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1.
为了探究森林植物叶片功能属性的地理格局及其影响因素,在2013年7-8月期间系统调查了中国东部南北样带9个森林生态系统的847种植物的叶片面积(LA)、叶片厚度(LT)、比叶面积(SLA)和叶片干物质含量(LDMC),并结合群落结构计算了各属性的群落加权平均值(LACWM、SLACWM、LTCWM和LDMCCWM)。结果显示:847种植物的LA、LT、SLA和LDMC的平均值(±标准误)分别为2860.01±135.37 mm2、0.17±0.003 mm、20.15±0.43 m2 kg-1和 316.73±3.81 mg g-1。SLA和LDMC表现出了明显的纬度格局,随着纬度增加,SLA逐渐增加,LDMC降低;然而,LA和LT沿纬度的变化趋势不明显(R2 = 0.02 ~ 0.06)。不同植物类型之间叶片属性的差异是影响LA、LT、SLA和LDMC空间变化的主要因素;叶片功能属性的群落加权值表现出了更加明显的纬度分布格局(R2 = 0.46 ~ 0.71),这主要受到了气候因素和土壤N含量的影响。本文结果完善了中国区域森林生态系统叶片功能属性地理分布的数据库,同时强调了在研究植物属性空间格局时,考虑群落结构在尺度扩展中的重要性。  相似文献   

2.
探究草地生态系统碳储量及其驱动因素对实现双碳目标具有重要意义,藏北高原作为我国重要的草地生态系统,其碳储量现状,空间格局以及驱动因素仍存在很大的争议。本文基于藏北高原150个实测样点数据,通过克里金插值和统计方法,评估分析了藏北高原草地生态系统的地上生物量碳密度、地下30 cm深度根系碳密度和土壤碳密度及其空间分布,以及各碳库的主要影响因素。结果表明:藏北高原地上生物量碳密度平均为0.038 kg C m-2,地下生物量碳密度平均为0.284 kg C m-2,土壤碳密度值最大,平均为7.445 kg C m-2。藏北高原草地生态系统总碳储量约为4.08 Pg C,其中植被碳库0.58 Pg C(包括地上生物量和地下生物量),土壤碳库2.58 Pg C (其余分布在裸地中),碳储量分布格局呈现出从东南向西北递减趋势。植被碳库0.58 Pg C(包括地上生物量和地下生物量),约占青藏高原植被碳库的28.29%;土壤碳库2.58 Pg C,约占青藏高原土壤碳库的26.60%。降水、温度和土壤质地均影响生态系统碳储量,其中降水...  相似文献   

3.
Analysis of casualties due to landslides from 2000 to 2012 revealed that their spatial pattern was affected by terrain and other natural environmental factors, which resulted in a higher distribution of landslide casualty events in southern China than in northern China. Hotspots of landslide-generated casualties were in the western Sichuan mountainous area and Yunnan-Guizhou Plateau region, southeast hilly area, northern part of the loess hilly area, and Tianshan and Qilian Mountains. However, local distribution patterns indicated that landslide casualty events were also influenced by economic activity factors. To quantitatively analyse the influence of natural environment and human-economic activity factors, the Probability Model for Landslide Casualty Events in China(LCEC) was built based on logistic regression analysis. The results showed that relative relief, GDP growth rate, mean annual precipitation, fault zones, and population density were positively correlated with casualties caused by landslides. Notably, GDP growth rate ranked only second to relative relief as the primary factors in the probability of casualties due to landslides. The occurrence probability of a landslide casualty event increased 2.706 times with a GDP growth rate increase of 2.72%. In contrast, vegetation coverage was negatively correlated with casualties caused by landslides. The LCEC model was then applied to calculate the occurrence probability of landslide casualty events for each county in China. The results showed that there are 27 counties with high occurrence probability but zero casualty events. The 27 counties were divided into three categories: poverty-stricken counties, mineral-rich counties, and real-estate overexploited counties; these are key areas that should be emphasized in reducing landslide risk.  相似文献   

