Land use and land cover change as the core of coupled human-environment systems has become a potential field of land change science （LCS） in the study of global environmental change. Based on remotely sensed data of...Land use and land cover change as the core of coupled human-environment systems has become a potential field of land change science （LCS） in the study of global environmental change. Based on remotely sensed data of land use change with a spatial resolution of 1 km × 1 km on national scale among every 5 years, this paper designed a new dynamic regionalization according to the comprehensive characteristics of land use change including regional differentiation, physical, economic, and macro-policy factors as well. Spatial pattern of land use change and its driving forces were investigated in China in the early 21 st century. To sum up, land use change pattern of this period was characterized by rapid changes in the whole country. Over the agricultural zones, e.g., Huang-Huai-Hai Plain, the southeast coastal areas and Sichuan Basin, a great proportion of fine arable land were engrossed owing to considerable expansion of the built-up and residential areas, resulting in decrease of paddy land area in southern China. The development of oasis agriculture in Northwest China and the reclamation in Northeast China led to a slight increase in arable land area in northern China. Due to the ＂Grain for Green＂ policy, forest area was significantly increased in the middle and western developing regions, where the vegetation coverage was substantially enlarged, likewise. This paper argued the main driving forces as the implementation of the strategy on land use and regional development, such as policies of ＂Western Development＂, ＂Revitalization of Northeast＂, coupled with rapidly economic development during this period.展开更多
Glaciers in China can be categorized into 3 types, i.e. the maritime (temperate) type, sub-continental (sub-polar) type and extreme Continental (polar) type, which take 22%, 46% and 32% of the total existing glacier a...Glaciers in China can be categorized into 3 types, i.e. the maritime (temperate) type, sub-continental (sub-polar) type and extreme Continental (polar) type, which take 22%, 46% and 32% of the total existing glacier area (59 406 km2) respectively. Researches indicate that glaciers of the three types show different response patterns to the global warming. Since the Maxima of the Little Ice Age (the 17th century), air temperature has risen at a magnitude of 1.3℃on average and the glacier area decreased corresponds to 20% of the present total glacier area in western China. it is estimated that air temperature rise in the 2030s, 2070s and 2100s will be of the order of 0.4-1.2, 1.2-2.7 and 2.1-4.0 K in western China. With these scenarios, glaciers in China will suffer from further shrinkage by 12%, 28% and 45% by the 2030s, 2070s and 2100s. The uncertainties may account for 30%-67% in 2100 in China.展开更多
This study mainly introduces the development of the Flexible Global Ocean-Atmosphere-Land System Model： Grid-point Version 2 （FGOALS-g2） and the preliminary evaluations of its performances based on re- sults from t...This study mainly introduces the development of the Flexible Global Ocean-Atmosphere-Land System Model： Grid-point Version 2 （FGOALS-g2） and the preliminary evaluations of its performances based on re- sults from the pre-industrial control run and four members of historical runs according to the fifth phase of the Coupled Model Intercomparison Project （CMIP5） experiment design. The results suggest that many obvi- ous improvements have been achieved by the FGOALS-g2 compared with the previous version, FGOALS-gl, including its climatological mean states, climate variability, and 20th century surface temperature evolution. For example, FGOALS-g2 better simulates the frequency of tropical land precipitation, East Asian Monsoon precipitation and its seasonal cycle, MJO and ENSO, which are closely related to the updated cumulus parameterization scheme, as well as the alleviation of uncertainties in some key parameters in shallow and deep convection schemes, cloud fraction, cloud macro/microphysical processes and the boundary layer scheme in its atmospheric model. The annual cycle of sea surface temperature along the equator in the Pacific is significantly improved in the new version. The sea ice salinity simulation is one of the unique characteristics of FGOALS-g2, although it is somehow inconsistent with empirical observations in the Antarctic.展开更多
INTRODUCTIONThe“nonspecific” inflammatory bowel diseases ,ulcerative colitis and Crohn,s represent a group of heterogeneous inflammatory and ulcerative disases of the small and large intestines of unknown etiology ,...INTRODUCTIONThe“nonspecific” inflammatory bowel diseases ,ulcerative colitis and Crohn,s represent a group of heterogeneous inflammatory and ulcerative disases of the small and large intestines of unknown etiology ,associated with many gastrointestinal and systemic complications .Appearing initially as isolated cases in Great Britain and northern Europe during the 19th and early 20th centuries ,they have steadily increased numerically and geographically and today are recognized worldwide.展开更多
