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Study on the processing method of nighttime CO_2 eddy covariance flux data in ChinaFLUX

Science China Earth Sciences 2006年第S2期49卷 36-46页

作者： ZHU Zhilin, SUN Xiaomin, WEN Xuefa, ZHOU Yanlian, TIAN Jing & YUAN Guofu Key Laboratory of ecosystem network Observation and Model, Institute of Geographic Sciences and Natural Resources research, chinese Academy of Sciences, Beijing 100101, China Graduate University of the chinese Academy of Sciences, Beijing 100049, China 1. Key Laboratory of ecosystem network Observation and Model Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China2. Graduate University of the Chinese Academy of Sciences Beijing 100049 China

At present, using Eddy Covariance (EC) method to estimate the "true value" of carbon sequestration in terrestrial ecosystem arrests more attention. However, one issue is how to solve the uncertainty of observations (especially the nighttime CO2 flux data) appearing in post-processing CO2 flux data. The ratio of effective and reliable nighttime EC CO2 flux data to all nighttime data is relatively low (commonly, less than 50%) for all the long-term and continuous observation stations in the world. Thus, the processing method of nighttime CO2 flux data and its effect analysis on estimating CO2 flux annual sums are very important. In this paper, the authors analyze and discuss the reasons for underestimating nighttime CO2 flux using EC method, and introduce the general theory and method for processing nighttime CO2 flux data. By analyzing the relationship between nighttime CO2 flux and air fraction velocity u., we present an alternate method, Average Values Test (AVT), to determine the thresholds of fraction velocity (u.c) for screening the effective nighttime CO2 flux data. Meanwhile, taking the data observed in Yucheng and Changbai Mountains stations for an example, we analyze and discuss the effects of different methods or parameters on nighttime CO2 flux estimations. Finally, based on the data of part ChinaFLUX stations and related literatures, empirical models of nighttime respiration at different sites in ChinaFLUX are summarized.

关键词： eddy covariance nighttime CO2 flux data correction ChinaFLUX.

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High ecostoichiometric stability and accumulating SiO2 and NO3- as main physiological adaptive mechanisms for reed to adverse environments

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research in Cold and Arid Regions 2024年第5期16卷 250-258页

作者： JianJun Kang Fan Yang DongMei Zhang LiWen Zhao Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands Linze Inland River Basin Research Station Chinese Ecosystem Research NetworkNorthwest Institute of Eco-Environment and Resources Chinese Academy of Sciences Minqin National Studies Station for Desert Steppe ecosystem Gansu Desert Control Research Institute

Previous studies have shown that nutrients accumulation played important roles in resisting to stress resistance of *** study examined the ecostoichiometric internal stability （EIS） of nutrients accumulation and,concomitantly identified the main resistant regulating substances and their contributions to stress resistance of reed （Gramineae） in arid desert *** （digging method） and soil samples （quartering method）) obtained from sand dune （SD）,desert steppe （DP）,interdune lowland （IL）,saline meadow （SM） and wetland （W） habitats were brought back to the lab for nutrients *** indicated that soil nutrients differed obviously,while reed maintained relatively stable ratios of SiO2:N,N:K,and P:K when the eco-environments changed in different ***,reed exhibits common adaptive characteristics by mainly accumulating large amounts of SiO2（122.6–174.0 g/kg） and NO3-（166.1–216.6 g/kg）,as well as moderate levels of soluble sugar （SS:24.0–55.0 g/kg）,which are mainly stored in leaves for stress *** contribution of ions to stress resistance was 80.03%–91.15%（with SiO2and NO3-accounting for 54.91%–63.10%）,whereas the contribution of solutes was only 8.85%–19.97%（with SS contributing to 5.14%–10.91%） in different *** findings suggest that maintaining relatively high EIS,while still accumulating SiO2and NO3-as main physiological regulators might be an effective strategy for reed to positively respond to adverse habitats,which provide a strong theoretical basis and technical reference for searching useful methods for restoration and reconstruction of the degraded ecosystems in desert oasis regions.

