BACKGROUND Gastric bezoars are masses of indigestible material that accumulate in the stomach,causing nausea,abdominal pain,and vomiting.Persimmon bezoars(diospyrobezoars),which comprise tannins and fibers from persim...BACKGROUND Gastric bezoars are masses of indigestible material that accumulate in the stomach,causing nausea,abdominal pain,and vomiting.Persimmon bezoars(diospyrobezoars),which comprise tannins and fibers from persimmons,are relatively rare but may cause significant gastric complications,including gastric outlet obstruction or ileus.Although computed tomography(CT)is a useful ima-ging tool,diagnosing bezoars can be challenging because their density is similar to that of food debris and gastric content.CASE SUMMARY Here,we report the case of a 72-year-old woman with a persimmon bezoar that was diagnosed using serial CT imaging and confirmed by endoscopy.CT perfor-med over several months revealed changes in the internal structure and density of the bezoar,suggesting progressive hardening.The patient had a history of a par-tial gastrectomy and excessive persimmon consumption,both of which are risk factors for bezoar formation.Endoscopic fragmentation of the bezoar successfully resolved symptoms.CONCLUSION Gastric bezoars,particularly persimmon bezoars,present diagnostic challenges because of their variable imaging characteristics.Serial CT can document tem-poral changes in bezoar density,potentially reflecting changes in hardness.Early diagnosis and endoscopic treatment are essential for effective management,particularly in patients with predisposing factors.This case underscores the im-portance of considering bezoars in the differential diagnosis of gastric masses,and highlights the value of CT for monitoring changes in bezoar characteristics over time.展开更多
It is important to understand the effects of temporal changes in microbial communities in the acidic soils of tea orchards with different fertilizers. A field experiment involving organic fertilizer （OF）, chemical f...It is important to understand the effects of temporal changes in microbial communities in the acidic soils of tea orchards with different fertilizers. A field experiment involving organic fertilizer （OF）, chemical fertilizer （CF）, and unfertilized control （CK） treatments was arranged to analyze the temporal changes in the bacterial and archaeal communities at bimonthly intervals based on the 16S ribosomal RNA （rRNA） gene using terminal restriction fragment length polymorphism （T-RFLP） profiling. The abundances of total bacteria, total archaea, and selected functional genes （bacterial and archaeal amoA, bacterial narG, nirK, nirS, and nosZ） were determined by quantitative poly- merase chain reaction （qPCR）. The results indicate that the structures of bacterial and archaeal communities varied significantly with time and fertilization based on changes in the relative abundance of dominant T-RFs. The abundancy of the detected genes changed with time. The total bacteria, total archaea, and archaeal amoA were less abundant in July. The bacterial amoA and denitrifying genes were less abundant in September, except the nirK gene. The OF treatment increased the abundance of the observed genes, while the CF treatment had little influence on them. The soil temperature significantly affected the bacterial and archaeal community structures. The soil moisture was signif- icantly correlated with the abundance of denitrifying genes. Of the soil chemical properties, soil organic carbon was the most important factor and was significantly correlated with the abundance of the detected genes, except the nirK gene. Overall, this study demonstrated the effects of both temporal alteration and organic fertilizer on the structures of mi- crobial communities and the abundance of genes involved in the nitrogen cycle.展开更多
By studying the county-level census data of 1990 and 2000, we analyzed the spatial and temporal changes in the floating population in China between 1990 and 2000. The results of the analysis revealed the following cha...By studying the county-level census data of 1990 and 2000, we analyzed the spatial and temporal changes in the floating population in China between 1990 and 2000. The results of the analysis revealed the following characteris- tics. First, the spatial distribution of the migrants (referred to as 'floaters' in this paper) became increasingly concentrated in the cities during the 1990s. Second, the number of floaters increased rapidly during this period, and the area in which the floaters settled expanded quickly into four population explosion belts: the coast, the Changjiang River Delta, the Beijing-Guangzhou Railway and national border belts. Third, the number of inter-province floaters increased rapidly and exceeded that of intra-province floaters in the 1990s. In addition, to obtain a quantitative relationship between the number of floaters and 10 socio-economic variables by using statistical methods and also to find the chiefly important pulling factors of the migration destination, the authors selected approximately 100 cities with the largest population of floaters. Consequently, we found that four factors-GDP, passenger trips per 10,000 persons, per capita GDP and foreign direct investment-could provide an explanation for 83.7% of the number of floaters in 2000. The GDP showed the highest correlation with the number of floaters, suggesting that a highly developed economy is the most important factor that attracts floaters. Furthermore, a fairly close relationship between the number of floaters and the GDP was also found in 2000 for all the counties.展开更多
Detecting temporal changes in fault zone properties at seismogenic depth have been a long-sought goal in the seismological community for many decades. Recent studies based on waveform analysis of repeating earthquakes...Detecting temporal changes in fault zone properties at seismogenic depth have been a long-sought goal in the seismological community for many decades. Recent studies based on waveform analysis of repeating earthquakes have found clear temporal changes in the shallow crust and around active fault zones associated with the occurrences of large nearby and teleseismic earthquakes. However, repeating earthquakes only occur in certain locations and their occurrence times cannot be controlled, which may result in inadequate sampling of the interested regions or time periods. Recent developments in passive imaging via auto- and cross-correlation of ambient seismic wavefields （e.g., seismic noise, earthquake coda waves） provide an ideal source for continuous monitoring of temporal changes around active fault zones. Here we conduct a systematic search of temporal changes along the Parkfield section of the San Andreas fault by cross-correlating relatively high-frequency （0.4-1.3 Hz） ambient noise signals recorded by 10 borehole stations in the High Resolution Seismic Network. After using stretch/compressed method to measure the delay time and the decorrelation-index between the daily noise cross-correlation functions （NCCFs）, we find clear temporal changes in the median seismic velocity and decorrelation-index associated with the 2004 M6.0 Parkfield earthquake. We also apply the same procedure to the seismic data around five regional/teleseismic events that have triggered non-volcanic tremor in the same region, but failed to find any clear temporal changes in the daily NCCFs. The fact that our current technique can detect temporal changes from the nearby but not regional and teleseismic events, suggests that temporal changes associated with distance sources are very subtle or localized so that they could not be detected within the resolution of the current technique （-0.2%）.展开更多
