It is of importance to enhance the urban areas'capacity for population aggregation in underdeveloped regions,aiming to rectify the imbalanced and insufficient pattern of economic development in China.Taking the Ta...It is of importance to enhance the urban areas'capacity for population aggregation in underdeveloped regions,aiming to rectify the imbalanced and insufficient pattern of economic development in China.Taking the Taiyuan Metropolitan Area(TMA)in central China as a case study,this paper examines the evolutionary process and characteristics of population agglomeration from 2000 to 2020,and identifies factors associated with agglomeration and their spatial effects.The findings indicated that:1)against the background of sustained population shrinkage in the provincial area,the TMA showed a demographic trend of steady increase,albeit with a decelerated growth rate.In the metropolitan area,urban population size continued to grow rapidly,whereas the rural areas endured sustained losses.Disparities in city size continued to widen,and the polarization of concentrated population in the core cities kept increasing.2)Agglomerations in both secondary and service industries had significant positive effects on local population agglomeration,with the former effect being stronger.Regional economic development,government fiscal expenditure,and financial advancement all contributed to facilitating local population clustering.From a spatial spillover perspective,service agglomeration and financial development promoted population agglomeration in surrounding areas.Conversely,fiscal expenditure inhibited such agglomeration.As for industrial agglomeration and regional economic development,their spatial spillover effects were non-significant.The results obtained reveal several policy implications aimed at enhancing the population agglomeration capacity of the metropolitan area in underdeveloped regions during the new era.展开更多
Restoration and reconstruction of the degraded Tarim River ecosystem is an important challenge. A goal of an ecological water conveyance project is to protect and restore the natural vegetation in the lower reaches of...Restoration and reconstruction of the degraded Tarim River ecosystem is an important challenge. A goal of an ecological water conveyance project is to protect and restore the natural vegetation in the lower reaches of Tadm River by transferring water from Bosten Lake, through the river channel, to the lower reaches. This study describes the changes in groundwater depth during the water transfer and the respondence of riparian vegetation to alterations in groundwater levels. The results indicate that groundwater depth along the Tarim River channel has a significant spatial-temporal component. Groundwater levels closest to the river channel show the most immediate and pronounced changes as a response to water transfer while those further away respond more slowly, although the observed change appears to be longer in duration. With a rise in the groundwater level, natural vegetation responded with higher growth rates, biomass and biodiversity. These favorable changes show that it is feasible to protect and restore the degraded natural vegetation by raising the groundwater depth. Plant communities are likely to reflect the hysteresis phenomenon, requiting higher water levels to initiate and stimulate desired growth than what may be needed to maintain the plant community. Because different species have different ecologies, including different root depths and densities and water needs, their response to increasing water availability will be spatially and temporally heterogenous. The response of vegetation is also influenced by microtopography and watering style. This paper discusses strategies for the protection and restoration of the degraded vegetation in the lower reaches of the Tarim River and provides information to complement ongoing theoretical research into ecological restoration in add or semi-arid ecosystems.展开更多
Land cover in the Chinese Loess Plateau has undergone dramatic changes since the late 1980s.Revealing the trend in land cover change and eco-environmental quality response of different geomorphic units in this stage i...Land cover in the Chinese Loess Plateau has undergone dramatic changes since the late 1980s.Revealing the trend in land cover change and eco-environmental quality response of different geomorphic units in this stage is a realistic requirement for promoting sustainable development of the Chinese Loess Plateau.Based on the data of geomorphic units and land cover in 1990,2000,2010 and 2018 of the Chinese Loess Plateau,we studied the trend of land cover change and eco-environmental quality response of different geomorphic units by using a significance index of land cover change,a proportion index of land cover change and an eco-environmental response model.The results indicated that from 1990 to 2018,the areas of forestland and construction land substantially increased,whereas those of cropland,grassland,wetland and unused land considerably decreased.Land cover change exhibited large geomorphic differences,and the main conversion of land cover was from cropland into other land types.Unstable trend of land cover change in the loess tablelands and sandy loess hills declined,whereas the unstable trends in the other geomorphic units enhanced.Eco-environmental quality varied among different geomorphic units.The expansion of construction land and degradation of forestland,grassland and wetland resulted in the deterioration of eco-environmental quality.The conversion of cropland and unused land into forestland and grassland,and the conversion of grassland into forestland were the main factors that drove the improvement of eco-environmental quality.The findings of this study may provide theoretical reference and support decision making for the optimization of land use structure and the improvement of eco-environmental quality on the Chinese Loess Plateau.展开更多
The nature heritages are the precious legacy of nature with outstanding scientific and aesthetic value. They are quite different from other common ecotourism areas, because of its original and unique system, sensitive...The nature heritages are the precious legacy of nature with outstanding scientific and aesthetic value. They are quite different from other common ecotourism areas, because of its original and unique system, sensitive and vulnerable landscape, and peripheral cultural features. Therefore, the tourism development in the nature heritage sites should be on the premise of ecological security. The evaluation index system of tourism ecological security in nature heritage sites was constructed in this article by AHP and Delphi methods, including nature ecological security, landscape visual security and local culture ecological security, and the security thresholds of indices were also established. In the indices' weights of the evaluation model, the nature ecological security ranked the highest, followed by tourist landscape visual security and culture ecological security, which reflected the influence degree of the limited factor to tourism ecological security. Then, this paper carried out an empirical study of Kanas of Xinjiang Uygur Autonomous Region, China, which has the potential to be the World Nature Heritage. On the basis of the data attained from survey and observation on the spot, as well as questionnaire answered by tourists and local communities, the ecological security status in Kanas was evaluated. The result showed that the status of Kanas tourism ecological security was better, but there had some limiting factors. Lastly, effective measures were put forward to ensure its ecological security.展开更多
Sedimentary sequences in the Subei Basin are complex and have been affected by interactions between the ocean and rivers since the Late Pliocene, including the Yellow River, Huaihe River, and the Yangtze River. This s...Sedimentary sequences in the Subei Basin are complex and have been affected by interactions between the ocean and rivers since the Late Pliocene, including the Yellow River, Huaihe River, and the Yangtze River. This sedimentary evolution, in particular the timing of Pleistocene transgressions, has long been a matter of controversy owing to the lack of precise chronological evidence. The aim of this study is to explore the evolution of the sedimentary environment throughout the past 3.00 Ma in this region on the basis of a comprehensive analysis of particle size and foraminifera and ostracods collected in the TZK9 core from the Subei Basin combined with geochronological studies of magnetostratigraphy, AMS^(14)C and optically stimulated luminescence(OSL). The results show that fluvial facies in the sedimentary environment from 3.00 to 1.01 Ma. There were fluvial facies and reflects six sea-level high stands from 1.01 to 0.25 Ma. The study area was affected by four large-scale transgressions since 0.25 Ma. The four marine sedimentary layers known as DU7(buried at 48–52 m), DU5(buried at 35–41 m), DU3(buried at 16–23 m), and DU1(buried at 2–4 m) are recorded in the MIS7(210–250 ka), MIS5, MIS3, and Holocene, respectively. The magnitude of the DU5 transgression was identical to that of the DU3 transgression, both were larger than the DU7 transgression, and the DU1 transgression was the weakest. The variation of transgression strength reflects the influence of global changes in sea level, tectonic subsidence, shell ridges, and sand dams. In the TZK9 core, we found evidence of seven sea-level high stands from the Early–Middle Pleistocene, and the first one caused by regional rapid subsidence and could be traced back to 0.83-0.84 Ma. The sea-level high stands and the age of the first one recorded above was different from other cores in eastern China, this was caused by the lack of absolute age control and the differences in paleotopography during this period. This study reconstructs sedimentary evolution, determines the transgression and its age, establishes the chronology since the Late Pliocene, and provides a scientific framework for further paleoenvironmental and tectonic studies. The results of this study highlight the important role that local tectonics and global sea level play in the sedimentary evolution and transgressions that have occurred in the western Subei Basin.展开更多
