Spatial-temporal dynamics of desert vegetation and its responses to climatic variations over the last three decades:a case study of Hexi region in Northwest China

Analysis of spatial-temporal variations of desert vegetation under the background of climate changes can provide references for ecological restoration in arid and semi-arid areas. In this study, we used the Global Inventory Modeling and Mapping Studies （GIMMS） NDVI data from 1982 to 2006 and Moderate Resolution Imaging Spectroradiometer （MODIS） NDVI data from 2000 to 2013 to reveal the dynamics of desert vegetation in Hexi region of Northwest China over the past three decades. We also used the annual temperature and precipitation data acquired from the Chinese meteorological stations to analyze the response of desert vegetation to climatic variations. The average value of NDVImax （the maximum NDVI during the growing season） for desert vegetation in Hexi region increased at the rate of 0.65x10-3/a （P〈0.05） from 1982 to 2013, and the significant increases of NDVImax mainly appeared in the typical desert vegetation areas. Vegetation was significantly improved in the lower reaches of Shule and Shiyang river basins, and the weighted mean center of desert vegetation mainly shifted toward the lower reaches of the two basins. Almost 95.32% of the total desert vegetation area showed positive correlation between NDVImax and annual precipitation, indicating that precipitation is the key factor for desert vegetation growth in the entire study area. Moreover, the areas with non-significant positive correlation between NDVImax and annual precipitation mainly located in the lower reaches of Shiyang and Shule river basins, this may be due to human activities. Only 7.64% of the desert vegetation showed significant positive correlation between NDVImax and annual precipitation in the Shule River Basin （an extremely arid area）, indicating that precipitation is not the most important factor for vegetation growth in this basin, and further studies are needed to investigate the mechanism for this phenomenon.

Spatial-temporal differences in in-stream flow requirement based on GIS： A case study of Yan＇an region, northern Shaanxi

Although water has the central function of the bloodstream in the biosphere especially in arid or semi-arid regions such as Yah＇an region in northwestern China, yet the very limited attention is paid to the role of the water-related processes in ecosystem. In this research, based on continuous nearly 50-year data including runoff volume, sediment discharge as well as sediment accretion from hydrographic stations, and 10-year information of water quality from pollution monitoring stations, the method for measuring in-stream flow requirement has been put forward supported by experiential models and GIS spatial analysis. Additionally, the changes of in-stream flow requirement for environment and economic development have been addressed from spatial-temporal dimensions. The results show that： （1） According to the central streams in Yan＇an region, mean annual in-stream flow requirement reaches 1.0619 billion m^3, and the surface water for economic exploitation is 0.2445 billion m3 （2） Mean annual in-stream flow requirement for sediment transfers in flood period occupies over 80% of the integrated volume in a year. （3） From the 1950s to 1970s, in-stream flow requirement for sediment transfers is comparatively higher, while from the 1980s to 1990s, this requirement presents a decreasing tendency.

Temporal-spatial change and driving mechanism for regional difference of domestic tourism in China

By using the variation coefficient,Gini coefficient and Theil coefficient,this paper makes preliminary exploration of temporalspatial change features and driving mechanism for regional differences of domestic tourism in China from 1995 to 2009.According to the results,we drew the following conclusions:(1)The regional difference of domestic tourism in China tends to be narrowing generally,and is less than that of inbound tourism,playing an important role in narrowing the overall gap of regional tourism in China.(2)The regional internal difference features:inter-provincial difference in the eastern region and difference among the eastern,central and western regions are comparatively obvious and demonstrate a significantly shrinking tendency,the change tendency is consistent with the change tendency of overall difference and exercises a decisive role in overall difference,whereas the inter-provincial difference in the central and western regions is small and relatively stable,having less influence on the overall difference.(3)The temporal-spatial change in regional difference is featured by:low-level provinces occupy a majority and are concentrated in the central and western regions,showing a tendency of narrowing difference;high-level provinces are concentrated in the eastern region,showing a tendency of spreading to the central and western regions;spatial pattern of regional difference demonstrates 4 types,i.e."proliferation type","polarization type","quiescence type"and"collapse type."(4)The driving force for regional difference of domestic tourism in China comes down to 3 aspects:regional socio-economic attribute,regional transport accessibility level and regional development policy.