关键词： Adaptive strategy Desert oasis Gramineae Nutrients Stoichiometric characteristics

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Sources of uncertainty in exploring rangeland phenology： A case study in an alpine meadow on the central Tibetan Plateau

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Journal of Mountain Science 2017年第9期14卷 1827-1838页

作者： ZHAO Guang-shuai SHI Pei-li Key Laboratory of ecosystem network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China University of chinese Academy of Science Beijing 100049 China China National Forestry Economics and Development research Center Beijing 100714 China

Global climate change has been found to substantially influence the phenology of rangeland,especially on the Tibetan Plateau. However, there is considerable controversy about the trends and causes of rangeland phenology owing to different phenological exploration methods and lack of ground validation. Little is known about the uncertainty in the exploration accuracy of vegetation ***, in this study, we selected a typical alpine rangeland near Damxung national meteorological station as a case study on central Tibetan Plateau, and identified several important sources influencing phenology to better understand their effects on phenological exploration. We found man-made land use was not easily distinguished from natural rangelands, and therefore this may confound phenological response to climate change in the rangeland. Change trends of phenology explored by four methods were similar, but ratio threshold method(RTM) was more suitable for exploring vegetation phenology in terms of the beginning of growing season(BGS) and end of growing season(EGS). However, some adjustments are needed when RTM is used in extreme drought years. MODIS NDVI/EVI dataset was most suitable for exploring vegetation phenology of BGS and EGS. The discrimination capacities of vegetation phenology declined with decreasing resolution of remote sensing images from MODIS to GIMMS AVHRR datasets. Additionally, distinct trends of phenological change rates were indicated in different terrain conditions, with advance of growing season in high altitudes but delay of season in lower altitudes. Therefore, it was necessary to eliminate interference of complex terrain and man-made land use to ensure the representativeness of natural vegetation. Moreover, selecting the appropriate method to explore rangelands and fully considering the impact of topography are important to accurately analyze the effects of climate change on vegetation phenology.

关键词： Climate change Data quality NDVI Phenological exploration Northern Tibetan Plateau

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Effect of experimental warming on soil respiration under conventional tillage and no-tillage farmland in the North China Plain

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Journal of Integrative Agriculture 2017年第4期16卷 967-979页

作者： TU Chun LI Fa-dong QIAO Yun-feng ZHU Nong GU Cong-ke ZHAO Xin Key Laboratory of ecosystem network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101P.R.China University of chinese Academy of Science Beijing 100049P.R.China

Understanding the response of soil respiration to global warming in agro-ecosystem is crucial for simulating terrestrial carbon （C） cycle. We conducted an infrared warming experiment under conventional tillage （CT） and no-tillage （NT） farmland for winter wheat and summer maize rotation system in North China Plain （NCP）. Treatments include CT with and without warming （CTW and CTN）, NT with and without warming （NTW and NTN）. The results indicated that warming had no sig- nificant effect on soil moisture in irrigated farmland of NCP （P〉0.05）. The elevated average soil temperature of 1.1-116℃ in crop growing periods could increase annual soil CO2 emission by 10.3% in CT filed （P〉0.05）, but significantly increase it by 12.7% in NT field （P〈0.05）, respectively. The disturbances such as plowing, irrigation and precipitation resulted in the obvious soil CO2 emission peaks, which contributed 36.6-40.8% of annual soil cumulative CO2 emission. Warming would enhance these soil CO2 emission peaks; it might be associated with the warming-induced increase of autotrophic respiration and heterotrophic respiration. Compared with un-warming treatments, dissolved organic carbon （DOC） and soil microbial biomass carbon （MBC） in warming treatments were significantly increased by 11.6-23.4 and 12.9-23.6%, respectively, indicating that the positive responses of DOC and MBC to warming in both of two tillage systems. Our study highlights that climate warming may have positive effects on soil C release in NCP in association with response of labile C substrate to warming.

