Historical land-use and land-cover changes caused by human activities during the last three centuries have been regarded as one of the five key frame issues in the LUCC project. China, with a history of 5000 years, has had its population boom ever since the early Qing Dynasty (around AD1700), and unprecedented development of national agricultural reclamation had started, left China as one of areas with rapid land-use and land-cover changes. Currently, there are two global historical land use datasets, generally referred as the 'RF datasets' and 'HYDE database', but at the zonal level, these global datasets are widely doubted with coarse resolution and inevitable errors. Academics have tried to reconstruct China's historical land-use and land-cover both quantitatively and spatially, but there are remarkable differences in their results, thus bringing troubles to relevant researches. Since the quantity forms the backbone of cropland restructuring, this paper grounded itself on China's historical records and related research achievements, and reconstructed China's provincial cropland data at the modern boundaries from 1661 to 1985, using a variety of methods based on resources and population, such as factor revision, man-land relationship test, and reclamation trend examination, etc. Our results differ less from HYDE, CHCD and Zhang with an average difference rate of less than 15%. But at the provincial level, our results are closer to CHCD, with 22% of provinces' average difference rate being over 30%. But significant diversities were found in a few provinces and further researches are needed. Then we analyzed China's cropland growth process and regional change characteristics. The results show that ever since the population boom in the Qing Dynasty, China's cropland trebled from 42.4×106 ha in the early Qing Dynasty to 136.9×106 ha in 1985. In terms of the growth rate, the process of China's cropland rise can be identified into five periods. Significant differences existed among the provincial cropland change. At the beginning of the Qing dynasty, China's farming activities mainly existed in the Yangtze River Plain, the Huang-Huai-Hai Plain, Guanzhong Basin and Yinchuan Plain. Thereafter, reclamation activities expanded to outer agriculture areas. Since the founding of the People's Republic of China, Northeast China and Northwest China have been major sources of additional cropland. National policy, disasters, wars, and economic development, are main factors affecting cropland changes.
The aim of this study is to establish several important factors representing the land-use intensification in the cultivated land (denoted by CII) using a multi-dimensional approach for achieving realistic and practical cultivated land use policies. For this reason, the theoretical framework was firstly built to explain the changes of land-use intensification in the cultivated land, and then the variables and index were further developed for characterizing the dynamic trends and driving forces of the land-use intensification in the cultivated land at provincial level. Results indicate that the extent of CII obviously increased during the period from 1996 to 2008 due to the extensively use of fertilizers, machinery and pesticide, the increased labor and capital input as well as the intensified land use. Moreover, the principal component regression results show that the productivity of cultivated land, the economic benefits of cultivated land, the labor productivity and the land use conversion are the main factors affecting the village development. The first three factors play a positive role while the last one produces a negative effect on the land-use intensification in the cultivated land. According to these results, main policies for sustainable intensification in cultivated land are formulated. Firstly, the sustainable pathways for intensification should be adopted to reduce the unsustainable uses of chemical fertilizer, agricultural chemicals and etc. Secondly, the condition for agricultural production should be further improved to increase the cultivated land productivity. Thirdly, it is necessary and helpful for improving labor productivity and land use efficiency from the viewpoint of speeding up the cultivated land circulation.
Based on the sampling data, we analyzed and revealed the floristic characteristics and the relationships of floristic composition between and among 11 mountains on the Loess Plateau. The results indicate that: (1) The floristic composition in forest communities in this region is abundant. Among the 353 plots, 1222 species of vascular plants, belonging to 473 genera of 108 families, were discovered. In those species, 1179 species of 447 genera of 93 families are Angyospermae, 9 species of 7 genera of 4 families are Gymnospermae, and 34 species of 19 genera of 11 families are Pteridophyta. (2) On the regional and local scales, the dominant distribution types of floristic elements at the family and genus levels are temperate origin, especially the north temperate origin. This characteristic is unique on the scale of community level. (3) The first axis of NMDS ordination revealed typical variation range of elevational gradient. The second axis displayed the latitudinal relationship between and among different mountains. The whole study area can be divided into 4 groups with different levels of floristic linkage by hierarchical clustering. Through the comparison of maximum Sørenson similarity coefficient, Helan Mountain, located at the northwest edge of the region, had the weakest relation with other mountains, whereas Taiyue Mountain had the strongest relation with all of the other mountains. (4) Multiple linear regression analysis accounted for 42.1% of the variation within the R/T value (ratio of the tropical to the temperate elements), revealing a significant trend that the R/T value in the region increased at sites with high annual average temperature, whereas it decreased at sites with high elevation. However, no significant tendency of the R/T value with annual precipitation was found in the same analysis.