[Objective]The aim was to study the spatial and temporal changes of extreme precipitation events in Ningxia in recent 50 years.[Method]Using dally precipitation data at 20 stations in Ningxia from 1961 to 2010,and def...[Objective]The aim was to study the spatial and temporal changes of extreme precipitation events in Ningxia in recent 50 years.[Method]Using dally precipitation data at 20 stations in Ningxia from 1961 to 2010,and defining the threshold value of extreme precipitation in each sta-tion by percentage method,choosing indicators such as precipitation,frequency and intensity of extreme precipitation events,the characteristics of the spatial and temporal distribution and linear trend of extreme precipitation events in Ningxia were analyzed based on linear regression and M-K non-parameter statistical test method.[Result]The percentage method suggested the threshold value of average extreme precipitation in Ningxia in recent 50 years decreased from south to north.The large threshold value was in southern Haiyuan,Tongxin and northern Yancheng,which was similar to the distribution of mean annual precipitation in Ningxia.In recent 50 years,extreme precipitation frequency and extreme precipitation de-creased in most part of Ningxia but the intensity tended to strengthen.Study of extreme precipitation in Mahuang Mountain and Liupan Mountain in-dicated that precipitation frequency,intensity and extreme precipitation reduced.Annual extreme precipitation frequency narrowed and then in-creased after 1994 and had mutation in 2003.Annual extreme precipitation intensity enhanced since 1984.Mutation took place in 1984.Intensity in Liupan Mountain had weakened since 1978.[Conclusion]The study provided theoretical basis for the mutation of climate in Ningxia.展开更多
Wetlands on the Qinghai-Tibetan Plateau （QTP） perform a dazzling array of vital ecological functions and are one of the most fragile ecosystems in the world. Timely and accurate information describing wetland resour...Wetlands on the Qinghai-Tibetan Plateau （QTP） perform a dazzling array of vital ecological functions and are one of the most fragile ecosystems in the world. Timely and accurate information describing wetland resources and their changes over time is becoming more important in their protection and conservation. By using remote sensing data, this study intended to investigate spatial distribution and temporal variations of wetlands on the QTP at different watershed scales from 1970s to 2010s. Results show that wetlands on the QTP have undergone widespread degradation from 1970s to 2010s, with nearly 6.4% of their area being lost. Areas of freshwater marsh, salt marsh and wet meadow declined by 46.6%, 53.9% and 15.6%, respectively, while lake area increased by 14.6%. The most extensive losses of natural wet/ands have occurred in endorheic basins, such as in the Kunlun-Altun-Qilian Drainage Basin and Qiangtang Basin, which shrank by 44.5% and 33.1%, respectively. A pronounced increase in temperature tends to facilitate the evaporation process and reduce water availability for wetlands, One-third of the wetlands on the QTP are under threat of being submerged due to lakes rising in recent years. More research is needed to gain insight into the interaction mechanisms behind observed variations and potential impacts from further warming in the future.展开更多
Forest structure changes continuously by natural and anthropogenic effects. Because the level of goods and services provided by forest ecosystems are related to this structure, some attributes have to be controlled wh...Forest structure changes continuously by natural and anthropogenic effects. Because the level of goods and services provided by forest ecosystems are related to this structure, some attributes have to be controlled while they are being managed. In this paper we describe the long-term temporal changes in land area and landscape metrics related to different land uses of a managed forest in Turkey. The study was carried out for the Daday Forest Planning Unit located in the west Black Sea region of northern Turkey. The total area is 16,813 ha and besides wood production, it is managed for erosion control, public health, aesthetics, and recreation. Stand type maps that were constructed in 1970,1989, 1999, and 2010 were used in this analysis. Transition matrixes that illustrate area changes among cover types and temporal changes on some landscape metrics were obtained using Geographic Information Systems. Stands were separated into small patches, and thus the number of patches increased nearly two-fold between 1970 and 2010. The total forest edge increased and through the associated fragmentation, the amount of core forest area decreased at the landscape scale. Landscape metrics were applied to digitized versions of historical maps to assess how forest area changed. Human use of the land has changed, forest management practices have evolved, and these along with natural forest growth have contributed to interesting changes in landscape character.展开更多
In order to understand the temporal changes of botanical composition in grassland ecosystem, and to clarify the relation between these changes and environmental impacts, such as climatic factors and artificial disturb...In order to understand the temporal changes of botanical composition in grassland ecosystem, and to clarify the relation between these changes and environmental impacts, such as climatic factors and artificial disturbance, a grazing trail was carried out during a 21-year period from 1974 at a sown grassland of the National Grassland Research Institute, located in Nishinasuno, the central area of Japan. The data sets of biomass for each mouth(from April to November)of the 21 year period were analyzed in this paper. The botanical composition of aboveground biomass varied greatly with both season and year. The biomass ratio of improved herbage species to invaded native plants gradually decreased each year. This may have been owing to meteorological factors, such as low air-temperature in winter, dry and hot summers, grassland management(including grazing intensity and fertilizer application), and inter-specific competition between native and introduced herbage plants.展开更多
Freezing–thawing indices serve as a comprehensive indicator of both the duration of the freezing/thawing periods and the degree of cold and heat in a given region.In-depth analysis of the freezing-thawing indices not...Freezing–thawing indices serve as a comprehensive indicator of both the duration of the freezing/thawing periods and the degree of cold and heat in a given region.In-depth analysis of the freezing-thawing indices not only enables the prediction of permafrost distribution and its dynamic changes,but also facilitates the assessment of damage risk to infrastructure under freeze-thaw action.In this paper,the air/ground freezing–thawing indices from 1987 to 2017,based on daily temperature observations from meteorological stations along the China–Nepal Highway(CNH),were calculated,and their spatial and temporal variation patterns were analyzed.The results showed that:(1)Both mean annual air temperature and mean annual ground surface temperature along the CNH fluctuated upward,with climate tendency rates of 0.43 and 0.52.C·(10a)~(-1),respectively;(2)The number of days with negative air temperature and ground temperature showed fluctuated downward,with change rates of-8.6 and-8.3 d·(10a)~(-1),respectively;(3)The ranges of air freezing index,air thawing index,ground freezing index,and ground thawing index over the years were 157.05-458.88°C·d,2034.20-2560.73°C·d,108.78-396.83°C·d,and 3515.25-4288.67°C·d,respectively.The climate tendency rates were-5.42,10.22,-6.79,and 12.14.C·d·a-1,respectively,showing a general warming trend;(4)The air freezing index,ground freezing index,and ground thawing index changed abruptly in 1999,2000,and 2002,respectively,evincing significant changes after 2002.The research results can provide a basis for the risk assessment of freezing–thawing erosion and the prevention and control of permafrost engineering diseases along the CNH.展开更多
A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion ...A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion of the hydrodynamic regimes of the estuary. Spatially, the SSC from Xuliujing downwards to Hangzhou Bay increases almost constantly, and the suspended sediment in the inner estuary shows higher concentration in summer than in winter, while in the outer estuary it shows higher concentration in winter than in summer, and the magnitude is greater in the outer estuary than in the inner estuary, greater in the Hangzhou Bay than in the Yangtze River estuary. The sediments discharged by the Yangtze River into the sea are resuspended by marine dynamics included tidal currents and wind waves. Temporally, the SSC shows a pronounced neap-spring tidal cycle and seasonal variations. Furthermore, through the analysis of dynamic mechanism, it is concluded that wave and tidal current are two predominant factors of sediment resuspension and control the distribution and changes of SSC, in which tidal currents control neap-spring tidal cycles, and wind waves control seasonal variations. The ratio between river discharge and marine dynamics controls spatial distribution of SSC.展开更多
