Anthropogenic activities have become more and more important in characterizing the landscape, but their impacts are still restricted by natural environments. This paper discusses the interactions of anthropogenic acti...Anthropogenic activities have become more and more important in characterizing the landscape, but their impacts are still restricted by natural environments. This paper discusses the interactions of anthropogenic activity, vegetation activity and topography through describing the spatial distribution of land cover and vegetation activity (represented by Normalized Difference Vegetation Index, NDVI) along topographic gradient in a mountainous area of southwestern China. Our results indicate that the existing landscape pattern is controlled by anthropogenic activities as well as topographic factors. Intensive anthropogenic activities mainly occur in areas with relatively low elevation, gentle and concave slopes, as these areas are easy and convenient to attain for human. Because of the destruction by human, some land cover types (mainly grassland and shrub) are only found in relatively harsher environments. This study also finds that topographic wetness index (W) used in other places only reflects runoff generation capacity, but not indicate the real spatial pattern of soil water content in this area. The relationships between NDVI and W, and NDVI and length slope factor (LSF) show that runoff and erosion have complex effects on vegetation activity. Greater values of W and LSF will lead to stronger capacity to produce runoff and transport sediment, and thereby increase soil water content and soil deposition, whereas beyond a certain threshold runoff and erosion are so strong that they would destruct vegetation growth. This study provides information needed to successfully restore native vegetation, improve land management, and promote sustainable development in mountainous areas, especially for developing regions.展开更多
Variations in vegetation activity during the past 18 years in China were investigated using the normalized difference vegetation index (NDVI) derived from the 3rd generation time series dataset of NOAA-AVHRR from 1982...Variations in vegetation activity during the past 18 years in China were investigated using the normalized difference vegetation index (NDVI) derived from the 3rd generation time series dataset of NOAA-AVHRR from 1982 to 1999. In order to eliminate the effects of non-vegetation factors, we characterized areas with NDVI < 0.1 as sparsely vegetated areas and areas with NDVI ≥ 0.1 as vegetated areas. The results showed that increasing NDVI trends were evident, to varying extents, in almost all regions in China in the 18 years, indicating that vegetation activity has been rising in recent years in these regions. Compared to the early 1980s, the vegetated area increased by 3.5% by the late 1990s, while the sparsely vegetated area declined by 18.1% in the same period. The national total mean annual NDVI increased by 7.4% during the study period. Extended growing seasons and increased plant growth rates ac-counted for the bulk of these increases, while increases in temperature and summer rainfall, and strengthening agricultural activity were also likely important factors. NDVI changes in China ex-hibited relatively large spatial heterogeneity; the eastern coastal regions experienced declining or indiscernibly rising trends, while agricultural regions and western China experienced marked increases. Such a pattern was due primarily to urbanization, agricultural activity, regional climate characteristics, and different vegetation responses to regional climate changes.展开更多
Terrestrial vegetation is one of the most important components of the Earth's land surface. Variations in terrestrial vegetation directly impact the Earth system's balance of material and energy. This paper de...Terrestrial vegetation is one of the most important components of the Earth's land surface. Variations in terrestrial vegetation directly impact the Earth system's balance of material and energy. This paper describes detected variations in vegetation activity at a national scale for China based on nearly 30 years of remote sensing data derived from NOAA/AVHRR(1982–2006) and MODIS(2001–2009). Vegetation activity is analyzed for four regions covering agriculture, forests, grasslands, and China's Northwest region with sparse vegetation cover(including regions without vegetation). Relationships between variations in vegetation activity and climate change as well as agricultural production are also explored. The results show that vegetation activity has generally increased across large areas, especially during the most recent decade. The variations in vegetation activity have been driven primarily by human factors, especially in the southern forest region and the Northwest region with sparse vegetation cover. The results further show that the variations in vegetation activity have influenced agricultural production, but with a certain time lag.展开更多