4.
森林是陆地生态系统的重要组分,为人类社会提供着多种多样的服务产品。明确不同类型森林生态系统服务的空间特征和驱动机制对优化森林资源管理和提升服务综合效益具有重要意义。基于InVEST模型、CASA模型和GIS技术对赣江流域森林生态系统固碳、蓄积量、水源供给和土壤保持4种服务进行了价值评估和空间制图,并分析了各类自然和社会-经济因子梯度变化与生态系统服务生产之间的联系。结果表明:赣江流域4种森林生态系统服务具有空间异质性。赣江流域周边山地和高丘区域固碳和蓄积量服务较高,林型以阔叶林和竹林为主;水源供给服务较高的区域则为赣江流域东北部,林型以松林和杉木林为主;土壤保持服务空间分布较离散,赣江流域东北部区域略高于西南部区域。生态系统服务是自然过程和人类活动共同作用的结果:随海拔或坡度增加,人类活动干扰减少,森林固碳和蓄积量服务增加,但水源供给和土壤保持服务减小;随区域人均GDP增加或总人口减少,森林固碳和蓄积量服务表现出增加趋势。未来还需进一步评估各类自然和社会-经济因子对不同类型生态系统服务的限制作用和格局影响,以更好地应对区域生态问题。  相似文献   

5.
Understanding the spatial variation in annual actual evapotranspiration(AET) and its influencing factors is crucial for a better understanding of hydrological processes and water resources management. By synthesizing ecosystem-level observations of eddy-covariance flux sites in China(a total of 61 sites), we constructed the most complete AET dataset in China up to now. Based on this dataset, we quantified the statistic characteristics of AET and water budgets(defined as the ratio of AET to annual mean precipitation(MAP), AET/MAP) of terrestrial ecosystems in China. Results showed that AET differed significantly among both different vegetation types and climate types in China, with overall mean AET of 534.7±232.8 mm yr-1. AET/MAP also differed significantly among different climate types, but there were no distinct differences in AET/MAP values across vegetation types, with mean AET/MAP of 0.82±0.28 for non-irrigated ecosystems. We further investigated how the main climatic factors and vegetation attributes control the spatial variation in AET. Our findings revealed that the spatial variation of AET in China was closely correlated with the geographical patterns of climate and vegetation, in which the effects of total annual net radiation(Rn), MAP and mean annual air temperature(MAT) were dominant. Thus, we proposed an empirical equation to describe the spatial patterns of AET in China, which could explain about 84% of the spatial variation in AET of terrestrial ecosystems in China. Based on the constructed dataset, we also evaluated the uncertainties of five published global evapotranspiration products in simulatingsite-specific AET in China. Results showed that large biases in site-specific AET values existed for all five global evapotranspiration products, which indicated that it is necessary to involve more observation data of China in their parameterization or validation, while our AET dataset would provide a data source for it.  相似文献   

6.
基于MCD64A1过火迹地产品、土地覆盖、植被指数和气候等数据,采用空间统计分析和相关分析方法研究了 2001-2017年蒙古东部野火时空动态及其影响因素.结果表明:(1)4-6月是野火发生最主要的时段,10月野火灾害也较严重,特别集中于年内第107-127、145-189、279-301 日 3个时段;2001-20...  相似文献   

7.
Comprehensive information on geographic patterns of leaf morphological traits in Chinese forests is still scarce.To explore the spatial patterns of leaf traits,we investigated leaf area(LA),leaf thickness(LT),specific leaf area(SLA),and leaf dry matter content(LDMC) across 847 species from nine typical forests along the North-South Transect of Eastern China(NSTEC) between July and August 2013,and also calculated the community weighted means(CWM) of leaf traits by determining the relative dominance of each species.Our results showed that,for all species,the means(± SE) of LA,LT,SLA,and LDMC were 2860.01 ± 135.37 mm2,0.17 ± 0.003 mm,20.15 ± 0.43 m2 kg–1,and 316.73 ± 3.81 mg g–1,respectively.Furthermore,latitudinal variation in leaf traits differed at the species and community levels.Generally,at the species level,SLA increased and LDMC decreased as latitude increased,whereas no clear latitudinal trends among LA or LT were found,which could be the result of shifts in plant functional types.When scaling up to the community level,more significant spatial patterns of leaf traits were observed(R2 = 0.46–0.71),driven by climate and soil N content.These results provided synthetic data compilation and analyses to better parameterize complex ecological models in the future,and emphasized the importance of scaling-up when studying the biogeographic patterns of plant traits.  相似文献   

