Analysis on the Temporal and Spatial Change of Grain Production of China in Recent Years and Its Adaptation Strategies

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.

Temporal and spatial changes of suspended sediment concentration and resuspension in the Yangtze River estuary

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.

Analysis of Temporal and Spatial Changes of Cultivated Land in Karst Areas of Southwest Guangxi Based on Landscape Pattern Indices

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.

Surface air temperature change in the Wuyi Mountains,southeast China

Detecting changes in surface air temperature in mid-and low-altitude mountainous regions is essential for a comprehensive understanding of warming trend with altitude.We use daily surface air temperature data from 64 meteorological stations in Wuyi Mountains and its adjacent regions to analyze the spatio-temporal patterns of temperature change.The results show that Wuyi Mountains have experienced significant warming from 1961 to 2018.The warming trend of the mean temperature is 0.20℃/decade,the maximum temperature is 0.17℃/decade,and the minimum temperature is 0.26℃/decade.In 1961-1990,more than 63%of the stations showed a decreasing trend in annual mean temperature,mainly because the maximum temperature decreased during this period.However,in 1971-2000,1981-2010 and 1991-2018,the maximum,minimum and mean temperatures increased.The fastest increasing trend of mean temperature occurred in the southeastern coastal plains,the quickest increasing trend of maximum temperature occurred in the northwestern mountainous region,and the increase of minimum temperature occurred faster in the southeastern coastal and northwestern mountainous regions than that in the central area.Meanwhile,this study suggests that elevation does not affect warming in the Wuyi Mountains.These results are beneficial for understanding climate change in humid subtropical middle and low mountains.

Spatial and temporal variation of water clarity in typical reservoirs in the Beijing-Tianjin-Hebei region observed by GF 1-WFV satellite data

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.

Temporal and spatial variation of cloud cover in arid regions of Central Asia in the last 40 years

Water resources are one of the key factors restricting the development of arid areas,and cloud water resources is an important part of water resources.The arid region of central Asia is the core region of the current national green silk road construction,and is the largest arid region in the world.Based on cloud cover data of ECMWF,the current study analyzed temporal and spatial characteristics of cloud properties in arid regions of Central Asia between 1980 and 2019.Our findings show that:(1)From the point of view of spatial distribution,total cloudiness in arid regions of Central Asia was low in the south and high in the north.The distribution of high cloud frequency and medium cloud frequency was higher in the south and lower in the north,while low cloud frequency distribution was low in the south and high in the north.(2)In terms of time,the variation of cloud cover and cloud type frequency had obvious seasonal characteristics.From winter to spring,cloud cover increased,and the change of cloud type frequency increased.From spring to summer,cloud cover continued to increase and the change of cloud type frequency increased further.Cloud cover began to decrease from summer to autumn,and the change of cloud type frequency also decreased.(3)Generally,average total cloud cover decreased in most of central Asia,and high and medium cloud cover increased while low cloud cover decreased.This study provides a reference for the rational development of cloud resources in the region.

Spatial and Temporal Changes of Floating Population in China Between 1990 and 2000

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.

Spatial and Temporal Changes of Wetlands on the Qinghai-Tibetan Plateau from the 1970s to 2010s

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.

Spatial Variation of Dissolved Organic Carbon in Soils of Riparian Wetlands and Responses to Hydro-geomorphologic Changes in Sanjiang Plain, China

Spatial variation of dissolved organic carbon(DOC) in soils of riparian wetlands and responses to hydro-geomorphologic changes in the Sanjiang Plain were analyzed through in situ collecting soil samples in the Naoli River and the Bielahong River. The results showed that the average contents of DOC for soil layer of 0–100 cm were 730.6 mg/kg, 250.9 mg/kg, 423.0 mg/kg and 333.1 mg/kg respectively from riverbed to river terrace along the transverse directions of the Naoli watershed. The content of the soil DOC was the highest in the riverbed, lower in the high floodplain and much lower in the river terrace, and it was the lowest in the low floodplain. The difference in the content and vertical distribution of DOC between the riverbed and the three riparian wetlands was significant, while it was not significant among the low floodplain, the high floodplain and the river terrace. The variability of soil DOC was related to the hydrological connectivity between different landscape position of the riparian wetlands and the adjacent stream. Extremely significant correlations were observed between DOC and total organic carbon(TOC), total iron(TFe), ferrous iron(Fe(II)) whose correlation coefficients were 0.819, –0.544 and –0.709 in riparian wetlands of the Naoli River. With the increase of wetland destruction, soil p H increased and soil DOC content changed. The correlation coefficients between soil DOC and TOC, TFe, Fe(II) also changed into 0.759, –0.686 and –0.575 respectively in the Bielahong River. Under the impact of drainage ditches, the correlations between soil DOC and TFe, Fe(II) were not obvious, while the soil p H was weakly alkaline and was negatively correlated with soil DOC in the previous high floodplain. It indicates that riparian hydro-geomorphology is the main factor that could well explain this spatial variability of soil DOC, and the agricultural environmental hydraulic works like ditching also must be considered.

