Using China's ground observations,e.g.,forest inventory,grassland resource,agricultural statistics,climate,and satellite data,we estimate terrestrial vegetation carbon sinks for China's major biomes between 19...Using China's ground observations,e.g.,forest inventory,grassland resource,agricultural statistics,climate,and satellite data,we estimate terrestrial vegetation carbon sinks for China's major biomes between 1981 and 2000.The main results are in the following:(1)Forest area and forest biomass car-bon(C)stock increased from 116.5×10^(6) ha and 4.3 Pg C(1 Pg C=10^(15) g C)in the early 1980s to 142.8×10^(6) ha and 5.9 Pg C in the early 2000s,respectively.Forest biomass carbon density increased form 36.9 Mg C/ha(1 Mg C=10^(6) g C)to 41.0 Mg C/ha,with an annual carbon sequestration rate of 0.075 Pg C/a.Grassland,shrub,and crop biomass sequestrate carbon at annual rates of 0.007 Pg C/a,0.014―0.024 Pg C/a,and 0.0125―0.0143 Pg C/a,respectively.(2)The total terrestrial vegetation C sink in China is in a range of 0.096―0.106 Pg C/a between 1981 and 2000,accounting for 14.6%―16.1%of carbon dioxide(CO_(2))emitted by China's industry in the same period.In addition,soil carbon sink is estimated at 0.04―0.07 Pg C/a.Accordingly,carbon sequestration by China's terrestrial ecosystems(vegetation and soil)offsets 20.8%―26.8%of its industrial CO_(2) emission for the study period.(3)Considerable uncertainties exist in the present study,especially in the estimation of soil carbon sinks,and need further intensive investigation in the future.展开更多
Aims We aim to construct a comprehensive global database of litter decomposition rate(k value)estimated by surface floor litterbags,and investigate the direct and indirect effects of impact factors such as geographic ...Aims We aim to construct a comprehensive global database of litter decomposition rate(k value)estimated by surface floor litterbags,and investigate the direct and indirect effects of impact factors such as geographic factors(latitude and altitude),climatic factors(mean annual tempePlrature,MAT;mean annual precipitation,MAP)and litter quality factors(the contents of N,P,K,Ca,Mg and C:N ratio,lignin:N ratio)on litter decomposition.Methods We compiled a large data set of litter decomposition rates(k values)from 110 research sites and conducted simple,multiple regression and path analyses to explore the relationship between the k values and impact factors at the global scale.Important findings The k values tended to decrease with latitude(LAT)and lignin content(LIGN)of litter but increased with temperature,precipitation and nutrient concentrations at the large spatial scale.Single factor such as climate,litter quality and geographic variable could not explain litter decomposition rates well.However,the combination of total nutrient(TN)elements and C:N accounted for 70.2%of the variation in the litter decomposition rates.The combination of LAT,MAT,C:N and TN accounted for 87.54%of the variation in the litter decomposition rates.These results indicate that litter quality is the most important direct regulator of litter decomposition at the global scale.This data synthesis revealed significant relationships between litter decomposition rates and the combination of climatic factor(MAT)and litter quality(C:N,TN).The global-scale empirical relationships developed here are useful for a better understanding and modeling of the effects of litter quality and climatic factors on litter decomposition rates.展开更多
Mobile communication standards have been developed into a new era of B5G and 6G.In recent years,low earth orbit(LEO)satellites and space Internet have become hot topics.The integrated satellite and terrestrial systems...Mobile communication standards have been developed into a new era of B5G and 6G.In recent years,low earth orbit(LEO)satellites and space Internet have become hot topics.The integrated satellite and terrestrial systems have been widely discussed by industries and academics,and even are expected to be applied in those huge constellations in construction.This paper points out the trends of two stages towards system integration of the terrestrial mobile communication and the satellite communications:to be compatible with 5G,and to be integrated within 6G.Based on analysis of the challenges of both stages,key technologies are thereafter analyzed in detail,covering both air interface currently discussed in 3GPP for B5G and also novel network architecture and related transmission technologies toward future 6G.展开更多
China announced its national goal to reach the peak of carbon emission by 2030 and achieve carbon neutrality by 2060,during the General Assembly of the United Nations in September 2020.In this context,the potential of...China announced its national goal to reach the peak of carbon emission by 2030 and achieve carbon neutrality by 2060,during the General Assembly of the United Nations in September 2020.In this context,the potential of the carbon sink in China’s terrestrial ecosystems to mitigate anthropogenic carbon emissions has attracted unprecedented attention from scientific communities,policy makers and the public.Here,we reviewed the assessments on China’s terrestrial ecosystem carbon sink,with focus on the principles,frameworks and methods of terrestrial ecosystem carbon sink estimates,as well as the recent progress and existing problems.Looking forward,we identified critical issues for improving the accuracy and precision of China’s terrestrial ecosystem carbon sink,in order to serve the more realistic policy making in pathways to achieve carbon neutrality for China.展开更多
The projected changes in carbon exchange between China terrestrial ecosystem and the atmosphere and vegetation and soil carbon storage during the 21st century were investigated using an atmos-phere-vegetation interact...The projected changes in carbon exchange between China terrestrial ecosystem and the atmosphere and vegetation and soil carbon storage during the 21st century were investigated using an atmos-phere-vegetation interaction model (AVIM2). The results show that in the coming 100 a, for SRES B2 scenario and constant atmospheric CO2 concentration, the net primary productivity (NPP) of terrestrial ecosystem in China will be decreased slowly, and vegetation and soil carbon storage as well as net ecosystem productivity (NEP) will also be decreased. The carbon sink for China terrestrial ecosystem in the beginning of the 20th century will become totally a carbon source by the year of 2020, while for B2 scenario and changing atmospheric CO2 concentration, NPP for China will increase continuously from 2.94 GtC·a?1 by the end of the 20th century to 3.99 GtC·a?1 by the end of the 21st century, and vegetation and soil carbon storage will increase to 110.3 GtC. NEP in China will keep rising during the first and middle periods of the 21st century, and reach the peak around 2050s, then will decrease gradually and approach to zero by the end of the 21st century.展开更多
