The long-term spatiotemporal changes of surface biogenic elements in the Changjiang River Estuary and adjacent waters during the summer of 2008–2016 were analyzed in this study.The concentrations of dissolved inorgan...The long-term spatiotemporal changes of surface biogenic elements in the Changjiang River Estuary and adjacent waters during the summer of 2008–2016 were analyzed in this study.The concentrations of dissolved inorganic nitrogen(DIN),soluble reactive phosphate(PO_(4)^(3−))and silicate(SiO_(3)^(2−))were generally stable,with a slight decrease of DIN and PO_(4)^(3−),and a slight increase of SiO_(3)^(2−),which mainly occurred in the estuarine waters.The grey correlation analysis was carried out between biogenic elements and chlorophyll a(Chl-a).Results showed that compared with the absolute values of biogenic elements,the correlations between the concentration ratio of nitrogen to phosphorus(N/P),ratio of silicon to nitrogen(Si/N)and Chl-a were closer,indicating the important influence on phytoplankton by the structure of biogenic elements.The study area was generally in a state of potential P limitation,and could have potential impact on the phytoplankton community,triggering the shift of red tide dominant species from diatoms to dinoflagellates.展开更多
Social vulnerability,as one of the risk components,partially explains the magnitude of the impacts observed after a disaster.In this study,a spatiotemporally comparable assessment of social vulnerability and its drive...Social vulnerability,as one of the risk components,partially explains the magnitude of the impacts observed after a disaster.In this study,a spatiotemporally comparable assessment of social vulnerability and its drivers was conducted in Portugal,at the civil parish level,for three census frames.The first challenging step consisted of the selection of meaningful and consistent variables over time.Data were normalized using the Adjusted Mazziotta-Pareto Index(AMPI)to obtain comparable adimensional-normalized values.A joint principal component analysis(PCA)was applied,resulting in a robust set of variables,interpretable from the point of view of their self-grouping around vulnerability drivers.A separate PCA for each census was also conducted,which proved to be useful in analyzing changes in the composition and type of drivers,although only the joint PCA allows the monitoring of spatiotemporal changes in social vulnerability scores and drivers from 1991 to 2011.A general improvement in social vulnerability was observed for Portugal.The two main drivers are the economic condition(PC1),and aging and depopulation(PC2).The remaining drivers highlighted are uprooting and internal mobility,and daily commuting.Census data proved their value in the territorial,social,and demographic characterization of the country,to support medium-and long-term disaster risk reduction measures.展开更多
Since the Grain for Green(GFG)program was implemented in 1999,most steeply sloping farmlands in the Loess Plateau of China have been returned to forestland and grassland.To understand its impact on the food production...Since the Grain for Green(GFG)program was implemented in 1999,most steeply sloping farmlands in the Loess Plateau of China have been returned to forestland and grassland.To understand its impact on the food production,this study analyzed the spatiotemporal changes of food crop production(FCP)in the plateau and quantified the contribution of sown area and yield changes to the total FCP during 1998–2014 using factor decomposition models,and then discussed the impact of GFG program on the FCP based on literature data.With the implementation of GFG program,total sown area in the Loess Plateau quickly deceased by 17.3%from 1998 to 2003,and then gradually restored to 1.03×107 hm2 in 2010.Thereafter,it slightly decreased to 1.02×107 hm2(94.6%of the area in 1998)in 2014.By contrast,total FCP generally showed an apparent growth trend,averagely increased by 1.71%per year in the whole plateau during 1998–2014.This increase was jointly contributed by the improved yield of individual crops,and the adjustment of cropping structure,i.e.,the expansion of high yield maize crop.The factor decomposition analysis results indicate that the sown area shrinkage only reduced the growth rate of total FCP by 0.29%per year during 1998–2014,although a significant impact was found for the early stage of 1999–2003.The results suggest that the implementation of GFG program would not induce an obvious risk of the food security.Therefore,it is suggested that the GFG program should be set as a long-term strategic policy,by not only supporting the conversion of slope farmlands,but also helping local farmers to seek sustainable ways of land use to improve the income and livelihood.It can be combined with the poverty eradication program,to simultaneously achieve the national goals of ecological civilization building and the livelihood improvement of rural people in the Loess Plateau.Considering rainfall limitation,the conversion of slope farmlands should be prioritized to grasslands.展开更多
The dynamics of soil organic carbon(SOC)in cropland is one of the central issues related to both soil fertility and environmental safety. However, little information is available at county level regarding the spatiote...The dynamics of soil organic carbon(SOC)in cropland is one of the central issues related to both soil fertility and environmental safety. However, little information is available at county level regarding the spatiotemporal variability of SOC in the southwestern mountainous region of China. Thus, this study aimed to explore spatiotemporal changes of SOC in the cultivated soil layer of dry land in Mojiang County,Yunnan Province, China. Data were obtained from the second national soil survey(SNSS) of 1985 and soil tests for fertilizer application carried out by the Mojiang Agricultural Bureau in 2006. The ANOVA test was applied to determine any significant differences between the datasets, while semivariogram analysis was performed on geostatistics via an ordinary Kriging method in order to map spatial patterns of soil organic carbon density(SOCD). The results revealed that SOCD in the cultivated soil layer significantly decreased from 3.93 kg m^(-2) in 1985 to 2.89 kg m^(-2) in 2006, with a total soil organic carbon stock(SOCS) decrease of 41.54×10~4 t over the same period. SOCS levels fell most markedly in yellow-brown soil at a rate of51.52%, while an increase of 8.70% was found in the analysed latosol. Geostatistical analysis also showed that the recorded changes in SOCD between 1985 and2006 were spatially structured. The decreasing trend might be attributed to the combined action of intense cultivation, major crop residue removal without any protective tillage measures, unreasonable fertilization and natural climatic diversity inducing a large decrease in SOC in the studied cultivated dry land region of Mojiang County. Therefore, management measures such as protective tillage should be undertaken in order to enhance soil C sequestration.展开更多