Carbon dynamics of grasslands on the Qinghai-Tibetan Plateau may play an important role in regional and global carbon cycles. The CENTURY model (Version 4.5) is used to examine temporal and spatial variations of soil ...Carbon dynamics of grasslands on the Qinghai-Tibetan Plateau may play an important role in regional and global carbon cycles. The CENTURY model (Version 4.5) is used to examine temporal and spatial variations of soil organic carbon (SOC) in grasslands on the Plateau for the period from 1960 to 2002. The model successfully simulates the dynamics of aboveground carbon and soil surface SOC at the soil depth of 0-20 cm and the simulated results agree well to the measurements. Examination of SOC for eight typical grasslands shows different patterns of temporal variation in different ecosystems in 1960-2002. The extent of temporal variation increases with the increase of SOC of ecosystem. SOC increases first and decreases quickly then during the period from 1990 to 2000. Spatially, SOC density obtained for the equilibrium condition declines gradually from the southeast to the northwest on the plateau and showed a high heterogeneity in the eastern plateau. The results suggest that (i) SOC den-sity in the alpine grasslands shows remarkable response to climate change during the 42 years, and (ii) the net carbon exchange rate between the alpine grassland ecosystems and the atmosphere increases from 1990 to 2000 as compared with that before 1990.展开更多
The projections of climate change in the globe and East Asia by the NCC/IAPT63 model with the SRES A2 and A1B scenarios have been investigated in this paper. The resultspointed out a global warming of 3.6℃/100 yr and...The projections of climate change in the globe and East Asia by the NCC/IAPT63 model with the SRES A2 and A1B scenarios have been investigated in this paper. The resultspointed out a global warming of 3.6℃/100 yr and 2.5℃/100 yr for A2 and A1B during the 21stcentury, respectively. The warming in high and middle latitudes will be more obvious than that inlow latitudes, especially in the winter hemisphere. The warming of 5.1℃/100 yr for A2 and 3.6℃/100 yr for A1B over East Asia in the 21st century will be much higher than that in the globe. Theglobal mean precipitation will increase by about 4.3%/100 yr for A2 and 3.4%/100 yr for A1B in the21st century, respectively. The precipitation will increase in most parts of the low and highlatitudes and decrease in some regions of the subtropical latitudes. The linear trends of the annualmean precipitation anomalies over East Asia will be 9.8%/100 yr for A2 and 5.2%/100 yr for A1B,respectively. The drier situations will occur over the northwestern and southeastern parts of EastAsia. The changes of the annual mean temperature and precipitation in the globe for the 21st centuryby the NCC/IAP T63 model with SRES A2 and A1B scenarios are in agreement with a number of the modelprojections.展开更多
Studies on the 20th century climate change in China have revealed that under the background of global warming over the past century, climate in China has also experienced significant change with mean annual temperatur...Studies on the 20th century climate change in China have revealed that under the background of global warming over the past century, climate in China has also experienced significant change with mean annual temperature increased by about 0.5 oC. More reliable results for the latter part of the 20th century indicate that the largest warming occurred in Northwest China, North China and Northeast China, and the warming in winter is most significant. Although no obvious increase or decrease trends were detected for mean precipitation over China in the past half century, regional differences are very distinct. In the middle and lower reaches of the Yangtze River, precipitation increased, while that in the Yellow River Basin markedly decreased. Studies suggest that climate change in China seems to be related not only with the internal factors such as ENSO, PDO, and the others, but also with the anthropogenic effects such as greenhouse gas emissions, and land use. The future climate change studies in China seem to be important in narrowing understanding the nature of China's climate change and its main causes, since it is significant for projection and for impact assessment of climate change in the future.展开更多
In order to assess the performance of two versions of the IAP/LASG Flexible Global Ocean-Atmosphere- Land System （FGOALS） model, simulated changes in surface air temperature （SAT）, from natural and an- thropogenie...In order to assess the performance of two versions of the IAP/LASG Flexible Global Ocean-Atmosphere- Land System （FGOALS） model, simulated changes in surface air temperature （SAT）, from natural and an- thropogenie forcings, were compared to observations for the period 1850-2005 at global, hemispheric, conti- nental and regional scales. The global and hemispheric averages of SAT and their land and ocean components during 1850-2005 were well reproduced by FGOALS-g2, as evidenced by significant correlation coefficients and small RMSEs. The significant positive correlations were firstly determined by the warming trends, and secondly by interdecadal fluctuations. The abilities of the models to reproduce interdecadal SAT variations were demonstrated by both wavelet analysis and significant positive correlations for