Vegetation Changes in Alberta Oil Sands,Canada,Based on Remotely Sensed Data from 1995 to 2020

There are rich oil and gas resources in Alberta oil sand mining area in Canada.Since the 1960s,the Canadian government decided to increase the mining intensity.However,the exploitation will bring many adverse effects.In recent years,more people pay attention to the environmental protection and ecological restoration of mining area,such as issues related with changes of vegetated lands.Thus,the authors used the Landsat-5 TM and Landsat-8 OLI remote sensing images as the basic data sources,and obtained the land cover classification maps from 1995 to 2020 by ENVI.Based on the NDVI,NDMI and RVI,three images in each period are processed and output to explore the long-term impact of exploitation.The results show that from 1995 to 2020,the proportion of vegetation around mining areas decreased sharply,the scale of construction land in the mining area increased,and the vegetated land was changed to land types such as tailings pond,oil sand mine and other land types.In addition,three vegetation indexes decreased from 1995 to 2020.Although the exploitation of oil sand mining area brings great economic benefits,the environmental protection(especially vegetation)in oil sand mining areas should be paid more attention.

Modeling Impacts of Vegetation in Western China on the Summer Climate of Northwestern China

Using the monthly NCEP-NCAR reanalysis dataset, the monthly temperature and precipitation at surface stations of China, and the MM5 model, we examine impacts of vegetation cover changes in western China on the interdecadal variability of the summer climate over northwestern China during the past 30 years. It is found that the summer atmospheric circulation, surface air temperature, and rainfall in the 1990s were different from those in the 1970s over northwestern China, with generally more rainfall and higher temperatures in the 1990s. Associated with these changes, an anomalous wave train appears in the lower troposphere at the midlatitudes of East Asia and the low-pressure system to the north of the Tibetan Plateau is weaker. Meanwhile, the South Asian high in the upper troposphere is also located more eastward. Numerical experiments show that change of vegetation cover in western China generally forces anomalous circulations and temperatures and rainfall over these regions. This consistency between the observations and simulations implies that the interdecadal variability of the summer climate over northwestern China between the 1990s and 1970s may result from a change of vegetation cover over western China.

Vegetation change as related to terrain factors at two glacier forefronts, Glacier National Park, Montana, U.S.A.

Glacier recession is a globally occurring trend. Although a rich body of work has documented glacial response to climate warming, few studies have assessed vegetation cover change in recently deglaciated areas, especially using geospatial technologies. Here, vegetation change at two glacier forefronts in Glacier National Park, Montana, U.S.A.was quantified through remote sensing analysis,fieldwork validation, and statistical modeling.Specifically, we assessed the spatial and temporal patterns of landcover change at the two glacier forefronts in Glacier National Park and determined the role of selected biophysical terrain factors(elevation, slope, aspect, solar radiation, flow accumulation, topographic wetness index, and surficial geology) on vegetation change(from nonvegetated to vegetated cover) at the deglaciated areas.Landsat imagery of the study locations in 1991, 2003,and 2015 were classified and validated using visual interpretation. Model results revealed geographic differences in biophysical correlates of vegetation change between the study areas, suggesting that terrain variation is a key factor affecting spatialtemporal patterns of vegetation change. At Jackson Glacier forefront, increases in vegetation over some portion or all of the study period were negatively associated with elevation, slope angle, and consolidated bedrock. At Grinnell Glacier forefront,increases in vegetation associated negatively with elevation and positively with solar radiation.Integrated geospatial and field approaches to the study of vegetation change in recently deglaciated terrain are recommended to understand and monitor processes and patterns of ongoing habitat change in rapidly changing mountain environments.

