Frontiers of Earth Science

ISSN 2095-0195

ISSN 2095-0209(Online)

CN 11-5982/P

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, Volume 10 Issue 4

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RESEARCH ARTICLE
Interactive effects of carbon dioxide, low temperature, and ultraviolet-B radiation on cotton seedling root and shoot morphology and growth
David BRAND,Chathurika WIJEWARDANA,Wei GAO,K. Raja REDDY
Front. Earth Sci.. 2016, 10 (4): 607-620.  
https://doi.org/10.1007/s11707-016-0605-0

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Interactive effects of multiple environmental stresses are predicted to have a negative effect on cotton growth and development and these effects will be exacerbated in the future climate. The objectives of this study were to test the hypothesis that cotton cultivars differ in their responses to multiple environmental factors of (CO2) [400 and 750 µmol·mol−1 (+(CO2)], temperature [28/20 and 20/12°C (−T)], and UV−B radiation [0 and 10 kJ·m−2·d−1 (+UV−B)]. A genetic and molecular standard (TM-1) and three modern cotton cultivars (DP1522B2XF, PHY496W3R, and ST4747GLB2) were grown in eight sunlit, controlled environment chambers with control treatment 400 µmol·mol−1 [CO2], 28/21°C temperature, and 0 kJ UV−B. The results showed significant differences among the cultivars for most of the shoot and root parameters. Plants grown under low temperature alone or as a combination with+UV−B treatment caused more detrimental effects on root and shoot vigor. Although the elevated CO2 treatments weakened the damaging effects of higher UV−B levels on cotton growth on all cultivars, increased CO2 could not mask the negative effects of low temperature. When comparing all cultivars, genetic standard TM-1 produced the smallest values for the majority of traits under CO2, UV−B, and low temperature either alone or in combination with other treatments. Based on principal component analysis, the four cultivars were classified as tolerant (DP1522B2XF), intermediate (PHY496W3R and ST4747GLB2) and sensitive (TM-1) to multiple environmental stresses.Low temperature was identified as the most damaging treatment to cotton early seedling vigor while elevated CO2 caused the least. Existing variability of cotton cultivars in response to multiple environmental stresses could allow for selection of cultivars with the best coping ability and higher lint yield for future climate change environments.

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Identifying sediment discontinuities and solving dating puzzles using monitoring and palaeolimnological records
Xuhui DONG,Carl D. SAYER,Helen BENNION,Stephen C. MABERLY,Handong YANG,Richard W. BATTARBEE
Front. Earth Sci.. 2016, 10 (4): 621-633.  
https://doi.org/10.1007/s11707-016-0578-z

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Palaeolimnological studies should ideally be based upon continuous, undisturbed sediment sequences with reliable chronologies. However for some lake cores, these conditions are not met and palaeolimnologists are often faced with dating puzzles caused by sediment disturbances in the past. This study chooses Esthwaite Water from England to illustrate how to identify sedimentation discontinuities in lake cores and how chronologies can be established for imperfect cores by correlation of key sediment signatures in parallel core records and with long-term monitoring data (1945–2003). Replicated short cores (ESTH1, ESTH7, and ESTH8) were collected and subjected to loss-on-ignition, radiometric dating (210Pb, 137Cs, and 14C), particle size, trace metal, and fossil diatom analysis. Both a slumping and a hiatus event were detected in ESTH7 based on comparisons made between the cores and the long-term diatom data. Ordination analysis suggested that the slumped material in ESTH7 originated from sediment deposited around 1805–1880 AD. Further, it was inferred that the hiatus resulted in a loss of sediment deposited from 1870 to 1970 AD. Given the existence of three superior 14C dates in ESTH7, ESTH1 and ESTH7 were temporally correlated by multiple palaeolimnological proxies for age-depth model development. High variability in sedimentation rates was evident, but good agreement across the various palaeolimnological proxies indicated coherence in sediment processes within the coring area. Differences in sedimentation rates most likely resulted from the natural morphology of the lake basin. Our study suggests that caution is required in selecting suitable coring sites for palaeolimnological studies of small, relatively deep lakes and that proximity to steep slopes should be avoided wherever possible. Nevertheless, in some cases, comparisons between a range of contemporary and palaeolimnological records can be employed to diagnose sediment disturbances and establish a chronology.