The spatial-temporal evolution of coherent structures in log law region of turbulent boundary layer

The spatial-temporal evolution of coherent structures （CS） is significant for turbulence control and drag re- duction. Among the CS, low and high speed streak structures show typical burst phenomena. The analysis was based on a time series of three-dimensional and three-component （3D-3C） velocity fields of the flat plate turbulent boundary layer （TBL） measured by a Tomographic and Time-resolved PIV （Tomo TRPIV） system. Using multi-resolution wavelet transform and conditional sampling method, we extracted the intrinsic topologies and found that the streak structures appear in bar-like patterns. Furthermore, we seized locations and velocity information of transient CS, and then calculated the propagation velocity of CS based on spatial-temporal cross-correlation scanning. This laid a foundation for further studies on relevant dynamics properties.

Spatial and Temporal Variations of Pneumoconiosis in the Pearl River Delta Region in 2006–2015

Pneumoconiosis is a restrictive lung disease mostly caused by occupational exposure to dust,including silica dust,asbestos,and other fibers.Inhalable particles smaller than 10μm can enter the bronchioles,injure lung cells,and induce lung fibrosis.This hard-to-cure disease places a substantial burden on patients and society[1].

THE TEMPORAL AND SPATIAL CHARACTERISTICS OF MOISTURE BUDGETS OVER ASIAN AND AUSTRALIAN MONSOON REGIONS

Apparent moisture sink and water vapor transport flux are calculated by using NCAR/NCEP reanalyzed daily data for water vapor and wind fields at various levels from 1980 to 1989.With the aid of EOF analysis method,temporal and spatial characteristics of moisture budgets over Asian and Australian monsoon regions are studied.The results show that there is apparent seasonal transition of moistrue sink and water vapor transport between Asian monsoon region and Australian monsoon region.In winter,the Asian monsoon region is a moisture source,in which three cross-equatorial water vapor transport channels in the 'continent bridge',at 80°E and 40°E～50° transport water vapor to the Australian monsoon region and southern Indian Ocean which are moistrue sinks.In summer,Australian Monsoon region anmd southern Indian Ocean are moistrue sources and by the three cross-equatorial transport channels water vapor is transport to the Asian monsoon region which is a moisture sink.In spring and autumn,ITCZ is the main moisture sink and there is no apparent water vapor transport between Asian monsoon region and Australian monsoon region.

Temporal and Spatial Variation Characteristics of Soil Organic Carbon Content in Cultivated Land of Black Soil Region in Liaoning Province

[Objectives]To study the temporal and spatial variation of SOC content in cultivated land in black soil region in Liaoning Province.[Methods]Through the evaluation and analysis of the research data of this project and the data of the second national soil census,and using GIS technology,this paper studied the temporal and spatial variation characteristics of SOC in the black soil region of Liaoning Province,and provided a basis for improving cultivated land carbon storage and soil organic matter content.[Results]Since 1980,the SOC content in cultivated land in the black soil region in Liaoning Province has generally declined,and the spatial distribution difference has gradually decreased.From 1980 to 2018,the homogeneity of SOC distribution weakened,and the variation in a small range strengthened.The SOC content generally showed the characteristics of increase and decrease,and the changes in the area were scattered.[Conclusions]This study is of great significance to the sustainable utilization of land resources.