8.
土壤氮磷钾和土壤有机质明显影响森林生长。但是,这些土壤特性具有空间异质性,这使得进行可持续森林经营变得更加复杂。因此,必须深入了解土壤氮磷钾和有机质的空间分布及其变异状况。在本研究中,我们在中国广西壮族自治区西南部的热带林业实验中心,布设了181个样点并进行了采样,应用地统计学方法研究了土壤中氮磷钾和有机质的空间变异性。块金值与基台值的比值表明土壤中氮具有很强的空间依赖性,主要受内在因素影响(如土壤质地、母质、植被类型和地形),而土壤中有机质、磷钾具有中等的空间依赖性,受内在因素和外在因素(如栽培技术、施肥和种植模式)共同影响。在土壤中氮磷钾和有机质的空间变异性的基础上,本研究采用普通克里格方法进行空间插值,制作了土壤氮磷钾和有机质空间分布图。模型验证表明,土壤性质空间分布图能够可靠地指导森林经营活动。  相似文献   

9.
Land circulation is an important measure that can be utilized to enable agricultural management at a moderate scale.It is therefore imperative to explore spatiotemporal changes in land circulation and the factors that drive these variations in order to maintain and increase the vitality of the land rental market.An initial analysis of spatiotemporal patterns in land circulation is presented in this study on the basis of data from 169,511 farm households between 2003 and 2013.The rural fixed observation point system advocated by the Chinese Ministry of Agriculture was utilized for this analysis,and Heckman two-stage models were developed and estimated in order to identify the drivers of regional differences in land circulation at the national scale and at the levels of different terrains.The results of this study show that the rate of land circulation in China rose from 15.09% to 25.1% over the course of the study period,an average rate of 0.8%.More specifically,data show that the rate of land circulation in the south of China has been higher than in the north,that the average land rental payment was 4256.13 yuan per ha,and that 55.05% of households did not pay such a fee during the land circulation process.In contrast,the average rent obtained was 3648.45 yuan per ha nationally even though 52.63% of households did not obtain any payments from their tenants.The results show that land quality,geographic location,transaction costs,and household characteristics have significantly affected land circulation in different regions of China.Specifically,the marginal effects of land quality and geographic location were larger in the plain regions,while transaction cost was the key factor influencing land circulation in the hilly and mountainous regions.The signal identified in this study,rent-free land circulation,is indicative of a mismatch that has led to the marginalization of mountainous regions and higher transaction costs that have reduced the potential value of land resources.Thus,as the opportunity cost of farming continues to rise across China,the depreciation of land assets will become irreversible and the phenomenon of land abandonment will become increasingly prevalent in hilly and mountainous regions in the future.The transaction costs associated with the land rental market should be reduced to mitigate these effects by establishing land circulation intermediaries at the township level,and the critical issues of land abandonment and poverty reduction in hilly and mountainous regions should arouse more attention.  相似文献   

10.
生态旅游区域协作是联合生态资源开发、促进自然生态保护和实现区域发展的制度保障,也是解决中国生态旅游发展掣肘的关键。中国地域广阔,山地、水域等大型自然地理实体常常是行政区的自然分界线,受到行政体制分割的影响,这些地区的生态资源利用通常是独立分化式开发,造成地方政府之间生态旅游产品的低层次、重复建设,限制了我国生态旅游水平的进一步提高。因此,需要针对以上问题,构建符合我国国情的区域生态旅游合作的空间体系和模式。本文系统梳理了生态旅游区域协作发展的影响因素和发展障碍,提出了中国生态旅游区域协作的空间发展和协作模式。结果表明:(1)生态旅游区域协作是建立在自然地带性、文化社会相似性、区域经济发展协同性和政策一体化基础上的必然选择;(2)生态旅游区域协作主要存在有行政区划壁垒、合作动力不足、合作模式松散、区域划分不清等四个关键问题;(3)中国生态旅游协作发展应采用生态旅游功能片区、协作区、风景道、线路、节点相结合立体化空间治理模式,从点、线、面三个层次构建一体化的协作体系。本研究对于未来中国的区域生态旅游协作和空间体系构建具有理论指导意义。  相似文献   

