Assessing the evolution of oases in arid regions by reconstructing their historic spatio-temporal distribution： a case study of the Heihe River Basin, China

Oasis evolution, one of the most obvious surface processes in arid regions, affects various aspects of the regional environment, such as hydrological processes, ecological conditions, and microclimates. In this paper, the historical spatio-temporal evolution of the cultivated oases in the Heihe River Basin, the second largest inland watershed in the northwest of China, was assessed using multidisciplinary methods and data from multiple sources, including historical literature, ancient sites, maps and remotely sensed images. The findings show that cultivated oases were first developed on a large scale during the Han Dynasty （121 BC-220） and then gradually decreased in extent from the Six Dynasties period （220-581） to the Sui- Tang period （581-907）, reaching a minimum in the Song- Yuan period （960-1368）. An abrupt revival occurred during the Ming Dynasty （1368-1644） and continued through the Qing Dynasty （1644-1911）, and during the period of the Republic of China （1912-1949）, oasis development reached its greatest peak of the entire historical period. The oasis areas during seven major historical periods, i.e., Hart, Six Dynasties, Sui-Tang, Song-Yuan, Ming, Qing, and Republic of China, are estimated to have been 1703 kma, 1115 km2, 629 km2, 614 km2, 964 km2, 1205 km2, and 1917 km2, respectively. The spatial distribution generally exhibited a continuous sprawl process, with the center of the oases moving gradually from the downstream region to the middle and even upstream regions. The oases along the main river remained stable during most periods, whereas those close to the terminal reaches were subject to frequent variations and even abandonment. Socio-economic factors were the main forces driving the evolution of cultivated oases in the area; among them, political and societal stability, national defense, agricultural policy, population, and technological progress were the most important.

Do green spaces affect the spatiotemporal changes of PM_(2.5) in Nanjing?

Introduction:Among the most dangerous pollutants is PM_(2.5),which can directly pass through human lungs and move into the blood system.The use of nature-based solutions,such as increased vegetation cover in an urban landscape,is one of the possible solutions for reducing PM_(2.5) concentration.Our study objective was to understand the importance of green spaces in pollution reduction.Methods:Daily PM_(2.5) concentrations were manually collected at nine monitoring stations in Nanjing over a 534-day period from the air quality report of the China National Environmental Monitoring Center(CNEMC)to quantify the spatiotemporal change of PM_(2.5) concentration and its empirical relationship with vegetation and landscape structure in Nanjing.Results:The daily average,minimum,and maximum PM_(2.5) concentrations from the nine stations were 74.0,14.2,and 332.0μg m^(−3),respectively.Out of the 534 days,the days recorded as“excellent”and“good”conditions were found mostly in the spring(30.7%),autumn(25.6%),and summer(24.5%),with only 19.2% of the days in the winter.High PM_(2.5) concentrations exceeding the safe standards of the CNEMC were recorded predominately during the winter(39.3-100.0%).Our hypothesis that green vegetation had the potential to reduce PM_(2.5) concentration was accepted at specific seasons and scales.The PM_(2.5) concentration appeared very highly correlated(R2>0.85)with green cover in spring at 1-2 km scales,highly correlated(R2>0.6)in autumn and winter at 4 km scale,and moderately correlated in summer(R2>0.4)at 2-,5-,and 6-km scales.However,a non-significant correlation between green cover and PM_(2.5) concentration was found when its level was>75μg m^(−3).Across the Nanjing urban landscape,the east and southwest parts had high pollution levels.Conclusions:Although the empirical models seemed significant for spring only,one should not devalue the importance of green vegetation in other seasons because the regulations are often complicated by vegetation,meteorological conditions,and human activities.

China's Regional Inequality in Innovation Capability,1995-2006

This paper assesses both interregional and intraregional innovation inequality in China from 1995 to 2006. It is revealed that the east-central-west inequality has increased over time. whereas the inter-provincial inequality showed a V-pattern until 2003; Both inequality measures oscillated from 2004 to 2006. Using a deeomposition framework recently developed by one of the authors, we determined that the major factors driving innovation inequality are population, economic development level, R＆D, location and openness. The aggravated innovation inequality reflects the growth of China＇s innovation centers in the eastern region and their admission into the global innovation networks. The fact that R＆D is a major .factor driving the inequality suggests that, consMered in the present study, the efficiency of R＆D investment improved in certian regions during the period （1995-2006）. Finally, geographic, location and openness affect innovation inequality primarily through the coupled evolution of innovation capability and economic development, resulting in first-mover advantages to provinces of the eastern region.

Urbanization,economic development,and environmental changes in transitional economies in the global south:a case of Yangon

Background:Transitional economies in Southeast Asia—a distinct group of developing countries—have experienced rapid urbanization in the past several decades due to the economic transition that fundamentally changed the function of their economies,societies and the environment.Myanmar,one of the least developed transitional economies in Southeast Asia,increased urbanization substantially from 25%in 1990 to 31%in 2019.However,major knowledge gaps exist in understanding the changes in urban land use and land cover and environment and their drivers in its cities.Methods:We studied Yangon,the largest city in Myanmar,for the urbanization,environmental changes,and the underlying driving forces in a radically transitioned economy in the developing world.Based on satellite imagery and historic land use maps,we quantified the expansion of urban built-up land and constructed the land conversion matrix from 1990 through 2020.We also used three air pollutants to illustrate the changes in environmental conditions.We analyzed the coupled dynamics among urbanization,economic development,and environmental changes.Through conducting a workshop with 20 local experts,we further analyzed the influence of human systems and natural systems on Yangon’s urbanization and sustainability.Results:The city of Yangon expanded urban built-up land rapidly from 1990 to 2000,slowed down from 2000 to 2010,but gained momentum again from 2010 to 2020,with most newly added urban built-up land appearing to be converted from farmland and green land in both 1990–2000 and 2010–2020.Furthermore,the air pollutant concen-tration of CO decreased,but that of NO_(2)and PM_(2.5)increased in recent years.A positive correlation exists between population and economic development and the concentration of PM_(2.5)is highly associated with population,the economy,and the number of vehicles.Finally,the expert panel also identified other potential drivers for urbanization,including the extreme climate event of Cyclone Nargis,capital relocation,and globalization.Conclusions:Our research highlights the dramatic expansion of urban land and degradation of urban environment measured by air pollutants and interdependent changes between urbanization,economic development,and environmental changes.