Characteristics of Temperature Change in China over the Last 2000 years and Spatial Patterns of Dryness/Wetness during Cold and Warm Periods

This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3℃ and 0.7℃, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56°± 0.42℃（100 yr）^（-1）; however, temperatures recorded in the 20 th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern： dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20 th century warming can primarily be attributed to a mega El Nino–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.

Analysis on Spatial and Temporal Changes of Extreme Precipitation Events in Ningxia in Recent 50 Years

[ 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.

Latitudinal changes (6°S-20°N) of summer ciliate abundance and species compositions in surface waters from the Java Sea to the South China Sea

Ciliates play a curial role in energy transfer from pico- and nano-phytoplankton to mesozooplankton in marine ecosystems. In order to visualize their geographical distributions from the Java Sea to the South China Sea （6~S to 20~N）, the authors investigated the ciliate abundance and species composition in sur- face waters during May 18 to 27 of 2010. The ciliate abundance decreased latitudinally from 3 080 ind./L （~6~S） to 40 ind./L （-~3~N）, and then increased to 1 180 ind./L （-~ 16~N） at the end of the survey. A total of 22 ciliates belonging to 15 genera were identified with the tintinnids accounted for 50% （11 species）; and the species number showed a same spatial change as the ciliate abundance. Moreover, the Strombidium oc- cupied over 50% of total ciliate abundance in most stations and Mesodiniurn and Tintinnopsis contributed to about 18.7% and 11.4%, respectively. In particular, our results indicate that the geographical changes in ciliate abundance were positively regulated by larger nano- and micro-phytoplankton biomass, rather than smaller pico-phytoplankton in the investigated waters.

Spatial and Temporal Variations of Extreme Climate Events in Xinjiang, China during 1961-2010

Daily maximum/minimum temperature and precipitation data from 35 weather stations in Xinjiang during 1961-2010 were examined using kriging spatial analysis, linear tendency estimation, and correlation analysis. Temporal trends and spatial distribution patterns of extreme temperature and precipitation in this area were then analyzed using 12 extreme temperature and 7 extreme precipitation indices. The following results were obtained. 1) Over the past 50 years, extreme cold indices, excepting the monthly maximum temperature minimum value and monthly extreme minimum temperature, showed slight decreasing trends. These indices include the maximum number of consecutive frost days, icy days, cold-nighttime days, and cold-daytime days. 2) Extreme warm events generally showed significant increasing trends (P < 0.01), including the indices of summertime days, warm-nighttime days, warm-daytime days, monthly extreme maximum temperature, and monthly minimum temperature maximum value. 3) The spatial distributions of threshold values of extreme warm and cold events showed notable regional differences. A reducing trend of extreme cold events and an increase in extreme warm events has occurred mainly in northern Xinjiang. 4) For the past 50 years, six extreme precipitation indices, aside from consecutive dry days, showed significant increasing trends in Xinjiang (P < 0.05) and notable differences in spatial distribution. The increase in extreme precipitation events was more rapid at northern than at southern sites. Extreme precipitation intensity was greater in mountainous areas, and precipitation frequency increased in the plain region. 5) Factor analysis revealed good correlations among extreme temperature indices, excepting extreme temperature days.