Agriculture needs to produce more food to feed the growing population in the 21st century.It makes the reference crop water requirement(WREQ)a major challenge especially in regions with limited water and high water de...Agriculture needs to produce more food to feed the growing population in the 21st century.It makes the reference crop water requirement(WREQ)a major challenge especially in regions with limited water and high water demand.Iran,with large climatic variability,is experiencing a serious water crisis due to limited water resources and inefficient agriculture.In order to overcome the issue of uneven distribution of weather stations,gridded Climatic Research Unit(CRU)data was applied to analyze the changes in potential evapotranspiration(PET),effective precipitation(EFFPRE)and WREQ.Validation of data using in situ observation showed an acceptable performance of CRU in Iran.Changes in PET,EFFPRE and WREQ were analyzed in two 30-a periods 1957-1986 and 1987-2016.Comparing two periods showed an increase in PET and WREQ in regions extended from the southwest to northeast and a decrease in the southeast,more significant in summer and spring.However,EFFPRE decreased in the southeast,northeast,and northwest,especially in winter and spring.Analysis of annual trends revealed an upward trend in PET(14.32 mm/decade)and WREQ(25.50 mm/decade),but a downward trend in EFFPRE(-11.8 mm/decade)over the second period.Changes in PET,EFFPRE and WREQ in winter have the impact on the annual trend.Among climate variables,WREQ showed a significant correlation(r=0.59)with minimum temperature.The increase in WREQ and decrease in EFFPRE would exacerbate the agricultural water crisis in Iran.With all changes in PET and WREQ,immediate actions are needed to address the challenges in agriculture and adapt to the changing climate.展开更多
The ecological quality of inland areas is an important aspect of the United Nations Sustainable Development Goals(UN SDGs).The ecological environment of Northwest China is vulnerable to changes in climate and land use...The ecological quality of inland areas is an important aspect of the United Nations Sustainable Development Goals(UN SDGs).The ecological environment of Northwest China is vulnerable to changes in climate and land use/land cover,and the changes in ecological quality in this arid region over the last two decades are not well understood.This makes it more difficult to advance the UN SDGs and develop appropriate measures at the regional level.In this study,we used the Moderate Resolution Imaging Spectroradiometer(MODIS)products to generate remote sensing ecological index(RSEI)on the Google Earth Engine(GEE)platform to examine the relationship between ecological quality and environment in Xinjiang during the last two decades(from 2000 to 2020).We analyzed a 21-year time series of the trends and spatial characteristics of ecological quality.We further assessed the importance of different environmental factors affecting ecological quality through the random forest algorithm using data from statistical yearbooks and land use products.Our results show that the RSEI constructed using the GEE platform can accurately reflect the ecological quality information in Xinjiang because the contribution of the first principal component was higher than 90.00%.The ecological quality in Xinjiang has increased significantly over the last two decades,with the northern part of this region having a better ecological quality than the southern part.The areas with slightly improved ecological quality accounted for 31.26%of the total land area of Xinjiang,whereas only 3.55%of the land area was classified as having a slightly worsen(3.16%)or worsen(0.39%)ecological quality.The vast majority of the deterioration in ecological quality mainly occurred in the barren areas Temperature,precipitation,closed shrublands,grasslands and savannas were the top five environmental factors affecting the changes in RSEI.Environmental factors were allocated different weights for different RSEI categories.In general,the recovery of ecological quality in Xinjiang has been controlled by climate and land use/land cover during the last two decades and policy-driven ecological restoration is therefore crucial.Rapid monitoring of inland ecological quality using the GEE platform is projected to aid in the advancement of the comprehensive assessment of the UN SDGs.展开更多
Understanding the trade-offs among ecosystem services(ESs)at multiple scales is a key challenge to effective environmental management.However,the scale effect of ESs trade-offs in the Qinghai-Tibetan Plateau(QTP)has r...Understanding the trade-offs among ecosystem services(ESs)at multiple scales is a key challenge to effective environmental management.However,the scale effect of ESs trade-offs in the Qinghai-Tibetan Plateau(QTP)has received little attention.This study investigated the scale effects of ESs trade-offs in Bailongjiang Watershed(BLJW),a typical transitional ecotone from the Loess Plateau to the Tibetan Plateau with multiple ESs,intensive human activities and frequent geological disasters in the Eastern Margin of the QTP,China.Four key ESs including food supply(FS),soil conservation(SC),water conservation(WC),and habitat quality(HQ)in BLJW in 1990,2002,and 2016 were mapped to analyze the scale effects at the watershed,county,and township scales.The results indicated varying scale-related temporal and spatial relationships among FS,SC,WC,and HQ.The trade-offs between FS-SC and FS-WC initially increased and then decreased during 1990-2002 and 2002-2016,respectively,while the trade-offs between SC-WC,SC-HQ,HQ-WC,and HQ-FS first decreased and then increased at the same period.The magnitudes of the trade-offs among the four ESs are in the order of watershed scale>township scale>county scale.Among the major land-use types in BLJW,the trade-offs between WC-FS and between HQ-FS in farmland and grassland were higher than those of other land uses.There is a strong trade-off between SC-HQ in forestland and a weak trade-off between SC-WC in farmland and grassland.The trade-offs between the six ESs pairs varied and were scale-dependent mainly due to spatial heterogeneity in the landscape and in human activities.Understanding the ESs trade-offs at the watershed,county,and township scales provides a scientific basis for the formulation of environmental management strategies at appropriate spatial scales.At the BLJW watershed scale,more attention should be paid on farmland and grassland planning and its management,also,forestland should be enlarged if possible.At the county and township scales,land consolidation and planning should be paid more attention to develop ecological agricultural tourism and multi-functional landscapes for strategic spatial planning and integrated watershed management.展开更多