In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected...In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected area, whereas the grazed area was continuously grazed at 8.5 dry sheep equivalent(DSE)/hm2. In the current research, soil and plant samples were taken from grazed and fenced areas to examine changes in vegetation and soil properties in 2005, 2006 and 2008. Results showed that vegetation characteristics and soil properties improved significantly in the fenced area compared with the grazed area. In the protected area the vegetation cover, height and above- and belowground biomass increased significantly. Soil pH, electrical conductivity and bulk density decreased significantly, but soil organic carbon and total nitrogen concentration increased greatly in the protected area. By comparing the vegetation and soil characteristics with pre-degraded grassland, we found that vegetation can recover 6 years after fencing, and soil pH can be restored 8 years after fencing. However, the restoration of soil organic carbon, total nitrogen and total phosphorus concentrations needed 16, 30 and 19 years, respectively. It is recommended that the stocking rate should be reduced to 1/3 of the current carrying capacity, or that a grazing regime of 1-year of grazing followed by a 2-year rest is adopted to sustain the current status of vegetation and soil resources. However, if N fertilizer is applied, the rest period could be shortened, depending on the rate of application.展开更多
As a major aspect of the ′China Model′, urbanization in China is being heatedly discussed in the Anglophone literature in the last two decades. By considering China′s urbanization as a ′testing ground′ of ′west...As a major aspect of the ′China Model′, urbanization in China is being heatedly discussed in the Anglophone literature in the last two decades. By considering China′s urbanization as a ′testing ground′ of ′western′ theories, these studies are important for the understanding of China′s ongoing urban restructuring and exchanging knowledge with ′western′ insights. Based on a survey of existing studies, this paper identifies various endogenous and exogenous concepts and explanations of China′s urbanization. It is suggested that China′s urbanization is mainly driven by a combination of political decentralization and neoliberalization with various forms of social stratification and mobility. However, it is argued that the distinctness of the ′China Model′, which is usually used to support the legitimacy of studies of China′s urbanization, has led to many controversial arguments and diminished the due contributions of Chinese scholars in the knowledge production of China′s urbanization. To consolidate the legitimacy of studies on China′s urbanization and enhance the roles of Chinese scholars, we suggest future studies to pay more attentions to the fundamental theories with looser constraints and ′true questions′ on China′s urbanization.展开更多
During the reform era, Chinese cities witnessed dramatic institutional transformation and spatial restructuring in general and profound change of commuting patterns in particular. Using household surveys collected in ...During the reform era, Chinese cities witnessed dramatic institutional transformation and spatial restructuring in general and profound change of commuting patterns in particular. Using household surveys collected in Guangzhou, China, in 2001, 2005 and 2010, excess commuting measurements are estimated. Excess commuting shows an overall trend of increasing during 1990–1999, and then declining during 2000–2010. We argue that deepening marketization of the jobs and housing sectors has induced spatial separation of jobs and housing. In other words, institutional transition and urban spatial restructuring are underpinning the changes of commuting patterns in Chinese cities. Excess commuting has strong relationship with individual socio-demographic status, which is by and large due to the increasing flexibilities of jobs and housing location choices enjoyed by urban residents. The findings call for considerations on balancing jobs-housing in making public policies relevant to urban development in general, and land use and transportation in particular.展开更多
The availability of high-resolution satellite precipitation measurement products provides an opportunity to monitor precipitation over large and complex terrain and thus accurately evaluate the climatic,hydrological a...The availability of high-resolution satellite precipitation measurement products provides an opportunity to monitor precipitation over large and complex terrain and thus accurately evaluate the climatic,hydrological and ecological conditions in those regions.The Global Precipitation Measurement(GPM)mission is an important new program designed for global satellite precipitation estimation,but little information has been reported on the applicability of the GPM’s products for the Tibetan Plateau(TP).The object of this study is to evaluate the accuracy of the Integrated Multi-Satellite Retrievals for GPM(IMERG)Final Run product under different terrain and climate conditions over the TP by using 78 ground gauges from April 2014 to December 2017.The results showed the following:(1)the 3-year average daily precipitation estimation in the IMERG agrees well with the rain gauge observations(R^2=0.58,P<0.01),and IMERG also has a considerable ability to detect precipitation,as indicated by a high probability of detection(78%-98%)and critical success index(65%-85%);(2)IMERG performed better at altitudes from 3000 m to 4000 m with a small relative bias(RB)of 6.4%.Precipitation change was not significantly affected by local relief;(3)the climate system of the TP was divided into four climate groups with a total of 12 climate types based on the K?ppen climate classification system,and IMERG performed well in all climate types with the exception of the arid-desert-cold climate(Bwk)type.Furthermore,although IMERG showed the potential to detect snowfall,it still exhibits deficiencies in identifying light and moderate snow.These results indicate that IMERG could provide more accurate precipitation data if its retrieval algorithm was improved for complex terrain and arid regions.展开更多
Study results in this paper have indicated that the Holocene climate in Xinjiang, Northwestem China has been alternating between wet and dry conditions, and was punctuated with a series of abrupt climate shifts. A sed...Study results in this paper have indicated that the Holocene climate in Xinjiang, Northwestem China has been alternating between wet and dry conditions, and was punctuated with a series of abrupt climate shifts. A sediment core taken from Barkol Lake in the northern Xinjiang of Northwest China was analyzed at 1 cm interval for grain-size distribution. Abrupt climate shifts revealed by the grain-size proxy occurred at ca 1.4, 3.0, 4.3, 5.6, 8.0 cal kyr B.E, which were well correlated to both the abrupt shifts recorded in the North Atlantic Ocean (NAO) and the Holocene sea surface temperature (SST) cooling events in the Arabian Ocean. The correlation indicated that the climatic changes in the extreme arid Northwest China were associated with the NAO, probably via the North Atlantic Oscillation-affected westerly winds. The strength and position of westerly winds probably modulated the Siberian-Mongolian high- pressure system (winter monsoon), and played an important role in climate change of Northwest China. Moreover, an evident drought interval during the middle Holocene was also revealed by grain-size proxy.展开更多
An undersea volcano at Hunga Tonga-Hunga Ha'apai(HTHH)near the South Pacific island nation of Tonga,erupted violently on 15 January 2022.Potential climate impact of the HTHH volcanic eruption is of great concern t...An undersea volcano at Hunga Tonga-Hunga Ha'apai(HTHH)near the South Pacific island nation of Tonga,erupted violently on 15 January 2022.Potential climate impact of the HTHH volcanic eruption is of great concern to the public;here,we intend to size up the impact of the HTHH eruption from a historical perspective.The influence of historical volcanic eruptions on the global climate are firstly reviewed,which are thought to have contributed to decreased surface temperature,increased stratospheric temperature,suppressed global water cycle,weakened monsoon circulation and El Niño-like sea surface temperature.Our understanding of the impacts of past volcanic eruptions on global-scale climate provides potential implication to evaluate the impact of the HTHH eruption.Based on historical simulations,we estimate that the current HTHH eruption with an intensity of 0.4 Tg SO_(2)injection will decrease the global mean surface temperature by only 0.004℃in the first year after eruption,which is within the amplitude of internal variability at the interannual time scale and thus not strong enough to have significant impacts on the global climate.展开更多
