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Taking Niyang River Basin as an example, applying with the indices of landscape pattern, the indices of ecological risk of ecosystems are calculated in this paper, which takes the value of ecological loss of main ecosystem as the evaluation standard and takes into account the impacts of probability or the velocity of main hazards and event of the ecosystem. And the grades of ecological risk are assessed. According to the results of assessment, the ecological risk grades of the basin are divided into five classes. From the first grade risk to the fifth grade risk, the values of regional risk indices gradually reduce. The first grade risk areas mainly distribute in Niyang river and its branches downstream and the surrounding areas of main towns. And the basin area of non-valley region and the headstream regions of the branches are the fifth grades risk areas. This evaluation results provide the basis to the regional sustainable development.

It analyses theCastanopsis carlesii, Camellia oleifera andSymplocos laurina populations' status and role in theCastanopsis carlesii community basing on the study on the dominant population size structure, survival curve and dynamic. It reveals theCastanopsis carlesi population acts as a main role in the community which maintains the stabilization and renovation of the community. The populations ofCamellia oleifera andSymplocos laurina act as a secondary position. The development and succession dynamics of dominant populations is also discussed. The management method is preliminary drawn out which offers a theoretical basis for the evergreen broad-leaved forest restoration and reconstruction in the lower hilly of the west edge of the Sichuan basin.

Characteristics of plant species diversity of two types of grassland communities (alpine meadow and alpine grassland) was examined and the relationship between species diversity and community dynamics was determined using GPS positioning and in situscrutinization of community of alpine grassland in Nakchu prefecture of Tibet Autonomous Region. The result indicated that: ① there was an unobvious difference between grassland communities in terms of richness index of plant, evenness index, dominant index and diversity index. The species diversity index followed the orderKobresia humilis meadow>Stipa purpurea steppe>K. littledalei meadow; ② the original community created high diversity, while the degenerative community suffering from serious disturbance was of low diversity; ③ the diversity of community plants was closely related to changes of species biomass, and the growth and decline of species in the community; ④ grazing disturbance is a key factor of community dynamics, leading to coexistence of various secondary successions of communities, diversified suitable habitats and species diversity improvements.

The sediment load and river sedimentation of the upper reaches of Yangtze River has been undergoing constant changes as complex landform, large mountain area and plentiful precipitation make the drainage area of Yangtze River very vulnerable to water erosion and gravity erosion. Through analyzing the hydrological and sediment load statistics recorded by major hydrological stations along Yangtze River since 1950s, and editing the accumulation graph of annual runoff volume and annual sediment load, we find out that the suspended-sediment of Yangtze river has been decreasing year by year in Wulong Hydrological Station on Wujiang River. Beibei Hydrological Station on Jialingjiang River, Lijiawan Hydrological Station on Tuojiang River and Gaochang Hydrological Station on Minjiang River, Yichang Hydrological Station, Cuntan Hydrological Station along Yangtze River mainstream share the same experience too. But the statistics obtained at Pingshan Hydrological Station on Jinshajiang River shows the sediment load there has increased. Taking ecological construction, hydraulic engineering construction and precipitation changes into consideration, the thesis analyses the causes for the sediment load decrease of Jialingjiang River, Tuojiang River, Minjiang River and Wujiang River and provides us both scientific foundation for further study of river sediment changes of the upper reaches of Yangtze River, and measures to control river sedimentation.

Focusing on the region of Yarlung Zangbo River and the middle reaches of its two tributaries of Nianchu River and Lhasa River in Tibet (Herefter referred to as the “One River and Two Tributaries” region), and based on the data from China 3rd, 4th and 5th population censuses, the article has analyzed change patterns of this region's labor force, Major findings from the study are summarized as follows: ① Compared with the data from the 3rd census, labor force population in 2000 has increased significanlty. ② Children dependency coefficient has dropped, while old people dependency coefficient has changed very slightly with an increase of 0.047% only. ③ Compared 2000 with 1982, illiteracy and semi-illiteracy rate of the population above 15 years old have decreased significantly by 30. 69 percentage points, but still higher than the national average. ④ Women's illiteracy rate has dropped faster than men's, but up to 2000 it was generally quite high. The upgrading of the entire population's overall quality has a long way to go.

In the case study in Agricultural Area of Tibet, the process and characteristics of farmers' land use were surveyed by semi-structural interview questionnaire. By comparing the change of land covers and farmers' land decision in two periods, the spatial connection of them was obtained. And the relations among farmers' land decision, land use change and environment were examined by calculating emergy and value flow. The results show that: hunting the maximal profits is the primary aim of farmers' land decision; farmers' land decision is incompatible with sustainable land use presently; farmers' land decision and land cover can be embodied spatially by each other; the change of farmers' land decision can be monitored by observing the change of land cover, and the sustainability of farmers' land decision can be appraised by calculating emergy and value flow.