The Chinese government adopted six ecological restoration programs to improve its natural environments. Although these programs have proven successful in improving local environments, some studies have questioned thei...The Chinese government adopted six ecological restoration programs to improve its natural environments. Although these programs have proven successful in improving local environments, some studies have questioned their performance when regions suffer from drought. Whether we should consider the effects of drought on vegetation change in assessments of the benefits of ecological restoration programs is unclear. Therefore, taking the Grain for Green Program(GGP) region as a study area, we estimated vegetation growth in the region from 2000–2010 to clarify the trends in vegetation and their driving forces. Results showed that: 1) vegetation growth increased in the GGP region during 2000–2010, with 59.4% of the area showing an increase in the Normalized Difference Vegetation Index(NDVI). This confirmed the benefits of the ecological restoration program. 2) Drought can affect the vegetation change trend, but human activity plays a significant role in altering vegetation growth, and the slight downward trend in the NDVI was not consistent with the severity of the drought. Positive human activity led to increased NDVI in 89.13% of areas. Of these, 22.52% suffered drought, but positive human activity offset the damage in part. 3) Results of this research suggest that appropriate human activity can maximize the benefits of ecological restoration programs and minimize the effects of extreme weather. We therefore recommend incorporating eco-risk assessment and scientific management mechanisms in the design and management of ecosystem restoration programs.展开更多
The taiga vegetation in Western Siberia has been seriously threatened by climate warming in recent decades.However,how vegetation in different growing states and climate conditions responds to climate changes differen...The taiga vegetation in Western Siberia has been seriously threatened by climate warming in recent decades.However,how vegetation in different growing states and climate conditions responds to climate changes differently is still unclear.Here we explore the vegetation activity trends in Western Siberia taiga forests using the annual rate of change in leaf area index(LAI)during 1982–2018 so as to answer two questions:(1)how did climate warming affect taiga vegetation activity in the recent last decades?(2)Did the growing state of taiga forest affect its response to climate warming?Our results revealed that climate warming promoted taiga vegetation activity in Western Siberia before 2000.However,continuous warming caused excessive evapotranspiration and led to decreased vegetation activity after 2000.Moreover,the intensity of vegetation growth response to warming was positively related to canopy height and LAI,indicating that both the positive and negative effects of warming were more significant in taiga forests in better growing state.Since these forests generally have higher productivity and play more important roles in ecosystem functioning(e.g.,carbon sink and biodiversity conservation),our results highlight their vulnerability to future climate change that need more research attention.展开更多
The revegetation protection system(VPS)on the edge of the Tengger Desert can be referred to as a successful model of sand control technology in China and even the world,and there has been a substantial amount of resea...The revegetation protection system(VPS)on the edge of the Tengger Desert can be referred to as a successful model of sand control technology in China and even the world,and there has been a substantial amount of research on revegetation stability.However,it is unclear how meso-and micro-scale revegetation activity has responded to climatic change over the past decades.To evaluate the relative influence of climatic variables on revegetation activities in a restored desert ecosystem,we analysed the trend of revegetation change from 2002 to 2015 using a satellite-derived normalized difference vegetation index(NDVI)dataset.The time series of the NDVI data were decomposed into trend,seasonal,and random components using a segmented regression method.The results of the segmented regression model indicate a changing trend in the NDVI in the VPS,changing from a decrease(−7×10−3/month)before 2005 to an increase(0.3×10−3/month)after 2005.We found that precipitation was the most important climatic factor influencing the growing season NDVI(P<0.05),while vegetation growth sensitivity to water and heat varied significantly in different seasons.In the case of precipitation reduction and warming in the study area,the NDVI of the VPS could still maintain an overall slow upward trend(0.04×10−3/month),indicating that the ecosystem is sustainable.Our findings suggest that the VPS has been successful in maintaining stability and sustainability under current climate change conditions and that it is possible to introduce the VPS in similar areas as a template for resistance to sand and drought hazards.展开更多
