Siberia is an important sensitive area with regard to global environmental change. Due to the limited availability of high resolution remote sensing data, previously there was a general lack of in-depth understanding of land cover and change in Siberia. Based on the land cover classification of China's 30 m global land cover (GLC) data product (GlobeLand30) in 2000 and 2010, this study analyzed the progress of land cover change in Siberia between 2000 and 2010 using spatial statistical method and land cover type transition matrix. Land cover changes in Siberia showed significant spatial and temporal variations between 2000 and 2010. Overall, the area that experienced most clear land cover change was west Siberia. The area of forests and grasslands decreased substantially and the change mainly took place in the traditional forest industry regions. The total area of wetland significantly increased and this change occurred mainly in the River Ob and Yenisei in west Siberia. Cultivated land decreased slightly mainly in the traditional agricultural region of the southwest. Built-up areas expanded rapidly, which mainly distributed in cities along the Trans-Siberian Railway. Land cover change in Siberia showed distinct temporal and spatial disparities primarily due to two reasons: industrial development and climate warming..

：Land use form of rural settlements transformed profoundly in the process of rapid industrialization and urbanization in China. By selecting seven rural settlements of different geomorphic types in the Aluke'rqin Banner located in the farming-pastoral transitional zone in Inner Mongolia and examining land use change through a survey, we discuss the relationship between morphological features of the rural settlements and farmers’ livelihood. Participatory rural appraisal method and geographic information system and remote sensing techniques were employed in the survey and analysis. The results show that: (1) Morphological features of rural settlements were closely related to livelihood of rural households, especially with regard to the quantity and quality of cultivated land and grassland and livelihood activities. Along with the increase of population, conversion of grassland to cultivated land, and diversification of rural household livelihood activities, rural pastoral settlements transformed into agro-pastoral settlements. (2) Land use types of agro-pastoral settlements were gradually diversified through time. Before the Reform and Opening-up of China in 1978, agricultural production was the dominant livelihood activity of rural households. Homestead was the primary land use type of rural settlements. After the Reform and Opening-up, however, livelihood activities of rural households gradually diversified and became increasingly non-agricultural. Commercial land, industrial warehousing land, and land for public service provision expanded rapidly in the rural settlements. (3) Homestead takes a significant share in agro-pastoral settlements. Cropping and animal husbandry are important productive activities for rural households. Corresponding to the livelihood demands of rural households,within the settlements homesteads are divided into production and ancillary production lands including colony house, vegetable garden, and warehouse in rural households. Both per capital construction land and homestead area in the case study settlements are larger than the national standard, which indicates an adaptive land use in response to the livelihood demands of the agro-pastoral resettlements. Therefore, the authors recommend that the governments should take concrete measures in the process of rural residential land consolidation that take into consideration the livelihood demands of rural households in this particular area.