Algal blooms have become a worldwide environmental concern due to water eutrophication.Dianchi Lake in Yunnan Province,China is suffering from severe eutrophication and is listed in the Three Important Lakes Restorati...Algal blooms have become a worldwide environmental concern due to water eutrophication.Dianchi Lake in Yunnan Province,China is suffering from severe eutrophication and is listed in the Three Important Lakes Restoration Act of China.Hydrothermal liquefaction allows a promising and direct conversion of algal biomass into biocrude oil.In this study,algal samples were collected from Dianchi Lake after a separation procedure including dissolved air flotation with polyaluminum chloride and centrifugation during four months,April,June,August and October.The algal biochemical components varied over the period;lipids from 0.7%to 2.1%ash-free dry weight(afdw),protein from 20.9%to 33.4%afdw and ash from 36.6%to 45.2%dry weight.The algae in June had the highest lipid and protein concentrations,leading to a maximum biocrude oil yield of 24.3%afdw.Biodiversity analysis using pyrosequencing revealed different distributions of microbial communities,specifically Microcystis in April(89.0%),June(63.7%)and August(84.0%),and Synechococcus in April(2.2%),June(12.0%)and August(1.0%).This study demonstrated remarkable temporal changes in the biochemical composition and biodiversity of algae harvested from Dianchi Lake and changes in biocrude oil production potential.展开更多
This paper takes poverty-stricken countyas the basic unit, and selects net income per peasantto study the poverty status in Hebei Province during1986~2000.Temporal and spatial changes of poverty-stricken areas are ana...This paper takes poverty-stricken countyas the basic unit, and selects net income per peasantto study the poverty status in Hebei Province during1986~2000.Temporal and spatial changes of poverty-stricken areas are analyzed. The result shows thatpoverty-stricken areas in Hebei Province distributedconcentratedly and the areas decreased during1986~2000, the net income per peasant was on therise with an increasing speed in off-poverty countiesbeing slightly higher than that in poverty-strickencounties, but the growth rate was extremely unstable,rising slowly in off-poverty counties while droppingin poverty-stricken counties. The main driving forcesthat influenced temporal and spatial changes wereeconomic development of the whole province,ecological environment quality, infrastructureconditions and radiation of the key city. On thisbasis, some anti-poverty countermeasures suitable tolocal conditions are proposed.展开更多
Affected by topographical conditions,the distribution of cultivated land in karst areas is relatively fragmented.More effective cultivated land protection measures can be taken in a targeted manner by grasping the spa...Affected by topographical conditions,the distribution of cultivated land in karst areas is relatively fragmented.More effective cultivated land protection measures can be taken in a targeted manner by grasping the spatial and temporal distribution characteristics of regional cultivated land.In this study,with the cultivated land of four county-level administrative regions(Debao County,Jingxi City,Daxin County,and Tiancheng County)in typical karst landform areas in southwestern Guangxi as the research object,combining with the spatial analysis function of the GIS software platform,the spatial distribution characteristics and temporal and spatial changes of cultivated land in the study area were investigated from 2009 to 2020 using the quantitative analysis method of landscape pattern indices,revealing the main problems of cultivated land utilization,and the multi-dimensional management ideas of cultivated land protection in karst areas under the background of rural revitalization strategy were proposed.展开更多
Rapidly monitoring regional water quality and the changing trend is of great practical and scientific significance,especially for the Beijing-Tianjin-Hebei(BTH)region of China where water resources are relatively scar...Rapidly monitoring regional water quality and the changing trend is of great practical and scientific significance,especially for the Beijing-Tianjin-Hebei(BTH)region of China where water resources are relatively scarce and inland water bodies are generally small.The remote sensing data of the GF 1 satellite launched in 2013 have characteristics of high spatial and temporal resolution,which can be used for the dynamic monitoring of the water environment in small lakes and reservoirs.However,the water quality remote sensing monitoring model based on the GF 1 satellite data for lakes and reservoirs in BTH is still lacking because of the considerable differences in the optical characteristics of the lakes and reservoirs.In this paper,the typical reservoirs in BTH-Guanting Reservoir,Yuqiao Reservoir,Panjiakou Reservoir,and Daheiting Reservoir are taken as the study areas.In the atmospheric correction of GF 1-WFV,the relative radiation normalized atmospheric correction was adopted after comparing it with other methods,such as 6 S and FLAASH.In the water clarity retrieval,a water color hue angle based model was proposed and outperformed other available published models,with the R 2 of 0.74 and MRE of 31.7%.The clarity products of the four typical reservoirs in the BTH region in 2013-2019 were produced using the GF 1-WFV data.Based on the products,temporal and spatial changes in clarity were analyzed,and the main influencing factors for each water body were discussed.It was found that the clarity of Guanting,Daheiting,and Panjiakou reservoirs showed an upward trend during this period,while that of Yuqiao Reservoir showed a downward trend.In the influencing factors,the water level of the water bodies can be an important factor related to the water clarity changes in this region.展开更多
Birdsong is an important secondary sexual trait which may vary between but also within species.Intraspecific variation is generally studied either on the geographical or on the temporal scale;most of the studies explo...Birdsong is an important secondary sexual trait which may vary between but also within species.Intraspecific variation is generally studied either on the geographical or on the temporal scale;most of the studies exploring the variation of song over time,however,focused on species with rather simple songs.In this study,we explored the temporal changes in song of a complex songster,the Thrush Nightingale(Luscinia luscinia),recorded after 33 years(in 1986 and 2019)at the same locality in south-eastern Finland.Our analysis revealed a complete turnover of song types over the study period,with no song type shared between the two recording years.In contrast,40%of the originally recorded syllable types were still found in the repertoires of recently recorded males.Their song type repertoires were significantly smaller but the songs themselves were on average longer compared to the 1986 recordings.Repertoires of both syllables and song types were more shared between males recorded in 1986 than between those from 2019.We discuss the processes that may have contributed to these temporal changes in song and call for more detailed studies of song evolution in wild populations.展开更多
Introduction:Coal-burning pollution type of endemic fluorosis remains a significant public health threat in certain rural areas of China.This study aimed to analyze the long-term trends in dental fluorosis prevalence ...Introduction:Coal-burning pollution type of endemic fluorosis remains a significant public health threat in certain rural areas of China.This study aimed to analyze the long-term trends in dental fluorosis prevalence in coal-burning fluorosis areas in China from 2009 to 2023.Methods:We collected and analyzed dental fluorosis detection rates among children aged 8–12 in 12 coalburning fluorosis provincial-level administrative divisions(PLADs)of China(2009–2023).The optimal Autoregressive Integrated Moving Average with Exogenous Inputs(ARIMAX)time series model was used to predict dental fluorosis detection rates in children from 2019 to 2023.The GeoDa(version 1.20.0;GeoDa Institute)software was employed for spatial analysis,while the SaTScan(version 10.1;GeoDa Institute)was used to analyze spatial-temporal aggregation patterns.Results:From 2009 to 2023,the dental fluorosis detection rates in children aged 8–12 years showed a decreasing trend,declining from 49.51%to 1.56%.After 2016,achieving the elimination standard(<15%).There was a goodagreement between the observed detection rates andexpected values,with a relative risk(RR)of 0.98.Global analysis shows that the detection rate of dental fluorosis is randomly dispersed.The Moran’s I index for dental fluorosis detection rates was positive in 2009,2011,and 2013,and negative in other years,with Z-values ranging from−1.53 to 0.99.Local analysis indicates that Yunnan Province has continuously presented a low-high aggregation pattern from 2011 to 2013.Space-time analysis identified that Yunnan was classified as a highprevalence cluster in 2022–2023[odds ratio(OR)=1.07,Log likelihood ratio(LLR)=30.45,P<0.05].Conclusions:China has achieved remarkable success in the prevention and control of coal-burning fluorosis.These spatial findings provide critical reference values to support targeted prevention strategies for coalburning fluorosis.展开更多