Crop planting patterns are an important component of agricultural land systems.These patterns have been significantly changed due to the combined impacts of climatic changes and socioeconomic developments.However,the ...Crop planting patterns are an important component of agricultural land systems.These patterns have been significantly changed due to the combined impacts of climatic changes and socioeconomic developments.However,the extent of these changes and their possible impacts on the environment,terrestrial landscapes and rural livelihoods are largely unknown due to the lack of spatially explicit datasets including crop planting patterns.To fill this gap,this study proposes a new method for spatializing statistical data to generate multitemporal crop planting pattern datasets.This method features a two-level model that combines a land-use simulation and a crop pattern simulation.The output of the first level is the spatial distribution of the cropland,which is then used as the input for the second level,which allocates crop censuses to individual gridded cells according to certain rules.The method was tested using data from 2000 to 2019 from Heilongjiang Province,China,and was validated using remote sensing images.The results show that this method has high accuracy for crop area spatialization.Spatial crop pattern datasets over a given time period can be important supplementary information for remote sensing and thus support a wide range of application in agricultural land systems.展开更多
The Qinghai-Tibet Plateau(QTP),also known as the Third Pole of the Earth,is a vital ecological security barrier for China.It is a tremendously sensitive region affected by the impacts of global climate change.The esca...The Qinghai-Tibet Plateau(QTP),also known as the Third Pole of the Earth,is a vital ecological security barrier for China.It is a tremendously sensitive region affected by the impacts of global climate change.The escalating intensity of climate change has presented profound challenges to its ecosystem functions and stability.This study first analyzes the spatiotemporal variations of the QTP ecosystem patterns and the key functions of the Plateau including water conservation,soil conservation,and windbreak and sand fixation from 2000 to 2020.It clarifies the regional differences in ecosystem functions and their importance,further evaluates the stability of ecosystem functions,and lays a scientific foundation for an ecological civilization on the Plateau by implementing conservation and restoration projects.The main results show that:(1)From 2000 to 2020,the wetland area in the QTP increased,while the grassland area significantly decreased.There were improvements in water conservation and windbreak and sand fixation capacities,with annual rates of change being 3.57m~3·ha^(-1)·a^(-1)and 0.23 t·ha^(-1)·a^(-1),respectively.However,the overall soil conservation trend declined during the same period,with an annual change rate of-0.16 t·ha^(-1)·a^(-1).(2)The core areas of water conservation,soil conservation,and windbreak and sand fixation on the QTP accounted for 12.7%,13.9%,and 14.2%of the total area,respectively.The core water conservation areas are mainly the southeastern QTP,Sanjiangyuan,and Naqu,while the core windbreak and sand fixation areas were concentrated in the central and western parts of the Plateau.The core soil conservation areas surrounded the entire interior of the Plateau.(3)From 2000 to 2020,the water conservation,soil conservation,and windbreak sand-fixation function on the QTP had higher stability in the southeastern and central parts,while stability was lower in the western region.Considering the stability assessment and ecological protection and restoration practices,the QTP can be divided into three major categories and 16 ecological functional zones.Differentiated ecological protection and restoration efforts can be implemented based on the different core ecosystem functions and zoning.展开更多
How vegetation phenology responds to climate change is a key to the understanding of the mechanisms driving historic and future changes in regional terrestrial ecosystem productivity. Based on the 250-m and 8-day mode...How vegetation phenology responds to climate change is a key to the understanding of the mechanisms driving historic and future changes in regional terrestrial ecosystem productivity. Based on the 250-m and 8-day moderate resolution imaging spectroradiometer(MODIS) normalized difference vegetation index(NDVI) data for 2000-2014 in the Three-River Source Region(TRSR) of Qinghai Province, China, i.e., the hinterland of the Tibetan Plateau, we extracted relevant vegetation phenological information(e.g., start, end, and length of growing season) and analyzed the changes in the TRSR vegetation in response to climate change. The results reveal that, under the increasingly warm and humid climate, the start of vegetation growing season(SOS) advanced 1.03 day yr-1 while the end of vegetation growing season(EOS) exhibited no significant changes, which led to extended growing season length. It is found that the SOS was greatly affected by the preceding winter precipitation, with progressively enhanced precipitation facilitating an earlier SOS. Moreover, as the variations of SOS and its trend depended strongly on topography, we estimated the elevation break-points for SOS. The lower the elevations were, the earlier the SOS started. In the areas below 3095-m elevation, the SOS delay changed rapidly with increasing elevation;whereas above that, the SOS changes were relatively minor. The SOS trend had three elevation break-points at 2660, 3880, and 5240 m.展开更多