In this paper, the artificial neural network(ANN) model was used to evaluate the degree of intensive urban land use in Nanjing City, China. The construction and application of the ANN model took into account the compr...In this paper, the artificial neural network(ANN) model was used to evaluate the degree of intensive urban land use in Nanjing City, China. The construction and application of the ANN model took into account the comprehensive, spatial and complex nature of urban land use. Through a preliminary calculation of the degree of intensive land use of the sample area, representative sample area selection and using the back propagation neural network model to train, the intensive land use level of each evaluation unit is finally determined in the study area. Results show that the method can effectively correct the errors caused by the limitations of the model itself and the determination of the ideal value and weights when the multifactor comprehensive evaluation is used alone. The ANN model can make the evaluation results more objective and practical. The evaluation results show a tendency of decreasing land use intensity from the core urban area to the periphery and the industrial functional area has relatively low land use intensity compared with other functional areas. Based on the evaluation results, some suggestions are put forward, such as transforming the mode of urban spatial expansion, strengthening the integration and potential exploitation of the land in the urban built-up area, and strengthening the control of the construction intensity of protected areas.展开更多
The spatial characteristics of residents’ leisure activities not only reflect their demand for urban leisure space but also affect the urban spatial layout. This study takes Shenyang, China as an example and analyzes...The spatial characteristics of residents’ leisure activities not only reflect their demand for urban leisure space but also affect the urban spatial layout. This study takes Shenyang, China as an example and analyzes the characteristics of residents’ leisure activities through questionnaires. On this basis, it uses point of interest data and mobile phone signaling data to identify various types of residential and leisure functional relationships, and uses spatial analysis and community detection to assess the distance characteristics, flow patterns, and community structure of residents’ leisure activities, so as to discuss the spatial structure of residents’ leisure activities in Shenyang. The results showed that: (1) in addition to leisure at home, Shenyang residents mainly went to shopping malls, supermarkets,and parks for leisure activities, and the proportions of residents of the two types of leisure activities were approximately equal;(2) the average distances that residents traveled for shopping and park leisure were near in the middle and far in the periphery, and the travel costs of peripheral residents for centrally located leisure were higher than those for residents in central areas;(3) the flow patterns of the residential-shopping and residential-park functional relationships displayed clustering mode characteristics, and Shenyang presented a significant monocentric structure;and (4) residents’ shopping activities were concentrated in the southern community, and walking in the park activities were concentrated in the western community. Residents’ leisure activities were characterized by centripetal agglomeration,which was prone to problems such as traffic congestion and big city diseases. The spatial expansion process in the city was characterized by obvious directional inheritance and path dependence, and the construction of sub-cities is needed to improve the related service facilities.展开更多
Underlying terrain strongly influences dune formation.However,the impacts of underlying terrain on the dune formation are poorly studied.In the present research,we focused on dunes that formed in the alluvial fans and...Underlying terrain strongly influences dune formation.However,the impacts of underlying terrain on the dune formation are poorly studied.In the present research,we focused on dunes that formed in the alluvial fans and dry salt flats in the Qaidam Basin,Northwest China.We quantified the dunes'sediment characteristics on different types of underlying terrain and the terrain's effects on the surface quartz grains by analyzing grain-size distribution,soluble salt contents and grain surface micro-textures.Results showed that barchan dunes were dominated by medium sands with a unimodal frequency distribution,whose peak corresponded to the saltation load.Linear dunes were mainly composed of fine sands with a bimodal frequency distribution,whose main peak represented the saltation load,and whose secondary peak represented the modified saltation or suspension load.Sand was transported from source area by running water(inland rivers)over short distances and by wind over relatively longer distances.Thus,quartz grains had poor roundness and were dominated by sub-angular and angular shapes.Surface micro-textures indicated that dune sands were successively transported by exogenic agents(glaciation,fluviation and wind).Soluble salt contents were low in dunes that developed in the alluvial fans,which represented a low-energy chemical environment,so the grain surface micro-textures mainly resulted from mechanical erosion,with weak micro-textures formed by SiO2 solution and precipitation.However,soluble salt contents were much higher in dunes that developed in the dry salt flats,which indicated a high-energy chemical environment.Therefore,in addition to micro-structures caused by mechanical erosion,micro-textures formed by SiO2 solution and precipitation also well developed.Our results improve understanding of the sediment characteristics of dune sands and the effects of underlying terrain on dune development in the Qaidam Basin,China.展开更多
To further understand the status quo and change tendency of ecological security in county area, we took the example of Ningwu County, the headstream of Fenhe River, confronting serious eco-environment problem and cons...To further understand the status quo and change tendency of ecological security in county area, we took the example of Ningwu County, the headstream of Fenhe River, confronting serious eco-environment problem and considerable human impacts. Taking Ningwu as the study area and using variation coefficient method to determine the weights of the indices, we built ecological security pattern based on Pressure-State-Response (P-S-R) Model of Organization for Economic Cooperation and Development. The ecological security status was evaluated by calculating eco-security index (ESI) with socio-economic statistical data of Ningwu during 2001 -2010. The results showed that the situation of eco-security had been improved from heavy alarm to relative safety during 2001 -2010. It reflected that the ecological economic system in Ningwu County tended to be relaxed constantly after experienced a sharp conflict between ecological environment and economic growth. The ecological safety awareness was growing, however, by force of the objective requirements of population growth and economic development, the situation of ecological security was still unstable.展开更多
In this paper,we study the interactive relationship between the agglomeration of urban elements and the evolution of eco-environmental pressure.We build an index system for evaluating the agglomeration of urban elemen...In this paper,we study the interactive relationship between the agglomeration of urban elements and the evolution of eco-environmental pressure.We build an index system for evaluating the agglomeration of urban elements and eco-environmental pressure.Using the entropy method and response intensity model,we analyze how urban elements agglomeration influenced eco-environmental pressure in Changchun from 1990 to 2012,eliciting the changing features and influential factors.Ultimately,we conclude there is a significant interactive relationship between the agglomeration of urban elements and the evolution of eco-environmental pressure in Changchun.This is inferred from the degree of this agglomeration in Changchun having increased since 1990,with the degree of eco-environmental pressure first decreasing and then increasing.Alongside this,the impact of urban elements agglomeration on eco-environmental pressure has changed from negative to positive.The main reasons behind this shift are arguably the rapid growth of urban investment and ongoing urbanization.展开更多
