Active layer hydrology in an arctic tundra ecosystem: quantifying water sources and cycling using water stable isotopes

Climate change and thawing permafrost in the Arctic will significantly alter landscape hydro‐geomorphology and the distribution of soil moisture, which will have cascading effects on climate feedbacks (CO₂ and CH₄) and plant and microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques (δ²H and δ¹⁸O) to infer sources and mixing of active layer waters in a polygonal tundra landscape in Barrow, Alaska (USA), in August and September of 2012. Results suggested that winter precipitation did not contribute substantially to surface waters or subsurface active layer pore waters measured in August and September. Summer rain was the main source of water to the active layer, with seasonal ice melt contributing to deeper pore waters later in the season. Surface water evaporation was evident in August from a characteristic isotopic fractionation slope (δ²H vs δ¹⁸O). Freeze‐out isotopic fractionation effects in frozen active layer samples and textural permafrost were indistinguishable from evaporation fractionation, emphasizing the importance of considering the most likely processes in water isotope studies, in systems where both evaporation and freeze‐out occur in close proximity. The fractionation observed in frozen active layer ice was not observed in liquid active layer pore waters. Such a discrepancy between frozen and liquid active layer samples suggests mixing of meltwater, likely due to slow melting of seasonal ice. This research provides insight into fundamental processes relating to sources and mixing of active layer waters, which should be considered in process‐based fine‐scale and intermediate‐scale hydrologic models. Copyright © 2016 John Wiley & Sons, Ltd.     

应用地震CT技术研究长白山火山的岩浆囊

中国火山学专家报导了长白山火山存在一定的潜在的喷发危险性及其地质背景等研究成果;美国、日本、德国的火山学家到该火山区进行过考察,也认为该火山存在一定的潜在危险性;国家科委根据有关方面的建议,已将“长白山火山危险性的研究”列入专项计划之中;其中有一个子课题是“应用地震ＣＴ技术研究长白山火山的岩浆囊”．本文报导的主要内容有：１）１９９４年张禹慎发展的“上地幔Ｓ波三维速度结构的方法”建立上地幔Ｓ波ＲＧ５．５速度模型,该模型能显示全球任一地区、任一剖面、深至５００公里的三维速度结构;他作出世界上２０个火山区,其中有１７个火山区下面均有明显的Ｓ波低速层,在不同程度上反映了＂低速层岩浆囊＂的存在;已作出通过长白山天地火山的３条速度剖面;该模型显示出：在长白山天池火山下面存在速度的负异常达２．５％的“低速囊”,其深度从３８—６５公里;其展布范围约１００—２００公里的范围;２）改进面波品质因数Ｑ值的成像方法,进一步收集２００次地震面波记录资料,应用“卷积反投影方法反演地壳面波品质因数Ｑ值的成像系统”长白山火山及其邻近地区面波Ｑ值分布,看出天池地区Ｑ＝１６１比中国地区Ｑ值的平均值偏低很多;这很可能与该地区下面地温偏高和岩层的     

长白山火山活动的现状和未来展望

长白山天池火山是中新世以来,特别是中更新世以来多次喷发并造成严重灾害的火山,是一座具有潜在喷发危险性的活动火山,文章主要阐述了全新世和近代火山活动及其喷发物,并对火山的现代活动与未来火山活动及其灾害作了评估。     

Carbon and suspended sediment transport in an impounded alpine river (Isère,France)

