The impact of land use and land cover changes on land surface temperature in a karst area of China

Satellite images have been used extensively to study temporal changes in land use and land cover (LULC) in China. However, few studies have been conducted in the karst areas despite the large area and population involved and the fragile ecosystem. In this study, LULC changes were examined in part of Guizhou Province of southern China from 1991 to 2001 based on Landsat Thematic Mapper (TM) images of November 7, 1991, December 5, 1994, and December 19, 2001. Land surface temperature (LST) and normalized difference vegetation index (NDVI) were computed based on LULC types. The results show that agricultural land decreased, while urban areas expanded dramatically, and forest land increased slightly. Barren land increased from 1991 to 1994, and then decreased from 1994 to 2001. These changes in LULC widened the temperature difference between the urban and the rural areas. The change in LST was mainly associated with changes in construction materials in the urban area and in vegetation abundance both in the urban and rural areas. Vegetation had a dual function in the temperatures of different LULC types. While it could ease the warming trend in the urban or built-up areas, it helped to keep other lands warmer in the cold weather. The study also reveals that due to the government's efforts on reforestation, rural ecosystems in some of the study area were being restored. The time required for the karst ecosystem to recover was shorter than previously thought.     

Land Use and Land Cover Change Analysis and Prediction in the Upper Reaches of the Minjiang River,China

Scientists have aimed at exploring land use and land cover change (LUCC) and modeling future landscape pattern in order to improve our understanding of the causes and consequences of these phenomena. This study addresses LUCC in the upper reaches of Minjiang River, China, from 1974 to 2000. Based on remotely sensed images, LUCC and landscape pattern change were assessed using cross-tabulation and landscape metrics. Then, using the CLUE-S model, changes in area of four types of land cover were predicted for two scenarios considering forest polices over the next 20 years. Results showed that forestland decreased from 1974 to 2000 due to continuous deforestation, while grassland and shrubland increased correspondingly. At the same time, the farmland and settlement land increased dramatically. Landscape fragmentation in the study area accompanied these changes. Forestland, grassland, and farmland take opposite trajectories in the two scenarios, as does landscape fragmentation. LUCC has led to ecological consequences, such as biodiversity loss and lowering of ecological carrying capacity.     

Effects of Land Management Change on Spatial Variability of Organic Matter and Nutrients in Paddy Field: A Case Study of Pinghu,China

The Household Responsibility System initiated in the late 1970s in China has brought a profound change to its rural economy. The shift from the collective farming system to individual family farms has changed land management. The change, including fertilization and crop systems, may have significant effects on soil quality and agro-environmental sustainability. However, very little research is being carried out on the impact of reformed land tenure systems on the spatial variability of soil nutrients. In this study, geostatistics was applied to analyze changes in the spatial variability of soil organic matter and nutrients in paddy fields in Pinghu County, China after 20 years of land management change. In 1984 and 2002, 617 and 131 locations were selected, respectively, for collecting surface soil samples to analyze soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK). From 1984 to 2002, variability of the SOM and TN changed from strongly to moderately spatial-dependent, and the variability of AP remained weakly dependent on space, but that of the AK changed from moderately to weakly spatial-dependent. That the trend of the variability of four soil properties in 2002 became weaker than that in 1984 showed that the extrinsic factors (soil management practices, such as fertilization) weakened the effect by intrinsic factors (soil formation factors, such as soil parent materials) owing to a long period of land management change. The temporal geographic maps of the SOM and nutrients spatial distributions suggested that the concentrations of the SOM and nutrients had been changed to different extents during the period. Significant increase in AP and decrease in AK were noted. The changes were likely due to the imbalance between N, P, and K fertilizers and increased grain yield.     

Evaluation of the economic and environmental impact of converting cropland to forest: a case study in Dunhua county, China

The Sloping Land Conversion Program (also known as "Grain for Green" or the Upland Conversion Program) for converting cropland to forest is one of China's most ambitious environmental initiatives, and is one of the world's largest land-conservation programs with a budget of RMB 337 billion (over US$ 40 billion). Although environmental impacts have played a vital role in the general reasoning and argumentation for forest plantations, environmental impact analyses have often received less attention than economic analyses in the planning of plantation forestry projects. The overall goal of this paper is to evaluate the program's environmental impact considering the farmer's interests and the potential social benefits due to carbon sequestration in different scenarios based on household and field survey data in Dunhua County. Our findings are that: (1) in many cases, the program did not give adequate consideration to land productivity and environmental heterogeneity when selecting plots; (2) more than half of the reforestation plots were on flat cropland (slopes of less than 5 degrees ); (3) in five of the eight townships, net incomes on reforested land were substantially above or below previous crop incomes, raising questions about the efficiency of the allocation of compensation to farmers participating in the program; (4) the potential carbon co-benefit increased the NPV of the program by 5954-7009 RMB/ha. In conclusion, we recommend that more attention should be paid to the quality of reforestation programs rather than just their scale and note that consideration of potential carbon sequestration co-benefits enhances the benefits of cropland conversion programs.     

Social and economic impacts of carbon sequestration and land use change on peasant households in rural China: a case study of Liping, Guizhou Province

Numerous innovative approaches to mitigate effects of excessive emission of greenhouse gases (GHGs) on global climate change are being proposed and formulated. Sequestering carbon to terrestrial ecosystems represents one of the important clean development mechanisms. Reforestation through converting various non-forest lands to forests is undoubtedly an important dimension of carbon sequestration. Using Liping County in Guizhou Province as a case region, this study examines the perceived change in social and economic livelihoods of peasants and the factors responsible for the variations in the changes. The results of the study reveal that socio-economic changes associated with the government-financed project are multifaceted and profound. Because of the financial subsidies provided by the central government, this environmental action in many aspects can be regarded as a poverty reduction measure in the underdeveloped area where rural poverty is widespread. A majority of peasant households have benefited from project participation. The land conversion project with continued financial support also contributes to the social transformations of traditional rural society in remote areas to a more mobile, less subsistence agriculture-based, and open society.