| A comparative study was conducted during 2000-2002 with two grazing systems of rotational grazing and free stocking on family ranches in Stipa breviflora desert steppe. Evaluations on the aspects of plant population, community, animal grazing behaviour, production output and economic efficiency were made on the two systems and sustainable management strategies were proposed. The main results were as follows:1. Compared with free stocking, rotational grazing allowed more above-ground biomass accumulations of Cleistogenes songoriea and Allium polyrhizum. Peak productions of Stipa breviflora above-ground biomass under the two grazing system were simila, while the peak time was lagged in free stocking system.Rotational grazing was favorable for tillering, and subsequently, tiller growth in S. breviflora, C. songoriea and A. polyrhizum. hi contrast, free stocking prevented the plants from producing tillers and subsequent tiller growth in C. songoriea and A. polyrhizum. Under free stocking system, the weights of individual tillers of S. breviflora, C. songoriea and A. polyrhizum were significantly lower than those under rotational grazing system and in closed pasture.2. More reproductive tillers of the S. breviflora, and subsequently more seeds per unit area, were formed in rotational grazing area. Grazing had negative influences on plant sexual reproduction. Free stocking had obvious negative influences on seedling survival of A. polyrhizum.Compared with free stocking area, carbohydrate storage were high during growing period, as well as during Autumn and early Spring times, in the rotational grazing area and in the closed area. Subsequently, vigorous early spring growth and growth potential were found in the late two areas.3. In the free stocking area, Convolvulus ammannii, a tough grazing resistant plant indicator, appeared in the third year of the experiment (Year 2002). Plant density, height and coverage of Artemisia frigida were increased. Density of Lagochilius ilicifolius, a high drought resistant plant, was increased, densities and coverages of annual plants were also increased in the free stocking area, which was considered an indication of grassland degeneration and inhabit dehydration.Coverage of S breviflora in the rotational grazing area increased in compared with the free stocking area and the closed area. No significant differences were found with C. songoriea in plant density and coverage in rotational grazing area and in closed area, though the two indexes were all low in the free stocking area.In the third year of the experiment (Year 2002), Shannon-Wiener index, Simpson index, and Pielou index were all found higher in the free stocking area than in the rotational grazing area. However, the distribution of importance values for the influential factors with these indexes was concentrated on several dominant andconstructive species, which indicated that rotational grazed grassland was more stable than the free stocked one.4. No significant yield differences of standing forages were found in the rotational grazing area and in the closed area, which were all superior to the free stocking area. The standing forage productions in the rotational grazing area and in the closed area showed Low-High-Low patterns, while a straight decline pattern was found in the free stocking area.Herbages in the free stocking area had high contents of crude protein, ash, phosphorus, and low content of crude fiber in the early growth stage, and low contents of crude protein, ash, phosphorus, and high content of crude fiber in the late growth stage, in compared with the rotational grazing and closing of grazing.Equal compensation growth was found in the two grazing system, although rotational grazing seemed more favorable for compensation growth potential5. Animal spatial selection behaviours were modified by rotational grazing, which reduced the grazing area, overlaid the grazing stations, and made more evenly uses of grasslands. Animals in the rotational system had a shorter...
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