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Black carbon record of the wildfire history of western Sichuan Province in China over the last 12.8 ka
Weiwei SUN,Enlou ZHANG,Ji SHEN,Rong CHEN,Enfeng LIU
Front. Earth Sci.. 2016, 10 (4): 634-643.  
https://doi.org/10.1007/s11707-015-0546-z

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Wildfire is recognized as a critical Earth system process which affects the global carbon cycle, atmospheric chemistry, and ecosystem dynamics. Estimating the potential impact of future climate change on the incidence of fire requires an understanding of the long-term interactions of fire, climate, vegetation, and human activity. Accordingly, we analyzed the black carbon content and the pollen stratigraphy of sediments spanning the past 12.8 ka from Lake Muge Co, an alpine lake in western Sichuan Province, in order to determine the main factors influencing regional fire regimes. The results demonstrate that wildfires occurred frequently and intensively during the late deglaciation and the early Holocene when the regional vegetation was dominated by deciduous forests. Wildfire occurrence decreased significantly during the Holocene climatic optimum between 9.2 and 5.6 cal ka BP. Overall, the wildfire history of western Sichuan Province is similar to that of the Chinese Loess Plateau and of East Asia as a whole, suggesting that regional-scale fires depended mainly on changes in the intensity of the Asian summer monsoon. In addition, the fire regime of western Sichuan Province may have been influenced by the establishment of human settlement and agriculture in western Sichuan Province and the southeastern Tibetan Plateau after about 5.5 cal ka BP, and by an intensification of cereal cultivation coupled with population expansion in southwestern China during the last two millennia.

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An assessment of precipitation and surface air temperature over China by regional climate models
Xueyuan WANG, Jianping TANG, Xiaorui NIU, Shuyu WANG
Front. Earth Sci.. 2016, 10 (4): 644-661.  
https://doi.org/10.1007/s11707-015-0548-x

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An analysis of a 20-year summer time simulation of present-day climate (1989‒2008) over China using four regional climate models coupled with different land surface models is carried out. The climatic means, interannual variability, linear trends, and extremes are examined, with focus on precipitation and near surface air temperature. The models are able to reproduce the basic features of the observed summer mean precipitation and temperature over China and the regional detail due to topographic forcing. Overall, the model performance is better for temperature than that of precipitation. The models reasonably grasp the major anomalies and standard deviations over China and the five subregions studied. The models generally reproduce the spatial pattern of high interannual variability over wet regions, and low variability over the dry regions. The models also capture well the variable temperature gradient increase to the north by latitude. Both the observed and simulated linear trend of precipitation shows a drying tendency over the Yangtze River Basin and wetting over South China. The models capture well the relatively small temperature trends in large areas of China. The models reasonably simulate the characteristics of extreme precipitation indices of heavy rain days and heavy precipitation fraction. Most of the models also performed well in capturing both the sign and magnitude of the daily maximum and minimum temperatures over China.

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Carbon concentrations of components of trees in 10-year-old Populus davidiana stands within the Desertification Combating Program of Northern China
Huitao SHEN,Wanjun ZHANG,Jiansheng CAO,Xiang ZHANG,Quanhong XU,Xue YANG,Dengpan XIAO,Yanxia ZHAO
Front. Earth Sci.. 2016, 10 (4): 662-668.  
https://doi.org/10.1007/s11707-016-0562-7

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Most studies do not consider the potential variation in carbon concentration among the different tree components of the same species in regional scale. This study examined the carbon concentrations of the components (i.e., foliage, branch, stem, and root) in a 10-year-old poplar species (Populus davidiana Dode) from the Desertification Combating Program of Northern China. The highest and lowest carbon concentrations were found in the stem and foliage, respectively. There was a significant difference in carbon concentrations among the different tree components. All of the observed carbon concentrations of tree components were lower than those predicted using the conversion factor of 0.5 applied to component biomass. Stem carbon made up 59.7% of the total tree biomass carbon. The power equation estimating proportion of tree biomass carbon against the independent variable of diameter at breast height explained more than 90% of the variability in allocation of carbon among tree components. Tree height, as a second independent variable is also discussed. Our results suggest that the difference in organic carbon concentration among tree components should be incorporated into accurately develop forest carbon budget. Moreover, further investigations on how the diameter at breast height equation developed in the present study performs across broader scales are required.