Enhancing the terrestrial ecosystem carbon sink(referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide(CO_(2)) concentration and to achieve carbon neu...Enhancing the terrestrial ecosystem carbon sink(referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide(CO_(2)) concentration and to achieve carbon neutrality target.To better understand the characteristics of terrestrial C sinks and their contribution to carbon neutrality,this review summarizes major progress in terrestrial C budget researches during the past decades,clarifies spatial patterns and drivers of terrestrial C sources and sinks in China and around the world,and examines the role of terrestrial C sinks in achieving carbon neutrality target.According to recent studies,the global terrestrial C sink has been increasing from a source of (-0.2±0.9) Pg C yr^(-1)(1 Pg=1015g)in the 1960s to a sink of (1.9±1.1) Pg C yr^(-1) in the 2010s.By synthesizing the published data,we estimate terrestrial C sink of 0.20–0.25 Pg C yr^(-1) in China during the past decades,and predict it to be 0.15–0.52 Pg C yr^(-1) by 2060.The terrestrial C sinks are mainly located in the mid-and high latitudes of the Northern Hemisphere,while tropical regions act as a weak C sink or source.The C balance differs much among ecosystem types:forest is the major C sink;shrubland,wetland and farmland soil act as C sinks;and whether the grassland functions as C sink or source remains unclear.Desert might be a C sink,but the magnitude and the associated mechanisms are still controversial.Elevated atmospheric CO_(2) concentration,nitrogen deposition,climate change,and land cover change are the main drivers of terrestrial C sinks,while other factors such as fires and aerosols would also affect ecosystem C balance.The driving factors of terrestrial C sink differ among regions.Elevated CO_(2) concentration and climate change are major drivers of the C sinks in North America and Europe,while afforestation and ecological restoration are additionally important forcing factors of terrestrial C sinks in China.For future studies,we recommend the necessity for intensive and long-term ec展开更多
The present study provides an overview of existing literature on changes in soil organic carbon(SOC) of various terrestrial ecosystems in China.Datasets from the literature suggest that SOC stocks in forest,grassland,...The present study provides an overview of existing literature on changes in soil organic carbon(SOC) of various terrestrial ecosystems in China.Datasets from the literature suggest that SOC stocks in forest,grassland,shrubland and cropland increased between the early 1980s and the early 2000s,amounting to(71±19) Tg·a-1.Conversion of marshland to cropland in the Sanjiang Plain of northeast China resulted in SOC loss of(6±2) Tg·a-1 during the same period.Nevertheless,large uncertainties exist in these estimates,especially for the SOC changes in the forest,shrubland and grassland.To reduce uncertainty,we suggest that future research should focus on:(i) identifying land use changes throughout China with high spatiotemporal resolution,and measuring the SOC loss and sequestration due to land use change;(ii) estimating the changes in SOC of shrubland and non-forest trees(i.e.,cash,shelter and landscape trees);(iii) quantifying the impacts of grassland management on the SOC pool;(iv) evaluating carbon changes in deep soil layers;(v) projecting SOC sequestration potential;and(vi) developing carbon budget models for better estimating the changes in SOC of terrestrial ecosystems in China.展开更多
Soil stores a large amount of the terrestrial ecosystem carbon (C) and plays an important role in maintaining global C balance. However, very few studies have addressed the regional patterns of soil organic carbon (SO...Soil stores a large amount of the terrestrial ecosystem carbon (C) and plays an important role in maintaining global C balance. However, very few studies have addressed the regional patterns of soil organic carbon (SOC) storage and the main factors influencing its changes in Chinese terrestrial ecosystems, especially using field measured data. In this study, we collected information on SOC storage in main types of ecosystems (including forest, grassland, cropland, and wetland) across 18 regions in China during the 1980s (from the Second National Soil Survey of China, SNSSC) and the 2010s (from studies published between 2004 and 2014), and evaluated its changing trends during these 30 years. The SOC storage (0-100 cm) in Chinese terrestrial ecosystems was 83.46 ± 11.89 Pg C in the 1980s and 86.50 ± 8.71 Pg C in the 2010s, and the net increase over the 30 years was 3.04 ± 1.65 Pg C, with an overall rate of 0.101 ± 0.055 Pg C yr<sup>-1</sup>. This increase was mainly observed in the topsoil (0-20 cm). Forests, grasslands, and croplands SOC storage increased 2.52 ± 0.77, 0.40 ± 0.78, and 0.07 ± 0.31 Pg C, respectively, which can be attributed to the several ecological restoration projects and agricultural practices implemented. On the other hand, SOC storage in wetlands declined 0.76 ± 0.29 Pg C, most likely because of the decrease of wetland area and SOC density. Combining these results with those of vegetation C sink (0.100 Pg C yr<sup>-1</sup>), the net C sink in Chinese terrestrial ecosystems was about 0.201 ± 0.061 Pg C yr<sup>-1</sup>, which can offset 14.85%-27.79% of the fossil fuel C emissions from the 1980s to the 2010s. These first estimates of soil C sink based on field measured data supported the premise that China’s terrestrial ecosystems have a large C sequestration potential, and further emphasized the importance of forest protection and reforestation to increase SOC storage capacity.展开更多
The eddy covariance technique has emerged as an important tool to directly measure carbon dioxide, water vapor and heat fluxes between the terrestrial ecosystem and the atmosphere after a long history of fundamental r...The eddy covariance technique has emerged as an important tool to directly measure carbon dioxide, water vapor and heat fluxes between the terrestrial ecosystem and the atmosphere after a long history of fundamental research and technological developments. With the realization of regional networks of flux measurements in North American, European, Asia, Brazil, Australia and Africa, a global-scale network of micrometeorological flux measurement (FLUXNET) was established in 1998. FLUXNET has made great progresses in investigating the environmental mechanisms controlling carbon and water cycles, quantifying spatial-temporal patterns of carbon budget and seeking the "missing carbon sink" in global terrestrial ecosystems in the past ten years. The global-scale flux measurement also built a platform for international communication in the fields of resource, ecology and environment sciences. With the continuous development of flux research, FLUXNET will introduce and explore new techniques to extend the application fields of flux measurement and to answer questions in the fields of bio-geography, eco-hydrology, meteorology, climate change, remote sensing and modeling with eddy covariance flux data. As an important part of FLUXNET, ChinaFLUX has made significant progresses in the past three years on the methodology and technique of eddy covariance flux measurement, on the responses of CO2 and H2O exchange between the terrestrial ecosystem and the atmosphere to environmental change, and on flux modeling development. Results showed that the major forests on the North-South Transect of Eastern China (NSTEC) were all carbon sinks during 2003 to 2005, and the alpine meadows on the Tibet Plateau were also small carbon sinks. However, the reserved natural grassland, Leymus chinensis steppe in Inner Mongolia, was a carbon source. On a regional scale, temperature and precipitation are the primary climatic factors that determined the carbon balance in major terrestrial ecosystems in China. Finally, the current research emphasis an展开更多