The Jiangsu muddy coastal zone is one of the key bases of cropland complementary resources in China. In 2009, the Chinese government approved the development plan of the Jiangsu coastal zone, wherein the tidal flat will be reclaimed and developed into new farmland. Potential land productivity in the coastal area can reflect its capacity to supply food for the country, and is the basis for maintaining the sustainability of the regional agricultural production. There exist various potential land productivity models in China and worldwide. Models based on the process of crop physiology and ecology were used at the field scale, such as the Crop-Environment Resource Synthesis System (CERES) and World Food Studies (WOFOST). Land productivity models based on light, temperature, precipitation, and soil properties—the Classification and Evaluation Techniques of Farmland and Evaluation System of Land Productivity (ESLP)—have been used in China. However, the soil validation coefficients in these two models are based on the evaluation of soil quality and did not consider the relationship between crop yields and soil properties. This article takes the reclamation zones in Rudong County, Jiangsu Province as a case study and attempts to improve the soil validation coefficient in potential land productivity models. It incorporates the percentage of soil fertility contribution (PSFC) and soil salinity factor as soil validation coefficients into the model of potential land productivity to reflect the quality of land. We used the field survey data on rice and wheat yields to verify the feasibility of the potential land productivity model in the coastal area of China. The results show that the PSFC of rice production in the Jiangsu coastal area was about 55%~59%. The PSFC of wheat production in the study area was 50%~80%. The rice and wheat production in the reclamation zones in 1951 and 1974 was not affected by soil salinity because the soils in these reclamation zones were not saline. The rice and wheat production in the reclamation zones in 1982 and 2007 were influenced by soil salinity. The salinity factors of rice and wheat production in the reclamation zones in 1982 were 0.73 and 1.00, respectively. The salinity factors of rice and wheat production in the reclamation zones in 2007 were 0 and 0.35. In 2007 the soil in the reclamation zone was no longer suitable for growing rice paddy. The rice and wheat potential productivity corrected by PSFC in the un-desalinized reclamation zones in 1982 were 12235.84 and 6502.23 kg/hm². The rice and wheat potential productivity corrected by soil salinity in the un-desalinized reclamation zones in 1982 were 15677.42 and 10329.39 kg/hm². The rice and wheat potential productivity corrected by PSFC and soil salinity in the un-desalinized reclamation zones in 1982 were 8934.97 and 6502.23 kg/hm². The actual field yields of rice and wheat (9750 and 6000 kg/hm²) are consistent with the potential productivity corrected by PSFC and soil salinity, and is far less than the potential productivity corrected by soil salinity. Improved fertilization can increase land production. The result of this research can be useful for evaluating newly reclaimed farmland resources and for calculating crop production in the coastal reclamation zones.

：The Qinghai-Tibet Plateau is a hotspot area for global climate change research and a key area for ecological protection in China. Land cover change research in this area can significantly contribute to optimizingland use pattern and improving ecological services and natural conditions of the region. Among various methods for land cover change detection, linear spectral unmixing (LSU) is an effective approach to monitor land cover change by using remote sensing technology. In this study, we chose Naidong County in Tibet as the study area and adopted the linear spectral unmixing technology to detect the ratio of vegetation, bare soil, and rock for each pixel of three Landsat TM/ETM images from 1988, 2000, and 2010. The vegetation component of the result was compared with NDVI. The results show that: (1) The study area has high proportion of mixed pixels, and LSU can deal with the complex features of land cover changes effectively. (2) The proportion of bare soil reduced evidently while rock and vegetation coverage increased from1988 to 2010. It proves that vegetation cover had recovered to some degree while rocky desertification expanded rapidly. (3) Through comparing the vegetation component with NDVI we conclude that LSU is applicable for the identification of land cover change of the Qinghai-Tibet Plateau.

Using the 3S (RS, GIS, GPS) technologies, quantitative analysis method of landscape patterns, and the 30 m resolution land use/land cover data, this study examines the spatiotemporal characteristics of land use/land cover change in the grassland restoration areas in China from 2000 to 2010. We apply two parameters land use transfer matrix and land use dynamic degree to explore the speed and regional differentiation of land use change. This study analyzes the characteristics of landscape patterns at the class and landscape levels in the study area and explores the ecological effect of land use pattern and regional ecological processes. The results show that: (1) Grassland, woodland, wetland, farmland, tificial surface, and others were the main landscape types in the study area in the past decade. The ecosystem structure was stable. About 0.37% of the total grassland area in 2000 experienced change in land use/land cover types. The area of woodlands, wetlands, farmlands, and tificial surface expanded. The area of "others" has declined. (2) The dynamic degree of regional land use was less than one percent in the recent ten years. The speed of land use and land cover change was low, and regional differentiation of change between the provinces was small. (3) The matrix of the landscape did not change in the study area. Landscape fragmentation index values decreased progressively; landscape diversity rose continuously; landscape aggregation and continuity decreased slightly; the landscape maintained relative integrity. The grassland restoration program implementation evidently improved the structure and stability of the land use / land cover.