A series of new aurone derivatives was prepared by means of a practical route and their anti-vascular smooth muscle cells（VSMC） vegetation activities were evaluated by the 3-（4,5-dimethylthlazol-2-yl）-2,5- dipheny...A series of new aurone derivatives was prepared by means of a practical route and their anti-vascular smooth muscle cells（VSMC） vegetation activities were evaluated by the 3-（4,5-dimethylthlazol-2-yl）-2,5- diphenyltetrazolium bromide（MTT） method with tetrandrine as a positive contrast drug. The structures of the com- pounds were confirmed by 1H NMR, 13C NMR and electrospray ionization mass spectrometry（ESI-MS）. Several new compounds exhibited promising activity against VSMC proliferation and the preliminary structure-activity relation- ships（SAR） were discussed in order to investigate the essential structures required for their bioactivities.展开更多
Vegetation greenness is a key indicator of terrestrial vegetation activity. To under- stand the variation in vegetation activity in spring across eastern China （EC）, we analysed the variation in the Normalised Diffe...Vegetation greenness is a key indicator of terrestrial vegetation activity. To under- stand the variation in vegetation activity in spring across eastern China （EC）, we analysed the variation in the Normalised Difference Vegetation Index （NDVI） from April to May during 1982-2006. The regional mean NDVI across EC increased at the rate of 0.02/10yr （P=0.28; p=0.024） prior to 1998; the increase ceased, and the NDVI dropped to a low level thereafter. However, the processes of variation in the NDVI were different from one region to another. In the North China Plain, a cultivated area, the NDVI increased （0.03/10yr; f2=0.52; p〈0.001） from 1982 to 2006. In contrast, the NDVI decreased （-0.02/10yr; P=0.24; p=0.014） consecu- tively from 1982 to 2006 in the Yangtze River and Pearl River deltas, two regions of rapid urbanisation. In the eastern region of the Inner Mongolian Plateau and the lower reaches of the Yangtze River in East China, the NDVI increased prior to 1998 and decreased thereafter. In the Hulun Buir area and the southern part of the Yangtze River Basin, the NDVI increased prior to 1998 and remained static thereafter. The NDVI in the grasslands and croplands in the semi-humid and semi-arid areas showed a significant positive correlation with precipitation, while the NDVI in the woodlands in the humid to semi-humid areas showed a significant positive correlation with temperature. As much as 60% of the variation in the NDVI was explained by either precipitation or temperature.展开更多
The Changbai Mountains and the Appalachian Mountains have similar spatial contexts.The elevation,latitude,and moisture gradients of both mountain ranges offer regional insight for investigating the vegetation dynamics...The Changbai Mountains and the Appalachian Mountains have similar spatial contexts.The elevation,latitude,and moisture gradients of both mountain ranges offer regional insight for investigating the vegetation dynamics in eastern Eurasia and eastern North America.We determined and compared the spatial patterns and temporal trends in the normalized difference vegetation index(NDVI)in the Changbai Mountains and the Appalachian Mountains using time series data from the Global Inventory Modeling and Mapping Studies 3^(rd) generation dataset from 1982 to 2013.The spatial pattern of NDVI in the Changbai Mountains exhibited fragmentation,whereas NDVI in the Appalachian Mountains decreased from south to north.The vegetation dynamics in the Changbai Mountains had an insignificant trend at the regional scale,whereas the dynamics in the Appalachian Mountains had a significant increasing trend.NDVI increased in 55% of the area of the Changbai Mountains and in 95% of the area of the Appalachian Mountains.The peak NDVI occurred one month later in the Changbai Mountains than in the Appalachian Mountains.The results revealed a significant increase in NDVI in autumn in both mountain ranges.The climatic trend in the Changbai Mountains included warming and decreased precipitation,and whereas that in the Appalachian Mountains included significant warming and increased precipitation.Positive and negative correlations existed between NDVI and temperature and precipitation,respectively,in both mountain ranges.Particularly,the spring temperature and NDVI exhibited a significant positive correlation in both mountain ranges.The results of this study suggest that human actives caused the differences in the spatial patterns of NDVI and that various characteristics of climate change and intensity of human actives dominated the differences in the NDVI trends between the Changbai Mountains and the Appalachian Mountains.Additionally,the vegetation dynamics of both mountain ranges were not identical to those in previous broader-scale studies.展开更多
Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities.Since the 1980s,climate has been warming on the Tibetan Plateau(TP)at a rate higher than North Hemisphere average.An...Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities.Since the 1980s,climate has been warming on the Tibetan Plateau(TP)at a rate higher than North Hemisphere average.Anthropogenic activities,including grazing,farming,and urbanization,are also influencing the alpine ecosystem on the TP.Especially,an ensemble of large engineering projects,such as power transported from west to east by State Grid,has been in operation on the TP.While studies disentangling effects of climate and anthropogenic activities interference are still lacking for the forest ecosystems on the TP.The overarching objectives of this study were to separate effects of natural climates and human interferences on forest ecosystem dynamics on the TP.Methods We compared vegetation activities of two typical natural reserves(Gongbu natural reserve,GNR,and Yarlung zangbo river grand canyon natural reserve,YNR)and their surroundings in southeastern Tibet(outside of the natural reserves,ONR)using long-term satel-lite normalized difference vegetation index(NDVI)dataset.Linear regression and partial correlation analyses were constructed for the relationship between vegetation activity and climates to evaluate the distinct climate effects on the two natural reserves.Important Findings The two natural reserves were established at different time,which were related to anthropogenic activities impact durations.The results showed that the annual mean NDVI fluctuated between 0.5 and 0.6 in the relatively longer reserved YNR,which was re-markably higher than those in other regions(with NDVI lower than 0.45).The vegetation vigor in the YNR showed neither a sig-nificant temporal trend nor significant relationship with climate.Nevertheless,vegetation vigor exhibited a significant increasing trend during the last three decades(0.012/decade)at the GNR.The inter-decadal analysis turned out positive relationships between vegetation vigor and annual temperature since late 1990s until early 2000s when the GNR was officially established.This study underlined the importance of considering human interference duration when assessing the relationships between vegetation dy-namics and climates.展开更多
Objective： To explore the molecular mechanism of puerarin （Pue） in improving insulin resistance through observing its effect on the insulin resistance of 3T3-Li lipocyte induced by free fatty acid （FFA）. Methods...Objective： To explore the molecular mechanism of puerarin （Pue） in improving insulin resistance through observing its effect on the insulin resistance of 3T3-Li lipocyte induced by free fatty acid （FFA）. Methods： 3T3-L1 preadipocyte was induced by a culture solution containing insulin, isobutyo-menthyl-xanthine, and dexamethasone to mature lipocyte, and it was divided into six groups： the control group （normal cells）, the model group （untreated model cells）, and the four drug treatment group exposed to dimethyl biguanide （Met group）, high- dose pueradn （PueH group）, low-dose puerarin （PueL group）, and propylene glycol （PG group）, respectively. Mature lipocytes in various groups, except those in the normal group, were established into insulin resistance model by FFA induction and treated respectively with corresponding drugs. Peroxisome proliferator-activated receptor- γ （PPAR- γ） mRNA expressions at the fourth, sixth, and eighth day were observed using reverse transcription polymerase chain reaction （RT-PCR）; glucose transportation in various groups were observed by 2-deoxy-[3H]-D-glucose intake method; mRNA expression of Cbl binding protein （CAP） was determined by RT-PCR; and glucose transporter-4 （Glut-4） transposition was detected by immune-fluorescence method. Results： PPAR- γmRNA expression increased gradually, and it showed lower levels at the fourth, sixth, and eighth day in all treatment groups than that in the model group. Glucose transportation determination showed that the transportation in the model group was 2.23 ± 0.63, significantly lower than that in the normal group 5.05 ± 0.66 （P〈0.01）; as compared with the model group, they were significantly higher in the PueH and the PueL groups. In addition, the CAP mRNA expression and membranous distribution of Glut-4 were higher in the two Pue treated groups than those in the model group, respectively. Conclusion： Pue could markedly improve the insulin resistance of 3T3-L1 lipocyte, which is realized possibly by way of inactivating CAP path, promoting Glut-4 transposition to cell membrane to increase the transportation of glucose.展开更多