11.
交通是旅游过程中能源消耗和碳排放的主要环节,认识旅游交通能源效率变化及其影响因素对推动旅游低碳化发展具有重要意义。基于中国旅游交通及相关数据,在测算不同类型旅游交通工具能源消耗系数的基础上,遵循"自上而下"原则构建新的研究方法,分析考察1994-2013年旅游交通的能源消耗、碳排放、能源效率及其影响因素。结果显示,1)中国旅游交通能源消耗由178.21PJ增长至565.82PJ,年均增长率为6.27%,相应的CO_2排放由14.96×10~6 t增长至47.94×10~6 t,主要由旅游出游人次数快速增长和旅游出行距离增加引起;2)中国旅游交通能源服务效率由3.22×10~6人次PJ~(-1)提高至5.99×10~6人次PJ~(-1),能源生态效率由26.07 kg人次~(-1)提升至14.01 kg人次~(-1);3)单位交通能耗降低、规模效应、政策推动等成为能源效率提高的主导推动因素,但旅游出行方式变化、享受型交通工具的发展等阻碍了能源效率的提升。基于分析结果,提出了中国旅游交通降低能源消耗、提高能源效率的建议措施。  相似文献   

12.
Leaf carbon content(LCC) is widely used as an important parameter in estimating ecosystem carbon(C) storage,as well as for investigating the adaptation strategies of vegetation to their environment at a large scale.In this study,we used a dataset collected from forests(5119 plots) and shrublands(2564 plots) in China,2011–2015.The plots were sampled following a consistent protocol,and we used the data to explore the spatial patterns of LCC at three scales:plot scale,eco-region scale(n = 24),and eco-region scale(n = 8).The average LCC of forests and shrublands combined was 45.3%,with the LCC of forests(45.5%) being slightly higher than that of shrublands(44.9%).Forest LCC ranged from 40.2% to 51.2% throughout the 24 eco-regions,while that of shrublands ranged from 35% to 50.1%.Forest LCC decreased with increasing latitude and longitude,whereas shrubland LCC decreased with increasing latitude,but increased with increasing longitude.The LCC increased,to some extent,with increasing temperature and precipitation.These results demonstrate the spatial patterns of LCC in the forests and shrublands at different scales based on field-measured data,providing a reference(or standard) for estimating carbon storage in vegetation at a regional scale.  相似文献   

13.
对县域农村贫困的认识是扶贫开发精准施策的基本前提。云南省是我国贫困县数量最多的省份,贫困人口多、分布范围广、贫困程度深、扶贫难度大。本文基于农村贫困发生率数据刻画了2010年和2015年云南省县域农村贫困格局,并运用逐步回归分析探索影响云南省县域层面农村贫困发生率及其变化的主要因素。研究发现,云南省县域农村贫困受自然条件和地理环境的影响颇深,2010年和2015年,在空间上均呈现出中部地区贫困程度较轻,西北、东北和南部地区贫困程度较深的整体格局,县域贫困格局与云南省地形地貌、集中连片特困区有较强的吻合性;云南省县域农村贫困发生率与农村居民年人均纯收入和农业机械化程度有较强相关性,这两个指标关系到农村居民生活水平和维持生计的农业生产情况;2010–2015年,云南省县域农村贫困发生率的变化与第一产业增加值和农业机械化程度显著相关,说明第一产业的发展在云南省县域农村居民脱贫致富的过程中起到关键作用。因此,对云南省农村地区而言,农民年人均纯收入以及农业生产水平的提高仍是其脱贫解困的主攻方向,云南省在脱贫攻坚阶段应重点围绕农民增收和农业生产经营两方面制定有效的扶贫政策措施。  相似文献   

14.
This research examines the distribution features of 4960 caves across Guizhou Province, while probing the relationship between the caves' spatial patterns and geographic elements. This study is based on hydrogeological and topographic maps of Guizhou. Arc GIS software was used to process the adjacent index, spatial analysis, and coupling analysis of the caves altitude and longitude, as well as the rock properties, lithology, drainage and tectonic division of almost 5000 caves. Based on a point pattern analysis of Guizhou caves, the adjacent index is 0.53, and the coefficient of variation verified by Tyson polygon reached 72.469%. This figure reflects the clustered distribution pattern of the caves. Across the entire province, caves are divided into four concentrated areas and one weakly affected area. The four concentrated areas are Zunyi-Tongren, Bijie, Qianxinan-Liupanshui, and Guiyang-Anshun-Qinan. The one weakly affected zone is Qiandongnan. The most concentrated among them is the Guiyang-Anshun-Qiannan area, which covers 24.67% of the total province area, and accounts for 36.63% of the total province's caves. Cave distribution in Guizhou is characterized as dense in the western part and sparse in the eastern part. Under this study background, the natural elements of formation, including lithology, structure, climate, hydrology, and altitude, and their effects on the distribution, number, and spatial pattern of cave development is analyzed.  相似文献   

