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Abstract: Carbon exchange between the atmosphere and terrestrial ecosystems is one of the key processes in biogeochemical cycles including plant photosynthesis and biological respiration. The exchange process directly determines the ecosystem functions of material production, diversity maintenance and climate regulation. Based on carbon fluxes data collected from existing literature published during 2000 – 2015, we built the dataset of production and respiration in Chinese typical terrestrial ecosystems. The dataset contained multiple-site annual records of gross primary production, ecosystem respiration and net ecosystem production from 57 typical ecosystems in China including forest, grassland, shrub, cropland and wetland. In addition, relevant biological and climatic information were compiled, such as biome type, vegetation type, mean annual temperature and precipitation. This dataset provides important resources for evaluating regional carbon budget, assessing eco-environment carrying capacity, studying climate change, and optimizing biogeochemical cycling models.
Keywords: terrestrial ecosystem; primary production; respiration; net production; eddy covariance; carbon fluxes
|Title||A dataset of primary production, respiration and net production of Chinese typical ecosystems based on literature integration|
|Data corresponding author||Chen Zhi (firstname.lastname@example.org), Yu Guirui (email@example.com)|
|Data authors||Chen Zhi, Yu Guirui, Zhu Xianjin, Zhang Leiming, Wang Qiufeng, Jiao Cuicui|
|Time period||2000 – 2015|
|Geographical scope||Chinese typical terrestrial ecosystems|
|Data service system||<http://www.cnern.org.cn/data/meta?id=40580>;<http://www.sciencedb.cn/dataSet/handle/599>|
|Sources of funding||National Natural Science Foundation of China (31600347); National Key Research and Development Program of China (2016YFA0600103); Strategic Priority Research Program of the Chinese Academy of Sciences (XDA19020302); Science and Technology Service Network Initiative of the Chinese Academy of Sciences (KFJ-SW-STS-169)|
|Dataset composition||The dataset includes observations of gross primary production, ecosystem respiration and net ecosystem production of 57 Chinese typical ecosystems during the period of 2000 – 2015. In addition, it includes some basic information such as site location, ecosystem type, observation year, annual mean air temperature and annual total precipitation, and so forth.|
Vegetation absorbs CO2 from the atmosphere through photosynthesis and converts it into biomass, which starts the material and energy cycles in terrestrial ecosystems. The photosynthetic production of vegetation directly determines the material resources provided by ecosystems for human society, such as foods, woods, and herbages.1 Photosynthesis is always accompanied by respiratory metabolism, which consumes energy for growth and maintenance. The litter biomass provides nutrients for soil microbes and drives the biogeochemical cycle under the respiratory metabolism processes of microorganisms.2 The remaining photosynthetic production, after vegetation and microbial respiration, is the net production of the ecosystem, which determines the resource and environmental carrying capacity, carbon sequestration, and the regulation to the global climate.3
The eddy covariance technique is an effective method for continuously observing production, respiration, and net production at the ecosystem scale.4-6 Through continuous, high frequency, and automatic observation of the carbon exchange processes at the ecosystem scale, this method can help reveal the dynamic processes and influencing mechanisms of ecosystem production, respiration and net production at different time scales.7 In the past 20 years, the constructions of observation sites for the eddy covariance technique have rapidly developed.8-9 In 2002, the Chinese terrestrial ecosystem flux observation and research network (ChinaFLUX) was formally established, which began the flux observation of typical ecosystems in China. Ecosystem flux observations, were soon joined by China’s national forestry, agricultural, meteorological and other functional departments, as well as universities and research institutes. After 15 years of development, more flux observation sites have been established in different regions and different ecosystem types in China, thus enriching the flux observation data on ecosystem carbon exchange.9-10 However, there is still a lack of systematic integration of such data, and a comprehensive dataset of ecosystem production, respiration and net production has not yet been formed, which renders them insufficient in answering national ecological issues, for example, regarding resources and environmental carrying capacity, environmental protection, climate regulation, and so on.
Through collection and integration of the published literature, we constructed a dataset of the typical ecosystem production and respiratory parameters in China, with the aim to provide open access data to support the assessment of carbon sequestration efficiency and ecological environment carrying capacities, as well as to contribute to the study of global change and the optimization of the biogeochemical cycling model.