Three global datasets, the History Database of the Global Environment (HYDE), Kaplan and Krurnhardt (KK) and Pongratz of reconstructed anthropogenic land cover change (ALCC) were introduced and compared in this ...Three global datasets, the History Database of the Global Environment (HYDE), Kaplan and Krurnhardt (KK) and Pongratz of reconstructed anthropogenic land cover change (ALCC) were introduced and compared in this paper. The HYDE dataset was recon- structed by Goldewijk and his colleagues at the National institute of Public ttealth and the Environment in Netherland, covering the past 12 000 years. The KK dataset was reconstructed by Kaplan and his colleagues, the Soil-Vegetation-Atmosphere Research Group at the Institute of Environmental Engineering in Switzerland, covering the past 8000 years. The Pongratz dataset was reconstructed by Pon- gratz and her colleagues at the Max Planck Institute for Meteorology in Germany, coveting AD 800-1992. The results show that the reconstructed datasets are quite different from each other due to the different methods used. The three datasets all allocated the historical ALCC according to human population density. The main reason causing the differences among the three datasets lies on the different relationships between population density and land use used in each reconstructed dataset. The KK dataset is better than the other two datasets for two important reasons. First, it used the nonlinear relationship between population density and land use, while the other two used the linear relationship. Second, Kaplan and his colleagues adopted the technological development and intensification parameters and considered the wood harvesting and the long-term fallow area resulted from shifting cultivation, which were neglected in the recon- structions of the other two datasets. Therefore, the KK dataset is more suitable as one of the anthropogenic forcing fields for climate simulation over the past two millennia that is recently concerned by two projects, the National Basic Research Program and the Strategic and Special Frontier Project of Science and Technology of the Chinese Academy of Sciences.展开更多
Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition w...Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition with four levels of N addition rate(N0, N30, N60, and N120) for6 years in an old-growth temperate forest in Xiaoxing’an Mountains in Northeastern China. We measured gross N transformation rates in the laboratory usingN tracing technology to explore the effects of N deposition on soil gross N transformations taking advantage of N deposition soils. No significant differences in gross soil N transformation rates were observed after 6 years of N deposition with various levels of N addition rate. For all N deposition soils, the gross NH~+ immobilization rates were consistently lower than the gross N mineralization rates,leading to net N mineralization. Nitrate(NO~-) was primarily produced via oxidation of NH~+(i.e., autotrophic nitrification), whereas oxidation of organic N(i.e., heterotrophic nitrification) was negligible. Differences between the quantity of ammonia-oxidizing bacteria and ammonia-oxidizing archaea were not significant for any treatment, which likely explains the lack of a significant effect on gross nitrification rates. Gross nitrification rates were much higher than the total NO~- consumption rates,resulting in a build-up of NO~-, which highlights the high risk of N losses via NO~- leaching or gaseous N emissions from soils. This response is opposite that of typical N-limited temperate forests suffering from N deposition,suggesting that the investigated old-growth temperate forest ecosystem is likely to approach N saturation.展开更多
Application of fertilizer has been found to significantly affect soil N cycling. However, a comprehensive understanding of the effects of long-term fertilization on soil gross N transformation rates is still lacking. ...Application of fertilizer has been found to significantly affect soil N cycling. However, a comprehensive understanding of the effects of long-term fertilization on soil gross N transformation rates is still lacking. We compiled data of observations from 10 long-term fertilization experiments and conducted a meta-analysis of the effects of long-term fertilization on soil gross N transformation rates. The results showed that if chemical fertilizers of N, P and K were applied in balance, soil p H decreased very slightly. There was a significantly positive effect of long-term fertilization, either chemical or organic fertilizers or their combinations, on gross N mineralization rate compared to the control treatment(the mean effect size ranged from 1.21 to 1.25 at 95% confidence intervals(CI) with a mean of 1.23), mainly due to the increasing soil total N content. The long-term application of organic fertilizer alone and combining organic and chemical fertilizer could increase the mineralization-immobilization turnover, thus enhance available N for plant while reduce N losses potential compared to the control treatment. However, long-term chemical fertilizer application did not significantly affect the gross NH4+ immobilization rate, but accelerated gross nitrification rate(1.19; 95% CI: 1.08 to 1.31). Thus, long-term chemical fertilizer alone would probably induce higher N losses potential through NO3– leaching and runoff than organic fertilizer application compared to the control treatment. Therefore, in the view of the effects of long-term fertilization on gross N transformation rates, it also supports that organic fertilizer alone or combination of organic and chemical fertilizer could not only improve crop yield, but also increase soil fertility and reduce the N losses potential.展开更多
The Hexi Inland River Basin in an arid region of northwestern China was chosen as the study area for this research. The authors define the vulnerability of an oasis social-ecological system to glacier change; select 1...The Hexi Inland River Basin in an arid region of northwestern China was chosen as the study area for this research. The authors define the vulnerability of an oasis social-ecological system to glacier change; select 16 indicators from natural and socioeconomic systems according to exposure, sensitivity, and adaptive capacity; and construct a vulnerability-assessment indicator system aimed at an inland river basin in the arid region of Northwestern China. Vulnerability of the oasis socialecological system affected by glacier change in the study area is evaluated by Spatial Principal Component Analysis(SPCA) under the circumstance of glacier change. The key factors affecting the vulnerability are analyzed. The vulnerability of the oasis social-ecological system in the Hexi Inland River Basin affected by glacier change is of more than medium grade, accounting for about 48.0% of the total number of counties in the study area. In terms of the spatial pattern of the vulnerability, the oasis economic belt is the most vulnerable. With the rapid development of the area's society and economy, the exposure of the system to glacial changes is significantly increased; and an increase in glacial meltwater is not enough to overcome the impact of increased exposure, which is the main reason for the high vulnerability. Based on the result of the vulnerability analysis and combined with the present industrial structure in the Hexi Inland River Basin, near-,medium-, and long-term adaptation initiatives are put forward in the article.展开更多
基金Under the auspices of the Humanities and Social Sciences Fund of the Ministry of Education of China (No.20YJC790107)Planning Project for Philosophy and Social Sciences of Shanxi Province (No.2021YJ040)Special Foundation for Science and Development of Shanxi Province (No.202204031401052)。
文摘It is of importance to enhance the urban areas'capacity for population aggregation in underdeveloped regions,aiming to rectify the imbalanced and insufficient pattern of economic development in China.Taking the Taiyuan Metropolitan Area(TMA)in central China as a case study,this paper examines the evolutionary process and characteristics of population agglomeration from 2000 to 2020,and identifies factors associated with agglomeration and their spatial effects.The findings indicated that:1)against the background of sustained population shrinkage in the provincial area,the TMA showed a demographic trend of steady increase,albeit with a decelerated growth rate.In the metropolitan area,urban population size continued to grow rapidly,whereas the rural areas endured sustained losses.Disparities in city size continued to widen,and the polarization of concentrated population in the core cities kept increasing.2)Agglomerations in both secondary and service industries had significant positive effects on local population agglomeration,with the former effect being stronger.Regional economic development,government fiscal expenditure,and financial advancement all contributed to facilitating local population clustering.From a spatial spillover perspective,service agglomeration and financial development promoted population agglomeration in surrounding areas.Conversely,fiscal expenditure inhibited such agglomeration.As for industrial agglomeration and regional economic development,their spatial spillover effects were non-significant.The results obtained reveal several policy implications aimed at enhancing the population agglomeration capacity of the metropolitan area in underdeveloped regions during the new era.