Accurate and rapid evaluation of the regional eco-environment is critical to policy formulation.The remote sensing ecological index(RSEI)model of the Guangxi Beibu Gulf Economic Zone(GBGEZ)during 2001-2020 was establi...Accurate and rapid evaluation of the regional eco-environment is critical to policy formulation.The remote sensing ecological index(RSEI)model of the Guangxi Beibu Gulf Economic Zone(GBGEZ)during 2001-2020 was established and evaluated using four indices:dryness,wetness,greenness,and heat.This paper proposes an information granulation method for remote sensing based on the RSEI index value that uses granular computing.We found that:(1)From 2001 to 2020,the eco-environmental quality(EEQ)of GBGEZ tended to improve,and the spatial difference tended to expand.The regional spatial distribution of the eco-environment is primarily in the second-level and third-level areas,and the EEQ in the east and west is better than that in the middle.The contribution of greenness,wetness,and dryness to the improvement of EEQ in the study region increased year by year.(2)From 2001to 2020,the order of the contribution of the EEQ index in the GBGEZ was dryness,wetness,greenness,and heat.(3)The social and economic activities in the study region had a certain inhibitory effect on the improvement of the EEQ.展开更多
Sensitivity assessment is useful for monitoring land desertification. Research into how to prevent and control desertification is also important. In the arid region of northwest China, desertification is becoming wors...Sensitivity assessment is useful for monitoring land desertification. Research into how to prevent and control desertification is also important. In the arid region of northwest China, desertification is becoming worse and is a serious problem that affects local sustainable development. Based on remote-sensing and geographic information system technology, this study establishes a 'soil-terrain-hydrology-climate-vegetation' desertification sensitivity comprehensive evaluation system to reflect the spatiotemporal changes of land desertification, and proposes a spatial distance model to calculate a desertification sensitivity index. The spatiotemporal change characteristics of land desertification sensitivity in northwest China are quantitatively assessed from 2000 to 2017. Moreover, the main driving factors are analyzed using the geographical detector method. The results show the following.(1) Terrain, soil, climate, vegetation and hydrology affect and restrict each other, and constitute the background conditions of the distributions and changes of sensitivity to desertification in northwest China.(2) Desertification sensitivity generally displays a low distribution characteristic on the periphery of the area and a high one in the interior. The low-sensitivity regions are mainly in the five major mountain ranges(Altai Mountains, Tianshan Mountains, Kunlun Mountains, Altun Mountains and Qilian Mountains), while the high-sensitivity regions are mainly in regions such as the Junggar Basin, the Tarim Basin and the Inner Mongolia Plateau, as well as the Taklimakan Desert, Badain Jaran Desert and Tengger Desert. The spatial distribution of desertification sensitivity is obviously regional, and the high-and low-sensitivity regions have clear boundaries and a concentrated distribution.(3) With regard to spatiotemporal evolution, changes in desertification sensitivity since 2000 have been predominantly stable, and the overall sensitivity has displayed a slowly decreasing trend, indicating that potential desertification regions are decreasing annually and that some achievements have been made in the control of regional desertification.(4) Soil and climate play a direct role in the driving factors of desertification in northwest China, and these have been found to be the most important influential factors. Vegetation is the most active and basic factor in changing the sensitivity. In addition, topography and hydrology play a role in restricting desertification changes. Socio-economic factors are the most rapid factors affecting regional desertification sensitivity, and their impacts tend to be gradually increasing. In general, desertification has been effectively controlled in northwest China, and positive results have been achieved in such control. However, against the backdrop of intensified global climate change, increasingly prominent human activities and new normals of socio-economic development, the monitoring, assessment and control of desertification in China still have a long way to go.展开更多
Glaciers are a reliable freshwater resource in arid regions of West China and the vulnerability of its changes is closely related to regional ecosystem services and economic sustainable development. Here, we took the ...Glaciers are a reliable freshwater resource in arid regions of West China and the vulnerability of its changes is closely related to regional ecosystem services and economic sustainable development. Here, we took the Qilian Mountains as an example and analyzed the spatiotemporal characteristics of glacier changes from 1998 to 2018, based on remote sensing images and the Second Chinese Glacier Inventory. We estimated the basic organizational framework and evaluation index system of glacier change vulnerability from exposure, sensitivity and adaptability, which covered the factors of physical geography, population status and socio-economic level. We analyzed the spatial and temporal evolutions of glacier change vulnerability by using the vulnerability evaluation model. Our results suggested that:(1) Glacier area and volume decreased by 71.12±98.98 km^(2) and 5.59±4.41 km^(3), respectively, over the recent two decades, which mainly occurred at the altitude below 4800 m, with an area shrinking rate of 2.5%. In addition, glaciers in the northern aspect(northwest, north and northeast) had the largest area reduction. Different counties exhibited remarkable discrepancies in glacier area reduction, Tianjuan and Minle presented the maximum and minimum decrease, respectively.(2) Glacier change vulnerability level showed a decreasing trend in space from the central to the northwestern and southeastern regions with remarkable differences. Vulnerability level had increased significantly over time and was mainly concentrated in moderate, high and extreme levels with typical characteristics of phases and regional complexity. Our study can not only help to understand and master the impacts of recent glacier changes on natural and social aspects but also be conducive to evaluate the influences of glacier retreat on socio-economic developments in the future, thus providing references for formulating relevant countermeasures to achieve regional sustainable development.展开更多
基金The National Research Program of China under contract No.2017YFC1405300.