Objective To determine the extent of the obesity epidemic in school‐aged Chinese children in 2010 and track the increasing trend in different socioeconomic regions over the preceding 25 years. Strategies for preventi...Objective To determine the extent of the obesity epidemic in school‐aged Chinese children in 2010 and track the increasing trend in different socioeconomic regions over the preceding 25 years. Strategies for preventing childhood obesity are suggested. Methods We used a dataset provided by the Chinese National Survey on Students’ Constitution and Health from 1985‐2010. Subjects were 7‐18‐year‐old students randomly selected from urban and rural areas in 30 provinces. Eight subgroups were created according to region and socioeconomic status. Results Increased rates of the epidemic （overweight and obesity combined） were greatest in large coastal cities‐32.6% and 19.1% among males and females, respectively. These rates has neared that of developed countries. Similar increases were found in all other regions, including the once poverty‐stricken rural west. The epidemic in most of the rural areas began after 2000, but has spread swiftly over the last decade. In 2010, it was estimated that 9.9% of Chinese school‐aged children and adolescents were overweight and that an additional 5.1% were obese, representing an estimated 30.43 million individuals. Conclusion The prognosis for China＇s childhood‐obesity epidemic is dire. To prevent childhood obesity, we suggest several strategies, including reasonable dietary intake, increase physical activity, a change in sedentary lifestyles and corresponding behavioral modifications.展开更多
A comprehensive analysis on the change of the total grain production and the temporal and spatial change of three main crops production（including wheat,maize and rice）,as well as the transfer trace of the center gra...A comprehensive analysis on the change of the total grain production and the temporal and spatial change of three main crops production（including wheat,maize and rice）,as well as the transfer trace of the center gravity of grain production in China were analyzed to reveal the overall developing trend of the grain production,explore the reasons and finally propose the corresponding suggestions and strategies to cope with the situation.展开更多
Vegetation response to the combined effects of human and nature has raised extensive controversy.The relative contributions of ecological restoration and multiple climate factors on vegetation variation remain unclear...Vegetation response to the combined effects of human and nature has raised extensive controversy.The relative contributions of ecological restoration and multiple climate factors on vegetation variation remain unclear.Combining spatial and temporal changes in fractional vegetation cover(FVC)and net primary productivity(NPP)from 2000 to 2021,we assessed the trend of these two indicators and quantified the impact of ecological restoration and climate factors on vegetation variation using partial correlation and residual analysis.The results indicated that:(1)From 2000 to 2021,vegetation restoration in the Taihang Mountain area was notably successful.FVC increased by 5.71%over 22 years with a change trend of 0.0018 per annum.The cumulative growth rate of NPP over the same period was 42.03%,corresponding to an average annual increase of 5.492 g(C)·m^(-2)·a^(-1).(2)During the 22-year period,the contribution rates of ecological engineering to FVC and NPP were 65.13%and 64.33%,respectively.Ecological restoration was the dominant factor affecting vegetation change,and its impact was increasing in over 90%of the regional projects.The primary climate controlling factor of NPP was precipitation,while FVC responded synergistically to precipitation(primary)and temperature(secondary).Overall,the impact of precipitation on vegetation was 1.5 times that of temperature.(3)Among various ecological restoration types,grassland restoration contributed the most to vegetation change,followed by forest land restoration.This study offers valuable scientific insights that can guide the sustainability of vegetation ecology in semi-arid mountainous areas.展开更多
Climate change and human activity have resulted in increasing change of vegetation growth globally. Numerous studies have been conducted on extreme climate events and analyses of ecological environment evolution. Howe...Climate change and human activity have resulted in increasing change of vegetation growth globally. Numerous studies have been conducted on extreme climate events and analyses of ecological environment evolution. However, such studies have placed little emphasis on vegetation change and spatial variation in this type of ecotone. Accordingly, this study analyzed the changes in vegetation type and growth using the 16-d composite MOD13A1 product with 1-km resolution and MOD12Q1 product with 1-km resolution. We used the mean, maximum, standard deviation normalized-difference vegetation index（NDVI） values, and the rate of change（ROC） of NDVI value to explain vegetation changes within the studied ecotone. Our results showed that significant vegetation type and growth changes have occurred in the study area. From 2001 to 2013, for example, with the exception of 2001, 2004 and 2009, a certain extent of grassland area was converted to cropland. Drought severity index（DSI） results indicate that there exists drought in 2001, 2004 and 2009. Such temporal changes in cropland and grassland area confirmed the ecological vulnerability of the ecotone. At the same time, vegetation varied spatially from west to east and from south to north. The mean, maximum and standard deviation NDVI values were all sorted in descending order based on differences in latitude and longitude, as follows： NDVI_（2013）〉NDVI_（2009）〉NDVI_（2004）〉NDVI_（2001）展开更多
文摘BACKGROUND Gastric bezoars are masses of indigestible material that accumulate in the stomach,causing nausea,abdominal pain,and vomiting.Persimmon bezoars(diospyrobezoars),which comprise tannins and fibers from persimmons,are relatively rare but may cause significant gastric complications,including gastric outlet obstruction or ileus.Although computed tomography(CT)is a useful ima-ging tool,diagnosing bezoars can be challenging because their density is similar to that of food debris and gastric content.CASE SUMMARY Here,we report the case of a 72-year-old woman with a persimmon bezoar that was diagnosed using serial CT imaging and confirmed by endoscopy.CT perfor-med over several months revealed changes in the internal structure and density of the bezoar,suggesting progressive hardening.The patient had a history of a par-tial gastrectomy and excessive persimmon consumption,both of which are risk factors for bezoar formation.Endoscopic fragmentation of the bezoar successfully resolved symptoms.CONCLUSION Gastric bezoars,particularly persimmon bezoars,present diagnostic challenges because of their variable imaging characteristics.Serial CT can document tem-poral changes in bezoar density,potentially reflecting changes in hardness.Early diagnosis and endoscopic treatment are essential for effective management,particularly in patients with predisposing factors.This case underscores the im-portance of considering bezoars in the differential diagnosis of gastric masses,and highlights the value of CT for monitoring changes in bezoar characteristics over time.
