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With disturbed and undisturbed belts during the construction of Qinghai-Tibet highway as test objectives, this paper studied the effects of human engineering activities on the permafrost ecosystem in northern Qinghai-Tibetan plateau. The results showed that the thickness of permafrost active layer was smaller in disturbed than in undisturbed belt, and decreased with increasing altitude in undisturbed belt while no definite pattern was observed in disturbed belt. Different vegetation types had different effects on the thickness of permafrost active layer, being decreased in the order of steppe > shrub > meadow. In the two belts, altitude was the main factor affecting the vertical distribution of soil moisture, but vegetation type was also an important affecting factor if the altitude was similar. Due to the human engineering activities, soil temperature in summer was lower in disturbed than in undisturbed belt.

It is of significance to establish an integrated evaluation system of snow disaster in northern pastoral areas. Based on the NOAA satellite digital images, field observation data, and maps of grassland type and seasonal pastureland, this paper selected the winter and spring pasturelands in Aletai region of Xinjiang as the main area of snow disaster-remote sensing monitoring. With affecting factors of economy and the characteristics of natural resource distribution comprehensively analyzed, and using 3S techniques and field survey information, a fundamental information processing model for integrated evaluation of snow disaster was built up, and snow disaster-spatial evaluation indices and damage level systems were constructed. Natural and social systems and 20 indices were selected in snow disaster evaluation indicator system. Four principal factors, i.e., snow cover area, snow depth on grassland, persistence days of low temperature, and livestock death rate, were used as the grading indices of snow disaster damage level, and the models of snow disaster identification and loss estimatation were set up to quantitatively analyze snow disaster. The results indicated that the system could accurately reflect the details of snow hazard grade and the situation of a disaster in temporal and spatial scales, which would help to carry out the dynamic monitoring and scientific estimatation of big area's snow disaster in pastoral region.

Grassland degradation, an important problem in grassland management, has affected the sustainable development of animal husbandry in Alatai region of Xinjiang. Based on the analysis of the community features, ecological service value and multiple functions, and main function of grassland types in the regional development, the classified management for grassland was designed. The results showed that Alatai grassland could be divided into three sectors, i.e., ecological function region, economic function region and mixed function region. The ecological function region made up 164.66 x 10(4) hm2 or 16.73% of total Alatai grassland, and the grassland types included alpine meadow, alpine rangeland, swamp, mountain desert steppe, mountain steppe desert and part of plain desert. For the ecological function region, the main management strategy was to prohibit grazing and cropping. The economic function region of 116.33 x 10(4) hm2 accounted for 11.82% of the total Alatai grassland, the grassland types included mountain meadow, flat meadow and meadow steppe, and the main management strategy to enhance the productivity was agricultural measures, such as fertilization and irrigation. The mixed function region which included mountain steppe, plain desert steppe and most part of plain desert was 703.21 x 10(4) hm2 or 71.45% of total Alatai grassland, and the main management strategy was rotational grazing.

Based on the theories of sustainable development of forest resources, this paper constructed an index system for the integrative evaluation on the sustainability of forest resources in Bailon River forest region of Gansu Province. After calculated the index values of five strategic levels and twenty measure levels, the degree of harmony (DH) was obtained, with which, the sustainability of test forest resources could be evaluated. The DH value was 0.5320 in 1996 and 0.6100 in 2000, which was smaller than the theoretic value of 0.7000, and hence, this forest region belonged to non-sustainable development, but made some progress for its sustainability.

A field study was conducted in the hilly and valley regions of Loess Plateau in Gansu Province to analyze the root system development ability of several alfalfa (Medicago sativa) cultivars. Eight introduced cultivars and one local cultivar were arranged in the same site. The secondary roots of alfalfa cultivars grew mainly from the taproot underground 10-20 cm depth, and there were no secondary roots below 50 cm depth. The total amount of secondary roots of Sandili and Ameristand 201 was the biggest, and that of Longdong alfalfa was the lowest. The volume and biomass of different cultivars were decreased from 0-10 cm depth to below 50 cm depth, except those of Sandili and Ameristand 201 at 20-30 cm depth was bigger than at 10-20 cm depth. The biomass of Ameristand 201 was 170.54 g and bigger than that of others, and that of Longdong alfalfa, which was 22.4% of Ameristand 201, was the lowest. According to cluster analysis on 9 alfalfa cultivars, Sandili, Ameristand 201 and Amerigraze 401 were suitable for planting on the hills and valleys of Loess Plateau due to their root system development ability.

The dynamics of forage supply and nutrition requirements of sheep were monitored for a whole year under alpine grassland conditions in Sunan County, Gansu Province. The digestion and metabolism of grazed sheep were determined in different seasons. The results showed that the DE(9.76 MJ), CP(21.53%) and the ratio of crude protein to digestible energy (22.06 g.MJ-1) of forage were the highest in Spring, while the herbage dry matter yield and dry matter intake (60.51 +/- 3.42 g.W0.75kg-1.d-1) by grazed sheep were the lowest. Supplementary DM especially in energy should be provided. The ratio of crude protein to digestible energy was 17.62 g.MJ-1 in Summer, and was somewhat higher. The nitrogen utility of the forage would be improved, if energy feed was supplemented. Both the quality and quantity of forage produced in grasslands in Autumn could meet the sheep requirement. Whereas during Winter, neither forage yield nor nutritive value was sufficient for sheep, and the contents of the DE and CP of forage were the lowest in the year, which were 4.30 MJ and 4.63%, respectively. The nitrogen metabolism of sheep was negative. Therefore, DM, especially DE and CP, should be supplemented. To improve the conditions, it was necessary to develop seasonal animal husbandry, and combine the subsystems into coupling systems.