Liu Shuzhen

The classification and assessment of freeze-thaw erosion in Tibet

Freeze-thaw erosion is the third largest soil erosion type after water erosion and wind erosion. Restricted by many factors, few researches on freeze-thaw erosion have so far been done at home and abroad, especially those on the assessment method of freeze-thaw erosion. Based on the comprehensive analysis of impact factors of free-thaw erosion, this paper chooses six indexes, including the annual temperature range, annual precipitation, slope, aspect, vegetation and soil, to build the model for relative classification of freeze-thaw erosion using weighted and additive methods, and realizes the relative classification of the freeze-thaw erosion in Tibet with the support of GIS software. Then a synthetic assessment of freeze-thaw erosion in Tibet has been carried out according to the relative classification result. The result shows that the distribution of freeze-thaw eroded area is very extensive in Tibet, accounting for 55.3% of the total local land area; the spatial differentiation of freeze-thaw erosion with different intensities is obvious; and the difference in distribution among different regions is also obvious.

Evaluation of eco-environmental stability based on GIS in Tibet, China

By making an evaluation index system and using Analytical Hierarchy Process (AHP) to determine the evaluation factors weights, this paper builds the valuation model of Eco-environmental stability of Tibet and uses the overlay function of raster-GIS (geographic information systems) to make a result map and finds the distribution characteristics of Eco-environmental stability of Tibet based on the analysis of result map. The study shows that the Eco-environmental stability of Tibet is almost good and the unstable region which is only 9.78% of the total area of Tibet is distributed in the middle and low reaches of Yarlung river. To protect the Eco-environmental of the unstable area from farther degenerating, the government should pay more attention on the Eco-environmental construction work on this area.

Impacts of Soil Moisture Content and Vegetation on Shear Strength of Unsaturated Soil

It is analyzed that the impacts of vegetation type and soil moisture content on shear strength of unsaturated soil through direct shearing tests for various vegetation types, different soil moisture contents and different-depth unsaturated soil. The results show that the cohesion of unsaturated soil changes greatly, and the friction angle changes in little with soil moisture content. It is also shown that vegetation can improve shear strength of unsaturated soil, which therefore provides a basis that vegetation can reinforce soil and protect slopes.

Classification and assessment of freeze-thaw erosion in Tibet, China

Based on the analysis of existing relevant research result, a theoretical basis for the defining freeze- thaw erosion zones of Qinghai-Tibet Plateau was been put forward, and a equation for calculating the altitude of the lower bound of the freeze-thaw erosion zones of Qinghai-Tibet Plateau was been established in this paper. Moreover, the freeze-thaw erosion zones in Tibet was been identified by using Geographical Information System (GIS) software. Next, based on the comprehensive analysis of impact factors of freeze-thaw erosion, this paper chooses annul temperature range, slop and vegetation as three indexes, works out the criteria for relative classification of freeze-thaw erosion, and realizes the relative classification of the freeze-thaw erosion in Tibet under the support of GIS software. Then, a synthetic assessment of freeze-thaw erosion in Tibet was been done according to the relative classification result.

Study on the Restoration of Vegetation in Arid-Hot Valleys Along the Jinshajiang River

Based on the features of environment and the fact of successful artificial afforestation, the paper points out that the restoration of vegetation in Arid-hot valleys along the Jinshajiang River should be implemented mainly by planting sparse - arbor/ shrub/ tussock Combination. Four ways to restore vegetation in the area are given in the paper.

Quantitative assessment on endangerment degree of rare animal and plant species in Tibet, China

It is of profound theoretical and practical significance to study endangerment status of rare species in Tibet. Index system is firstly set down for quantitative assessment of rare animal and plant species, then endangerment degree of wildlife under special state protection are calculated, which is expressed by value E. The results reveal that Yunnan snub-nosed monkey (Rhinopithecus bieti), Himalayan tahr (Hemitragus jemlahicus) and Gigantic Cypress (Cupressus gigantea) have the highest E respectively in animals and plants. According to value E, all species are categorized into 4 ranks: critically endangered (0.6–0.8), endangered (0.4–0.6), vulnerable (0.2–0.4) and lower risk (E ⩽ 0.2). By comparison of the first five animals and plants of the highest E, each sub-ecozone bears a distinct identity.

Plant Community Characteristics of Trampling Disturbance Kobresia humilis Community along the Road in Naqu,Tibet

The change of plant community character during recovery succession processes of high mountain meadow in Naqu, Tibet, was investigated. The results show that there are 41 plant species in the inventoried quadrates. The high-plants in four big families plays important roles in natural vegetation recovery, whileKobresia play an important role in climax communities. The plant species components changed with each succession stage. The plant species were mainly annual and biennial during the early succession stage, and perennial during the medium; and dominated byKobresia humilis during the late.Potentilla bi furca andPotentilla tanaletfolia were both found in all stages. The accumulated number of family, genus, and species during the succession process varied quadric with the stages. The main plant community characteristics varied logistically with the succession stages except the height. The community characteristics mainly affected by dominant species which were changed in same rhythm. The biomass under ground was far more than the upground. The plant diversity inflated in the medium stage.

Impacts of Human Activities on the Land Desertification in the Dry-Hot Valley of the Jinshajiang River

The research area, Yuanmou County, is located in the downstream of dry-hot valley of the Jinshajiang River. There is an average annual precipitation of 619 mm with 85% of the total amount concentrated in the rain season from June to August. Problems of the land desertification, such as soil erosion, exposure of land, rock fragments, land sandstonization and soil degradation etc. by runoff water are very serious in Yuanmou County. The distribution, characteristics of the land desertification are described. Impacts of human activities on the land desertification are analyzed. It is found that rapid growth of population, reclaiming precipitous slope, random deforestation and over-grazing are main reasons to cause the soil acceleration erosion and the land desertification.

Impact of water environmental characteristics in Dry-Hot valley of Jinsha river on soil desertification

Based on the field investigation and the analysis of soil moisture curve, it is clearly shown that there is a positive relationship between vegetation coverage rate and soil moisture capacity and soil depth in dry-hot valley of the Jinsha River, and also there is a desertification process with seasonality. It is suggested that the basic factor of desertification in the area is water deficiency (seasonal drought and low soil water capacity) and the direct dynamic of desertification is soil erosion. Some effective countermeasures are presented, of which water-saving planting and irrigation techniques should be firstly applied in the studied area.

Effect of Socio-economic Factors on Soil Erosion: A Literature Review

Based on the summarization of the research on man-made accelerated erosion,this paper introduced the four social-economic factors which affect soil erosion including population growth,policy,economic development and land use changes,and reviewed the research methods for the social-economic factors affecting soil erosion both at home and abroad.After that,it is proposed that three aspects of the research need further study: interdisciplinary studies,social-economic models and regional differences.