Temporal and Spatial Variation Characteristics of Precipitation during Crop Growing Season in Northeast China

[Objective] The aims were to understand variation characteristics of water resources and provide theoretical guidance for the formulation of agricultural irrigation methods.[Method] Taking the precipitation records during crop growing season（from April to September）observed by 177 weather stations from 1971 to 2008 in the three provinces of Northeast China（Heilongjiang,Jilin and Liaoning）as research data,annual change and spatial distribution characteristics of precipitation during crop growing season were analyzed by means of small grid interpolation and climatic trend rate.[Result] The precipitation during crop growing season general exhibited the decreasing trend and the precipitation trend rate was-8.6 mm/10a in Northeast China.In addition,there was lack of rain from 1971 to 1980 and relatively abundant of rain during 1981 and 1990 respectively.Moreover,the precipitation obviously exhibited decreasing trend from 1991 to 2008.But the decreasing trend was inconsistent in spatial distributions,that was,the precipitation slightly increased in relatively rainless areas and obviously decreased in relatively rainy areas.[Conclusion] The areas with obvious decreasing trend of precipitation during crop growing season are the main grain producing zones in Northeast China,so the problem of food production security caused by the precipitation changes should be paid enough attention.

Temporal and Spatial Variation and Distribution Characteristics of Maximum and Minimum Temperature from 1971 to 2008 in Tibet

Based on temperature data of meteorological stations from 1971 to 2008 in Tibet,the temporal and spatial variation of maximum andminimum temperature in Tibet was analyzed.The results showed that both maximum temperature andminimum temperature increased distinctly,the warming amplitude of winter was the highest among the four seasons,and next came spring.The increment ofminimum temperature was visibly over that of maximum temperature,particularlyminimum temperature in winter with significant increment.For spatial variation,maximum temperature in most stations increased except particular stations,while theminimum temperature in all stations rose.In addition,the space variation law ofminimum temperature,being more obvious thanminimum temperature,increased from southeast to northwest with different spatial changes in various seasons.From decadal variation,both maximum andminimum temperature appeared increase from 1970s to the first eight years in the 21st century,and the rise ofminimum temperature was significant greater than maximum temperature.The increase of maximum andminimum temperature was the highest from 2001 to 2008,whereas the lowest in 1970s.

基于GTWR-LightGBM模型的京津冀地区近地面SO_(2)浓度估算

文章利用Sentinel-5P卫星提供的SO_(2)柱浓度数据(TROPOMI-L3 SO_(2))和ERA5再分析气象数据作为估算变量,将能够捕获时空信息的GTWR模型和使用了按叶子生长算法的LightGBM模型组合在一起,构建了GTWR-LightGBM模型,基于该模型对京津冀地区近地面SO_(2)浓度进行估算。结果表明:(1)GTWR-LightGBM模型估算近地面SO_(2)浓度精度最高,十折交叉验证R^(2)、RMSE和MAE分别为0.90、2.88μg/m^(3)和1.93μg/m^(3),优于AdaBoost、GBDT、RF、LightGBM、GTWR、GTWR-Adaboost、GTWR-GBDT和GTWRRF等模型,同时模型在季节尺度上的验证结果均较为良好。(2)在时间分布上,2019年京津冀地区的近地面SO_(2)月均浓度总体呈现先下降后上升的“V”型趋势,SO_(2)浓度月均值在1月达到最高,在7月降到最低,其中5月和6月呈现小幅上升趋势,且2019年该地区近地面SO_(2)浓度存在明显的季节性差异,四季浓度大小趋势为:冬季>春季>秋季>夏季。(3)在空间分布上,SO_(2)浓度总体均表现出局部高污染和南高北低的分布特征,在人口密度大,工业集中的南部平原地区呈现高值状态,在高海拔,人口密度小,工业排放少的北部地区呈现低值状态。