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Emergence of ancient cities in relation to geopolitical circumstances and climate change during late Holocene in northeastern Tibetan Plateau, China
Guanghui DONG,Honggao LIU,Yishi YANG,Ying YANG,Aifeng ZHOU,Zhongxin WANG,Xiaoyan REN,Fahu CHEN
Front. Earth Sci.. 2016, 10 (4): 669-682.  
https://doi.org/10.1007/s11707-015-0575-7

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The study of the history of human activities in ancient cities has provided valuable evidences for understanding the evolution of human-land relations during the late Holocene. Numerous ancient cities were discovered through archaeological surveys of the east Qinghai Province, located on the northeastern border of the Tibetan Plateau, China; however , the mystery of when or why these cities were built remains unsolved. As recorded in this paper, we sampled reliable dating materials from 47 ancient cities in the area, determined their ages by radiocarbon dating, and compared the dating results with historical documents and high resolution paleoclimate records to explore the influencing factors for the development of these ancient cities. The 54 radiocarbon dates indicated that most of these cities were built or repaired during the Han Dynasty (202 BC?AD 220), Tang Dynasty (AD 618?AD 907), the Five Dynasties and Ten Kingdoms period (AD 907?AD 960), the Song dynasty (AD 960?AD 1279), and the Ming Dynasty (AD 1368?AD 1644). The radiocarbon dates correspond well with historical records of the area. Our work suggests the ancient cities in east Qinghai Province were likely built primarily for military defense, and may have also have been affected by climate change.

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Evaluation of the occluded carbon within husk phytoliths of 35 rice cultivars
Xing SUN,Qin LIU,Jie GU,Xiang CHEN,Keya ZHU
Front. Earth Sci.. 2016, 10 (4): 683-690.  
https://doi.org/10.1007/s11707-015-0549-9

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Rice is a well-known silicon accumulator. During its periods of growth, a great number of phytoliths are formed by taking up silica via the plant roots. Concurrently, carbon in those phytoliths is sequestrated by a mechanism of long-term biogeochemical processes within the plant. Phytolith occluded C (PhytOC) is very stable and can be retained in soil for longer than a millennium. In this study, we evaluated the carbon bio-sequestration within the phytoliths produced in rice seed husks of 35 rice cultivars, with the goal of finding rice cultivars with relatively higher phytolith carbon sequestration efficiencies. The results showed that the phytolith contents ranged from 71.6 mg·g?1 to 150.1 mg·g?1, and the PhytOC contents ranged from 6.4 mg·g?1 to 38.4 mg·g?1, suggesting that there was no direct correlation between the PhytOC content and the content of rice seed husk phytoliths (R= 0.092, p>0.05). Of all rice cultivars, six showed a higher carbon sequestration efficiency in phytolith seed husks. Additionally, the carbon bio-sequestration within the rice seed husk phytoliths was approximately 0.45?3.46 kg-e-CO2·ha?1·yr?1. These rates indicate that rice cultivars are a potential source of carbon biosequestration which could contribute to the global carbon cycle and climate change.

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Development of a stationary carbon emission inventory for Shanghai using pollution source census data
Xianzhe LI, Ping JIANG, Yan ZHANG, Weichun MA
Front. Earth Sci.. 2016, 10 (4): 691-706.  
https://doi.org/10.1007/s11707-016-0553-8