Runoff calculation is one of the key components in the hydrological modeling. For a certain spatial scale, runoff is a very complex nonlinear process. Currently, the runoff yield model in different hydrological models is not unique. The Chinese LCM model and the American SCS model describe runoff at the macroscopic scale, taking into account the relationship between total actual retention and total rainfall and having a certain similarity. In this study, by comparing the two runoff yield models using theoretical analyses and numerical simulations, we found that: (1) the SCS model is a simple linear representation of the LCM model, and the LCM model reflects more significantly the nonlinearity of catchment runoff. (2) There are strict mathematical relationships between parameters (R, r) of LCM model and between parameters (S) of SCS model, respectively. Parameters (R, r) of LCM can be determined using the research results of SCS model parameters. (3) LCM model parameters (R, r) can be easily obtained by field experiments, while it is difficult to measure SCS parameters (S). Therefore, parameters (R, r) of LCM model can also provide the foundation for SCS model. (4) The SCS model has a linear relationship between the reciprocal of total actual retention and the reciprocal of total rainfall during runoff period. The one-order term of a Taylor series expansion of the LCM model describes the same relationship, which needs to be further studied.
As a typical experimental Soil and Water Conservation District, the Yanhe River basin has long been plagued by soil erosion due to severe human disturbances. The 'Grain-For-Green' project has been practiced to increase grain yield to feed the mass population in starvation and curbed the continually deteriorating ecological situation. It is importantly scientific to explore watershed landscape pattern and hydrological processes. Exerting remote sensing and geographic information technology, this paper firstly analyzed simulated ecological hydrological process in the Yanhe River basin based on SWAT model. On this basis, it applied landscape indices method, land use change on eco-hydrological processes was quantitatively described, particularly those soil erosion influences caused by the change of landscape pattern with the complicated topography and soil type status; then we defined the landscape unit including topography, soil and land use/land cover change (LUCC) information, constructed a comprehensive landscape indices which was closely related to soil erosion, and reflected the coupling relationship between regional landscape pattern change and soil erosion. The results are as follows: (1) this paper constituted the spatial heterogeneity of hydrological response units (HRUs) by several factors such as land use type, soil type, topography, etc. At the landscape level, seven landscape indices were selected with principal component factor analysis, which are DCAD, GYRATE_SD, COHESION, SHEI, TCA, PAFRAC, IJI, etc. Coupled analysis on relationships of landscape indices, annual runoff and annual sediment in each sub-basin, the correlation coefficient of seven selected landscape indices and runoff is very small and cannot pass all significant tests. But correlation among the indices except for TCA and IJI and sediment yield is significant; the absolute value of the correlation coefficient is between 0.3 and 0.5. (2) This paper built Slope-HRU landscape index: coupling relationship between Slope-HRU landscape indices and annual sediment in each sub-basin is very comprehensible, and correlation coefficient is -0.6, which is significantly negatively correlated. Based on 'source-sink' landscape theory of soil erosion, Slope-HRU landscape index was fabricated to reflect the relationship between landscape pattern and soil erosion process to a certain extent. According to the space distribution of R value of Slope-HRU landscape index in 41 sub-basins, the results showed that: in the sub-basin scale, Slope-HRU landscape indices and annual sediment have obvious regional differentiation regularity. And R value spatial variation of Slope-HRU landscape indices and the variation of annual sediment amount were on contrary. On the other hand, the R value increased from southeast to northwest, with annual sediment decreasing from southeast to northwest.
