Life in extreme environments: Approaches to study life-environment co-evolutionary strategies     

XIAO Xiang  ZHANG Yu 《中国科学:地球科学(英文版)》2014,57(5):869-877

The term"extreme environments"describes the conditions that deviate from what mesophilic cells can tolerate.These conditions are"extreme"in the eye of mankind,but they may be suitable or even essential living conditions for most microorganisms.Hyperthermophilic microorganisms form a branch at the root of the phylogenetic tree,indicating that early life originated from extreme environments similar to that of modern deep-sea hydrothermal vents,which are characterized by high-temperature and oxygen-limiting conditions.During the inevitable cooling and gradual oxidation process on Earth,microorganisms developed similar mechanisms of adaptation.By studying modern extremophiles,we may be able to decode the mysterious history of their genomic evolution and to reconstruct early life.Because life itself is a process of energy uptake to maintain a dissipative structure that is not in thermodynamic equilibrium,the energy metabolism of microorganisms determines the pathway of evolution,the structure of an ecosystem,and the physiology of cells."Following energy"is an essential approach to understand the boundaries of life and to search for life beyond Earth.  相似文献   

Soil phosphorus bioavailability assessed by XANES and Hedley sequential fractionation technique in a glacier foreland chronosequence in Gongga Mountain,Southwestern China   总被引：2，自引：0，他引：2  

YanHong Wu  Jörg Prietzel  Jun Zhou  HaiJian Bing  Ji Luo  Dong Yu  ShouQin Sun  JianHong Liang  HongYang Sun 《中国科学:地球科学(英文版)》2014,57(8):1860-1868

The primary productivity of terrestrial ecosystems is influenced by soil phosphorus bioavailability, which depends largely on chemical fractions of phosphorus. The sequential fractionation technique developed by Hedley et al. or its subsequent modification is a well-known method to determine soil phosphorus forms. Hedley sequential fractionation technique separates the phosphorus into fractions based on their different chemical solubilities in extractants with certain chemical properties. Recently, synchrotron-based X-ray absorption near edge structure (XANES) spectroscopy has been employed to measure soil phosphorus species directly and non-invasively. The XANES method provides information concerning local structure and chemical information of target elements at a molecular level. Thus, it can distinguish phosphorus fractions bound by metal oxides or hydroxides (such as Fe, Al, and Ca). In this present work, the phosphorus speciation of topsoil along a glacial foreland chronosequence in Gongga Mountain is determined using these two methods. The changes in soil phosphorus bioavailability along the 120-year-old chronosequence are assessed based on comparisons of the results obtained by these two methods. The results indicate that Hedley sequential fractionation technique shows a greater ability to determine soil bioavailable phosphorus (Resin-P and NaCHO₃-P), while XANES is effective in distinguishing phosphorus bound by metal compounds. In the chronosequence, Ca- and Al-bound phosphorus were derived mainly from primary minerals, whose phosphorus contents decreased within 120 years of moraine weathering and soil development. The content of soil bioavailable phosphorus increased rapidly after 30 years since deglaciation. The increasing phosphorus bioavailability promoted the colonizing and primary succession vegetation.  相似文献   

A climatic dataset of ocean vertical turbulent mixing coefficient based on real energy sources     

Yu Zhang  YiHua Lin  RuiXin Huang 《中国科学:地球科学(英文版)》2014,57(10):2435-2446

Using data on wind stress, significant height of combined wind waves and swell, potential temperature, salinity and seawater velocity, as well as objectively-analyzed in situ temperature and salinity, we established a global ocean dataset of calculated wind- and tide-induced vertical turbulent mixing coefficients. We then examined energy conservation of ocean vertical mixing from the point of view of ocean wind energy inputs, gravitational potential energy change due to mixing (with and without artificially limiting themixing coefficient), and K-theory vertical turbulent parameterization schemes regardless of energy inputs. Our research showed that calculating the mixing coefficient with average data and artificial limiting the mixing coefficient can cause a remarkable lack of energy conservation, with energy losses of up to 90% and changes in the energy oscillation period. The data also show that wind can introduce a huge amount of energy into the upper layers of the Southern Ocean, and that tidesdo so in regions around underwater mountains. We argue that it is necessary to take wind and tidal energy inputs into account forlong-term ocean climate numerical simulations. We believe that using this ocean vertical turbulent mixing coefficient climatic dataset is a fast and efficient method to maintain the ocean energy balance in ocean modeling research.  相似文献   