祁连山地区水资源-人口-经济-生态环境系统协调发展的时空演变及预测

利用熵权TOPSIS模型测度2007—2021年祁连山地区30个县域水资源-人口-经济-生态环境系统综合发展水平,采用耦合协调模型分析水资源-人口-经济-生态环境系统的协调度,采用GM(1,1)灰色预测模型预测2022—2031年水资源-人口-经济-生态环境协调发展状况。结果表明:祁连山地区水资源-人口-经济-生态环境系统综合发展水平逐年升高,水资源子系统发展水平呈波动上升趋势,人口子系统发展水平缓慢上升,经济子系统发展起点较低但增速较快;生态环境子系统发展起点相对较高但波动较大,且除水资源子系统外,甘肃片区指标优于青海片区。祁连山地区水资源-人口-经济-生态环境系统耦合度处于高水平耦合状态,协调度等级波动上升已达到中级协调;各地区增速具有异质性,南部增速最快,西北部次之,中部最慢。祁连山地区水资源-人口-经济-生态环境系统协调度呈现稳步上升态势,逐渐由中级协调升至良好协调等级,且甘肃片区协调度略高于青海片区。

基于Spearman-GCN-GRU模型的超短期多区域电力负荷预测

为提升多区域电力负荷的预测精度,聚焦于多区域电力数据的时空相关性分析,提出了一种基于Spearman-GCN-GRU的超短期多区域电力负荷预测模型。该模型通过Spearman相关系数分析不同区域电力负荷的时空相关性,构建Spearman邻接矩阵并输入图卷积神经网络(graph convolutional network,GCN)和门控循环单元(gated recurrent unit,GRU)提取数据中的空间特征和时序特征,最后由多层感知机(multilayer perceptron,MLP)解码输出预测结果。与基于距离邻接矩阵的模型进行对比,验证了SpearmanGCN-GRU模型的可行性。在模型的预测精度上,与传统统计模型和神经网络模型相比,Spearman-GCNGRU模型在通用的评价指标中均取得最优结果。就均方根误差(root mean square error,RMSE)而言,SpearmanGCN-GRU模型与神经网络模型GRU、GCN和深度神经网络(deep neural network,DNN)相比,RMSE指标分别下降了13.90%、11.66%和8.36%,验证了模型具有更好的预测效果。

基于“末端控制-区域协同”的京津冀地区碳减排效应及时空特征分析

近年来,协同推进区域碳减排已被上升为国家重要战略,作为我国最发达经济圈之一的京津冀地区,始终将统筹环境治理作为推动区域协同发展的重点领域。然而,现有研究缺乏从京津冀地区总体视角,通过一致的比较框架来探究3省市碳排放与地区协同发展之间的区域协同减排效应。本研究选用单位国内生产总值(GDP)的碳排放量作为指标,并创新性地在末端控制-区域协同分析框架下,通过对数平均分裂指数(LMDI)方法量化部门末端控制、区域协同减排效应和社会经济发展对碳减排的影响。结果表明,部门末端控制措施对京津冀地区碳减排影响较小,非控制、控制以及基线3种情景下京津冀区域碳排放浓度依次下降,相较非控制情景,后两者降幅分别为0.0727%、25.3763%,区域协同减排效应对于碳减排影响潜力巨大。河北省是京津冀地区区域协同减排效应碳减排重要突破口,且2014—2021年京津冀地区区域协同减排效应带来的碳减排主要归因于产业结构、家庭能源使用水平、能源强度等驱动因素。

Investigating spatio-temporal characteristics and influencing factors for green energy consumption in China

The green transformation of energy consumption is beneficial for promoting green development in China.This study constructed a green energy consumption evaluation index system and measured the green energy consumption levels in 30 provinces of China from 2000 to 2019 using the fuzzy comprehensive evaluation method.This study further employed the spatial Durbin model to examine influencing factors and spillover effects of green energy consumption.The results showed that,temporally,China’s green energy consumption levels had a fluctuating upward trend.While,spatially,the overall levels of green energy consumption in China showed apparent characteristics of“high in the west and low in the east”.In terms of influencing factors,environmental regulations played an important role in promoting green energy consumption in the region,while economic development,opening up,and industrial structure had considerably inhibiting effects.Additionally,economic development,opening up,and industrial structure of neighboring regions showed marked positive spillover effects,while urbanization level and technological innovation showed substantial negative spillover effects.The regional heterogeneity test results showed that environmental regulation and industrial structure rationalization were the important factors for promoting green energy consumption in the eastern region,environmental regulation played an important driving role in the central region,and opening to the outside world and technological innovation helped improve the level of green energy consumption in the western region.