Integrating cross-sensor high spatial resolution satellite images to detect subtle forest vegetation change in the Purple Mountains,a national scenic spot in Nanjing,China

Accurate information on the location and magnitude of vegetation change in scenic areas can guide the configuration of tourism facilities and the formulation of vegetation protection measures.High spatial resolution remote sensing images can be used to detect subtle vegetation changes.The major objective of this study was to map and quantify forest vegetation changes in a national scenic location,the Purple Mountains of Nanjing,China,using multi-temporal cross-sensor high spatial resolution satellite images to identify the main drivers of the vegetation changes and provide a reference for sustainable management.We used Quickbird images acquired in 2004,IKONOS images acquired in 2009,and WorldView2 images acquired in 2015.Four pixel-based direct change detection methods including the normalized difference vegetation index difference method,multi-index integrated change analysis(MIICA),principal component analysis,and spectral gradient difference analysis were compared in terms of their change detection performances.Subsequently,the best pixel-based detection method in conjunction with object-oriented image analysis was used to extract subtle forest vegetation changes.An accuracy assessment using the stratified random sampling points was conducted to evaluate the performance of the change detection results.The results showed that the MIICA method was the best pixel-based change detection method.And the object-oriented MIICA with an overall accuracy of 0.907 and a kappa coefficient of 0.846 was superior to the pixel-based MIICA.From 2004 to 2009,areas of vegetation gain mainly occurred around the periphery of the study area,while areas of vegetation loss were observed in the interior and along the boundary of the study area due to construction activities,which contributed to 79%of the total area of vegetation loss.During 2009–2015,the greening initiatives around the construction areas increased the forest vegetation coverage,accounting for 84%of the total area of vegetation gain.In spite of this,vegetation loss occurred in the interior of the Purple Mountains due to infrastructure development that caused conversion from vegetation to impervious areas.We recommend that:(1)a local multi-agency team inspect and assess law enforcement regarding natural resource utilization;and(2)strengthen environmental awareness education.

Climate Change and Ecological Projects Jointly Promote Vegetation Restoration in Three-River Source Region of China

As the source of the Yellow River,Yangtze River,and Lancang River,the Three-River Source Region(TRSR)in China is very important to China’s ecological security.In recent decades,TRSR’s ecosystem has degraded because of climate change and human disturbances.Therefore,a range of ecological projects were initiated by Chinese government around 2000 to curb further degradation.Current research shows that the vegetation of the TRSR has been initially restored over the past two decades,but the respective contribution of ecological projects and climate change in vegetation restoration has not been clarified.Here,we used the Moderate Resolution Imaging Spectroradiometer(MODIS)Enhanced Vegetation Index(EVI)to assess the spatial-temporal variations in vegetation and explore the impact of climate and human actions on vegetation in TRSR during 2001–2018.The results showed that about 26.02%of the TRSR had a significant increase in EVI over the 18 yr,with an increasing rate of 0.010/10 yr(P<0.05),and EVI significantly decreased in only 3.23%of the TRSR.Residual trend analysis indicated vegetation restoration was jointly promoted by climate and human actions,and the promotion of human actions was greater compared with that of climate,with relative contributions of 59.07%and40.93%,respectively.However,the degradation of vegetation was mainly caused by human actions,with a relative contribution of71.19%.Partial correlation analysis showed that vegetation was greatly affected by temperature(r=0.62,P<0.05)due to the relatively sufficient moisture but lower temperature in TRSR.Furthermore,the establishment of nature reserves and the implementation of the Ecological Protection and Restoration Program(EPRP)improved vegetation,and the first stage EPRP had a better effect on vegetation restoration than the second stage.Our findings identify the driving factors of vegetation change and lay the foundation for subsequent effective management.

