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Water balance and migration for maize in an oasis farmland of northwest China

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chinese Science Bulletin 2014年第34期59卷 4829-4837页

作者： Liwen Zhao Wenzhi Zhao Linze Inland River Basin research Station China Ecosystem Research Network Key Laboratory of Ecohydrology of Inland River Basin Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences

Water balance and migration characteristics are vital to the establishment of an efficient irrigation management system. Based on the observed data including microclimate and growing parameters of maize from 2009 to 2012, actual evapotranspiration during the growth period was estimated by a combination of the FAO-56 crop coefficient approach and the Penman–Monteith model; the changes in soil water storage were estimated through the monitored water content at different depths from 0 to 3 m;the water content monitoring zone was divided into three sub-zones according to the water-balance characteristics of different soil layers and water monitoring data. On these bases, in combination of water-balance model, three aspects were analyzed: water-balance characteristics at different growth stages; water-balance characteristics in the three different sub-zones; and water-migration characteristics of ten sunny days following irrigation. These analyses revealed severe deep leakage under present irrigation management, which could be remedied by limiting onetime irrigation practices and increasing irrigation frequency. Additionally, some practical suggestions are provided for different growing stages.

关键词：迁移特性水平衡绿洲农田中国西北玉米灌溉管理系统监测数据实际蒸散量

Turbulence flux measurement above the overstory of a subtropical Pinus plantation over the hilly region in southeastern China

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Science China Earth Sciences 2005年第Z1期48卷 63-73页

作者： WEN Xuefa, YU Guirui, SUN Xiaomin & LIU Yunfen chinese ecosystem research network synthesis research center, Institute of Geographic Sciences and Natural Resources research, chinese Academy of Sciences, Beijing 100101, China Graduate School of the chinese Academy of Sciences, Beijing 100039, China chinese ecosystem research network synthesis research center Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Graduate School of the chinese Academy of Sciences Beijing 100039 China chinese ecosystem research network synthesis research center Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China

Continuous turbulence flux measurement using the eddy covariance (EC) technique was made from January 1 to December 31 in 2003 at two and three canopy heights of a subtropical Pinus plantation on the red earth hilly region in southeastern China. To be able to make sure that the measured turbulence flux will equal the net ecosystem/atmosphere exchange, the quality of the data has to be assessed. Three criteria were investigated here, including the power spectra and cospectra analyses, flux variance similarity (integral turbulence test) and energy balance closure. The spectral analyses suggested that above-canopy power spectral slopes for all velocity components and scalars such as CO2, H2O and air temperature followed the expected -2/3 power law in the inertial subrange, and their cospectral slopes were close to -4/3 power law in the inertial subrange. The important contribution of large-scale motions to energy and mass transfer above the canopy at higher measurement level was also confirmed by the spectral analyses. The eddy covariance systems have the ability to resolve fluctuations associated with small-scale eddies and did not induce an obvious underestimation of the measured turbulence flux. The Monin-Obukhov similarity functions for the normalized standard deviation of vertical wind speed and air temperature were well-defined functions of atmospheric stability at two heights above the forest canopy, which indicated that turbulence flux measurements made at two heights were within the surface layer. Nocturnal flux underestimation and departures of this normalized standard deviation of vertical wind speed similarity function from that expected from Monin-Obukhov theory were a function of friction velocity. Thus, an optimal criterion of friction velocity was determined to be greater than 0.2-0.3 m s-1 for nocturnal fluxes so that the eddy covariance flux measurement was under high turbulent mixing conditions. Energy balance closure reached about 72%-81% at the stu

关键词： eddy covariance, power spectra, cospectra, Monin-Obukhov similarity, energy balance closure, nocturnal turbulence flux.

Recent greening of grasslands in northern China driven by increasing precipitation

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Journal of Plant Ecology 2021年第5期14卷 843-853页

作者： Kai Di Zhongmin Hu Mei Wang Ruochen Cao Minqi Liang Genan Wu Ruru Chen Guangcun Hao Yaolong Zhao School of Geography South China Normal UniversityShipai CampusGuangzhou 510631China synthesis research center of chinese ecosystem research network Key Laboratory of Ecosystem Network Observation and ModelingInstitute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100101China China Communications Construction Co.Ltd. Fourth Harbor Engineering Institute Co.Ltd.Guangzhou 510230China China Communications Construction Co.Ltd. Key Laboratory of Environmental Protection&Safety of Communication Foundation EngineeringGuangzhou 510230China

