Vegetation and soil carbon storage in China

This study estimated the current vegetation and soil carbon storage in China using a biogeochemical model driven with climate, soil and vegetation data at 0.5° latitude-longitude grid spatial resolution. The results indicate that the total carbon storage in China's vegetation and soils was 13.33 Gt C and 82.65 Gt C respectively, about 3% and 4% of the global total. The nationally mean vegetation and soil carbon densities were 1.47 kg C/m2 and 9.17 kg C/m2, respectively, differing greatly in various regions affected by climate, vegetation, and soil types. They were generally higher in the warm and wet Southeast China and Southwest China than in the arid Northwest China; whereas vegetation carbon density was the highest in the warm Southeast China and Southwest China, soil carbon density was the highest in the cold Northeast China and southeastern fringe of the Qinghai-Tibetan Plateau. These spatial patterns are clearly correlated with variations in the climate that regulates plant growth and soil organi     

Seasonal variation of carbon exchange of typical forest ecosystems along the eastern forest transect in China

The long-term and continuous carbon fluxes of Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical evergreen coniferous forest (QYZ), Dinghushan subtropical evergreen mixed forest (DHS) and Xishuangbana tropical rainforest (XSBN) have been measured with eddy covariance techniques. In 2003, different responses of carbon exchange to the environment appeared across the four ecosystems. At CBS, the carbon exchange was mainly determined by radiation and temperature. 0℃and 10℃were two important temperature thresholds; the former determined the length of the growing season and the latter affected the magnitude of carbon exchange. The maximum net ecosystem exchange (NEE) of CBS occurred in early summer because maximum ecosystem photosynthesis (GPP) occurred earlier than maximum ecosystem respiration (Rθ). During summer, QYZ experienced severe drought and NEE decreased significantly mainly as a result of the depression of GPP. At DHS and XSBN, NEE was higher in the drought season than the wet season, especially the conversion between carbon sink and source occurring during the transition season at XSBN. During the wet season, increased fog and humid weather resulted from the plentiful rainfall, the ecosystem GPP was dispressed. The Q10 and annual respiration of XSBN were the highest among the four ecosystems, while the average daily respiration of CBS during the growing season was the highest. Annual NEE of CBS, QYZ, DHS and XSBN were 181.5, 360.9, 536.2 and -320.0 g·C·m-2·a-1, respectively. From CBS to DHS, the temperature and precipitation increased with the decrease in latitude. The ratio of WEE/Rθincreased with latitude, while Rθ/Gpp, ecosystem light use efficiency (LUE), precipitation use efficiency and average daily GPP decreased gradually. However, XSBN usually escaped such latitude trend probably because of the influence of the south-west monsoon climate which does not affect the other ecosystems. Long-term measurement and more research were necessary to understand the adaptation of forest ecosystems to climate change and to evaluate the ecosystem carbon balance due to the complexity of structure and function of forest ecosystems.     

Carbon budgets of three temperate forest ecosystems in Dongling Mt.,Beijing,China

There is a general agreement that forest ecosystems in the Northern Hemisphere function as signifi-cant sinks for atmospheric CO2; however, their magnitude and distribution remain large uncertainties. In this paper, we report the carbon (C) stock and its change of vegetation, forest floor detritus, and mineral soil, annual net biomass increment and litterfall production, and respiration of vegetation and soils between 1992 to 1994, for three temperate forest ecosystems, birch (Betula platyphylla) forest, oak (Quercus liaotungensis) forest and pine (Pinus tabulaeformis) plantation in Mt. Dongling, Beijing, China. We then evaluate the C budgets of these forest ecosystems. Our results indicated that total C density (organic C per hectare) of these forests ranged from 250 to 300 t C ha-1, of which 35―54 t C ha-1 from vegetation biomass C and 209―244 t C ha-1 from soil organic C (1 m depth, including forest floor detritus). Biomass C of all three forests showed a net increase, with 1.33―3.55 t C ha-1 a-1 during the study period. Litterfall production, vegetation autotrophic respiration, and soil heterotrophic respira-tion were estimated at 1.63―2.34, 2.19―6.93, and 1.81―3.49 t C ha-1 a-1, respectively. Ecosystem gross primary production fluctuated between 5.39 and 12.82 t C ha-1 a-1, about half of which (46%―59%, 3.20―5.89 t C ha-1 a-1) was converted to net primary production. Our results suggested that pine forest fixed C of 4.08 t ha-1 a-1, whereas secondary forests (birch and oak forest) were nearly in balance in CO2 exchange between the atmosphere and ecosystems.     