基金the National Natural Science Foundation of China (40621061)the Project of Chinese Academy of Sciences (KZCX2-XB2-02-31) for their financial support
文摘Anthropogenic activities have become more and more important in characterizing the landscape, but their impacts are still restricted by natural environments. This paper discusses the interactions of anthropogenic activity, vegetation activity and topography through describing the spatial distribution of land cover and vegetation activity (represented by Normalized Difference Vegetation Index, NDVI) along topographic gradient in a mountainous area of southwestern China. Our results indicate that the existing landscape pattern is controlled by anthropogenic activities as well as topographic factors. Intensive anthropogenic activities mainly occur in areas with relatively low elevation, gentle and concave slopes, as these areas are easy and convenient to attain for human. Because of the destruction by human, some land cover types (mainly grassland and shrub) are only found in relatively harsher environments. This study also finds that topographic wetness index (W) used in other places only reflects runoff generation capacity, but not indicate the real spatial pattern of soil water content in this area. The relationships between NDVI and W, and NDVI and length slope factor (LSF) show that runoff and erosion have complex effects on vegetation activity. Greater values of W and LSF will lead to stronger capacity to produce runoff and transport sediment, and thereby increase soil water content and soil deposition, whereas beyond a certain threshold runoff and erosion are so strong that they would destruct vegetation growth. This study provides information needed to successfully restore native vegetation, improve land management, and promote sustainable development in mountainous areas, especially for developing regions.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.40024101&90211016).
文摘Variations in vegetation activity during the past 18 years in China were investigated using the normalized difference vegetation index (NDVI) derived from the 3rd generation time series dataset of NOAA-AVHRR from 1982 to 1999. In order to eliminate the effects of non-vegetation factors, we characterized areas with NDVI < 0.1 as sparsely vegetated areas and areas with NDVI ≥ 0.1 as vegetated areas. The results showed that increasing NDVI trends were evident, to varying extents, in almost all regions in China in the 18 years, indicating that vegetation activity has been rising in recent years in these regions. Compared to the early 1980s, the vegetated area increased by 3.5% by the late 1990s, while the sparsely vegetated area declined by 18.1% in the same period. The national total mean annual NDVI increased by 7.4% during the study period. Extended growing seasons and increased plant growth rates ac-counted for the bulk of these increases, while increases in temperature and summer rainfall, and strengthening agricultural activity were also likely important factors. NDVI changes in China ex-hibited relatively large spatial heterogeneity; the eastern coastal regions experienced declining or indiscernibly rising trends, while agricultural regions and western China experienced marked increases. Such a pattern was due primarily to urbanization, agricultural activity, regional climate characteristics, and different vegetation responses to regional climate changes.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences,Climate Change:Carbon Budget and Relevant Issues(Grant No.XDA05050100)
文摘Terrestrial vegetation is one of the most important components of the Earth's land surface. Variations in terrestrial vegetation directly impact the Earth system's balance of material and energy. This paper describes detected variations in vegetation activity at a national scale for China based on nearly 30 years of remote sensing data derived from NOAA/AVHRR(1982–2006) and MODIS(2001–2009). Vegetation activity is analyzed for four regions covering agriculture, forests, grasslands, and China's Northwest region with sparse vegetation cover(including regions without vegetation). Relationships between variations in vegetation activity and climate change as well as agricultural production are also explored. The results show that vegetation activity has generally increased across large areas, especially during the most recent decade. The variations in vegetation activity have been driven primarily by human factors, especially in the southern forest region and the Northwest region with sparse vegetation cover. The results further show that the variations in vegetation activity have influenced agricultural production, but with a certain time lag.