Aims Recent warmer and wetter climate in northern China remains a hot topic in recent years,yet its effect on vegetation growth has not been fully *** study investigated the temporal change of vegetation cover and its correlations with climatic variables from 1982 to 2018 for grasslands in northern *** aim is to clarify whether the warmer and wetter climate in recent years drives the greening of the vegetation in this *** We investigated the temporal dynamic of vegetation normalized difference vegetation index(NDVI)and its driving forces based on long time-series *** regression was used to examine whether there was a turning point of the trend of NDVI and climatic *** correlation analyses were conducted to quantify the relationship between NDVI and climatic *** multivariable regression was used to quantify the contributions of climate variables to the temporal variations in *** Findings We found a turning point of NDVI trend in 2008,with GIMMS NDVI indicating a slight increase of 0.00022 yr?1 during 1982–2008 to an increase of 0.002 yr?1 for GIMMS NDVI during 2008–2015 and 0.0018 yr?1 for MODIS NDVI during 2008–*** was the predominant driver,and air temperature and vapor pressure deficit exerted a minor impact on the temporal dynamics of ***,our results suggest a turning point of NDVI trend,and that recent warmer and wetter climate has caused vegetation greening,which provides insights for better predicting the vegetation cover in this region under changing climate.

关键词： plant growth temporal dynamics turning point trend change climate change

Pollution characteristics and health risk assessment of polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons during heating season in Beijing

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Journal of Environmental Sciences 2023年第1期123卷 169-182页

作者： Xurong Bai Jie Wei Yanqin Ren Rui Gao Fahe Chai Hong Li Fei Xu Yuxue Kong State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental SciencesBeijing 100012China Shandong University Environment Research InstituteQingdao 266237China Key Laboratory of ecosystem network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China

Polycyclic aromatic hydrocarbons(PAHs)and their nitrated derivatives(NPAHs)attract continuous attention due to their outstanding carcinogenicity and *** order to investigate the diurnal variations,sources,formation mechanism,and health risk assessment of them in heating season,particulate matter(PM)were collected in Beijing urban area from December 26,2017 to January 17,*** and NPAHs in PM were quantitatively analyzed via gas chromatography-mass spectrometry(GC-MS).Average daily concentrations of PAHs and NPAHs were(78±54)ng/m^(3)and(783±684)pg/m^(3),*** concentrations of them were significantly higher at nighttime than at daytime,and NPAHs concentrations were 1-2 orders of magnitude lower than PAHs *** the heating season,the dominant species of PAHs include benzo[b]fluoranthene,fluoranthene,pyrene,and chrysene,while 9-nitroanthracene,2+3-nitrofluoranthene,and 2-nitropyrene were dominant species for *** were found to have a single peak during heating and to be primarily distributed in the 0.4-0.7μm particle *** emissions such as biomass burning,coal combustion,and traffic emissions were the major sources of *** were produced by the primary source of vehicle emissions and the secondary reaction triggered by OH radicals,as well as biomass burning during *** to the health risk assessment,the total carcinogenic risk was higher in adults than in *** upon oral ingestion,the carcinogenic risk in children was higher than that of adults,but the risk of adults was higher than children through skin contact and respiratory inhalation.

关键词： Heating season Polycyclic aromatic hydrocarbons Nitrated polycyclic aromatic hydrocarbons Pollution characteristics Source Health risk assessment

Energy balance closure at ChinaFLUX sites

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Science China Earth Sciences 2005年第Z1期48卷 51-62页

作者： LI Zhengquan, YU Guirui, WEN Xuefa, ZHANG Leiming, REN Chuanyou & FU Yuling chinese ecosystem research network synthesis research center, Institute of Geographic Sciences and Natural Resources research, chinese Academy of Sciences, Beijing 100101, China Graduate School of the chinese Academy of Sciences, Beijing 100039, China chinese ecosystem research network synthesis research center Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Graduate School of the chinese Academy of Sciences Beijing 100039 China chinese ecosystem research network synthesis research center Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China

