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A preliminary study for spatial representiveness of flux observation at ChinaFLUX sites

Science China Earth Sciences 2006年第S2期49卷 24-35页

作者： Ml Na, YU Guirui, WANG Panxing, WEN Xuefa & SUN Xiaomin Nanjing University of Information Science and Technology, Nanjing 210044, China key laboratory of ecosystem network observation and modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China 1. Nanjing University of Information Science and Technology Nanjing 210044 China 2. Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China

The results of eddy covariance observation system could represent the physical process at certain area of the surface. Thus point-to-area representativeness was of primary interest in flux observation. This research presents a preliminary study for flux observation at ChinaFLUX sites by the use of observation data and Flux Source Area Model (FSAM). Results show that the footprint expands and is further away from flux tower when atmosphere becomes more stable, the observation height increases, or the surfaces become smoother. This suggests that the area represented by the flux observation becomes larger. The distances from the reference point to the maximum point Smax and the minimum point x1 of source weight function (Dmax and Dmin, respectively) can be influenced by atmosphere stability which becomes longer when atmosphere is more stable. For more rough surfaces and lower observation point Dmax and Dmin become shorter. This research gives the footprint at level P=90% at ChinaFLUX sites at different atmosphere stability. The preliminary results of spatial representiveness at ChinaFLUX sites were given based on the dominant wind direction and footprint response to various factors. The study also provides some theoretical basis for data quality control and evaluating data uncertainty.

关键词： eddy covariance method footprint source weight function ChinaFLUX.

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Estimation and testing of linkages between forest structure and rainfall interception characteristics of a Robinia pseudoacacia plantation on China’s Loess Plateau

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Journal of Forestry Research 2022年第2期33卷 529-542页

作者： Changkun Ma Yi Luo Mingan Shao Xiaoxu Jia State Key Laboratory of Eco-Hydraulics in Northwest Arid Region Xian University of TechnologyXianChina Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100190China

Understanding the interaction between canopy structure and the parameters of interception loss is essential in predicting the variations in partitioning rainfall and water resources as affected by changes in canopy structure and in implementing water-based management in semiarid forest *** this study,seasonal variations in rainfall interception loss and canopy storage capacity as driven by canopy structure were predicted and the linkages were tested using seasonal filed *** study was conducted in nine 50 m×50 m Robinia pseudoacacia plots in the semiarid region of China’s Loess *** rain-fall,throughfall and stemflow were measured in seasons with and without leaves in 2015 and *** show that measured average interception loss for the nine plots were 17.9% and 9.4% of gross rainfall during periods with leaves (the growing season) and without leaves, respectively. Average canopy storage capacity estimated using an indirect method was 1.3 mm in the growing season and 0.2 mm in the leafless season. Correlations of relative interception loss and canopy storage capacity to canopy variables were highest for leaf/wood area index (LAI/WAI) and canopy cover, fol-lowed by bark area, basal area, tree height and stand density. Combined canopy cover, leaf/wood area index and bark area multiple regression models of interception loss and canopy storage capacity were established for the growing season and in the leafless season in 2015. It explained 97% and 96% of the variations in relative interception loss during seasons with and without leaves, respectively. It also explained 98% and 99% of the variations in canopy storage capacity during seasons with and without leaves, respectively. The empiri-cal regression models were validated using field data col-lected in 2016. The models satisfactorily predicted relative interception loss and canopy storage capacity during seasons with and without leaves. This study provides greater under-standing a

关键词： Rainfall interception loss Canopy storage Canopy structure Regression models China’s Loess Plateau

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CO_2 Flux Estimation by Different Regression Methods from an Alpine Meadow on the Qinghai-Tibetan Plateau

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Advances in Atmospheric Sciences 2010年第6期27卷 1372-1379页

作者：姜春明于贵瑞曹广民李英年张世春方华军 Key Laboratory of Ecosystem Network Observation and Modeling Chinese Academy of SciencesInstitute of Geographical Sciences and Natural Resources ResearchChinese Academy of Sciences Graduate University of the Chinese Academy of Sciences Northwest Plateau Institute of Biology Chinese Academy of Sciences

CO2 efflux was estimated using different regression methods in static chamber observation from an alpine meadow on the Qinghai-Tibetan Plateau. The CO2 efflux showed a seasonal pattern, with the maximun flux occurring in the middle of July. The temperature sensitivity of CO2 efflux （Q10） was 3.9, which was at the high end of the range of global values. CO2 emissions calculated by linear and nonlinear regression were significantly different （p 〈0.05）. Compared with the linear regression, CO2 emissions calculated by exponential regression and quadratic regression were 12.7% and 11.2% larger, respectively. However, there were no significant differences in temperature sensitivity values estimated by the three methods. In the entire growing season, the CO2 efflux estimated by linear regression may be underestimated by up to 25% compared to the real CO2 efflux. Consequently, great caution should be taken when using published flux data obtained by linear regression of static chamber observations to estimate the regional CO2 flux in alpine meadows on the Qinghai-Tibetan Plateau.

