Developing and utilising desert grassland by fostering its advantage and avoiding its weaknesses has important ecological, economic and social significance. In this paper, the fundamental ecological problems and optimal objectives were analysed. The management principles were discussed with the emphasis of practising management strategies at the regional scale and using the system theory. The expansion of the artificial forage production should be considered as a driving force, and the combination of agricultural and animal husbandry is necessary for bringing the whole effect of mountain-plain-oasis compound system into full pay. That is the core of the regulation principles. The ecologically optimal model for proper grassland use of South Zhungar desert grassland region was put forward as a representative case.

The soil water-salt attributes as well as its dynamics a direct influence on species composition of plant communities in arid region. According to the measurement of the soil water-salt dynamic(soil salt content up to 1m depth, water table and the mineralization degree) and the grassland investigation, a index for characterise the water and salt grades were proposed, and the relationships of the water-salt-plant system in different grassland types were discussed. The natural grassland types near the Grassland Ecology Research Station, Hutubi, Xinjiang, were divided into five forms: marshy lowland meadow, saline lowland meadow, heavy saline lowland meadow, salt desert and heavy salt desert.

The potted plants of Puccinellia tenuiflora were respectively treated with different concentrations of NaCl solutions. Biomass, K, Na and Cl contents, absorption and transportation rates from plant roots to shoots at the seedling and elongating stages were measured and compared.The maximum shoot biomass of the seedlings and elongating plants was appeared under the treatment of 66 and 134mmol/L, and maximum root biomass was under that of 66mmol/L. The ratio of plant roots to shoots at seedling stage were linearly de- creased with the increase of the NaCl concentration, while those at elongating stage were lower than that at seeding stage, and has no significant changes with the cnange of salt concentrations. Na and Cl contents in both shoots and roots, and Na and Cl caused osmoregulation capacity in shoots, absorption and roots, transport rates of K, Ma and Cl from roots to shoots were higher during elongation stage than that during seedling stage. However K/Na ratios, selectivity of K over Na calculated by selective ratio was lower during elongation stage than during seedling stage. Absorption and transportation rates of plants to K during seedlings and elongation, and to Na and Cl during elongation had significant correlation with their relative growth rate (RGR), while those to Na and C1 during seedlings had no correlation with RGR. Based on numerical change of K, Na and Cl contents, it is inferred that ions played different roles during osmoregulation under stress. Cl was used to maintain "basic osmotic potential" of shoots relative to the control solution without strees, and also to maintain osmoregualtion. K did not significantly cause osmoregulation, numerically, and played a little role in maintenance of "basic osmotic potential" of shoots.

The experiments were conducted to investigate the effect of ecological factors, such as treatment solutions and temperature on the salt tolerance of the Puccinellia tenuiflora seeds. The relative germination ratio were used as a measurement for its salt-tolerance. The experiments includs 2 treatment temperatures, 3 seedlots and 4 solutions (PEG, NaC, CaCl2 and NaSO4) with the different osmotic potentials or concentrations. Relative germination was linearly decreased as the osmotic potential of the solutions decreased, and the regression coefficient and intercept of regression equation reflected magnitude of osmotic and ionic effect of the solution on germination, respectively. No evident difference of the relative germination in salt solutions exited among the seedlots with significantly different germination in water. Solution types and ambient temperature during germination affected salt-tolerance of seeds through modifying ionic effect of solutions, but they caused no alteration of osmotic effect of the solutions on germination. The osmotic effect of the four solutions on germination of Puccinellia tenuiflora was a decrease of the relative germination rate by 52.3 % with a 1.0 mpa decrease of osmotic potential. The increase of the seed germination rates by treatment of the 3 osmatic potential salt solution were 14. 0%, 15. 1% and 21. 6% in comparison with that of PEG, under a temperature of 10～25℃. The ionic effect of NaCl solution was 17.0% lower under 15～25℃ than that under 10～25℃

Maowusu sandy grassland is an ecotone in the transitional zone of animal husbandry and agriculture in North China. In this study, a quantitative hierarchical classification is committed on the sandy grassland landscape ecological elements with TWINSPAN, which is widely used in vegetation science. Then a sandy grassland ecological classification system is drawn. DCA, which has a similar algorithm in comparison with TWINSPAN, is applied in the ordination of sandy grassland landscape ecological elements. Other multivariate analysis such as stepwise regression is done to clarify the relationship between the classified landscape ecological types. Maowusu sandy grassland is rich in landscape ecological types. Groundwater-table, sand depth, and parent material types are the key factors controlling the genesis and succession of the landscape ecological types. Finally a landscape ecological succession module of Maowusu sandy grassland is given. According to this research, TWINSPAN and DCA are useful in landscape ecological quantitative classification and ordination.

A managerial advisory system,ASSG, for the hilly sandy grassland ecosystems in north China was developed. The system combined empirical knowledge of local experts of ecosystem management and the theoretical research results on soil water dynamics to produce optimal managerial strategies in terms of land use ,planting species/variety and optimal coverage of plants. A three-step interactive inference procedure together with structured knowledge bases was used to guide users through the consulting process step by step. At each step of the inference, users are provided with multiple options derived from a corresponding knowledge base, and the next inferential step is based on users choice in the current step. This interactive scheme of inference gives users maximum flexibility to obtain appropriate consulting results.The main body of the system was implemented in Turbo Prolog, a descriptive language for expert system development. The optimal plant coverage model based on soil water dynamics was encoded into Turbo C and was imbedded into the main body of the program by using the multiple language programming. Sample consultation runs of the system indicated that the system operated smoothly and produced reasonable results of managerial strategies.