Hydro-climatic variability and forest fires in Mexico’s northern temperate forests

Global warming is likely modifying the hydrological cycle of forested watersheds. This report set as objectives to: a) assess the hydrological variables interception loss, I, potential and actual evapo-transpiration, E, Et, runoff, Q, and soil moisture content, θ; b) evaluate whether these variables are presenting consistent trends or oscillations that can be associated to global warming or climate variability; and c) relate θ to the number of wildfires and the burned area in Durango, Mexico. A mass balance approach estimated daily variables of the water cycle using sub-models for I and Et to calculate Q and θ for a time series from 1945 to 2007. Regression and auto-regressive and moving averaging (ARIMA) techniques evaluated the statistical significance of trends. The cumulative standardized z value magnified and ARIMA models projected statistically similar monthly and annual time series data of all variables of the water cycle. Regression analysis and ARIMA models showed monthly and annual P, I, E, and Et, Q, and θ do not follow consistent up or downward linear tendencies over time with statistical significance; they rather follow oscillations that could be adequately predicted by ARIMA models (r² ≥ 0.70). There was a consistent statistical association (p ≤ 0.05) of θ with the number of wildfires and the area burned regardless of the different spatial scales used in evaluating these variables. The analysis shows seasonal variability is increasing over time as magnifying pulses of dryness and wetness, which may be the response of the hydrological cycle to climate change. Further research must center on using longer time series data, testing seasonal variability with additional statistical analysis, and incorporating new variables in the analysis.     

Characteristics of China’s oil and gas pool formation in latest geological history

1 Introduction China’s continent is a mountain-building zone made up of numerous micro-continental blocks and mini- continental blocks[1,2]. The continent has been sub- jected to the processes and evolution of three continual geodynamic systems of Paleo-Asia Ocean, Pa- leo-Tethys Ocean and Pacific Ocean[3]. The structural framework of China’s continent had been gradually finalized in the Neogene-Quaternary period owing to the India-Eurasia collision and its continuous com- pression[3], …     

A classification scheme for Earth’s critical zones and its application in China

As the thin layer at the Earth's terrestrial surface, the critical zone(CZ) ranges from the vegetation canopy to the aquifer or the interface between saprolite and bedrock and varies greatly in space. In the last decade, much attention has been paid to the establishment of Critical Zone Observatories(CZOs) that focus on various aspects of CZ science over different time scales. However, to the best of our knowledge, few studies have explicitly contributed to CZ classification or regionalization;thus, the spatial patterns of similar CZs have not been clearly identified. This study proposed a three-category CZ classification scheme by integrating environmental factors that greatly affect the transfer of energy and mass in the Earth's near-surface environment and thus dominate CZ formation and evolution, i.e., climate, parent material, soil type, groundwater table depth,geomorphology and land use. The main goal was to highlight the zonality of these driving forces, of which the high-category classification units were overlaid to delineate the CZ boundaries. The CZ regionalization of China was performed as a case study,resulting in 44 major regions(1 st category), 100 submajor regions(2 nd category) and 1448 regions(3 rd category). The spatial distributions and driving factors of the ten largest regions were identified, followed by a simple comparison of the CZO network.Then, the proposed CZ regionalization was compared with recent studies on regionalization in China to evaluate its successes and weaknesses. By linking together CZ studies from the last decade, we advocate that a theoretical framework integrating the CZ evolution processes with ecological functions acts as one of the frontiers of CZ science. Our study demonstrates that the proposed three-category CZ classification scheme effectively identifies the spatial variations in CZs and could thus be further applied in other areas to advance terrestrial environmental research and provide decision support for the sustainable management of natural resources.     

China’s component borehole strainmeter network

In 2004,China’s digital seismic observation network project began to deploy 40 sets YRY-4 four-component borehole strainmeters in order to monitor earthquake preparation process.The paper describes observed solid tidal strain discreteness and tidal factor anisotropy,analyzes the reliability of observational data and discusses the cause for this phenomenon.After getting rid of interferences,the network,in two years practice,has observed several pre-seismic strain anomalies at stations close to epicenters esp...     

Overview of the development history of China’s typhoon research and operational work in the past century

Because typhoons are one of the most major natural disasters in the southeastern coastal areas of China,great attention has been paid to the prevention and mitigation of the disasters caused by typhoons.Over the past century,significant progress has been made in typhoon-related scientific research and operational work in China,including the construction of a network of typhoon monitoring stations,the establishment of forecasting operation systems,early warning and prevention of typhoon-related disasters,and the research of basic theories of typhoon behaviors and key forecasting technologies.This paper briefly reviews the milestones in the development history of typhoon research in China over the past century and a half in order to commemorate the predecessors,especially those who made historical contributions to the advancement of typhoon research since the economic and cultural reforms known as the"Opening of China",who provided historical references which enabled China to become an international leader in the field of typhoon science and technology.     

