The development of domestic and foreign concepts, and previous research of desertification are reviewed in this paper. We conclude that extreme land degradation in sub-humid and humid regions should be classified as desertification. Due to the lithology of the soft redbed rocks, along with excessive resource exploitation by humans and the humid climate, a special kind of desertification occurred in redbed regions in Southern China. As preliminary research concerning redbed desertification, we put forward the concepts of redbed deserts and redbed desertification. We also elaborate on features of desertification developing in redbed regions, such as landform features, ecological features, and soil features. Then, utilizing Nanxiong Basin as a case study, the spatial patterns of redbed desertification and the patterns of desertification at the basin scale are analyzed. The process of redbed desertification begins as spotty uncovering, and then develops into patches. Redbed desertification has mostly occurred on hills formed of soft rock in the central part of the basin. Based on the field work, the mechanism of redbed desertification is discussed from the aspects of lithological features, natural impacts, and human activities. The triggers of redbed badland desertification are complex, but are mainly impacted by activities such as severe reclamation, forest fires, tree planting disturbances, dry-land degradation, acquirement of topsoil, and so on. Once red beds are exposed, the extension of the desert region can be caused by both nature and human activities.
With the help of GIS and RS technology, and based on remote sensing image data, DEM data, soil type data and relevant statistical data, we use the modified universal soil loss equation (RUSLE) as the evaluation model to determine the relevant parameters of the model, to calculate the soil erosion modulus in Chaohu Watershed from 1992 to 2013, and to analyze the spatial and temporal dynamic changes of soil erosion intensity in this region. The soil erosion area in Chaohu basin is mainly distributed in the NE-SW direction. Slight, mild, moderate, intense, strong and severe erosion accounted for 93.46%, 6.25%, 0.68%, 0.19%, 0.01% and 0.01% of the total watershed area respectively. The largest erosion area was paddy field, accounting for 64.42% of the total watershed, followed by woodland (20.98%) and urban and industrial land (10.36%), which was based on micro erosion and mild erosion mentioned above. From 1992 to 2006, the soil erosion modulus decreased from 510.70 t/(km2·a) to 129.79 t/(km2·a), falling by 74.59%, while the vegetation cover increased from 37% to 47.80%. The change of soil erosion area was obvious: mild (8.93%), moderate (2.33%), intense (1.32%), extreme (0.09%) and severe erosion (0.05%) were reduced to 4.74%, 1.39%, 0.28%, 0.02% and 0.01%, respectively, while slight erosion increased from 87.88% to 94.16%. However, the slight erosion reduced to 93.46%, and the slight erosion had a worsening trend in 2013. From 1992 to 2013, the soil erosion modulus increased from 129.79 t/(km2·a) to 149.44 t/(km2·a), an increase of 15.14%, meanwhile the vegetation cover rate decreased from 47.80% to 45.15%.
Haze pollution in China has become a severe environmental problem for people’s daily life as well as their health, among which PM2.5 makes significant contribution to poor air quality. Satellite observations played a leading role in the recognition in the spatio-temporal variation of PM2.5 nationally. However, based on the information and data obtained by satellites, the inversion method has limitations to truly reflect the spatio-temporal variation of PM2.5 concentrations near ground level. Based on the observed PM2.5 concentration data from 945 newly set-up air monitoring sites in 2014, our research reveals the spatio-temporal variations of PM2.5 concentrations in China by using spatial statistical model. The results show that (1) in 2014, the average PM2.5 concentration in China was 61 μg/m3. It had a periodical U-impulse type daily variation as well as a U-shaped monthly variation with a higher level in autumn and winter while a lower one in spring and summer. (2) Concentration of PM2.5 in urban China shows a significant spatial differentiation and clustering pattern with spatial-periodic occurrences in north and south China. (3) The Hu-line (Hu Population Line) and Yangtze River are respectively the east-west and north-south boundaries which separate the high-value zone and the low-value zone of PM2.5 concentrations in China. In 2014, the highly polluted cities by PM2.5 were mainly distributed in the urban agglomerations (Central Henan, Harbin-Changchun, the Bohai Rim Region, the Yangtze River Delta, and the Middle Yangtze River), east of the Hu-line and north of the Yangtze River. The Beijing-Tianjin-Hebei urban agglomeration was the most severely polluted region all the year round. The southeast coastal region centered on the Pearl River Delta had good air quality in a stable manner.