Vegetation change and its response to drought in Inner Mongolia of northern China from 1998 to 2013

Vegetation plays a significant role in global terrestrial ecosystems and in combating desertification.We analyzed vegeta tion change in Inner Mongolia of northern China using the Normalized Difference Vegetation Index(NDVI)from 1998 to 2013,which is an important composite of Chinese National Ecological Security Shelter.The correlation between vegeta tion growth and drought quantified using the Standardized Precipitation Evapotranspiration Index(SPEI)was also ex plored.Results show that vegetation in most of the study area has been rehabilitated to various degrees,especially in re gions such as most of the Horqin Sandy Land,eastern Ordos Plateau,Hetao Plain,as well as the middle-northern Da Hing gan Ling Mountains.Vegetation improvement in spring was significant in most of the study area.Vegetation degradation was centrally distributed in Xilingol grassland close to the Sino-Mongolia border and abandoned croplands in Ulanqab Meng.Vegetation change trends and seasonal differences varied among different vegetation types.The biggest vegetation variation in the growing season was the belt-like distribution along those grasslands close to the precipitation isoline of 200 mm and the Sino-Mongolia border,but also variation in summer and autumn exist in obvious spatial differences be tween grasslands and forests.Drought largely influenced vegetation change of Inner Mongolia at 6-month scale or 12-month scale,except for forests of eastern Hunlun Buir Meng and deserts or gobi deserts of western Alxa Meng.Moreover,drought in the previous winter and early spring seasons had a lag effect on growing-season vegetation.Desert grassland was the most easily affected by drought in the study area.Anthropogenic activities have made great progress in improving local vegetation under the lasting drought background.

VEGETATION CHANGE IN THE MT.QOMOLANGMA NATURAL RESERVE FROM 1981 TO 2001

1 Introduction On 18 May 1989,the Mt.Qomolangma (Everest)Natural Reserve(abbr.MQNR)in Tibet Autonomous Region formally came into existence and it was listed as World Network of Biosphere Reserves(WNBR)in May 2005.The MQNR is a comprehensive reserve,which mainly protects alpine ecosystems,plateau natural landscapes,geological remains and Tibetan historical and cultural heritages.

Response of Vegetation Cover Change to Drought at Different Time-scales in the Beijing-Tianjin Sandstorm Source Region,China

Dominated by an arid and semiarid continental climate,the Beijing-Tianjin Sandstorm Source Region(BTSSR)is a typical ecologically fragile region with frequently occurring droughts.To provide information for regional vegetation protection and drought prevention,we assessed the relations between vegetation cover change(measured by the Normalized Difference Vegetation Index,NDVI)and the Standardized Precipitation Evapotranspiration Index(SPEI)at different time-scales,in different growth stages,in different subregions and for different vegetation types based on the Pearson's correlation coefficient in the BTSSR from 2000 to 2017.Results showed that 88.19%of the vegetated areas experienced increased NDVI in the growing season;48.3%of the vegetated areas experi-enced significantly increased NDVI(P<0.05)and were mainly in the south of the BTSSR.During the growing season,a wetter climate contributed to the increased vegetation cover from 2000 to 2017,and NDVI anomalies were closely related to SPEI.The maximum correlation coefficient in the growing season(Rmax)was significantly positive(P<0.05)in 97.84%of the total vegetated areas.In the vegetated areas with significantly positive Rmax,pixels with short time-scales(1-3 mon)accounted for the largest proportion(33.9%).The sensitivity of vegetation to the impact of drought rose first and then decreased in the growing season,with a peak in July.Compared with two subregions in the south,subregions in the north of the BTSSR were more sensitive to the impacts of drought variations,especially in the Xilingol Plateau and Wuzhumuqin Basin.All four major vegetation types were sensitive to the effects of drought variations,especially grasslands.The time-scales of the most impacting droughts varied with growth stages,regions,and vegetation types.These results can help us understand the relations between vegetation and droughts,which are important for ecological restoration and drought prevention.

CHINA'S VEGETATION/ECOSYSTEM RESPONSE TO GLOBAL CHANGE: RESEARCH PROGRESS & PROSPECTS

This paper presents the latest developments in the re search progress on mechanisms by which natural plants and crops respond to the doubled concentration of CO2 in the atmosphere, resultant climatic change and the modeling of vegetation and eco-systems in China. In addition, it points out that the future study on global change and terrestrial ecosystems should stress m(?)iti-disciplinary teamwork and inter-discipline penetration. Finally, the paper emphasizes 10 research realms in the field to be enhanced in the future.

