China had implemented the national strategies for Major Function-oriented Zones (MFOZs) to realize the goal of national sustainable development since 2010. This study analyzed and compared spatio-temporal characteristics and differences in built-up area for China’s MFOZs using a China’ s Land Use Database (CLUD) derived from high-resolution remotely sensed images in the periods of 2000-2010 and 2010-2013. To sum up: (1) The percentage of built-up area in each of the MFOZs was significantly different, revealing the gradient feature of national land development based on the distribution of the main functions. (2) Annual growth in built-up area in optimal development zones (ODZs) decreased significantly during 2010-2013 compared with the period 2000-2010, while annual growth in built-up area in key development zones (KDZs), agricultural production zones (APZs) and key ecological function zones (KEFZs) increased significantly. (3) In ODZs, the average annual increase in built-up area in the Yangtze River Delta region was significantly higher than in other regions; the average area increase and rate of increase of built-up area in KDZs was faster in the western region than in other regions; average annual area growth of built-up area in APZs in the northeast, central and western regions was twice as high as the previous decade on average; the annual rate of change and increase in the dynamic degree of built-up area were most notable in KEFZs in the central region. (4) The spatial pattern and characteristics of built-up area expansions in the period 2010-2013 reflected the gradient feature of the plan for MFOZs. But the rate of increase locally in built-up area in ODZs, APZs and KEFZs is fast, so the effective measures must be adopted in the implementation of national and regional policies. The conclusions indicated these methods and results were meaningful for future regulation strategies in optimizing national land development in China.
Quantifying the contributions of climate change and human activities to ecosystem evapotranspiration (ET) and gross primary productivity (GPP) changes is important for adaptation assessment and sustainable development. Spatiotemporal patterns of ET and GPP were estimated from 2000 to 2014 over North China Plain (NCP) with a physical and remote sensing-based model. The contributions of climate change and human activities to ET and GPP trends were separated and quantified by the first difference de-trending method and multivariate regression. Results showed that annual ET and GPP increased weakly, with climate change and human activities contributing 0.188 mm yr-2 and 0.466 mm yr-2 to ET trend of 0.654 mm yr-2, and -1.321 g C m-2 yr-2 and 7.542 g C m-2 yr-2 to GPP trend of 6.221 g C m-2 yr-2, respectively. In cropland, the increasing trends mainly occurred in wheat growing stage; the contributions of climate change to wheat and maize were both negative. Precipitation and sunshine duration were the major climatic factors regulating ET and GPP trends. It is concluded that human activities are the main drivers to the long term tendencies of water consumption and gross primary productivity in the NCP.
Spatial-explicitly mapping of the hotspots and coldspots is a vital link in the priority setting for ecosystem services (ES) conservation. However, little research has identified and tested the compactness and efficiency of their ES hotspots and coldspots, which may weaken the effectiveness of ecological conservation. In this study, based on the RUSLE model and Getis-Ord Gi* statistics, we quantified the variation of annual soil conservation services (SC) and identified the statistically significant hotspots and coldspots in Shaanxi Province of China from 2000 to 2013. The results indicate that, 1) areas with high SC presented a significantly increasing trend as well, while areas with low SC only changed slightly; 2) SC hotspots and coldspots showed an obvious spatial differentiation—the hotspots were mainly spatially aggregated in southern Shaanxi, while the coldspots were mainly distributed in the Guanzhong Basin and Sand-windy Plateau; and 3) the identified hotspots had the highest capacity of providing SC, with 29.6% of the total area providing 59.7% of the total service. In contrast, the coldspots occupied 46.3% of the total area, but only provided 17.2% of the total SC. In addition to conserving single ES, the Getis-Ord Gi* statistics method can also help identify multi-functional priority areas for conserving multiple ES and biodiversity.
Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake varied. Water level dropped, the velocity decreased and water exchange time lengthened, which changed the release of phosphorous from sediments. In order to investigate how the hydrodynamic factors influence the release of phosphorous from sediments, we used a two-way annular flume device to simulate the release characteristics of phosphorous from sediments under variable water levels and velocities. We found that both water level rising and velocity increasing could enhance the disturbance intensity to sediments, which caused the increase of suspended solids (SS) concentration, total phosphorus (TP) concentration in the overlying water, and the ability that phosphorus released to overlying water from sediments enhanced as well: when overlying water velocity maintained 0.3 m/s, SS concentration increased to 4035.85 mg/L at the water level 25 cm which was about 25 times compared to the minimum value and TP concentration in the overlying water also reached the maximum value at the water level 25 cm which was 1.2 times that of the value at 10 cm; when water level maintained 15 cm, SS concentration increased to 4363.35 mg/L at the velocity of 0.5 m/s which was about 28 times compared to the value of 0 m/s, and TP concentration in the overlying water increased from 0.11 mg/L to 0.44 mg/L. When the water level maintained 15 cm, the phosphorous release rate reached the maximum value of 4.86 mg/(md) at 0.4 m/s. The concentration of total dissolved phosphorous (TDP) and soluble reactive phosphate (SRP) both in overlying water and sediment-water interface were negatively correlated with pH. Using the parabolic equation, the optimum water level at a velocity of 0.3 m/s was calculated to be 0.57 cm, and the optimum velocity at water level of 15 cm was found to be 0.2 m/s.
