbon trap, forests play a crucial role in battling climate change. The structure of the organisms and the carbon stock were analyzed using a standardized sampling approach over environmental gradients. In the 36 quadrant plots of 20 x 20 m each spread along transect lines, data was collected. Breast diameter ≥ 5cm and overall measured height for each tree in the main map. Using the allometric equation, above and below land biomass was measured, while the litter carbon was estimated as carbon by taking 50 percent of dry biomass. Soil samples were obtained using an auguring process and carbon was analyzed using the Walkley-Black method, while bulk density was analyzed using the oven-dried method. The data was analyzed using R software's one-way ANOVA. The carbon stocks showed distinct differences in environmental gradients in the aboveground, belowground, litter biomass and soil organic carbon. The carbon stock above and below ground has shown a declining pattern along with rising altitude, although organic soil carbon and liter carbon showed a rising pattern along with altitude rise. The mean above and below field carbon stocks were respectively 156.60 t C ha-1 and 31.32 t C ha-1 while the stocks of litter carbon and soil organic carbon were respectively 2.72 t C ha-1 and 125.86 t C ha-1. The Gara-Mukitar forest's overall carbon stock density was found to be 316.6±67.15 t C ha-11. Similarly, in the above ground biomass, 49.5 percent of carbon was found, 9.9 percent in underground biomass, 0.9 percent in litter carbon and 39.8 percent in soil organic carbon (0-30 cm deep).

Tracing the isotopic signatures of cryospheric water and establishing the altitude effect in Central Himalayas: A tool for cryospheric water partitioning

This study focuses on the isotopic characterization of cryospheric water and quantification of different components contributing to Alaknanda River (major tributary of the Ganges River system) at its place of origin near snout of the Satopanth Glacier. A detailed understanding of various sources/flow components contributing to the river is useful for water resource management under changing climate scenario and helpful in risk assessment due to natural hazards in the headwater catchments, Extensive fieldwork was conducted, and water samples were collected from the river, snow, glacial ice, rain, lakes, and supraglacial channels of Satopanth Glacier Basin during the ablation period of 2017 and analysed for δ18O, δ2H, and 3H along with electrical conductivity. The results helped to establish the spatio-temporal and altitudinal variability in isotopic signatures of rain, snow, and ice in Satopanth Glacier Basin. The altitudinal effect in δ18O of pre-monsoon and monsoon rainfall is −0.13‰ and −0.41‰ per 100 m rise in elevation, respectively. Snow samples show depleting isotopic trend with an altitude effect of −0.43‰ in δ18O per 100 m rise in altitude. However, snowpack samples show an enrichment with time indicating post-depositional isotopic fractionation. The contrasting isotopic gradient in debris covered and non-debris covered ice are −0.9‰ and +3.4‰ per 100 m rise in elevation, respectively. These results divulge the spatial as well as temporal variation in cryospheric waters and these variations are used to derive the isotopic signatures of snow melt, glacier melt, and rain water. The results of hydrograph separation show that the snow melt, ice melt and rain water contribute about 33%, 49% and 18% respectively, to the discharge of Alaknanda River during the ablation period. Tracer based hydrograph separation indicates that the snow melt contribution dominates in river discharge during the initial ablation period. River discharge is a mixture of snow melt, glacier melt and rain water during July and August, while there is a dominance of glacier melt during end of the ablation period. The results of the present study highlight the importance of accounting the spatial and temporal variability in tracer signatures of cryospheric water for quantifying the contributions of snow and ice melt in a river originating from glacerised area.