Carbon and total suspended sediment (TSS) loads were investigated from April 2006 to March 2008 in the mountainous watershed of the Isère River, French Alps (5570 km²). The river bed has been highly impounded for hydroelectricity production during the last century. Hydraulic flushes are managed every year to prevent TSS storage within upstream dams. The Isère River has been instrumented for high‐frequency monitoring of water, TSS by turbidity and carbon (organic, inorganic, dissolved and particulate) in order to evaluate the impact of natural floods and hydraulic flushes on annual loads. Annual TSS load which was estimated between 1.3 and 2.3 MT y^?1 (i.e. 233 to 413 T km^?2 y^?1) highlighted the high erodibility of the Isère watershed. Annual carbon load was estimated between 173 10³ T y^?1 and 199 10³ T y^?1 (i.e 31 to 36 T km^?2 y^?1). About 80% of the annual carbon loads were inorganic. The impact of hydraulic flushes on annual loads appeared limited (less than 3% for annual TSS load and about 1.5% for annual carbon load), whereas the most important natural flood event contributed to 20% of the annual TSS load and 10% of the annual carbon load. Copyright © 2012 John Wiley & Sons, Ltd.     

基于InSAR、GPS形变场的长白山地区火山岩浆囊参数模拟研究

利用差分合成孔径雷达干涉测量技术（DInSAR）获取长白山地区的形变场.结果显示1995~1998年期间,位于长白山东南侧的间白山火山存在6~12 cm的视线向形变,而长白山天池火山处于平静期,没有明显形变.利用2002~2003年的GPS和水准获取的形变数据,分别采用Mogi单源、双源模型反演了长白山地区火山的岩浆囊参数.其中双源模型拟合效果较为理想,两个点源一个位于长白山天池老火山口下方7.9 km处,另一个位于间白山火山下方5.5 km处.对双源模型反演得到的岩浆囊参数进行适当调整,拟合得到与InSAR形变场基本吻合的结果.上述研究结果表明长白山地区火山活动存在时间上的间歇性和空间上的迁移性,为进一步研究长白山地区火山活动机制提供了参考和依据.     

Long‐term carbon storage and hydrological control of CO2 exchange in tundra ponds in the Hudson Bay Lowland

Carbon dioxide fluxes and water balance were examined in 43 tundra ponds in the northern portion of the Hudson Bay Lowland near Churchill, Manitoba. Most of the ponds were hydrologically disconnected from their catchments during dry periods throughout the post‐melt season. However, episodic reconnection occurred following large precipitation events where depression storage was exceeded. Significant shifts in pond chemistry were observed following precipitation events, with the degree of CO₂ saturation increasing during these periods. Pond CO₂ concentrations rapidly fell to pre‐event levels following events, suggesting that hydrological connectivity can affect the magnitude and direction of CO₂ gas fluxes in tundra ponds. Atmospheric CO₂ invaded ponds with highly organic sediments for most of the summer, suggesting that terrestrially derived inorganic carbon was insufficient to meet the demands of algal net production. In contrast, ponds with highly mineral sediments continued to evade CO₂ during the summer. In a subset of 11 ponds, long‐term rates of carbon accumulation in sediment ranged from 0·6 to 2·2 mol C m^?2 year^?1. Very strong correlations existed between average sediment accumulation rates and pond perimeters and basin areas suggesting that peat may be a major source of sediment carbon. Aeolian transport is also a potentially large source of sediment carbon. Copyright © 2004 John Wiley & Sons, Ltd.     

Dissolved inorganic carbon isotopes of a typical alpine river on the Tibetan Plateau revealing carbon sources,wetland effect and river recharge

The Nyangqu River, the largest right bank tributary of the Yarlung Zangbo River in the Qinghai–Tibet Plateau, was representative of an alpine riverine carbon cycle experiencing climate change. In this study, dissolved inorganic carbon (DIC) spatial and seasonal variations, as well as their carbon isotopic compositions (δ¹³C_DIC) in river water and groundwater were systematically investigated to provide constraints on DIC sources, recharge and cycling. Significant changes in the δ¹³C_DIC values (from −2.9‰ to −23.4‰) of the water samples were considered to be the result of different contributions of two dominant DIC origins: soil CO₂ dissolution and carbonate weathering. Three types of rock weathering (dissolution of carbonate minerals by H₂CO₃ and H₂SO₄, and silicate dissolution by H₂CO₃) were found to control the DIC input into the riverine system. In DIC cycling, groundwater played a significant role in delivering DIC to the surface water, and DIC supply from tributaries to the main stream increased from the dry season to the wet season. Notably, the depleted δ¹³C_DIC ‘peak’ around the 88.9° longitude, especially in the September groundwater samples, indicated the presence of ‘special’ DIC, which was attributed to the oxidation of methane from the Jiangsa wetland located nearby. This wetland could provide large amounts of soil organic matter available for bacterial degradation, producing ¹³C-depleted methane. Our study provided insights regarding the role of wetlands in riverine carbon cycles and highlighted the contribution of groundwater to alpine riverine DIC cycles.     