Patterns and trajectories of macrophyte change in East China’s shallow lakes over the past one century

Macrophytes play important roles in maintaining ecosystem health and stability of shallow lakes. Better understanding of their long-term dynamics has important theoretical and practical significance for both lake ecosystem restoration and eutrophication control. However, the knowledge about the historical status and changing patterns of macrophytes in China's shallow lakes is still controversial and lacks systematic research. Here, we reviewed and synthesized the published records of submerged macrophytes from 14 typical shallow lakes in the eastern plain covering the past 100 years. The results suggest that submerged macrophytes have experienced three clear stages of change: rare period(the 1900 s–the 1950 s), growth period(the1950 s–the 1980 s), and recession period(the 1980 s–now). This finding is different from the traditional understanding that submerged macrophytes were abundant in the early 20 th century and have been degrading since then. On this basis, we proposed the possible evolution pattern(less-more-less) of submerged macrophytes in the eastern plain lake region over the past 100 years,which provides new perspectives about the long-term evolution process of macrophytes in shallow lakes. Furthermore, we found that the decline of submerged macrophytes during the regime shift shows a gradual process at the interdecadal scale; this finding contradicts the classical regime shift theory that macrophytes decline sharply during the critical transition. This study has important theoretical value for the restoration of the eastern plain lakes in China from "turbid lake" to "clear lake", especially for establishing the historical reference condition and restoration path of macrophytes.     

Features of different types of seismic events in China’s Capital Region

Seismic records produced by different seismic sources vary. In this study, we compared the waveform records and time-frequency characteristics of tectonic earthquakes, artificial explosions, and mine collapses in China’s Capital Region. The results show that tectonic earthquakes are characterized by stronger S-wave energy than P-wave energy, obvious high-frequency components, and wide frequency bands of P and S waves. Artificial explosions are characterized by greater P-wave amplitude than S-wave amplitude and near-station surface wave development. Mine collapses are characterized by lower overall frequency, more obvious surface waves, and longer duration. We extracted quantitative discriminants based on the analysis of different event records, with 31 feature values in 7 categories (P/S maximum amplitude ratio, high/low frequency energy ratio, P/S spectral ratio, corner frequency, duration, the second-order moment of spectrum, and energy strongest point). A comparison of the ability of these feature values to recognize distinct events showed that the 6–17 Hz P/S spectral ratio was able to completely distinguish artificial explosions from the other two types of events. The S-wave corner frequency performed relatively well in identifying all three types of events, with an accuracy of over 90%. Additionally, a support vector machine was used to comprehensively distinguish multiple features, with an accuracy for all three types of events reaching up to 100%.     

CO_2 flux evaluation over the evergreen coniferous and broad-leaved mixed forest in Dinghushan, China

The Dinghushan flux observation site, as one of the four forest sites of ChinaFLUX, aims to acquire long-term measurements of CO2 flux over a typical southern subtropical evergreen coniferous and broad-leaved mixed forest ecosystem using the open path eddy covariance method. Based on two years of data from 2003 to 2004, the characteristics of temporal variation in CO2 flux and its response to environmental factors in the forest ecosystem are analyzed. Provided two-dimensional coordinate rotation, WPL correction and quality control, poor energy-balance and underestimation of ecosystem respiration during nighttime implied that there could be a CO2 leak during the nighttime at the site. Using daytime (PAR > 1.0μmol-1·m-2·s-1) flux data during windy conditions (u* > 0.2 m·s-1), monthly ecosystem respiration (Reco) was derived through the Michaelis-Menten equation modeling the relationship between net ecosystem CO2 exchange (NEE) and photosynthetically active radiation (PAR). Exponential function was employed to describe the relationship between Reco and soil temperature at 5 cm depth (Ts05), then Reco of both daytime and nighttime was calculated respectively by the function. The major results are: (i) Derived from the Michaelis-Menten equation, the apparent quantum yield (α) was 0.0027±0.0011 mgCO2·μmol-1 photons, and the maximum photosynthetic assimilation rate (Amax) was 1.102±0.288 mgCO2·m-2·s-1. Indistinctive seasonal variation of o or Amax was consistent with weak seasonal dynamics of leaf area index (LAI) in such a lower subtropical evergreen mixed forest. (ii) Monthly accumulated Reco was estimated as 95.3±21.1 gC·m-2 mon-1, accounting for about 68% of the gross primary product (GPP). Monthly accumulated NEE was estimated as -43.2±29.6 gC·m-2·mon-1. The forest ecosystem acted as carbon sink all year round without any seasonal carbon efflux period. Annual NEE of 2003 and 2004 was estimated as -563.0 and -441.2 gC·m-2·a-1 respectively, accounting for about 32% of GPP.     

