Spatiotemporal pattern of climate change in the China-Myanmar Economic Corridor from 1901 to 2018

The China-Myanmar Economic Corridor(CMEC) is an important part of China's Belt and Road Initiative and an important area for global ecology and biodiversity. In this study, the annual and seasonal spatiotemporal patterns of temperature and precipitation in the CMEC over the past century were investigated using linear tendency estimation, the Mann-Kendall mutation test, the T-test, and wavelet analysis based on the monthly mean climatic data from 1901 to 2018 released by the Climatic Research Unit(CRU) of the University of East Anglia, UK. The results show that the CMEC demonstrated a trend of warming and drying over the past 100 years, and the rate of change in Myanmar was stronger than that in Yunnan Province of China. The warming rate was 0.039 ℃/10a. Precipitation decreased at a rate of -6.1 mm/10a. From the perspective of spatial distribution, temperature was high in the central and southern, low in the north of the CMEC, and the high-temperature centers were mainly distributed in the southern plain and river valley. Precipitation decreased from west to east and from south to north of the CMEC. From the perspective of the rate of change, warming was stronger in central and northern CMEC than in southern and northeastern CMEC. The rate of precipitation decline was stronger in the central and western regions than in the eastern region. This study provides a scientific reference for the CMEC to address climate change and ensure sustainable social and economic development and ecological security.

Spatiotemporal Pattern of Cultivated Land Pressure and Its Influencing Factors in the Huaihai Economic Zone, China

Cultivated land pressure represents a direct reflection of grain security. Existing relevant studies rarely approached the spatiotemporal pattern of cultivated land pressure or the spatial heterogeneity of its influencing factors from the level of economic zones.Taking the Huaihai Economic Zone(HEZ), China for case analysis, this study investigated the spatiotemporal pattern of cultivated land pressure in diverse periods from 2000 to 2018 based on a modified cultivated land pressure index and spatial correlation models. On this basis, it explored the influencing factors of the spatial differentiation of cultivated land pressure in the late stage of the study using geographical detector as well as multi-scale geographically weighted regression model. The results indicated that: 1) in the study period, the global cultivated land pressure index of the study area decreased gradually, but cultivated land pressure increased locally in a significant way, especially in the central and southern Shandong Province;2) the spatial pattern of cultivated land pressure manifested global clustering features. Hot and secondary-hot spots presented a narrowing and clustering trend, whereas cold and secondary-cold spots manifested a spreading and clustering trend;3) average slope, the proportion of non-grain crops, population urbanization rate, and multiple cropping index have significant effects on the spatial differentiation of cultivated land pressure. The former three factors were positively correlated with cultivated land pressure, and the last factor was negatively correlated with cultivated land pressure;and 4) the amount of cultivated land has increased in the central and southern Shandong Province through land consolidation which, nonetheless, failed to improve the grain production. In regards to major grain producing areas similar to the HEZ in China, the authors suggest that great importance should be given to the balance of the quality and quantity of cultivated land, the optimization of agricultural production factors and the rational control of non-grain crops, thus providing a powerful guarantee for grain security in China.

Co-occurrence Patterns of Above-ground and Below-ground Mite Communities in Farmland of Sanjiang Plain, Northeast China

One of the fundamental questions in community ecology is whether communities are random or formed by deterministic mechanisms. Although many efforts have been made to verify non-randomness in community structure, little is known with regard to co-occurrence patterns in above-ground and below-ground communities. In this paper, we used a null model to test non-randomness in the structure of the above-ground and below-ground mite communities in farmland of the Sanjiang Plain, Northeast China. Then, we used four tests for non-randomness to recognize species pairs that would be demonstrated as significantly aggregated or segregated co-occurrences of the above-ground and below-ground mite communities. The pattern of the above-ground mite commu- nity was significantly non-random in October, suggesting species segregation and hence interspecific competition. Additionally, species co-occurrence patterns did not differ from randomness in the above-ground mite community in August or in below-ground mite com- munities in August and October. Only one significant species pair was detected in the above-ground mite community in August, while no significant species pairs were recognized in the above-ground mite community in October or in the below-ground mite communities in August and October. The results indicate that non-randomness and significant species pairs may not be the general rule in the above-ground and below-ground mite communities in farmland of the Sanjiang Plain at the fine scale.