Satellite remote sensing is an important technique for cropland resources survey, while time series of remote sensing images, particularly, are of great practical significance for cropland extraction. Optical remote sensing imagery is largely affected by illumination and atmospheric conditions, which limits available satellite images within a year, especially where cloudy or rainy weather frequently occurs. Synthetic Aperture Radar (SAR), on the other hand, is able to acquire data throughout the day under any weather condition. However, owing to the influence of speckle noise, very little work has been done to use SAR image time series for feature extraction. This study examines the applicability of SAR image time series for cropland extraction, and Xuzhou City in Jiangsu Province was chosen as the study area. A total of 11 ENVISAT ASAR images covering the study area and dated from December 2009 to December 2010 were selected to establish a SAR time series as experimental data. Thirty cropland sampling regions with the size of 5 pixels × 5 pixels were visually chosen to calculate the consistency of cropland backscatter signatures in the temporal domain, at both neighboring location (inside each sampling region) and remote location (beyond the sampling regions). Euclidean distance method, correlation method, and dynamic time warp (DTW) method were then adopted to extract cropland pixels in the study area. The experiment results show high backscattering consistency for neighboring cropland pixels, with a coefficient of variation of 9.96%. A lower but still satisfactory backscattering consistency was derived by remote cropland pixels in the study area, with a coefficient of variation of 15.27%. Despite the inherent speckle noises of SAR data, the general characteristics of time series for cropland backscatter coefficient correspond well with crop calendar. For the three selected methods, correlation method performed best, which produced a correctness of 86.25% and completeness of 80.70%. Euclidean method took the second place, with a correctness of 76.40% and a completeness of 71.93%. DTW achieved the lowest accuracy, with a correctness of 62.15% and completeness of 77.78%. This research shows that as a new data organizing form, time series of SAR images can be used for cropland extraction effectively.

Many studies have demonstrated that land use and cover change (LUCC) has played a key role in global environmental change. The contemporary land cover is a result of human land use in the history. In order to simulate the LUCC's influence in climate and ecosystem, it is important to have a historical LUCC dataset, especially high- resolution land cover dataset. However, in China, such national coverage dataset is still missing, and this has limited the national environmental change simulations. So there is an urgent need to develop an effective way to reconstruct historical cropland distribution with high-resolution grids. Considering the complexity of the natural environment in China, in this study we developed a separate reconstruction method. First, we divided China into four regions based on a qualitative analysis: the traditional cultivated region, the northeastern region, the northwestern region, and the Qinghai-Tibet Plateau. This division is mostly consistent with other recent studies except for the northwestern region, which differs slightly from common delineation. Second, in every region we examined the relationship between cropland distribution and various natural and human factors and built a reconstruction model. In the traditional cultivated region and the northeastern region, we found that elevation, slope, and population density were the main contributing factors to cropland distribution. In other regions, how-ever, population density was the sole significant contributing factor. This model was then used to reconstruct the cropland distribution of China in 1913, 1933, 1950, 1970, 1990 and 2000 at a spatial resolution of 10 km×10 km. By comparing the reconstruction result with remote sensing data interpretation for 1990, we found that the reconstructed cropland distribution data are reliable not only at the county scale, but also at the grid scale. The comparison between the reconstructed change and the remote sensing data-derived change from 1990 to 2000 also supports this view, that is, the separate reconstruction method developed in this study is effective for capturing cropland change over time. The reconstructed dataset indicates the follows. (1) In the northeastern region, the cropland area slightly decreased at the beginning of the People's Republic of China in 1949; up to 1970, the cropland area had recovered and the modern distribution pattern formed; thereafter, the Sanjiang Plain was brought into agricultural development gradually. (2) In Xinjiang in western China, the first cropland development climax appeared in the republican period influenced by the agricultural policy; the second climax appeared between the 1950s and the 1970s, but most of the cropland was distributed in the area of the Tianshan Mountains. (3) Change in cropland distribution of the Qinghai-Tibet Plateau was not notable, but the area had increased much; the spatial distribution of cropland in the traditional cultivated region also did not change significantly, but the reclamation ratio has increased. In conclusion, cropland area in China had increased in the early 20th century and then decreased, and the inflection point was likely in the late 20th century. This trend occurred not only in cropland area, but also in reclamation ratio. However, the change varies in different regions and is more pronounced in the northeastern and northwestern regions.

