Elevational patterns of warming effects on plant community and topsoil properties: focus on subalpine meadows ecosystem

Climate warming profoundly affects plant biodiversity, community productivity, and soil properties in alpine and subalpine grassland ecosystems. However, these effects are poorly understood across elevational gradients in subalpine meadow ecosystems. To reveal the elevational patterns of warming effects on plant biodiversity, community structure, productivity, and soil properties, we conducted a warming experiment using open-top chambers from August 2019 to August 2022 at high(2764 m a. s. l.), ...     

A Preliminary Study on the Phenomenon of Microseismic Fluctuations before Impending Strong Earthquake

Based on repeated comparison studies of broadband digital seismic records before the Wenchuan M_S8. 0,Yushu M_S7. 1 and Qingchuan M_S5. 4 earthquakes,the possible microseismic fluctuations before impending earthquakes were preliminarily identified. In order to verify and test this phenomenon,a real-time tracking technical system was established by using continuous waveform records of more than 200 wide-band digital seismic stations in regional networks such as Gansu,Qinghai,Sichuan,Yunnan and Tibet.Through real-time tracking and dynamic monitoring of 24 earthquakes with M≥5. 0 occurring in the Qinghai-Tibetan block during the period of 2012-2014 and the observations of stations in some non-seismic areas,the reproducibility and objectivity of the impending earthquake phenomenon were verified. The main characteristics of the microseismic fluctuation phenomena immediately preceding the strong earthquakes are as follows:(1)the spectrum range is wider,the dominant frequency is 11-16 Hz,and the spectrum shape is more regular;(2)it appears 6-24 days before the earthquake,averaging about 15 days;(3)it is possible to be recorded by the stations within the epicenter distance of 50 km,and the stations with the epicenter distance of more than 50 km generally cannot record it;(4)this phenomenon is directional,i. e. the direction in which the activity degree,N-value,varies significantly may be related to the location of the seismic source,the seismogenic fault and the distribution of aftershocks of the strong earthquake. The preliminary study shows that the impending-earthquakes microseismic phenomena may be related to the pre-activity,micro-vibration and micro-rupture in the source region in the imminent stage,or the microactivity and micro-rupture associated with the active tectonics.     

Reservoir Porosity Measurement Uncertainty and its Influence on Shale Gas Resource Assessment

Reservoir porosity is a critical parameter for the process of unconventional oil and gas resources assessment. It is difficult to determine the porosity of a gas shale reservoir, and any large deviation will directly reduce the credibility of any shale gas resources evaluation. However, there is no quantitative explanation for the accuracy of porosity measurement. In this paper, measurement uncertainty, an internationally recognized index, was used to evaluate the results of porosity measurement of gas shale plugs, and its impact on the credibility of shale gas resources assessment was determined. The following conclusions are drawn:(1) the measurement uncertainty of porosity of a shale plug is 1.76%–3.12% using current measurement methods, the upper end of which is too large to be acceptable. It is suggested that the measurement uncertainty should be factored into the standard helium gas injection porosity determination experiment, and the uncertainty should be less than 2.00% when using a high-precision pressure gauge;(2) in order to reduce the risk for exploration and decision-making, attention should be paid to the large uncertainty(30% at least) of shale gas resource assessment results, sometimes with corrections being made based on the practical considerations;(3) a pressure gauge with an accuracy of 0.25% of the full scal cannot meet the requirements of porosity measurement, and a high-precision plug cutting method or high-precision bulk volume measurement method such as one using 3 D scanning, is recommended to effectively reduce porosity uncertainty;(4) the method and process for evaluating the measurement uncertainty of gas shale porosity could also be referred for assessment of experimental quality by other laboratories.     

Remote Sensing-based Spatiotemporal Distribution of Grassland Aboveground Biomass and Its Response to Climate Change in the Hindu Kush Himalayan Region

The grassland in the Hindu Kush Himalayan(HKH) region is one of the large st and most biodiverse mountain grassland types in the world,and its ecosystem service functions have profound impacts on the sustainable development of the HKH region.Monitoring the spatiotemporal distribution of grassland aboveground biomass(AGB) accurately and quantifying its response to climate change are indispensable sources of information for sustainably managing grassland ecosystems in the HKH region.In this study,...     