基金supported by the Research Fund for the Doctoral Program of Higher Education of China(No.20130101110127)the Project of Zhejiang Key Scientific and Technological Innovation Team(No.2010R50039),China
文摘It is important to understand the effects of temporal changes in microbial communities in the acidic soils of tea orchards with different fertilizers. A field experiment involving organic fertilizer （OF）, chemical fertilizer （CF）, and unfertilized control （CK） treatments was arranged to analyze the temporal changes in the bacterial and archaeal communities at bimonthly intervals based on the 16S ribosomal RNA （rRNA） gene using terminal restriction fragment length polymorphism （T-RFLP） profiling. The abundances of total bacteria, total archaea, and selected functional genes （bacterial and archaeal amoA, bacterial narG, nirK, nirS, and nosZ） were determined by quantitative poly- merase chain reaction （qPCR）. The results indicate that the structures of bacterial and archaeal communities varied significantly with time and fertilization based on changes in the relative abundance of dominant T-RFs. The abundancy of the detected genes changed with time. The total bacteria, total archaea, and archaeal amoA were less abundant in July. The bacterial amoA and denitrifying genes were less abundant in September, except the nirK gene. The OF treatment increased the abundance of the observed genes, while the CF treatment had little influence on them. The soil temperature significantly affected the bacterial and archaeal community structures. The soil moisture was signif- icantly correlated with the abundance of denitrifying genes. Of the soil chemical properties, soil organic carbon was the most important factor and was significantly correlated with the abundance of the detected genes, except the nirK gene. Overall, this study demonstrated the effects of both temporal alteration and organic fertilizer on the structures of mi- crobial communities and the abundance of genes involved in the nitrogen cycle.
基金Under the auspices of the Domestic Research Fellowship of the Japan Foundation of Public Communication on Scienceand Technology (No. H-3)
文摘By studying the county-level census data of 1990 and 2000, we analyzed the spatial and temporal changes in the floating population in China between 1990 and 2000. The results of the analysis revealed the following characteris- tics. First, the spatial distribution of the migrants (referred to as 'floaters' in this paper) became increasingly concentrated in the cities during the 1990s. Second, the number of floaters increased rapidly during this period, and the area in which the floaters settled expanded quickly into four population explosion belts: the coast, the Changjiang River Delta, the Beijing-Guangzhou Railway and national border belts. Third, the number of inter-province floaters increased rapidly and exceeded that of intra-province floaters in the 1990s. In addition, to obtain a quantitative relationship between the number of floaters and 10 socio-economic variables by using statistical methods and also to find the chiefly important pulling factors of the migration destination, the authors selected approximately 100 cities with the largest population of floaters. Consequently, we found that four factors-GDP, passenger trips per 10,000 persons, per capita GDP and foreign direct investment-could provide an explanation for 83.7% of the number of floaters in 2000. The GDP showed the highest correlation with the number of floaters, suggesting that a highly developed economy is the most important factor that attracts floaters. Furthermore, a fairly close relationship between the number of floaters and the GDP was also found in 2000 for all the counties.
基金funded in part by the National Science Foundation of United States under grants EAR-0710959 and EAR-0956051support of U.S. Air Force Research Laboratory under grant FA8718-07-186 C-0005 and Dr. Peter Gerstoft
文摘Detecting temporal changes in fault zone properties at seismogenic depth have been a long-sought goal in the seismological community for many decades. Recent studies based on waveform analysis of repeating earthquakes have found clear temporal changes in the shallow crust and around active fault zones associated with the occurrences of large nearby and teleseismic earthquakes. However, repeating earthquakes only occur in certain locations and their occurrence times cannot be controlled, which may result in inadequate sampling of the interested regions or time periods. Recent developments in passive imaging via auto- and cross-correlation of ambient seismic wavefields （e.g., seismic noise, earthquake coda waves） provide an ideal source for continuous monitoring of temporal changes around active fault zones. Here we conduct a systematic search of temporal changes along the Parkfield section of the San Andreas fault by cross-correlating relatively high-frequency （0.4-1.3 Hz） ambient noise signals recorded by 10 borehole stations in the High Resolution Seismic Network. After using stretch/compressed method to measure the delay time and the decorrelation-index between the daily noise cross-correlation functions （NCCFs）, we find clear temporal changes in the median seismic velocity and decorrelation-index associated with the 2004 M6.0 Parkfield earthquake. We also apply the same procedure to the seismic data around five regional/teleseismic events that have triggered non-volcanic tremor in the same region, but failed to find any clear temporal changes in the daily NCCFs. The fact that our current technique can detect temporal changes from the nearby but not regional and teleseismic events, suggests that temporal changes associated with distance sources are very subtle or localized so that they could not be detected within the resolution of the current technique （-0.2%）.