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This study utilizes 521,631 activity data points from the 2007 Shanghai Pollution Source Census to compile a stationary carbon emission inventory for Shanghai. The inventory generated from our dataset shows that a large portion of Shanghai’s total energy use consists of coal-oriented energy consumption. The electricity and heat production industries, iron and steel mills, and the petroleum refining industry are the main carbon emitters. In addition, most of these industries are located in Baoshan District, which is Shanghai’s largest contributor of carbon emissions. Policy makers can use the enterprise-level carbon emission inventory and the method designed in this study to construct sound carbon emission reduction policies. The carbon trading scheme to be established in Shanghai based on the developed carbon inventory is also introduced in this paper with the aim of promoting the monitoring, reporting and verification of carbon trading. Moreover, we believe that it might be useful to consider the participation of industries, such as those for food processing, beverage, and tobacco, in Shanghai’s carbon trading scheme. Based on the results contained herein, we recommend establishing a comprehensive carbon emission inventory by inputting data from the pollution source census used in this study.

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Accumulation and source of heavy metals in sediment of a reservoir near an industrial park of northwest China
Yuanjie ZHU, Xinwei LU, Linna YANG, Lijun WANG
Front. Earth Sci.. 2016, 10 (4): 707-716.  
https://doi.org/10.1007/s11707-016-0560-9

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The accumulation and source of heavy metals As, Ba, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn in the surface sediment of a reservoir near an industrial park of northwest China were determined by enrichment factor and multivariate statistical analysis. Multivariate statistical analyses, i.e., factor analysis, cluster analysis, and correlation coefficient analysis, were used to identify the possible sources of the heavy metals. The results show that the mean concentrations of As, Ba, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn in the reservoir sediment are higher than their corresponding concentrations in the control sample, indicating all analyzed heavy metals accumulated in the surface sediments. The values of the mean concentrations of heavy metals in the surface sediment divided by their corresponding concentrations in the control sample increase in the order of Ba= Cr<Co= Pb<V<Ni<Cu= Zn<As<Mn. The enrichment factor values of Ba and Cr in the surface sediment samples are<2, revealing minimal enrichment, while the enrichment factor values of As, Co, Cu, Mn, Ni, Pb, V, and Zn are in the range of 2‒5, displaying moderate enrichment. Combining the results of correlation coefficient analysis, factor analysis, and cluster analysis, three main sources of these heavy metals were identified. As, Co, Cu, Mn, Ni, and V have mixed sources of natural and industrial sources and local consumption residues; Pb and Zn mainly originate from industrial activities, while Ba and Cr primarily originate from natural sources.

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Inventory of CO2 emissions driven by energy consumption in Hubei Province: a time-series energy input-output analysis
Jiashuo LI,Ran LUO,Qing YANG,Haiping YANG
Front. Earth Sci.. 2016, 10 (4): 717-730.  
https://doi.org/10.1007/s11707-016-0554-7

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Based on an input-output analysis, this paper compiles inventories of fuel-related CO2 emissions of Hubei economy in the years of 2002, 2005, and 2007. Results show that calculated total direct CO2 emissions rose from 114,462.69 kt (2002) to 196,650.31 kt (2005), reaching 210,419.93 kt in 2007, with an average 22.50% rate of increase. Raw coal was the dominant source of the direct emissions throughout the three years. The sector of Electric Power, Heat Production, and Supply was the main direct emissions contributor, with the largest intensities observed from 2002 (1192.97 g/CNY) to 2007 (1739.15 g/CNY). From the industrial perspective, the secondary industry, which is characterized as manufacture of finished products, was still the pillar of the Hubei economy during this period concerned, contributing more than 80% of the total direct emissions. As a net exporter of embodied CO2 emissions in 2002 and 2007, Hubei reported net-exported emissions of 4109.00 kt and 17,871.77 kt respectively; however, Hubei was once a net importer of CO2 emissions in 2005 (2511.93 kt). The CO2 emissions embodied in export and fixed capital formation had the two leading fractions of emissions embodied in the final use. The corresponding countermeasures, such as promoting renewable and clean energy and properly reducing the exports of low value added and carbon-intensive products are suggestions for reducing CO2 emissions in Hubei.