文摘The long-term spatiotemporal changes of surface biogenic elements in the Changjiang River Estuary and adjacent waters during the summer of 2008–2016 were analyzed in this study.The concentrations of dissolved inorganic nitrogen(DIN),soluble reactive phosphate(PO_(4)^(3−))and silicate(SiO_(3)^(2−))were generally stable,with a slight decrease of DIN and PO_(4)^(3−),and a slight increase of SiO_(3)^(2−),which mainly occurred in the estuarine waters.The grey correlation analysis was carried out between biogenic elements and chlorophyll a(Chl-a).Results showed that compared with the absolute values of biogenic elements,the correlations between the concentration ratio of nitrogen to phosphorus(N/P),ratio of silicon to nitrogen(Si/N)and Chl-a were closer,indicating the important influence on phytoplankton by the structure of biogenic elements.The study area was generally in a state of potential P limitation,and could have potential impact on the phytoplankton community,triggering the shift of red tide dominant species from diatoms to dinoflagellates.
基金funded by FCT (Funda??o para a Ciência e Tecnologia/Portuguese Foundation for Science and Technology),through the projects “Be Safe Slide-Landslide early warning soft technology prototype to improve community resilience and adaptation to environmental change”(PTDC/GES-AMB/30052/2017)“MIT-RSC-Multi-risk interactions towards resilient and sustainable cities”(MIT-EXPL/CS/0018/2019)+3 种基金Jorge Rocha was financed through FCT,within the framework of the project “TRIAD-Health risk and social vulnerability to arboviral diseases in mainland Portugal”(PTDC/GES-OUT/30210/2017)partially developed within the framework of the RISKCOAST project (Ref:SOE3/P4/E0868) funded by the Interreg SUDOE Program (3rd Call for proposals)Pedro Pinto Santos was fi nanced by FCT,within the framework of the contract CEEIND/00268/2017by the Research Unit UID/GEO/00295/2020
文摘Social vulnerability,as one of the risk components,partially explains the magnitude of the impacts observed after a disaster.In this study,a spatiotemporally comparable assessment of social vulnerability and its drivers was conducted in Portugal,at the civil parish level,for three census frames.The first challenging step consisted of the selection of meaningful and consistent variables over time.Data were normalized using the Adjusted Mazziotta-Pareto Index(AMPI)to obtain comparable adimensional-normalized values.A joint principal component analysis(PCA)was applied,resulting in a robust set of variables,interpretable from the point of view of their self-grouping around vulnerability drivers.A separate PCA for each census was also conducted,which proved to be useful in analyzing changes in the composition and type of drivers,although only the joint PCA allows the monitoring of spatiotemporal changes in social vulnerability scores and drivers from 1991 to 2011.A general improvement in social vulnerability was observed for Portugal.The two main drivers are the economic condition(PC1),and aging and depopulation(PC2).The remaining drivers highlighted are uprooting and internal mobility,and daily commuting.Census data proved their value in the territorial,social,and demographic characterization of the country,to support medium-and long-term disaster risk reduction measures.
基金jointly supported by the National Natural Science Foundation of China(41671093)the National Key R&D Program of China(2017YFA0604701,2012CB955304)
文摘Since the Grain for Green(GFG)program was implemented in 1999,most steeply sloping farmlands in the Loess Plateau of China have been returned to forestland and grassland.To understand its impact on the food production,this study analyzed the spatiotemporal changes of food crop production(FCP)in the plateau and quantified the contribution of sown area and yield changes to the total FCP during 1998–2014 using factor decomposition models,and then discussed the impact of GFG program on the FCP based on literature data.With the implementation of GFG program,total sown area in the Loess Plateau quickly deceased by 17.3%from 1998 to 2003,and then gradually restored to 1.03×107 hm2 in 2010.Thereafter,it slightly decreased to 1.02×107 hm2(94.6%of the area in 1998)in 2014.By contrast,total FCP generally showed an apparent growth trend,averagely increased by 1.71%per year in the whole plateau during 1998–2014.This increase was jointly contributed by the improved yield of individual crops,and the adjustment of cropping structure,i.e.,the expansion of high yield maize crop.The factor decomposition analysis results indicate that the sown area shrinkage only reduced the growth rate of total FCP by 0.29%per year during 1998–2014,although a significant impact was found for the early stage of 1999–2003.The results suggest that the implementation of GFG program would not induce an obvious risk of the food security.Therefore,it is suggested that the GFG program should be set as a long-term strategic policy,by not only supporting the conversion of slope farmlands,but also helping local farmers to seek sustainable ways of land use to improve the income and livelihood.It can be combined with the poverty eradication program,to simultaneously achieve the national goals of ecological civilization building and the livelihood improvement of rural people in the Loess Plateau.Considering rainfall limitation,the conversion of slope farmlands should be prioritized to grasslands.
基金supported as a special project by the Agriculture Ministry of China(Grant No.201503119)the Natural Science Foundation of China(Grant No.41471232)
文摘The dynamics of soil organic carbon(SOC)in cropland is one of the central issues related to both soil fertility and environmental safety. However, little information is available at county level regarding the spatiotemporal variability of SOC in the southwestern mountainous region of China. Thus, this study aimed to explore spatiotemporal changes of SOC in the cultivated soil layer of dry land in Mojiang County,Yunnan Province, China. Data were obtained from the second national soil survey(SNSS) of 1985 and soil tests for fertilizer application carried out by the Mojiang Agricultural Bureau in 2006. The ANOVA test was applied to determine any significant differences between the datasets, while semivariogram analysis was performed on geostatistics via an ordinary Kriging method in order to map spatial patterns of soil organic carbon density(SOCD). The results revealed that SOCD in the cultivated soil layer significantly decreased from 3.93 kg m^(-2) in 1985 to 2.89 kg m^(-2) in 2006, with a total soil organic carbon stock(SOCS) decrease of 41.54×10~4 t over the same period. SOCS levels fell most markedly in yellow-brown soil at a rate of51.52%, while an increase of 8.70% was found in the analysed latosol. Geostatistical analysis also showed that the recorded changes in SOCD between 1985 and2006 were spatially structured. The decreasing trend might be attributed to the combined action of intense cultivation, major crop residue removal without any protective tillage measures, unreasonable fertilization and natural climatic diversity inducing a large decrease in SOC in the studied cultivated dry land region of Mojiang County. Therefore, management measures such as protective tillage should be undertaken in order to enhance soil C sequestration.