Grassland degradation in the ＂Three-River Headwaters＂ region, Qinghai Province

Supported by MSS images in the mid and late 1970s,TM images in the early 1990s and TM/ETM images in 2004,grassland degradation in the＂Three-River Headwaters＂region （TRH region）was interpreted through analysis on RS images in two time series,then the spatial and temporal characteristics of grassland degradation in the TRH region were analyzed since the 1970s.The results showed that grassland degradation in the TRH region was a continuous change process which had large affected area and long time scale,and rapidly strengthen phenomenon did not exist in the 1990s as a whole.Grassland degradation pattern in the TRH region took shape initially in the mid and late 1970s.Since the 1970s,this degradation process has taken place continuously,obviously characterizing different rules in different regions.In humid and semi-humid meadow region,grassland firstly fragmentized, then vegetation coverage decreased continuously,and finally＂black-soil-patch＂degraded grassland was formed.But in semi-arid and arid steppe region,the vegetation coverage decreased continuously,and finally desertification was formed.Because grassland degradation had obviously regional differences in the TRH region,it could be regionalized into 7 zones, and each zone had different characteristics in type,grade,scale and time process of grassland degradation.

西北五省(区)交通-环境-经济耦合协调发展时空格局

为促进西北地区的区域协调发展,基于西北五省(区)面板数据构建交通-环境-经济耦合协调模型指标体系,并在运用耦合协调模型分析交通-环境-经济耦合协调发展水平时空演变特征的基础上,进一步利用向量自回归VAR模型探究交通-环境-经济三个子系统的相互作用机理。结果表明:西北五省(区)耦合协调发展与交通子系统发展趋势高度一致,二者发展水平较低但均呈差异化提升趋势。交通子系统的发展更加侧重于依赖交通自身发展趋势和基本情况,在经济互联互通方面的作用有待于进一步加强,因此加快交通子系统对其他子系统从消极影响到积极影响的转变是提升西北地区耦合协调发展水平的重中之重。

Changing characteristics and spatial differentiation of spring precipitation in Southwest China during 1961-2012

In this study,we analyze spring precipitation from 92 meteorological stations spanning between 1961 and 2012 to understand temporal-spatial variability and change of spring precipitation over Southwest China.Various analysis methods are used for different purposes,including empirical orthogonal function（EOF） analysis and rotated EOF（REOF） for analyzing spatial structure change of precipitation anomaly,and the Mann-Kendall testing method to determine whether there were abrupt changes during the analyzed time span.We find that the first spatial mode of the precipitation has a domain uniform structure;the second is dominated by a spatial dipole;and the third contains five variability centers.The 2000 s is the decade with the largest amount of precipitation while the 1990 s is the decade with the smallest amount of precipitation.The year-to-year difference of that region is large：the amount of the largest precipitation year doubles that of the smallest precipitation year.We also find that spring precipitation in Southwest China experienced a few abrupt changes：a sudden increase at 1966,a sudden decrease at 1979,and a sudden increase at 1995.We speculate that the spring precipitation will increase gradually in the next two decades.