A 30 meter land cover mapping of China with an efficient clustering algorithm CBEST     

LuanYun Hu  YanLei Chen  Yue Xu  YuanYuan Zhao  Le Yu  Jie Wang  Peng Gong 《中国科学:地球科学(英文版)》2014,57(10):2293-2304

Remote sensing based land cover mapping at large scale is time consuming when using either supervised or unsupervised classification approaches. This article used a fast clustering method—Clustering by Eigen Space Transformation(CBEST) to produce a land cover map for China. Firstly, 508 Landsat TM scenes were collected and processed. Then, TM images were clustered by combining CBEST and K-means in each pre-defined ecological zone(50 in total for China). Finally, the obtained clusters were visually interpreted as land cover types to complete a land cover map. Accuracy evaluation using 2159 test samples indicates an overall accuracy of 71.7% and a Kappa coefficient of 0.64. Comparisons with two global land cover products(i.e., Finer Resolution Observation and Monitoring of Global Land Cover(FROM-GLC) and GlobCover 2009) also indicate that our land cover result using CBEST is superior in both land cover area estimation and visual effect for different land cover types.  相似文献   

A τ_c magnitude estimation of the 20 April 2013 Lushan earthquake,Sichuan, China     

PENG ChaoYong  YANG JianSi  ZHENG Yu  JIANG XuDong  XU ZhiQiang  GAO Yu 《中国科学:地球科学(英文版)》2014,(12)

A crucial part of proposed earthquake early warning systems is a rapid estimate for earthquake magnitude.Most of these methods are focused on the first part of the P-wave train,the earlier and less destructive part of the ground motion that follows an earthquake.A method has been proposed by using the period of the P-wave to determine the magnitude of a large earthquake at local distance,and a specific relation for the Sichuan region was calibrated according to acceleration records of Wenchuan earthquake.The Mw 6.6 earthquake hit Lushan County,Sichuan,on April 20,2013 and the largest aftershocks provide a useful dataset to validate the proposed relation and discuss the risks connected to the extrapolation of magnitude relations with a poor dataset of large earthquake waveforms.A discrepancy between the local magnitude(ML)estimated by means ofτc evaluation and the standard ML(6.4 vs.7.0)suggests using caution when ML vs.τc calibrations do not include a relevant dataset of large earthquakes.Effects from large residuals could be mitigated or removed by introducing selection rules onτc function,by regionalizing the ML vs.τc function in the presence of significant tectonic or geological heterogeneity,and by using probabilistic and evolutionary methods.  相似文献   

A Comparative Study on Nitrogen and Phosphorus Concentration Characteristics of Twelve Riparian Zone Species from Upstream of Hunhe River          下载免费PDF全文

Shuai Yu  Wei Chen  Xingyuan He  Zhouli Liu  Hong Song  Yin Ye  Yanqing Huang  Lian Jia 《洁净——土壤、空气、水》2014,42(4):408-414

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A new look at the alkalinity of the Sea of Japan     