Based on the Tibet Autonomous Region's statistic yearbooks and the data from the two household surveys in 2002 and 2004, this paper has comprehensively analyzed the pattern of changes on the farmers and herdsmen's income sources in the Tibet Autonomous Region since 1990 with the main findings as follows: ① The change of income from the labor payment is the fastest; ② There is no regular pattern of income variation for the household economic activities, the farmers and herdsmen's household income generation projects are impacted by the elements like prices and returns, and there is a lack appropriate direction: ③ The income structure of labor payment shows that the income from the farmers and herdsmen working outside grows fastest: ④ The income from the farmers and herdsmen's labor payment correlate positively to their net income per capita; ⑤ From the perspective of the variation by region, labor payment income has changed fastest in the counties of Rutok, Nyerong and Khangmar compared the data from the household survey in 2002 with that of 2004.

Focusing on the 18 counties along “One River and Two Tributaries” region, and based on the data from China 3nl, 4th and 5th population censuses, this article has analyzed the time and spatial changing patterns of the population in this region. The analyses show that since the 3nl population census, total population, average age and total birth rate have all changed considerably: ① Total population has grown, fast, with most counties' annual average growth rate of more than 10. ② In terms of the region's average age, in 2000 the age in the 18 counties is younger than 30 years old. ③ Compared with the 3nl population census, labor force by the 5th census is much younger. ④ Countermeasures are proposed to control population by controlling birth rate as the result of the local resident's quality improvement by education.

Taking Tibet as an example, the functional essentiality degrees of water resources conserving of regions were discussed in this paper. At first, based on the status of regional vegetation, whether the region has the function of water conserving was made certain. And then, according to the impacted objects of water resources conserving, taking into account the demands for water and regional supply capacities of water and the requirement of environmental protection, the functional grades of regional water resources conserving of Tibet were evaluated in this paper.

Based on Universal Soil Loss Equation and methods of mathematics model and GIS analysis, this study classified influence of precipitation, soil, topography and vegetation upon sensitivity of soil erosion into five different degrees which are extreme sensitivity, quite sensitivity, sensitivity, less sensitivity and no sensitivity. Assessment map of each factor was generated separately. Integrated assessment map of sensitivity of soil erosion has also been drawn by overlapping function with Arcinfo. Furthermore, the study analyzed distribution characteristics and spatial difference of sensitivity of soil erosion under special plateau environment of Tibet. According to sensitivity degree, some important controlling regions was confirmed so that departments of water conservancy, traffic management and agriculture could make scientific and reasonable decisions for their respective subject planning.

The Sichuan Basin Region is important composition part of the upper reaches of the Yangtze River. Eco-environment change in this region exerts important effect to the middle and lower reaches of the Yangtze River. The forest cover had hugely been reduced from the 1950s to the mid-1970s, and it has obviously been increased since the end of the 1970s, because that the reforestation project has been implemented. The water source conservation capacity in the studied watersheds has been getting better through study and analysis of the methods for assessment of the forest hydrologic effect. It is found that the method of index of the water source conservation capacity can be used to assessment of the forest water source conservation in the big scale watershed in the studied region. In addition, the retention water capacity of the different vegetation vertical zones in the typical mountain in the north-western Sichuan Basin was studied, its result provides the base for protection and building of the forest ecosystem in the mountain area in the studied region.

Regional eco-security assessment is an intricate, challenging task. In previous studies, the integration of eco-environmental models and geographical information systems (GIS) usually takes two approaches: loose coupling and tight coupling. However, the present study used a full coupling approach to develop a GIS-based regional eco-security assessment decision support system (ESDSS). This was achieved by merging the pressure-state-response (PSR) model and the analytic hierarchy process (AHP) into ArcGIS 9 as a dynamic link library (DLL) using ArcObjects in ArcGIS and Visual Basic for Applications. Such an approach makes it easy to capitalize on the GIS visualization and spatial analysis functions, thereby significantly supporting the dynamic estimation of regional eco-security. A case study is presented for the Tibetan Plateau, known as the world's "third pole" after the Arctic and Antarctic. Results verified the usefulness and feasibility of the developed method. As a useful tool, the ESDSS can also help local managers to make scientifically-based and effective decisions about Tibetan eco-environmental protection and land use. (C) 2010 Elsevier Ltd. All rights reserved.