Inertial effects in the Earth’s crust and magnetosphere

A review of studies devoted to the problem of exciting magnetic signals in the crust associated with the formation of the major rupture in an earthquake source and with the propagation of seismic waves was given in [Sgrigna et al., 2004]. However, this review contains incorrect citations from original papers and several erroneous statements concerning inertial and inductive mechanisms of conversion of the energy of rock motion into magnetic field energy. These mistakes are analyzed in the present paper. The formal and physical similarity between seismomagnetic waves in the crust and Alfvén waves in the magnetosphere is used in the analysis. A comparative analysis of the inertial and inductive mechanisms of seismomagnetic field generation is performed. The Cherenkov criterion of Alfvén wave generation due to the ionospheric effect of acoustic waves from earthquakes and explosions is derived. Attention is also given to nonlinear phenomena (nonlinearity of a mechanomagnetic conversion in the crust and anharmonicity and self-focusing of Alfvén waves in the magnetosphere).     

Luminescence of Molecular Nitrogen Bands in the Earth’s Atmosphere during the Precipitation of High-Energy Electrons

Geomagnetism and Aeronomy - The luminescence-intensity profiles of the bands of the first and second positive systems of molecular nitrogen were calculated for the case of the precipitation of...     

Spatiotemporal evolution and driving factors of China’s flash flood disasters since 1949

This study examines the spatiotemporal evolution of China’s flash flood disasters (FFDs) since 1949 and explores driving factors affecting the spatial distribution of historical FFDs. Records of more than 60000 FFDs are examined, and the centroid comparison method is used to reveal the spatiotemporal evolution of FFDs from 1951 to 2015. In particular, the geographical locations of the centroids, degrees of aggregation, and associated movement tendencies are examined to conduct a preliminary analysis of correlations between rainfall, population, and the spatiotemporal evolution of FFDs. Subsequently, using relevant data from 2000 to 2015, three factors relating to FFDs in natural watershed units include namely rainfall, human activity, and the environment of the Earth’s surface. The geographical detector method is then employed to explore the effect of these driving factors on the spatial distribution of FFDs. Analysis results show that displacement of the spatial distribution of FFDs since 1949 is correlated with variations in rainfall and population distribution. In addition, it is determined that the distribution of FFDs occurring between 2000 and 2015 have regional differentiation characteristics. However, the effect of rainfall on the distribution of FFDs is more significant than that of human activity or the environment of the Earth’s surface, but interactions occur between these latter two factors in disaster-formative environments. Furthermore, results also show that the driving factors of FFDs have significant spatiotemporal heterogeneity. In China, regions at high risk of FFDs include the Sichuan-Chongqing ecological zone, the South China ecological zone, the Yunnan-Guizhou Plateau, and the middle and lower reaches of the Yangtze River, while regions with a low risk of FFDs include the Northwest China arid zone, Qinghai-Tibet Plateau, Inner Mongolian Plateau, and the Northeast China ecological zone. These findings support further studies investigating disaster-formative environments, facilitate FFD risk zoning, and provide a scientific basis for plans to effectively prevent and control FFDs.     

Temporal vP/vS variation characteristics in different zones of China’s Capital Circle area before and after Wen’an earthquake

On July 4, 2006, an earthquake of MS5.1 took place in Wen’an, Hebei Province, just at the south center of China’s Capital Circle area digital seismograph network. It is the strongest event recorded ever since the network went into operation in 2002. We processed the vast amounts of phase data yielded by the 107 digital seismic stations between 2002~2007 using Wadati method. In order to improve the precision and stability of shear and compressional wave velocities (vP/vS) calculation, we impose a number of r...     

Introduction to China’s Earthquake Emergency Response System

Following the M_S6.4 earthquake that occurred on May 21, 2021 in Yangbi, Yunnan, China, the earthquake emergency response system (EERS) responded immediately. The real-time software delivered many seismic parameters that provided a preliminary assessment of the earthquake. The 24-hour on-duty staff and scientific researchers revised these parameters and produced more detailed reports to understand the cause of the earthquake and the potential damage, which provided valuable information for emergency rescue operations and earthquake situation assessment. Emergency personnel were dispatched immediately to the earthquake site to observe the aftershocks, investigate the damage, and guide and assist in the relief efforts. This paper describes the EERS response to the Yangbi earthquake to demonstrate the characteristics of the system and discuss the potential for further improvement.     