Spatiotemporal patterns of non-point source nitrogen loss in an agricultural catchment

Non-point source nitrogen loss poses a risk to sustainable aquatic ecosystems. However, non-point sources, as well as impaired river segments with high nitrogen concentrations, are difficult to monitor and regulate because of their diffusive nature, budget constraints, and resource deficiencies. For the purpose of catchment management, the Bayesian maximum entropy approach and spatial regression models have been used to explore the spatiotemporal patterns of non-point source nitrogen loss. In this study, a total of 18 sampling sites were selected along the river network in the Hujiashan Catchment. Over the time period of 2008e2012, water samples were collected 116 times at each site and analyzed for non-point source nitrogen loss. The morphometric variables and soil drainage of different land cover types were studied and considered potential factors affecting nitrogen loss. The results revealed that, compared with the approach using the Euclidean distance, the Bayesian maximum entropy approach using the river distance led to an appreciable 10.1% reduction in the estimation error, and more than 53.3% and 44.7% of the river network in the dry and wet seasons, respectively, had a probability of non-point source nitrogen impairment. The proportion of the impaired river segments exhibited an overall decreasing trend in the study catchment from 2008 to 2012, and the reduction in the wet seasons was greater than that in the dry seasons. High nitrogen concentrations were primarily found in the downstream reaches and river segments close to the residential lands. Croplands and residential lands were the dominant factors affecting non-point source nitrogen loss, and explained up to 70.7%of total nitrogen in the dry seasons and 54.7% in the wet seasons. A thorough understanding of the location of impaired river segments and the dominant factors affecting total nitrogen concentration would have considerable importance for catchment management.

Assembly and co-occurrence patterns of rare and abundant bacterial sub-communities in rice rhizosphere soil under short-term nitrogen deep placement

Nitrogen(N)deep placement has been found to reduce N leaching and increase N use efficiency in paddy fields.However,relatively little is known how bacterial consortia,especially abundant and rare taxa,respond to N deep placement,which is critical for understanding the biodiversity and function of agricultural ecosystem.In this study,lllumina sequencing and ecological models were conducted to examine the diversity patterns and underlying assembly mechanisms of abundant and rare taxa in rice rhizosphere soil under different N fertilization regimes at four rice growth stages in paddy fields.The results showed that abundant and rare bacteria had distinct distribution patterns in rhizosphere samples.Abundant bacteria showed ubiquitous distribution;while rare taxa exhibited uneven distribution across all samples.Stochastic processes dominated community assembly of both abundant and rare bacteria,with dispersal limitation playing a more vital role in abundant bacteria,and undominated processes playing a more important role in rare bacteria.The N deep placement was associated with a greater influence of dispersal limitation than the broadcast N fertilizer(BN)and no N fertilizer(NN)treatments in abundant and rare taxa of rhizosphere soil;while greater contributions from homogenizing dispersal were observed for BN and NN in rare taxa.Network analysis indicated that abundant taxa with closer relationships were usually more likely to occupy the central position of the network than rare taxa.Nevertheless,most of the keystone species were rare taxa and might have played essential roles in maintaining the network stability.Overall,these findings highlighted that the ecological mechanisms and co-occurrence patterns of abundant and rare bacteria in rhizosphere soil under N deep placement.

Spatio-Temporal Variations in Co-Occurrence Patterns of Fish Communities in Haizhou Bay, China: Null Model Analysis

Co-occurrence pattern of fish species plays an important role in understanding the spatio-temporal structure and the stability of fish community.Species coexistence may vary with time and space.The co-occurrence patterns of fish species were examined using the C-score under fixed-fixed null model for fish communities in spring and autumn over different years in the Haizhou Bay,China.The results showed that fish assemblages in the whole bay had non-random patterns in spring and autumn over different years.However,the fish co-occurrence patterns were different for the northern and southern fish assemblages in spring and autumn.The northern fish assemblage showed structured pattern,whereas the southern assemblage were randomly assembled in spring.The co-occurrence patterns of fish communities were relatively stable over different years,and the number of significant species pairs in northern assemblage was more than that in the southern assemblage.Environmental heterogeneity played an important role in determining the distributions of fish species that formed significant species pairs,which might affect the co-occurrence patterns of northern and southern assemblages further in the Haizhou Bay.