With intensifying human activities global ecological and environmental problems have become increasingly pressing. Therefore the study of global change has become more prominent. Obtaining accurate land cover information in a timely fashion is critically important for such research. With the development of remote sensing science and technology and application, numerous studies have the issue of land cover classification using remote sensing image. In this study, the Beijing-Tianjin-Hebei region was selected as a study area for land cover classification using MODIS data. The 16-day MOD13Q1/EVI data in 2013, MOD09Q1 (Band1, 2) and MOD09A1(Band3- 7) products in May 2013 were used as the basic data. Harmonic analysis method was employed to remove clouds and noises of the whole year's EVI, so that it can better reflect plant phenology. Then, the processed MOD13Q1/EVI data, surface albedo of MODIS/Ref1-7, modified normalized difference water index (MNDWI), normalized difference soil brightness index (NDSI), and normalized difference water index (NDWI) were integrated to construct three schemes of CART decision tree to investigate the land cover classification of the Beijing-Tianjin-Hebei region. The three band combinations are scheme1: 23 phases of EVI of 2013; scheme2: 23 phases of EVI of 2013 plus B1-B7 of MOD09; and scheme3: scheme2+MNDWI+NDSI+NDWI. The results show that the overall classification accuracy of the three schemes reaches 86.70%, 89.98%, and 89.98% respectively. Their Kappa coefficients are 84.94%, 88.66%, and 90.20% respectively. Therefore, MODIS images with various classification characteristics, combined with the decision trees can achieve higher precision land cover classification. This proves the feasibility of the proposed method for land cover classification at the regional scale.

At present, farmland abandonment is a widespread problem in many poor mountainous areas of China. This type of land use change in sensitive environment has positive impact on the ecological security of these areas, but affects negatively on grain production and food security. For national food security reasons, large amounts of basic farmland in mountainous areas are still required. Therefore the contradiction between ecological security and food security is hard to resolve. Farmland transfer, however, may offer a solution to this problem. Understanding the characteristics and determinants of farmland transfer- in provides insights for decision making on the rational distribution of basic farmland and grain for green projects, but existing research is insufficient for mountainous areas. Based on a field survey of 1015 households in the "two wings" of Chongqing using participatory rural appraisal (PRA) tool, this study analyzes the basic characteristics of farmland transfer- in at plot level. It quantitatively analyzes the influencing factors on the farmland area that farming households transfer in by using the Tobit model. The results show that: (1) As free-of-compensation transfer is common in the study area, the surveyed households are unwilling to transfer out large plots located close to residence. However, farming households who transfer in farmland tend to choose plots with relatively good quality or convenient for farming, and have a low demand for plots with relatively poor production conditions. Thus these plots are more likely to be abandoned. (2) The farming households who transfer in farmland are often small farmers with low cropping income and their plots are generally small. With regard to farmland management, the surveyed farming households tend to grow cash crops on the plots that they transfer in, while labor and fertilizer input to these plots are lower than that of own plots. (3) The Tobit model analysis suggests that farm labor force, household farming income, quantity of farming equipment, and cultivated area have significant positive impacts on the farmland area that households transfer in. On the other hand, age of household head, average plot area, and Wulong County have significant negative impacts. Other variables, such as off-farm income, quantity of household livestock, distance from market, road, and Wushan County, have no significant impact on the farmland area that farmers transfer in. (4) In order to foster land transfer market in the mountainous areas, targeted measures need to be adopted by the government, such as developing land consolidation projects, adjusting grain production subsidies and cropping structure, increasing the amount of agricultural machinery purchase allowance, and so on. This study also identified issues that require further research, for example, why free-of-compensation transfer is common in the mountainous areas and what is the role of the government in farmland transfer.