15.
村镇治理是推进国家治理体系和治理能力现代化的基本要求,关乎国家乡村振兴战略的实施和国家治理现代化目标的实现。本文以全国2189个乡村治理示范村镇为研究对象,综合运用最邻近点指数法、核密度估计法、网格维数分析法、空间自相关分析法,探索乡村治理示范村镇的空间分布结构与影响因素。研究表明:全国乡村治理示范村镇空间分布趋于集聚分布,空间分异较为明显;乡村治理示范村镇核密度分析在空间上呈现出多个核中心,以及由核中心向四周递减扩散而形成的呈带状分布的次级中心的分布格局;乡村治理示范村镇系统具有明显无标度区,分形特征显著;乡村治理示范村镇空间分布主要受自然和人文因素影响明显,其中自然因素中地形地貌和湖泊水系是主要影响因素;人文因素中社会经济、交通、民族文化是主要影响因素,人口分布的影响不显著。  相似文献   

16.
Urban agglomerations in China have become the strategic core of national economic development and the main component of the new type of urbanization. However, they are threatened by a series of eco-environmental problems and challenges, including the severe overexploitation of natural resources. Eco-efficiency, which is defined as accomplishing the greatest possible economic benefit with the least possible resource input and damage to the environment, is used as an indicator to quantify the sustainability of urban agglomerations. In this work, a traditional data envelopment analysis(DEA) model with a slack-based measurement(SBM) model of undesirable outputs, was used to assess and compare the economic efficiency and eco-efficiency of four major urban agglomerations in eastern China(UAECs) in 2005, 2011, and 2014. The spatio-temporal characteristics of the evolution of urban agglomerations were analyzed. Based on the results of a slack analysis, suggestions for improving the eco-efficiency of the four UAECs are provided. The overall economic efficiency of urban agglomerations located in the Shandong Peninsula, Yangtze River Delta, and Pearl River Delta displayed a V-shaped pattern(decreased and then increased). In contrast, the overall economic efficiency of the Beijing-Tianjin-Hebei urban agglomeration declined during the study period. The Beijing-Tianjin-Hebei urban agglomeration had a considerable loss of economic efficiency due to pollution, whereas the Shandong Peninsula urban agglomeration was less impacted. Overall, the eco-environmental efficiency of the four UAECs declined from 2005 to 2011 and then increased from 2011 to 2014. In addition, the urban eco-efficiency in the four coastal UAECs was characterized by different evolution patterns. The eco-efficiency was higher in the peri-urban areas of the core cities, riverside areas, and seaside areas and lower in the inland cities. The core cities of the Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta urban agglomerations were characterized by high resource consumption, economic benefit output, and eco-efficiency. In most of cities in the urban agglomerations, the emission of pollutants declined, leading to a reduction of pollutants and mitigation of environmental problems. In addition, a differential analysis, from the perspective of urban agglomeration, was performed, and concrete suggestions for improvement are proposed.  相似文献   

17.
The development of grass-feeding livestock breeding is the key to promoting the transition from grain-consumption type animal husbandry to grain-saving type animal husbandry in China, and to solving the problem of competition for grain between people and livestock. From the perspective of economic geography, this paper first defines the conversion standard for the breeding quantity of livestock, and then uses exploratory spatial data analysis technology and econometric models and methods to systematically investigate the sequential variation process, geographical aggregation characteristics, and influencing factors of grass-feeding livestock breeding in China. The study results show the following: 1) The breeding quantity of grass-feeding livestock in China has an obvious overall growth trend, but there is an obvious difference among the livestock species. During the period 1978–2012, the breeding quantity of grass-feeding livestock in China grew by 92.5%; and the breeding quantity within the same period was beef cattle sheep dairy cow. 2) On the county scale, the number of increasing areas of the breeding quantity of grass-feeding livestock is larger than the number of decreasing areas, and the growth rate of breeding quantity of grass-feeding livestock in northern China is higher than that in southern China, which initially forms the pattern of "hot in the north and cold in the south". 3) The spatial Durbin model shows that the per capita output of grain, proportion of productive land area, urban per capita disposable income, agricultural mechanization level, agricultural labor productivity and policy factor have positive effects on the development of grass-feeding livestock breeding, while the per capita GDP, urbanization level and proportion of non-agricultural income have obvious negative effects on it. 4) Grass-feeding livestock breeding in China can be divided into six major types of areas, and each type of area should be regulated and controlled in terms of their respective focus of attention according to regional conditions and situation of agricultural production.  相似文献   