文摘Agriculture needs to produce more food to feed the growing population in the 21st century.It makes the reference crop water requirement(WREQ)a major challenge especially in regions with limited water and high water demand.Iran,with large climatic variability,is experiencing a serious water crisis due to limited water resources and inefficient agriculture.In order to overcome the issue of uneven distribution of weather stations,gridded Climatic Research Unit(CRU)data was applied to analyze the changes in potential evapotranspiration(PET),effective precipitation(EFFPRE)and WREQ.Validation of data using in situ observation showed an acceptable performance of CRU in Iran.Changes in PET,EFFPRE and WREQ were analyzed in two 30-a periods 1957-1986 and 1987-2016.Comparing two periods showed an increase in PET and WREQ in regions extended from the southwest to northeast and a decrease in the southeast,more significant in summer and spring.However,EFFPRE decreased in the southeast,northeast,and northwest,especially in winter and spring.Analysis of annual trends revealed an upward trend in PET(14.32 mm/decade)and WREQ(25.50 mm/decade),but a downward trend in EFFPRE(-11.8 mm/decade)over the second period.Changes in PET,EFFPRE and WREQ in winter have the impact on the annual trend.Among climate variables,WREQ showed a significant correlation(r=0.59)with minimum temperature.The increase in WREQ and decrease in EFFPRE would exacerbate the agricultural water crisis in Iran.With all changes in PET and WREQ,immediate actions are needed to address the challenges in agriculture and adapt to the changing climate.
基金the Key Laboratory Open Subjects of Xinjiang Uygur Autonomous Region Science and Technology Department(2020D04038)the Key Project of Natural Science Foundation of Xinjiang Uygur Autonomous Region(2021D01D06)the National Natural Science Foundation of China(41961059).
文摘The ecological quality of inland areas is an important aspect of the United Nations Sustainable Development Goals(UN SDGs).The ecological environment of Northwest China is vulnerable to changes in climate and land use/land cover,and the changes in ecological quality in this arid region over the last two decades are not well understood.This makes it more difficult to advance the UN SDGs and develop appropriate measures at the regional level.In this study,we used the Moderate Resolution Imaging Spectroradiometer(MODIS)products to generate remote sensing ecological index(RSEI)on the Google Earth Engine(GEE)platform to examine the relationship between ecological quality and environment in Xinjiang during the last two decades(from 2000 to 2020).We analyzed a 21-year time series of the trends and spatial characteristics of ecological quality.We further assessed the importance of different environmental factors affecting ecological quality through the random forest algorithm using data from statistical yearbooks and land use products.Our results show that the RSEI constructed using the GEE platform can accurately reflect the ecological quality information in Xinjiang because the contribution of the first principal component was higher than 90.00%.The ecological quality in Xinjiang has increased significantly over the last two decades,with the northern part of this region having a better ecological quality than the southern part.The areas with slightly improved ecological quality accounted for 31.26%of the total land area of Xinjiang,whereas only 3.55%of the land area was classified as having a slightly worsen(3.16%)or worsen(0.39%)ecological quality.The vast majority of the deterioration in ecological quality mainly occurred in the barren areas Temperature,precipitation,closed shrublands,grasslands and savannas were the top five environmental factors affecting the changes in RSEI.Environmental factors were allocated different weights for different RSEI categories.In general,the recovery of ecological quality in Xinjiang has been controlled by climate and land use/land cover during the last two decades and policy-driven ecological restoration is therefore crucial.Rapid monitoring of inland ecological quality using the GEE platform is projected to aid in the advancement of the comprehensive assessment of the UN SDGs.
基金This work was supported by the National Natural Science Foundation of China(Grant No.41771196)the Second Tibetan Plateau Scientific Expedition and Research(No.2019QZKK0603)National Key R&D Program of China(No.2016YFC0501701).
文摘Understanding the trade-offs among ecosystem services(ESs)at multiple scales is a key challenge to effective environmental management.However,the scale effect of ESs trade-offs in the Qinghai-Tibetan Plateau(QTP)has received little attention.This study investigated the scale effects of ESs trade-offs in Bailongjiang Watershed(BLJW),a typical transitional ecotone from the Loess Plateau to the Tibetan Plateau with multiple ESs,intensive human activities and frequent geological disasters in the Eastern Margin of the QTP,China.Four key ESs including food supply(FS),soil conservation(SC),water conservation(WC),and habitat quality(HQ)in BLJW in 1990,2002,and 2016 were mapped to analyze the scale effects at the watershed,county,and township scales.The results indicated varying scale-related temporal and spatial relationships among FS,SC,WC,and HQ.The trade-offs between FS-SC and FS-WC initially increased and then decreased during 1990-2002 and 2002-2016,respectively,while the trade-offs between SC-WC,SC-HQ,HQ-WC,and HQ-FS first decreased and then increased at the same period.The magnitudes of the trade-offs among the four ESs are in the order of watershed scale>township scale>county scale.Among the major land-use types in BLJW,the trade-offs between WC-FS and between HQ-FS in farmland and grassland were higher than those of other land uses.There is a strong trade-off between SC-HQ in forestland and a weak trade-off between SC-WC in farmland and grassland.The trade-offs between the six ESs pairs varied and were scale-dependent mainly due to spatial heterogeneity in the landscape and in human activities.Understanding the ESs trade-offs at the watershed,county,and township scales provides a scientific basis for the formulation of environmental management strategies at appropriate spatial scales.At the BLJW watershed scale,more attention should be paid on farmland and grassland planning and its management,also,forestland should be enlarged if possible.At the county and township scales,land consolidation and planning should be paid more attention to develop ecological agricultural tourism and multi-functional landscapes for strategic spatial planning and integrated watershed management.