detrended data. The observed land-sea thermal contrast change was poorly simulated. The major weakness of FGOALS-s2 was an exaggerated warming response to anthropogenic forcing, with the simulation showing results that were far removed from observations prior to the 1950s. The observations featured warming trends （1906-2005） of 0.71, 0.68 and 0.79℃ （100 yr）-1 for global, Northern and Southern Hemispheric averages, which were overestimated by FGOALS-s2 [1.42, 1.52 and 1.13~C （100 yr）-1] but underestimated by FGOALS-g2 [0.69, 0.68 and 0.73~C （100 yr）-l]. The polar amplification of the warming trend was exaggerated in FGOALS- s2 but weakly reproduced in FGOALS-g2. The stronger response of FGOALS-s2 to anthropogenic forcing was caused by strong sea-ice albedo feedback and water vapor feedback. Examination of model results in 15 selected subcontinental-scale regions showed reasonable performance for FGOALS-g2 over most regions. However, the observed warming trends were overestimated by FGOALS-s2 in most regions. Over East Asia, the meridional gradient of the warming trend simulated by FGOALS-s2 （FGOALS-g2） was stronger （weaker） than observed.展开更多
Geographically explicit historical land use and land cover datasets are increasingly required in studies of climatic and ecological effects of human activities. In this study, using historical population data as a pro...Geographically explicit historical land use and land cover datasets are increasingly required in studies of climatic and ecological effects of human activities. In this study, using historical population data as a proxy, the provincial cropland areas of Qinghai province and the Tibet Autonomous Region （TAR） for 1900, 1930, and 1950 were estimated. The cropland areas of Qinghai and the TAR for 1980 and 2000 were obtained from published statistical data with revisions. Using a land suitability for cultivation model, the provincial cropland areas for the 20th century were converted into crop cover datasets with a resolution of 1 x 1 km. Finally, changes of sediment retention due to crop cover change were assessed using the sediment delivery ratio module of the Integrated Valuation of Ecosystem Services and Trade-offs （In- VEST） model （version 3.3.1）. There were two main results. （1） For 1950-1980 the fractional cropland area increased from 0.32% to 0.48% and land use clearly intensified in the Tibetan Plateau （TP）, especially in the Yellow River-Huangshui River Valley （YHRV） and the mid- stream of the Yarlung Zangbo River and its two tributaries valley （YRTT）. For other periods of the 20th century, stability was the main trend. （2） For 1950-1980, sediment export increased rapidly in the Minhe autonomous county of the YHRV, and in the Nianchu River and Lhasa River basins of the YRTT, which means that sediment retention clearly decreased in these regions over this period. The results of this assessment provide scientific support for con- servation planning, development planning, or restoration activities.展开更多
It is of interest in an era of increasing biomedical sophisticaton to recall that a relatively short time ago, early in the 20th century, ‘simple' ulcerative colitis was an obscure ‘medical curiosity' emergi...It is of interest in an era of increasing biomedical sophisticaton to recall that a relatively short time ago, early in the 20th century, ‘simple' ulcerative colitis was an obscure ‘medical curiosity' emerging slowly from an unknown past. Crohn's disease was yet unidentified as a separate entity although careful review of the IBD literature documented its early presence, masquerading as ‘intestinal tuberculosis'. Into the 1930s, the etiology and pathogenesis of ulcerative colitis and Crohn's disease were unknown, and investigative hypotheses were scarce. Therapeutic resources were limited and treatment was primitive. At a time of limited biomedical knowledge and minimal clinical awareness, unsubstantiated views prevailed, including ‘vague reactions to foods' (sugar,margarine, corn flakes), deficiency of a ‘protective factor'in pig intestine, and psychiatric disease.展开更多
Based on data from 10-year field experiments on residue/fertilizer management in the dryland farming region of northern China, Century model was used to simulate the site-specific ecosystem dynamics through adjustment...Based on data from 10-year field experiments on residue/fertilizer management in the dryland farming region of northern China, Century model was used to simulate the site-specific ecosystem dynamics through adjustment of the model＇s parameters, and the applicability of the model to propose soil organic carbon （SOC） management temporally and spatially, in cases such as of tillage/residue/fertilization management options, was identified v/a scenario analysis.Results between simulations and actual measurements were in close agreement when appropriate applications of stover,manure and inorganic fertilizer were combined. Simulations of extreme C/N ratios with added organic materials tended to underestimate the measured effects. Scenarios of changed tillage methods, residue practices and fertilization options showed potential to maintain and enhance SOC in the long run, while increasing inorganic N slowed down the SOC turnover rate but did not create a net C sink without any organic C input. The Century model simulation showed a good relationship between annual C inputs to the soil and the rate of C sequestration in the top 20 cm layer and provided quantitative estimations of changes in parameters crucial for sustainable land use and management. Conservation tillage practices for sustainable land use should be integrated with residue management and appreciable organic and inorganic fertilizer application, adapted according to the local residue resource, soil fertility and production conditions. At least 50% residue return into the soil was needed annually for maintenance of SOC balance, and manure amendment was important for enhancement of SOC in small crop-livestock systems in which crop residue land application was limited.展开更多