关键词： CO2 emission static chamber technique nonlinearity underestimation Qinghai-Tibetan Plateau

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Spatiotemporal dynamics of aboveground primary productivity along a precipitation gradient in Chinese temperate grassland

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Science China Earth Sciences 2007年第5期50卷 754-764页

作者： HU ZhongMin FAN JiangWen ZHONG HuaPing YU GuiRui Key Laboratory of Ecosystem Network Observation and Modeling CERN Center for Synthesis ResearchInstitute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Graduate University of Chinese Academy of Sciences Beijing 100039China

Investigating the spatial and temporal variance in productivity along natural precipitation gradients is one of the most efficient approaches to improve understanding of how ecosystems respond to climate change. In this paper, by using the natural precipitation gradient of the Inner Mongolian Plateau from east to west determined by relatively long-term observations, we analyzed the temporal and spatial dynamics of aboveground net primary productivity (ANPP) of the temperate grasslands covering this region. Across this grassland transect, ANPP increased exponentially with the increase of mean annual precipitation (MAP) (ANPP=24.47e0.005MAP, R2=0.48). Values for the three vegetation types desert steppe, typical steppe, and meadow steppe were: 60.86 gm-2a-1, 167.14 gm-2a-1 and 288.73 gm-2a-1 respectively. By contrast, temperature had negative effects on ANPP. The moisture index (K ), which takes into ac- count both precipitation and temperature could explain the spatial variance of ANPP better than MAP alone (ANPP=2020.34K1.24, R2=0.57). Temporally, we found that the inter-annual variation in ANPP (cal- culated as the coefficient of variation, CV) got greater with the increase of aridity. However, this trend was not correlated with the inter-annual variation of precipitation. For all of the three vegetation types, ANPP had greater inter-annual variation than annual precipitation (PPT). Their difference (ANPP CV/PPT CV) was greatest in desert steppe and least in meadow steppe. Our results suggest that in more arid regions, grasslands not only have lower productivity, but also higher inter-annual variation of production. Climate change may have significant effects on the productivity through changes in precipitation pattern, vegetation growth potential, and species diversity.

关键词： grassland transect spatial variance temporal variance temperature precipitation gradient Inner Mongolia

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The importance of terrestrial carbon in supporting molluscs in the wetlands of Poyang Lake

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Chinese Journal of Oceanology and Limnology 2017年第4期35卷 825-832页

作者：张欢于秀波王玉玉徐军 Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of Sciences University of Chinese Academy of Sciences College of Nature Conservation Beijing Forestry University Institute of Hydrobiology Chinese Academy of Sciences

Allochthonous organic matter plays an important role in nutrient cycling and energy mobilization in freshwater ecosystems. However, the subsidies of this carbon source in floodplain ecosystems have not yet well understood. We used a Bayesian mixing model and stable isotopes （613C and 815N） of primary food resources and dominant molluscs species, to estimate the relative importance of allochthonous carbon sources for consumers in a representative sub-lake of Poyang Lake during a prolonged dry season. Our study inferred that terrestrial-derived carbon from Carex spp. could be the primary contributor to snails and mussels in Dahuchi Lake. The mean percentage of allochthonous food resources accounted for 35%- 50% of the C incorporated by these consumers. Seston was another important energy sources for benthic consumers. However, during the winter and low water-level period, benthic algae and submerged vegetation contributed less carbon to benthic consumers. Our data highlighted the importance of terrestrial organic carbon to benthic consumers in the wetlands of Poyang Lake during the prolonged dry period. Further, our results provided a perspective that linkages between terrestrial and aquatic ecosystems might be facilitated by wintering geese via their droppings.

关键词： allochthonous Carex spp. molluscs floodplain wetland stable isotope analysis Poyang Lake

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Off-farm employment,agriculture production activities,and household dietary diversity in environmentally and economically vulnerable areas of Asia

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Journal of Integrative Agriculture 2024年第2期23卷 359-373页

作者： Yunli Bai Xuanye Zeng Chao Fu Linxiu Zhang Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China United Nations Environment Programme-International Ecosystem Management Partnership(UNEP-IEMP) Beijing 100101China University of Chinese Academy of Sciences Beijing 100101China

Access to off-farm employment has been expected to be a critical approach to ending hunger and all forms of malnutrition,two important targets of achieving Zero *** study aims to investigate the role of off-farm employment in improving dietary diversity through substitution effect and complementary effect with agricultural production activities and income *** study adopts Poisson/Tobit/Probit/OLS regressions and the instrument variable method based on the primary survey data collected among 1,282 households at 12 sites in environmentally and economically vulnerable areas of China,Nepal,Cambodia,Thailand,and Myanmar in *** results show that off-farm employment is positively associated with household dietary diversity and the consumption of flesh meat,fish and other aquatic animals,fruits,and milk and dairy products,which are rich in protein and *** results of mechanism analysis show that off-farm employment contributes to household dietary diversity by improving crop diversity,especially for poor households,boosting the probability of livestock raising for households with the middle one-third disposal income,and increasing household *** positive association between off-farm employment and household dietary diversity is much higher for households with the bottom one-third disposal income,low illiteracy,and from upper-middle income *** findings imply that off-farm employment does play a vital role in achieving multiple benefits of poverty alleviation,malnutrition reduction,and agrobiodiversity conservation in environmentally and economically vulnerable ***,it may enlarge the gaps in dietary diversity between households with low human capital and from low and lower-middle income countries and those with high human capital and from middle-high countries.