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Alternative industrial carbon emissions benchmark based on input-output analysis
Mengyao HAN, Xi JI
Front. Earth Sci.. 2016, 10 (4): 731-739.  
https://doi.org/10.1007/s11707-016-0574-3

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Some problems exist in the current carbon emissions benchmark setting systems. The primary consideration for industrial carbon emissions standards highly relate to direct carbon emissions (power-related emissions) and only a portion of indirect emissions are considered in the current carbon emissions accounting processes. This practice is insufficient and may cause double counting to some extent due to mixed emission sources. To better integrate and quantify direct and indirect carbon emissions, an embodied industrial carbon emissions benchmark setting method is proposed to guide the establishment of carbon emissions benchmarks based on input-output analysis. This method attempts to link direct carbon emissions with inter-industrial economic exchanges and systematically quantifies carbon emissions embodied in total product delivery chains. The purpose of this study is to design a practical new set of embodied intensity-based benchmarks for both direct and indirect carbon emissions. Beijing, at the first level of carbon emissions trading pilot schemes in China, plays a significant role in the establishment of these schemes and is chosen as an example in this study. The newly proposed method tends to relate emissions directly to each responsibility in a practical way through the measurement of complex production and supply chains and reduce carbon emissions from their original sources. This method is expected to be developed under uncertain internal and external contexts and is further expected to be generalized to guide the establishment of industrial benchmarks for carbon emissions trading schemes in China and other countries.

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Newmark displacement model for landslides induced by the 2013 Ms 7.0 Lushan earthquake, China
Renmao YUAN,Qinghai DENG,Dickson CUNNINGHAM,Zhujun HAN,Dongli ZHANG,Bingliang ZHANG
Front. Earth Sci.. 2016, 10 (4): 740-750.  
https://doi.org/10.1007/s11707-015-0547-y

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Predicting approximate earthquake-induced landslide displacements is helpful for assessing earthquake hazards and designing slopes to withstand future earthquake shaking. In this work, the basic methodology outlined by Jibson (1993) is applied to derive the Newmark displacement of landslides based on strong ground-motion recordings during the 2013 Lushan Ms 7.0 earthquake. By analyzing the relationships between Arias intensity, Newmark displacement, and critical acceleration of the Lushan earthquake, formulas of the Jibson93 and its modified models are shown to be applicable to the Lushan earthquake dataset. Different empirical equations with new fitting coefficients for estimating Newmark displacement are then developed for comparative analysis. The results indicate that a modified model has a better goodness of fit and a smaller estimation error for the Jibson93 formula. It indicates that the modified model may be more reasonable for the dataset of the Lushan earthquake. The analysis of results also suggests that a global equation is not ideally suited to directly estimate the Newmark displacements of landslides induced by one specific earthquake. Rather it is empirically better to perform a new multivariate regression analysis to derive new coefficients for the global equation using the dataset of the specific earthquake. The results presented in this paper can be applied to a future co-seismic landslide hazard assessment to inform reconstruction efforts in the area affected by the 2013 Lushan Ms 7.0 earthquake, and for future disaster prevention and mitigation.

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Deformation geometry and timing of the Wupoer thrust belt in the NE Pamir and its tectonic implications
Xiaogan CHENG,Hanlin CHEN,Xiubin LIN,Shufeng YANG,Shenqiang CHEN,Fenfen ZHANG,Kang LI,Zelin LIU
Front. Earth Sci.. 2016, 10 (4): 751-760.  
https://doi.org/10.1007/s11707-016-0606-z

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The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau’s tectonic evolution. Here we present new findings on the deformation geometry and timing of the Wupoer thrust belt at the northeastern margin of Pamir. Field investigations and interpretations of seismic profiles indicate that the eastern portion of the Wupoer thrust belt is dominated by an underlying foreland basin and an overlying piggy-back basin. A regional unconformity occurs between the Pliocene (N2) and the underlying Miocene (N1) or Paleogene (Pg) strata associated with two other local unconformities between Lower Pleistocene (Q1) and N2 and between Middle Pleistocene (Q2-4) and Q1 strata. Results of structural restorations suggest that compressional deformation was initiated during the latest Miocene to earliest Pliocene, contributing a total shortening magnitude of 48.6 km with a total shortening rate of 48.12%, most of which occurred in the period from the latest Miocene to earliest Pliocene. These results, combined with previous studies on the Kongur and Tarshkorgan extensional system, suggest an interesting picture of strong piedmont compressional thrusting activity concurrent with interorogen extensional rifting. Combining these results with previously published work on the lithospheric architecture of the Pamir, we propose that gravitational collapse drove the formation of simultaneous extensional and compressional structures with a weak, ductile middle crustal layer acting as a décollement along which both the extensional and compressional faults merged.