To explore the large-scale changes in leaf functional traits from the species level to community level and their influencing factors in Eastern China, we investigated leaf area (LA), leaf thickness (LT), specific leaf area (SLA) and leaf dry matter content (LDMC) across 847 species from nine typical forest ecosystems along the North-South Transect of Eastern China (NSTEC) between July and August in 2013, and we also calculated the community weighted means (CWM) of leaf traits on the basis of the relative dominance of each species within the community. Our results showed that, for all 847 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. In addition, SLA increased and LDMC decreased with the increasing latitude, whereas no clear latitudinal trends of LA and LT were found (R2 = 0.02-0.06), as latitudinal changes were mainly affected by plant functional types. At the community level, more significant spatial patterns of leaf traits were observed (R2 = 0.46-0.71). Generally, as latitude increased, LACWM and SLACWM varied nonlinearly, while LTCWM increased and LDMCCWM decreased linearly, which were influenced by climate and soil N. This study improved the biogeographical database of leaf functional traits from tropical to cold-temperate forests in eastern China and emphasized the importance of scaling-up in the study of plant traits.
Low-slope hilly land is one of the most important construction and development resources in China, where hilly area is much more than the flat ground. The construction process can be very difficult as the complex terrain and sensitive eco-environment of the hilly land, where eco-environmental problems may take place due to unreasonable human development. An ecological risk assessment conceptual framework of low-slope hilly land has been built by taking account of natural ecological risk probability, development ecological risk probability as well as ecological importance. In detail, natural ecological risk probability contains geological disaster stress and soil erosion stress, while the development ecological risk consists of pollution accumulated stress, resource depletion stress and space occupation stress. Then a conceptual framework has been applied in the ecological risk assessment of Dali Bai Autonomous Prefecture, a representative region of low-slope hilly city construction areas in Yunnan Province, China. In this study, firstly, the quantitative and spatial patterns of the influence factors were analyzed separately and then the integrated ecological risk probability was graded into 5 degrees. Secondly, the spatial pattern of integrated ecological risk and its relationship with land use types has been analyzed. Finally, 383 watersheds were classified into four categories, namely development priority area, protection priority area, development balance area and protection balance area according to the grade of integrated ecological risk and grade of development status. The guidance and advice for future development has also been proposed for low-slope hilly construction in Dali Prefecture.
Natural ecosystems offer society important goods and services. With the rapid population growth and ongoing natural resource use, humans have enhanced the production of some services at the expense of others. This paper examines changes in ecosystem services, and the relationship between ecosystem services, in Guanzhong-Tianshui Economic Region. These ecosystem changes are of great significance to the sustainable development of this economic region. The methods of "rose map" and "production possibilities frontiers (PPFs)" are applied to evaluate the trade-offs and co-benefits between NPP, water conservation, and soil erosion. Furthermore, the CASA (Carnegie-Ames-Stanford Approach) model, ULSE (Universal Soil Loss Equation) model, and the water storage capacity method are used to estimate net primary productivity (NPP), water conservation, and soil erosion. The study takes soil retention (the reduction of soil erosion) as a model ecosystem service, using 2000-2010 data from the study area. Three land use strategy scenarios - planning, exploitation and protection - are applied to evaluate potential changes in ecosystem services and trade-offs between NPP, water conservation, and soil erosion. The study reveals noticeable trade-offs between NPP, water conservation, and soil erosion, with co-benefits from NPP and water conservation. There are also trade-offs between NPP, water conservation, and soil erosion under the three scenarios. The "protection" scenario is the most favorable land use strategy for regulating ecosystem service capacity; that scenario results in the highest NPP, water conservation, and soil retention. The results could impact natural capital and ecosystem services planning, management, and land use decision-making.