基金Project supported by the National Natural Science Foundation of China (No.30470329,40671036,30600092)"Xibuzhiguang"Project of the Chinese Academy of Sciences (CAS).
文摘Restoration and reconstruction of the degraded Tarim River ecosystem is an important challenge. A goal of an ecological water conveyance project is to protect and restore the natural vegetation in the lower reaches of Tadm River by transferring water from Bosten Lake, through the river channel, to the lower reaches. This study describes the changes in groundwater depth during the water transfer and the respondence of riparian vegetation to alterations in groundwater levels. The results indicate that groundwater depth along the Tarim River channel has a significant spatial-temporal component. Groundwater levels closest to the river channel show the most immediate and pronounced changes as a response to water transfer while those further away respond more slowly, although the observed change appears to be longer in duration. With a rise in the groundwater level, natural vegetation responded with higher growth rates, biomass and biodiversity. These favorable changes show that it is feasible to protect and restore the degraded natural vegetation by raising the groundwater depth. Plant communities are likely to reflect the hysteresis phenomenon, requiting higher water levels to initiate and stimulate desired growth than what may be needed to maintain the plant community. Because different species have different ecologies, including different root depths and densities and water needs, their response to increasing water availability will be spatially and temporally heterogenous. The response of vegetation is also influenced by microtopography and watering style. This paper discusses strategies for the protection and restoration of the degraded vegetation in the lower reaches of the Tarim River and provides information to complement ongoing theoretical research into ecological restoration in add or semi-arid ecosystems.
基金funded by the Special Project of the Ministry of Science and Technology of China(2014FY210100)the National Key Research and Development Program of China(2018YFD1100101)the National Natural Science Foundation of China(41971204)
文摘Land cover in the Chinese Loess Plateau has undergone dramatic changes since the late 1980s.Revealing the trend in land cover change and eco-environmental quality response of different geomorphic units in this stage is a realistic requirement for promoting sustainable development of the Chinese Loess Plateau.Based on the data of geomorphic units and land cover in 1990,2000,2010 and 2018 of the Chinese Loess Plateau,we studied the trend of land cover change and eco-environmental quality response of different geomorphic units by using a significance index of land cover change,a proportion index of land cover change and an eco-environmental response model.The results indicated that from 1990 to 2018,the areas of forestland and construction land substantially increased,whereas those of cropland,grassland,wetland and unused land considerably decreased.Land cover change exhibited large geomorphic differences,and the main conversion of land cover was from cropland into other land types.Unstable trend of land cover change in the loess tablelands and sandy loess hills declined,whereas the unstable trends in the other geomorphic units enhanced.Eco-environmental quality varied among different geomorphic units.The expansion of construction land and degradation of forestland,grassland and wetland resulted in the deterioration of eco-environmental quality.The conversion of cropland and unused land into forestland and grassland,and the conversion of grassland into forestland were the main factors that drove the improvement of eco-environmental quality.The findings of this study may provide theoretical reference and support decision making for the optimization of land use structure and the improvement of eco-environmental quality on the Chinese Loess Plateau.
基金Under the auspices of National Natural Science Foundation of China (No. 40671057)Knowledge Innovation Pro-grams of Chinese Academy of Sciences (No. KZCX3-SW-355)
文摘The nature heritages are the precious legacy of nature with outstanding scientific and aesthetic value. They are quite different from other common ecotourism areas, because of its original and unique system, sensitive and vulnerable landscape, and peripheral cultural features. Therefore, the tourism development in the nature heritage sites should be on the premise of ecological security. The evaluation index system of tourism ecological security in nature heritage sites was constructed in this article by AHP and Delphi methods, including nature ecological security, landscape visual security and local culture ecological security, and the security thresholds of indices were also established. In the indices' weights of the evaluation model, the nature ecological security ranked the highest, followed by tourist landscape visual security and culture ecological security, which reflected the influence degree of the limited factor to tourism ecological security. Then, this paper carried out an empirical study of Kanas of Xinjiang Uygur Autonomous Region, China, which has the potential to be the World Nature Heritage. On the basis of the data attained from survey and observation on the spot, as well as questionnaire answered by tourists and local communities, the ecological security status in Kanas was evaluated. The result showed that the status of Kanas tourism ecological security was better, but there had some limiting factors. Lastly, effective measures were put forward to ensure its ecological security.
基金supported by the China Geological Survey Project(DD20160060,121201140 42901)the National Natural Science Foundation of China(41502119,41371207)
文摘Sedimentary sequences in the Subei Basin are complex and have been affected by interactions between the ocean and rivers since the Late Pliocene, including the Yellow River, Huaihe River, and the Yangtze River. This sedimentary evolution, in particular the timing of Pleistocene transgressions, has long been a matter of controversy owing to the lack of precise chronological evidence. The aim of this study is to explore the evolution of the sedimentary environment throughout the past 3.00 Ma in this region on the basis of a comprehensive analysis of particle size and foraminifera and ostracods collected in the TZK9 core from the Subei Basin combined with geochronological studies of magnetostratigraphy, AMS^(14)C and optically stimulated luminescence(OSL). The results show that fluvial facies in the sedimentary environment from 3.00 to 1.01 Ma. There were fluvial facies and reflects six sea-level high stands from 1.01 to 0.25 Ma. The study area was affected by four large-scale transgressions since 0.25 Ma. The four marine sedimentary layers known as DU7(buried at 48–52 m), DU5(buried at 35–41 m), DU3(buried at 16–23 m), and DU1(buried at 2–4 m) are recorded in the MIS7(210–250 ka), MIS5, MIS3, and Holocene, respectively. The magnitude of the DU5 transgression was identical to that of the DU3 transgression, both were larger than the DU7 transgression, and the DU1 transgression was the weakest. The variation of transgression strength reflects the influence of global changes in sea level, tectonic subsidence, shell ridges, and sand dams. In the TZK9 core, we found evidence of seven sea-level high stands from the Early–Middle Pleistocene, and the first one caused by regional rapid subsidence and could be traced back to 0.83-0.84 Ma. The sea-level high stands and the age of the first one recorded above was different from other cores in eastern China, this was caused by the lack of absolute age control and the differences in paleotopography during this period. This study reconstructs sedimentary evolution, determines the transgression and its age, establishes the chronology since the Late Pliocene, and provides a scientific framework for further paleoenvironmental and tectonic studies. The results of this study highlight the important role that local tectonics and global sea level play in the sedimentary evolution and transgressions that have occurred in the western Subei Basin.