基金supported and financed by the National key Research and Development Program of China(2019YFA0607400)the Fundamental Research Funds for the Central Universities, China (CCNU19TS045)
文摘Crop planting patterns are an important component of agricultural land systems.These patterns have been significantly changed due to the combined impacts of climatic changes and socioeconomic developments.However,the extent of these changes and their possible impacts on the environment,terrestrial landscapes and rural livelihoods are largely unknown due to the lack of spatially explicit datasets including crop planting patterns.To fill this gap,this study proposes a new method for spatializing statistical data to generate multitemporal crop planting pattern datasets.This method features a two-level model that combines a land-use simulation and a crop pattern simulation.The output of the first level is the spatial distribution of the cropland,which is then used as the input for the second level,which allocates crop censuses to individual gridded cells according to certain rules.The method was tested using data from 2000 to 2019 from Heilongjiang Province,China,and was validated using remote sensing images.The results show that this method has high accuracy for crop area spatialization.Spatial crop pattern datasets over a given time period can be important supplementary information for remote sensing and thus support a wide range of application in agricultural land systems.
基金The Second Tibetan Plateau Scientific Expedition and Research Program,No.2019QZKK0404。
文摘The Qinghai-Tibet Plateau(QTP),also known as the Third Pole of the Earth,is a vital ecological security barrier for China.It is a tremendously sensitive region affected by the impacts of global climate change.The escalating intensity of climate change has presented profound challenges to its ecosystem functions and stability.This study first analyzes the spatiotemporal variations of the QTP ecosystem patterns and the key functions of the Plateau including water conservation,soil conservation,and windbreak and sand fixation from 2000 to 2020.It clarifies the regional differences in ecosystem functions and their importance,further evaluates the stability of ecosystem functions,and lays a scientific foundation for an ecological civilization on the Plateau by implementing conservation and restoration projects.The main results show that:(1)From 2000 to 2020,the wetland area in the QTP increased,while the grassland area significantly decreased.There were improvements in water conservation and windbreak and sand fixation capacities,with annual rates of change being 3.57m~3·ha^(-1)·a^(-1)and 0.23 t·ha^(-1)·a^(-1),respectively.However,the overall soil conservation trend declined during the same period,with an annual change rate of-0.16 t·ha^(-1)·a^(-1).(2)The core areas of water conservation,soil conservation,and windbreak and sand fixation on the QTP accounted for 12.7%,13.9%,and 14.2%of the total area,respectively.The core water conservation areas are mainly the southeastern QTP,Sanjiangyuan,and Naqu,while the core windbreak and sand fixation areas were concentrated in the central and western parts of the Plateau.The core soil conservation areas surrounded the entire interior of the Plateau.(3)From 2000 to 2020,the water conservation,soil conservation,and windbreak sand-fixation function on the QTP had higher stability in the southeastern and central parts,while stability was lower in the western region.Considering the stability assessment and ecological protection and restoration practices,the QTP can be divided into three major categories and 16 ecological functional zones.Differentiated ecological protection and restoration efforts can be implemented based on the different core ecosystem functions and zoning.
基金Supported by the National Key Research and Development Program of China(2016YFC0500203 and 2017YFC0503803)National Natural Science Foundation of China(31971507)Science and Technology Program of Qinghai Province(2018-ZJ-T09)。
文摘How vegetation phenology responds to climate change is a key to the understanding of the mechanisms driving historic and future changes in regional terrestrial ecosystem productivity. Based on the 250-m and 8-day moderate resolution imaging spectroradiometer(MODIS) normalized difference vegetation index(NDVI) data for 2000-2014 in the Three-River Source Region(TRSR) of Qinghai Province, China, i.e., the hinterland of the Tibetan Plateau, we extracted relevant vegetation phenological information(e.g., start, end, and length of growing season) and analyzed the changes in the TRSR vegetation in response to climate change. The results reveal that, under the increasingly warm and humid climate, the start of vegetation growing season(SOS) advanced 1.03 day yr-1 while the end of vegetation growing season(EOS) exhibited no significant changes, which led to extended growing season length. It is found that the SOS was greatly affected by the preceding winter precipitation, with progressively enhanced precipitation facilitating an earlier SOS. Moreover, as the variations of SOS and its trend depended strongly on topography, we estimated the elevation break-points for SOS. The lower the elevations were, the earlier the SOS started. In the areas below 3095-m elevation, the SOS delay changed rapidly with increasing elevation;whereas above that, the SOS changes were relatively minor. The SOS trend had three elevation break-points at 2660, 3880, and 5240 m.