A grazing-induced degenerated Artemisia frigida community has been monitored till 1993 since it was fenced in 1983 in the middle reaches of the Xilin River. The vegetation was measured by 10～20 quadrats of 1m2 once per 15 days during the plant growing season from May to September each year. The species standing crops, density, height, water content, and their flowering stem number were recorded. The similar monitoring were simultaneously conducted in the well protected communities dominated by Leymus chinensis and Stipa grandis. The dynamics of spatial distribution pattern of plant population has also been monitored with improved method of quadrat variance. Based on a comparative analysis of these data, the community features were summarised and the driving force for restoration was discussed. The results are as follows: 1. The degenerated Artemisia frigida community is in a stable state corresponding to a certain grazing intensity. Degeneration degree depend on the grazing intensity. 2. The species composition of the degenerated A. frigida community has no significant difference from that of primary plant community dominated by L. chinensis. The grazing disturbance has a big effects on the proportion of plant population in community, but no much effects on the species richness for the succession series between A. frigida and L. chinensis communities. 3. The spatial hetterogeneity is low in degenerated community, and will increase with the restoring succession due to the patches of some populations’ expansion. 4. The species-biomass relationships in degenerated community and in primary community fits to a log-normal distribution model. The restoration succession fits to a broken-stick distribution model. 5. A significant character of the degenerated grassland is the low productivity. The productivity is only 1/3 of the primary community, and palatable forage proportion is only 50 % ～ 70 % of the primary community, so the usable productivity decreased to only 30% of that of primary community. 6. The plant colonising ability and the relative surplus resource in the degenerated community is the driving force for its restoration

The restoration dynamics of the Artemisia frigida community, one of the grazing-induced degenerated community of the zonal vegetation dominated by Leymus chinensis+Stipa grandis, was monitored after the fence during 1983 to 1995. The temporal data set were analysed. The results were as follows:1. Based on the replacement of dominant species and the result of principle component analysis, the process of restoring succession can be relatively divided into 4 stages, that is, the stage of degenerated community, the initial stage of restoration, the Agropyronmichnoi dominating stage, and the Leymus chinensis dominating stage.2. A feature of staircase transitions alternating with sub-atable treads is shown by change of community productivity during the restoring succession. The first transition started as soon as the grassland was fenced (in 1984), and the productivity level climbed to the first tread; the second transition was taken place in 1990, the productivity jumped second tread that approached the productivity of primary community.3. The relationship between community productivity and water resource were dependent on the stage of restoring succession. The standing crops of the community maintained the a standing crop of 166g·m-2 A precipitation favorable year with a rainfall of 176 mm during plant growth season had no significant effect to the raise of community productivity in the first sub-stable state stage. While the relationship between community biomass and precipitation was significant in the second sub-stable state stage. The water requirement for producing dry material were between 1.1～1.6mm·g-1,that is, the maximum water resource utilization ratio of community was 1.1mm·g-1,and the maximum production can be reached when the ratio was 1.6mm·g-14. The dots number of the studied community density is around 271.5 plants·m-2. The density became high and low alternatively and rhythmically, being the instinct mechanism of community restoration. The restoring succession speed could be measured by the half-change of communities. A 1.78 half-change. happened during the 10 years restoration.5. The restoration could be accelerated by adjusting grazing intensities and other techniques in accordance with the rhythmic regularity of the restoring succession.

Evapotranspiration (ET) and transpiration (TR) of Sueade corniculata community were measured using artificial lysimeters in plant growing season in Songnen grassland. The climate data, including air temperature, air relative humidity, solar radiation, wind speed, soil moisture and plant water storage were simultaneously recorded. The results showed that the ET and Tr of Suaeda corniculata community varied significantly in different month. The diurnal variations of Tr had close relation with radiation, air temperature, relative humidity and wind speed. Solar radiation played a leading rote. The precipitation, ET, soil water storage and canopy water storage were main parts of soil-vegetation-air water flow system in Songnen grassland. In the whole growing season the water deficits of Suaeda corniculata community was not serious (6.3mm), but it changed significantly among months, the water deficits in June was serious (30.1mm).

The biological approaches for improving alkaline-saline grassland were studied. The first method is to improve the physical-chemical characters of alkaline-saline soil by setting up a litter layer and sowing Aneurolepidium chinense,which can led to a fast restoration of grassland vegetation. The second method is to sow alkaline-saline grasses, which could gradually accumulate the organic matter and led a gradual restoration of the natural vegetation. In comparison with the control, the improved area by adding litter 1.5kg·m-2 had a soil bulk density of 1.10g·cm3 much more lower than that of control (1.7g·cm3). The soil hold degree, water content and air content were also increased by 41.7%, 31.7%and 170.0% respectively. While soil pH value decreased from 10.1 to 8.5,the total salt content and soil conductivity rate drooped by 34.1% and 40.0% respectively; soil alkaline degree decreased from 60.59% to 35.75%. Planting Chloris virgata is one of the most effective ways for improving alkaline-saline grassland. In the fourth year after the improvement ,the alkaline patches were recovered by vegetation and community yield reached 450g·m-2 in which Aneurolopidium chinense yield made up over 45%. Experimental result showed that A. chinense could live on alkaline-saline soil improved by adding litter 1.5g·m-2,the community yield might reach 600g·m-2and A. chinense grassland could be recovered to primary type at the fourth year after the improvement.