It is important to reconstruct the past environmental changes for unglaciated area in the typical mountains of the Tibetan Plateau and in eastern China by using modern theoretical equilibrium line altitudes (ELAs). Based on the data from 28 meteorological stations of 17 typical mountains, the ELAs were calculated by the methods of Maximum Precipitation Zoneand Empirical Curve (MPC), Maximum Precipitation Zone and Empirical Formula (MPF) and Meteorological Precipitation and Empirical Formula (WPF). Research results show that, MPF is better than WPF through the comparison of the applicability between these two methods in the study areas. The results also indicate that the factors affecting the ELAs are precipitation, temperature, altitude of the meteorological stations and lapse rate of temperature. Based on the in-depth analysis of the principle, parameter selection, computational process and error sources, the authors put forward a newly improved method for calculating modern theoretical ELAs.
Heat and energy exchange between land and atmosphere over the Tibetan Plateau is of great importance for the climatic system in China, east Asia as well as the world. However, there is no systematic observation on atmosphere-land interaction in northern Tibetan Plateau due to rough environmental conditions. In this paper, surface heating and energy/water balance within various temporal scales are analyzed from October 2011 to September 2012 in Shuanghu region. The results show that: (1) the surface heating is positive in the whole year, with an average value of 79.5 W/m2. However, the intensity displays obviously seasonal and diurnal patterns in this region, where it is stronger in summer than that in winter, and also higher in daytime than at night; (2) Surface energy condition varies seasonally, and latent heat exchange is dominated in July and August; (3) surface moisture imbalance occurs in this region, where the annual rainfall and evaporation is 332 mm and 312.9 mm respectively, and the difference is 19.1 mm. (4) The evaporative potential is strong with a humid index of 0.17, belonging to a typically semi-arid climatic region.
The changes of lake levels could keep a record of lake variation on the Tibetan Plateau. Under the background of global warming in recent years, it is of importance to understand regional responses to climate changes by revealing the lake level variation of the inland lakes on the Tibetan Plateau. The paper obtained the time-series of the five typical lake areas and levels from 1972 to 2012 in the south-central Tibetan Plateau, and used the multi-sensor remote sensing data to analyze the variation of lake levels in recent 40 years. The results show that the three inland lakes (Pumo Yumco, Taro Co and Zhari Namco) expanded by 0.89 m, 0.70 m and 0.40 m in water level, respectively, while the two lakes (Peiku Co and Mapang Yumco) presented a decreasing tendency in water level. On the whole, the period 2000-2012 experienced remarkable changes compared with the preceding period (1976-1999). In term of spatial changes, the lakes of Peiku Co and Mapang Yumco, located in south fringe of the Tibetan Plateau, have shown the consistency in lake level changes, and so are the lakes of Taro Co and Zhari Namco in the southwestern part of central Tibetan Plateau.
Based on the data set of 60 weather stations in the east of Qinghai-Tibet Plateau for the period 1967-2012 and the methods of REOF, polynomial fitting, running t-test, the temporal and spatial variations of snowfall are analyzed. Meanwhile, combined with the variation of precipitation and air temperature, the relationship between snowfall and snow cover is discussed. The results indicate the spatial distribution of annual snowfall in the eastern Qinghai-Tibet Plateau is far from uniformity, varying in the range from 1.3 to 152.5 mm. The autumn snowfall is richer in the central part than in the surrounding area, the winter snowfall shows a gradual decreasing trend from southeast to northwest, the spring snowfall shows the same spatial distribution as the annual snowfall. Based on the REOF method, the field of snowfall could be classified into eight subregions: Southern Qinghai Plateau, Northern Tibet Plateau, Qaidam Basin, the southeast edge of Qinghai-Tibet Plateau, northwest of Western Sichuan Plateau, the south edge of Qinghai-Tibet Plateau, northeast of Qinghai Plateau and the valley in Southern Tibet Plateau. As a whole, in the eastern Qinghai-Tibet Plateau, except for autumn, the snowfall shows the obvious interdecadal change, namely, the snowfall was little before the mid-1980s, rich from the late 1980s to the late 1990s, and became little again after the end of the 20th century. By using running t-test method, winter snowfall shifted from the little stage to the rich stage in 1986, the snowfall in winter and spring shifted from the rich stage to the little stage in 1997. Also, in different subregions, the temporal variation of snowfall shows different characteristics. There is close relationship between snowfall and snow depth in the east of Qinghai-Tibet Plateau. The spring snowfall is influenced significantly by air temperature, followed by autumn and winter snowfall. Different from the shift of spring rainfall from the little stage to the rich stage at the end of 20th century, spring snowfall exhibited the shift from the rich stage to the little stage because of the rise of air temperature.