Spatiotemporal Patterns of Urban PM2.5 Pollution in China

Air pollution is one of the top environmental concerns and causes of deaths and variousdiseases worldwide. In this paper, PM2.5 observation data at 1,497 automatic air quality-monitoringstations in 367 cities of China in 2015 were utilized, and the study on spatiotemporal distribution of PM2.5concentration found that the average annual concentration of PM2.5 in urban China in 2015 was 49.74 μg/m3and exceeded the annual average limit in 287 cities. PM2.5 concentrations were highest in winter and lowestin summer in most cities, but it reached the highest in spring in the cities around Taklimakan Desert. Therewere 320 fi ne days in 2015 and the maximum PM2.5 was prone to appear at night, the minimum was usuallyin the afternoon, but in the early morning in Lhasa, and the minimum in winter was even in the earlymorning, midday and afternoon in some cities. Higher concentrations of PM2.5 were found in the EastChina Plain and the cities around Taklimakan Desert, preceded by the Yangtze River Delta economic zone,Chengdu-Chongqing economic zone and Harbin-Changchun megalopolis, while the lower values coveredthe northwestern region of Xinjiang, Heilongjiang Xing’an Mountains region, northeast high latitudes ofInner Mongolia, southwest high altitudes in the border area of Sichuan, Yunnan, Qinghai-Tibet Plateau andthe southeast coastal areas.

Spatial and temporal patterns of the sensitivity of radial growth response by Picea schrenkiana to regional climate change in the Tianshan Mountains

Climate change significantly impacts forest ecosystems in arid and semi-arid regions.However,spatiotemporal patterns of climate-sensitive changes in individual tree growth under increased climate warming and precipitation in north-west China is unclear.The dendrochronological method was used to study climate response sensitivity of radial growth of Picea schrenkiana from 158 trees at six sites during 1990-2020.The results show that climate warming and increased precipitation significantly promoted the growth of trees.The response to temperature first increased,then decreased.However,the response to increased precipitation and the self-calibrating Palmer Drought Severity Index(scPDSI)increased significantly.In most areas of the Tianshan Mountains,the proportion of trees under increased precipitation and scPDSI positive response was relatively high.Over time,small-diameter trees were strongly affected by drought stress.It is predicted that under continuous warming and increased precipitation,trees in most areas of the Tianshan Mountains,especially those with small diameters,will be more affected by precipitation.

Stabilizing Spiral and Spatiotemporal Chaos in External Centric Field

In this paper, a scheme of spatial perturbation is introduced into a class of excitable media, which are described by two-dimensional partial-differential equation models. Inertial acentric force （or centrlpetal force）, which is generated by circumgyrating the whole system vs. a right axis, is used to disturb the system. The whole system becomes homogeneous as soon as the spatial perturbation is imposed on even when the noise is in consideration. The principle of this scheme is confirmed based on the theory of hopf bifurcation and numerical simulation.

Spatiotemporal Evolution of Waterlogging Events in Eastern China from 1961 to 2016

In this study, based on the data on the frequency of waterlogging events and the number of waterlogging days of 1,638 stations from 1961 to 2016, a variety of mathematical statistics methods were used to analyze the spatiotemporal evolution of waterlogging events in eastern China. The results showed that:① In terms of time, the annual frequency of waterlogging events and the number of waterlogging days in eastern China in 1961–2016 showed an increasing trend despite of fluctuations. In the interdecadal changes, the highest frequency of waterlogging events and the greatest number of waterlogging days occurred in the 1990s, and from the 1960s to the 1980s, the frequency of waterlogging events and the number of waterlogging days in eastern China showed a decreasing trend. There were 6-year and 30-year periodic variations in the frequency of waterlogging events and the number of waterlogging days in eastern China, and mutations occurred in 1991.② In terms of space, from 1961 to 2016, the areas with high frequency of waterlogging events in various years in eastern China were mainly South China, western and southern Yunnan, northern Jiangsu, southern Zhejiang, northern Fujian, junction areas between Hunan and Chongqing, northern Sichuan, and eastern Liaoning.③ In the spatial distribution of change trends and fluctuation characteristics, the frequency of waterlogging events and the number of waterlogging days in eastern China increased significantly in the southeastern coastal areas from 1961 to 2016, and the fluctuations of the frequency of waterlogging events and the number of waterlogging days in eastern China from 1961 to 2016 presented a spatial variation pattern of low in the southwest and high in the northwest.