基金Supported by Climate Changes in Chinese Meteorological Bureau(CCSF2011-26)Ningxia Science and Technology Development(KGX12-09-02)Ningxia Natural Science Fund(NZ11246)and(NZ10212)
文摘[Objective]The aim was to study the spatial and temporal changes of extreme precipitation events in Ningxia in recent 50 years.[Method]Using dally precipitation data at 20 stations in Ningxia from 1961 to 2010,and defining the threshold value of extreme precipitation in each sta-tion by percentage method,choosing indicators such as precipitation,frequency and intensity of extreme precipitation events,the characteristics of the spatial and temporal distribution and linear trend of extreme precipitation events in Ningxia were analyzed based on linear regression and M-K non-parameter statistical test method.[Result]The percentage method suggested the threshold value of average extreme precipitation in Ningxia in recent 50 years decreased from south to north.The large threshold value was in southern Haiyuan,Tongxin and northern Yancheng,which was similar to the distribution of mean annual precipitation in Ningxia.In recent 50 years,extreme precipitation frequency and extreme precipitation de-creased in most part of Ningxia but the intensity tended to strengthen.Study of extreme precipitation in Mahuang Mountain and Liupan Mountain in-dicated that precipitation frequency,intensity and extreme precipitation reduced.Annual extreme precipitation frequency narrowed and then in-creased after 1994 and had mutation in 2003.Annual extreme precipitation intensity enhanced since 1984.Mutation took place in 1984.Intensity in Liupan Mountain had weakened since 1978.[Conclusion]The study provided theoretical basis for the mutation of climate in Ningxia.
基金Under the auspices of the National Key Research and Development Program of China(No.2016YFC050040106,2016YFA060230302)the National Science Foundation of China(No.41671087,41671081,41471081)the Technological Basic Research Program of China(No.2013FY111800)
文摘Wetlands on the Qinghai-Tibetan Plateau （QTP） perform a dazzling array of vital ecological functions and are one of the most fragile ecosystems in the world. Timely and accurate information describing wetland resources and their changes over time is becoming more important in their protection and conservation. By using remote sensing data, this study intended to investigate spatial distribution and temporal variations of wetlands on the QTP at different watershed scales from 1970s to 2010s. Results show that wetlands on the QTP have undergone widespread degradation from 1970s to 2010s, with nearly 6.4% of their area being lost. Areas of freshwater marsh, salt marsh and wet meadow declined by 46.6%, 53.9% and 15.6%, respectively, while lake area increased by 14.6%. The most extensive losses of natural wet/ands have occurred in endorheic basins, such as in the Kunlun-Altun-Qilian Drainage Basin and Qiangtang Basin, which shrank by 44.5% and 33.1%, respectively. A pronounced increase in temperature tends to facilitate the evaporation process and reduce water availability for wetlands, One-third of the wetlands on the QTP are under threat of being submerged due to lakes rising in recent years. More research is needed to gain insight into the interaction mechanisms behind observed variations and potential impacts from further warming in the future.
文摘Forest structure changes continuously by natural and anthropogenic effects. Because the level of goods and services provided by forest ecosystems are related to this structure, some attributes have to be controlled while they are being managed. In this paper we describe the long-term temporal changes in land area and landscape metrics related to different land uses of a managed forest in Turkey. The study was carried out for the Daday Forest Planning Unit located in the west Black Sea region of northern Turkey. The total area is 16,813 ha and besides wood production, it is managed for erosion control, public health, aesthetics, and recreation. Stand type maps that were constructed in 1970,1989, 1999, and 2010 were used in this analysis. Transition matrixes that illustrate area changes among cover types and temporal changes on some landscape metrics were obtained using Geographic Information Systems. Stands were separated into small patches, and thus the number of patches increased nearly two-fold between 1970 and 2010. The total forest edge increased and through the associated fragmentation, the amount of core forest area decreased at the landscape scale. Landscape metrics were applied to digitized versions of historical maps to assess how forest area changed. Human use of the land has changed, forest management practices have evolved, and these along with natural forest growth have contributed to interesting changes in landscape character.
文摘In order to understand the temporal changes of botanical composition in grassland ecosystem, and to clarify the relation between these changes and environmental impacts, such as climatic factors and artificial disturbance, a grazing trail was carried out during a 21-year period from 1974 at a sown grassland of the National Grassland Research Institute, located in Nishinasuno, the central area of Japan. The data sets of biomass for each mouth(from April to November)of the 21 year period were analyzed in this paper. The botanical composition of aboveground biomass varied greatly with both season and year. The biomass ratio of improved herbage species to invaded native plants gradually decreased each year. This may have been owing to meteorological factors, such as low air-temperature in winter, dry and hot summers, grassland management(including grazing intensity and fertilizer application), and inter-specific competition between native and introduced herbage plants.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2021QZKK0202)Shaanxi Provincial Youth Science and Technology Rising Star Project(No.2022KJXX-85)+3 种基金Key Scientific Research Project of Shaanxi Provincial Department of Education(No.22JS041)Youth Innovation Team Research Project of Shaanxi Provincial Department of Education(Nos.22JP099,21JP137)The Youth Innovation Team of Shaanxi Universitiesthe Support Program for Outstanding Young Talents of Shaanxi Universities(Dr.Tao Luo)。
文摘Freezing–thawing indices serve as a comprehensive indicator of both the duration of the freezing/thawing periods and the degree of cold and heat in a given region.In-depth analysis of the freezing-thawing indices not only enables the prediction of permafrost distribution and its dynamic changes,but also facilitates the assessment of damage risk to infrastructure under freeze-thaw action.In this paper,the air/ground freezing–thawing indices from 1987 to 2017,based on daily temperature observations from meteorological stations along the China–Nepal Highway(CNH),were calculated,and their spatial and temporal variation patterns were analyzed.The results showed that:(1)Both mean annual air temperature and mean annual ground surface temperature along the CNH fluctuated upward,with climate tendency rates of 0.43 and 0.52.C·(10a)~(-1),respectively;(2)The number of days with negative air temperature and ground temperature showed fluctuated downward,with change rates of-8.6 and-8.3 d·(10a)~(-1),respectively;(3)The ranges of air freezing index,air thawing index,ground freezing index,and ground thawing index over the years were 157.05-458.88°C·d,2034.20-2560.73°C·d,108.78-396.83°C·d,and 3515.25-4288.67°C·d,respectively.The climate tendency rates were-5.42,10.22,-6.79,and 12.14.C·d·a-1,respectively,showing a general warming trend;(4)The air freezing index,ground freezing index,and ground thawing index changed abruptly in 1999,2000,and 2002,respectively,evincing significant changes after 2002.The research results can provide a basis for the risk assessment of freezing–thawing erosion and the prevention and control of permafrost engineering diseases along the CNH.