Influence of climate on alpine stream chemistry and water sources

The resilience of alpine/subalpine watersheds may be viewed as the resistance of streamflow or stream chemistry to change under varying climatic conditions, which is governed by the relative size (volume) and transit time of surface and subsurface water sources. Here, we use end‐member mixing analysis in Andrews Creek, an alpine stream in Rocky Mountain National Park, Colorado, from water year 1994 to 2015, to explore how the partitioning of water sources and associated hydrologic resilience change in response to climate. Our results indicate that four water sources are significant contributors to Andrews Creek, including snow, rain, soil water, and talus groundwater. Seasonal patterns in source‐water contributions reflected the seasonal hydrologic cycle, which is driven by the accumulation and melting of seasonal snowpack. Flushing of soil water had a large effect on stream chemistry during spring snowmelt, despite making only a small contribution to streamflow volume. Snow had a large influence on stream chemistry as well, contributing large amounts of water with low concentrations of weathering products. Interannual patterns in end‐member contributions reflected responses to drought and wet periods. Moderate and significant correlations exist between annual end‐member contributions and regional‐scale climate indices (the Palmer Drought Severity Index, the Palmer Hydrologic Drought Index, and the Modified Palmer Drought Severity Index). From water year 1994 to 2015, the percent contribution from the talus‐groundwater end member to Andrews Creek increased an average of 0.5% per year (p < 0.0001), whereas the percent contributions from snow plus rain decreased by a similar amount (p = 0.001). Our results show how water and solute sources in alpine environments shift in response to climate variability and highlight the role of talus groundwater and soil water in providing hydrologic resilience to the system.     

Influence of microclimate and geomorphological factors on alpine vegetation in the Western Swiss Alps

Among the numerous environmental factors affecting plant communities in alpine ecosystems, the influence of geomorphic processes and landforms has been minimally investigated. Subjected to persistent climate warming, it is vital to understand how these factors affect vegetation properties. Here, we studied 72 vegetation plots across three sites located in the Western Swiss Alps, characterized by high geomorphological variability and plant diversity. For each plot, vascular plant species were inventoried and ground surface temperature, soil moisture, topographic variables, earth surface processes (ESPs) and landform morphodynamics were assessed. The relationships between plant communities and environmental variables were analysed using non-metric multi-dimensional scaling (NMDS) and multivariate regression techniques (generalized linear model, GLM, and generalized additive model, GAM). Landform morphodynamics, growing degree days (sum of degree days above 5°C) and mean ground surface temperature were the most important explanatory variables of plant community composition. Furthermore, the regression models for species cover and species richness were significantly improved by adding a morphodynamics variable. This study provides complementary support that landform morphodynamics is a key factor, combined with growing degree days, to explain alpine plant distribution and community composition. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Soil organic carbon and nitrogen content of density fractions and effect of meadow degradation to soil carbon and nitrogen of fractions in alpine Kobresia meadow

This research was conducted on the non-disturbed native alpine Kobresia meadow(YF) and the severely degraded meadow(SDL) of Dari County of Qinghai Province.By a density fractionation approach,each soil sample was divided into two fractions:light fraction(LF) and heavy fraction(HF).The obtained fractions were analyzed for organic carbon(OC) and nitrogen(N) concentrations.The results showed:(1) the OC concentration in HF and LF was 3.84% and 28.63% respectively while the nitrogen concentration in HF and LF wa...     

