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

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Science china Earth sciences 2006年第S2期49卷 47-62页

作者： ZHANG Leiming, YU Guirui, SUN Xiaomin, WEN Xuefa, REN Chuanyou, SONG Xia, LIU Yunfen, GUAN Dexin, YAN Junhua & ZHANG Yiping Synthesis center of chinese Ecosystem {2. Network (CERN), Institute of Geographic sciences and Natural Resources {2., chinese academy of sciences, beijing 100101, china Institute of applied Ecology, chinese academy of sciences, Shenyang 110016, china South china Institute of Botany, chinese academy of sciences, Guangzhou 510650, china Xishuangbanna Tropical Botanical Garden, chinese academy of sciences, Kunming 6502.3, china Graduate University of chinese academy of sciences, beijing 100049, china Synthesis center of chinese Ecosystem {2. Network (CERN) Institute of Geographic Sciences and Natural Re-sources Research Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China Institute of applied Ecology Chinese Academy of Sciences Shenyang China South china Institute of Botany Chinese Academy of Sciences Guangzhou China Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences Kunming 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 2.03, 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 -32..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 t

关键词： forest transect carbon budget ecosystem photosynthesis ecosystem respiration china-FLUX eddy covariance.

A comparative study on 3-D solar wind structure observed by Ulysses and MHD simulation

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Science Bulletin 2005年第7期50卷 672-678页

作者： FENG Xueshang, XIANG Changqing, ZHONG Dingkun & FAN Quanlin SIGMA Weather Group, Key Laboratory of space Weather Key Labo- ratory of Geospace Environment and Geodesy, Ministry of Education, {2. for space Science and applied research, chinese academy of sciences, beijing 100080, china SIGMA Weather Group Key Laboratory of Space Weather Beijing China Key Labo-ratory of Geospace Environment and Geodesy Ministry of Education Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China

During Ulysses’ first rapid pole-to-pole transit from September 1994 to June 1995, its observations showed that middle- or high-speed solar winds covered all latitudes except those between ?2.° and +2.° near the ecliptic plane, where the velocity was 300―450 km/s. At poleward 40°, however, only fast solar winds at the speed of 700―870 km/s were observed. In addition, the transitions from low-speed wind to high-speed wind or vice versa were abrupt. In this paper, the large-scale structure of solar wind observed by Ulysses near solar minimum is simulated by using the three-dimensional numerical MHD model. The model com- bines TVD Lax-Friedrich scheme and MacCormack II scheme and decomposes the calculation region into two re- gions: one from 1 to 2. Rs and the other from 18 Rs to 1 AU. Based on the observations of the solar photospheric magnetic field and an addition of the volumetric heating to MHD equations, the large-scale solar wind structure mentioned above is reproduced by using the three-dimensional MHD model and the numerical results are roughly consistent with Ulysses’ observations. Our simulation shows that the initial magnetic field topology and the addition of volume heating may govern the bimodal structure of solar wind observed by Ulysses and also demonstrates that the three-dimensional MHD numerical model used here is efficient in modeling the large-scale solar wind structure.

关键词： Ulysses observation solar wind structure numerical simulation.

The roles of a decision support system in applying forest ecosystem management in Northeast china

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Science china(Technological sciences) 2006年第Z1期49卷 9-18页

作者： DAI Limin, ZHENG Bofu, Guofan Shao & ZHOU Li State Key Lab of Systems Ecology, research center for Eco-Environmental {2., chinese academy of sciences, beijing 100085, china Institute of applied Ecology, chinese academy of sciences, Shenyang 110016, china Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA Graduate University of chinese academy of sciences, beijing 100101, china State Key Lab of Systems Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing China Institute of applied Ecology Chinese Academy of Sciences Shenyang China Department of Forestry and Natural Resources Purdue University West Lafayette USA Graduate University of chinese academy of sciences Beijing China

Forest ecosystems provide a variety of services and forest ecosystem management (FEM) is an effective approach to maximize the services. Because of the complexity of forest ecosystems, the applications of FEM can be facilitated with decision support systems (DSS) that recognize and incorporate ecological and socio-economic variables. With the rapid development of computation and information technologies, DSS have been advanced in many ways. Traditional forest management within a forestry unit in china is planned on a yearly basis. The planning itself remains primarily a verbal concept as there are no quantitative decision-support tools available to translate the concept into forest management actions. For the purposes of FEM at the management level, a forest management DFF, FORESTAR, has been developed under a framework of geographic information system (GIS) and forest models. The paper explained the intelligent modeling mechanisms and demonstrated how the applications of FEM can be strengthened with the applications of FORESTAR.