2.1 Data sources
This study collected data from literature of carbon fluxes in terrestrial ecosystems in China from 2000 to 2015. Based on the Web of Science (http://apps.webofknowledge.com) and China National Knowledge Infrastructure (http://www.cnki.net), we used the following keywords for locating relevant literature: "eddy covariance", "carbon flux" or "carbon exchange" or "carbon budget", "production", "Gross Primary Production (GPP)", "Net Ecosystem Production (NEP)", and "Net Ecosystem Exchange (NEE)", etc. The collected literature was screened by the following criteria: (1) carbon flux was uniformly measured by eddy covariance technique; (2) quality control was performed on the flux data, including three-dimensional coordinate rotation and Webb-Pearman-Leuning (WPL) correction;11-14 (3) valid data must be complete and continuous for more than one year. After screening based on the above criteria, the carbon flux data for 57 typical terrestrial ecosystems, including forest, grassland, cropland, wetland, shrubland and urban areas, was obtained (Figure 1).
2.2 Data extraction
Get Data Graph Digitizer was used to extract the gross primary production, ecosystem respiration, net ecosystem production, and auxiliary meteorological and vegetation information of the typical ecosystems from the collected literature. For sites with given multi-year annual values, we extracted the annual gross primary production, ecosystem respiration, and net ecosystem production for each year. For sites with given monthly values, we calculated the annual value by summing the monthly observations. For sites with given growing season and non-growing season values, we summed the growing and non-growing seasons to obtain an annual value. The unit of the extracted gross primary production, ecosystem respiration, and net ecosystem production was uniformly converted to g C m-2 yr-1. Finally, the extracted multi-year values were averaged to obtain the multi-year mean annual gross primary production, ecosystem respiration, and net ecosystem production for each site. Meanwhile, the geographic location, ecosystem type, and vegetation type of each site were also extracted. Geographic location includes the latitude and longitude information of the flux tower. Missing information on geographic location and ecosystem type was supplemented through an additional search for that site. In addition, climatic factors of each site during respective observation periods were extracted, such as mean annual temperature and mean annual precipitation. For sites whose temperature and precipitation data were not recorded, we used data of a nearby meteorological station of the same observation period from the global surface meteorological dataset (ftp://ftp.ncdc.noaa.gov/pub/data/gsod/). The specific data processing procedure is shown in Figure 2.
The dataset contains the gross primary production, ecosystem respiration, and net ecosystem production of 57 typical ecosystems in China from 2000 to 2015. It includes 18 forests, 20 grasslands and shrublands, 7 croplands, 10 wetlands, and 2 urban green lands.
The dataset consists of two Excel sheets, one for ecosystem production and respiration data, and the other for the sources of literature. The data fields in the data sheet are ordered as follows: sequence number, site code, site name, site name in English, full name of ecosystem, full name of ecosystem in English, ecosystem type, ecosystem type in English, latitude, longitude, altitude, mean annual temperature, mean annual precipitation, beginning time of observation, ending time of observation, net ecosystem production, gross primary production, and ecosystem respiration (Table 1). Site code is the abbreviation of the site name; for example, XSBN represents Xishuangbanna. A suffix would be added to distinguish varied treatments of one site; for example, GL-D indicates Guoluo-degraded grassland and GL-A indicates Guoluo-artificial grassland.
|Site name in English||-||Character||Xishuangbanna|
|Full name of ecosystem||-||Character||西双版纳热带常绿阔叶林|
|Full name of ecosystem in English||-||Character||Xishuangbanna tropical evergreen broadleaf forest|
|Ecosystem type in English||-||Character||Forest|
|Mean annual temperature||℃||Double||19.25|
|Mean annual precipitation||mm||Double||1416.75|
|Beginning time of observation||-||Integer||2003|
|Ending time of observation||-||Integer||2008|
|Net ecosystem production||g C m-2 yr-1||Double||168.83|
|Gross primary production||g C m-2 yr-1||Double||2342.67|
|Ecosystem respiration||g C m-2 yr-1||Double||2173.83|
|Source of literature||-||Character|||
Building upon published literature, this dataset underwent rigorous quality control throughout the processes of database selection, keywords search, document screening, data extraction and collection.
