8. Research achievement: 8.1. Effects of simulated rainfall and nitrogen supplement conditions on community and productivity of alpine meadow The response of synthetic dominated ratio (SDR) and above-ground biomass in different plant groups of grassy species, weeds and sedge species were not significantly different between 20% - 40% rainfall reduction and 20% - 40% rainfall augmentation conditions. It was more favorable to the growth of grassy species during summer under the treatment of 100% increased snow in winter and spring while the reverse was the case to the growth of other plant populations. It indicated that sedges were the most tolerant to the fluctuation in environmental resources followed by grassy species and weeds. The sedges were net sensitive under various rainfall treatments indicating their strong adaptation to the flunctation of environmental resources. Simulated experiment indicated that rainfall increased by 20% - 40% could moderately reduce the effect of lower precipitation in water-deficiency year, while the decreased rainfall by 20% - 40% could intensify the effect of drought. The response of grasses to nitrogen addition was more significant than that of non-leguminous forbs. The synthetic dominated ratio (SDR) of grasses increased, and that of non-leguminous forbs decreased with the increase of nitrogen, whereas the SDR of sedges and leguminous forbs were not significantly affected by nitrogen fertilizer. Plant diversity was decreased in the low short Kobresia meadow and forage quality increased with the increase of nitrogen fertilizer. Index of meadow quality (IMQ) was the highest at 150 kg N/ha plot, and had no significant difference between 150 kg N/ha and 300 kg N/ha plot. Excessive nitrogen application did not improve the IMQ. Response of above-ground biomass of plant groups was lagged when compared with plant diversity and IMQ. Total above-ground biomass significantly increased with the nitrogen application. There were different responses to the nitrogen application of above-ground biomass among plant groups. The results indicated that the above-ground biomass of grasses was significantly increased with nitrogen-fertilizer application, and was decreased in forbs. The responses to nitrogen application of plant groups were more affected by precipitation and especially its distribution in July. Therefore, the status of soil water after nitrogen application was a crucial factor in the responses by various plant groups. 8.2. Experiment and practice for sustainable development of astoral-animal husbandry on the alpine meadow pasture Increasing supply of fodders by planting oat and vetch and/or other fast-growing species can afford the raising of sheep and yaks during the long winter. This in turn reduces the slaughter period and makes animal production more efficiently. An experiment was carried out to investigate the effect of a mixed planting with oat and vetch on the yield of fodder. The results indicated that fodder yield of the mixed planting was higher than in a monoculture. The optimum mixture proportion and density of oat and vetch are 3:1 (Oat / Yetch) and 800 plants/m2, respectively. The longer raise period and lower slaughter rate constitute the most important limiting factors for livestock production on high frigid meadow, and the main problem in achieving an optimal production structure is the light weight of 1-year-old sheep that does not meet the market requirement. These two problems would be solved by fattening. There are generally 3 methods of livestock fattening in the region: 1) grazing fattening, the most economic method with the weight of sheep increased by 20% -30 % after grazing for 80 - 90 days when herbages are flourishing; 2) Combined fattening mostly for the sheep with poor condition at late autumn with the supply of some nutritious feedstuff to these sheep and then slaughter them within 30 - 40 days; and 3) Indoor fattening that could free from the limit of seasonal changes with weight of sheep increased by 160 - 190 g/d. This would provide mutton for the market during the meat lacking season, and the herdsmen would gain more profit. The economic benefit of meadow management will be increased and livestock fattening will reduce grazing pressure on meadow for the following year. Livestock fattening is accepted widely not only in many pasture areas but also in agricultural areas for higher profit from sheep breeding in increasing income and improving living standard of the people. Various ways of increasing sustainable development efficiency and economic profit of alpine meadow ecosystem management have been developed. This includes optimizing structure of the animal population, livestock