Land use and land cover change (LUCC) plays, an important part in the studies of global environmental change and sustainable development. Land quality change can particularly reflect the impacts of human socio-economic activities on environment. By means of land classification for LUCC to different times of remote sensing information, picking-up vegetation index (NDVI), and assaying field repeated soil samples, as well as statistical analysis, this paper studies land use and land cover quality change of past several to 21 years in the Yellow River Delta. The conclusions are as follows: 1. In the Yellow River Delta, although sediment loads carried by the Yellow River result in rapid expansion of land area, the main driving force of LUCC is derived from human economic activities. 2. In the macroscopic view, land use and land cover quality change shows a tendency to improve because of water conservancy projects, vegetation cover and increase of per unit area yield of crop so that the overall ecological environment is improving in the mass. But in the microcosmic and point analysis, there are different and imbalanced development within the region. The task of transforming saline land is still arduous. The hidden trouble of soil fertility depression can not be neglected. 3. Both natural force and human action can engender environmental positive and negative effects. But it is more difficult to restore the latter made by human activities. The paper brings forward measures for sustainable land use. Finally, there is a discussion about issues of further study.
Vegetation plays an important role in the energy, matter and momentum exchange between land surface and atmosphere and the change of vegetation is mainly caused by climate variation and human activities. Therefore, it is necessary to study the relationship between climate factors and inter-annual change of vegetation, which will help us to understand global change. In order to understand the effects of rainfall on vegetation cover, we selected the Yellow River Basin in China as the study area to assess the inter-annual change of fractional vegetation cover in the Yellow River Basin, and analyzed the relationship between rainfall and fractional vegetation cover using 8 km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to1999. The data are from NASA Pathfinder AVHRR Land data sets. The spatial distribution and dynamic change of fractional vegetation cover were studied by using yearly maximum NDVI. The results show that in spite of inter-annual fluctuations, there exists an inclining trend of fractional vegetation cover for the whole basin, which is different from the trend of annual rainfall. The inclining trend may be caused by human activities while inter-annual fluctuation may be caused by climate factors. Finally, the correlation coefficients between NDVI and rainfall in different periods (annual rainfall, rainfall in flood and non-flood seasons) were computed for every pixel to assess the effect of rainfall on fractional vegetation cover change. The results show that there is good relationship between NDVI and rainfall in the Yellow River Basin, especially in arid and semi-arid steppe zones, and inter-annual change of fractional vegetation cover is mainly affected by flood season rainfall. However, human activities can reduce the effect, for example, the effect of rainfall on NDVI is small in irrigated cropland.
Using the data of monthly mean temperature, maximum and minimum temperature from 1961 to 2000 in Tibet, the linear trends of the annual and seasonal temperature are analyzed. The results show that, the mean temperature displayed warming trend in most parts of Tibet, especially in autumn and winter. The asymmetry was detectable in Tibet, the type of asymmetry was mainly the increase of Tmax and Tmin, while Tmin increase was bigger than that of Tmax. The increase of Tmax occurred mainly in summer and Tmin in winter. The decrease of daily temperature range (DTR) was in all seasons (except summer). Warming was displayed at all latitudes, the increase was the strongest in spring and autumn, secondly in winter, the trend was stronger on the higher altitude than on the lower altitude. In addition, the linear trend of the warming for annual mean temperature over Tibet during the past forty years indicated an increase of 0.26 oC / 10 a, it is obviously higher than in other parts of China and in the whole globe. There were more anomalous cold years in the 1960s, whereas anomalous warm years in the 1990s.
Wind erosion has played the major role in shaping Mu Us landscape. Although Mu Us Sand land is a hot spot, of research, the detail of wind erosion in Mu Us has been poorly understood. On the basis of observations in Mu Us Desert, we determine the threshold of wind velocity and present sand transport equations on bare and vegetated land. Furthermore, we discuss the quantitative relationship between vegetation cover and sand transport. We get a quite good understanding of the effect of vegetation on wind erosion.
Through a case study on PC-related manufacturing in Dongguan, this paper examines the transformation of global-local ties in the development of local clusters in the context of Pearl River Delta, a foreign investment driven industrialized area in China. Following a brief theoretical review on the industrial cluster and the dynamics of global PC market environment, the changing structure of local PC production network is analyzed. The development of the local PC production network is divided into two stages: first, from the late 1980s to the early 1990s, export oriented manufacturing plants with strong global linkages but weak local linkages were established under the export processing regulations; second, from the middle 1990s till now, the local electronics intermediates production network kept growing with the Taiwan PC makers flood-in. The changing structure of local industrial linkages is intervened with the dynamics of social relations between different agents, which leads to the challenges of institutional innovation in the development of local clusters. Then, we analyze the congestion of custom, a prevalent problem faced by most local PC makers at present, and the ongoing bargain on regulations between overseas investors and local policy-makers. We argue that this institutional bottleneck of local production network is among the results of the structural changing, and cannot be solved only by readjustment at operational level. The forthcoming entrance WTO is a step towards improvement. However, the establishment of local common sense on new market rules among investors, local officials and labors is still a long way to go.