Oxygen saturation at different altitudes in Nepal among adults

Introduction: The partial pressure of oxygen in the atmosphere decreases proportionately with an increase in the altitude. The study was done to compare the oxygen saturation of non-acclimatized adults going to different altitudes in Nepal. Materials and Methods: It was a descriptive observational study conducted on ten individuals of a medical team traveling to Humla district of Nepal for a multi-disciplinary medical camp. Oxygen saturation was measured at different altitudes i.e. in Kathmandu, Nepalgunj, in the flight at an altitude of 3360 meters and in Bargaun village of Humla district located at an altitude of 3300 meters. Mean pulse oximetry reading was calculated and compared. Results: Among the participants, age ranged from 24-57 years. Male to female ratio was 1.5:1. The mean SPO2 at Nepalgunj, Kathmandu, Bargaun of Humla and in the flight (at an altitude of 3360 meters) were 99.67 %, 97%, 91% and 87.4% respectively among the study participants. However, the difference in Oxygen saturation values at different altitudes among different gender and different age was not statistically significant. Conclusions: Oxygen saturation decreased linearly with the rise in altitude among all the study participants irrespective of age and gender.

Real-time monitoring hypoxia at high altitudes using electrical bioimpedance technique: an animal experiment.

Hypoxia poses a serious threat to pilots. The aim of this study was to examine the efficacy of electrical bioimpedance (EBI) in detecting the onset of hypoxia in real time in a rabbit hypoxia model. Thirty-two New Zealand rabbits were divided equally into four groups (control group and three hypoxia groups, i.e., mild, moderate, and severe). Hypoxia was induced by simulating various altitudes in the hypobaric oxygen chamber (3,000 m, 5,000 m, and 8,000 m). Both cerebral impedance and blood oxygen (SpO2) were monitored continuously. Results showed that the cerebral impedance increased immediately during the period of increasing altitude and decreased quickly to the initial baseline at the phase of descending altitude. Moreover, the change of cerebral impedance in the mild hypoxia group (3,000 m) was significantly smaller than those in the other two groups (5,000 m and 8,000 m, P < 0.05). The changes in cerebral impedance and SpO2 were significantly correlated based on the total of measurement data (r2 = 0.628, P < 0.001). Furthermore, the agreement analysis performed with Bland-Altman and standardized residual plots exhibited high concordance between cerebral impedance and SpO2. Receiver operator characteristic analysis manifested that the sensitivity, specificity, and area under the curve using cerebral impedance for changes in SpO2 >10% were 0.735, 0.826, and 0.845, respectively. These findings demonstrated that EBI could sensitively and accurately monitor changes of cerebral impedance induced by hypoxia, which might provide a potential tool for the real-time and noninvasive monitoring of hypoxic condition of pilots in flight for early identification of hypoxia.NEW & NOTEWORTHY This study is the first to examine the efficacy of electrical bioimpedance (EBI) in detecting the onset of high-altitude hypoxia in real time. The novelty of this research includes three aspects. First, the cerebral impedance of rabbits increased immediately during the rising of altitude and decreased quickly to the initial baseline at the phase of descending altitude. Second, there was a significant correlation and high concordance between cerebral impedance and SpO2. Third, cerebral impedance could determine the change of SpO2 resulting from hypoxia.

The Variation of Lightning Current Parameters with Altitude in Shandong Region

Lightning current parameters is the basis of the transmission line design and transformation essential parameters of lightning location system somewhere in shandong area ground ground lightning information lack of height of the statistical properties, not situation, the analysis of the influence of altitude on lightning parameters using global digital elevation data filled in the lightning location data in the lack of information, analysis of the lightning current parameters and the relationship between the altitude in the region. The variation of lightning current amplitude, lightning return times, ground flash density and other factors with altitude is studied, and the variation law of lightning parameters in this area with altitude is obtained. When the altitude is 1200∼2000m and 2400∼3200m, the number of lightning return stroke fluctuates greatly. When the altitude is from 2000 to 2800m, the number of lightning return strokes increases with the increase of altitude. With the rise of altitude, the proportion of normal lightning flashes in total lightning flashes in shandong area has a tendency to increase gradually. Due to the shortcomings of the above three kinds of observation data, we try to learn from each other to better reflect the lightning activity rule in shandong more comprehensively, accurately and effectively, and to provide certain theoretical basis and help for lightning protection and disaster reduction work, providing reference for the design and lightning protection transformation of power grid in shandong.

