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A comprehensive analysis of normalized difference vegetation index (NDVI), land-use type, and digital elevation model (DEM) data by using the geographic information system (GIS) showed that the index had increased over time in 84 prefectures that were part of the Grain for Green Project. SPOT Vegetation (Satellite Pour l’Observation de la Terre Vegetation, or satellite observation of the earth’s vegetation) data and the NDVI showed that compared to 2000, in 2015 2.05% of the arable land in the study area was no longer cultivated and that 25% of the farmland with slopes steeper than 35° and 2.68% of the moderately sloped farmland (2-35°) had been turned into forests. The arable land had been converted mainly to woodland and grassland. The interpretation of thematic mapper (TM) images showed that forest cover had increased significantly (by nearly 22%); that vegetation cover was less than 10% over 95.27% of the area; and that the area with high vegetation cover had increased significantly. Superposition analysis of TM images and DEM data showed that the intensity of soil erosion had generally decreased, with the areas under mild and pole-strength soil erosion decreasing by more than 10%. However, the Grain for Green Project has failed to check severe soil erosion so far. At present, although 60% of the study area is covered by forests, the extent of change in the degree of vegetation cover varied over time, and the spatial distribution was uneven, being higher in the east than in the west. It is therefore important to continue to strengthen governance through such projects.
The haze satellite map produced by NASA in 2013 showed a "Gray Great Wall" in the sky from Beijing to Hong Kong, indicating serious air pollution in China. The air pollutants and greenhouse gases can be reduced through engineering measures known as industrial gas emission and haze reduction (GGE&H reduction), as well as through green GGE&H reduction by ecosystems such as forests and wetlands that play significant roles in carbon sequestration and atmospheric environmental purification of air, soil, and water. Compared with the industrial GGE&H reduction, the green GGE&H reduction is lower in investment and operational cost, but offers more ecological benefits and therefore is more economically feasible. In this review the roles of green GGE&H reduction are summarized and its future potential is highlighted. The possible approaches to enhance the capability of green GGE&H reduction in China are discussed.
In order to investigate the effects of climate factors on the tree-ring width of Quercus acutissima in the rocky mountain area of northern China, correlation analysis and response function analysis were used to determine the relationship between the tree-ring width of Quercus acutissima and climate factors. The results showed that: 1. The residual (RES) chronology of the Quercus acutissima forest contained richer environmental information than standard (STD) chronology and was suitable for response analysis. 2. Tree-ring width had a general positive correlation with the average monthly temperature, a significantly positive correlation (P<0.05) with the April temperature, and a highly significantly positive correlation (P<0.01) with the May temperature of the current year. Tree-ring width had a positive correlation with precipitation from March to June in the current year, especially a significantly positive (P<0.05) correlation with May and June precipitation, and a negative correlation with precipitation from September of the previous year to February of the current year; however, the correlation coefficients with precipitation were basically lower than the coefficients with temperature basically 3. Temperature and humidity index were the main climate factors that influenced the tree-ring width of Quercus acutissima, followed by precipitation.
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