network of eddy covariance observation is measuring long-term carbon and water fluxes in contrasting ecosystems and climates. As one important reference of independently evaluating scalar flux estimates from eddy covariance, energy balance closure is used widely in study of carbon and water fluxes. Energy balance closure in ChinaFLUX was evaluated by statistical regression of turbulent energy fluxes (sensible and latent heat) against available energy (net radiation, soil heat flux, canopy heat storage) and the energy balance ratio (EBR) and the frequency distribution of relative errors of energy balance (S). The trends of diurnal and seasonal variation of energy balance in ChinaFLUX were analyzed. The results indicated that the imbalance was prevalent in all observation sites, but there were little differences among sites because of the properties variation of sites. The imbalance was greater during nocturnal periods than daytime and closure was improved with friction velocity intensifying. Generally the results suggested that estimates of the scalar turbulent fluxes of sensible and latent heat were underestimated and/or that available energy was overestimated. Finally, we discussed certain factors that are contributed to the imbalance of energy, such as systematic errors associated with the sampling mismatch, systematic instrument bias, neglected energy sinks, low and high frequency loss of turbulent fluxes and advection of heat and water vapor.

关键词： energy balance, ChinaFLUX, eddy covariance technique.

Comparison of flux measurement by open-path and close-path eddy covariance systems

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Science China Earth Sciences 2005年第Z1期48卷 74-84页

作者： SONG Xia, YU Guirui, LIU Yunfen, SUN Xiaomin, REN Chuanyou & WEN Xuefa chinese ecosystem research network synthesis research center, Institute of Geographic Sciences and Natural Resources research, chinese Academy Sciences, Beijing 100101, China Graduate School of the chinese Academy of Sciences, Beijing 10039, China chinese ecosystem research network synthesis research center Institute of Geographic Sciences and Natural Resources Research Chinese Academy Sciences Beijing 100101 China Graduate School of the chinese Academy of Sciences Beijing 10039 China chinese ecosystem research network synthesis research center Institute of Geographic Sciences and Natural Resources Research Chinese Academy Sciences Beijing 100101 China

For flux measurement, the eddy covariance technique supplies a possibility to directly measure the exchange between vegetation and atmosphere; and there are two kinds of eddy covariance systems, open-path and close-path systems. For the system error, it may result in difference of flux measurements by two systems. Therefore, it is necessary to compare the measured results from them. ChinaFLUX covers of eight sites applied the micrometeorological method, in which Changbai Mountains (CBS) and Qianyanzhou (QYZ) carried out open-path eddy covariance (OPEC) and close-path eddy covariance (CPEC) measurements synchronously. In this paper the data sets of CBS and QYZ were employed. The delay time of close-path analyzer to the open-path analyzer was calculated; the spectra and cospectra of time-series data of OPEC and CPEC were analyzed; the open-path flux measurement was used as a standard comparison, the close-path flux measurement results were evaluated. The results show that, at two sites the delay time of CO2 density for close-path analyzer was about 7.0-8.0 s, H2O density about 8.0-9.0 s; the spectrum from the open-path, close-path and 3D sonic anemometer was consistent with the expected -2/3 slope (log-log plot), and the cospectra showed the expected slope of -4/3 in the internal subrange; the CO? flux measured by the close-path sensor was about 84% of that of open-path measurement at QYZ, about 80% at CBS, and the latent heat flux was balanced for two systems at QYZ, 86% at CBS. From the flux difference between open-path and close-path analyzers, it could be inferred that the attenuation of turbulent fluctuations in flow through tube of CPEC affected H2O flux more significantly than CO2 flux. The gap between two systems was bigger at CBS than at QYZ; the diurnal variation in CO2 flux of two measurement systems was very consistent.

关键词： eddy covariance technique, open-path eddy covariance, close-path eddy covariance, delay time, spectrum analyze, flux.

The 30m-NDVI-based Alpine Grassland Changes and Climate Impacts in the Three-River Headwaters Region on the Qinghai-Tibet Plateau from 1990 to 2018

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Journal of Resources and Ecology 2022年第2期13卷 186-195页

作者： SUN Ziyu WANG Junbang National ecosystem Science Data center Key Laboratory of Ecosystem Network Observation and ModelingInstitute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China University of chinese Academy of Sciences Beijing 100049China