fattening, restoration of degenerated grassland, fodder plantation, optimizing of grazing intensity, and so on. Integrated environmental rehabilitation, sustainable utilization, and moderate inputs of energy and materials management systems have been developed and implemented in 6 pilot households, sponsored by the Haibei Alpine Meadow Ecosystem Research station, CAS. 8.3. The contribution to the atmospheric greenhouse gas from alpine meadow ecosystem The CO2 emission rate had significant daily fluctuations and seasonal dynamics from alpine meadow ecosystem. Maximum and minimum rates of CO2 emission appeared at 14:00 - 16:00 and 6:00 - 8:00, respectively. Maximum and minimum daily amplitude were 797.75 mg/m2h (August 16.) and 197.33 mg/m2h (June 1), respectively. The CO2 emission rate during daytime was greater than that at night time. Rate of CO2 emission varied with changing of phenological periods, and the pattern was in the following order: Exuberance > Withering > Greening. The daily CO2 emission rates during the plant growing period, the range of maximum and minimums values were 441.72 ?155.29 mg/m2h, 681.06 mg/m2h (July 16), and 176.65 mg/m2h (June 1) respectively. The rate of CO2 emission in the degraded Mat Cryo-sod soil was lower than that of undegraded Mat Cryo-sod soil with daily average value was below 137.47 mg/m2h. Correlation analysis indicated that CO2 emission rate was significantly correlated with air temperature, soil surface temperature, and soil temperatures at 5 cm, 10 cm, 15 cm, 20 cm, and 30cm depths. The temperature was one of most dominant factors affecting the rate of CO2 emission in Mat Cryo-sod soil. Soil CO2 emission is the production of microbial decomposition into soil organic substances and plant roots respiration, and it is affected by soil biotic and environmental factors. Daily changes in soil CO2 emission from Mollic-gryic Cambisols was paralleled with daily trends of air temperature and soil surface temperature, but the peak of air temperature delayed 2 hours than that of soil CO2 emission and soil surface temperature. Soil surface temperature had strong effect on CO2 emission and both exhibited a highly significant correlation. However, it became weak at 5-cm depth underground. Soil temperature (at 0 ?C 30 cm depths, especially 10 cm), fungal hyphal biomes (within 0 ?C 20 cm depths), humic-C extant (within 0 ?C 20 cm depths) and living content of above-ground caused seasonal variations of soil CO2 emission. They all exhibited a significant or extremely significant levels to soil CO2 emission. Excessive grazing made the increase of soil capacity and the decrease of porosity and organic substances, which could reduce soil CO2 emission. The CO2 emission between livestock intensities of 2.55 and 5.35 sheeps/km2 was significantly different by F-test. Precipitation and soil moisture have not affected soil CO2 emission of Mollic-gryic Cambisols. Sudden climate change would lead to strong fluctuation of soil CO2 emission. The values of carbon dioxide emission from different land-use of alpine meadow varied with seasons. During the growing season (May to September), the order is as follows: Potentilla fruticosa shrub meadow (1871.40 g/m2) > Kobresia humilis meadow (1769.63 g/m2) > Degraded P. fruticosa shrub meadow (1495.60g/m2) > Degraded K. humilis meadow (1191.26 g/m2). The order during non-growing period (October to April) is as follows: K. humilis meadow (661.46 g/m2) > P. fruticosa shrub meadow (550.90 g/m2) > Degraded K. humilis meadow (502.50 g/m2) > Degraded P. fruticosa shrub meadow (384.50 g/m2). The order for the whole year is as follows: K. humilis meadow (2431.09 g/m2) > P. fruticosa shrub meadow (2422.30 g/m2) > Degraded P. fruticosa shrub meadow (1880.10 g/m2) > Degraded K. humilis meadow (1694.06 g/m2). This difference were not only decided by the soil microbial activities and soil characteristics, but also had close correlation to duration of breezing period. 8.4. Effectsof prolonged UV-B radiation on photosynthesis and adaptation in some alpine plant species From the results of photosynthesis in 7 plant species, we could find that most species were quite adaptable to supplementary UV-B radiation. However, this changed with leave ages and weather conditions. Plant development could be influenced by supplementary UV-B radiation, and this should be studied in more details in the future, especially its significant effect in plant ecology. The activities of some enzymes have been studied, but in order to be certain, the seasonal changes should be done in the future. The leave thickness was studied in Gentiama straminea and Saussurea superba, the increase of leave thickness could influence the photosynthesis.