基金supported by the National Key Basic Research Program of China (2011CB403203)the Strategic Science and Technology Guide Project of Chinese Academy of Sciences (XDA05050401)
文摘In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected area, whereas the grazed area was continuously grazed at 8.5 dry sheep equivalent(DSE)/hm2. In the current research, soil and plant samples were taken from grazed and fenced areas to examine changes in vegetation and soil properties in 2005, 2006 and 2008. Results showed that vegetation characteristics and soil properties improved significantly in the fenced area compared with the grazed area. In the protected area the vegetation cover, height and above- and belowground biomass increased significantly. Soil pH, electrical conductivity and bulk density decreased significantly, but soil organic carbon and total nitrogen concentration increased greatly in the protected area. By comparing the vegetation and soil characteristics with pre-degraded grassland, we found that vegetation can recover 6 years after fencing, and soil pH can be restored 8 years after fencing. However, the restoration of soil organic carbon, total nitrogen and total phosphorus concentrations needed 16, 30 and 19 years, respectively. It is recommended that the stocking rate should be reduced to 1/3 of the current carrying capacity, or that a grazing regime of 1-year of grazing followed by a 2-year rest is adopted to sustain the current status of vegetation and soil resources. However, if N fertilizer is applied, the rest period could be shortened, depending on the rate of application.
基金Under the auspices of National Natural Science Foundation of China(No.41271165,41130747)Humanities and Social Science Research Planning Fund,Ministry of Education of China(No.12YJAGJW007)
文摘As a major aspect of the ′China Model′, urbanization in China is being heatedly discussed in the Anglophone literature in the last two decades. By considering China′s urbanization as a ′testing ground′ of ′western′ theories, these studies are important for the understanding of China′s ongoing urban restructuring and exchanging knowledge with ′western′ insights. Based on a survey of existing studies, this paper identifies various endogenous and exogenous concepts and explanations of China′s urbanization. It is suggested that China′s urbanization is mainly driven by a combination of political decentralization and neoliberalization with various forms of social stratification and mobility. However, it is argued that the distinctness of the ′China Model′, which is usually used to support the legitimacy of studies of China′s urbanization, has led to many controversial arguments and diminished the due contributions of Chinese scholars in the knowledge production of China′s urbanization. To consolidate the legitimacy of studies on China′s urbanization and enhance the roles of Chinese scholars, we suggest future studies to pay more attentions to the fundamental theories with looser constraints and ′true questions′ on China′s urbanization.
基金Under the auspices of Ministry of Education of Humanities and Social Sciences Project(No.09YJC840016)National Natural Science Foundation of China(No.41001088)National Basic Research Program of China(No.2014CB460614)
文摘During the reform era, Chinese cities witnessed dramatic institutional transformation and spatial restructuring in general and profound change of commuting patterns in particular. Using household surveys collected in Guangzhou, China, in 2001, 2005 and 2010, excess commuting measurements are estimated. Excess commuting shows an overall trend of increasing during 1990–1999, and then declining during 2000–2010. We argue that deepening marketization of the jobs and housing sectors has induced spatial separation of jobs and housing. In other words, institutional transition and urban spatial restructuring are underpinning the changes of commuting patterns in Chinese cities. Excess commuting has strong relationship with individual socio-demographic status, which is by and large due to the increasing flexibilities of jobs and housing location choices enjoyed by urban residents. The findings call for considerations on balancing jobs-housing in making public policies relevant to urban development in general, and land use and transportation in particular.
基金supported by the Chinese Academy of Sciences (KJZD-EW-G03-02)the National Natural Science Foundation of China (41705139)+1 种基金the Youth Science Fund of China (41401085)the project of the State Key Laboratory of Cryosphere Science (SKLCS-ZZ-2017)
文摘The availability of high-resolution satellite precipitation measurement products provides an opportunity to monitor precipitation over large and complex terrain and thus accurately evaluate the climatic,hydrological and ecological conditions in those regions.The Global Precipitation Measurement(GPM)mission is an important new program designed for global satellite precipitation estimation,but little information has been reported on the applicability of the GPM’s products for the Tibetan Plateau(TP).The object of this study is to evaluate the accuracy of the Integrated Multi-Satellite Retrievals for GPM(IMERG)Final Run product under different terrain and climate conditions over the TP by using 78 ground gauges from April 2014 to December 2017.The results showed the following:(1)the 3-year average daily precipitation estimation in the IMERG agrees well with the rain gauge observations(R^2=0.58,P<0.01),and IMERG also has a considerable ability to detect precipitation,as indicated by a high probability of detection(78%-98%)and critical success index(65%-85%);(2)IMERG performed better at altitudes from 3000 m to 4000 m with a small relative bias(RB)of 6.4%.Precipitation change was not significantly affected by local relief;(3)the climate system of the TP was divided into four climate groups with a total of 12 climate types based on the K?ppen climate classification system,and IMERG performed well in all climate types with the exception of the arid-desert-cold climate(Bwk)type.Furthermore,although IMERG showed the potential to detect snowfall,it still exhibits deficiencies in identifying light and moderate snow.These results indicate that IMERG could provide more accurate precipitation data if its retrieval algorithm was improved for complex terrain and arid regions.
基金Under the auspices of National Natural Science Foundation of China (No. 49761007)Open Foundation of National Laboratory of Western China’s Environmental Systems,Lanzhou University
文摘Study results in this paper have indicated that the Holocene climate in Xinjiang, Northwestem China has been alternating between wet and dry conditions, and was punctuated with a series of abrupt climate shifts. A sediment core taken from Barkol Lake in the northern Xinjiang of Northwest China was analyzed at 1 cm interval for grain-size distribution. Abrupt climate shifts revealed by the grain-size proxy occurred at ca 1.4, 3.0, 4.3, 5.6, 8.0 cal kyr B.E, which were well correlated to both the abrupt shifts recorded in the North Atlantic Ocean (NAO) and the Holocene sea surface temperature (SST) cooling events in the Arabian Ocean. The correlation indicated that the climatic changes in the extreme arid Northwest China were associated with the NAO, probably via the North Atlantic Oscillation-affected westerly winds. The strength and position of westerly winds probably modulated the Siberian-Mongolian high- pressure system (winter monsoon), and played an important role in climate change of Northwest China. Moreover, an evident drought interval during the middle Holocene was also revealed by grain-size proxy.