U-Pb-Hf isotopes and petrogenesis of Late Jurassic akakitic quartz monzodiorite in Xingcheng area,western Liaoning Province

The petrogenesis and geodynamic setting of the Late Jurassic Baita porphyry quartz monzodiorite in Xingcheng--Liaoxi area provide information for understanding the Mesozoic tectonic evolution of the northeastern North China Craton. In this paper, geochronological, whole-rock geochemical, and in-situ zircon Hf isotopic analyses of Baita porphyry quartz monzodiorite were investigated to constrain the crystallization age and petrogenesis. Zircons exhibit typical oscillatory zoning in cathodoluminescence images and show relatively high Th/U ratios(0.78--1.62), and U-Pb analyses indicate that these rocks were crystallized during the Late Jurassic(159±1 Ma). Geochemically, they are characterized by high contents of SiO_2(65.21 wt%--65.31 wt%), Al_2O_3(16.29 wt%--16.31 wt%), Sr(521×10~(-6)-539×10~(-6)), and Sr/Y ratio(45.1--47.8) but low Y(10.9×10~(-6)-12.0×10~(-6)), with obvious adakitic geochemical affinities. These above-mentioned findings, combined with their negative ε_(Hf)(t) values(-21.7 to-20.2), corresponding two-stage model age(T_(DM2)) of 2 579--2 484 Ma, as well as low MgO(1.38 wt%--1.39 wt%), Cr(18.5×10~(-6)-19.5×10~(-6)) and Ni(9.45×10~(-6)-9.46×10~(-6)) values, indicate that Baita porphyry quartz monzodiorite may be generated by partial melting of the Neoarchean-Paleoproterozoic thickened basaltic lower crust. Based on the results from this study and pre-vious regional studies, it is concluded that Baita porphyry quartz monzodiorite was spatially related to the westward subduction of the Paleo-Pacific plate.     

Detection and Attribution of Changes in Thermal Discomfort over China during 1961-2014 and Future Projections

In this study, variation in the frequency of thermal discomfort days over China during the period of 1961-2014,including heat discomfort days(HDDs) and cold discomfort days(CDDs), and the influence of external forcings on it are discussed. HDDs are the conditions of overheating and overhumidity(represented by humidity index), and CDDs reflect the dangers from cold temperatures and winds(represented by wind chill index). Observations show significant increases(decreases) in the frequency of HDDs(CDDs) over China from 1961 to 2014, with clear regional distinctions. The historical ALL and greenhouse gas(GHG) simulations can sufficiently reproduce the spatial patterns of the observational trend in the frequency of both HDDs and CDDs over China. Further, the impacts of GHG and anthropogenic forcings on the HDDs(CDDs) are detectable over China, except for central and eastern China, based on the optimal fingerprinting method. GHG forcing is identified as a dominant factor for the observational changes in the frequency of HDDs over southern China;GHG and anthropogenic forcings have dominant effects on the variation in the frequency of CDDs over southwestern China. Although trends in the frequency of HDDs and CDDs in historical aerosol forcing simulations seems to be opposite to observations, an aerosol signal fails to be detected. Natural forcing contributes to the observational variation in the frequency of HDDs over northwestern China. In addition, the future projections of thermal discomfort days indicate that Chinese residents will face more threats of heat discomfort and fewer threats of cold discomfort in the future under global warming.     

对2021年华南夏季降水预测成败的分析

基于国内外动力模式和诊断分析，分析了2021年华南夏季降水预测的成功和不足。结果表明：(1)2021年夏季西太平洋副热带高压偏大偏强，水汽输送较弱；西太平洋和南海生成的台风较少，登陆及影响华南的台风偏弱。综合影响导致2021年夏季华南降水偏少25%以上。(2)2021年华南夏季降水实况与2021年3和4月两次预测存在较大差异，主要表现为动力模式对副高脊线和西伸脊点位置以及东亚大槽的预报与实况存在较大差异；物理因子诊断分析预测中大部分信号指示2021年华南夏季降水偏多的可能性较大，与实况相差较大。     

2022年2月广东降水异常偏多特征及成因分析

为了分析广东省2022年2月降水异常的成因，基于1951—2022年广东省86个国家气象站逐日降水资料、1991—2022年NCEP/NCAR再分析资料和中国气候系统监测指数集数据，采用相关分析、合成分析等方法研究了2022年2月广东降水异常偏多的原因。结果表明：2月广东降水异常偏多2.7倍，为20世纪90年代以来最多；18—22日出现罕见冬季暴雨过程，20日全省平均日雨量打破2月历史极值。厄尔尼诺和拉尼娜事件对次年广东2月降水的影响基本反相，厄尔尼诺(拉尼娜)次年，菲律宾上空为反气旋性(气旋性)环流异常，其西北侧的西南风(东北风)将海洋(陆地)湿(干)空气输送至广东上空，使广东大部降水偏多(少)。在拉尼娜次年时，若2月青藏高原高度场异常偏低，有利于高原南侧的印缅槽偏强，则广东省2月降水偏多；若2月青藏高原高度场略偏低，则广东省2月降水以偏少为主。2022年2月广东降水异常偏多，与典型拉尼娜次年的影响不同，但同期青藏高原高度场异常偏低，说明拉尼娜背景并不是导致该次广东降水异常偏多的原因，青藏高原高度场异常偏低则是导致广东2022年2月降水异常偏多的主要原因。     

The Middle Assemblages of Fluid Inclusions Characteristics and Significance of Dolomite in Majiagou Formation in Ordos Basin, China

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