Diachronic Study of the Vegetation Covers Spatiotemporal Change Using GIS and Remote Sensing in the Ferkla Oasis: Case Study, Bour El Khourbat, Tinjdad, Morocco

The Oasis of Ferkla is part of the Oases of Tafilalt in southern Morocco. These are classified by UNESCO as the Oases of Southern Morocco Biosphere Reserve. The Ferkla Oasis is increasingly experiencing a situation of increased regression and degradation, aggravated by the effects of climate change. These foreshadow a considerable acceleration of desertification and drought with the effect of the loss of production systems whose social, ecological and economic role remains major for the whole country. In order to contribute to a better understanding of the dynamics of the vegetation in this territory and the impact of climate change in the Oasis of Ferkla, we used spatial remote sensing to trace the evolution of changes in the vegetation cover in an agricultural extension called Bour El Khourbat. Calculation of the Normalized Difference Vegetation Index for seven multidate satellite images allowed us to follow the vegetation in this oasis zone from the year 1984 to 2019. Indeed, from these multi-temporal images, this study clearly shows the evolution of the vegetation with a remarkable agricultural extension towards the South-East of the zone. This extension is due not only to the installation of a diversion dam upstream but also to the development of the localized irrigation system “Drop by Drop” which is a technique that saves water resources in addition to the presence in the area. Bour El Khourbat specifies a geological structure, in the primary, relatively favorable to having water linked to cracks.

Changes in Vegetation and Assessment of Meteorological Conditions in Ecologically Fragile Karst Areas

Meteorological conditions have an important impact on changes of vegetation in ecologically fragile karst areas.This study aims to explore a method for quantitative evaluation of these meteorological conditions. We analyzed the changing trend of vegetation during 2000–2018 and the correlations between vegetation changes and various meteorological factors in karst rocky areas of Guangxi Zhuang Autonomous Region, China. Key meteorological factors in vegetation areas with varying degrees of improvement were selected and evaluated at seasonal timescale. A quantitative evaluation model of comprehensive influences of meteorological factors on vegetation was built by using the partial least-square regression(PLS). About 91.45% of the vegetation tended to be improved, while only the rest 8.55% showed a trend of degradation from 2000 to 2018. Areas with evident vegetation improvement were mainly distributed in the middle and northeast, and those with obvious vegetation degradation were scattered. Meteorological factors affecting vegetation were significantly different among the four seasons. Overall, high air humidity, small temperature difference in spring and autumn, and low daily minimum temperature and air pressure were favorable conditions. Low temperature in winter as well as high temperature in summer and autumn were unfavorable conditions. The Climate Vegetation Index(CVI) model was established by PLS using the maximum, minimum, and average temperatures;vapor pressure;rainfall;and air pressure as key meteorological factors. The Enhanced Vegetation Index(EVI) was well fitted by the CVI model, with the average coefficient of determination(r2) and root mean square error(RMSE) of 0.856 and 0.042, respectively. Finally, an assessment model of comprehensive meteorological conditions was built based on the interannual differences in CVI. The meteorological conditions in the study area in 2014 were successfully evaluated by combining the model and selected seasonal key meteorological factors.

Changes in vegetation and moisture in the northern Tianshan of China over the past 450 years

Knowledge of historical changes in moisture within semi-arid and arid regions is the basis of climatic change predictions and strategies in response to long-term drought.In this study,a multiproxy peat record with highresolution from Sichanghu in the northern Tianshan was used to document the changes in vegetation and climate over the past 450 years in the arid Central Asia.The pollen,grain size,and loss on ignition(LOI)records indicate that the productivity of local peat began to increase at^1730 AD.The vegetation in the Sichanghu area experienced several transitions,from temperate desert to dense desert,marsh meadow,and steppe desert vegetation.The climate in the study area was extremely dry during the early stages of the Little Ice Age(LIA)(before 1730 AD)and relatively wet during the late stages(1730–1880 AD).The inferred changes in the moisture conditions of the Sichanghu peatland since the LIA may have been controlled by the extent of Arctic sea ice,the North Atlantic Oscillation,and the Siberian High via the connections of large-scale atmospheric circulations such as the Westerlies.