基金supported by the National Natural Science Foundation of China(Grant Nos.41988101,,42105047).
文摘An undersea volcano at Hunga Tonga-Hunga Ha'apai(HTHH)near the South Pacific island nation of Tonga,erupted violently on 15 January 2022.Potential climate impact of the HTHH volcanic eruption is of great concern to the public;here,we intend to size up the impact of the HTHH eruption from a historical perspective.The influence of historical volcanic eruptions on the global climate are firstly reviewed,which are thought to have contributed to decreased surface temperature,increased stratospheric temperature,suppressed global water cycle,weakened monsoon circulation and El Niño-like sea surface temperature.Our understanding of the impacts of past volcanic eruptions on global-scale climate provides potential implication to evaluate the impact of the HTHH eruption.Based on historical simulations,we estimate that the current HTHH eruption with an intensity of 0.4 Tg SO_(2)injection will decrease the global mean surface temperature by only 0.004℃in the first year after eruption,which is within the amplitude of internal variability at the interannual time scale and thus not strong enough to have significant impacts on the global climate.
基金Under the auspices of Special Financial Grant and General Financial Grant from the China Postdoctoral Science Foundation(No.2015T80127,2014M561040)National Natural Science Foundation of China(No.41371172,41401171,41471143)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(No.164320H101)
文摘In this paper, the artificial neural network(ANN) model was used to evaluate the degree of intensive urban land use in Nanjing City, China. The construction and application of the ANN model took into account the comprehensive, spatial and complex nature of urban land use. Through a preliminary calculation of the degree of intensive land use of the sample area, representative sample area selection and using the back propagation neural network model to train, the intensive land use level of each evaluation unit is finally determined in the study area. Results show that the method can effectively correct the errors caused by the limitations of the model itself and the determination of the ideal value and weights when the multifactor comprehensive evaluation is used alone. The ANN model can make the evaluation results more objective and practical. The evaluation results show a tendency of decreasing land use intensity from the core urban area to the periphery and the industrial functional area has relatively low land use intensity compared with other functional areas. Based on the evaluation results, some suggestions are put forward, such as transforming the mode of urban spatial expansion, strengthening the integration and potential exploitation of the land in the urban built-up area, and strengthening the control of the construction intensity of protected areas.
基金Under the auspices of National Natural Science Foundation of China(No.41871162)。
文摘The spatial characteristics of residents’ leisure activities not only reflect their demand for urban leisure space but also affect the urban spatial layout. This study takes Shenyang, China as an example and analyzes the characteristics of residents’ leisure activities through questionnaires. On this basis, it uses point of interest data and mobile phone signaling data to identify various types of residential and leisure functional relationships, and uses spatial analysis and community detection to assess the distance characteristics, flow patterns, and community structure of residents’ leisure activities, so as to discuss the spatial structure of residents’ leisure activities in Shenyang. The results showed that: (1) in addition to leisure at home, Shenyang residents mainly went to shopping malls, supermarkets,and parks for leisure activities, and the proportions of residents of the two types of leisure activities were approximately equal;(2) the average distances that residents traveled for shopping and park leisure were near in the middle and far in the periphery, and the travel costs of peripheral residents for centrally located leisure were higher than those for residents in central areas;(3) the flow patterns of the residential-shopping and residential-park functional relationships displayed clustering mode characteristics, and Shenyang presented a significant monocentric structure;and (4) residents’ shopping activities were concentrated in the southern community, and walking in the park activities were concentrated in the western community. Residents’ leisure activities were characterized by centripetal agglomeration,which was prone to problems such as traffic congestion and big city diseases. The spatial expansion process in the city was characterized by obvious directional inheritance and path dependence, and the construction of sub-cities is needed to improve the related service facilities.
基金The study was funded by the National Natural Science Foundation of China(41601005,41930641)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province(2019L0797).
文摘Underlying terrain strongly influences dune formation.However,the impacts of underlying terrain on the dune formation are poorly studied.In the present research,we focused on dunes that formed in the alluvial fans and dry salt flats in the Qaidam Basin,Northwest China.We quantified the dunes'sediment characteristics on different types of underlying terrain and the terrain's effects on the surface quartz grains by analyzing grain-size distribution,soluble salt contents and grain surface micro-textures.Results showed that barchan dunes were dominated by medium sands with a unimodal frequency distribution,whose peak corresponded to the saltation load.Linear dunes were mainly composed of fine sands with a bimodal frequency distribution,whose main peak represented the saltation load,and whose secondary peak represented the modified saltation or suspension load.Sand was transported from source area by running water(inland rivers)over short distances and by wind over relatively longer distances.Thus,quartz grains had poor roundness and were dominated by sub-angular and angular shapes.Surface micro-textures indicated that dune sands were successively transported by exogenic agents(glaciation,fluviation and wind).Soluble salt contents were low in dunes that developed in the alluvial fans,which represented a low-energy chemical environment,so the grain surface micro-textures mainly resulted from mechanical erosion,with weak micro-textures formed by SiO2 solution and precipitation.However,soluble salt contents were much higher in dunes that developed in the dry salt flats,which indicated a high-energy chemical environment.Therefore,in addition to micro-structures caused by mechanical erosion,micro-textures formed by SiO2 solution and precipitation also well developed.Our results improve understanding of the sediment characteristics of dune sands and the effects of underlying terrain on dune development in the Qaidam Basin,China.
基金Supported by National Natural Science Fund,China(41271143)Soft Science Research Project of Shanxi,China(2013041059-04)
文摘To further understand the status quo and change tendency of ecological security in county area, we took the example of Ningwu County, the headstream of Fenhe River, confronting serious eco-environment problem and considerable human impacts. Taking Ningwu as the study area and using variation coefficient method to determine the weights of the indices, we built ecological security pattern based on Pressure-State-Response (P-S-R) Model of Organization for Economic Cooperation and Development. The ecological security status was evaluated by calculating eco-security index (ESI) with socio-economic statistical data of Ningwu during 2001 -2010. The results showed that the situation of eco-security had been improved from heavy alarm to relative safety during 2001 -2010. It reflected that the ecological economic system in Ningwu County tended to be relaxed constantly after experienced a sharp conflict between ecological environment and economic growth. The ecological safety awareness was growing, however, by force of the objective requirements of population growth and economic development, the situation of ecological security was still unstable.