关键词： off-farm employment dietary diversity income effect substitution effect complementary effect

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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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Analyzing the velocity of vegetation phenology over the Tibetan Plateau using GIMMS NDVI3G data

Analyzing the velocity of vegetation phenology over the Tibe...

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2018 ISPRS TC III Mid-Term Symposium on Developments, Technologies and Applications in Remote Sensing

作者： Zhou, Y.K. Key Laboratory of Ecosystem Network Observation and Modelling IGSNRR CAS Beijing100101 China

Global environmental change is rapidly altering the dynamics of terrestrial vegetation, and phenology is a classic proxy to detect the response of vegetation to the changes. On the Tibetan Plateau, the earlier spring and delayed autumn vegetation phenology is widely reported. Remotely sensed NDVI can serve as a good data source for vegetation phenology study. Here GIMMS NDVI3g data was used to detect vegetation phenology status on the Tibetan Plateau. The spatial and temporal gradients are combined to depict the velocity of vegetation expanding process. This velocity index represents the instantaneous local velocity along the Earth's surface needed to maintain constant vegetation condition. This study found that NDVI velocity show a complex spatial pattern. A considerable number of regions display a later starting of growing season (SOS) and earlier end of growing season (EOS) reflected by the velocity change, particularly in the central part of the plateau. Nearly 74% vegetation experienced a shortened growing season length. Totally, the magnitude of the phenology velocity is at a small level that reveals there is not a significant variation of vegetation phenology under the climate change context. © Authors 2018. CC BY 4.0 License.

关键词： Velocity

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A R-shiny based phenology analysis system and case study using digital camera dataset

A R-shiny based phenology analysis system and case study usi...

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2018 ISPRS TC III Mid-Term Symposium on Developments, Technologies and Applications in Remote Sensing

作者： Zhou, Y.K. Key Laboratory of Ecosystem Network Observation and Modelling IGSNRR CAS Beijing100101 China

Accurate extracting of the vegetation phenology information play an important role in exploring the effects of climate changes on vegetation. Repeated photos from digital camera is a useful and huge data source in phonological analysis. Data processing and mining on phenological data is still a big challenge. There is no single tool or a universal solution for big data processing and visualization in the field of phenology extraction. In this paper, we proposed a R-shiny based web application for vegetation phenological parameters extraction and analysis. Its main functions include phenological site distribution visualization, ROI (Region of Interest) selection, vegetation index calculation and visualization, data filtering, growth trajectory fitting, phenology parameters extraction, etc. the long-term observation photography data from Freemanwood site in 2013 is processed by this system as an example. The results show that: (1) this system is capable of analyzing large data using a distributed framework;(2) The combination of multiple parameter extraction and growth curve fitting methods could effectively extract the key phenology parameters. Moreover, there are discrepancies between different combination methods in unique study areas. Vegetation with single-growth peak is suitable for using the double logistic module to fit the growth trajectory, while vegetation with multi-growth peaks should better use spline method. © Authors 2018. CC BY 4.0 License.

关键词： Vegetation

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The Altitudinal Belts of Subalpine Virgin Forest on *** Simulated by a Succession Model

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Journal of Mountain Science 2014年第6期11卷 1560-1570页

作者： CHENG Gen-wei SUN Jian SHA Yu-kun FAN Ji-hui Key Laboratory of Mountain Surface Process and Ecological Regulation Institute of Mountain Hazard and EnvironmentChinese Academy of Sciences Synthesis Research Centre of Chinese Ecosystem Research Network Key Laboratory of Ecosystem Network Observation and Modelling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences University of Chinese Academy of Sciences

How to accurately simulate the distribution of forest species based upon their biological attributes has been a traditional biogeographical *** gap models are very useful tools for examining the dynamics of forest succession and revealing the species structure of *** the present study,the GFSM(Gongga Forest Succession Model) was developed and applied to simulate the distribution,composition and succession process of forests in 100 m elevation *** results indicate that the simulated results of the tree species,quantities of the different types of trees,tree age and differences in DBH(diameter at breast height) composition were in line with the actual situation from 1400 to 3700 MASL(meters above sea level) on the eastern slope of ***,the dominant species in the simulated results were the same as those in the surveyed ***,the GFSM model can best simulate the features of forest dynamics and structure in the natural conditions of *** work provides a new approach to studying the structure and distribution characteristics of mountain ecosystems in varied ***,the results of this study suggest that the biogeochemistry mechanism model should be combined with the forestsuccession model to facilitate the ecological model in simulating the physical and chemical processes involved.

关键词： Subalpine forests Altitudinal belts Succession processes Forest gap model

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