Temporal vP/vS variation characteristics in different zones of China’s Capital Circle area before and after Wen’an earthquake

On July 4, 2006, an earthquake of MS5.1 took place in Wen’an, Hebei Province, just at the south center of China’s Capital Circle area digital seismograph network. It is the strongest event recorded ever since the network went into operation in 2002. We processed the vast amounts of phase data yielded by the 107 digital seismic stations between 2002~2007 using Wadati method. In order to improve the precision and stability of shear and compressional wave velocities (vP/vS) calculation, we impose a number of restrictions on the computation environment and condition, e.g., the earthquakes are densely concentrated, selected stations are limited in range, the number of stations in- volved in the computation is larger than 5 and linear fitting features high precision and small error. Under these restrictions, the study shows that vP/vS in and around Wen’an and Tangshan underwent a normal-low-normal proc- ess one year before Wen’an earthquake, vP/vS became obviously low and the low ratio lasted for about one year, meanwhile, little variation of vP/vS was seen in Xingtai, northwest of Beijing, southwest of Beijing, Beijing-Tianjin and Beijing; after the quake, the vP/vS returned normal in Wen’an and Tangshan. Error and stability analysis of the calculated result for vP/vS shows it is convincible that anomaly appeared in and around Wen’an and Tangshan be- fore Wen’an earthquake.     

Mangshan loess on China’ s Central Plain and its response to tectonic movement and climate*

The Mangshan loess on China’s Central Plain, located on the transitional zone between the uplifting Loess Plateau and the subsiding North China Plain, is a proximal sandy loess transported from the fanhead of alluvial fan in the lower reaches of the Yellow River and has recorded the coupling effect of the tectonics and climate over the last 200 ka. An abrupt environmental change indicated by the abrupt rise of deposit rate in the late penultimate glaciation, about 150 ka BP, took place; that is, the Yellow River downcut and moved eastwards through the Sanmenxia Gorge and transported abundant materials from the Loess Plateau to form paleosol S1 with a thickness of 15.7 m and loess L1 with a thickness of 77.3 m. The loess-paleosol sequence at Mangshan has not only recorded detailed climate responses of this area to the East Asian monsoon, but also reflects the tectonogenetic environmental effect caused by the trunk stream of the Yellow River cutting through Sanmenxia Gorge into sea. Project supported by the National Natural Science Foundation of China (Grant No..49572132).     

ZHANG Heng’s Seismometer and Longxi earthquake in AD 134

Introduction Houhan Shu?ZHANG Heng Biography written by FAN Ye(AD398?AD445,South-North Dynasties)described about the response of ZHANG Heng’s Seismometer to Longxi earthquake as follows.“On one occasion a dragon dropped a ball without an earthquake being felt.All the scholars in the capital blamed this effect happening without any feelings of the earthquake.Several days later,a messenger arrived reporting that an earthquake really had taken place at Longxi.There-upon people all a…     

Responses of water use efficiency to phenology in typical subtropical forest ecosystems——A case study in Zhejiang Province

Ecosystem-scale water-use efficiency(WUE) is an important indicator for understanding the intimately coupled relationship between carbon and water cycles in ecosystems. Previous studies have suggested that both abiotic and biotic factors have significant effects on WUE in forest ecosystems. However, responses of WUE to phenology in the context of climate change remain poorly understood. In this study, we analyzed the sensitivity and response patterns of seasonal WUE to phenology in Zhejiang Province where typical subtropical forest ecosystems are located, and discussed potential causes of the changes of the sensitivity and response patterns along different climate gradient during 2000–2014. The results of interannual partial correlation analysis showed widespread negative correlations between WUE and the start of growing season(SOS) in spring. This is because the increase in gross primary product(GPP) is larger than that of evapotranspiration(ET), resulting from an advanced SOS. The positive correlation between WUE and SOS was widely observed in summer mainly because of water stress and plant ecological strategy. The autumn WUE enhanced with the delay in the end of growing season(EOS)mainly because of the increase in GPP meanwhile the decrease or steadiness in ET, resulting from a delayed EOS. In space, the sensitivity of spring WUE to SOS significantly decreased along the radiation gradient, which might be related to strong soil evaporation in high radiation area;the sensitivity of WUE to SOS in summer showed a positive correlation with precipitation and a negative correlation with temperature, respectively, which might be attributed to the compensation of GPP to the delayed SOS and water stress caused by high temperature. The sensitivity of WUE to EOS increased significantly along the radiation and precipitation gradients in autumn, which may be because the increase of radiation and precipitation provides more water and energy for photosynthesis.