基金Under the auspices of the National Key R&D Program of China(No.2017YFC0504701)Science and Technology Service Network Initiative Project of Chinese Academy of Sciences(No.KFJ-STS-ZDTP-036)+1 种基金Fundamental Research Funds for the Central Universities(No.GK201703053)China Postdoctoral Science Foundation(No.2017M623114)
文摘The Chinese government adopted six ecological restoration programs to improve its natural environments. Although these programs have proven successful in improving local environments, some studies have questioned their performance when regions suffer from drought. Whether we should consider the effects of drought on vegetation change in assessments of the benefits of ecological restoration programs is unclear. Therefore, taking the Grain for Green Program(GGP) region as a study area, we estimated vegetation growth in the region from 2000–2010 to clarify the trends in vegetation and their driving forces. Results showed that: 1) vegetation growth increased in the GGP region during 2000–2010, with 59.4% of the area showing an increase in the Normalized Difference Vegetation Index(NDVI). This confirmed the benefits of the ecological restoration program. 2) Drought can affect the vegetation change trend, but human activity plays a significant role in altering vegetation growth, and the slight downward trend in the NDVI was not consistent with the severity of the drought. Positive human activity led to increased NDVI in 89.13% of areas. Of these, 22.52% suffered drought, but positive human activity offset the damage in part. 3) Results of this research suggest that appropriate human activity can maximize the benefits of ecological restoration programs and minimize the effects of extreme weather. We therefore recommend incorporating eco-risk assessment and scientific management mechanisms in the design and management of ecosystem restoration programs.
基金The Third Xinjiang Scientific Expedition Program,No.2021xjkk0603,No.2022xjkk1205National Natural Science Foundation of China,No.32201258,No.32271652。
文摘The taiga vegetation in Western Siberia has been seriously threatened by climate warming in recent decades.However,how vegetation in different growing states and climate conditions responds to climate changes differently is still unclear.Here we explore the vegetation activity trends in Western Siberia taiga forests using the annual rate of change in leaf area index(LAI)during 1982–2018 so as to answer two questions:(1)how did climate warming affect taiga vegetation activity in the recent last decades?(2)Did the growing state of taiga forest affect its response to climate warming?Our results revealed that climate warming promoted taiga vegetation activity in Western Siberia before 2000.However,continuous warming caused excessive evapotranspiration and led to decreased vegetation activity after 2000.Moreover,the intensity of vegetation growth response to warming was positively related to canopy height and LAI,indicating that both the positive and negative effects of warming were more significant in taiga forests in better growing state.Since these forests generally have higher productivity and play more important roles in ecosystem functioning(e.g.,carbon sink and biodiversity conservation),our results highlight their vulnerability to future climate change that need more research attention.
基金The authors gratefully acknowledge the editor and two anonymous reviewers for valuable comments on the manuscript.We also acknowledge DingHai Zhang for their help in the data analysis.This work was supported by the Funds for Creative Research Groups of China(Grant No.41621001)the National Natural Science Foundation of China(Grant Nos.41530746+1 种基金41901064)the Foundation for Excellent Youth Scholars of NIEER,CAS.
文摘The revegetation protection system(VPS)on the edge of the Tengger Desert can be referred to as a successful model of sand control technology in China and even the world,and there has been a substantial amount of research on revegetation stability.However,it is unclear how meso-and micro-scale revegetation activity has responded to climatic change over the past decades.To evaluate the relative influence of climatic variables on revegetation activities in a restored desert ecosystem,we analysed the trend of revegetation change from 2002 to 2015 using a satellite-derived normalized difference vegetation index(NDVI)dataset.The time series of the NDVI data were decomposed into trend,seasonal,and random components using a segmented regression method.The results of the segmented regression model indicate a changing trend in the NDVI in the VPS,changing from a decrease(−7×10−3/month)before 2005 to an increase(0.3×10−3/month)after 2005.We found that precipitation was the most important climatic factor influencing the growing season NDVI(P<0.05),while vegetation growth sensitivity to water and heat varied significantly in different seasons.In the case of precipitation reduction and warming in the study area,the NDVI of the VPS could still maintain an overall slow upward trend(0.04×10−3/month),indicating that the ecosystem is sustainable.Our findings suggest that the VPS has been successful in maintaining stability and sustainability under current climate change conditions and that it is possible to introduce the VPS in similar areas as a template for resistance to sand and drought hazards.