Archaeological excavations have exposed a shocking picture of the prehistorical calamities in the Lajia Ruins in the Guanting Basin along the Yellow River. The destruction reasons has been a hot and focus issue in recent years. Geological records of the major disasters in relation to the devastation of this prehistorical settlement were investigated by detailed field observations, sedimentological analysis and optically stimulated luminescence (OSL) and 14C dating. More importantly, we made a comparative study of the conglomerated red clay, the gully deposit at the foot of the Great Red Hills where the Ganggou gullies emerge onto the Guanting Basin, and the palaeoflood deposit of the Yellow River in the barrier lake in the Jishixia. The results show that at ca. 3950 a BP, immediately followed by a major earthquake, the settlement was overtaken by immense mudflows coming along the tributary gullies from the hillsides behind. The enormous mudflows suddenly buried and destroyed the dwellings, which led to the prehistorical calamities in the Lajia Ruins. These results are of important implications in understanding the prehistorical environmental change in the environmentally sensitive zones over the world. It has very important reference value for the further studying of man-land relationship.
The paper estimates urban land-use efficiency, investigates its spillover effect, and analyses its determinants based on stochastic frontier production function and spatial lag model, by using city-level panel data of 282 cities during 2003-2012. The empirical results support that: first, there exists an obvious spatial and temporal variation in land-use efficiency among the 282 cities from 2003-2012. For example, the land-use efficiency indices in most of the cities were below 0.8 in 2003. However, these indices rose up to 0.8 in 2012. The cities with high land-use efficiency are concentrated in the Pearl River Delta, Hunan province, Hubei province, southern Henan province, eastern Anhui province and the junction between Shandong and Jiangsu provinces. Cities located in central China are most efficient in land use, while northeastern cities are most inefficient ones. The land-use efficiency in northwestern cities grows fastest while that in southwest cities slowest. Second, the spillover effect of land-use efficiency is significantly positive, which is higher in central, northeastern and northwestern than in southeastern cities. The spatial spillovers might originate from the demonstration effect of land-use efficiency through technological diffusion and industrial transfer. Third, there exist similarities and differences in determinants of urban land-use efficiency across cities and regions. Overall, transportation infrastructure, information technology, saving level positively affect urban land-use efficiency, while foreign direct investment, or loans do not significantly increase the urban land-use efficiency. The population density affects land-use efficiency convexly in eastern and southwestern cities and concavely in northeastern cities. Fiscal expenditure exerts significant positive influence on land-use efficiency in eastern, northeastern, northwestern, and southwestern cities. The ratio of college students to population positively influences urban land-use efficiency in eastern cities, while negatively in other ones. The medical care affects urban land-use efficiency negatively over the whole country but not in northwest China. Land marketization is conducive to urban land-use efficiency in eastern, central and southwestern China. The influence of land type on land-use efficiency varies across different regions and cities.
Three-dimensional urban space expansion has become an important feature of China’s urban spatial expansion since the early 21st century. Based on the three-dimensional digital reconstruction results of Nanjing in 2000 and 2012, this paper expanded the application methods of land use types transfer-matrix to study the evolution of land use intensity caused by the changes of land use types in urban built-up areas. The results consist of three aspects: (1) Nanjing's built-up area has experienced rapid expansion since the early 21st century, and it expanded 50.50 km2 per year on average. During the past 12 years, industrial land attained maximal growth with an expansion of 155.34 km2, and its main incremental source was agricultural land, followed by residential land. Agricultural land and water area decreased obviously, and the lost agricultural land was transferred mainly to industrial land. (2) The sequence of average plot ratio of five major land use types in built-up areas, which were commercial land, residential land, educational land, industrial land and land for other construction purposes in descending order, did not change from 2000 to 2012, and the average plot ratio of the first four land use types increased by 0.59, 0.48, 0.31 and 0.06, respectively. In the transformation processes of five major land use types in built-up areas, the plot ratio of residential land converted to other construction land decreased, while other conversion types significantly increased. The plot ratio of unchanged land use types also constantly rose. (3) The plot ratios of new residential and educational lands as well as land for other construction purposes exceeded those of the corresponding land types in the old town, suggesting that the plot ratios of land types in the urban expansion area were at a higher level. The plot ratios of new industrial land and old industrial land were unchanged. The plot ratio of new commercial land was 65.67% of that of old commercial land.