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Trace Projection Transformation: a new method for measurement of debris flow surface velocity fields
Yan YAN,Peng CUI,Xiaojun GUO,Yonggang GE
Front. Earth Sci.. 2016, 10 (4): 761-771.  
https://doi.org/10.1007/s11707-015-0576-6

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Spatiotemporal variation of velocity is important for debris flow dynamics. This paper presents a new method, the trace projection transformation, for accurate, non-contact measurement of a debris-flow surface velocity field based on a combination of dense optical flow and perspective projection transformation. The algorithm for interpreting and processing is implemented in C++ and realized in Visual Studio 2012. The method allows quantitative analysis of flow motion through videos from various angles (camera positioned at the opposite direction of fluid motion). It yields the spatiotemporal distribution of surface velocity field at pixel level and thus provides a quantitative description of the surface processes. The trace projection transformation is superior to conventional measurement methods in that it obtains the full surface velocity field by computing the optical flow of all pixels. The result achieves a 90% accuracy of when comparing with the observed values. As a case study, the method is applied to the quantitative analysis of surface velocity field of a specific debris flow.

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Multi-antenna synchronized global navigation satellite system receiver and its advantages in high-precision positioning applications
Danan DONG,Wen CHEN,Miaomiao CAI,Feng ZHOU,Minghua WANG,Chao YU,Zhengqi ZHENG,Yuanfei WANG
Front. Earth Sci.. 2016, 10 (4): 772-783.  
https://doi.org/10.1007/s11707-016-0559-2

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The multi-antenna synchronized global navigation satellite system receiver is a high precision, low cost, and widely used emerging receiver. Using this type of receiver, the satellite and receiver clock errors can be eliminated simultaneously by forming between antenna single-differences, which is equivalent to the conventional double-difference model. However, current multi-antenna synchronized global navigation satellite system receiver products have not fully realized their potential to achieve better accuracy, efficiency, and broader applications. This paper introduces the conceptual design and derivable products of multi-antenna synchronized global navigation satellite system receivers involving the aspects of attitude determination, multipath effect mitigation, phase center variation correction, and ground-based carrier phase wind-up calibration. Through case studies, the advantages of multi-antenna synchronized global navigation satellite system receivers in high-precision positioning applications are demonstrated.

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Assessing spatio-temporal variations of precipitation-use efficiency over Tibetan grasslands using MODIS and in-situ observations
Zhengjia LIU,Mei HUANG
Front. Earth Sci.. 2016, 10 (4): 784-793.  
https://doi.org/10.1007/s11707-016-0566-3

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Clarifying the spatial and temporal variations in precipitation-use efficiency (PUE) is helpful for advancing our knowledge of carbon and water cycles in Tibetan grassland ecosystems. Here we use an integrated remote sensing normalized difference vegetation index (NDVI) and in-situ above-ground net primary production (ANPP) measurements to establish an empirical exponential model to estimate spatial ANPP across the entire Tibetan Plateau. The spatial and temporal variations in PUE (the ratio of ANPP to mean annual precipitation (MAP)), as well as the relationships between PUE and other controls, were then investigated during the 2001–2012 study period. At a regional scale, PUE increased from west to east. PUE anomalies increased significantly (>0.1 g·m–2·mm–1/10 yr) in the southern areas of the Tibetan Plateau yet decreased (>0.02 g·m–2·mm–1/10 yr) in the northeastern areas. For alpine meadow, we obtained an obvious breaking point in trend of PUE against elevation gradients at 3600 m above the sea level, which showed a contrasting relationship. At the inter-annual scale, PUE anomalies were smaller in alpine steppe than in alpine meadow. The results show that PUE of Tibetan grasslands is generally high in dry years and low in wet years.

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16 articles