Yanzhao Yang

Relief degree of land surface and its influence on population distribution in China

The relief degree of land surface (RDLS) is an important factor for describing the landform at macro-scales. This study defines a concept for RDLS and applies the concept for population distribution study of the entire country. Based on the concept and macro-scale digital elevation model datum and ARC/INFO software, the RDLS at a 10 km×10 km grid size of China is extracted. This paper depicts systemically the spatial distributions of RDLS through analyzing the ratio structure and altitudinal characters of RDLS in China. The conclusions are drawn as follows: the RDLS in more than 63% of the area is less than one (1) (relative altitude is less than 500 m), reflecting the fact that most of RDLS in China is low. In general, the RDLS in the west is larger than that in the east and so is the south than that of the north in China. The RDLS decreases with the increase of longitude and latitude and the change of RDLS at the latitudes of 28°N, 35°N, 42°N, as well as at the longitudes of 85°E, 102°E, 115°E could reflect the three major ladders of China. In the vertical direction, the RDLS increases with the increase of altitude. Analysis of the correlation between RDLS and population distribution in China and its regional difference shows that the R2 value between RDLS and population density is 0.91 and RDLS is an important factor influencing the spatial distribution of population. More than 85% of the people in China live in areas where the RDLS is less than one (1), while the population in areas with RDLS greater than 3 accounts only for 0.57% of the total. The regional difference of correlation between RDLS and population within China is significant and such correlation is significant in Central China and South China and weak in Inner Mongolia and Tibet.

Rubber plantation and its relationship with topographical factors in the border region of China, Laos and Myanmar

Rubber plantation is the major land use type in Southeast Asia. Monitoring the spatial-temporal pattern of rubber plantation is significant for regional land resource development, eco-environmental protection, and maintaining border security. With remote sensing technologies, we analyzed the rubber distribution pattern and spatial-temporal dynamic; with GIS and a newly proposed index of Planted Intensity (PI), we further quantified the impacts and limits of topographical factors on rubber plantation in the border region of China, Laos and Myanmar (BRCLM) between 1980 and 2010. The results showed that: (1) As the dominant land use type in this border region, the acreage of rubber plantation was 6014 km2 in 2010, accounting for 8.17% of the total area. Viewing from the rubber plantation structure, the ratio of mature- (≥10 year) and young rubber plantation (<10 year) was 5:7. (2) From 1980 to 2010, rubber plantation expanded significantly in BRCLM, from 705 km2 to 6014 km2, nearly nine times. The distribution characteristics of rubber plantation varied from concentrated toward dispersed, from border inside to outside, and expanded further in all directions with Jinghong City as the center. (3) Restricted by the topographical factors, more than 4/5 proportion of rubber plantation concentrated in the appropriate elevation gradients between 600 and 1000 m, rarely occurred in elevations beyond 1200 m in BRCLM. Nearly 2/3 of rubber plantation concentrated on slopes of 8°–25°, rarely distributed on slopes above 35°. Rubber plantation was primarily distributed in south and east aspects, relatively few in north and west aspects. Rubber planted intensity displayed the similar distribution trend. (4) Comparative studies of rubber plantation in different countries showed that there was a remarkable increase in area at higher elevations and steeper slopes in China, while there were large appropriate topographical gradients for rubber plantation in Laos and Myanmar which benefited China for rubber trans-boundary expansion. (5) Rubber plantation in BRCLM will definitely expend cross borders of China to the territories of Laos and Myanmar, and the continuous expansion in the border region of China will be inevitable.

Studying the thermal anomaly before the Zhangbei earthquake with MTSAT and meteorological data

The occurrence of a thermal anomaly before an earthquake has been widely reported in the last 20 years. In these reports, Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) night-time data are the most widely used data, and the distance between the thermal anomaly and the epicentre is about 100–1000 km. Here we use Multi-functional Transport Satellite (MTSAT) -1R geostationary data, with high temporal resolution and surface air temperature data, to study the thermal anomaly before the Zhangbei earthquakes in China. The combination of these two datasets showed some advantages over AVHRR and MODIS data – they are less affected by clouds, while the surface air temperature difference showed a good relation between the epicentre and thermal anomaly. Their distance is less than 100 km. This provides a possible way to estimate future epicentres within reasonable errors.