The projections of climate changes in China for the 21st century by about 40climate scenarios and multi-model ensembles have been investigated in this research. All the modelswith the different scenarios project a war...The projections of climate changes in China for the 21st century by about 40climate scenarios and multi-model ensembles have been investigated in this research. All the modelswith the different scenarios project a warming of 1.2℃ to 9.2℃ in China by the end of 21stcentury. Most of the projections point show the increasing of precipitation in China for the 21stcentury.展开更多
Based on time series and linear trend analysis, the authors evaluated the performance of the fourth gen- eration atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy...Based on time series and linear trend analysis, the authors evaluated the performance of the fourth gen- eration atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences （IAP AGCM4.0）, in simulating surface air temperature （SAT） during the twentieth century over China and the globe. The numerical experiment is con- ducted by driving the model with the observed sea surface temperature and sea ice. It is shown that IAP AGCM4.0 can simulate the warming trend of the global SAT, with the major wanning regions in the high latitudes of the Northern Hemisphere and the mid-latitudes of the South- ern Hemisphere. While the simulated trend over the whole globe is close to the observation, the model trader- estimates the observed trend over the continents. More- over, the model simulates the spatial distribution of SAT in China, with a bias of approximately -2℃ in eastern China, but with a more serious bias in western China. Compared with the global mean, however, the correlation coefficient between the simulation and observation in China is significantly lower, indicating that there is large uncertainty in simulating regional climate change.展开更多
基金National Basic Research Program of China, No.2009CB421105National Key Technology R&D Program, No.2006BAC08B00Knowledge Innovation Program of the CAS, No.KSCX1-YW-09-01
文摘Land use and land cover change as the core of coupled human-environment systems has become a potential field of land change science （LCS） in the study of global environmental change. Based on remotely sensed data of land use change with a spatial resolution of 1 km × 1 km on national scale among every 5 years, this paper designed a new dynamic regionalization according to the comprehensive characteristics of land use change including regional differentiation, physical, economic, and macro-policy factors as well. Spatial pattern of land use change and its driving forces were investigated in China in the early 21 st century. To sum up, land use change pattern of this period was characterized by rapid changes in the whole country. Over the agricultural zones, e.g., Huang-Huai-Hai Plain, the southeast coastal areas and Sichuan Basin, a great proportion of fine arable land were engrossed owing to considerable expansion of the built-up and residential areas, resulting in decrease of paddy land area in southern China. The development of oasis agriculture in Northwest China and the reclamation in Northeast China led to a slight increase in arable land area in northern China. Due to the ＂Grain for Green＂ policy, forest area was significantly increased in the middle and western developing regions, where the vegetation coverage was substantially enlarged, likewise. This paper argued the main driving forces as the implementation of the strategy on land use and regional development, such as policies of ＂Western Development＂, ＂Revitalization of Northeast＂, coupled with rapidly economic development during this period.
文摘Glaciers in China can be categorized into 3 types, i.e. the maritime (temperate) type, sub-continental (sub-polar) type and extreme Continental (polar) type, which take 22%, 46% and 32% of the total existing glacier area (59 406 km2) respectively. Researches indicate that glaciers of the three types show different response patterns to the global warming. Since the Maxima of the Little Ice Age (the 17th century), air temperature has risen at a magnitude of 1.3℃on average and the glacier area decreased corresponds to 20% of the present total glacier area in western China. it is estimated that air temperature rise in the 2030s, 2070s and 2100s will be of the order of 0.4-1.2, 1.2-2.7 and 2.1-4.0 K in western China. With these scenarios, glaciers in China will suffer from further shrinkage by 12%, 28% and 45% by the 2030s, 2070s and 2100s. The uncertainties may account for 30%-67% in 2100 in China.