The response of long-term vegetation changes and climate change has been a hot topic in recent ***,a Landsat-based fusion model was developed and used to produce a dataset of normalized vegetation index(NDVI)for the Three-River Headwater region on the Qinghai-Tibet Plateau with a spatial resolution of 30 m and the time spanning the nearly 30 years from 1990 to *** this study,the NDVI was applied to an analysis of the spatial and temporal changes in the alpine grassland and the impacts from climate change using the Theil-Sen Median method and linear *** results showed that:(1)The regional mean NDVI was 0.39and showed a spatial pattern of decreasing from the southeast to the northwest in the recent three *** the three parks,the Lancang River Park had the highest NDVI(0.43),followed by the Yellow River Park(0.38)and Yangtze River Park(0.23).(2)An upward trending was found in the NDVI time series at a rate of 0.0031 yr^(-1)(R^(2)=0.62,P<0.01)over the whole period of 1990–*** increasing rate(0.00649 yr^(-1),R^(2)=0.71,P<0.01)in the latter period of 2005–2018 was nearly 2.3 times of that(0.00284 yr^(-1),R^(2)=0.31,P<0.01)in the previous period of1990–*** the latest periods,the three parks experienced rates that were 2.3 to 63 times the corresponding values in the early period.(3)The NDVI is correlated more positively with temperature than *** impacts of climate change decreased along with the coverage fraction from the higher,median and then lower *** climate change can explain 34%of the variability in the NDVI time series of the areas with a higher fraction of grassland coverage,while it was 31%for the median fraction and 20%for the lower *** study is the first to use the 30 m NDVI dataset spanning nearly 30 years to analyze the spatial and temporal variability and climate impacts in the alpine grasslands of the Three-River Headwater region of the Qinghai-Tibet *** results provide a

关键词： Normalized Difference Vegetation Index(NDVI) the Three-River Headwater region alpine grassland climate change

ANALYSIS OF CLIMATE VARIABILITY IN THE JINSHA RIVER VALLEY

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Journal of Tropical Meteorology 2016年第2期22卷 243-251页

作者：何云玲张一平吴志杰 School of Resources & Environment and Earth Science Yunnan University Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of Sciences Ailaoshan Station for Subtropical Forest ecosystem Studies Chinese Ecosystem Research Network

Monthly mean surface air temperatures and precipitation at 20 meteorological stations in the Jinsha River Valley(JRV) of southwest China were analyzed for temporal-spatial variation patterns during the period *** magnitude of a trend was estimated using Sen's Nonparametric Estimator of Slope *** statistical significance of a trend was assessed by the MK *** results showed that mean annual air temperature has been increasing by 0.08℃/decade during the past 50 years as a *** climate change trend in air temperature was more significant in the winter(0.13℃/decade) than in the summer(0.03℃/decade).Annual precipitation tended to increase slightly thereafter and the increasing was mainly during the crop-growing *** the greatest variation of the annual mean temperature and annual precipitation were observed at the dry-hot valley area of middle *** warming rates were found in the upper reaches whereas the dry-hot basins of middle reaches experienced a cooling trend during the past *** of the overall increasing in precipitation,more obvious upward-trends were found in the dry-hot basins of middle reaches whereas the upper reaches had a drought trend during the past decades.

关键词： temperature precipitation trend analysis climate change Jinsha River Valley

Spatio-temporal analysis of the human footprint in the Hengduan Mountain region:Assessing the effectiveness of nature reserves in reducing human impacts

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Journal of Geographical Sciences 2020年第7期30卷 1140-1154页

作者： YIN Le DAI Erfu ZHENG Du WANG Yahui MA Liang TONG Miao Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Lhasa Plateau ecosystem research Station Key Laboratory of Ecosystem Network Observation and ModelingInstitute of Geographic Sciences and Natural Resources ResearchCASBeijing 100101China University of chinese Academy of Sciences Beijing 100049China

Mapping the human footprint(HF)makes it possible to quantify human influence,which has had an unprecedented impact on the global *** five categories of human pressure data,this study mapped the HF of the Hengduan Mountain region and assessed the effectiveness of nature reserves in reducing human *** results showed that the HF of the Hengduan Mountain region was generally higher in the south and lower in the *** HF increased by 11.24%over the past 25 years,with faster growth in the *** HF growth rate in nature reserves was much lower than that across the region,which indicated that nature reserves played an important role in reducing the impact of human pressure.A study of Baimaxueshan nature reserve found that establishing nature reserves could effectively reduce the impact of human activities,and no"leakage"*** growth was an important reason for the increased HF in nature *** development of ecotourism in nature reserves must be based on ecological *** the long-term monitoring,evaluation,and management of nature reserves is a basic requirement for their long-term development.

关键词： human influence human footprint nature reserves effectiveness