Terrestrial ecosystems may act as a source or a sink for the atmospheric greenhouse gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), depending on land use and management. This paper reviews the lit...Terrestrial ecosystems may act as a source or a sink for the atmospheric greenhouse gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), depending on land use and management. This paper reviews the literature on carbon, CH4, and N2O fluxes from terrestrial ecosystems in China, and analyzes its national greenhouse gas budget. Carbon storage in biomass and soils in Chinese terrestrial ecosystems decreased in the past 300 years, due to deforestation and expansion of cultivated land, and reached a minimum in the late 1970s. Since then, carbon storage has increased at an estimated rate of 0.19 to 0.26 Pg C yr-1, mainly owing to reforestation and afforestation. CH4 emission from natural wetlands decreased from 6.65 Tg CH4 yr-1 in 1990 to 5.71 Tg CH4 yr-1 in 2000 owing to the decrease in wetland area. CH4 emission from flooded rice fields was 7.41 Tg CH4 yr-1. At the same time, aerobic soils took up atmospheric CH4 at a rate of 2.56 Tg CH4 yr-1. Nitrous oxide emission from forestlands, grasslands, and farmlands was positively correlated with precipitation at a national scale, and the emission rate was positively correlated with the CH4 uptake rate of forestlands and grasslands (P<0.01). Natural N2O sources were estimated to be 419 Gg N yr-1 and anthropogenic sources (from farmlands) to be 292 to 476.3 Gg N yr-1, with a mean of 372.6 Gg N yr-1. The integrated budget of greenhouse gasses indicates that Chinese terrestrial ecosystems act as a small net sink for global warming potential (GWP), ranging from 0.04 to 0.32 Pg CO2-eq yr-1, in a striking contrast to terrestrial ecosystems globally, which are a source of 2.75 to 6.78 Pg CO2-eq yr-1. The ratios of anthropogenic to natural sources of CH4 and N2O are much larger in Chinese terrestrial ecosystems than they are in global averages, reflecting greater human disturbance of terrestrial ecosystems in China.展开更多
From 1992 to 2015, ecological environment has been threatened by the changes of cropland around the world. In order to evaluate the impact of cropland changes on ecosystem, we calculated the response of terrestrial ec...From 1992 to 2015, ecological environment has been threatened by the changes of cropland around the world. In order to evaluate the impact of cropland changes on ecosystem, we calculated the response of terrestrial ecosystem service values (TESVs) variation to cropland conversion based on land-use data from European Space Agency (ESA). The results showed that cropland changes were responsible for an absolute loss of $166.82 billion, equivalent to 1.17% of global TESVs in 1992. Among the different regions, the impact of cropland changes on TESVs was significant in South America and Africa but not obvious in Oceania, Asia and Europe. Cropland expansion from tropical forest was the main reason for decreases in TESVs globally, especially in South America, Africa and Asia. The effect of wetland converted to cropland was notable in North America and Europe while grassland converted to cropland played an important role in Oceania, Africa and Asia. In Europe, the force of urban expansion cannot be ignored as well. The conversion of cropland to tropical or temperate forest partly compensated for the loss of TESVs globally, especially in Asia.展开更多
Scaling, as the translation of information across spatial, temporal, and organizational scales, is essential to predictions and understanding in all sciences and has become a central issue in ecology. A large body of ...Scaling, as the translation of information across spatial, temporal, and organizational scales, is essential to predictions and understanding in all sciences and has become a central issue in ecology. A large body of theoretical and empirical evidence concerning allometric scaling in terrestrial individual plants and plant communities has been constructed around the fractal volume-filling theory of West, Brown, and Enquist （the WBE model）. One of the most thought-provoking findings has been that the metabolic rates of plants, like those of animals, scale with their size as a 3/4 power law. The earliest, single most-important study cited in support of the application of the WBE model to terrestrial plants claims that whole-plant resource use in terrestrial plants scales as the 3/4 power of total mass, as predicted by the WBE model. However, in the present study we show that empirical data actually do not support such a claim. More recent studies cited as evidence for 3/4 scaling also suffer from several statistical and data-related problems. Using a forest biomass dataset including 1 266 plots of 17 main forest types across China, we explored the scaling exponents between tree productivity and tree mass and found no universal value across forest stands. We conclude that there is not sufficient evidence to support the existence of a single constant scaling exponent for the metabolism-biomass relationship for terrestrial plants.展开更多
Current and past land use practices are critical in determining the distribution and size of global terrestrial carbon (C) sources and sinks. Althoughfossil fuel emissions dominate the anthropogenic perturbation of th...Current and past land use practices are critical in determining the distribution and size of global terrestrial carbon (C) sources and sinks. Althoughfossil fuel emissions dominate the anthropogenic perturbation of the global C cycle, land use still drives the largest portion of anthropogenic emissions in a number of tropical regions of Asia. The size of the emission flux owing to land use change is still the biggest uncertainty in the global C budget. The Intergovernmental Panel on Climate Change (IPCC) reported a flux term of 1.7 PgC@a-1 for 1990-1995 but more recent estimates suggest the magnitude of this source may be only of 0.96 PgC@a-1 for the 1990s. In addition, current and past land use practices are now thought to contribute to a large degree to the northern hemisphere terrestrial sink, and are the dominant driver for some regional sinks. However, mechanisms other than land use change need to be invoked in order to explain the inferred C sink in the tropics. Potential candidates are the carbon dioxide (CO2) fertilization and climate change; fertilization due to nitrogen (N) deposition is believed to be small or nil. Although the potential for managing C sinks is limited, improved land use management and new land uses such as reforestation and biomass fuel cropping, can further enhance current terrestrial C sinks. Best management practices in agriculture alone could sequester 0.4-0.8 PgC per year in soils if implemented globally. New methodologies to ensure verification and permanency of C sequestration need to be developed.展开更多