关键词： global warming conventional tillage no-tillage soil respiration dissolved organic carbon soil microbial biomasscarbon

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Responses of gross primary productivity to different sizes of precipitation events in a temperate grassland ecosystem in Inner Mongolia, China

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Journal of Arid Land 2016年第1期8卷 36-46页

作者： GUO Qun LI Shenggong HU Zhongmin ZHAO Wei YU Guirui SUN Xiaomin LI Linghao LIANG Naishen BAI Wenming Key Laboratory of ecosystem network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences University of chinese Academy of Sciences State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Global Carbon Cycle research Section Center for Global Environmental research National Institute for Environmental Studies

Changes in the sizes of precipitation events in the context of global climate change may have profound impacts on ecosystem productivity in arid and semiarid grasslands. However, we still have little knowledge about to what extent grassland productivity will respond to an individual precipitation event. In this study, we quantified the duration, the maximum, and the time-integrated amount of the response of daily gross primary productivity (GPP) to an individual precipitation event and their variations with different sizes of precipitation events in a typical temperate steppe in Inner Mongolia, China. Results showed that the duration of GPP-response (τR) and the maximum absolute GPP-response (GPPmax) increased linearly with the sizes of precipitation events (Pes), driving a corresponding increase in time-integrated amount of the GPP-response (GPPtotal) because variations of GPPtotal were largely explained by τR and GPPmax. The relative contributions of these two parameters to GPPtotal were strongly Pes-dependent. The GPPmax contributed more to the variations of GPPtotal when Pes was relatively small (R was the main driver to the variations of GPPtotal when Pes was relatively large. In addition, a threshold size of at least 5 mm of precipitation was required to induce a GPP-response for the temperate steppe in this study. Our work has important implications for the modeling community to obtain an advanced understanding of productivity-response of grassland ecosystems to altered precipitation regimes.

关键词： precipitation event grassland gross primary productivity global climate change precipitation regime

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Temporal and spatial variations in hydrogeochemistry of cave percolation water and their implications for four caves in Guizhou, China

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chinese Journal Of Geochemistry 2013年第2期32卷 119-129页

作者： LUO Weijun WANG Shijie XIE Xingneng ZHOU Yunchao LI Tingyu State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences Puding Karst ecosystem research Station Chinese Academy of Sciences

Soil water and cave drip water from four cave systems in Guizhou, Southwest China, were monitored and sampled monthly from April 2003 to May 2004 to understand spatio-temporal variations in hydro-geochemistry of cave percolation water. The results indicated that among the 5 drip water sites from the Liangfeng Cave (LFC), there were no significant differences among the hydro-geochemical parameters. In the Xiniu Cave (XNC), the drip rates were variable and responded quickly to precipitation events in the 3# (No. 3) drip site with variable water head; both bulk and variation in drip rates were smaller in the 2# with constant water head. However, in the Qixing Cave (QXC) and Jiangjun Cave (JJC), drip rates, concentrations of major ions and saturation index for calcite (SI C ) were smaller, and Mg/Ca ratios in Group I (1#, 2#, 6#, 7# and 8# in the QXC; 2# and 3# in the JJC) were larger than those in Group II (3#, 4#, 5# and 9# in the QXC; 1# and 4# in the JJC). These differences might be the result of different hydrogeological processes above the caves, which are divided into five categories based on hydro-geochemistry data. The formation of some proxies in speleothem, such as Mg/Ca, is likely to be affected by those processes.