18.
农作物秸秆还田作为农田土壤和养分管理的推荐做法之一,对于土壤有机碳(SOC)固定和CO_2减排具有重要意义。本研究利用环境政策综合气候模型(EPIC)模拟了4种作物秸秆还田情形下2001年至2010年中国农田表层土壤有机碳变化及其空间格局。模拟结果显示,秸秆完全移除(CR0%)下的土壤有机碳损失为28.89 Tg yr–1,当前30%的秸秆还田(CR30%)能够减缓22.38 Tg C yr–1的碳损失。若秸秆还田率从30%提高至50%(CR50%)乃至75%(CR75%),中国农田表层土壤将变为净碳汇。中国农田表层土壤固碳潜力在CR50%和CR75%情形下分别可达25.53 Tg C yr–1和52.85 Tg C yr–1,且在不同农业区存在空间异质性。单位面积土壤固碳潜力在西北和华北地区最高,而华东最低。华北地区具有最高的区域固碳潜力。在这十年间,CR50%和CR75%情形下增加的土壤表层有机碳相当于减少了1.4%和2.9%的中国CO_2排放总量。总之,我们建议鼓励我国农民将原本直接焚烧或用作家用燃料的秸秆返还田间以改善土壤性质和减缓大气CO_2增加,尤其是华北地区更应推行这一举措。  相似文献   

19.
林地是维护生态安全,实现区域可持续发展的根本基础资源。林地变化可能导致一些生态环境问题,包括土壤侵蚀,水资源短缺,干旱加剧以及生物多样性的丧失。本文以景观生态学和逻辑回归模型为基础,探讨了京津冀地区1985-2000期间林地变化的时空格局及其影响因素。格局分析结果表明,林地景观破碎化正在下降和林地形状变得越来越规则。通过建立Logistic回归模型,这项研究旨在探讨这一区域1985-2000期间林地变化的重要变量。对于京津冀地区1985-2000期间林地变化而言,土壤有机质含量,坡度(5°),到最近村庄的距离以及人均国内生产总值是最重要的解释变量。研究表明,空间异质性会影响到林地变化的逻辑回归模型的可预测性。  相似文献   

20.
Ambient air pollution brought by the rapid economic development and industrial production in China has exerted a significant influence on socio-economic activities and public health, especially in the densely populated urban areas. Therefore, scientific examination of regional variation of urban air quality and its dominant factors is of great importance to regional environmental management. Based on daily air quality index(AQI) datasets spanning from 2014 to 2016, this study analysed the spatiotemporal characteristics of air quality across different regions throughout China and ascertained the determinants of urban air quality in disparate regions. The main findings are as follows:(1) The annual average value of the urban AQI in China decreased from 2014 to 2016, indicating a desirable trend in air quality at the national scale.(2) The attainment rate of the urban AQI exhibited an apparent spatially stratified heterogeneity, wherein North China retained a high AQI value. The increase of Moran's I Index reported an apparent spillover effect among adjacent regions.(3) Both at the national and regional scales, the seasonal tendency of air quality in each year is similar, wherein good in summer and relatively poor in winter.(4) Results drawn from the Geographic Detector analysis show that dominant factors influencing AQI vary significantly across urban agglomerations. Topographical and meteorological variations in urban areas may lead to complex spatiotemporal variations in pollutant concentration. Whereas given the same natural conditions, the human-dominated factors, such as industrial structure and urban form, exert significant impacts on urban air quality.The spatial spillover effects and regional heterogeneity of urban air quality illustrated in this study suggest the governments and institutions should set priority to the importance of regional cooperation and collaboration in light of environment regulation and pollution prevention.  相似文献   

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