A wide variety of studies have estimated the magnitude of global terrestrial net primary production （NPP）, but its variations, both spatially and temporally, still remain uncertain. By using an improved process-base...A wide variety of studies have estimated the magnitude of global terrestrial net primary production （NPP）, but its variations, both spatially and temporally, still remain uncertain. By using an improved process-based terrestrial ecosystem model （DLEM, Dynamic Land Ecosystem Model）, we provide an estimate of global terrestrial NPP induced by multiple environmental factors and examine the response of terrestrial NPP to climate variability at biome and global levels and along latitudes throughout the first decade of the 21st century. The model simulation estimates an average global terrestrial NPP of 54.6 Pg C yr-1 during 2000-2009, varying from 52.8 Pg C yr-1 in the dry year of 2002 to 56.4 Pg C yr-1 in the wet year of 2008. In wet years, a large increase in terrestrial NPP compared to the decadal mean was prevalent in Amazonia, Africa and Australia. In dry years, however, we found a 3.2% reduction in global terrestrial NPP compared to the decadal mean, primarily due to limited moisture supply in tropical regions. At a global level, precipitation explained approximately 63% of the variation in terrestrial NPP, while the rest was attributed to changes in temperature and other environmental factors. Precipitation was the major factor determining inter-annual variation in terrestrial NPP in low-latitude regions. However, in midand high-latitude regions, temperature variability largely controlled the magnitude of terrestrial NPP. Our results imply that pro- jected climate warming and increasing climate extreme events would alter the magnitude and spatiotemporal patterns of global terrestrial NPP.展开更多
The paper respectively adopted physio-chemical properties of every soil stratum from 2473 soil profiles of the second national soil survey. The corresponding carbon content of soils is estimated by utilizing conversio...The paper respectively adopted physio-chemical properties of every soil stratum from 2473 soil profiles of the second national soil survey. The corresponding carbon content of soils is estimated by utilizing conversion coefficient 0.58. In the second soil survey, the total amount of soil organic carbon is about 924.18xl08t and carbon density is about 10.53 kgC/m2 in China according to the area of 877.63x106hm2 surveyed throughout the country. The spatial distribution characteristics of soil organic carbon in China is that the carbon storage increases when latitude increases in eastern China and the carbon storage decreases when longitude reduces in northern China. A transitional zone with great variation in carbon storage exists. Moreover, there is an increasing tendency of carbon density with decrease of latitude in western China. Soil circle is of great significance to global change, but with substantial difference in soil spatial distribution throughout the country. Because the structure of soil is inhomogeneous, it could bring some mistakes in estimating soil carbon reservoirs. It is necessary to farther resolve soil respiration and organic matter conversion and other questions by developing uniform and normal methods of measurement and sampling.展开更多
To predict global climate change and to implement the Kyoto Protocol for stabilizing atmospheric greenhouse gases concentrations require quantifying spatio-temporal variations in the terrestrial carbon sink accurately...To predict global climate change and to implement the Kyoto Protocol for stabilizing atmospheric greenhouse gases concentrations require quantifying spatio-temporal variations in the terrestrial carbon sink accurately. During the past decade multi-scale ecological experiment and observation networks have been established using various new technologies (e.g. controlled environmental facilities, eddy covariance techniques and quantitative remote sensing), and have obtained a large amount of data about terrestrial ecosystem carbon cycle. However, uncertainties in the magnitude and spatio-temporal variations of the terrestrial carbon sink and in understanding the underlying mechanisms have not been reduced significantly. One of the major reasons is that the observations and experiments were conducted at individual scales independently, but it is the interactions of factors and processes at different scales that determine the dynamics of the terrestrial carbon sink. Since experiments and observations are always conducted at specific scales, to understand cross-scale interactions requires mechanistic analysis that is best to be achieved by mechanistic modeling. However, mechanistic ecosystem models are mainly based on data from single-scale experiments and observations and hence have no capacity to simulate mechanistic cross-scale interconnection and interactions of ecosystem processes. New-generation mechanistic ecosystem models based on new ecological theoretical framework are needed to quantify the mechanisms from micro-level fast eco-physiological responses to macro-level slow acclimation in the pattern and structure in disturbed ecosystems. Multi-scale data-model fusion is a recently emerging approach to assimilate multi-scale observational data into mechanistic, dynamic modeling, in which the structure and parameters of mechanistic models for simulating cross-scale interactions are optimized using multi-scale observational data. The models are validated and evaluated at different spatial and temporal scales and r展开更多
Heat flow plays an important role in the study ot thermal structure and thermal evolutionof continental margin of the northern South China Sea. The analysis of heat flow value shows that margin heat flow in the northe...Heat flow plays an important role in the study ot thermal structure and thermal evolutionof continental margin of the northern South China Sea. The analysis of heat flow value shows that margin heat flow in the northern South China Sea is relatively high setting, but the percentage of crustal heat flow is lower than 35% in terrestrial heat flow. The terrestrial heat flow exhibited a current of rise from the Northern Continental Margin to the Southern Central Basin. However, the proportion of crustal heat flow in terrestrial heat flow slowly dropped down in the same direction. It is suggested that the main factor causing high heat flow setting is the moving up of hot material from asthenosphere.展开更多
基金Supported by the National Natural Science Foundation of China(Grant Nos.90211016,40638039,40228001,and 40021101)the Key MOE Research Project(Grant No.306019)
文摘Using China's ground observations,e.g.,forest inventory,grassland resource,agricultural statistics,climate,and satellite data,we estimate terrestrial vegetation carbon sinks for China's major biomes between 1981 and 2000.The main results are in the following:(1)Forest area and forest biomass car-bon(C)stock increased from 116.5×10^(6) ha and 4.3 Pg C(1 Pg C=10^(15) g C)in the early 1980s to 142.8×10^(6) ha and 5.9 Pg C in the early 2000s,respectively.Forest biomass carbon density increased form 36.9 Mg C/ha(1 Mg C=10^(6) g C)to 41.0 Mg C/ha,with an annual carbon sequestration rate of 0.075 Pg C/a.Grassland,shrub,and crop biomass sequestrate carbon at annual rates of 0.007 Pg C/a,0.014―0.024 Pg C/a,and 0.0125―0.0143 Pg C/a,respectively.(2)The total terrestrial vegetation C sink in China is in a range of 0.096―0.106 Pg C/a between 1981 and 2000,accounting for 14.6%―16.1%of carbon dioxide(CO_(2))emitted by China's industry in the same period.In addition,soil carbon sink is estimated at 0.04―0.07 Pg C/a.Accordingly,carbon sequestration by China's terrestrial ecosystems(vegetation and soil)offsets 20.8%―26.8%of its industrial CO_(2) emission for the study period.(3)Considerable uncertainties exist in the present study,especially in the estimation of soil carbon sinks,and need further intensive investigation in the future.