Strengthened African Summer Monsoon in the Mid-Piacenzian

Using model results from the first phase of the Pliocene Model Intercomparison Project （PlioMIP） and four experiments with CAM4, the intensified African summer monsoon （ASM） in the mid-Piacenzian and corresponding mechanisms are analyzed. The results from PlioMIP show that the ASM intensified and summer precipitation increased in North Africa during the mid-Piacenzian, which can be explained by the increased net energy in the atmospheric column above North Africa. Further experiments with CAM4 indicated that the combined changes in the mid-Piacenzian of atmospheric CO2 concentration and SST, as well as the vegetation change, could have substantially increased the net energy in the atmospheric column over North Africa and further intensified the ASM. The experiments also demonstrated that topography change had a weak effect. Overall, the combined changes of atmospheric CO2 concentration and SST were the most important factor that brought about the intensified ASM in the mid-Piacenzian.

An Analysis of Spatio-Temporal Trends of Land Surface Temperature in the Dhaka Metropolitan Area by Applying Landsat Images

Land surface temperature (LST) is a basic determinant of the global thermal behavior of the Earth surface. LST is a vital consideration for the appraisal of gradual thermal change for urban areas to examine the strength of the thermal intensity of the surface of urban heat island (SUHI) and to see how hot the surface of the Earth would be in a particular location. In this respect, the most developed urban city like Dhaka Metropolitan Area (DMA), Bangladesh is considered for estimation of LST, and Normalized Difference Vegetation Index (NDVI) changes trend in more developed and growing developing areas. The focus of this study is to find out the critical hotspot zones for further instantaneous analysis between these two types of areas. The trends of long-term spatial and temporal LST and NDVI are estimated applying Landsat images-Landsat 5-TM and Landsat OLI_TIRS-8 for the period of 1988 to 2018 for DMA and for developed and growing developing areas during the summer season like for the month of March. The supervised classification was used to estimate the land cover categories and to generate the LST trends maps of the different percentiles of LSTs over time using the emissivity and effective at sensor brightness temperature. The study found the change in land cover patterns by different LST groups based on 50th, 75th, and 90th percentile where the maximum LST for the whole DMA went up by 2.48°C, 1.01°C, and 3.76°C for the months of March, April, and May, respectively for the period of 1988 to 2018. The highest difference in LST was found for the most recently developed area. The moderate change of LST increased in the built-up areas where LST was found more sensitive to climate change than the growing developed areas. The vegetation coverage area decreased by 6.74% in the growing, developing areas compared to the developed areas from 1988 to 2018. The findings of the study might be helpful for urban planners and researchers to take up appropriate measures to mitigate the thermal effect on urban environment.

Holocene millennial-scale megaflood events point to ENSO-driven extreme climate changes