关键词：水文地球化学洞穴滴水渗漏水化学研究贵州和空间时间石窟

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Dynamic carbon-nitrogen coupling under global change

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Science China(Life Sciences) 2023年第4期66卷 771-782页

作者： Shuli Niu Lei Song Jinsong Wang Yiqi Luo Guirui Yu Key Laboratory of ecosystem network Observation and Modelling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China Center for ecosystem Science and Society Department of Biological SciencesNorthern Arizona UniversityFlagstaffAZ 86011USA

Carbon-nitrogen coupling is a fundamental principle in ecosystem ***,how the coupling responds to global change has not yet been *** a comprehensive and systematic literature review,we assessed how the dynamics of carbon processes change with increasing nitrogen input and how nitrogen processes change with increasing carbon input under global *** review shows that nitrogen input to the ecosystem mostly stimulates plant primary productivity but inconsistently decreases microbial activities or increases soil carbon sequestration,with nitrogen leaching and nitrogenous gas emission rapidly *** fixation increases and nitrogen leaching decreases to improve soil nitrogen availability and support plant growth and ecosystem carbon sequestration under elevated CO_(2)and temperature or along ecosystem *** conclude that soil nitrogen cycle processes continually adjust to change in response to either overload under nitrogen addition or deficiency under CO_(2)enrichment and ecosystem succession to couple with carbon ***,processes of both carbon and nitrogen cycles continually adjust under global change,leading to dynamic coupling in carbon and nitrogen *** dynamic coupling framework reconciles previous debates on the“uncoupling”or“decoupling”of ecosystem carbon and nitrogen cycles under global *** models failing to simulate these dynamic adjustments cannot simulate carbonnitrogen coupling nor predict ecosystem carbon sequestration well.

关键词： nitrogen limitation carbon-nitrogen interaction global change carbon sequestration soil nitrogen cycle

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Degradation leads to dramatic decrease in topsoil but not subsoil root biomass in an alpine meadow on the Tibetan Plateau, China

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Journal of Arid Land 2020年第5期12卷 806-818页

作者： ZHANG Zhenchao LIU Miao SUN Jian WEI Tianxing Synthesis research Centre of chinese ecosystem research network Key Laboratory of Ecosystem Network Observation and ModellingInstitute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water ConservationNorthwest A&F UniversityYangling 712100China Arid Land research Center Tottori UniversityTottori 6800001Japan School of Soil and Water Conservation Beijing Forestry UniversityBeijing 100083China

Understanding the effects of degradation on belowground biomass(BGB)is essential for assessment of carbon budget of the alpine meadow ecosystem on the Tibetan Plateau,*** ecosystem has been undergoing serious degradation owing to climate change and anthropogenic *** study examined the response of the vertical distribution of plant BGB to degradation and explored the underlying mechanisms in an alpine meadow on the Tibetan Plateau.A field survey was conducted in an alpine meadow with seven sequential degrees of degradation in the Zoige Plateau on the Tibetan Plateau during the peak growing season of *** measured aboveground biomass(AGB),BGB,soil water content(SWC),soil bulk density(SBD),soil compaction(SCOM),soil organic carbon(SOC),soil total nitrogen(STN),soil total phosphorus(STP),soil available nitrogen(SAN),and soil available phosphorus(STP)in the 0-30 cm soil *** results show that degradation dramatically decreased the BGB in the 0-10 cm soil layer(BGB0-10)but slightly increased the subsoil *** main reason may be that the physical-chemical properties of surface soil were more sensitive to degradation than those of subsoil,as indicated by the remarked positive associations of the trade-off value of BGB0-10 with SWC,SCOM,SOC,STN,SAN,and STP,as well as the negative correlation between the trade-off value of BGB0-10 and SBD in the soil layer of 0-10 *** addition,an increase in the proportion of forbs with increasing degradation degree directly affected the BGB vertical *** findings suggest that the decrease in the trade-off value of BGB0-10 in response to degradation might be an adaptive strategy for the degradation-induced drought and infertile soil *** study can provide theoretical support for assessing the effects of degradation on the carbon budget and sustainable development in the alpine meadow ecosystem on the Tibetan Plateau as well as other similar ecosystems in the world.