The change in population density from 2000 to 2010 and its influencing factors in China at the county scale

Studying the change in population distribution and density can provide important basis for regional development and planning. The spatial patterns and driving factors of the change in population density in China were not clear yet. Therefore, using the population census data in 2000 and 2010, this study firstly analyzed the change of population density in China and divided the change in all 2353 counties into 4 types, consisting of rapid increase, slow increase, slow decrease and rapid decrease. Subsequently, based on the partial least square (PLS) regression method, we recognized the significant factors (among 11 natural and social-economic factors) impacting population density change for the whole country and counties with different types of population change. The results showed that: (1) compared to the population density in 2000, in 2010, the population density in most of the counties (over 60%) increased by 21 persons per km2 on average, while the population density in other counties decreased by 13 persons per km2. Of all the 2353 counties, 860 and 589 counties respectively showed rapid and slow increase in population density, while 458 and 446 counties showed slow and rapid decrease in population density, respectively. (2) Among the 11 factors, social-economic factors impacted population density change more significantly than natural factors. The higher economic development level, better medical condition and stronger communication capability were the main pull factors of population increase. The dense population density was the main push factor of population decrease. These conclusions clarified the spatial pattern of population change and its influencing factors in China over the past 10 years and could provide helpful reference for the future population planning.

Research on the suitability of population distribution at the provincial scale in China

The relationship between population distribution and resources, environment and social-economic development has a significant influence on the human development. This paper set up a set of index system and model methods for the assessment of the coordination between population and resources, environment and social-economic development, and it quantitatively evaluated this coordination at the provincial scale in 2000 and 2010 respectively. Based on this set of index system, the suitability degree and the spatial-temporal pattern of population distribution at the provincial scale were carefully characterized. The restriction of population distribution at the provincial scale was graded and classified, and the coordinated development strategy of population, resources, environment and social economy was finally put forward. The results showed that: (1) The environmental suitability of population distribution at the provincial scale was generally high in China, which tended to be stable from 2000 to 2010. (2) The restriction of water and land resources at the provincial scale was generally strong in China, but it tended to be weak from 2000 to 2010. (3) The coordination degree between the social-economic development and population distribution at the provincial scale was mostly at a middle level, which was in the positive upward path from 2000 to 2010. (4) The suitability of population distribution at the provincial scale was mostly at a middle level, all of which was rising from 2000 to 2010. (5) The coordination degree between population distribution and resources, environment and social-economic development at the provincial scale was divided into four grades, including basic coordination, relative coordination, awaited coordination and urgent-needed coordination. (6) The basic ways to promote the coordinated development of population, resources and environment in different regions in China can be summarized as: implementing the strategy of population agglomeration and evacuation, guiding the orderly flow of population, optimizing the spatial distribution of population and drawing up the spatial planning of population development.

The past, present, and future of population geography in China: Progress, challenges and opportunities

Population geography (PopGeo), although a sub-discipline of human geography, should have been well developed in China in light of its national population size and unique demographic issues, regional socio-economic development, and biophysical differences. Yet it typically lags behind the development of its parent disciplines, especially demography and geography. Specifically, PopGeo in Chinese higher education is still at a low level in terms of the three major aspects of disciplinary development: academic majors for higher education, academic conferences, and journals. The research content of PopGeo in China has focused on the growth, composition, change, distribution, and carrying capacity of population at the meso- and macro-spatial scales. As the most populated country in the world, questions about how and why the population changes, where the population settles and migrates to, its maximum carrying capacity, and how to guide sound development of population matter to society and the economy, are always important topics in the PopGeo studies in China. In contrast, some new population phenomena such as human space–time behaviors (commuting, remittances, and friends’ interaction), popular in the scientific community abroad, are not fully investigated at the micro-level. Presently, PopGeo in China may face both challenges and opportunities because of the adjustment of fertility policies and implementation of national new urbanization plans at the national level. It is this occasion that calls for a state-of-the-art review of the development of PopGeo since the 1980s, the turning point of an increasing number of PopGeo studies in China. We aim to reveal the current status of PopGeo in China to the world, and shed light on its further study.