Study on Altitude Adaptability of a Turbocharged Off-Road Diesel Engine

Abstract This paper investigates the operating characteristics of an off-road diesel engine to enhance its power performance in plateau. First, the impacts of altitude on the power, fuel economy, and emissions characteristics were analyzed by a bench test. Second, the combustion and overall performance working at different altitudes were studied by three-dimensional numerical simulation, including the relationship between fuel injection parameters and engine performance. The results showed that altitude significantly affects the performance of the off-road diesel engine. As the altitude increased from 0 m to 2000 m, the engine power decreased as much as 4.3%, and the brake-specific fuel consumption (BSFC) increased as much as 6%. At the peak torque condition, the intake manifold boost pressure and the exhaust manifold pressure both reduced with a rise of altitude, while the intake and exhaust manifold temperatures both increased with a rise of altitude. Finally, after comparing the in-cylinder flow conditions and combustion characteristics given by six combustion chamber designs that have different shrinkage ratios, the engine performance at 4000 m altitude with five different fuel spray angles were further optimized. The engine rated power increased by 8.2% when the shrinkage ratio was 7.28% and the fuel spray angle was 150 deg at the 4000 m altitude.

Influence of geographical factors on thermal stress in northern Carpathians

While general features of mountain climate are well recognised, there is not many research regarded their bioclimatic differentiation. The aim of the present study is to answer the question how different geographical factors: elevation above sea level, physiographical type of area, climate continentality and location of area in relation to the main mountain ridge influence thermal stress in northern Carpathians. To analyse thermal stress in the region, daily meteorological data from 21 stations of national weather networks of Poland, Ukraine and Slovakia for the period 1986–2015 were used. Daily data of air temperature, relative humidity, total cloud cover and wind speed at 10 m above ground for 12 UTC were used because they represent midday hours which are mostly used for any human activity. The Universal Thermal Climate Index (UTCI) was applied as a measure of thermal stress. The results show that (1) cold stress significantly increases and heat stress decreases due to rise of altitude, (2) due to climate continentality and physiographical differences between western and eastern parts of northern Carpathians in their eastern edge, the cold stress is more evident than in western one, (3) at southward slopes of Carpathian, heat stress is significantly more frequent then at northward areas.

Assessment of Phenolic Content, Antioxidant Properties and Antimicrobial Activity of Flower and Leaf Extracts from Some Hypericum Species Affected by Wild Habitat Altitude

In this study, determination of habitat altitude effect on the total phenolic contents, antioxidant and antimicrobial activities of flower and leaf extracts from Hypericum montbretii, H. orientale and H. perforatum species was aimed. The plants were collected randomly from forages (altitudes were ranged from 430 to 1105 m a.s.l.) located in Western Black Sea Region, Turkey. Antioxidant properties of ethanolic extracts were determined with DPPH and ABTS assay and antimicrobial activities of the extracts on Bacillus pumilis NRRL BD-142, B. subtilis NRRL B-209, B. licheniformis NRRL-B-1001, B. cereus NRRL B-3711, Staphylococcus aureus ATCC 33862, Pseudomonas aeruginosa ATCC 27853, Listeria inocua ATCC 33090, L. monocytogenes ATCC 7644 and Escherichia coli ATCC 25922 were examined. Total phenolic contents and antioxidant activities of Hypericum species changed depending on the habitat altitude. The antimicrobial activity of the ethanolic extracts was evaluated by minimal inhibitory concentrations (MIC) method. Flower and leaf extracts exhibited a broad antibacterial spectrum, but they were not effective against Escherichia coli (ATCC 25922). Phenolic contents of all Hypericum species and antimicrobial activity of only H. perforatum extracts were significantly increased by altitude rising, but no positive correlation was detected in antioxidant activity of extracts due to habitat altitude.