基金supported by the National"863"Project(Grant No.2010AA012304)the"973"Project(Grant No.2010CB951904)+1 种基金the China Meteorological Administration R&D Special Fund for Public Welfare(meteorology)(Grant No.GYHY201006014)the National Natural Science Foundation of China(Grant Nos.40923002 and 41005053)
文摘This study mainly introduces the development of the Flexible Global Ocean-Atmosphere-Land System Model： Grid-point Version 2 （FGOALS-g2） and the preliminary evaluations of its performances based on re- sults from the pre-industrial control run and four members of historical runs according to the fifth phase of the Coupled Model Intercomparison Project （CMIP5） experiment design. The results suggest that many obvi- ous improvements have been achieved by the FGOALS-g2 compared with the previous version, FGOALS-gl, including its climatological mean states, climate variability, and 20th century surface temperature evolution. For example, FGOALS-g2 better simulates the frequency of tropical land precipitation, East Asian Monsoon precipitation and its seasonal cycle, MJO and ENSO, which are closely related to the updated cumulus parameterization scheme, as well as the alleviation of uncertainties in some key parameters in shallow and deep convection schemes, cloud fraction, cloud macro/microphysical processes and the boundary layer scheme in its atmospheric model. The annual cycle of sea surface temperature along the equator in the Pacific is significantly improved in the new version. The sea ice salinity simulation is one of the unique characteristics of FGOALS-g2, although it is somehow inconsistent with empirical observations in the Antarctic.
文摘INTRODUCTIONThe“nonspecific” inflammatory bowel diseases ,ulcerative colitis and Crohn,s represent a group of heterogeneous inflammatory and ulcerative disases of the small and large intestines of unknown etiology ,associated with many gastrointestinal and systemic complications .Appearing initially as isolated cases in Great Britain and northern Europe during the 19th and early 20th centuries ,they have steadily increased numerically and geographically and today are recognized worldwide.
基金Supported by the Global Environmental Research Program of the Ministry of the Environment, Japan (Grant No. S1)by an Innovation Project of the Chinese Academy of Sciences (Grant No. KZCX3-SW-446)
文摘Carbon dynamics of grasslands on the Qinghai-Tibetan Plateau may play an important role in regional and global carbon cycles. The CENTURY model (Version 4.5) is used to examine temporal and spatial variations of soil organic carbon (SOC) in grasslands on the Plateau for the period from 1960 to 2002. The model successfully simulates the dynamics of aboveground carbon and soil surface SOC at the soil depth of 0-20 cm and the simulated results agree well to the measurements. Examination of SOC for eight typical grasslands shows different patterns of temporal variation in different ecosystems in 1960-2002. The extent of temporal variation increases with the increase of SOC of ecosystem. SOC increases first and decreases quickly then during the period from 1990 to 2000. Spatially, SOC density obtained for the equilibrium condition declines gradually from the southeast to the northwest on the plateau and showed a high heterogeneity in the eastern plateau. The results suggest that (i) SOC den-sity in the alpine grasslands shows remarkable response to climate change during the 42 years, and (ii) the net carbon exchange rate between the alpine grassland ecosystems and the atmosphere increases from 1990 to 2000 as compared with that before 1990.
基金This research is supported by the IPCC-China Special Climate Projects and the Laboratory for Climate Studies of ChinaMeteorological Administration.
文摘The projections of climate change in the globe and East Asia by the NCC/IAPT63 model with the SRES A2 and A1B scenarios have been investigated in this paper. The resultspointed out a global warming of 3.6℃/100 yr and 2.5℃/100 yr for A2 and A1B during the 21stcentury, respectively. The warming in high and middle latitudes will be more obvious than that inlow latitudes, especially in the winter hemisphere. The warming of 5.1℃/100 yr for A2 and 3.6℃/100 yr for A1B over East Asia in the 21st century will be much higher than that in the globe. Theglobal mean precipitation will increase by about 4.3%/100 yr for A2 and 3.4%/100 yr for A1B in the21st century, respectively. The precipitation will increase in most parts of the low and highlatitudes and decrease in some regions of the subtropical latitudes. The linear trends of the annualmean precipitation anomalies over East Asia will be 9.8%/100 yr for A2 and 5.2%/100 yr for A1B,respectively. The drier situations will occur over the northwestern and southeastern parts of EastAsia. The changes of the annual mean temperature and precipitation in the globe for the 21st centuryby the NCC/IAP T63 model with SRES A2 and A1B scenarios are in agreement with a number of the modelprojections.