基金Supported by the National Natural Science Foundation of China(No.81172938)the Program for the Top Science and Technology Innovation Teams of Higher Learning Institutions of Shanxi Province,China+1 种基金the Shanxi Foundation for Overseas Returned,China(No.2008-51)the Program for the Top Young and Middle-aged Innovative Talents of Higher Learning Institutions of Shanxi Province,China
文摘A series of new aurone derivatives was prepared by means of a practical route and their anti-vascular smooth muscle cells（VSMC） vegetation activities were evaluated by the 3-（4,5-dimethylthlazol-2-yl）-2,5- diphenyltetrazolium bromide（MTT） method with tetrandrine as a positive contrast drug. The structures of the com- pounds were confirmed by 1H NMR, 13C NMR and electrospray ionization mass spectrometry（ESI-MS）. Several new compounds exhibited promising activity against VSMC proliferation and the preliminary structure-activity relation- ships（SAR） were discussed in order to investigate the essential structures required for their bioactivities.
基金China Global Change Research Program, No.2010CB951801 No.2010CB950903+1 种基金National Natural Science Foundation of China, No.41001122 No.41030101
文摘Vegetation greenness is a key indicator of terrestrial vegetation activity. To under- stand the variation in vegetation activity in spring across eastern China （EC）, we analysed the variation in the Normalised Difference Vegetation Index （NDVI） from April to May during 1982-2006. The regional mean NDVI across EC increased at the rate of 0.02/10yr （P=0.28; p=0.024） prior to 1998; the increase ceased, and the NDVI dropped to a low level thereafter. However, the processes of variation in the NDVI were different from one region to another. In the North China Plain, a cultivated area, the NDVI increased （0.03/10yr; f2=0.52; p〈0.001） from 1982 to 2006. In contrast, the NDVI decreased （-0.02/10yr; P=0.24; p=0.014） consecu- tively from 1982 to 2006 in the Yangtze River and Pearl River deltas, two regions of rapid urbanisation. In the eastern region of the Inner Mongolian Plateau and the lower reaches of the Yangtze River in East China, the NDVI increased prior to 1998 and decreased thereafter. In the Hulun Buir area and the southern part of the Yangtze River Basin, the NDVI increased prior to 1998 and remained static thereafter. The NDVI in the grasslands and croplands in the semi-humid and semi-arid areas showed a significant positive correlation with precipitation, while the NDVI in the woodlands in the humid to semi-humid areas showed a significant positive correlation with temperature. As much as 60% of the variation in the NDVI was explained by either precipitation or temperature.
基金supported by the National Natural Science Foundation of China (Grant No. 41601438 and 41571078)the Fundamental Research Funds for the Central Universities (Grant No.2412016KJ026)the Foundation of the Education Department of Jilin Province in the 13~(th) Five-Year project (Grant No. JJKH20170916KJ)
文摘The Changbai Mountains and the Appalachian Mountains have similar spatial contexts.The elevation,latitude,and moisture gradients of both mountain ranges offer regional insight for investigating the vegetation dynamics in eastern Eurasia and eastern North America.We determined and compared the spatial patterns and temporal trends in the normalized difference vegetation index(NDVI)in the Changbai Mountains and the Appalachian Mountains using time series data from the Global Inventory Modeling and Mapping Studies 3^(rd) generation dataset from 1982 to 2013.The spatial pattern of NDVI in the Changbai Mountains exhibited fragmentation,whereas NDVI in the Appalachian Mountains decreased from south to north.The vegetation dynamics in the Changbai Mountains had an insignificant trend at the regional scale,whereas the dynamics in the Appalachian Mountains had a significant increasing trend.NDVI increased in 55% of the area of the Changbai Mountains and in 95% of the area of the Appalachian Mountains.The peak NDVI occurred one month later in the Changbai Mountains than in the Appalachian Mountains.The results revealed a significant increase in NDVI in autumn in both mountain ranges.The climatic trend in the Changbai Mountains included warming and decreased precipitation,and whereas that in the Appalachian Mountains included significant warming and increased precipitation.Positive and negative correlations existed between NDVI and temperature and precipitation,respectively,in both mountain ranges.Particularly,the spring temperature and NDVI exhibited a significant positive correlation in both mountain ranges.The results of this study suggest that human actives caused the differences in the spatial patterns of NDVI and that various characteristics of climate change and intensity of human actives dominated the differences in the NDVI trends between the Changbai Mountains and the Appalachian Mountains.Additionally,the vegetation dynamics of both mountain ranges were not identical to those in previous broader-scale studies.