基金National Natural Science Foundation of China.No.40276027No.40231010Shanghai Priority Academic Discipline
文摘A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion of the hydrodynamic regimes of the estuary. Spatially, the SSC from Xuliujing downwards to Hangzhou Bay increases almost constantly, and the suspended sediment in the inner estuary shows higher concentration in summer than in winter, while in the outer estuary it shows higher concentration in winter than in summer, and the magnitude is greater in the outer estuary than in the inner estuary, greater in the Hangzhou Bay than in the Yangtze River estuary. The sediments discharged by the Yangtze River into the sea are resuspended by marine dynamics included tidal currents and wind waves. Temporally, the SSC shows a pronounced neap-spring tidal cycle and seasonal variations. Furthermore, through the analysis of dynamic mechanism, it is concluded that wave and tidal current are two predominant factors of sediment resuspension and control the distribution and changes of SSC, in which tidal currents control neap-spring tidal cycles, and wind waves control seasonal variations. The ratio between river discharge and marine dynamics controls spatial distribution of SSC.
基金the Chinese Universities Scientific Fund(2015SYL004).
文摘Algal blooms have become a worldwide environmental concern due to water eutrophication.Dianchi Lake in Yunnan Province,China is suffering from severe eutrophication and is listed in the Three Important Lakes Restoration Act of China.Hydrothermal liquefaction allows a promising and direct conversion of algal biomass into biocrude oil.In this study,algal samples were collected from Dianchi Lake after a separation procedure including dissolved air flotation with polyaluminum chloride and centrifugation during four months,April,June,August and October.The algal biochemical components varied over the period;lipids from 0.7%to 2.1%ash-free dry weight(afdw),protein from 20.9%to 33.4%afdw and ash from 36.6%to 45.2%dry weight.The algae in June had the highest lipid and protein concentrations,leading to a maximum biocrude oil yield of 24.3%afdw.Biodiversity analysis using pyrosequencing revealed different distributions of microbial communities,specifically Microcystis in April(89.0%),June(63.7%)and August(84.0%),and Synechococcus in April(2.2%),June(12.0%)and August(1.0%).This study demonstrated remarkable temporal changes in the biochemical composition and biodiversity of algae harvested from Dianchi Lake and changes in biocrude oil production potential.
文摘This paper takes poverty-stricken countyas the basic unit, and selects net income per peasantto study the poverty status in Hebei Province during1986~2000.Temporal and spatial changes of poverty-stricken areas are analyzed. The result shows thatpoverty-stricken areas in Hebei Province distributedconcentratedly and the areas decreased during1986~2000, the net income per peasant was on therise with an increasing speed in off-poverty countiesbeing slightly higher than that in poverty-strickencounties, but the growth rate was extremely unstable,rising slowly in off-poverty counties while droppingin poverty-stricken counties. The main driving forcesthat influenced temporal and spatial changes wereeconomic development of the whole province,ecological environment quality, infrastructureconditions and radiation of the key city. On thisbasis, some anti-poverty countermeasures suitable tolocal conditions are proposed.
文摘Affected by topographical conditions,the distribution of cultivated land in karst areas is relatively fragmented.More effective cultivated land protection measures can be taken in a targeted manner by grasping the spatial and temporal distribution characteristics of regional cultivated land.In this study,with the cultivated land of four county-level administrative regions(Debao County,Jingxi City,Daxin County,and Tiancheng County)in typical karst landform areas in southwestern Guangxi as the research object,combining with the spatial analysis function of the GIS software platform,the spatial distribution characteristics and temporal and spatial changes of cultivated land in the study area were investigated from 2009 to 2020 using the quantitative analysis method of landscape pattern indices,revealing the main problems of cultivated land utilization,and the multi-dimensional management ideas of cultivated land protection in karst areas under the background of rural revitalization strategy were proposed.
基金Supported by the International Partnership Program of Chinese Academy of Sciences(No.313GJHZ2022085 FN)the Dragon 5 Cooperation(No.59193)。
文摘Rapidly monitoring regional water quality and the changing trend is of great practical and scientific significance,especially for the Beijing-Tianjin-Hebei(BTH)region of China where water resources are relatively scarce and inland water bodies are generally small.The remote sensing data of the GF 1 satellite launched in 2013 have characteristics of high spatial and temporal resolution,which can be used for the dynamic monitoring of the water environment in small lakes and reservoirs.However,the water quality remote sensing monitoring model based on the GF 1 satellite data for lakes and reservoirs in BTH is still lacking because of the considerable differences in the optical characteristics of the lakes and reservoirs.In this paper,the typical reservoirs in BTH-Guanting Reservoir,Yuqiao Reservoir,Panjiakou Reservoir,and Daheiting Reservoir are taken as the study areas.In the atmospheric correction of GF 1-WFV,the relative radiation normalized atmospheric correction was adopted after comparing it with other methods,such as 6 S and FLAASH.In the water clarity retrieval,a water color hue angle based model was proposed and outperformed other available published models,with the R 2 of 0.74 and MRE of 31.7%.The clarity products of the four typical reservoirs in the BTH region in 2013-2019 were produced using the GF 1-WFV data.Based on the products,temporal and spatial changes in clarity were analyzed,and the main influencing factors for each water body were discussed.It was found that the clarity of Guanting,Daheiting,and Panjiakou reservoirs showed an upward trend during this period,while that of Yuqiao Reservoir showed a downward trend.In the influencing factors,the water level of the water bodies can be an important factor related to the water clarity changes in this region.
文摘Birdsong is an important secondary sexual trait which may vary between but also within species.Intraspecific variation is generally studied either on the geographical or on the temporal scale;most of the studies exploring the variation of song over time,however,focused on species with rather simple songs.In this study,we explored the temporal changes in song of a complex songster,the Thrush Nightingale(Luscinia luscinia),recorded after 33 years(in 1986 and 2019)at the same locality in south-eastern Finland.Our analysis revealed a complete turnover of song types over the study period,with no song type shared between the two recording years.In contrast,40%of the originally recorded syllable types were still found in the repertoires of recently recorded males.Their song type repertoires were significantly smaller but the songs themselves were on average longer compared to the 1986 recordings.Repertoires of both syllables and song types were more shared between males recorded in 1986 than between those from 2019.We discuss the processes that may have contributed to these temporal changes in song and call for more detailed studies of song evolution in wild populations.