关键词： belowground biomass soil properties plant community structure degradation alpine meadow Tibetan Plateau

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Stable Carbon Isotope Variations in Cave Percolation Waters and their Implications in Four Caves of Guizhou, China

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Acta Geologica Sinica(English Edition) 2013年第5期87卷 1396-1411页

作者： LUO Weijun WANG Shijie XIE Xingneng ZHOU Yunchao LI Tingyu State Key Laboratory of Environmental Geochemistry Institute of GeochemistryChinese Academy of Sciences Puding Karst ecosystem research Station Chinese Academy of Sciences

Monitoring and sampling of main plants, soil CO2, soil water, bedrock, spring water, drip water and its corresponding speleothem were performed at four cave systems of Guizhou, Southwest China, from April 2003 to May 2004, in order to understand stable carbon isotope ratios variations of dissolved inorganic Carbon （DIC） in cave percolation waters （δ13CDIC） and their implications for paleoclimate. Stable carbon isotopic compositions and ions （Ca, Mg, Sr, SO4, CI etc.） were measured for all samples. The results indicate that there are significant differences among the δ13CDIC values from inter-cave, even inter-drip of intra-cave in the four caves. The δ13CDIC values from the Liangfeng Cave （LFC） is lightest among the four caves, where vegetation type overlying the cave is primary forest dominated by tall trees with lighter average δ13C value （-29.9‰）. And there are remarkable differences in δ13CDIC values of different drip waters in the Qixing Cave （QXC） and Jiangjun Cave （JJC）, up to 6.9‰ and 7.8‰, respectively. Further analyses show that the δ13CDIC values in cave drip waters are not only controlled by vegetation biomass overlying the cave, but also hydro-geochemical processes. Therefore, accurate interpreting of δ13C recorded in speleothems cannot be guaranteed if these effects of the above mentioned factors are not taken into consideration.

关键词： cave drip water stable carbon isotope biomass hydro-geochemistry speleothem

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Changes in individual plant traits and biomass allocation in alpine meadow with elevation variation on the Qinghai-Tibetan Plateau

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Science China(Life Sciences) 2010年第9期53卷 1142-1151页

作者： MA WeiLing SHI PeiLi LI WenHua HE YongTao ZHANG XianZhou SHEN ZhenXi CHAI SiYue Lhasa National Ecological research Station Key Laboratory of Ecosystem Network Observation and ModelingInstitute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Graduate University of chinese Academy of Sciences Beijing 100049China

Plant traits and individual plant biomass allocation of 57 perennial herbaceous species,belonging to three common functional groups (forbs,grasses and sedges) at subalpine (3700 m ASL),alpine (4300 m ASL) and subnival (≥5000 m ASL) sites were examined to test the hypothesis that at high altitudes,plants reduce the proportion of aboveground parts and allocate more biomass to belowground parts,especially storage organs,as altitude increases,so as to geminate and resist environmental ***,results indicate that some divergence in biomass allocation exists among *** increasing altitude,the mean fractions of total biomass allocated to aboveground parts *** mean fractions of total biomass allocation to storage organs at the subalpine site (7%±2% S.E.) were distinct from those at the alpine (23%±6%) and subnival (21%±6%) sites,while the proportions of green leaves at all altitudes remained almost *** 4300 m and 5000 m,the mean fractions of flower stems decreased by 45% and 41%,respectively,while fine roots increased by 86% and 102%,*** leaf areas and leaf areas of forbs and grasses deceased with rising elevation,while sedges showed opposite *** all three functional groups,leaf area ratio and leaf area root mass ratio decreased,while fine root biomass increased at higher *** allocation patterns of alpine plants were characterized by a reduction in aboveground reproductive organs and enlargement of fine roots,while the proportion of leaves remained *** was beneficial for high altitude plants to compensate carbon gain and nutrient uptake under low temperature and limited nutrients by stabilizing biomass investment to photosynthetic structures and increasing the absorption surface area of fine *** contrast to forbs and grasses that had high mycorrhizal infection,sedges had higher single leaf area and more root fraction,especially fine roots.

关键词： Qinghai-Tibetan Plateau climate stress biomass allocation shoot/root ratio plant traits fine roots

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