数字乡村发展水平指标体系构建与实证研究--以河南省2014-2021年18个地级市面板数据为例

【目的】科学量化数字乡村发展水平,有效推进现代信息技术与乡村各领域全面有机融合,助力乡村振兴。【方法】在梳理学界最新研究成果以及实践调研的基础上,基于2014-2021年河南省18个地市面板数据,从乡村数字信息基础、乡村数字经济新业态、农业数字化转型、乡村生活数字化4个维度选取20个指标,构建数字乡村发展水平评价指标体系。综合运用熵权法、TOPSIS法、Kernel密度估计、泰尔指数、Moran’s I等研究方法测度河南省数字乡村发展水平,分析其区域差异及时空演变规律。【结果】(1)从发展水平看,考察期内河南省数字乡村发展水平呈现逐年上升态势,虽然整体发展水平不高,但可持续发展动能强劲。(2)从区域差异看,河南数字乡村发展水平整体差异呈现稳步下降趋势。其中,区域间差异对总体差异的贡献最大,中原城市群与黄淮地区差异最明显,区域内差异表现为中原城市群、豫西豫西南、豫北、黄淮地区依次递减的态势。(3)从时空演变看,四大经济区区域间呈现明显且稳定的正相关,中原城市群地市多表现为高高集聚,而黄淮地区基本表现为低低集聚。【结论】河南省数字乡村发展应该结合省情及区域特征,全面布局、统筹推进、均衡发展、弥合差距、快速提升。

长江经济带土地利用与经济-社会-环境耦合协调研究

[目的]测算长江经济带城市土地利用与经济—社会—环境系统的耦合协调度,并考察其时空分异特征及驱动因素,进而为长江经济带土地可持续利用和区域高质量协调发展提供决策参考。[方法]基于2006—2019年长江经济带108个地级市的面板数据,构建了土地利用与经济—社会—环境系统的指标体系,采用熵权法、耦合协调度模型测算耦合协调度,并借助Dagum基尼系数、莫兰指数和地理加权回归模型进行时空分异特征及驱动因素分析。[结果]2006—2019年长江经济带土地利用与经济—社会—环境耦合协调度由0.309上升至0.477,从轻度失调转入勉强协调。不同区域间的耦合协调度由下游区域向上游区域逐步递减,呈现“东高西低”的空间分布格局。耦合协调度的总体、区域内和区域间差异呈现下降趋势。区域间差异是总体差异的主要原因,其贡献率由43.67%上升至46.88%。耦合协调度的Moran's I值由0.095上升至0.134,具有显著的空间正自相关性,“H—H”集聚区主要分布在下游区域,“L—L”集聚区主要分布在中上游区域。地形起伏和坡度呈现负向驱动,城镇化水平和外商直接投资呈现正向驱动,人口密度呈现两级化驱动特征。[结论]长江经济带土地利用与经济—社会—环境的耦合协调度存在时空异质性,应充分考虑区域特征制定差异化的土地利用政策。

中国城市碳排放绩效:动态分解、空间差异与影响因素

以非径向方向距离函数为框架,构造全要素碳排放绩效指数对中国2006—2019年城市碳排放治理绩效进行测度。在此基础上从经济含义、跨期动态变化、区域均衡等层面对全要素碳排放绩效指数进行多维分解,检验中国城市碳排放绩效的影响因素。结果表明:第一,样本期内全国城市平均全要素碳排放绩效指数总体呈波动上升态势,动态分解结果显示,中国各地的平均碳排放绩效水平不断改进,创新效应对其贡献逐年增大但赶超效应贡献不足;第二,空间分异方面,珠三角、长三角、粤闽浙沿海、长江中游等东部地区城市群不仅平均碳排放绩效水平普遍较高,且碳排放绩效的增长速度较快,中西部地区仅成渝城市群碳排放绩效表现较好,中原、京津冀等城市群近年来碳排放绩效的改善速度较快;第三,基尼系数测度及其分解显示,近年中国城市碳排放绩效指数的分异程度逐步加深,分异成因主要为城市群组间差异,城市群内部差异贡献度较低;第四,Lasso分析及双固定面板模型分析结果显示,经济发展水平、清洁能源使用、金融发展、绿色环保和科技支持能够有效改善城市层面的碳排放绩效,能源消耗强度和第二产业就业人员比重对碳排放绩效具有负面影响;最后,城市群因子探测结果显示,各城市群间的驱动因子存在一定差异。