四川省大豆生产格局变化及驱动因素研究

四川省是我国13个粮食主产区之一,也是我国大豆种植的新兴地区和西南产区的重要组成,研究大豆生产格局对四川省落实粮食安全战略、推动西南地区大豆产业发展具有重大意义。文章基于2000—2020年四川省183个区市县的面板数据,运用空间基尼指数、地理集中度系数、空间转移系数、探索性空间数据分析、最优地理探测器分析了大豆生产的时空格局变化及驱动因素。研究结果发现:1)2000—2020年,四川省大豆产能波动上升,空间分布极不均衡,聚集水平逐步上升,并逐步向川中丘陵区集中;2)大豆生产存在较强的正向空间相关性,总体表现为高-高聚集和低-低聚集;3)资源要素、比较收益、地理气候、经济社会等因素对大豆生产格局变化的影响均高度显著,且呈现非线性增强、双因子增强的交互效应。资源要素投入、比较收益、海拔高程长期以来对大豆生产格局的影响较为显著且呈波动上升趋势,气温、乡村家庭规模的影响力提升较快,交通条件、地区GDP的影响力则总体呈下降趋势,耕作制度长期以来驱动力最弱。基于此,四川省大豆生产应着力破解耕地资源细碎化与劳动力短缺等资源环境约束,大力发展生产性服务业,全面提升大豆生产机械化水平。通过强化科技创新提升川豆单产,并进一步优化大豆生产、农机、服务、保险等环节的政策保障。同时,应重点关注气候变化引发的干旱等自然风险,健全农业领域自然灾害风险预警与防范机制,以进一步强化大豆产业的综合风险抵御能力。

城市地区场次降雨时空展布方法研究

受气候变化和城市规模不断扩张等因素影响,城市地区降雨过程的时空动态性愈发明显,通常采用的点、面雨量等表达方式难以体现这种时空动态性。随着降雨观测技术的进步,大多城市积累了长序列降雨观测数据,其中蕴含了丰富的降雨时空过程信息,为预报降雨或设计降雨的时空展布提供了可能。设计了一套降雨时空展布方法,包括数据收集、标准化处理、降雨场次划分、时空模式提取、标准网格插值、时空展布等环节,并提出每个环节的处理步骤和关键问题。以北京市为例,对该技术方法进行了验证,选择了12 h、24 h、72 h 3个历时的场次降雨,提取的时空模式和展布结果表达出了场次降雨的时空动态性,并与历史的降雨过程表现出很好的匹配性。表明该方法可用于城市地区降雨典型模式提取,以及降雨过程的时空展布。该方法利用历史降雨数据提取降雨展布模板,输入场次降雨(或预报降雨)的总雨量,得到该场次降雨的时空分布过程,展布结果可为洪水预报提供更为准确的降雨输入条件。

空间转向视角下的南京市博物馆时空格局演化及其影响因素研究

为探明南京市博物馆的时空演化规律,文章以多源数据获取的南京市101家博物馆为研究对象,通过梳理博物馆发展历程,综合运用数理统计、GIS空间分析方法以及Spearman相关性分析和地理探测器模型对其时空格局演化及影响因素进行探究。研究表明:(1)南京市博物馆发展呈现明显的阶段特征,9类博物馆呈现规模化且多元化发展态势。(2)南京市博物馆主要集聚于中心城区及秦淮河沿岸,尽管在空间上有由中心向外围扩散的趋势,但空间上仍呈现明显的“核心-边缘”特征;对各乡镇街道博物馆进行聚类和异常值分析的结果表明,聚类态势的高值区主要在中心城区;全局分布具有空间自相关特性,冷热点区域变动显著,热点区沿中心城区向东南和西北不断延伸和扩大。(3)博物馆空间分布的类型和格局基本上是由历史资源禀赋的地域差异所决定的,在此基础上,区域经济发展水平、交通通达程度、人口因素,以及政策因素进一步强化了博物馆的空间分异。最后,结合空间转向背景,从宏观、中观和微观3个层面提出调控博物馆空间布局的建议,以期进一步促进博物馆与城市空间的高度融合。