基金Science and Technology Project of State Grid Corporation of China(SGxzzzlwzhbGCJS1700095)National Key Research&Development Program of China(2018YFA0606101,2017YFA0604802)National Natural Science Foundation of China(41501103).
文摘Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities.Since the 1980s,climate has been warming on the Tibetan Plateau(TP)at a rate higher than North Hemisphere average.Anthropogenic activities,including grazing,farming,and urbanization,are also influencing the alpine ecosystem on the TP.Especially,an ensemble of large engineering projects,such as power transported from west to east by State Grid,has been in operation on the TP.While studies disentangling effects of climate and anthropogenic activities interference are still lacking for the forest ecosystems on the TP.The overarching objectives of this study were to separate effects of natural climates and human interferences on forest ecosystem dynamics on the TP.Methods We compared vegetation activities of two typical natural reserves(Gongbu natural reserve,GNR,and Yarlung zangbo river grand canyon natural reserve,YNR)and their surroundings in southeastern Tibet(outside of the natural reserves,ONR)using long-term satel-lite normalized difference vegetation index(NDVI)dataset.Linear regression and partial correlation analyses were constructed for the relationship between vegetation activity and climates to evaluate the distinct climate effects on the two natural reserves.Important Findings The two natural reserves were established at different time,which were related to anthropogenic activities impact durations.The results showed that the annual mean NDVI fluctuated between 0.5 and 0.6 in the relatively longer reserved YNR,which was re-markably higher than those in other regions(with NDVI lower than 0.45).The vegetation vigor in the YNR showed neither a sig-nificant temporal trend nor significant relationship with climate.Nevertheless,vegetation vigor exhibited a significant increasing trend during the last three decades(0.012/decade)at the GNR.The inter-decadal analysis turned out positive relationships between vegetation vigor and annual temperature since late 1990s until early 2000s when the GNR was officially established.This study underlined the importance of considering human interference duration when assessing the relationships between vegetation dy-namics and climates.
文摘Objective： To explore the molecular mechanism of puerarin （Pue） in improving insulin resistance through observing its effect on the insulin resistance of 3T3-Li lipocyte induced by free fatty acid （FFA）. Methods： 3T3-L1 preadipocyte was induced by a culture solution containing insulin, isobutyo-menthyl-xanthine, and dexamethasone to mature lipocyte, and it was divided into six groups： the control group （normal cells）, the model group （untreated model cells）, and the four drug treatment group exposed to dimethyl biguanide （Met group）, high- dose pueradn （PueH group）, low-dose puerarin （PueL group）, and propylene glycol （PG group）, respectively. Mature lipocytes in various groups, except those in the normal group, were established into insulin resistance model by FFA induction and treated respectively with corresponding drugs. Peroxisome proliferator-activated receptor- γ （PPAR- γ） mRNA expressions at the fourth, sixth, and eighth day were observed using reverse transcription polymerase chain reaction （RT-PCR）; glucose transportation in various groups were observed by 2-deoxy-[3H]-D-glucose intake method; mRNA expression of Cbl binding protein （CAP） was determined by RT-PCR; and glucose transporter-4 （Glut-4） transposition was detected by immune-fluorescence method. Results： PPAR- γmRNA expression increased gradually, and it showed lower levels at the fourth, sixth, and eighth day in all treatment groups than that in the model group. Glucose transportation determination showed that the transportation in the model group was 2.23 ± 0.63, significantly lower than that in the normal group 5.05 ± 0.66 （P〈0.01）; as compared with the model group, they were significantly higher in the PueH and the PueL groups. In addition, the CAP mRNA expression and membranous distribution of Glut-4 were higher in the two Pue treated groups than those in the model group, respectively. Conclusion： Pue could markedly improve the insulin resistance of 3T3-L1 lipocyte, which is realized possibly by way of inactivating CAP path, promoting Glut-4 transposition to cell membrane to increase the transportation of glucose.