This study explores the spatial distribution of the first frost date, last frost date and the frost-free period in China through an in-depth analysis of the daily minimum temperature. Accumulative anomaly and linear trend estimation are used to describe the trends in the first frost date, last frost date and the length of the frost-free period. Then, the relationship between the first frost date, last frost date and the frost-free period is explored, and the abrupt feature of frost-free period is detected using a Mann-Kendall test. Four major results were obtained. First, the frost-free period decreases with the increase of latitude or altitude, with yearly fluctuation as latitude ascends or altitude descends. Second, over large parts of China (80%), the frost-free period is extended by both a later first frost date and an earlier last frost date. Furthermore, the magnitude of the changes in the three indices (the first frost date, last frost date and frost-free period) are higher in the north and east regions, but lower in the south and west. Third, for the majority of agricultural regions, the delayed first frost date together with an earlier last frost date prolongs the frost-free period. However, in some areas of the southwest agricultural region and the middle and lower Yangtze River agricultural region, the last frost date is later, but is more than offset by the later first frost date, or the first frost date is earlier, but is more than offset by the earlier last frost date, so the frost-free period is still be prolonged. Fourth, the mutation of the frost-free period was significant in Northeast China, Inner Mongolia and Great Wall, Huang-Huai-Hai, Qinghai-Tibet and Gansu-Xinjiang agricultural regions, which constitute half of China. With respect to timing, the mutation of the frost-free period occurred primarily in the eastern monsoon region in the 1980s and in the western non-monsoon region in the 1990s. Overall, these changes in the three indices (first and last frost date, and frost-free period length) could affect the suitability of conditions for sowing and harvesting of a variety of crops.
This article reviews the hydrological geography in the Heilongjiang River Basin from four aspects: geographical environment, surface water, groundwater and the water quality. Studies on geographical environment can be illustrated on climate change, lakes and wetlands, watershed regionalization and watershed development. In recent years, the Heilongjiang River Basin has witnessed warming climate, its river basin has abundant lakes and wetland resources, its river basin has numerous protected areas and protected objects on both sides, its reservoirs play a key role for its water resources development and utilization. Studies on surface water can be made on runoff characteristics and flood characteristics. The Heilongjiang River can be divided into seven tributaries and one main stream. Atmospheric circulation anomalies are the direct cause for consecutive torrential rain over the main stream in 2013. Studies on groundwater can be conducted on hydrogeology, groundwater level and trans-boundary aquifers. The Heilongjiang River Basin can be divided into nine hydrogeological zones. The change of the groundwater level has its unique characteristics. Thus, trans-boundary aquifers need to be studied in the future. Studies on water quality can be illustrated on surface water quality and groundwater quality. Prevention and cure work against the polluted water need to be strengthened, groundwater control measures and emergency treatment programs need to be put forward as soon as possible. Finally, hot topics related to surface water quality and groundwater quality are discussed.
In this paper, we compared the concept of agricultural drought and its relationship with other types of drought, and discussed research progress in agricultural drought monitoring from the site-based and remote sensing aspects, respectively. The applicability and limitations of different drought monitoring indexes were also compared. Results showed that the site-based drought index has experienced a long development history and become the main way of monitoring drought. Meanwhile, the remote sensing based drought index was mainly established from two aspects, soil water and crop water, and has achieved good results in agricultural drought monitoring. In addition, through mathematical statistics and document comparison, the development and latest progress of agricultural drought monitoring has been revealed, suggesting a transformation of agricultural drought monitoring from traditional single meteorological monitoring indicators to integrated meteorology and remote sensing monitoring indicators, mainly reflected in the introduction of multisource data and the innovation of research methods. The applicability and limitations of comprehensive drought monitoring indexes established in recent years were also discussed. Finally, through the analysis of current challenges in agricultural drought monitoring, future research prospects in agricultural drought monitoring are proposed, including further investigating the mechanism of agricultural drought, identifying the influences of agricultural drought, developing a multi spatiotemporal scale agricultural drought monitoring model, coupling the qualitative and quantitative agricultural drought evaluation models, and improving the application level of remote sensing data in agricultural drought monitoring.
"New Five Modernizations" is the opportunity and innovation of Geography. The 2015 annual conference of "The Geographical Society of China (North China) and Yellow River Branch" is convened in Shandong Normal University in September, 2015. After 10 keynote reports, seven sessions are focused on the following: New Urbanization, Industrialization and Industrial Restructuring; Agricultural Modernization and "Three Rural Issues"; Technological Development and Application of Big Data and 3S; Environmental Governance in North China and Integrated Development of Coastal Zones; Development and Ecological Civilization Construction of Yellow River Basin; Human-Environmental Interaction and Regional Sustainable Development; Hot Issues and Editing and Publishing on Geography.