福建省县域收缩城市的识别与格局研究

从综合视角,构建集人口、经济、社会保障和投资消费4个维度的指标体系,对福建省县级行政单元进行收缩城市的识别和类型划分,并分析其时空演变特征。研究发现:(1)福建省人口单一指标收缩的城市数量较多,形成了闽中、闽西2个人口收缩带;(2)福建省综合指标收缩的城市已不少,呈现出阶段性和内聚性特征,2000—2010年有92.7%的县市区表现为综合收缩,2010—2020年略有下降,有72.7%的县市区表现为综合收缩;(3)研究期间福建省收缩城市数量呈递减趋势,出现了增长型、收缩型、明显收缩型和严重收缩型4种收缩类型,尚未出现衰败型;(4)福建省收缩城市空间分布格局与人口收缩格局类似,重点分布在福建省中西部地区,东部只有平潭县和安溪县出现过收缩情况。基于综合收缩结果发现,人口流失成为造成福建省县级行政单元城市收缩的核心因素,地方财政、产业结构、消费活力等因素也进一步加剧了城市收缩的进程。

中国与“一带一路”国家粮食贸易驱动的虚拟水流动时空格局及其节水效益

粮食贸易是“一带一路”国家经济贸易合作中至关重要的部分之一,可以带动粮食生产全过程所需的虚拟水流动。将单位粮食产品虚拟水量纳入粮食贸易数据系统,进而揭示中国与“一带一路”国家间粮食贸易驱动的虚拟水流动时空格局,并测算粮食贸易所实现的全局性节水效益。研究发现:(1)研究时段中国粮食贸易所驱动的虚拟水净进口量逐年上升,净进口结构以稻米和玉米为主。(2)中国粮食虚拟水进口来源国结构稳定但相对单一,建议粮食贸易对象多元化;粮食虚拟水出口量较少,出口对象国相对分散。(3)结合水资源禀赋可以看出,在进口不可避免的前提下,中国考虑进口地区水资源禀赋后的粮食进口虽然未显示水资源节约,但浪费量大幅减少;粮食出口稀缺节水量为正,具有一定的节水效益。基于研究结果,提出我国可通过降低粮食进口国集中度,优化粮食贸易空间布局,在保障粮食安全的同时,通过虚拟水贸易实现水资源有效节约,拓展节水的思路与路径。

全球研发投入2500强中国企业聚集强度影响因素及其作用机制

研究全球研发投入2500强中国企业的研发经费投入影响因素有助于揭示企业战略和决策的动因,从而为企业管理和政策制定提供理论支持。以欧盟委员会发布的全球研发投入2500强中国企业作为样本,运用首位度、基尼系数、全局空间自相关、局部空间自相关、核密度、时空地理加权回归(GTWR)模型等指标和模型,分别从人员和经费两方面探讨其失控分布特征,并进一步研究政府支持、研发环境、人均生产总值和交通条件对研发投入与企业聚集强度之间的作用机制。结果发现:全球研发投入2500强中国企业呈现出“东南多、西北少”的典型特征;研发经费集中在少数高投入的领域或机构中,而研发人员的空间聚集性较强,存在一定集聚现象;政府R&D经费内部支出与研究与开发机构数为影响企业数量的主导影响因子。为此,政府需要关注企业集聚过程中可能导致的人才和资源不均衡分布问题,鼓励企业加强对研发人员的培训与支持,提高其整体素质和分布均衡性。