文摘Studies on the 20th century climate change in China have revealed that under the background of global warming over the past century, climate in China has also experienced significant change with mean annual temperature increased by about 0.5 oC. More reliable results for the latter part of the 20th century indicate that the largest warming occurred in Northwest China, North China and Northeast China, and the warming in winter is most significant. Although no obvious increase or decrease trends were detected for mean precipitation over China in the past half century, regional differences are very distinct. In the middle and lower reaches of the Yangtze River, precipitation increased, while that in the Yellow River Basin markedly decreased. Studies suggest that climate change in China seems to be related not only with the internal factors such as ENSO, PDO, and the others, but also with the anthropogenic effects such as greenhouse gas emissions, and land use. The future climate change studies in China seem to be important in narrowing understanding the nature of China's climate change and its main causes, since it is significant for projection and for impact assessment of climate change in the future.
基金supported by the National High Technology Research and Development Program of China(Grant No.2010AA012304)National Program on Key Basic Research Project of China(Grant No.2010CB951904)NSFC project(Grant No.41125017)
文摘In order to assess the performance of two versions of the IAP/LASG Flexible Global Ocean-Atmosphere- Land System （FGOALS） model, simulated changes in surface air temperature （SAT）, from natural and an- thropogenie forcings, were compared to observations for the period 1850-2005 at global, hemispheric, conti- nental and regional scales. The global and hemispheric averages of SAT and their land and ocean components during 1850-2005 were well reproduced by FGOALS-g2, as evidenced by significant correlation coefficients and small RMSEs. The significant positive correlations were firstly determined by the warming trends, and secondly by interdecadal fluctuations. The abilities of the models to reproduce interdecadal SAT variations were demonstrated by both wavelet analysis and significant positive correlations for detrended data. The observed land-sea thermal contrast change was poorly simulated. The major weakness of FGOALS-s2 was an exaggerated warming response to anthropogenic forcing, with the simulation showing results that were far removed from observations prior to the 1950s. The observations featured warming trends （1906-2005） of 0.71, 0.68 and 0.79℃ （100 yr）-1 for global, Northern and Southern Hemispheric averages, which were overestimated by FGOALS-s2 [1.42, 1.52 and 1.13~C （100 yr）-1] but underestimated by FGOALS-g2 [0.69, 0.68 and 0.73~C （100 yr）-l]. The polar amplification of the warming trend was exaggerated in FGOALS- s2 but weakly reproduced in FGOALS-g2. The stronger response of FGOALS-s2 to anthropogenic forcing was caused by strong sea-ice albedo feedback and water vapor feedback. Examination of model results in 15 selected subcontinental-scale regions showed reasonable performance for FGOALS-g2 over most regions. However, the observed warming trends were overestimated by FGOALS-s2 in most regions. Over East Asia, the meridional gradient of the warming trend simulated by FGOALS-s2 （FGOALS-g2） was stronger （weaker） than observed.
基金Foundation： Strategic Priority Research Program of the Chinese Academy of Sciences, No.XDB03030500 National Natural Science Foundation of China, No.41371120 The Key Foundation Project of Basic Work of the Min- istry of Science and Technology of China, No.2012FY 111400
文摘Geographically explicit historical land use and land cover datasets are increasingly required in studies of climatic and ecological effects of human activities. In this study, using historical population data as a proxy, the provincial cropland areas of Qinghai province and the Tibet Autonomous Region （TAR） for 1900, 1930, and 1950 were estimated. The cropland areas of Qinghai and the TAR for 1980 and 2000 were obtained from published statistical data with revisions. Using a land suitability for cultivation model, the provincial cropland areas for the 20th century were converted into crop cover datasets with a resolution of 1 x 1 km. Finally, changes of sediment retention due to crop cover change were assessed using the sediment delivery ratio module of the Integrated Valuation of Ecosystem Services and Trade-offs （In- VEST） model （version 3.3.1）. There were two main results. （1） For 1950-1980 the fractional cropland area increased from 0.32% to 0.48% and land use clearly intensified in the Tibetan Plateau （TP）, especially in the Yellow River-Huangshui River Valley （YHRV） and the mid- stream of the Yarlung Zangbo River and its two tributaries valley （YRTT）. For other periods of the 20th century, stability was the main trend. （2） For 1950-1980, sediment export increased rapidly in the Minhe autonomous county of the YHRV, and in the Nianchu River and Lhasa River basins of the YRTT, which means that sediment retention clearly decreased in these regions over this period. The results of this assessment provide scientific support for con- servation planning, development planning, or restoration activities.