关键词： forest functions, forested landscapes, forest services, forest models, geographic information systems.

Correlative ionospheric disturbances in the sunlit hemisphere during the flare on July 14,2.00

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chinese Science Bulletin 2002年第12期47卷 975-977页

作者： ZHANG Donghe & XIAO ZuoDepartment of Geophysics, Peking University, beijing 100871, china Qingdao {2. center, chinese {2. Institute of Radio-wave Propagation, Qingdao 2.6071, china center for space Science and applied {2., chinese {12. o Department of Geophysics Peking University Beijing China Qingdao research center Chinese Research Institute of Radio-wave Propagation Qingdao China center for space Science and {2. research Chinese Academy of Sciences Beijing China

Using GPS data obtained from GPS sites located on the sunlit hemisphere during the flare on July 14, 2.00, the ionospheric response to the flare was analyzed. A kind of tiny correlative ionospheric fluctuations were revealed from the temporal total electron content (TEC) curves derived from GPS measurements, and the values of this kind of disturbances are about 1015 m-2. A comparative analysis of these disturbances and soft X-ray flux detected at GOES satellite during the flare is done. It is found that this kind of disturbances revealed in the temporal TEC curves did occur in a very large area of sunlit ionosphere and its behavior is mainly controlled by the characteristics of the flare’s extra radiation. Because the similar fluctuations are not found in the curve of soft X-ray flux, it is concluded that the flare extra radiation in EUV band should have corresponding fluctuations and it is the fluctuations that cause the TEC disturbances. The height, where the disturbances occur, should be in the F

关键词： GPS TEC flare correlative disturbance.

Estimation of forest volumes by integrating Landsat TM imagery and forest inventory data

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Science china(Technological sciences) 2006年第Z1期49卷 54-62页

作者： GU Huiyan, DAI Limin, WU Gang, XU Dong, WANG Shunzhong &WANG Hui Institute of applied Ecology, chinese academy of sciences, Shenyang 110016,{2. School of Forestry, Northeast Forestry University, Harbin 150040,{2. State Key Lab of Systems Ecology, research center for Eco-Environmental sciences, chinese academy of sciences, beijing 100085,{2. Graduate University of chinese academy of sciences, beijing 100039,{2. Institute of applied Ecology Chinese Academy of Sciences Shenyang China School of Forestry Northeast Forestry University Harbin China State Key Lab of Systems Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

Accurate information about forest volumes is essential for forest management planning. The survey interval of the Forest Resource Inventory of china (FRIC) is too long to meet the demand for timely decision-making required for forest protection, management, and utilization. Analysis of satellite imagery provides good potential for more frequent reporting of forest parameters. In this study, we describe an application of the k-nearest neighbors (kNN) method to Landsat TM imagery for improving estimation of forest volumes. Several spectral features were tested and compared in forest volume estimations, including normalized difference vegetation index, environmental vegetation index, and the combination of the spectral features. The combined index resulted in the most accurate volume estimations. The kNN estimator and the combined index were then used in forest volume estimation. The estimation error (RMSE) of the total volume was44.2., much lower than those for Larix forest (the RMSE was 51.7%) and those for the Korean pine and broadleaved forests (the estimation errors were over 71.7% and 88.19%,respectively). This preliminary study demonstrates the potential of forest volume estimations with remote sensing data to provide useful information for forest management if only limited ground information is available.

关键词： forest inventory, landsat TM, k-nearest neighbors, spectral extraction.

Differentiation transforming system

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Progress in Natural Science:Materials International 2009年第3期19卷 397-406页

作者： Qiang Chenga,b,c,*, Haibin Zhang d, Bin Wanga, Yonghua Zhao c a LASG, Institute of Atmospheric Physics, chinese academy of sciences, beijing 10002., PR{2. b LSEC, Institute of Computing Mathematics, chinese academy of sciences, beijing 100080, PR{2. c SC, Institute of Computer Network Information center, chinese academy of sciences, beijing 100190, PR{2. d College of applied sciences, beijing University of Technology, beijing 10012., PR{2. LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 PR China LSEC Institute of Computing Mathematics Chinese Academy of Sciences Beijing 100080 PR China SC Institute of Computer Network Information Center Chinese Academy of Sciences Beijing 100190 PR China College of applied sciences Beijing University of Technology Beijing 100124 PR China

The differentiation transforming (DFT) system is developed to produce the tangent linear codes, which is used to calculate the Jaco- bian- and the Hessian-vector products with no truncation errors. This paper first gives the introduction of the functionality and features of the DFT system, and then discusses several techniques for the implementation of automatic differentiation tools, including data depen- dence analysis, singular differentiation and code optimization. Finally, the codes generated with DFT used in several applications have been demonstrated.