基金supported by the Chinese Ecosystem Research Net(CERN)NSFC(30570350,40730102,30725006)+1 种基金by the Office of Science(BER),U.S.Department of Energy,Grant No.DE-FG03-99ER62800through the South Central Regional Center of the National Institute for Global Environmental Change under Cooperative Agreement No.DE-FC03-90ER61010.
文摘Aims We aim to construct a comprehensive global database of litter decomposition rate(k value)estimated by surface floor litterbags,and investigate the direct and indirect effects of impact factors such as geographic factors(latitude and altitude),climatic factors(mean annual tempePlrature,MAT;mean annual precipitation,MAP)and litter quality factors(the contents of N,P,K,Ca,Mg and C:N ratio,lignin:N ratio)on litter decomposition.Methods We compiled a large data set of litter decomposition rates(k values)from 110 research sites and conducted simple,multiple regression and path analyses to explore the relationship between the k values and impact factors at the global scale.Important findings The k values tended to decrease with latitude(LAT)and lignin content(LIGN)of litter but increased with temperature,precipitation and nutrient concentrations at the large spatial scale.Single factor such as climate,litter quality and geographic variable could not explain litter decomposition rates well.However,the combination of total nutrient(TN)elements and C:N accounted for 70.2%of the variation in the litter decomposition rates.The combination of LAT,MAT,C:N and TN accounted for 87.54%of the variation in the litter decomposition rates.These results indicate that litter quality is the most important direct regulator of litter decomposition at the global scale.This data synthesis revealed significant relationships between litter decomposition rates and the combination of climatic factor(MAT)and litter quality(C:N,TN).The global-scale empirical relationships developed here are useful for a better understanding and modeling of the effects of litter quality and climatic factors on litter decomposition rates.
基金This work was supported in part by the National Science Fund for Distinguished Young Scholars in China under grant 61425012the National Science Foundation Project in China under grant 61931005 and 61731017.
文摘Mobile communication standards have been developed into a new era of B5G and 6G.In recent years,low earth orbit(LEO)satellites and space Internet have become hot topics.The integrated satellite and terrestrial systems have been widely discussed by industries and academics,and even are expected to be applied in those huge constellations in construction.This paper points out the trends of two stages towards system integration of the terrestrial mobile communication and the satellite communications:to be compatible with 5G,and to be integrated within 6G.Based on analysis of the challenges of both stages,key technologies are thereafter analyzed in detail,covering both air interface currently discussed in 3GPP for B5G and also novel network architecture and related transmission technologies toward future 6G.
基金supported by the National Natural Science Foundation of China(Grant No.41988101)National Key R&D Program of China(Grant No.2019YFA0607304)。
文摘China announced its national goal to reach the peak of carbon emission by 2030 and achieve carbon neutrality by 2060,during the General Assembly of the United Nations in September 2020.In this context,the potential of the carbon sink in China’s terrestrial ecosystems to mitigate anthropogenic carbon emissions has attracted unprecedented attention from scientific communities,policy makers and the public.Here,we reviewed the assessments on China’s terrestrial ecosystem carbon sink,with focus on the principles,frameworks and methods of terrestrial ecosystem carbon sink estimates,as well as the recent progress and existing problems.Looking forward,we identified critical issues for improving the accuracy and precision of China’s terrestrial ecosystem carbon sink,in order to serve the more realistic policy making in pathways to achieve carbon neutrality for China.
基金the Basic Research Program of China (Grant No. 2002CB412500)the National Natural Science Foundation of China (Grant No. 30590384)
文摘The projected changes in carbon exchange between China terrestrial ecosystem and the atmosphere and vegetation and soil carbon storage during the 21st century were investigated using an atmos-phere-vegetation interaction model (AVIM2). The results show that in the coming 100 a, for SRES B2 scenario and constant atmospheric CO2 concentration, the net primary productivity (NPP) of terrestrial ecosystem in China will be decreased slowly, and vegetation and soil carbon storage as well as net ecosystem productivity (NEP) will also be decreased. The carbon sink for China terrestrial ecosystem in the beginning of the 20th century will become totally a carbon source by the year of 2020, while for B2 scenario and changing atmospheric CO2 concentration, NPP for China will increase continuously from 2.94 GtC·a?1 by the end of the 20th century to 3.99 GtC·a?1 by the end of the 21st century, and vegetation and soil carbon storage will increase to 110.3 GtC. NEP in China will keep rising during the first and middle periods of the 21st century, and reach the peak around 2050s, then will decrease gradually and approach to zero by the end of the 21st century.