P. Ya. Tishchenko  G. Yu. Pavlova  E. M. Shkirnikova 《Oceanology》2012,52(1):21-33

The most important feature of the distribution of the alkalinity and calcium in the Sea of Japan—the increase in the potential alkalinity with depth under the conditions when the waters are supersaturated in relation to calcium carbonate—is considered. It is demonstrated that this fact cannot be accounted for by the reaction of the formation-dissolution of calcium carbonate. A new concept explaining the alkalinity distribution in the sea is proposed. According to it, the biological pump is the basic process responsible for the alkalinity transport from the euphotic layer into the interior of the sea. Photosynthesis is the driving force for this process. The role of the active element transporting the alkalinity is not calcium carbonate, as has been claimed elsewhere, but extracellular polysaccharides (EPSs) produced by phytoplankton. EPSs bind to calcium and other cations to form transparent exopolymer particles (TEPs). The proposed conception makes it possible to explain the following: (a) the vertical flux of calcium carbonate that is independent of the super-saturation—undersaturation state of the ambient water regarding calcium carbonate; (b) the existence of the calcium carbonate flux regardless of the nature of the plankton skeletons; (c) the nonstoichiometric ratio between the alkalinity and calcium fluxes.  相似文献   

The geochemistry of deepwater particulate matter over the hydrothermal field at 9°d50′ N (the East Pacific Rise)     

V. N. Lukashin  L. L. Demina  V. V. Gordeev  V. Yu. Gordeev 《Oceanology》2012,52(2):271-283

The results of geochemical studies of particulate matter in the water mass over the hydrothermal field at 9°50′ N on the East Pacific Rise are presented. The particulate matter was tested in background waters, in the buoyant plume, and in the near-bottom waters. The contents of Si, Al, P, C_org, Fe, Mn, Cu, Zn, Ni, Co, As, Cr, Cd, Pb, Ag, and Hg were determined. No definite correlations were found between the ele-ments in the background waters. Many of the chemical elements correlated with Fe and associated with its oxyhydroxides in the buoyant plume. In the near-bottom waters, microelements are associated with Fe, Zn, and Cu (probably, to their sulfides formed under fluid mixing with seawater). The matter precipitated in a sed-imentation trap was similar to the near-bottom particulate matter in the elemental composition.  相似文献   

Interference of the mechanisms of influence that weak extremely low-frequency electromagnetic fields have on the human body and animals     

V. S. Martynyuk  Yu. V. Tseyslyer  N. A. Temuryants 《Izvestiya Atmospheric and Oceanic Physics》2012,48(8):832-846

This review is devoted to the problem of interference between the mechanisms of biological action of natural and artificial electromagnetic fields (EMFs) for different levels of the organization of life. We discuss the problem of specific and nonspecific responses of the human body and animals to the action of EMFs on cellular and organismal levels.  相似文献   

A three-dimensional water quality model and its application to Jiaozhou Bay, China     

张燕  孙英兰  余静  袁道伟  张瑞瑾 《中国海洋工程》2012,26(4):669-684

A three-dimensional coupled physical and water quality model was developed and applied to the Jiaozhou Bay to study water quality involving nutrients, biochemical oxygen demand, dissolved oxygen, and phytoplankton that are closely related to eutrophication process. The physical model is a modified ECOM-si version with inclusion of flooding/draining processes over the intertidal zone. The water quality model is based on WASP5 which quantifies processes governing internal nutrients cycling, dissolved oxygen balance and phytoplankton growth. The model was used to simulate the spatial distribution and the temporal variation of water quality in the Jiaozhou Bay for the period of May 2005 to May 2006. In addition, the effect of reduction of riverine nutrients load was simulated and evaluated. The simulated results show that under the influence of nutrients discharged from river, the concentrations of nutrients and phytoplankton were higher in the northwest and northeast of the bay, and decreased from the inner bay to the outer. Affected by strong tidal mixing, the concentrations of all state variables were vertically homogeneous except in the deeper regions where a small gradient was found. Obvious seasonal variation of phytoplankton biomass was found, which exhibited two peaks in March and July, respectively. The variation of riverine waste loads had remarkable impact on nutrients concentration in coastal areas, but slightly altered the distribution in the center of the bay.  相似文献