基金Supported by the National Key Research and Development Program of China(2022YFC2503101)the National Natural Science Foundation of China(82273749 and 82473747).
文摘Introduction:Coal-burning pollution type of endemic fluorosis remains a significant public health threat in certain rural areas of China.This study aimed to analyze the long-term trends in dental fluorosis prevalence in coal-burning fluorosis areas in China from 2009 to 2023.Methods:We collected and analyzed dental fluorosis detection rates among children aged 8–12 in 12 coalburning fluorosis provincial-level administrative divisions(PLADs)of China(2009–2023).The optimal Autoregressive Integrated Moving Average with Exogenous Inputs(ARIMAX)time series model was used to predict dental fluorosis detection rates in children from 2019 to 2023.The GeoDa(version 1.20.0;GeoDa Institute)software was employed for spatial analysis,while the SaTScan(version 10.1;GeoDa Institute)was used to analyze spatial-temporal aggregation patterns.Results:From 2009 to 2023,the dental fluorosis detection rates in children aged 8–12 years showed a decreasing trend,declining from 49.51%to 1.56%.After 2016,achieving the elimination standard(<15%).There was a goodagreement between the observed detection rates andexpected values,with a relative risk(RR)of 0.98.Global analysis shows that the detection rate of dental fluorosis is randomly dispersed.The Moran’s I index for dental fluorosis detection rates was positive in 2009,2011,and 2013,and negative in other years,with Z-values ranging from−1.53 to 0.99.Local analysis indicates that Yunnan Province has continuously presented a low-high aggregation pattern from 2011 to 2013.Space-time analysis identified that Yunnan was classified as a highprevalence cluster in 2022–2023[odds ratio(OR)=1.07,Log likelihood ratio(LLR)=30.45,P<0.05].Conclusions:China has achieved remarkable success in the prevention and control of coal-burning fluorosis.These spatial findings provide critical reference values to support targeted prevention strategies for coalburning fluorosis.
文摘Objective To determine the extent of the obesity epidemic in school‐aged Chinese children in 2010 and track the increasing trend in different socioeconomic regions over the preceding 25 years. Strategies for preventing childhood obesity are suggested. Methods We used a dataset provided by the Chinese National Survey on Students’ Constitution and Health from 1985‐2010. Subjects were 7‐18‐year‐old students randomly selected from urban and rural areas in 30 provinces. Eight subgroups were created according to region and socioeconomic status. Results Increased rates of the epidemic （overweight and obesity combined） were greatest in large coastal cities‐32.6% and 19.1% among males and females, respectively. These rates has neared that of developed countries. Similar increases were found in all other regions, including the once poverty‐stricken rural west. The epidemic in most of the rural areas began after 2000, but has spread swiftly over the last decade. In 2010, it was estimated that 9.9% of Chinese school‐aged children and adolescents were overweight and that an additional 5.1% were obese, representing an estimated 30.43 million individuals. Conclusion The prognosis for China＇s childhood‐obesity epidemic is dire. To prevent childhood obesity, we suggest several strategies, including reasonable dietary intake, increase physical activity, a change in sedentary lifestyles and corresponding behavioral modifications.
基金Supported by National Scientific and Technological Supporting Project(2006BAD20B05)~~
文摘A comprehensive analysis on the change of the total grain production and the temporal and spatial change of three main crops production（including wheat,maize and rice）,as well as the transfer trace of the center gravity of grain production in China were analyzed to reveal the overall developing trend of the grain production,explore the reasons and finally propose the corresponding suggestions and strategies to cope with the situation.
基金supported by the National Natural Science Foundation of China(No.41930651 and 41807013)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2020102)。
文摘Vegetation response to the combined effects of human and nature has raised extensive controversy.The relative contributions of ecological restoration and multiple climate factors on vegetation variation remain unclear.Combining spatial and temporal changes in fractional vegetation cover(FVC)and net primary productivity(NPP)from 2000 to 2021,we assessed the trend of these two indicators and quantified the impact of ecological restoration and climate factors on vegetation variation using partial correlation and residual analysis.The results indicated that:(1)From 2000 to 2021,vegetation restoration in the Taihang Mountain area was notably successful.FVC increased by 5.71%over 22 years with a change trend of 0.0018 per annum.The cumulative growth rate of NPP over the same period was 42.03%,corresponding to an average annual increase of 5.492 g(C)·m^(-2)·a^(-1).(2)During the 22-year period,the contribution rates of ecological engineering to FVC and NPP were 65.13%and 64.33%,respectively.Ecological restoration was the dominant factor affecting vegetation change,and its impact was increasing in over 90%of the regional projects.The primary climate controlling factor of NPP was precipitation,while FVC responded synergistically to precipitation(primary)and temperature(secondary).Overall,the impact of precipitation on vegetation was 1.5 times that of temperature.(3)Among various ecological restoration types,grassland restoration contributed the most to vegetation change,followed by forest land restoration.This study offers valuable scientific insights that can guide the sustainability of vegetation ecology in semi-arid mountainous areas.
基金funded by the National Basic Research Program of China (973 Program, 2014CB954301)the Project of the State Key Laboratory of Earth Surface Processes and Resources Ecology, Beijing Normal University, China (2013-KF-11)the Project of Ministry of Environmental Protection of China (257228006)
文摘Climate change and human activity have resulted in increasing change of vegetation growth globally. Numerous studies have been conducted on extreme climate events and analyses of ecological environment evolution. However, such studies have placed little emphasis on vegetation change and spatial variation in this type of ecotone. Accordingly, this study analyzed the changes in vegetation type and growth using the 16-d composite MOD13A1 product with 1-km resolution and MOD12Q1 product with 1-km resolution. We used the mean, maximum, standard deviation normalized-difference vegetation index（NDVI） values, and the rate of change（ROC） of NDVI value to explain vegetation changes within the studied ecotone. Our results showed that significant vegetation type and growth changes have occurred in the study area. From 2001 to 2013, for example, with the exception of 2001, 2004 and 2009, a certain extent of grassland area was converted to cropland. Drought severity index（DSI） results indicate that there exists drought in 2001, 2004 and 2009. Such temporal changes in cropland and grassland area confirmed the ecological vulnerability of the ecotone. At the same time, vegetation varied spatially from west to east and from south to north. The mean, maximum and standard deviation NDVI values were all sorted in descending order based on differences in latitude and longitude, as follows： NDVI_（2013）〉NDVI_（2009）〉NDVI_（2004）〉NDVI_（2001）