The uplifting process of the Bogda Mountain during the Cenozoic and its tectonic implication

The Tianshan Mountains have undergone its initial orogeny, extension adjusting and re-orogeny since the Late Paleozoic. The re-orogeny and uplifting process of the orogeny in the Mesozoic and Cenozoic are two of most important events in the geological evolution of Euro-Asian continent, which resulted in the formation of the present range-and-basin pattern in topography of the Tianshan Mountains and its adjacent areas. Thermochronology results by the method of fission-track dating of apatite suggest three obvious uplifting stages of the Bogad Mountain Chain re-orogeny during the Cenozoic, i.e. 5.6-19 Ma, 20-30 Ma, and 42-47 Ma. The strongest uplifting stage of the mountain is the second one at 20 -30 Ma, when the mountain uplifted as a whole, and the beginning of re-orogeny was no less than 65 Ma. Furthermore, our studies also show that the uplifting types of the mountain are variable in the dif-ferent time periods, including uplifting of mountain as a whole and differential uplifting. The apparently diversified uplifting processes of the mountain chain are characterized by the migration (or transfor-mation) of the uplifting direction of the mountain from west to east and from north to south, and the main process of mountain extending is from north to south.     

Establishment of apparent quantum yield and maximum ecosystem assimilation on Tibetan Plateau alpine meadow ecosystem

The alpine meadow is widely distributed on the Tibetan Plateau with an area of about 1.2×106kn2. Damxung County, located in the hinterland of the Tibetan Plateau, is the place covered with this typical vegetation. An open-path eddy covariance system was set up in Damxung rangeland station to measure the carbon flux of alpine meadow from July to October,2003. The continuous carbon flux data were used to analyze the relationship between net ecosystem carbon dioxide exchange (NEE) and photosynthetically active radiation (PAR), as well as the seasonal patterns of apparent quantum yield (α) and maximum ecosystem assimilation (Pmax).Results showed that the daytime NEE fitted fairly well with the PAR in a rectangular hyperbola function, with α declining in the order of peak growth period (0.0244 μmolCO2 · μmol-1pAR) ＞early growth period ＞ seed maturing period ＞ withering period (0.0098 μmolCO2 · μmol-1pAR).The Pmax did not change greatly during the first three periods, with an average of 0.433mgCO2· m-2· s-1, i.e. 9.829 μmolCO2· m-2· s-1. However, during the withering period, Pmax was only 0.35 mgCO2 · m-2 · s-1, i.e. 7.945 μmolCO2 · m-2 · s-1. Compared with other grassland ecosystems, the α of the Tibetan Plateau alpine meadow ecosystem was much lower.     

Comparison of Cu and Zn cycling in eutrophic lakes with oxic and anoxic hypolimnion

Data on the cycling of Cu and Zn in two eutrophic lakes are presented: Lake Greifen that becomes seasonally anoxic in its hypolimnion and Lake Sempach that is aerated during winter and oxygenated during summer. They suggest that hypolimnetic oxygenation 1) enhances the release of copper from the sediment but 2) also accelerates the entrapment and deposition of Cu and Zn by freshly formed Mn- and Fe-oxides.     