Much attention is being given to estimating cement-related CO2 emissions in China. However, scant explicit and systematical exploration is being done on regional and national CO2 emission volumes. The aim of this work is therefore to provide an improved bottom-up spatial-integration system, relevant to CO2 emissions at factory level, to allow a more accurate estimation of the CO2 emissions from cement production. Based on this system, the sampling data of cement production lines were integrated as regional- and national-level information. The integration results showed that each ton of clinker produced 883 kg CO2, of which the process, fuel, and electricity emissions accounted for 58.70%, 35.97%, and 5.33%, respectively. The volume of CO2 emissions from clinker and cement production reached 1202 Mt and 1284 Mt, respectively, in 2013. A discrepancy was identified between the clinker emission factors relevant to the two main production processes (i.e., the new suspension preheating and pre-calcining kiln (NSP) and the vertical shaft kiln (VSK)), probably relevant to the energy efficiency of the two technologies. An analysis of the spatial characteristics indicated that the spatial distribution of the clinker emission factors mainly corresponded to that of the NSP process. The discrepancy of spatial pattern largely complied with the economic and population distribution pattern of China. The study could fill the knowledge gaps and provide role players with a useful spatial integration system that should facilitate the accurate estimation of carbon and corresponding regional mitigation strategies in China.
The floating population has become the main driver of urban population excessive growth in China’s mega cities. Urban transit system (UTS) is a significant factor in population spatial distributions within urban areas, especially rapid and high-capacity transit systems. This paper analyzes the causal effects of the extension of expressways and subways between 2000 and 2010 in the Beijing Metropolitan Area (BMA), focusing on the group differences between the local residents and the floating population. Due to the endogeneity of transportation improvements and population growth, Instrumental Variable (IV) regression model is applied to avoid this problem. The results show the local residents increased in the inner suburbs but decreased in the city center, while the floating population increased in the majority areas. IV regression results show that the extension of urban transit systems had statistically significant impacts on population growth across the BMA. The results also show that the extension of urban subway system had more effects on the floating population than the local residents across the BMA. It is mainly caused by the rather low fare of urban subway system. This implies that the excessive subsidy on urban subway system could result in excessive floating population growth and residential differentiation, even residential segregation. Hence, it is necessary to plan and design reasonable and scientific urban transit systems in order to advance reasonable population size and promote residential integration. Moreover, the regional analysis shows that the effects of urban transportation improvements on the local residents are not statistically significant in the inner suburbs. It implies that urban transportation improvements had limited effects on inducing people to move to suburban areas and controlling center city’s population in Beijing. Therefore, it should be stressed the differentiated effects of urban transportation improvements on population distribution in the process of urban planning and population control.
The Xiaohe Cemetery archaeological site (Cal. 4-3.5 ka BP) is one of the most important Bronze Age sites in Xinjiang, China. Although the surrounding environment is an extremely arid desert now, abundant archaeological remains indicate that human occupation was common during certain periods in the Holocene. Field investigations and laboratory analyses of a sediment profile near the Xiaohe Cemetery indicate that while the regional environment was arid desert throughout the Holocene there were three episodes of lake formation near the site in the periods 4.8-3.5 ka BP, 2.6-2.1 ka BP and 1.2-0.9 ka BP. Geomorphic and hydrological investigations reveal that a lake or lakes formed in a low-lying area when water was derived initially from the Kongque River and then shunted into the Xiaohe River basin. Low amounts of active chemical elements in lacustrine sediment between 4.8-3.5 ka BP indicate abundant and continuous water volume in the lake; the content of active chemical elements increased between 2.6-2.1 ka BP but was still at a relatively low level, suggesting a declining amount of water and diminished inflow. Between 1.2-0.9 ka BP there was a very high content of active elements, suggesting decreased water volume and indicating that the lake was stagnate. In contrast, the general climate condition shows that there had a warm-humid stage at 8-6 ka BP, a cool-humid stage at 6-2.9 ka BP and a warm-dry stage at 2.9-0.9 ka BP in this region. The hydrological evolutions around Xiaohe Cemetery did not have one-to-one correspondence with climate changes. Regional comparison indicates that broad-scale climatic conditions played an important role through its influences on the water volume of the Tarim River and Kongque River. But, the formation of the lakes and their level were controlled by geomorphic conditions that influenced how much water volume could be shunted to Xiaohe River from Kongque River. Human occupation of the Xiaohe Cemetery and nearby regions during the Bronze Age and Han-Jin period (202 BC-420 AD) corresponded to the two earlier lake periods, while no human activities existed in the third lake period because of the decreased water volume.