中国省域蔬菜生产集聚格局演变及驱动因素研究

中国是世界上最大的蔬菜生产国和消费国,蔬菜已成为人们日常饮食最重要的组成部分,同时也是重要的农业经济作物。基于2002-2020年中国省域的蔬菜产量数据,运用标准差椭圆和空间自相关、地理探测器等方法,分析不同尺度下的蔬菜生产时空格局演变,探讨不同分区下的省域蔬菜生产时空格局演变影响因素。结果表明:2002-2020年中国蔬菜产量呈现波动增长的趋势,蔬菜生产区域差异较大,中部和华南产区的单产最高、东北产区单产最低。蔬菜生产较低产省份的数量明显减少,全国蔬菜生产重心由以河南为重心逐渐向西南(湖北)方向偏移。全国蔬菜生产格局基本吻合人口密度分界线(胡焕庸线),胡焕庸线两侧蔬菜生产水平差异存在逐渐缩小趋势。蔬菜高产区位于以山东省为核心的黄淮海平原及其周边省份。中国省域蔬菜产量时空分异的影响因素具有显著差异。全国层面与东部地区的蔬菜生产影响因素基本一致,社会经济因素是最重要的影响因素,与西部地区存在明显差异。西部地区自然地理环境和蔬菜生产现代化水平成为其最重要的影响因素。研究结果可为合理调整中国蔬菜生产空间布局,充分发挥不同区域的资源优势,促进蔬菜生产高质量发展提供科学依据。

基于动态稳定性验证和CA-Markov预测的耕地时空演变特征--以赣榆区为例

为阐明耕地变化动态稳定性验证的重要性,预测“十四五”目标年(2025年)与远景目标年(2035年)的耕地变化,本研究运用耕地面积变异系数、地理集中指数、不平衡指数及趋势分析法,从耕地数量、空间分布与空间发展趋势三个方面,对江苏省连云港市赣榆区耕地变化的动态稳定性进行验证,并运用CA-Markov模型对未来不同政策情境下的耕地变化情况进行模拟。结果表明,2009-2016年赣榆区耕地总量持续下降,未存在较大反复与波动,耕地空间分布较为均衡,耕地占用与补充的空间发展趋势较为连续,总体上具有较高的动态稳定性,符合运用CA-Markov模型的前提条件。预测在各种政策情境下,2025年之前赣榆区将经历快速的耕地非农化过程,至2035年耕地减少的速率有所放缓,具有区位优势的赣榆北部地区将是未来耕地非农化的重点区域,耕地将逐渐向南部内陆地区转移。研究表明,对耕地变化的动态稳定性进行验证可以有效保证CA-Markov模型的模拟精度,赣榆区未来的耕地保护形势不容乐观,应合理协调经济发展与耕地保护之间的关系,保障社会、生态与粮食安全。

促进各民族交往交流交融有形有感有效——读《图案与仪式:融合发展中的云南多民族文化》

时空意识是各民族文化和精神的基本符号,要理解一个民族的文化,首先要从时空观念入手;而一个民族的时空观念往往与其民族的图案或各种仪式展演有关。《图案与仪式:融合发展中的云南多民族文化》正是从云南各少数民族的时空意识入手,通过自己的“看”与“听”精心绘制了各民族共同筑就的“七彩云南”的空间之美。

闽三角城市群景观生态风险时空演变分析

【目的】闽三角城市群等沿海经济发达地区在土地利用演化过程中面临生态功能退化、生态空间碎片化的风险。揭示闽三角城市群土地利用与景观格局演化规律,为闽三角城市群生态空间管控优化与土地资源合理配置提供科学参考。【方法】以2000—2020年土地利用变化数据为基础,分析闽三角城市群的土地利用动态度、土地利用类型转移矩阵等土地利用变化特征,明确景观格局变化特征,最后利用景观格局指数构建景观生态风险评价模型,获取景观生态风险时空分布特征,并识别出城市群景观生态风险空间聚集的冷热点。【结果】2000—2020年,闽三角城市群土地利用类型转移的重点是耕地向林地、建设用地转移,景观生态格局破碎化程度加重,景观生态风险等级先降低再升高。厦门、漳州、泉州三市的景观生态风险分别呈现“稳定可控”“轻度失控”和“基本可控”的特征,“低-低”和“高-高”聚集类型分别分布在区域西北内陆和东南沿海地区。【结论】基于景观生态风险评估模型的总体分析方法,实现了闽三角城市群土地利用空间信息的定量化表达,并基于景观生态风险时空分布特征及空间集聚冷热点识别结果,有效揭示了研究区域景观生态风险的关联图式及分异规律,为闽三角城市群化解景观生态风险提供技术支撑。