基金supported by the National Natural Science Foundation of China (31988102)。
文摘Enhancing the terrestrial ecosystem carbon sink(referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide(CO_(2)) concentration and to achieve carbon neutrality target.To better understand the characteristics of terrestrial C sinks and their contribution to carbon neutrality,this review summarizes major progress in terrestrial C budget researches during the past decades,clarifies spatial patterns and drivers of terrestrial C sources and sinks in China and around the world,and examines the role of terrestrial C sinks in achieving carbon neutrality target.According to recent studies,the global terrestrial C sink has been increasing from a source of (-0.2±0.9) Pg C yr^(-1)(1 Pg=1015g)in the 1960s to a sink of (1.9±1.1) Pg C yr^(-1) in the 2010s.By synthesizing the published data,we estimate terrestrial C sink of 0.20–0.25 Pg C yr^(-1) in China during the past decades,and predict it to be 0.15–0.52 Pg C yr^(-1) by 2060.The terrestrial C sinks are mainly located in the mid-and high latitudes of the Northern Hemisphere,while tropical regions act as a weak C sink or source.The C balance differs much among ecosystem types:forest is the major C sink;shrubland,wetland and farmland soil act as C sinks;and whether the grassland functions as C sink or source remains unclear.Desert might be a C sink,but the magnitude and the associated mechanisms are still controversial.Elevated atmospheric CO_(2) concentration,nitrogen deposition,climate change,and land cover change are the main drivers of terrestrial C sinks,while other factors such as fires and aerosols would also affect ecosystem C balance.The driving factors of terrestrial C sink differ among regions.Elevated CO_(2) concentration and climate change are major drivers of the C sinks in North America and Europe,while afforestation and ecological restoration are additionally important forcing factors of terrestrial C sinks in China.For future studies,we recommend the necessity for intensive and long-term ec
基金supported by the A3 Foresight Program (Grant No. 30721140306),National Science Foundation of China, the Knowledge Innovation Program (Grant No. KZCX2-YW-Q1-15)Chinese Academy of Sciences, and the National High-Tech Research and Development Program of China (Grant No. 2009AA12Z1462)
文摘The present study provides an overview of existing literature on changes in soil organic carbon(SOC) of various terrestrial ecosystems in China.Datasets from the literature suggest that SOC stocks in forest,grassland,shrubland and cropland increased between the early 1980s and the early 2000s,amounting to(71±19) Tg·a-1.Conversion of marshland to cropland in the Sanjiang Plain of northeast China resulted in SOC loss of(6±2) Tg·a-1 during the same period.Nevertheless,large uncertainties exist in these estimates,especially for the SOC changes in the forest,shrubland and grassland.To reduce uncertainty,we suggest that future research should focus on:(i) identifying land use changes throughout China with high spatiotemporal resolution,and measuring the SOC loss and sequestration due to land use change;(ii) estimating the changes in SOC of shrubland and non-forest trees(i.e.,cash,shelter and landscape trees);(iii) quantifying the impacts of grassland management on the SOC pool;(iv) evaluating carbon changes in deep soil layers;(v) projecting SOC sequestration potential;and(vi) developing carbon budget models for better estimating the changes in SOC of terrestrial ecosystems in China.
基金The Chinese Academy of Sciences Strategic Priority Research Program,No.XDA19020302National Key Research Project of China,No.2016YFC0500202National Natural Science Foundation of China,No.31290221,No.41571130043,No.31570471
文摘Soil stores a large amount of the terrestrial ecosystem carbon (C) and plays an important role in maintaining global C balance. However, very few studies have addressed the regional patterns of soil organic carbon (SOC) storage and the main factors influencing its changes in Chinese terrestrial ecosystems, especially using field measured data. In this study, we collected information on SOC storage in main types of ecosystems (including forest, grassland, cropland, and wetland) across 18 regions in China during the 1980s (from the Second National Soil Survey of China, SNSSC) and the 2010s (from studies published between 2004 and 2014), and evaluated its changing trends during these 30 years. The SOC storage (0-100 cm) in Chinese terrestrial ecosystems was 83.46 ± 11.89 Pg C in the 1980s and 86.50 ± 8.71 Pg C in the 2010s, and the net increase over the 30 years was 3.04 ± 1.65 Pg C, with an overall rate of 0.101 ± 0.055 Pg C yr<sup>-1</sup>. This increase was mainly observed in the topsoil (0-20 cm). Forests, grasslands, and croplands SOC storage increased 2.52 ± 0.77, 0.40 ± 0.78, and 0.07 ± 0.31 Pg C, respectively, which can be attributed to the several ecological restoration projects and agricultural practices implemented. On the other hand, SOC storage in wetlands declined 0.76 ± 0.29 Pg C, most likely because of the decrease of wetland area and SOC density. Combining these results with those of vegetation C sink (0.100 Pg C yr<sup>-1</sup>), the net C sink in Chinese terrestrial ecosystems was about 0.201 ± 0.061 Pg C yr<sup>-1</sup>, which can offset 14.85%-27.79% of the fossil fuel C emissions from the 1980s to the 2010s. These first estimates of soil C sink based on field measured data supported the premise that China’s terrestrial ecosystems have a large C sequestration potential, and further emphasized the importance of forest protection and reforestation to increase SOC storage capacity.