Spatial Development of Local Bantik Community in Malalayang, Indonesia

The Proximity between the central business district and the settlement has led to many changes in the local Bantik community. These include changes in the function of settlements, population size, location of residence, and the movement of local culture. This study aims to examine the spatial changes that occur in local neighborhoods with a focus on the Bantik tribal community in Malalayang. Data were obtained from a series of field observations, questionnaires and structured interviews. This study conducted a series of analyses on spatial patterns, sociocultural factors and urban policy. The results show that the dynamic changes are natural and hard to avoid, since they are related to the community＇s needs and development of the city. In order to face the changes, adjustments in the values of the local community towards the settlement terms and conditions are necessary. In addition, an increase in internal resources for those local communities is needed.

Dynamic change of desertified land in each county around Qinghai Lake in recent 30 years

Desertification is one of the most serious eco-environmental problems around Qinghai Lake.Based on GIS and RS,GIS analysis was used to obtain the information of spatial-temporal change and different pattern of desertification in each county around Qinghai Lake in four phases of1976,1987,1995 and 2006.Using the function of intersect and overlay supported by ARCGIS,with analyzing attributes of vector RS images,we obtained transition data and established transfer matrix of land-use types in recent 30 years,besides,protracted land-use transition maps of all desertification classes.In further,we analyzed transition quantity and direction of desertification in each county,moreover,reconstructed the process of spatial-temporal evolution of desertification.The results are showed below:(1)it's the transition between desertified land and others but not in the desertified that played the main role in Gangcha and Gonghe County,while the transfer between desertified lands were greater than that with other land-use types in Haiyan County.(2)Extremely severe desertified land mainly distributes in Ketu and Sand Islands that belongs to Haiyan County,and moderate desertified land in riversides of Gangcha County,also,the light desertification expanded too rapidly to become the most desertified land-use type in the surrounding of Qinghai Lake since 1976.(3)By using relative change rate of desertified land,the regional variability rank from top to toe was Gangcha,Haiyan and Gonghe.

Surface coal mining impacts on land use change and ecological service value:a case study in Shengli coalfield,Inner Mongolia

Coal plays a crucial role in global economic development and remains the most common and widely distributed fossil fuel worldwide.As the world's largest developing country,China's mining and utilization of coal resources have contributed signifcantly to the country’s rapid economic growth.Inner Mongolia is an ecologically fragile arid and semi-arid area of China.The exploitation of opencast mining has seriously hindered the sustainable use of regional land and the residents'well-being.Using ENVI-based remote sensing images from 2000,2005,2010,2015,and 2020,this study employed a random forest algorithm to divide land utilization types into construction land,vegetation,cultivated land,bare land,and water areas and analyzed the characteristics of land use and ecosystem service value changes over the past 20 years.The results were as follows:(1)Construction land in the mining area changed minimally from 2000 to 2020;vegetation and water bodies showed a decreasing trend,whereas bare and cultivated lands showed an increasing trend.Bare land exhibited the largest change in area proportion and water bodies the smallest.(2)The total ecosystem service value of the mining area declined from 10.939 to 9.527 billion Yuan.Vegetation ecosystem service value was the highest,followed by cultivated land and water,with the bare land ecosystem service value the lowest.(3)On a spatial scale,the total ecosystem service value of the Shengli mining area decreased year by year,indicating that land use changes in the mining area do have an impact on ecosystem service value.

A New Method Based on Association Rules Mining and Geo-filter for Mining Spatial Association Knowledge

Association rule mining methods, as a set of important data mining tools, could be used for mining spatial association rules of spatial data. However, applications of these methods are limited for mining results containing large number of redundant rules. In this paper, a new method named Geo-Filtered Association Rules Mining(GFARM) is proposed to effectively eliminate the redundant rules. An application of GFARM is performed as a case study in which association rules are discovered between building land distribution and potential driving factors in Wuhan, China from 1995 to 2015. Ten sets of regular sampling grids with different sizes are used for detecting the influence of multi-scales on GFARM. Results show that the proposed method can filter 50%–70% of redundant rules. GFARM is also successful in discovering spatial association pattern between building land distribution and driving factors.