Document screening: We conducted literature search on the Web of Science (www.Webofknowledge.com) and China National Knowledge Infrastructure (http://epub.cnki.net) to ensure the validity of the references. We set "eddy covariance" as the keyword for the search, to ensure the consistency of observing methods and the comparability of measured results. All the obtained data were then subject to three-dimensional coordinate rotation, WPL correction, storage item correction, abnormal value elimination, and night CO2 correction. The resulting data were checked whether they were complete and continuous for more than one consecutive year, to ensure the reliability of the data.
Data extraction and collection: The extracted data was uniformly calculated using the arithmetic mean method to obtain the multi-year mean gross primary production, ecosystem respiration, and net ecosystem production. Furthermore, unit conversion was conducted to ensure the consistency of the data. Moreover, for sites whose meteorological data was missing, we uniformly used data of nearby meteorological stations of the same observation period as a supplement from the global surface meteorological dataset.
Data validation: After the dataset was compiled, the original data was re-checked by the data collator by referring to corresponding published literature, followed by a random sampling and cross-validation conducted by multiple data collators. Finally, the dataset was submitted to experts for a final review.
Data quality assessment: Several uncertainties are involved in this carbon flux dataset, which are mainly derived from the following aspects: (1) eddy convenience system measurement errors. During the measurement period, systematic errors might be caused due to the influence of the complex terrain, atmospheric stability, data sampling frequency response, nighttime advection flow, and so on.15 (2) Data statistical errors. Certain systematic errors were caused because each site adopted different types of data elimination criteria, correction and interpolation methods due to their varied terrain conditions and/or vegetation types. The statistical analysis of this study varied from one site to another mainly as a result of their varied friction wind speed u* setting and interpolation methods, which was to meet the different local topographical, vegetational and meteorological conditions. However, the friction wind speed u* threshold uniformly remained within the reasonable range of 0.1~0.4 m/s.13 Missing carbon flux data were interpolated by using the mean daily variation, lookup table and nonlinear regression methods. Previous studies indicated no significant difference in the interpolation results regardless of the interpolation methods used, and their impact on the total annual NEE was within the range of ± 25 g C m-2 yr-1.16
The dataset of Chinese terrestrial ecosystem production and respiration, established by this study, is the first literature-based, ecosystem-scale dataset of carbon exchange fluxes in China. This dataset covers the carbon budget characteristics of 57 typical terrestrial ecosystems in China, which can provide data support for assessing carbon sequestration efficiency and ecological environment carrying capacity, studying global change, and optimizing the biogeochemical cycling model.
Users should note the following two points when using this dataset:
First, as there is no uniform standard for flux data processing, each site adopted technical methods deemed best suitable to its local conditions. Therefore, the standards for threshold setting, flux analysis, and data interpolation varied among sites.
Second, as this study synthesized existing literature of multiple sources, the dataset reflects the multi-year mean carbon budget of each site, which is supposed to be different from that reported by any individual study.
For further information on quality control and data processing, users can refer to references 17-18.
For data access and download, users can visit the National Ecosystem Observing Research Network Data Resource Service website (http://www.cnern.org.cn). After logging in, a click of “Datasets as Paper Attachment” on the homepage or in the “Data Resources” section will direct users to a webpage for data download. Alternatively, users can also log in to Science Data Bank (http://www.sciencedb.cn/dataSet/handle/599) for data access.
We thank all the staff involved in flux observation, data management and analysis. We also thank Prof. He Nianpeng for his instruction on paper writing.
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1. Chen Z, Yu G, Zhu X et al. A dataset of primary production, respiration and net production of Chinese typical ecosystems based on literature integration. Science Data Bank. DOI: 10.11922/sciencedb.599 (2018).
How to cite this article
Chen Z, Yu G, Zhu X et al. A dataset of primary production, respiration and net production of Chinese typical ecosystems based on literature integration. China Scientific Data 4(2019). DOI: 10.11922/csdata.2018.0024.zh