Reconstructing the Holocene megaflood history is a key component of understanding the mechanism of past climate change and assessing the potential impact of future catastrophic events.The Pearl River is the longest watercourse in southern China,and its lower reach has been identified as one of the world's most vulnerable regions for flood exposure.However,there is a complete lack of millennial-scale geological records of paleomegafloods for the future prediction of once-in-a-hundred(even once-in-a-thousand)year floods in southern China.Here,we identified a series of paleomegaflood deposits interbedded with wood-rich peat layers in the lower West Pearl River area.All paleoflood layers have been well dated using AMS~(14)C dating method.According to the regional correlation of the flood sequence,sediment characteristics and provenance analysis,there have been at least 7 megafloods corresponding to once-in-a-thousand-year events in the lower reaches of the West Pearl River during the past 6000 years,with an average return period of approximately 855 years.The identified paleomegafloods were coeval with periods of strong El Ni?o-Southern Oscillation(ENSO),indicating that weakening of the Asian summer monsoon,associated with enhanced ENSO variability,may have triggered abnormally high precipitation leading to flooding of exceptional magnitude in southern China.In addition,the most prominent paleomegafloods identified in the lower Pearl River coincided with intervals of lower precipitation and fewer storms in central-eastern China,indicating the intensification of the meridional“tripole”pattern of precipitation across eastern China during the latter half of the Holocene.Increased land use and deforestation over the last 2000 years have resulted in soil loss and rapid degradation of local primeval forest ecosystems,leading to more catastrophic flooding.Large amounts of rice pollen in the uppermost flood layer during the Song Dynasty indicate that this megaflood may have inundated a large area of cultivated land.The periodic occurrence of Holocene megafloods not only caused damage to human existence,but also affected the evolution of local civilization.This study reveals for the first time a series of Holocene millennial-scale megafloods and sheds new light on the importance of atmosphere-ocean interactions in the tropical Pacific and monsoon subtropical climate dynamics for precipitation anomalies in East Asia.Our data yield valuable information for future research into climate extremes and hazard prevention.

Vegetation stability during the last two centuries on the western Tibetan Plateau:a palynological evidence

Investigating the dynamics of vegetation is an essential basis to know how to protect ecological environments and to help predict any changes in trend.Because of its fragile alpine ecosystem,the Tibetan Plateau is a particularly suitable area for studying vegetation changes and their driving factors.In this study,we present a high-resolution pollen record covering the last two centuries extracted from Gongzhu Co on the western Tibetan Plateau.Alpine steppe is the predominant vegetation type in the surrounding area throughout the past 250 years with stable vegetation composition and abundance,as revealed by pollen spectra dominated by Artemisia,Ranunculaceae,Cyperaceae,and Poaceae.Detrended canonical correspondence analysis(DCCA)of the pollen data reveals low turnover in compositional species(0.41 SD),suggesting that the vegetation in the Gongzhu catchment had no significant temporal change,despite climate change and population increases in recent decades.We additionally ran DCCA on ten other pollen records from the Tibetan Plateau with high temporal resolution(1-20 years)covering recent centuries,and the results also show that compositional species turnover(0.15-0.81 SD)is relatively low,suggesting that the vegetation stability may have prevailed across the Tibetan Plateau during recent centuries.More high-resolution pollen records and high taxonomic-resolution palaeo-vegetation records(such as sedaDNA),however,are needed to confirm the vegetation stability on the Tibetan Plateau.

Integration of Landsat time-series vegetation indices improves consistency of change detection

Vegetation indices(VIs)were used to detect when and where vegetation changes occurred.However,different VIs have different or even diametrically opposite results,which obstructed the in-depth understanding of vegetation change.Therefore,this study examined the spatial and temporal consistency offive VIs(EVI;NBR;NDMI;NDVI;and NIRv)in detecting abrupt and gradual vegetation changes,and provided an ensemble algorithm which integrated the change detection results of thefive indices to reduce the uncertainty of change detection using a single index.The spatial consistency of thefive indices in abrupt change detection accounted for 50.6%of the study area,but the temporal consistency was low(21.6%).Wetness indices(NBR,NDMI)were more sensitive to negative abrupt changes,greenness indices(EVI,NDVI,NIRv)were more sensitive to positive abrupt changes;and both types of indices were similar in detecting gradual and total changes.The overall accuracy of the ensemble method was 81.60%and higher than that of any single index in abrupt change detection.This study provides a comprehensive evaluation of the spatial and temporal inconsistencies of change detection in model-fitting errors and various types of vegetation changes.The proposed ensemble method can support robust change-detection.