基金Guangxi Natural Science Foundation,No.2020GXNSFAA297176National Natural Science Foundation of China,No.U21A2022,No.42101369Youth Teacher Scientific Research Ability Improvement Project of Guangxi,No.2021KY0393。
文摘Accurate and rapid evaluation of the regional eco-environment is critical to policy formulation.The remote sensing ecological index(RSEI)model of the Guangxi Beibu Gulf Economic Zone(GBGEZ)during 2001-2020 was established and evaluated using four indices:dryness,wetness,greenness,and heat.This paper proposes an information granulation method for remote sensing based on the RSEI index value that uses granular computing.We found that:(1)From 2001 to 2020,the eco-environmental quality(EEQ)of GBGEZ tended to improve,and the spatial difference tended to expand.The regional spatial distribution of the eco-environment is primarily in the second-level and third-level areas,and the EEQ in the east and west is better than that in the middle.The contribution of greenness,wetness,and dryness to the improvement of EEQ in the study region increased year by year.(2)From 2001to 2020,the order of the contribution of the EEQ index in the GBGEZ was dryness,wetness,greenness,and heat.(3)The social and economic activities in the study region had a certain inhibitory effect on the improvement of the EEQ.
基金National Natural Science Foundation of China,No.41861040, No.41761047, No.41961027。
文摘Sensitivity assessment is useful for monitoring land desertification. Research into how to prevent and control desertification is also important. In the arid region of northwest China, desertification is becoming worse and is a serious problem that affects local sustainable development. Based on remote-sensing and geographic information system technology, this study establishes a 'soil-terrain-hydrology-climate-vegetation' desertification sensitivity comprehensive evaluation system to reflect the spatiotemporal changes of land desertification, and proposes a spatial distance model to calculate a desertification sensitivity index. The spatiotemporal change characteristics of land desertification sensitivity in northwest China are quantitatively assessed from 2000 to 2017. Moreover, the main driving factors are analyzed using the geographical detector method. The results show the following.(1) Terrain, soil, climate, vegetation and hydrology affect and restrict each other, and constitute the background conditions of the distributions and changes of sensitivity to desertification in northwest China.(2) Desertification sensitivity generally displays a low distribution characteristic on the periphery of the area and a high one in the interior. The low-sensitivity regions are mainly in the five major mountain ranges(Altai Mountains, Tianshan Mountains, Kunlun Mountains, Altun Mountains and Qilian Mountains), while the high-sensitivity regions are mainly in regions such as the Junggar Basin, the Tarim Basin and the Inner Mongolia Plateau, as well as the Taklimakan Desert, Badain Jaran Desert and Tengger Desert. The spatial distribution of desertification sensitivity is obviously regional, and the high-and low-sensitivity regions have clear boundaries and a concentrated distribution.(3) With regard to spatiotemporal evolution, changes in desertification sensitivity since 2000 have been predominantly stable, and the overall sensitivity has displayed a slowly decreasing trend, indicating that potential desertification regions are decreasing annually and that some achievements have been made in the control of regional desertification.(4) Soil and climate play a direct role in the driving factors of desertification in northwest China, and these have been found to be the most important influential factors. Vegetation is the most active and basic factor in changing the sensitivity. In addition, topography and hydrology play a role in restricting desertification changes. Socio-economic factors are the most rapid factors affecting regional desertification sensitivity, and their impacts tend to be gradually increasing. In general, desertification has been effectively controlled in northwest China, and positive results have been achieved in such control. However, against the backdrop of intensified global climate change, increasingly prominent human activities and new normals of socio-economic development, the monitoring, assessment and control of desertification in China still have a long way to go.
基金Second Tibetan Plateau Scientific Expedition and Research Program,No.2019QZKK0201Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA20020102,No.XDA20060201+2 种基金State Key Laboratory of Cryospheric Science,No.SKLCS-ZZ-2021National Natural Science Foundation of China,No.41721091,42001067National Cryosphere Desert Data Center,No.20D03。
文摘Glaciers are a reliable freshwater resource in arid regions of West China and the vulnerability of its changes is closely related to regional ecosystem services and economic sustainable development. Here, we took the Qilian Mountains as an example and analyzed the spatiotemporal characteristics of glacier changes from 1998 to 2018, based on remote sensing images and the Second Chinese Glacier Inventory. We estimated the basic organizational framework and evaluation index system of glacier change vulnerability from exposure, sensitivity and adaptability, which covered the factors of physical geography, population status and socio-economic level. We analyzed the spatial and temporal evolutions of glacier change vulnerability by using the vulnerability evaluation model. Our results suggested that:(1) Glacier area and volume decreased by 71.12±98.98 km^(2) and 5.59±4.41 km^(3), respectively, over the recent two decades, which mainly occurred at the altitude below 4800 m, with an area shrinking rate of 2.5%. In addition, glaciers in the northern aspect(northwest, north and northeast) had the largest area reduction. Different counties exhibited remarkable discrepancies in glacier area reduction, Tianjuan and Minle presented the maximum and minimum decrease, respectively.(2) Glacier change vulnerability level showed a decreasing trend in space from the central to the northwestern and southeastern regions with remarkable differences. Vulnerability level had increased significantly over time and was mainly concentrated in moderate, high and extreme levels with typical characteristics of phases and regional complexity. Our study can not only help to understand and master the impacts of recent glacier changes on natural and social aspects but also be conducive to evaluate the influences of glacier retreat on socio-economic developments in the future, thus providing references for formulating relevant countermeasures to achieve regional sustainable development.