文摘The eddy covariance technique has emerged as an important tool to directly measure carbon dioxide, water vapor and heat fluxes between the terrestrial ecosystem and the atmosphere after a long history of fundamental research and technological developments. With the realization of regional networks of flux measurements in North American, European, Asia, Brazil, Australia and Africa, a global-scale network of micrometeorological flux measurement (FLUXNET) was established in 1998. FLUXNET has made great progresses in investigating the environmental mechanisms controlling carbon and water cycles, quantifying spatial-temporal patterns of carbon budget and seeking the "missing carbon sink" in global terrestrial ecosystems in the past ten years. The global-scale flux measurement also built a platform for international communication in the fields of resource, ecology and environment sciences. With the continuous development of flux research, FLUXNET will introduce and explore new techniques to extend the application fields of flux measurement and to answer questions in the fields of bio-geography, eco-hydrology, meteorology, climate change, remote sensing and modeling with eddy covariance flux data. As an important part of FLUXNET, ChinaFLUX has made significant progresses in the past three years on the methodology and technique of eddy covariance flux measurement, on the responses of CO2 and H2O exchange between the terrestrial ecosystem and the atmosphere to environmental change, and on flux modeling development. Results showed that the major forests on the North-South Transect of Eastern China (NSTEC) were all carbon sinks during 2003 to 2005, and the alpine meadows on the Tibet Plateau were also small carbon sinks. However, the reserved natural grassland, Leymus chinensis steppe in Inner Mongolia, was a carbon source. On a regional scale, temperature and precipitation are the primary climatic factors that determined the carbon balance in major terrestrial ecosystems in China. Finally, the current research emphasis an
基金financially funded by Key Project of Chinese National Programs for Fundamental Research and Development (Grant No.2010CB833500)National Natural Science Foundation of China (Grant No. 30590381)Innovation Program of the Chinese Academy of Sciences(Grant No. KZCX2-YW-432)
基金supported by National Natural Science Foundation of China (Grant Nos. 40921061 and 40830531)Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA05020000)
文摘Terrestrial ecosystems may act as a source or a sink for the atmospheric greenhouse gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), depending on land use and management. This paper reviews the literature on carbon, CH4, and N2O fluxes from terrestrial ecosystems in China, and analyzes its national greenhouse gas budget. Carbon storage in biomass and soils in Chinese terrestrial ecosystems decreased in the past 300 years, due to deforestation and expansion of cultivated land, and reached a minimum in the late 1970s. Since then, carbon storage has increased at an estimated rate of 0.19 to 0.26 Pg C yr-1, mainly owing to reforestation and afforestation. CH4 emission from natural wetlands decreased from 6.65 Tg CH4 yr-1 in 1990 to 5.71 Tg CH4 yr-1 in 2000 owing to the decrease in wetland area. CH4 emission from flooded rice fields was 7.41 Tg CH4 yr-1. At the same time, aerobic soils took up atmospheric CH4 at a rate of 2.56 Tg CH4 yr-1. Nitrous oxide emission from forestlands, grasslands, and farmlands was positively correlated with precipitation at a national scale, and the emission rate was positively correlated with the CH4 uptake rate of forestlands and grasslands (P<0.01). Natural N2O sources were estimated to be 419 Gg N yr-1 and anthropogenic sources (from farmlands) to be 292 to 476.3 Gg N yr-1, with a mean of 372.6 Gg N yr-1. The integrated budget of greenhouse gasses indicates that Chinese terrestrial ecosystems act as a small net sink for global warming potential (GWP), ranging from 0.04 to 0.32 Pg CO2-eq yr-1, in a striking contrast to terrestrial ecosystems globally, which are a source of 2.75 to 6.78 Pg CO2-eq yr-1. The ratios of anthropogenic to natural sources of CH4 and N2O are much larger in Chinese terrestrial ecosystems than they are in global averages, reflecting greater human disturbance of terrestrial ecosystems in China.
基金National Natural Science Foundation of China,No.41771116,No.41501095National Basic Research Program of China,No.2015CB452705National Key Research and Development Program of China,No.2016YFC0502103
文摘From 1992 to 2015, ecological environment has been threatened by the changes of cropland around the world. In order to evaluate the impact of cropland changes on ecosystem, we calculated the response of terrestrial ecosystem service values (TESVs) variation to cropland conversion based on land-use data from European Space Agency (ESA). The results showed that cropland changes were responsible for an absolute loss of $166.82 billion, equivalent to 1.17% of global TESVs in 1992. Among the different regions, the impact of cropland changes on TESVs was significant in South America and Africa but not obvious in Oceania, Asia and Europe. Cropland expansion from tropical forest was the main reason for decreases in TESVs globally, especially in South America, Africa and Asia. The effect of wetland converted to cropland was notable in North America and Europe while grassland converted to cropland played an important role in Oceania, Africa and Asia. In Europe, the force of urban expansion cannot be ignored as well. The conversion of cropland to tropical or temperate forest partly compensated for the loss of TESVs globally, especially in Asia.
基金中国科学院知识创新工程项目，the Natural Resources Research, the Chinese Academy of Sciences，中国科学院资助项目
文摘Scaling, as the translation of information across spatial, temporal, and organizational scales, is essential to predictions and understanding in all sciences and has become a central issue in ecology. A large body of theoretical and empirical evidence concerning allometric scaling in terrestrial individual plants and plant communities has been constructed around the fractal volume-filling theory of West, Brown, and Enquist （the WBE model）. One of the most thought-provoking findings has been that the metabolic rates of plants, like those of animals, scale with their size as a 3/4 power law. The earliest, single most-important study cited in support of the application of the WBE model to terrestrial plants claims that whole-plant resource use in terrestrial plants scales as the 3/4 power of total mass, as predicted by the WBE model. However, in the present study we show that empirical data actually do not support such a claim. More recent studies cited as evidence for 3/4 scaling also suffer from several statistical and data-related problems. Using a forest biomass dataset including 1 266 plots of 17 main forest types across China, we explored the scaling exponents between tree productivity and tree mass and found no universal value across forest stands. We conclude that there is not sufficient evidence to support the existence of a single constant scaling exponent for the metabolism-biomass relationship for terrestrial plants.