Vegetation Coverage Changes in the West Qinling Region from 2000 to 2010:A Case Study of Longnan City

As the main content of terrestrial ecosystem study,vegetation coverage change has gained extensive attention in the process of global climate change and sustainable development recently.Based on MODIS NDVI data from June to October during 2000-2010,taking Longnan City as a case area,this paper develops the calculation method of vegetation coverage(VC) by using Pixel Dichotomy model and analyzes the spatial-temporal variation of vegetation coverage in the West Qinling region by using simple linear regression and standard deviation method.The results show that vegetation coverage remains stable and is significantly correlated with temperature and precipitation during the decade.The vegetation coverage of 90% of study area shows stability with small annual variation and also is consistent with the spatial distribution of forest land;the vegetation coverage in the remaining study areas shows a growing trend with significant variation and also is consistent with the spatial distribution of farmland and grassland,especially in Huicheng Basin,Xili Basin and adret slope of Bailongjiang River Valley,indicating that Project about the Conversion of Degraded Farmland into Forest has made a great contribution to vegetation coverage increase.This paper proves the effect of ecology construction in the West Qinling region since the late 20 th century.All the findings also provide references for local ecological environment construction and sustainable development.

Community structure and spatial-temporal variation of netzphytoplankton in the Bering Sea in summer

Marine biodiversity is changing in response to altered physical environment, subsequent ecological changes as well as anthropogenic disturbances. In this study, phytoplankton samples in situ collected in the Bering Sea in July of 1999 and 2010 were analyzed to obtain phytoplankton community structure and spatial-temporal variation between the beginning and end of this decade, and the correlation of phytoplankton community dynamics and environmental factors was investigated. A total of 5 divisions, 58 genera and 153 species of phytoplankton belonging to 3 ecological groups were identified. The vast majority of phytoplankton consisted of diatoms accounting for 66.7% of the total species and 95.2% of the total abundance. Considering differentiation in spatial extent and phytoplankton sample types, there were subtle changes in species composition, large altering in abundance and significant variation in spatial distribution between two surveys. The abundance peak area was located at the Bering Strait while sub peak was found at the Bering Sea Basin. The boreal-temperate diatom was the dominant flora, which was subsequently replaced by eurythermal and frigid-water diatom. Phytoplankton community in the Bering Sea was not a simplex uniform community but composed of deep-ocean assemblage and neritic assemblage. The deep-ocean assemblage was located in the northwestern Pacific Ocean and Bering Sea Basin, dominated by boreal-temperate species（Neodenticula seminae, Thalassiothrix longissima, Amphiprora hyperborean, Chaetoceros atlanticus, Thalassiosira trifulta, etc.） and eurychoric species（Thalassionema nitzschioides, Ch. compressus, Rhizosolenia styliformis, etc.）, and characterized by low abundance, even interspecies abundance allocations, diverse dominant species and high species diversity. The neritic assemblage was distributed on the continental shelf and slope of Bering Sea and was mainly composed of frigid-water species（Th.nordenski？ldii, Ch. furcellatus, Ch. socialis, Bacteriosira fragilis, etc.） and eurythermal and euryhaline species（L.danicus, Ch. curvisetus, Coscinodiscus curvatulus, etc.）, and it was characterized by high abundance, uneven interspecies allocations, prominent dominant species and low species diversity. Spatial-temporal variation of species composition and abundance of phytoplankton in the Bering Sea was directly controlled by surface circulation,nutrient supply and ice edge.

Research on Frequency of the Aftershock Sequence of the Wenchuan Earthquake Based on Coseismic Coulomb Stress Change

By the aftershock frequency estimation method based on the calculation of coseismic static Coulomb stress changes and rate-and state-dependent fault constitutive law,we calculate the frequency of "direct "aftershocks of the Wenchuan earthquake related to coseismic static Coulomb stress changes in its aftershock zone and the areas nearby.It shows that the frequency is significantly lower than the truth in the main rupture zone,especially in the southern rupture zone,due to the decrease of stress level on the rupture plane of the main shock resulting from coseismic Coulomb stress change.The study also shows that the effect of the Coulomb stress change on the duration of aftershock activity is associated with the lower limit magnitude.The duration is about 15-16 months for aftershocks above ML4.0,and close to 60 months for aftershocks above ML3.5.In this period,the ratio of the"direct"aftershocks caused by coseismic Coulomb stress change ranges between 44.7% to48.6%,which suggests that,even in the "effective"period of coseismic Coulomb stress changes,about half of the aftershocks on the main shock rupture plane are independent of coseismic Coulomb stress changes.It is pointed out that those aftershocks may be related to the afterslip or the viscoelastic relaxation,which are time dependent cases.