Study on the Balance of Agricultural Water and Land Resources on Ningxia Plain

Abstract The article puts forward the process and means of regional water and land balance research, and then from two scenarios which are the balances under natural regulation and human intervention, calculated and analysed the balance between water and land on Ningxia Plain. For the balance under natural regulation named farmland water balance, using farmland water resource balance equation, the research estimated the monthly farmland water balance of 8 major crops for all of the 12 counties on Ningxia Plain in the period of 1960–2001; for the balance under human intervention, the research estimated land-use water balance equation of the counties in 2000, and calculated the balance between land use and water resources including irrigating water of all the 12 counties on Ningxia Plain. Results showed that ①precipitation can not meet the water demand of the crops for growth and development on Ningxia Plain, and water shortage is the primary character of farmland water balance under natural regulation, ②the diversity of water and land balance of different counties is distinctly influenced by the crop structure, water quantity for irrigation and irrigation level. ③Irrigation water could meet the crop water demand on Ningxia Plain in 2000, but there was not much space to expand irrigating cultivated land.The article puts forward the process and means of regional water and land balance research, and then from two scenarios which are the balances under natural regulation and human intervention, calculated and analysed the balance between water and land on Ningxia Plain. For the balance under natural regulation named farmland water balance, using farmland water resource balance equation, the research estimated the monthly farmland water balance of 8 major crops for all of the 12 counties on Ningxia Plain in the period of 1960-2001; for the balance under human intervention, the research estimated land-use water balance equation of the counties in 2000, and calculated the balance between land use and water resources including irrigating water of all the 12 counties on Ningxia Plain. Results showed that ①precipitation can not meet the water demand of the crops for growth and development on Ningxia Plain, and water shortage is the primary character of farmland water balance under natural regulation. ②the diversity of water and land balance of different counties is distinctly influenced by the crop structure, water quantity for irrigation and irrigation level. ③Irrigation water could meet the crop water demand on Ningxia Plain in 2000, but there was not much space to expand irrigating cultivated land.

Land cover classification in qinghai-tibet plateau a case study on shannan prefecture

Qinghai-Tibet Plateau is an important part of global terrestrial ecosystem, and plays a significant role in regional sustainable development. The land cover classification in Qinghai-Tibet Plateau has been a topic research in recent years. Digital elevation model (DEM) have proved to be an effective aid to improving land cover classification. The objective of this study is to assess the contribution of incorporating DEM data in image classification to improve the spectral information accuracy. Two different bands combining methods, band I and band 3 of Moderate Resolution Imaging Spectrometer (MODIS), combining with Normalized Difference Vegetation Index (NDVI), band 1 and band 3 of MODIS, incorporating with NDVI and DEM, were used to classify the land cover of Shannon Prefecture. Results showed that the DEM data considerably improved the classification accuracy, the overall classification accuracy in test area improved 12.89%. As for most land cover types, the method combing DEM improved the classification accuracy at the same time, the producer accuracy of alpine meadow steppe and temperate steppe improved 23.06% and 27.03%, the user accuracy of cultivated land and alpine steppe improved 26.42% and 21.45%.

Grid-based study on the potential crop productivity of cultivated land in China

By intearating the land use dada extracted from remote sensing imaging, meteorological data and crop production model in GIS environment, this paper takes winter wheat as a case to calculate and evaluate the potential crop productivity of cultivated land limited by radiation and temperature, namely photosynthetic thermal productivity in China based on 1 km x 1 km grid. The results show: With the changing of spatial position, the winter wheat photosynthetic thermal productivity of cultivated land in China is usually changing from 3000 kg/ha to 14150 ka/ha. Furthermore, we compare the potential productivity of provinces with actual yield of ten main production provinces of winter wheat by combining Chinas administrative boundary map and potential land productivity map. In ten main production provinces, winter wheat PTP of most provinces is close to or more than 7000 kg/ha except Sichuan provinces is 4211 kg/ha. The highest is Jiangsu province (9930 kg/ha), the lowest is Sichuan province (4211 kg/ha). There are five provinces where winter wheat utilizing efficiency of ;radiation and temperature are higher than 50%, Sichuan province is the highest (71%), the lowest is Shaanxi province, due to lack of water, only 35%.