Impact of Land Reclamation on the Vegetal Cover of Bayelsa State, Nigeria

The study examined the impact of land reclamation on vegetal cover in Bayelsa State.For the purpose of this study,both quantitative and quali­tative research methods were adopted.Field observations,questionnaire survey and landsat imagery of land cover changes in the year 1986 and 2018 were generated from the global ground cover facility stream.The time series study design and supervised classification of the image processing were adopted to determine the impact of land reclamation on vegetal cover of the study area.It was therefore recommended that recovery of land will make strategic urban planning initiatives sustainable in overcrowded areas and institutions should also put in place laws and strategies to regulate rec­lamation activities across the region and also geo-spatial skills should be put in place to help quantify the dynamics,trends and rate of reclamation induced land cover change in the environment.

Responses of grassland vegetation to climatic variations on different temporal scales in Hulun Buir Grassland in the past 30 years

Global warming has led to significant vegetation changes especially in the past 20 years. Hulun Buir Grassland in Inner Mongolia, one of the world’s three prairies, is undergoing a process of prominent warming and drying. It is essential to investigate the effects of climatic change （temperature and precipitation） on vegetation dynamics for a better understanding of climatic change. NDVI （Normalized Difference Vegetation Index）, reflecting characteristics of plant growth, vegetation coverage and biomass, is used as an indicator to monitor vegetation changes. GIMMS NDVI from 1981 to 2006 and MODIS NDVI from 2000 to 2009 were adopted and integrated in this study to extract the time series characteristics of vegetation changes in Hulun Buir Grassland. The responses of vegetation coverage to climatic change on the yearly, seasonal and monthly scales were analyzed combined with temperature and precipitation data of seven meteorological sites. In the past 30 years, vegetation coverage was more correlated with climatic factors, and the correlations were dependent on the time scales. On an inter-annual scale, vegetation change was better correlated with precipitation, suggesting that rainfall was the main factor for driving vegetation changes. On a seasonal-interannual scale, correlations between vegetation coverage change and climatic factors showed that the sensitivity of vegetation growth to the aqueous and thermal condition changes was different in different seasons. The sensitivity of vegetation growth to temperature in summers was higher than in the other seasons, while its sensitivity to rainfall in both summers and autumns was higher, especially in summers. On a monthly-interannual scale, correlations between vegetation coverage change and climatic factors during growth seasons showed that the response of vegetation changes to temperature in both April and May was stronger. This indicates that the temperature effect occurs in the early stage of vegetation growth. Correlations between vegetation growth and precipitation of the month before the current month, were better from May to August, showing a hysteresis response of vegetation growth to rainfall. Grasses get green and begin to grow in April, and the impacts of temperature on grass growth are obvious. The increase of NDVI in April may be due to climatic warming that leads to an advanced growth season. In summary, relationships between monthly-interannual variations of vegetation coverage and climatic factors represent the temporal rhythm controls of temperature and precipitation on grass growth largely.

Vegetation-related dry deposition of global PM_(2.5) from satellite observations

Vegetation plays an important role in the dry deposition of particles with significant spatial variability,but the magnitude remains unclear at the global scale.With the aid of satellite products,this study estimated the vegetation-related dry deposition of fine particulate matter(PM_(2.5)).Methodologically,dry deposition was first calculated using an empirical algorithm.Then,deposition on the leaf surface was estimated to evaluate the influence of vegetation.Our results showed that the mean deposition velocity(V_(d))of global PM_(2.5)was 0.91×10^(-3)μg·m^(-2)·s^(-1),with high velocities observed in sparsely vegetated regions because of the high friction velocity.Under the combined effect of the PM_(2.5)mass concentration and deposition velocity,the global mean dry deposition reached 0.47 g·m-^(2)·yr^(-1).Global vegetation absorbed 0.26 g·m-^(2)·yr^(-1)from PM_(2.5)pollution sources,contributing 54.98%of the total dry deposition.Spatially,vegetation-related dry deposition was high in the Amazon,Central Africa and East China due to dense vegetation coverage or serious pollution.Temporally,the increasing trends were mainly in Central Africa and India because of worsening air pollution.The results of this study helped to clarify the impact of vegetation on air pollution,which supported related land management and planning for air quality improvement.