文摘It is of interest in an era of increasing biomedical sophisticaton to recall that a relatively short time ago, early in the 20th century, ‘simple' ulcerative colitis was an obscure ‘medical curiosity' emerging slowly from an unknown past. Crohn's disease was yet unidentified as a separate entity although careful review of the IBD literature documented its early presence, masquerading as ‘intestinal tuberculosis'. Into the 1930s, the etiology and pathogenesis of ulcerative colitis and Crohn's disease were unknown, and investigative hypotheses were scarce. Therapeutic resources were limited and treatment was primitive. At a time of limited biomedical knowledge and minimal clinical awareness, unsubstantiated views prevailed, including ‘vague reactions to foods' (sugar,margarine, corn flakes), deficiency of a ‘protective factor'in pig intestine, and psychiatric disease.
基金Project supported by the National High Technology Research and Development Program of China (863 Program)(Nos. 2002AA2Z4311 and 2002AA2Z4021), and the Soil Technology Group in Wageningen University, the Netherlands.
文摘Based on data from 10-year field experiments on residue/fertilizer management in the dryland farming region of northern China, Century model was used to simulate the site-specific ecosystem dynamics through adjustment of the model＇s parameters, and the applicability of the model to propose soil organic carbon （SOC） management temporally and spatially, in cases such as of tillage/residue/fertilization management options, was identified v/a scenario analysis.Results between simulations and actual measurements were in close agreement when appropriate applications of stover,manure and inorganic fertilizer were combined. Simulations of extreme C/N ratios with added organic materials tended to underestimate the measured effects. Scenarios of changed tillage methods, residue practices and fertilization options showed potential to maintain and enhance SOC in the long run, while increasing inorganic N slowed down the SOC turnover rate but did not create a net C sink without any organic C input. The Century model simulation showed a good relationship between annual C inputs to the soil and the rate of C sequestration in the top 20 cm layer and provided quantitative estimations of changes in parameters crucial for sustainable land use and management. Conservation tillage practices for sustainable land use should be integrated with residue management and appreciable organic and inorganic fertilizer application, adapted according to the local residue resource, soil fertility and production conditions. At least 50% residue return into the soil was needed annually for maintenance of SOC balance, and manure amendment was important for enhancement of SOC in small crop-livestock systems in which crop residue land application was limited.
基金This research is supported by the China-IPCC special climate project and LCS projects.
文摘The projections of climate changes in China for the 21st century by about 40climate scenarios and multi-model ensembles have been investigated in this research. All the modelswith the different scenarios project a warming of 1.2℃ to 9.2℃ in China by the end of 21stcentury. Most of the projections point show the increasing of precipitation in China for the 21stcentury.
基金supported by the Strategic Priority Research Program-Climate Change: Carbon Budget and Related Issues of the Chinese Academy of Sciences (Grant No. XDA05110201)the Development and Validation of High Resolution Climate System Model of the National Basic Research Program of China (Grant No.2010CB951901)
文摘Based on time series and linear trend analysis, the authors evaluated the performance of the fourth gen- eration atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences （IAP AGCM4.0）, in simulating surface air temperature （SAT） during the twentieth century over China and the globe. The numerical experiment is con- ducted by driving the model with the observed sea surface temperature and sea ice. It is shown that IAP AGCM4.0 can simulate the warming trend of the global SAT, with the major wanning regions in the high latitudes of the Northern Hemisphere and the mid-latitudes of the South- ern Hemisphere. While the simulated trend over the whole globe is close to the observation, the model trader- estimates the observed trend over the continents. More- over, the model simulates the spatial distribution of SAT in China, with a bias of approximately -2℃ in eastern China, but with a more serious bias in western China. Compared with the global mean, however, the correlation coefficient between the simulation and observation in China is significantly lower, indicating that there is large uncertainty in simulating regional climate change.