昆仑山口西8.1级地震前后山西及邻区速度场和应变场的变化

在山西及邻区,1999~2004年几乎所有的GPS站速度都小于1999~2001年,鄂尔多斯西部大多数GPS站1999~2004年的运动方向相对于1999~2001年发生了逆时针旋转。鄂尔多斯和山西中南部的NWW向运动与昆仑山口西8.1级大震断裂带以北地区的运动方向是一致的,而鄂尔多斯以南的向东运动与断裂带以南地壳的运动方向也是一致的。鄂尔多斯的逆时针旋转形成了109.0°E以西地区E-W方向的压应变。而它的逆时针旋转和太行山东部的向东伸展运动形成了109.0°E以东地区E-W方向的张应变。鄂尔多斯东部和山西地区在8.1级大震后的增量应变场减弱了基本应变场E-W方向压应变的积累,而鄂尔多斯西部的增量应变场增加了E-W方向压应变的积累。     

Gas contents and CO2 isotope studies on fluid inclusion in ultra-high pressure metamorphic rock from Shuanghe area, Dabie Mountain

Step heating experiments on ultra-high pressure (UHP) mcks from the Dabie Mountain shows a majority of CO₂ in fluid inclusion (excluding H₂O); CO is also a significant component, with a small content of N₂ and CH₄. Carbon isotopic composition of CO₂ in fluid of metamorphic climax stage (-25%0- -30%0) is different from that of mantle carbon, indicating that UHP rocks did not experience obvious transformation by mantle fluids despite their subduction depth. CO₂ was derived from carbon matter in the pmtoliths of UHP rocks in a relatively confined system, showing that the UHP rocks subsided quickly and uplifted quickly from the mantle. Current organization: Research Institute of Petroleum Exploration and Development, Beijing 100083, China.     

中高山地区滑坡发育地形地貌因子敏感性研究

为分析海拔高度大于1 300m的中高山地区地形地貌因子对滑坡发育的敏感性程度,运用基于因子综合贡献率的敏感性分析方法,研究黔东北中高山地区坡面形态、地形坡度、相对高差三类影响因子对滑坡发育的影响程度.在各类影响因子对滑坡发育频数、面积及体积分量贡献率的基础上,利用顺序赋值法量化各分量贡献率的贡献指数,并以各分量贡献指数的几何平均数构建敏感性系数,定量分析三类地形地貌影响因子对中高山地区滑坡发育的敏感性.研究结果表明,阶梯形和凸形坡面形态的斜坡中后部为地貌演化堆积区,能提供较大重力势能,属滑坡发育的敏感性坡面形态因子;地形坡度在18°～22°之间的较陡坡和相对高差在40～80m之间的矮坡常分布于受地表水强烈冲刷的地带,在一定重力势能和强烈地下水共同作用下,极易诱发浅层小规模滑坡;地形坡度大于27°的极陡坡和相对高差大于120m的高坡由于具备较大重力势能,常诱发深层大规模滑坡.     

Soil organic carbon and nitrogen content of density fractions and effect of meadow degradation to soil carbon and nitrogen of fractions in alpine <Emphasis Type="Italic">Kobresia</Emphasis> meadow

This research was conducted on the non-disturbed native alpine Kobresia meadow (YF) and the severely degraded meadow (SDL) of Dari County of Qinghai Province. By a density fractionation approach, each soil sample was divided into two fractions: light fraction (LF) and heavy fraction (HF). The obtained fractions were analyzed for organic carbon (OC) and nitrogen (N) concentrations. The results showed: (1) the OC concentration in HF and LF was 3.84% and 28.63% respectively while the nitrogen concentration in HF and LF was 0.362% and 1.192% respectively in 0–10 cm depth. C:N ratio was 10.6 in HF and 23.8 in LF respectively. (2) As far as the ratio of OC in given fraction to that in gross sample was concerned, dominance of OC in HF was obvious in the whole soil profile. OC in HF increased from 78.95% to 90.33%, while OC in LF decreased from 21.05% to 9.68% with depths. (3) Soil total OC amounted to 47.47 in YF while 17.63 g · kg⁻¹ in SDL, in which the OC content in HF decreased from 37.31 to 16.01 g · kg⁻¹ while OC content in LF decreased from 10.01 to 1.62 g · kg⁻¹. In other words, results of OC and N content show meadow degradation led to the loss of 57% OC in HF and 84% OC in LF from originally native ecosystem on alpine meadow. In addition, meadow degradation led to the loss of 43% N in HF and 79% N in LF from originally native ecosystem on alpine meadow. (4) The main reason for loss of C and N in LF during meadow degradation was not attributed to the decrease of OC and N concentration in LF and LF, but to the decrease in LF dry weight. Loss of N was far lower than loss of C in HF. This may suggest that there is difference in protection mode of C and N in HF. Supported by National Natural Science Foundation of China (Grant No. 30660120), Science Support Project in the Source Region of the Three Rivers (Grant No. 2005-SN-2)     