基金Under the auspices of Education Ministry for Development of Liberal Arts and Social Science(No.14YJA790035)
文摘In this paper,we study the interactive relationship between the agglomeration of urban elements and the evolution of eco-environmental pressure.We build an index system for evaluating the agglomeration of urban elements and eco-environmental pressure.Using the entropy method and response intensity model,we analyze how urban elements agglomeration influenced eco-environmental pressure in Changchun from 1990 to 2012,eliciting the changing features and influential factors.Ultimately,we conclude there is a significant interactive relationship between the agglomeration of urban elements and the evolution of eco-environmental pressure in Changchun.This is inferred from the degree of this agglomeration in Changchun having increased since 1990,with the degree of eco-environmental pressure first decreasing and then increasing.Alongside this,the impact of urban elements agglomeration on eco-environmental pressure has changed from negative to positive.The main reasons behind this shift are arguably the rapid growth of urban investment and ongoing urbanization.
基金Under the auspices of Strategic and Special Frontier Project of Science and Technology of Chinese Academy of Sciences (No. XDA05080800)National Basic Research Program of China (No. 2010CB950102)National Natural Science Foundation of China (No. 40871007)
文摘Three global datasets, the History Database of the Global Environment (HYDE), Kaplan and Krurnhardt (KK) and Pongratz of reconstructed anthropogenic land cover change (ALCC) were introduced and compared in this paper. The HYDE dataset was recon- structed by Goldewijk and his colleagues at the National institute of Public ttealth and the Environment in Netherland, covering the past 12 000 years. The KK dataset was reconstructed by Kaplan and his colleagues, the Soil-Vegetation-Atmosphere Research Group at the Institute of Environmental Engineering in Switzerland, covering the past 8000 years. The Pongratz dataset was reconstructed by Pon- gratz and her colleagues at the Max Planck Institute for Meteorology in Germany, coveting AD 800-1992. The results show that the reconstructed datasets are quite different from each other due to the different methods used. The three datasets all allocated the historical ALCC according to human population density. The main reason causing the differences among the three datasets lies on the different relationships between population density and land use used in each reconstructed dataset. The KK dataset is better than the other two datasets for two important reasons. First, it used the nonlinear relationship between population density and land use, while the other two used the linear relationship. Second, Kaplan and his colleagues adopted the technological development and intensification parameters and considered the wood harvesting and the long-term fallow area resulted from shifting cultivation, which were neglected in the recon- structions of the other two datasets. Therefore, the KK dataset is more suitable as one of the anthropogenic forcing fields for climate simulation over the past two millennia that is recently concerned by two projects, the National Basic Research Program and the Strategic and Special Frontier Project of Science and Technology of the Chinese Academy of Sciences.
基金supported by Grants from the ‘‘973’’ Project(2014CB953803)the Fundamental Research Funds for the Central Universities(2572017EA02)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD,164320H116)
文摘Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition with four levels of N addition rate(N0, N30, N60, and N120) for6 years in an old-growth temperate forest in Xiaoxing’an Mountains in Northeastern China. We measured gross N transformation rates in the laboratory usingN tracing technology to explore the effects of N deposition on soil gross N transformations taking advantage of N deposition soils. No significant differences in gross soil N transformation rates were observed after 6 years of N deposition with various levels of N addition rate. For all N deposition soils, the gross NH~+ immobilization rates were consistently lower than the gross N mineralization rates,leading to net N mineralization. Nitrate(NO~-) was primarily produced via oxidation of NH~+(i.e., autotrophic nitrification), whereas oxidation of organic N(i.e., heterotrophic nitrification) was negligible. Differences between the quantity of ammonia-oxidizing bacteria and ammonia-oxidizing archaea were not significant for any treatment, which likely explains the lack of a significant effect on gross nitrification rates. Gross nitrification rates were much higher than the total NO~- consumption rates,resulting in a build-up of NO~-, which highlights the high risk of N losses via NO~- leaching or gaseous N emissions from soils. This response is opposite that of typical N-limited temperate forests suffering from N deposition,suggesting that the investigated old-growth temperate forest ecosystem is likely to approach N saturation.
基金supported by the National Natural Science Foundation of China (41330744)the “973” Program of China (2014CB953803)the Priority Academic Program Development of Jiangsu Higher Education Institutions, China (164320H116)
文摘Application of fertilizer has been found to significantly affect soil N cycling. However, a comprehensive understanding of the effects of long-term fertilization on soil gross N transformation rates is still lacking. We compiled data of observations from 10 long-term fertilization experiments and conducted a meta-analysis of the effects of long-term fertilization on soil gross N transformation rates. The results showed that if chemical fertilizers of N, P and K were applied in balance, soil p H decreased very slightly. There was a significantly positive effect of long-term fertilization, either chemical or organic fertilizers or their combinations, on gross N mineralization rate compared to the control treatment(the mean effect size ranged from 1.21 to 1.25 at 95% confidence intervals(CI) with a mean of 1.23), mainly due to the increasing soil total N content. The long-term application of organic fertilizer alone and combining organic and chemical fertilizer could increase the mineralization-immobilization turnover, thus enhance available N for plant while reduce N losses potential compared to the control treatment. However, long-term chemical fertilizer application did not significantly affect the gross NH4+ immobilization rate, but accelerated gross nitrification rate(1.19; 95% CI: 1.08 to 1.31). Thus, long-term chemical fertilizer alone would probably induce higher N losses potential through NO3– leaching and runoff than organic fertilizer application compared to the control treatment. Therefore, in the view of the effects of long-term fertilization on gross N transformation rates, it also supports that organic fertilizer alone or combination of organic and chemical fertilizer could not only improve crop yield, but also increase soil fertility and reduce the N losses potential.
基金supported by the Global Change Research Program of China (2013CBA01808)the China National Natural Science Foundation (41271088)
文摘The Hexi Inland River Basin in an arid region of northwestern China was chosen as the study area for this research. The authors define the vulnerability of an oasis social-ecological system to glacier change; select 16 indicators from natural and socioeconomic systems according to exposure, sensitivity, and adaptive capacity; and construct a vulnerability-assessment indicator system aimed at an inland river basin in the arid region of Northwestern China. Vulnerability of the oasis socialecological system affected by glacier change in the study area is evaluated by Spatial Principal Component Analysis(SPCA) under the circumstance of glacier change. The key factors affecting the vulnerability are analyzed. The vulnerability of the oasis social-ecological system in the Hexi Inland River Basin affected by glacier change is of more than medium grade, accounting for about 48.0% of the total number of counties in the study area. In terms of the spatial pattern of the vulnerability, the oasis economic belt is the most vulnerable. With the rapid development of the area's society and economy, the exposure of the system to glacial changes is significantly increased; and an increase in glacial meltwater is not enough to overcome the impact of increased exposure, which is the main reason for the high vulnerability. Based on the result of the vulnerability analysis and combined with the present industrial structure in the Hexi Inland River Basin, near-,medium-, and long-term adaptation initiatives are put forward in the article.