Using the daily minimum temperature data of 121 meteorological stations in Inner Mongolia and its surrounding areas, this paper analyzed the spatiotemporal variation of cold surge and its possible influencing factors in Inner Mongolia during 1960-2012, based on piecewise regression model, Sen+Mann-Kendall model, and correlation analysis. The results show that, (1) The occurrence frequency of single-station cold surge presented a decreasing trend in Inner Mongolia during recent 53 years, with a linear tendency of -0.5 times/10a (-2.4-1.2 times/10a), of which a significant decreasing trend was detected before 1991, being -1.1 times/10a (-3.3-2.5 times/10a), while an increasing trend of 0.45 times/10a (-4.4-4.2 times/10a) was found after 1991. On the seasonal scale, the trend of spring cold surge was consistent with that of the annual value, and the most obvious change of cold surge also occurred in spring. The frequency of monthly cold surge showed a bimodal structure, and November witnessed the highest incidence of cold surge. (2) Spatially, the high incidence of cold surge is mainly observed in the northern and central parts of Inner Mongolia, and higher in the northern than the central part. The inter-decadal characteristic also detected that high frequency and low frequency regions presented a decreasing trend and an increasing trend, respectively, during 1960-1990, while high frequency regions expanded after the 1990s, regions with high frequency of cold surge were mainly distributed in Tol Gol, Xiao’ergou, and Xi Ujimqin Banner. (3) On annual scale, the cold surge was dominated by AO, NAO, CA, APVII, and CQ, while the difference in driving forces among seasons was detected. Winter cold surge was significantly correlated with AO, NAO, SHI, CA, TPI, APVII, CW, and IZ, indicating that cold surge in winter was caused multifactor. Autumn cold surge was mainly affected by CA and IM, while spring cold surge was significantly correlated with CA and APVII.
Taking Acta Geographica Sinica (AGS), Journal of Geographical Sciences (JGS), Annals of the Association of American Geographers (AAAG) and Transactions of the Institute of British Geographers (TIBG) as typical representatives of mainstream journals in China and western countries, according to the information from the respective official websites and documents, and with the background and development history of each journal, the author of this paper makes a comparative analysis on the aims of the journals, report content, internationalization degree, characteristics and their requirement for the articles. The results show that: 1) In terms of the arms of publication, AAAG and TIBG focus on their discipline construction, express definitely their high orientation of international authority, and emphasize contribution of publication to the discipline knowledge, i.e. they have specific and definite requirements for innovativeness, while AGS and JGS, in addition to serving the discipline construction, put forward their objective to serve national economic construction, and emphasize the high level and originality of publication. 2) On the report content, AAAG laid stress on physical geography for its publication in the first two decades, but human geography has been in a dominant position in the following period; attention is also paid to environment science and geographical methodology in recent years; and basic theory study for geography is deepening, but the publication tendency of weakening physical geography becomes a problem faced by the comprehensive geography journals. For the publication of AGS, the ratio of physical geography and human geography is reasonably balanced. JGS pays attention to physical geography and comprehensive research involving physical and human geography. Both of them lay stress on empirical research articles. 3) As for the degree of internationalization, the authors of all selected journals are mainly from their own country, the international authors mostly come from USA, UK, and Canada. The internationalization degree of authors of AAAG is the highest, and the internationalization degree of editors and editorial boards of those journals is similar to that of the authors, with a slight difference, the proportion of international editorial members in TIBG is the highest, but the number of international editorial members of AAAG is the biggest. As international mainstream journals, they are all included by the most important international retrieval systems. 4) As for journal characteristics, AGS and JGS pay more attention to empirical research; AAAG mainly features in the special issues and the presidential speech, and TIBG is mainly embodied in virtual issues and articles' contribution requirements.