Study on the Natural Mineral Water Resource Bearing Capacity and its Driving Factors in Fusong County,Changbai Mountain Area,Jilin Province of China

Water Resources - In order to maintain the sustainable exploitation of the natural mineral water resources in Changbai Mountain Area with the continuously increasing exploitation intensity,...     

Synergistic effect of vegetation and air temperature changes on soil water content in alpine frost meadow soil in the permafrost region of Qinghai‐Tibet

Seasonal changes over 2 years (2004–2006) in soil moisture content (θ_v) of frozen alpine frost meadow soils of the Qinghai‐Tibet plateau permafrost region under three different levels of vegetation cover were investigated. Vegetation cover and air temperature changes had significant effects (synergistic effect) on θ_v and its distribution in the soil profile. During periods of soil freezing or thawing, the less the vegetation cover, the quicker the temperature drop or rise of soil water, and the shorter the duration of the soil water freeze–thaw response in the active soil layer. Under 30% and 65% vegetation cover the amplitude of variation in θ_v during the freezing period was 20–26% greater than that under 93% cover, while during the thawing period, it was 1·5‐ to 40·5‐fold greater. The freezing temperature of the surface soil layer, ^fT_s, was 1·6 °C lower under 30% vegetation cover than under 93% vegetation cover. Changes in vegetation cover of the alpine frost meadow affected θ_v and its distribution, as well as the relationship between θ_v and soil temperature (T_s). As vegetation cover decreased, soil water circulation in the active layer increased, and the response to temperature of the water distribution across the soil profile was heightened. The quantity of transitional soil phase water at different depths significantly increased as vegetation cover decreased. The influence of vegetation cover and soil temperature distribution led to a relatively dry soil layer in the middle of the profile (0·70–0·80 m) under high vegetation cover. Alpine meadow θ_v and its pattern of distribution in the permafrost region were the result of the synergistic effect of air temperature and vegetation cover. Copyright © 2007 John Wiley & Sons, Ltd.     

New observations on the geomorphology and origins of Mountain Lake,Virginia

Mountain Lake is the only natural lake of significance in the unglaciated southern Appalachian Highlands. It is located near the summit of Salt Pond Mountain, Giles County Virginia, at an elevation of 1177 m. It is underlain by Ordovician and Silurian non‐calcareous shale and sandstone of the Martinsburg, Juniata and Clinch formations. Historical (250 years) and sediment (6000 years) records suggest that the size of the lake has varied periodically. In the 1930s lake origin was proposed as due to valley damming by a lateral landslide (Hutchinson and Pickford, 1932) or damming by scree (Sharp, 1933). A later theory modified the landslide hypothesis to the primarily vertical collapse of a canyon feature in the Clinch (Parker et al., 1975). Fracture trace analysis now reveals a regional lineation feature associated with the lake. This feature is present surficially both downgradient from the lake to the northwest, and upgradient to the southeast. Sonar bathymetry and diver reconnaissance show it expressed as a (relatively sediment‐free) narrow open crevice in the deepest (33 m) portion of the lake, probably a fault. Hydrologic observation and resistivity suggest preferential water movement along this fracture, as well as leakage directly from the lake. The present study suggests conduit erosion within this feature and periodic vertical downsettling of overlying Clinch material as the primary mechanism of lake origin and water‐level fluctuations through time. Copyright © 2001 John Wiley & Sons, Ltd.