关键词： Jacobian Hessian Tangent linear model Automatic differentiation

Determination of polychlorinated biphenyl congeners in environmental samples

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Journal of Environmental sciences 1996年第1期8卷 57-65页

作者： Chu Shaogang Yang Chun Xu Xiaobai (research center for Eco-Environmental {2.,chinese academy of {2., beijing 100085,china )

A modified separation method has been developed for determinating polychlorinated biphenyl congeners in environmental samples. Direct treatment of extract with concentrated HzSO4 was employed in the first step for removal of lipids and other interfering substances, then a joint column of alumina-silica gel(Ag+) was applied to separate PCBs fraction from HCH, DDT and its analogs. After this separation, the PCBs fraction was analyzed by capillary gas chromatography with ECD detector and confirmed by GC/MS. The recoveries of individual congeners in Aroclor 12.4 through the separation are about 79%-84%. The method is very efficient and useful for determination of trace amount of PCB congeners in environmental samples.

关键词： polychlorinated biphenyl capillary gas chromatography environmental samples.

Simulation studies of high-latitude magnetospheric boundary dynamics

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Science china(Technological sciences) 2004年第4期47卷 421-435页

作者： PU Zuyin1, SHI Quanqi1,3, XIAO Chijie1, FU Suiyan1, ZHANG Hui1,2. ZONG Qiugang2.& LIU Zhenxing3 1. School of Earth and space sciences, Peking University, {2. 100871, china 2. center for space Physics, Boston University, 72. Commonwealth Avenue, Boston, MA 02.15, USA 3. center for space Science and Application research, chinese academy of sciences, beijing 100080, china School of Earth and space sciences Peking University Beijing China center for space Science and Application {2. Chinese Academy of Sciences Beijing China center for space Physics Boston University Boston USA

Magnetic reconnection at the high-latitude magnetopause is studied using 2.5-dimensional Hall-MHD simulation. Concentric flow vortices and magnetic islands appear when both Hall effect and sheared flow are considered. Plasma mixing across the magnetopause occurs in the presence of the flow vortices. Reconnected structure generated in the vicinity of the subsolar point changes its geometry with increasing flow shear while moving to high latitudes. In the presence of flow shear, with the Hall-MHD reconnection a higher reconnection rate than with the traditional MHD is obtained. The out-of-plane components of flow and magnetic field produced by the Hall current are redistributed under the action of the flow shear, which makes the plasma transport across the boundaries more complicated. The simulation results provide some help in understanding the dynamic processes at the high latitude magnetopause.

关键词： magnetopause, entry layer, magnetic reconnection, vortex reconnection, Hall effect, flow shear.

MAGNETOSPHERIC PHYSICS

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空间科学学报 1998年第S1期18卷 27-38页

作者： LIU Zhen-xing(center for space Science and {2. Researeh, The chinese academy of sciences,beijing 100080)PU Zu-yin (Department of Geophysics, Peking University)

Magnetospheric physics has been one of the most active areas in chinese space {2. in past two years. The major project "Energy Transport Processes in the Solar-Terrestrial System" (1993-1997) sponsored by the National Natural Science Foundation in china (NSFC) has been successfully completed. Prestudies relevant to the key scientific engineering program "Meridian Chain at One Hundred Twenty Degree East Multi-Station and Multi-Instrument Observatory System" have started. A new key project "Study of Auroral Magnetospheric and Ionospheric Physics" (1997-1999) sponsored by the NSFC has begun. The space Active Experiment Program has been carrying on *** between chinese and international magnetospheric physicists have proceeded forward. More than 40 papers covering a variety of subjects in the magnetospheric physics were published in chinese and international academic journals. Most of these works were supported by the NSFC. This report provides a brief summary of aforementioned advances made in china in the past two years.

关键词： Magnetospheric physics Magnetopause Magnetic reconnection Substorm Magnetospheric modeling Magnetospheric waves and instabilities