文摘Current and past land use practices are critical in determining the distribution and size of global terrestrial carbon (C) sources and sinks. Althoughfossil fuel emissions dominate the anthropogenic perturbation of the global C cycle, land use still drives the largest portion of anthropogenic emissions in a number of tropical regions of Asia. The size of the emission flux owing to land use change is still the biggest uncertainty in the global C budget. The Intergovernmental Panel on Climate Change (IPCC) reported a flux term of 1.7 PgC@a-1 for 1990-1995 but more recent estimates suggest the magnitude of this source may be only of 0.96 PgC@a-1 for the 1990s. In addition, current and past land use practices are now thought to contribute to a large degree to the northern hemisphere terrestrial sink, and are the dominant driver for some regional sinks. However, mechanisms other than land use change need to be invoked in order to explain the inferred C sink in the tropics. Potential candidates are the carbon dioxide (CO2) fertilization and climate change; fertilization due to nitrogen (N) deposition is believed to be small or nil. Although the potential for managing C sinks is limited, improved land use management and new land uses such as reforestation and biomass fuel cropping, can further enhance current terrestrial C sinks. Best management practices in agriculture alone could sequester 0.4-0.8 PgC per year in soils if implemented globally. New methodologies to ensure verification and permanency of C sequestration need to be developed.
基金NSF Decadal and Regional Climate Prediction using Earth System Models,No.AGS-1243220NSF Dynamics of Coupled Natural and Human Systems,No.1210360+2 种基金NSF Computer and Network Systems,No.CNS-1059376NASA Land Cover/Land Use Change Program,No.NNX08AL73G S01NASA Interdisciplinary Science Program,No.NNX10AU06G,No.NNX11AD47G
文摘A wide variety of studies have estimated the magnitude of global terrestrial net primary production （NPP）, but its variations, both spatially and temporally, still remain uncertain. By using an improved process-based terrestrial ecosystem model （DLEM, Dynamic Land Ecosystem Model）, we provide an estimate of global terrestrial NPP induced by multiple environmental factors and examine the response of terrestrial NPP to climate variability at biome and global levels and along latitudes throughout the first decade of the 21st century. The model simulation estimates an average global terrestrial NPP of 54.6 Pg C yr-1 during 2000-2009, varying from 52.8 Pg C yr-1 in the dry year of 2002 to 56.4 Pg C yr-1 in the wet year of 2008. In wet years, a large increase in terrestrial NPP compared to the decadal mean was prevalent in Amazonia, Africa and Australia. In dry years, however, we found a 3.2% reduction in global terrestrial NPP compared to the decadal mean, primarily due to limited moisture supply in tropical regions. At a global level, precipitation explained approximately 63% of the variation in terrestrial NPP, while the rest was attributed to changes in temperature and other environmental factors. Precipitation was the major factor determining inter-annual variation in terrestrial NPP in low-latitude regions. However, in midand high-latitude regions, temperature variability largely controlled the magnitude of terrestrial NPP. Our results imply that pro- jected climate warming and increasing climate extreme events would alter the magnitude and spatiotemporal patterns of global terrestrial NPP.
基金Key Project of Chinese Academy of Sciences, No. KZ95T-03-02-04 Key Project of State Science and Technology, No. 96-911-01-01
文摘The paper respectively adopted physio-chemical properties of every soil stratum from 2473 soil profiles of the second national soil survey. The corresponding carbon content of soils is estimated by utilizing conversion coefficient 0.58. In the second soil survey, the total amount of soil organic carbon is about 924.18xl08t and carbon density is about 10.53 kgC/m2 in China according to the area of 877.63x106hm2 surveyed throughout the country. The spatial distribution characteristics of soil organic carbon in China is that the carbon storage increases when latitude increases in eastern China and the carbon storage decreases when longitude reduces in northern China. A transitional zone with great variation in carbon storage exists. Moreover, there is an increasing tendency of carbon density with decrease of latitude in western China. Soil circle is of great significance to global change, but with substantial difference in soil spatial distribution throughout the country. Because the structure of soil is inhomogeneous, it could bring some mistakes in estimating soil carbon reservoirs. It is necessary to farther resolve soil respiration and organic matter conversion and other questions by developing uniform and normal methods of measurement and sampling.
基金This study was supported by the China's Ministry of Science and Technology(Grant No.G2002CB412507)the National Natural Science Foundation of China(Grant No.40425103).
文摘To predict global climate change and to implement the Kyoto Protocol for stabilizing atmospheric greenhouse gases concentrations require quantifying spatio-temporal variations in the terrestrial carbon sink accurately. During the past decade multi-scale ecological experiment and observation networks have been established using various new technologies (e.g. controlled environmental facilities, eddy covariance techniques and quantitative remote sensing), and have obtained a large amount of data about terrestrial ecosystem carbon cycle. However, uncertainties in the magnitude and spatio-temporal variations of the terrestrial carbon sink and in understanding the underlying mechanisms have not been reduced significantly. One of the major reasons is that the observations and experiments were conducted at individual scales independently, but it is the interactions of factors and processes at different scales that determine the dynamics of the terrestrial carbon sink. Since experiments and observations are always conducted at specific scales, to understand cross-scale interactions requires mechanistic analysis that is best to be achieved by mechanistic modeling. However, mechanistic ecosystem models are mainly based on data from single-scale experiments and observations and hence have no capacity to simulate mechanistic cross-scale interconnection and interactions of ecosystem processes. New-generation mechanistic ecosystem models based on new ecological theoretical framework are needed to quantify the mechanisms from micro-level fast eco-physiological responses to macro-level slow acclimation in the pattern and structure in disturbed ecosystems. Multi-scale data-model fusion is a recently emerging approach to assimilate multi-scale observational data into mechanistic, dynamic modeling, in which the structure and parameters of mechanistic models for simulating cross-scale interactions are optimized using multi-scale observational data. The models are validated and evaluated at different spatial and temporal scales and r
文摘Heat flow plays an important role in the study ot thermal structure and thermal evolutionof continental margin of the northern South China Sea. The analysis of heat flow value shows that margin heat flow in the northern South China Sea is relatively high setting, but the percentage of crustal heat flow is lower than 35% in terrestrial heat flow. The terrestrial heat flow exhibited a current of rise from the Northern Continental Margin to the Southern Central Basin. However, the proportion of crustal heat flow in terrestrial heat flow slowly dropped down in the same direction. It is suggested that the main factor causing high heat flow setting is the moving up of hot material from asthenosphere.
